In this paper we assess the possibility that a rigid cosmological constant, $\Lambda$, and hence the traditional concordance $\Lambda$CDM model, might not be the best phenomenological description of the current cosmological data. We show that a large class of dynamical vacuum models (DVMs), whose vacuum energy density $\rho_{\Lambda}(H)$ consists of a nonvanishing constant term and a series of powers of the Hubble rate, provides a substantially better phenomenological account of the overall $SNIa+BAO+H(z)+LSS+CMB$ cosmological observations. We find that some models within the class of DVMs, particularly the running vacuum model (RVM), appear significantly much more favored than the $\Lambda$CDM, at an unprecedented confidence level of $\sim 4\sigma$. We further support this claim by computing the Akaike and Bayesian information criteria and confirm that the RVM is strongly preferred as compared to the $\Lambda$CDM. In addition, we compare the dynamical vacuum signature encoded in the RVM to the behavior of the generic XCDM and CPL parametrizations of the dark energy, as well as to particular $\Phi$CDM (quintessence) models with specific potentials (e.g. the Peebles & Ratra potential). In all cases the most telltale sign of dynamical vacuum energy in our expanding universe lies in the combined triad of modern $BAO+LSS+CMB$ observations. In the absence of any of these three crucial data sources, the dynamical signature could not be perceived at a significant confidence level. This comprehensive paper is the expanded, and fully updated, backup version of the previously submitted, Letter-type, presentation of our results in arXiv:1606.00450.
We present results from a 100 ks XMM-Newton observation of galaxy cluster XLSSC 122, the first massive cluster discovered through its X-ray emission at $z\approx2$. The data provide the first precise constraints on the bulk thermodynamic properties of such a distant cluster, as well as an X-ray spectroscopic confirmation of its redshift. We measure an average temperature of $kT=5.0\pm0.7$ keV; a metallicity with respect to solar of $Z/Z_{\odot}=0.33^{+0.19}_{-0.17}$, consistent with lower-redshift clusters; and a redshift of $z=1.99^{+0.07}_{-0.06}$, consistent with the earlier photo-z estimate. The measured gas density profile leads to a mass estimate at $r_{500}$ of $M_{500}=(6.3\pm1.5)\times10^{13}M_{\odot}$. From CARMA 30 GHz data, we measure the spherically integrated Compton parameter within $r_{500}$ to be $Y_{500}=(3.6\pm0.4)\times10^{-12}$. We compare the measured properties of XLSSC 122 to lower-redshift cluster samples, and find good agreement when assuming the simplest (self-similar) form for the evolution of cluster scaling relations. While a single cluster provides limited information, this result suggests that the evolution of the intracluster medium in the most massive, well developed clusters is remarkably simple, even out to the highest redshifts where they have been found. At the same time, our data reaffirm the previously reported spatial offset between the centers of the X-ray and SZ signals for XLSSC 122, suggesting a disturbed configuration. Higher spatial resolution data could thus provide greater insights into the internal dynamics of this system.
We examine the validity of the $\Lambda$CDM model, and probe for the dynamics of dark energy using latest astronomical observations. Using the $Om(z)$ diagnosis, we find that different kinds of observational data are in tension within the $\Lambda$CDM framework. We then allow for dynamics of dark energy and investigate the constraint on dark energy parameters. We find that for two different kinds of parametrisations of the equation of state parameter $w$, a combination of current data mildly favours an evolving $w$, although the significance is not sufficient for it to be supported by the Bayesian evidence. A forecast of the DESI survey shows that the dynamics of dark energy could be detected at $7\sigma$ confidence level, and will be decisively supported by the Bayesian evidence, if the best fit model of $w$ derived from current data is the true model.
We apply the nonlinear reconstruction method (Zhu et al., arXiv:1611.09638) to simulated halo fields. For halo number density $2.77\times 10^{-2}$ $(h^{-1} {\rm Mpc})^{-3}$ at $z=0$, corresponding to the SDSS main sample density, we find the scale where the noise saturates the linear signal is improved to $k\gtrsim0.36\ h {\rm Mpc}^{-1}$, a factor of $2.29$ improvement in scale, or $12$ in number of linear modes. The improvement is less for higher redshift or lower halo density. We expect this to substantially improve the BAO accuracy of dense, low redshift surveys, including the SDSS main sample, 6dFGS and 21cm intensity mapping initiatives.
We report on SPT-CLJ2011-5228, a giant system of arcs created by a cluster at $z=1.06$. The arc system is notable for the presence of a bright central image. The source is a Lyman Break galaxy at $z_s=2.39$ and the mass enclosed within the 14 arc second radius Einstein ring is $10^{14.2}$ solar masses. We perform a full light profile reconstruction of the lensed images to precisely infer the parameters of the mass distribution. The brightness of the central image demands that the central total density profile of the lens be shallow. By fitting the dark matter as a generalized Navarro-Frenk-White profile---with a free parameter for the inner density slope---we find that the break radius is $270^{+48}_{-76}$ kpc, and that the inner density falls with radius to the power $-0.38\pm0.04$ at 68 percent confidence. Such a shallow profile is in strong tension with our understanding of relaxed cold dark matter halos; dark matter only simulations predict the inner density should fall as $r^{-1}$. The tension can be alleviated if this cluster is in fact a merger; a two halo model can also reconstruct the data, with both clumps (density going as $r^{-0.8}$ and $r^{-1.0}$) much more consistent with predictions from dark matter only simulations. At the resolution of our Dark Energy Survey imaging, we are unable to choose between these two models, but we make predictions for forthcoming Hubble Space Telescope imaging that will decisively distinguish between them.
We study the morphology, luminosity and mass of the superclusters from the BOSS Great Wall (BGW), a recently discovered very rich supercluster complex at the redshift $z = 0.47$. We have employed the Minkowski functionals to quantify supercluster morphology. We calculate supercluster luminosities and masses using two methods. Firstly, we used data about the luminosities and stellar masses of high stellar mass galaxies with $\log(M_*/h^{-1}M_\odot) \geq 11.3$. Secondly, we applied a scaling relation that combines morphological and physical parameters of superclusters to obtain supercluster luminosities, and obtained supercluster masses using the mass-to-light ratios found for local rich superclusters. We find that the BGW superclusters are very elongated systems, with shape parameter values of less than $0.2$. This value is lower than that found for the most elongated local superclusters. The values of the fourth Minkowski functional $V_3$ for the richer BGW superclusters ($V_3 = 7$ and $10$) show that they have a complicated and rich inner structure. We identify two Planck SZ clusters in the BGW superclusters, one in the richest BGW supercluster, and another in one of the poor BGW superclusters. The luminosities of the BGW superclusters are in the range of $1 - 8\times~10^{13}h^{-2}L_\odot$, and masses in the range of $0.4 - 2.1\times~10^{16}h^{-1}M_\odot$. Supercluster luminosities and masses obtained with two methods agree well. We conclude that the BGW is a complex of massive, luminous and large superclusters with very elongated shape. The search and detailed study, including the morphology analysis of the richest superclusters and their complexes from observations and simulations can help us to understand formation and evolution of the cosmic web.
We search for sterile neutrinos in the holographic dark energy cosmology by using the latest observational data. To perform the analysis, we employ the current cosmological observations, including the cosmic microwave background temperature power spectrum data from Planck mission, the baryon acoustic oscillation measurements, the type Ia supernova data, the redshift space distortion measurements, the shear data of weak lensing observation, the Planck lensing measurement, and the latest direct measurement of $H_0$ as well. We show that, compared to the $\Lambda$CDM cosmology, the holographic dark energy cosmology with sterile neutrinos can relieve the tension between the Planck observation and the direct measurement of $H_0$ much better. Once including the $H_0$ measurement in the global fit, we find that the hint of the existence of sterile neutrinos in the holographic dark energy cosmology can be given. Under the constraint of the all-data combination, we obtain $N_{\rm eff}= 3.76\pm0.26$ and $m_{\nu,\rm sterile}^{\rm eff}< 0.215\,\rm eV$, indicating that the detection of $\Delta N_{\rm eff}>0$ in the holographic dark energy cosmology is at the $2.75\sigma$ level and the massless or very light sterile neutrino is favored by the current observations.
In this paper we study the cosmic acceleration for five dynamical dark energy models whose equation of state varies with redshift. The cosmological parameters of these models are constrained by performing a MCMC analysis using mainly gas mass fraction, $f_{gas}$, measurements in two samples of galaxy clusters: one reported by Allen et al. (2004), which consists of $42$ points spanning the redshift range $0.05<z<1.1$, and the other by Hasselfield et al. (2013) from the Atacama Cosmology Telescope survey, which consists of $91$ data points in the redshift range $0.118 < \mathrm{z} < 1.36$. In addition, we perform a joint analysis with the measurements of the Hubble parameter $H(z)$, baryon acoustic oscillations and the cosmic microwave background radiation from WMAP and Planck measurements to estimate the equation of state parameters. We obtained that both $f_{gas}$ samples provide consistent constraints on the cosmological parameters. We found that the $f_{gas}$ data is consistent at the $2\sigma$ confidence level with a cosmic slowing down of the acceleration at late times for most of the parameterizations. The constraints of the joint analysis using WMAP and Planck measurements show that this trend disappears. We have confirmed that the $f_{gas}$ probe provides competitive constraints on the dark energy parameters when a $w(z)$ is assumed.
In this work, by investigating the low temperature behaviour of a scalar field around a cosmic string, and assuming stable thermodynamic equilibrium, it is shown that the coupling parameter of the field with curvature must be restricted to a certain range of values whose bounds are determined by the deficit angle of the associated conical geometry.
We study general properties of static and spherically symmetric bidiagonal black holes in Hassan-Rosen bimetric theory. In particular, we explore the behaviour of the black hole solutions both at the common Killing horizon and at the large radii. The former study leads to a new classification for black holes within the bidiagonal ansatz. The latter study shows that, among the great variety of the black hole solutions, the only solutions converging to Minkowski, Anti-de Sitter and de Sitter spacetimes at large radii are those of General Relativity, i.e., the Schwarzschild, Schwarzschild-Anti-de Sitter and Schwarzschild-de Sitter solutions.
We propose an innovative method for measuring the neutral hydrogen (HI) content of an optically-selected spectroscopic sample of galaxies through cross-correlation with HI intensity mapping measurements. We show that the HI-galaxy cross-power spectrum contains an additive shot noise term which scales with the average HI brightness temperature of the optically-selected galaxies, allowing constraints to be placed on the average HI mass per galaxy. This approach can estimate the HI content of populations too faint to directly observe through their 21cm emission over a wide range of redshifts. This cross-correlation, as a function of optical luminosity or colour, can be used to derive HI-scaling relations. We demonstrate that this signal will be detectable by cross-correlating upcoming Australian SKA Pathfinder (ASKAP) observations with existing optically-selected samples. We also use semi-analytic simulations to verify that the HI mass can be successfully recovered by our technique in the range M_HI > 10^8 M_solar, in a manner independent of the underlying power spectrum shape. We conclude that this method is a powerful tool to study galaxy evolution, which only requires a single intensity mapping dataset to infer complementary HI gas information from existing optical and infra-red observations.
We propose a simple modification of the no-scale supergravity Wess-Zumino model of Starobinsky-like inflation to include a Polonyi term in the superpotential. The purpose of this term is to provide an explicit mechanism for supersymmetry breaking at the end of inflation. We show how successful inflation can be achieved for a gravitino mass satisfying the strict upper bound $m_{3/2}< 10^3$ TeV, with favoured values $m_{3/2}\lesssim\mathcal{O}(1)$ TeV. The model suggests that SUSY may be discovered in collider physics experiments such as the LHC or the FCC.
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Newtonian N-body simulations have been employed successfully over the past decades for the simulation of the cosmological large-scale structure. Such simulations usually ignore radiation perturbations (photons and massless neutrinos) and the impact of general relativity (GR) beyond the background expansion. This approximation can be relaxed and we discuss three different approaches that are accurate to leading order in GR. For simulations that start at redshift less than about 100 we find that the presence of early radiation typically leads to percent-level effects on the numerical power spectra at large scales. Our numerical results agree across the three methods, and we conclude that all of the three methods are suitable for simulations in a standard cosmology. Two of the methods modify the N-body evolution directly, while the third method can be applied as a post-processing prescription.
The cosmic neutrino background is a key prediction of Big Bang cosmology which has not been observed yet. The movement of the earth through this neutrino bath creates a force on a pendulum, as if it was exposed to a cosmic wind. We revise here estimates for the resulting pendulum acceleration and compare it to the theoretical sensitivity of an experimental setup where the pendulum position is measured using current laser interferometer technology as employed in gravitational wave detectors. We discuss how a significant improvement of this setup can be envisaged in a micro gravity environment. The proposed setup could simultaneously function as a dark matter detector in the sub-MeV range, which currently eludes direct detection constraints.
The latest measurements of CMB electron scattering optical depth reported by Planck significantly reduces the allowed space of HI reionization models, pointing towards a later ending and/or less extended phase transition than previously believed. Reionization impulsively heats the intergalactic medium (IGM) to $\sim10^4$ K, and owing to long cooling and dynamical times in the diffuse gas, comparable to the Hubble time, memory of reionization heating is retained. Therefore, a late ending reionization has significant implications for the structure of the $z\sim5-6$ Lyman-$\alpha$ (ly$\alpha$) forest. Using state-of-the-art hydrodynamical simulations that allow us to vary the timing of reionization and its associated heat injection, we argue that extant thermal signatures from reionization can be detected via the ly$\alpha$ forest power spectrum at $5< z<6$. This arises because the small-scale cutoff in the power depends not only the the IGMs temperature at these epochs, but is also particularly sensitive to the pressure smoothing scale set by the IGMs full thermal history. Comparing our different reionization models with existing measurements of the ly$\alpha$ forest flux power spectrum at $z=5.0-5.4$, we find that models satisfying Planck's $\tau_e$ constraint, favor a moderate amount of heat injection consistent with galaxies driving reionization, but disfavoring quasar driven scenarios. We explore the impact of different reionization histories and heating models on the shape of the power spectrum, and find that they can produce similar effects, but argue that this degeneracy can be broken with high enough quality data. We study the feasibility of measuring the flux power spectrum at $z\simeq 6$ using mock quasar spectra and conclude that a sample of $\sim10$ high-resolution spectra with attainable S/N ratio will allow to discriminate between different reionization scenarios.
We study the intra-cluster magnetic field in the poor galaxy cluster Abell 194 by complementing radio data, at different frequencies, with data in the optical and X-ray bands. We analyze new total intensity and polarization observations of Abell 194 obtained with the Sardinia Radio Telescope (SRT). We use the SRT data in combination with archival Very Large Array observations to derive both the spectral aging and Rotation Measure (RM) images of the radio galaxies 3C40A and 3C40B embedded in Abell 194. The optical analysis indicates that Abell 194 does not show a major and recent cluster merger, but rather agrees with a scenario of accretion of small groups. Under the minimum energy assumption, the lifetimes of synchrotron electrons in 3C40B measured from the spectral break are found to be 157 Myrs. The break frequency image and the electron density profile inferred from the X-ray emission are used in combination with the RM data to constrain the intra-cluster magnetic field power spectrum. By assuming a Kolmogorov power law power spectrum, we find that the RM data in Abell 194 are well described by a magnetic field with a maximum scale of fluctuations of Lambda_max=64 kpc and a central magnetic field strength of <B0>=1.5 microG. Further out, the field decreases with the radius following the gas density to the power of eta=1.1. Comparing Abell 194 with a small sample of galaxy clusters, there is a hint of a trend between central electron densities and magnetic field strengths.
We derive and compare the fractions of cool-core clusters in the Planck Early Sunyaev-Zel'dovich sample of 164 clusters with $z \leq 0.35$ and in a flux-limited X-ray sample of 129 clusters with $z \leq 0.30$, using Chandra observations. We use four metrics to identify cool-core clusters: 1) the concentration parameter: the ratio of the integrated emissivity profile within 0.15 $r_{500}$ to that within $r_{500}$, and 2) the ratio of the integrated emissivity profile within 40 kpc to that within 400 kpc, 3) the cuspiness of the gas density profile: the negative of the logarithmic derivative of the gas density with respect to the radius, measured at 0.04 $r_{500}$, and 4) the central gas density, measured at 0.01 $r_{500}$. We find that the sample of X-ray selected clusters, as characterized by each of these metrics, contains a significantly larger fraction of cool-core clusters compared to the sample of SZ selected clusters (41$\pm$6% vs. 28$\pm$4% using the concentration in the 0.15--1.0 $r_{500}$ range, 60$\pm$7% vs. 36$\pm$5% using the concentration in the 40--400 kpc range, 64$\pm$7% vs. 38$\pm$5% using the cuspiness, and 53$\pm$7% vs. 39$\pm$5% using the central gas density). Qualitatively, cool-core clusters are more X-ray luminous at fixed mass. Hence, our X-ray flux-limited sample, compared to the approximately mass-limited SZ sample, is over-represented with cool-core clusters. We describe a simple quantitative model that uses the excess luminosity of cool-core clusters compared to non-cool-core clusters at fixed mass to successfully predict the observed fraction of cool-core clusters in X-ray selected samples.
We show that axion-like particles constituting 100% of the cold dark matter observed and of mass below a certain value $\bar{m}$ must have originated during the inflationary period only, populating the so-called "anthropic window" of the axion parameter space. The numerical value of $\bar{m}$ ranges between 10neV and 0.5peV, depending on the value of the ALP susceptibility. The bound on the ALP mass comes from the non-observation of primordial gravitational waves, which constrains the energy scale of inflation thus the energy scale of the axion-like particle. We also show that, in the anthropic window, the constraint on the energy scale of inflation is orders of magnitude smaller than what derived from the non-observation of primordial gravitational waves, the exact value depending on the ALP mass.
In the conventional framework for cosmological dynamics the scale factor $a(t)$ is assumed to obey the `background' Friedmann equation for a perfectly homogeneous universe while particles move according to equations of motions driven by the gravity sourced by the density fluctuations. It has been suggested that the emergence of structure modifies the evolution of $a(t)$ via `kinematic' backreaction and that this may avoid the need for dark energy. Here we show that the conventional equations are exact in Newtonian gravity -- which should accurately describe the low-$z$ universe -- and there is no approximation in the use of the homogeneous universe equation for $a(t)$. We conclude that there is no backreaction of structure on $a(t)$ and that the need for dark energy cannot be avoided in this way.
Number counts observations available with new surveys such as the Euclid mission will be an important source of information about the metric of the Universe. We compute the low red-shift expansion for the energy density and the density contrast using an exact spherically symmetric solution in presence of a cosmological constant. At low red-shift the expansion is more precise than linear perturbation theory prediction. We then use the local expansion to reconstruct the monopole component of the metric from the monopole of the density contrast. We test the inversion method using numerical calculations and find a good agreement within the regime of validity of the red-shift expansion. The method could be applied to observational data to reconstruct the metric of the local Universe with a level of precision higher than the one achievable using perturbation theory.
We revisit the physical properties of global and local monopoles and discuss their implications in the dynamics of monopole networks. In particular, we review the Velocity-dependent One-Scale (VOS) model for global and local monopoles and propose physically motivated changes to its equations. We suggest a new form for the acceleration term of the evolution equation of the root-mean-squared velocity and show that, with this change, the VOS model is able to describe the results of radiation and matter era numerical simulations of global monopole networks with a single value of the acceleration parameter $k$, thus resolving the tension previously found in the literature. We also show that the fact that the energy of global monopoles is not localized within their cores affects their dynamics and, thus, the Hubble damping terms in the VOS equations. We study the ultra-relativistic linear scaling regime predicted by the VOS equations and demonstrate that it cannot be attained either on radiation or matter eras and, thus, cannot arise from the cosmological evolution of a global monopole network. We also briefly discuss the implications of our findings for the VOS model for local monopoles.
If a significant fraction of the dark matter in the Universe is made of an ultra-light scalar field, named fuzzy dark matter (FDM) with a mass $m_a$ of the order of $10^{-22}-10^{-21}$ eV, then its de Broglie wavelength is large enough to impact the physics of large scale structure formation. In particular, the associated cutoff in the linear matter power spectrum modifies the structure of the intergalactic medium (IGM) at the scales probed by the Lyman-$\alpha$ forest of distant quasars. We study this effect by making use of dedicated cosmological simulations which take into account the hydrodynamics of the IGM. We explore heuristically the amplitude of quantum pressure for the FDM masses considered here and conclude that quantum effects should not modify significantly the non-linear evolution of matter density at the scales relevant to the measured Lyman-$\alpha$ flux power, and for $m_a \geq 10^{-22}$ eV. We derive a scaling law between $m_a$ and the mass of the well-studied thermal warm dark matter (WDM) model that is best adapted to the Lyman-$\alpha$ forest data, and differs significantly from the one infered by a simple linear extrapolation. By comparing FDM simulations with the Lyman-$\alpha$ flux power spectra determined from the BOSS survey, and marginalizing over relevant nuisance parameters, we exclude FDM masses in the range $10^{-22} \leq m_a < 2.3\times 10^{-21}$ eV at 95 \% CL. Adding higher-resolution Lyman-$\alpha$ spectra extends the exclusion range up to $2.9\times 10^{-21}$ eV. This provides a significant constraint on FDM models tailored to solve the "small-scale problems" of $\Lambda$CDM.
We introduce a rigorous definition of general power-spectrum responses as resummed vertices with two hard and $n$ soft momenta in cosmological perturbation theory. These responses measure the impact of long-wavelength perturbations on the local small-scale power spectrum. The kinematic structure of the responses (i.e., their angular dependence) can be decomposed unambiguously through a "bias" expansion of the local power spectrum, with a fixed number of physical response coefficients, which are only a function of the hard wavenumber $k$. Further, the responses up to $n$-th order completely describe the $(n+2)$-point function in the squeezed limit, i.e. with two hard and $n$ soft modes, which one can use to derive the response coefficients. This generalizes previous results, which relate the angle-averaged squeezed limit to isotropic response coefficients. We derive the complete expression of first- and second-order responses at leading order in perturbation theory, and present extrapolations to nonlinear scales based on simulation measurements of the isotropic response coefficients. As an application, we use these results to predict the non-Gaussian part of the angle-averaged matter power spectrum covariance ${\rm Cov}^{\rm NG}_{\ell = 0}(k_1,k_2)$, in the limit where one of the modes, say $k_2$, is much smaller than the other. Without any free parameters, our model results are in very good agreement with simulations for $k_2 \lesssim 0.06\ h/{\rm Mpc}$, and for any $k_1 \gtrsim 2 k_2$. The well-defined kinematic structure of the power spectrum response also permits a quick evaluation of the angular dependence of the covariance matrix. While we focus on the matter density field, the formalism presented here can be generalized to generic tracers such as galaxies.
Galaxy clusters are known to induce gas loss in infalling galaxies due to the ram pressure exerted by the intracluster medium over their gas content. In this paper, we investigate this process through a set of simulations of Milky Way like galaxies falling inside idealised clusters of 10$^{14}$ M$_\odot$ and 10$^{15}$ M$_\odot$, containing a cool-core or not, using the adaptive mesh refinement code RAMSES. We use these simulations to constrain how much of the initial mass contained in the gaseous disk of the galaxy will be converted into stars and how much of it will be lost, after a single crossing of the entire cluster. We find that, if the galaxy reaches the central region of a cool-core cluster, it is expected to lose all its gas, independently of its entry conditions and of the cluster's mass. On the other hand, it is expected to never lose all its gas after crossing a cluster without a cool-core just once. Before reaching the centre of the cluster, the SFR of the galaxy is always enhanced, by a factor of 1.5 to 3. If the galaxy crosses the cluster without being completely stripped, its final amount of gas is on average two times smaller after crossing the 10$^{15}$ M$_\odot$ cluster, relative to the 10$^{14}$ M$_\odot$ cluster. This is reflected in the final SFR of the galaxy, which is also two times smaller in the former, ranging from 0.5 $-$ 1 M$_\odot$ yr$^{-1}$, compared to 1 $-$ 2 M$_\odot$ yr$^{-1}$ for the latter.
We analyze the environmental properties of 370 present-day early-type galaxies in the MASSIVE and ATLAS3D surveys, two complementary volume-limited integral-field spectroscopic (IFS) galaxy surveys spanning absolute $K$-band magnitude $-21.5 > M_K > -26.6$, or stellar mass $6\ times 10^{9} < M_* < 2 \times 10^{12} M_\odot$. We find these galaxies to reside in a diverse range of environments measured by four methods: group membership (whether a galaxy is a brightest group/cluster galaxy, satellite, or isolated), halo mass, large-scale mass density (measured over a few Mpc), and local mass density (measured within the $N$th neighbor). The spatially resolved IFS stellar kinematics provide robust measurements of the angular momentum parameter $\lambda_e$ and enable us to examine the relationship among $\lambda_e$, stellar mass, and environment of ETGs. We find a strong correlation between $\lambda_e$ and stellar mass, where the average $\lambda_e$ decreases from $\sim 0.5$ to less than 0.1 with increasing galaxy mass, and the fraction of slow rotators increases correspondingly from $\sim 10$% to 90%. While we see weak trends between environment and both $\lambda_e$ and slow rotator fraction, this kinematic morphology-density relation is fully accounted for by the strong correlation between the slow rotator fraction and stellar mass; due to the correlation between stellar mass and environment, it naturally results in a correlation between slow/fast classification and environment as well. A possible exception is that the increased fraction of slow rotators at high local density is slightly more than expected based only on these joint correlations. Our results suggest that the physical processes responsible for building up the present-day stellar masses of massive galaxies are also very efficient at reducing their angular momentum, in any environment.
Recent observations have revealed massive galactic molecular outflows that may have physical conditions (high gas densities) required to form stars. Indeed, several recent models predict that such massive galactic outflows may ignite star formation within the outflow itself. This star-formation mode, in which stars form with high radial velocities, could contribute to the morphological evolution of galaxies, to the evolution in size and velocity dispersion of the spheroidal component of galaxies, and would contribute to the population of high-velocity stars, which could even escape the galaxy. Such star formation could provide in-situ chemical enrichment of the circumgalactic and intergalactic medium (through supernova explosions of young stars on large orbits), and some models also predict that it may contribute substantially to the global star formation rate observed in distant galaxies. Although there exists observational evidence for star formation triggered by outflows or jets into their host galaxy, as a consequence of gas compression, evidence for star formation occurring within galactic outflows is still missing. Here we report new spectroscopic observations that unambiguously reveal star formation occurring in a galactic outflow at a redshift of 0.0448. The inferred star formation rate in the outflow is larger than 15 Msun/yr. Star formation may also be occurring in other galactic outflows, but may have been missed by previous observations owing to the lack of adequate diagnostics.
Follow-up observations at high-angular resolution of submillimeter galaxies showed that the single-dish sources are comprised of a blend of several galaxies. Consequently, number counts derived from low and high angular resolution observations are in disagreement. This demonstrates the importance of resolution effects and the need to have realistic simulations to explore them. We built a new 2deg^2 simulation of the extragalactic sky from the far-infrared to the submillimeter. It is based on an updated version of the two star-formation mode galaxy evolution model. Using global galaxy properties, we use the abundance matching technique to populate a dark-matter lightcone and thus simulate the clustering. We produce maps and extract the sources, and show that the limited angular resolution of single-dish instruments have a strong impact on (sub)millimeter continuum observations. Taking into account these resolution effects, we are reproducing a large set of observables, including number counts, redshift distributions, and cosmic infrared background power spectra. Our simulation describes consistently the number counts from single-dish telescopes and interferometers. In particular, at 350 and 500 um, we find that number counts measured by Herschel between 5 and 50 mJy are biased towards high values by a factor 2, and that redshift distributions are biased towards low z. We also show that the clustering has an important impact on the Herschel pixel histogram used to derive number counts from P(D) analysis. Finally, we demonstrate that the large number density of red Herschel sources found in observations but not in models could be an observational artifact caused by the combination of noise, resolution effects, and the steepness of color and flux density distributions. Our simulation (SIDES) is available at this http URL
Experiments using nuclei to probe new physics beyond the Standard Model, such as neutrinoless $\beta\beta$ decay searches testing whether neutrinos are their own antiparticle, and direct detection experiments aiming to identify the nature of dark matter, require accurate nuclear physics input for optimizing their discovery potential and for a correct interpretation of their results. This demands a detailed knowledge of the nuclear structure relevant for these processes. For instance, neutrinoless $\beta\beta$ decay nuclear matrix elements are very sensitive to the nuclear correlations in the initial and final nuclei, and the spin-dependent nuclear structure factors of dark matter scattering depend on the subtle distribution of the nuclear spin among all nucleons. In addition, nucleons are composite and strongly interacting, which implies that many-nucleon processes are necessary for a correct description of nuclei and their interactions. It is thus crucial that theoretical studies and experimental analyses consider $\beta$ decays and dark matter interactions with a coupling to two nucleons, called two-nucleon currents.
Gamma-ray bursts (GRBs) are powerful probes of early stars and galaxies, during and potentially even before the era of reionization. Although the number of GRBs identified at z>6 remains small, they provide a unique window on typical star-forming galaxies at that time, and thus are complementary to deep field observations. We report the identification of the optical drop-out afterglow of Swift GRB 120923A in near-infrared Gemini-North imaging, and derive a redshift of z=7.84_{-0.12}^{+0.06} from VLT/X-shooter spectroscopy. At this redshift the peak 15-150 keV luminosity of the burst was 3.2x10^52 erg/s, and in fact the burst was close to the Swift/BAT detection threshold. The X-ray and near-infrared afterglow were also faint, and in this sense it was a rather typical long-duration GRB in terms of rest-frame luminosity. We present ground- and space-based follow-up observations spanning from X-ray to radio, and find that a standard external shock model with a constant-density circumburst environment with density, n~4x10^-2 cm^-3 gives a good fit to the data. The near-infrared light curve exhibits a sharp break at t~3.4 days in the observer frame, which if interpreted as being due to a jet corresponds to an opening angle of ~5 degrees. The beaming corrected gamma-ray energy is then E_gamma~2x10^50 erg, while the beaming-corrected kinetic energy is lower, E_K~10^49 erg, suggesting that GRB 120923A was a comparatively low kinetic energy event. We discuss the implications of this event for our understanding of the high-redshift population of GRBs and their identification.
We present a method to calculate, without making assumptions about the local dark matter velocity distribution, the maximal and minimal number of signal events in a direct detection experiment given a set of constraints from other direct detection experiments and/or neutrino telescopes. The method also allows to determine the velocity distribution that optimizes the signal rates. We illustrate our method with three concrete applications: i) to derive a halo-independent upper limit on the cross section from a set of null results, ii) to confront in a halo-independent way a detection claim to a set of null results and iii) to assess, in a halo-independent manner, the prospects for detection in a future experiment given a set of current null results.
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What are the fundamental limitations of reconstructing the properties of dark energy, given cosmological observations in the weakly nonlinear regime in a range of redshifts, to be as precise as required? The aim of this paper is to address this question by constructing model-independent observables, whilst completely ignoring practical problems of real-world observations. Non-Gaussianities already present in the initial conditions are not directly accessible from observations, because of a perfect degeneracy with the non-Gaussianities arising from the nonlinear matter evolution in generalized dark energy models. By imposing a specific set of evolution equations that should cover a range of dark energy cosmologies, we however find a constraint equation for the linear structure growth rate $f_1$ expressed in terms of model-independent observables. Entire classes of dark energy models which do not satisfy this constraint equation could be ruled out, and for models satisfying it we could reconstruct e.g. the nonlocal bias parameters $b_1$ and $b_2$.
Convergence maps of the integrated matter distribution are a key science result from weak gravitational lensing surveys. To date, recovering convergence maps has been performed using a planar approximation of the celestial sphere. However, with the increasing area of sky covered by dark energy experiments, such as Euclid, the Large Synoptic Survey Telescope (LSST), and the Wide Field Infrared Survey Telescope (WFIRST), this assumption will no longer be valid. We extend the Kaiser-Squires technique for recovering convergence fields, restricted previously to the plane, to the spherical setting. Through simulations we study the error introduced by planar approximations. Moreover, we examine how best to recover convergence maps in the planar setting, considering a variety of different projections and defining the local rotations that are required when projecting spin fields such as cosmic shear. For the sky coverages typical of future surveys, errors introduced by projection effects can be of order tens of percent, exceeding 50% in some cases. The stereographic projection, which is conformal and so preserves local angles, is the most effective planar projection. In any case, these errors can be avoided entirely by recovering convergence fields directly on the celestial sphere. We apply the spherical Kaiser-Squires mass-mapping method presented to the public Dark Energy Survey (DES) science verification data to recover convergence maps directly on the celestial sphere.
Cosmic rays (CRs) govern the energetics of present-day galaxies and might have also played a pivotal role during the Epoch of Reionization. In particular, energy deposition by low-energy ($E \lesssim 10$ MeV) CRs accelerated by the first supernovae, might have heated and ionized the neutral intergalactic medium (IGM) well before ($z \approx 20$) it was reionized, significantly adding to the similar effect by X-rays or dark matter annihilations. Using a simple, but physically motivated reionization model, and a thorough implementation of CR energy losses, we show that CRs contribute negligibly to IGM ionization, but heat it substantially, raising its temperature by $\Delta T=10-200$ K by $z=10$, depending on the CR injection spectrum. Whether this IGM pre-heating is uniform or clustered around the first galaxies depends on CR diffusion, in turn governed by the efficiency of self-confinement due to plasma streaming instabilities that we discuss in detail. This aspect is crucial to interpret future HI 21 cm observations which can be used to gain unique information on the strength and structure of early intergalactic magnetic fields, and the efficiency of CR acceleration by the first supernovae.
Previous studies have found our velocity in the rest frame of radio galaxies at high redshift to be substantially larger than that inferred from the CMB temperature dipole anisotropy. We construct a full sky catalogue NVSUMSS, by merging the NVSS and SUMSS catalogues and removing local sources by various means including cross-correlating with the 2MRS catalogue. We take into account both aberration and Doppler boost to deduce our velocity from the hemispherical number count asymmetry, as well as via a 3-dimensional linear estimator. Both the magnitude and direction depend on cuts made to the catalogue, e.g. on the lowest source flux, however these effects are small. With the hemispheric number count asymmetry method we obtain a velocity of 1729 $\pm$ 187 km/s i.e. about 4 times larger than that obtained from the CMB dipole, but close in direction, towards RA=149 $\pm$ 2 degree, DEC = -17 $\pm$ 12 degree. With the 3-dimensional estimator, the derived velocity is 1355 $\pm$ 174 km/s towards RA=141 $\pm$ 11 degree, DEC=-9 $\pm$ 10 degree. We assess the statistical significance of these results by constructing catalogues of random distributions and show that they are at best significant at the $2.81 \sigma$ (99.95% confidence) level.
In a model of the late-time cosmic acceleration within the framework of generalized Proca theories, there exists a de Sitter attractor preceded by the dark energy equation of state $w_{\rm DE}=-1-s$, where $s$ is a positive constant. We run the Markov-Chain-Monte-Carlo code to confront the model with the observational data of Cosmic Microwave Background (CMB), baryon acoustic oscillations, supernovae type Ia, and local measurements of the Hubble expansion rate for the background cosmological solutions and obtain the bound $s=0.254^{{}+ 0.118}_{{}-0.097}$ at 95% confidence level (CL). Existence of the additional parameter $s$ to those in the $\Lambda$-Cold-Dark-Matter ($\Lambda$CDM) model allows to reduce tensions of the Hubble constant $H_0$ between the CMB and the low-redshift measurements. Including the cosmic growth data of redshift-space distortions in the galaxy power spectrum and taking into account no-ghost and stability conditions of cosmological perturbations, we find that the bound on $s$ is shifted to $s=0.16^{+0.08}_{-0.08}$ (95 % CL) and hence the model with $s>0$ is still favored over the $\Lambda$CDM model. Apart from the quantities $s, H_0$ and the today's matter density parameter $\Omega_{m0}$, the constraints on other model parameters associated with perturbations are less stringent, reflecting the fact that there are different sets of parameters that give rise to similar cosmic expansion and growth history.
General relativistic imprints on the galaxy bispectrum arise from both dynamical and observational (or projection) effects. The lightcone projection effects include local contributions from Doppler and gravitational potential terms, as well as lensing and other integrated contributions. We recently presented for the first time, the correction to the galaxy bispectrum from all local lightcone projection effects up to second order in perturbations. Here we provide the details underlying this correction, together with further results and illustrations. For moderately squeezed shapes, the correction to the Newtonian prediction is ~10% on equality scales. We generalise our recent results to include the contribution, up to second order, of magnification bias (which affects some of the local terms) and evolution bias.
The remarkable properties of the geodesic light-cone (GLC) coordinates allow analytic expressions for the light-cone observables, providing a new non-perturbative way for calculating the effects of inhomogeneities in our Universe. However, the gauge-invariance of these expressions in the GLC formalism has not been shown explicitly. Here we provide this missing part of the GLC formalism by proving the gauge-invariance of the GLC expressions for the light-cone observables, such as the observed redshift, the luminosity distance, and the physical area and volume of the observed sources. Our study provides a new insight on the properties of the GLC coordinates and it complements the previous work by the GLC collaboration, leading to a comprehensive description of light propagation in the GLC representation.
We present a halo-independent determination of the unmodulated signal corresponding to the DAMA modulation if interpreted as due to dark matter weakly interacting massive particles (WIMPs). First we show how a modulated signal gives information on the WIMP velocity distribution function in the Galactic rest frame, from which the unmodulated signal descends. Then we perform a mathematically-sound profile likelihood analysis in which we profile the likelihood over a continuum of nuisance parameters (namely, the WIMP velocity distribution). As a first application of the method, which is very general and valid for any class of velocity distributions, we restrict the analysis to velocity distributions that are isotropic in the Galactic frame. In this way we obtain halo-independent maximum-likelihood estimates and confidence intervals for the DAMA unmodulated signal. We find that the estimated unmodulated signal is in line with expectations for a WIMP-induced modulation and is compatible with the DAMA background rate. Specifically, for the isotropic case we find that the modulated amplitude ranges between a few percent and about 25% of the unmodulated amplitude, depending on the WIMP mass.
Recent studies suggest that the quenching properties of galaxies are correlated over several mega-parsecs. The large-scale "galactic conformity" phenomenon around central galaxies has been regarded as a potential signature of "galaxy assembly bias" or "pre-heating", both of which interpret conformity as a result of direct environmental effects acting on galaxy formation. Building on the iHOD halo quenching framework developed in Zu & Mandelbaum (2015, 2016), we discover that our fiducial halo mass quenching model, without any galaxy assembly bias, can successfully explain the overall environmental dependence and the conformity of galaxy colours in SDSS, as measured by the mark correlation functions of galaxy colours and the red galaxy fractions around isolated primaries, respectively. Our fiducial iHOD halo quenching mock also correctly predicts the differences in the spatial clustering and galaxy-galaxy lensing signals between the more vs. less red galaxy subsamples, split by the red-sequence ridge-line at fixed stellar mass. Meanwhile, models that tie galaxy colours fully or partially to halo assembly bias have difficulties in matching all these observables simultaneously. Therefore, we demonstrate that the observed environmental dependence of galaxy colours can be naturally explained by the combination of 1) halo quenching and 2) the variation of halo mass function with environment --- an indirect environmental effect mediated by two separate physical processes.
Stars form in cold molecular clouds. However, molecular gas is difficult to observe because the most abundant molecule (H2) lacks a permanent dipole moment. Rotational transitions of CO are often used as a tracer of H2, but CO is much less abundant and the conversion from CO intensity to H2 mass is often highly uncertain. Here we present a new method for estimating the column density of cold molecular gas (Sigma_gas) using optical spectroscopy. We utilise the spatially resolved H-alpha maps of flux and velocity dispersion from the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) Galaxy Survey. We derive maps of Sigma_gas by inverting the multi-freefall star formation relation, which connects the star formation rate surface density (Sigma_SFR) with Sigma_gas and the turbulent Mach number (Mach). Based on the measured range of Sigma_SFR = 0.005-1.5 M_sol/yr/kpc^2 and Mach = 18-130, we predict Sigma_gas = 7-200 M_sol/pc^2 in the star-forming regions of our sample of 260 SAMI galaxies. These values are close to previously measured Sigma_gas obtained directly with unresolved CO observations of similar galaxies at low redshift. We classify each galaxy in our sample as 'Star-forming' (219) or 'Composite/AGN/Shock' (41), and find that in Composite/AGN/Shock galaxies the average Sigma_SFR, Mach, and Sigma_gas are enhanced by factors of 2.0, 1.6, and 1.3, respectively, compared to Star-forming galaxies. We compare our predictions of Sigma_gas with those obtained by inverting the Kennicutt-Schmidt relation and find that our new method is a factor of two more accurate in predicting Sigma_gas, with an average deviation of 32% from the actual Sigma_gas.
We use $>$9400 $\log(m/M_{\odot})>10$ quiescent and star-forming galaxies at $z\lesssim2$ in COSMOS/UltraVISTA to study the average size evolution of these systems, with focus on the rare, ultra-massive population at $\log(m/M_{\odot})>11.4$. The large 2-square degree survey area delivers a sample of $\sim400$ such ultra-massive systems. Accurate sizes are derived using a calibration based on high-resolution images from the Hubble Space Telescope. We find that, at these very high masses, the size evolution of star-forming and quiescent galaxies is almost indistinguishable in terms of normalization and power-law slope. We use this result to investigate possible pathways of quenching massive $m>M^*$ galaxies at $z<2$. We consistently model the size evolution of quiescent galaxies from the star-forming population by assuming different simple models for the suppression of star-formation. These models include an instantaneous and delayed quenching without altering the structure of galaxies and a central starburst followed by compaction. We find that instantaneous quenching reproduces well the observed mass-size relation of massive galaxies at $z>1$. Our starburst$+$compaction model followed by individual growth of the galaxies by minor mergers is preferred over other models without structural change for $\log(m/M_{\odot})>11.0$ galaxies at $z>0.5$. None of our models is able to meet the observations at $m>M^*$ and $z<1$ with out significant contribution of post-quenching growth of individual galaxies via mergers. We conclude that quenching is a fast process in galaxies with $ m \ge 10^{11} M_\odot$, and that major mergers likely play a major role in the final steps of their evolution.
In a wide class of cosmological models, a positive cosmological constant drives cosmological evolution toward an asymptotically de Sitter phase. Here we connect this behavior to the increase of entropy over time, based on the idea that de Sitter space is a maximum-entropy state. We prove a cosmic no-hair theorem for Robertson-Walker and Bianchi I spacetimes by assuming that the generalized entropy of a Q-screen ("quantum" holographic screen), in the sense of the cosmological version of the Generalized Second Law conjectured by Bousso and Engelhardt, increases up to a finite maximum value, which we show coincides with the de Sitter horizon entropy. We do not use the Einstein field equations in our proof, nor do we assume the existence of a positive cosmological constant. As such, asymptotic relaxation to a de Sitter phase can, in a precise sense, be thought of as cosmological equilibration.
By far cosmology is one of the most exciting subject to study, even more so with the current bulk of observations we have at hand. These observations might indicate different kinds of doomsdays, if dark energy follows certain patterns. Two of these doomsdays are the Little Rip (LR) and Little Sibling of the Big Rip (LSBR). In this work, aside from proving the unavoidability of the LR and LSBR in the Eddington-inspired-Born-Infeld (EiBI) scenario, we carry out a quantum analysis of the EiBI theory with a matter field, which, from a classical point of view would inevitably lead to a universe that ends with either LR or LSBR. Based on a modified Wheeler-DeWitt equation, we demonstrate that such fatal endings seems to be avoidable.
We discuss a dark family of lepton-like particles with their own "private" gauge bosons under a local SU'(2)xU'(1) symmetry. The Higgs doublet would couple in the standard way to the left-handed SU'(2) doublet and right-handed singlets but not to the extra gauge bosons. This reduces the electroweak-type gauge symmetries from SU'(2)xU'(1)xSU_w(2)xU_Y(1) to the diagonal (vector-like) SU(2)xU(1). The "dark leptons" would contribute to the dark matter and interact with Standard Model matter through the Higgs portal. The dark gauge bosons remain massless with their energy densities decreasing with the fourth power of the scale factor. This defines a dark matter model with internal interactions. The Standard Model Higgs boson aligns the two electroweak-type symmetry groups in the visible and dark sectors and generates the masses in both sectors. We also identify charge assignments for SU'(2)xU'(1) in the dark sector which allow for the formation of dark atoms as bound states of dark lepton-like particles. The simplest single-component dark matter version of the model predicts a dark matter mass around 96 GeV, but the corresponding nucleon recoil cross section is ruled out by the xenon based experiments. However, multi-component models or models with a dark SU(2) doublet mediator instead of the Higgs portal would still be viable.
We study how the gas in a sample of galaxies (M* > 10e9 Msun) in clusters, obtained in a cosmological simulation, is affected by the interaction with the intra-cluster medium (ICM). The dynamical state of each elemental parcel of gas is studied using the total energy. At z ~ 2, the galaxies in the simulation are evenly distributed within clusters, moving later on towards more central locations. In this process, gas from the ICM is accreted and mixed with the gas in the galactic halo. Simultaneously, the interaction with the environment removes part of the gas. A characteristic stellar mass around M* ~ 10e10 Msun appears as a threshold marking two differentiated behaviours. Below this mass, galaxies are located at the external part of clusters and have eccentric orbits. The effect of the interaction with the environment is marginal. Above, galaxies are mainly located at the inner part of clusters with mostly radial orbits with low velocities. In these massive systems, part of the gas, strongly correlated with the stellar mass of the galaxy, is removed. The amount of removed gas is sub-dominant compared with the quantity of retained gas which is continuously influenced by the hot gas coming from the ICM. The analysis of individual galaxies reveals the existence of a complex pattern of flows, turbulence and a constant fuelling of gas to the hot corona from the ICM that could make the global effect of the interaction of galaxies with their environment to be substantially less dramatic than previously expected.
Caustics form in Lagrangian fluids when fluid elements cross and multi-stream regions form. For low-dimensional Lagrangian fluids, the caustics have been classified by catastrophe theory. In the case of potential flow, for one- and two-dimensional fluids, Aronl'd et al. (1982) related this classification to conditions on the displacement field of the fluid. These conditions are called the caustic conditions. This paper concerns nothing less than an entirely new proof for the classification of Lagrangian catastrophes. We provide an alternative, more direct and transparent, path towards the classification of singularities as proposed by Arnol'd. In this study we give a novel derivation of the caustic conditions for the explicit situation of three-dimensional fluids, following up on those for one- and two-dimensional fluids. Moreover, our derivation scheme allows us to extend these to general Lagrangian fluids in spaces of arbitrary dimensions. Applications to cosmic structure formation and to turbulence are indicated, and shortly discussed. In an accompanying publication we apply this towards a full three-dimensional study of caustics in the context of the formation of the cosmic web.
A Type IIn supernova (SN) is dominated by the interaction of SN ejecta with the circumstellar medium (CSM). Some SNe IIn (e.g., SN 2006jd) have episodes of re-brightening ("bumps") in their light curves. We present iPTF13z, a SN IIn discovered by the intermediate Palomar Transient Factory (iPTF) and characterised by several bumps in its light curve. We analyse this peculiar behaviour trying to infer the properties of the CSM and of the SN explosion, as well as the nature of its progenitor star. We obtained multi-band optical photometry for over 1000 days after discovery with the P48 and P60 telescopes at Palomar Observatory. We obtained low-resolution optical spectra in the same period. We did an archival search for progenitor outbursts. We analyse our photometry and spectra, and compare iPTF13z to other SNe IIn. A simple analytical model is used to estimate properties of the CSM. iPTF13z was a SN IIn showing a light curve with five bumps during its decline phase. The bumps had amplitudes between 0.4 and 0.9 mag and durations between 20 and 120 days. The most prominent bumps appeared in all our different optical bands. The spectra showed typical SN IIn characteristics, with emission lines of H$\alpha$ (with broad component FWHM ~$10^{3}-10^{4} ~{\rm ~km ~s^{-1}}$ and narrow component FWHM ~$10^2 \rm ~km ~s^{-1}$) and He I, but also with Fe II, Ca II, Na I D and H$\beta$ P-Cygni profiles (with velocities of ~$10^{3}$ ${\rm ~km ~s^{-1}}$). A pre-explosion outburst was identified lasting $\gtrsim 50$ days, with $M_r \approx -15$ mag around 210 days before discovery. Large, variable progenitor mass-loss rates (~> 0.01 $M_{\odot} \rm ~yr^{-1}$) and CSM densities (~> 10$^{-16}$ g cm$^{-3}$) are derived. We suggest that the light curve bumps of iPTF13z arose from SN ejecta interacting with denser regions in the CSM, possibly produced by the eruptions of a luminous blue variable star.
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Motivated by the recent proposal of the splashback radius as a physical boundary of dark matter halos, we present a parallel computer code for Subhalo and PARticle Trajectory Analysis (SPARTA). The code analyzes the orbits of all simulation particles in all host halos, billions of orbits in the case of typical cosmological N-body simulations. Within this general framework, we develop an algorithm that accurately extracts the location of the first apocenter of particles after infall into a halo, or splashback. We define the splashback radius of a halo as the smoothed average of the apocenter radii of individual particles. This definition allows us to reliably measure the splashback radii of 95% of host halos above a resolution limit of 1000 particles. We show that, on average, the splashback radius and mass are converged to better than 5% accuracy with respect to mass resolution, snapshot spacing, and all free parameters of the method.
The splashback radius $R_{\rm sp}$, the apocentric radius of particles on their first orbit after falling into a dark matter halo, has recently been suggested as a physically motivated halo boundary that separates accreting from orbiting material. Using the SPARTA code presented in Paper I, we analyze the orbits of billions of particles in cosmological simulations of structure formation and measure $R_{\rm sp}$ for a large sample of halos which spans a mass range from dwarf galaxy to massive cluster halos, reaches redshift 8, and includes WMAP, Planck, and self-similar cosmologies. We analyze the dependence of $R_{\rm sp}/R_{\rm 200m}$ and $M_{\rm sp}/M_{\rm 200m}$ on the mass accretion rate $\Gamma$, halo mass, redshift, and cosmology. The scatter in these relations varies between 0.02 and 0.1 dex. While we confirm the known trend that $R_{\rm sp}/R_{\rm 200m}$ decreases with $\Gamma$, the relationships turn out to be more complex than previously thought, demonstrating that $R_{\rm sp}$ is an independent definition of the halo boundary that cannot trivially be reconstructed from spherical overdensity definitions. We present fitting functions for $R_{\rm sp}/R_{\rm 200m}$ and $M_{\rm sp}/M_{\rm 200m}$ as a function of accretion rate, peak height, and redshift, achieving an accuracy of 5% or better everywhere in the parameter space explored. We discuss the physical meaning of the distribution of particle apocenters and show that the previously proposed definition of $R_{\rm sp}$ as the radius of steepest logarithmic density slope encloses roughly three quarters of the apocenters. Finally, we conclude that no analytical model presented thus far can fully explain our results.
In this paper, we report a significant recovery of the linear baryonic acoustic oscillation (BAO) signature by applying the isobaric reconstruction algorithm to the non-linearly evolved matter density field. Assuming that only the longitudinal component of the displacement is cosmologically relevant, this algorithm iteratively solves the non-linear coordinate transform between the Lagrangian and Eulerian frames without requiring any specific knowledge of the dynamics. For dark matter field, it produces the non-linear displacement potential with very high fidelity. The reconstruction error at the pixel level is within a few percent caused only by the emergence of the transverse component after the shell-crossing. As this method circumvents one of the most strongest non-linearity in density field, the reconstructed field is well-described by linear theory and is immune from the bulk-flow smearing of the BAO signature, and therefore could be used to significantly improve the precision of measuring the sound horizon scale. For a perfect large-scale structure survey at redshift zero without Poisson or instrumental noise, the fractional error is reduced by a factor of 2.7, and is very close to the ideal limit one would ever achieve with linear power spectrum and Gaussian covariance matrix.
Recent observations show that the electromagnetic fine-structure constant, $\alpha_e$, may vary with space and time. In the framework of Finsler spacetime, we propose here an anisotropic cosmological model, in which both the spatial and temporal variations of $\alpha_e$ are allowed. Our model naturally leads to the dipole structure of $\alpha_e$, and predicts that the dipole amplitude increases with time. We fit our model to the most up-to-date measurements of $\alpha_e$ from the quasar absorption lines. It is found that the dipole direction points towards $(l,b)=(330.2^\circ\pm7.3^\circ,-13.0^\circ\pm5.6^\circ)$ in the galactic coordinates, and the anisotropic parameter is $b_0=(0.47\pm 0.09) \times10^{-5}$, which corresponds to a dipole amplitude $(7.2\pm 1.4)\times 10^{-8}$ at redshift $z=0.015$. This is well consistent with the upper limit of the variation of $\alpha_e$ measured in the Milky Way. We also fit our model to the Union2.1 type Ia supernovae, and find that the preferred direction of Union2.1 is well consistent with the dipole direction of $\alpha_e$.
The differential event rate in Weakly Interacting Massive Particle (WIMP) direct detection experiments depends on the local dark matter density and velocity distribution. Accurate modelling of the local dark matter distribution is therefore required to obtain reliable constraints on the WIMP particle physics properties. Data analyses typically use a simple Standard Halo Model which might not be a good approximation to the real Milky Way (MW) halo. We review observational determinations of the local dark matter density, circular speed and escape speed and also studies of the local dark matter distribution in simulated MW-like galaxies. We discuss the effects of the uncertainties in these quantities on the energy spectrum and its time and direction dependence. Finally we conclude with an overview of various methods for handling these astrophysical uncertainties.
Star-forming galaxies at high redshifts are the ideal targets to probe the hypothetical variation of the fine-structure constant alpha over cosmological time scales. We propose a modification of the alkali doublets method which allows us to search for variation in alpha combining far infrared and submillimeter spectroscopic observations. This variation manifests as velocity offsets between the observed positions of the fine-structure and gross-structure transitions when compared to laboratory wavelengths. Here we describe our method whose sensitivity limit to the fractional changes in alpha is about 5*10^-7. We also demonstrate that current spectral observations of hydrogen and [C II] 158 micron lines provide an upper limit on |Delta alpha/alpha| < 6*10^-5 at redshifts z = 3.1 and z = 4.7.
The direct detection of gravitational waves opens new perspectives for measuring properties of gravitationally bound compact objects. It is then important to investigate black holes and neutron stars in alternative theories of gravity, since they can have features that make them observationally distinguishable from their General Relativity (GR) counterparts. In this work, we examine a special case of vector Galileons, a vector-tensor theory of gravity with interesting cosmological properties, which consists of a one parameter modification of the Einstein-Maxwell action. Within this theory, we study configurations describing asymptotically flat, spherically symmetric black holes and neutron stars. The set of black hole solutions in this theory is surprisingly rich, generalising results found in GR or in related scalar-tensor theories. We investigate the properties and conserved charges of black holes, using both analytical and numerical techniques, highlighting configurations that are more compact than in GR. We then study properties of neutron stars, showing how the vector profile can influence the star internal structure. Depending on properties of matter and fields inside the star, neutron stars can be more massive than in GR, and they can be even more compact than Schwarzschild black holes, making these objects observationally interesting. We also comment on possible extensions of our configurations to magnetically charged or rotating configurations.
In 1979 Penrose hypothesized that the arrows of time are explained by the hypothesis that the fundamental laws are time irreversible. That is, our reversible laws, such as the standard model and general relativity are effective, and emerge from an underlying fundamental theory which is time irreversible. In Cort\^{e}s and Smolin (2014a, 2014b, 2016) we put forward a research program aiming at realizing just this. The aim is to find a fundamental description of physics above the planck scale, based on irreversible laws, from which will emerge the apparently reversible dynamics we observe on intermediate scales. Here we continue that program and note that a class of discrete dynamical systems are known to exhibit this very property: they have an underlying discrete irreversible evolution, but in the long term exhibit the properties of a time reversible system, in the form of limit cycles. We connect this to our original model proposal in Cort\^{e}s and Smolin (2014a), and show that the behaviours obtained there can be explained in terms of the same phenomenon: the attraction of the system to a basin of limit cycles, where the dynamics appears to be time reversible. Further than that, we show that our original models exhibit the very same feature: the emergence of quasi-particle excitations obtained in the earlier work in the space-time description is an expression of the system's convergence to limit cycles when seen in the causal set description.
We construct a model in which the cosmological constant is canceled from the gravitational equations of motion. Our model relies on two key ingredients: a nonlocal constraint on the action, which forces the spacetime average of the Lagrangian density to vanish, and a dynamical way for this condition to be satisfied classically with arbitrary matter content. We implement the former condition with a spatially-constant Lagrange multiplier associated with the volume form and the latter by including a free four-form gauge field strength in the action. These two features are enough to remove the cosmological constant from the Einstein equation. The model is consistent with all cosmological and experimental bounds on modification of gravity and allows for both cosmic inflation and the present epoch of acceleration.
In all supersymmetric theories, gravitinos, with mass suppressed by the Planck scale, are an obvious candidate for dark matter; but if gravitinos ever reached thermal equilibrium, such dark matter is apparently either too abundant or too hot, and is excluded. However, in theories with an axion, a saxion condensate is generated during an early era of cosmological history and its late decay dilutes dark matter. We show that such dilution allows previously thermalized gravitinos to account for the observed dark matter over very wide ranges of gravitino mass, keV < $m_{3/2}$ < TeV, axion decay constant, $10^9$ GeV < $f_a$ < $10^{16}$ GeV, and saxion mass, 10 MeV < $m_s$ < 100 TeV. Constraints on this parameter space are studied from BBN, supersymmetry breaking, gravitino and axino production from freeze-in and saxion decay, and from axion production from both misalignment and parametric resonance mechanisms. Large allowed regions of $(m_{3/2}, f_a, m_s)$ remain, but differ for DFSZ and KSVZ theories. Superpartner production at colliders may lead to events with displaced vertices and kinks, and may contain saxions decaying to $(WW,ZZ,hh), gg, \gamma \gamma$ or a pair of Standard Model fermions. Freeze-in may lead to a sub-dominant warm component of gravitino dark matter, and saxion decay to axions may lead to dark radiation.
Gravitational radiation is an excellent field for testing theories of gravity in strong gravitational fields. The current observations on the gravitational-wave (GW) bursts by LIGO have already placed various constraints on the alternative theories of gravity. In this paper, we investigate the possible bounds which could be placed on the Brans-Dicke gravity using GW detection from inspiralling compact binaries with the proposed Einstein Telescope, a third-generation GW detector. We first calculate in details the waveforms of gravitational radiation in the lowest post-Newtonian approximation, including the tensor and scalar fields, which can be divided into the three polarization modes, i.e. "plus mode", "cross mode" and "breathing mode". Applying the stationary phase approximation, we obtain their Fourier transforms, and derive the correction terms in amplitude, phase and polarization of GWs, relative to the corresponding results in General Relativity. Imposing the noise level of Einstein Telescope, we find that the GW detection from inspiralling compact binaries, composed of a neutron star and a black hole, can place stringent constraints on the Brans-Dicke gravity. The bound on the coupling constant $\omega_{\rm BD}$ depends on the mass, sky-position, orbital angle, polarization angle, luminosity distance, redshift distribution and total observed number $N_{\rm GW}$ of the binary systems. Taking into account all the burst events up to redshift $z=5$, we find that the bound could be $\omega_{\rm BD}\gtrsim 10^{6}\times(N_{\rm GW}/10^4)^{1/2}$. Even for the conservative estimation with $10^{4}$ observed events, the bound is still more than one order tighter than the current limit from solar system experiments. So, we conclude that Einstein Telescope will provide a powerful platform to test alternative theories of gravity.
We provide an updated calibration of CIV $\lambda1549$ broad emission line-based single-epoch (SE) black hole (BH) mass estimators for active galactic nuclei (AGNs) using new data for six reverberation-mapped AGNs at redshift $z=0.005-0.028$ with BH masses (bolometric luminosities) in the range $10^{6.5}-10^{7.5}$ $M_{\odot}$ ($10^{41.7}-10^{43.8}$ erg s$^{\rm -1}$). New rest-frame UV-to-optical spectra covering 1150-5700 \AA\ for the six AGNs were obtained with the Hubble Space Telescope (HST). Multi-component spectral decompositions of the HST spectra were used to measure SE emission-line widths for the CIV, MgII, and H$\beta$ lines as well as continuum luminosities in the spectral region around each line. We combine the new data with similar measurements for a previous archival sample of 25 AGNs to derive the most consistent and accurate calibrations of the CIV-based SE BH mass estimators against the H$\beta$ reverberation-based masses, using three different measures of broad-line width: full-width at half maximum (FWHM), line dispersion ($\sigma_{\rm line}$) and mean absolute deviation (MAD). The newly expanded sample at redshift $z=0.005-0.234$ covers a dynamic range in BH mass (bolometric luminosity) of $\log\ M_{\rm BH}/M_{\odot} = 6.5-9.1$ ($\log\ L_{\rm bol}/$erg s$^{\rm -1}=41.7-46.9$), and we derive the new CIV-based mass estimators using a Bayesian linear regression analysis over this range. We generally recommend the use of $\sigma_{\rm line}$ or MAD rather than FWHM to obtain a less biased velocity measurement of the CIV emission line, because its narrow-line component contribution is difficult to decompose from the broad-line profile.
In string-derived supergravity theory, K\"{a}hler metric of chiral matter fields often has a pole. Such K\"{a}hler metric is interesting from the viewpoint of the framework of the pole inflation, where the scalar potential can be stretched out to be flat around the pole for a canonically normalized field and inflation can be realized. However, when K\"{a}hler metric has a pole, the scalar potential can also have a pole at the same point in supergravity theory. We study such supergravity models with the pole, and provide numerical analysis of inflationary dynamics and resultant density perturbation. We also examine attractor behavior of our model.
We present the results of our search for the faint galaxies near the end of the Reionisation Epoch. This has been done using very deep OSIRIS images obtained at the Gran Telescopio Canarias (GTC). Our observations focus around two close, massive Lyman Alpha Emitters (LAEs) at redshift 6.5, discovered in the SXDS field within a large-scale overdense region (Ouchi et al. 2010). The total GTC observing time in three medium band filters (F883w35, F913w25 and F941w33) is over 34 hours covering $7.0\times8.5$ arcmin$^2$ (or $\sim30,000$ Mpc$^3$ at $z=6.5$). In addition to the two spectroscopically confirmed LAEs in the field, we have identified 45 other LAE candidates. The preliminary luminosity function derived from our observations, assuming a spectroscopic confirmation success rate of $\frac{2}{3}$ as in previous surveys, suggests this area is about 2 times denser than the general field galaxy population at $z=6.5$. If confirmed spectroscopically, our results will imply the discovery of one of the earliest protoclusters in the universe, which will evolve to resemble the most massive galaxy clusters today.
We put forward a new proposal for generating the baryon asymmetry of the universe by making use of the dynamics of a $\mathrm{U}(1)$ scalar field coupled to dark matter. High dark matter densities cause the $\mathrm{U}(1)$ symmetry to break spontaneously so that the field acquires a large vacuum expectation value. The symmetry is restored when the density redshifts below a critical value, resulting in the coherent oscillation of the scalar field. A net $B-L$ number can be generated either via baryon number-conserving couplings to the standard model or through small symmetry-violating operators and the subsequent decay of the scalar condensate.
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The amplitude of the ionizing background that pervades the intergalactic medium (IGM) at the end of the epoch of reionization provides a valuable constraint on the emissivity of the sources which reionized the Universe. While measurements of the ionizing background at lower redshifts rely on a simulation-calibrated mapping between the photoionization rate and the mean transmission of the Ly$\alpha$ forest, at $z\gtrsim6$ the IGM becomes increasingly opaque, and transmission arises solely in narrow spikes separated by saturated Gunn-Peterson troughs. In this regime, the traditional approach of measuring the average transmission over large $\sim 50$ Mpc$/h$ regions is less sensitive and sub-optimal. Additionally, the five times smaller oscillator strength of the Ly$\beta$ transition implies the Ly$\beta$ forest is considerably more transparent at $z\gtrsim6$, even in the presence of contamination by foreground $z\sim 5$ Ly$\alpha$ forest absorption. In this work we present a novel statistical approach to analyze the joint distribution of transmission spikes in the co-spatial $z\sim 6$ Ly$\alpha$ and Ly$\beta$ forests. Our method relies on Approximate Bayesian Computation (ABC), which circumvents the necessity of computing the intractable likelihood function describing the highly correlated Ly$\alpha$ and Ly$\beta$ transmission. We apply ABC to mock data generated from a large-volume hydrodynamical simulation combined with a state-of-the-art model of ionizing background fluctuations in the post-reionization IGM, and show that it is sensitive to higher IGM neutral hydrogen fractions than previous techniques. As a proof of concept, we apply this methodology to a real spectrum of a $z=6.54$ quasar and measure the ionizing background from $5.4\leq z \leq 6.4$ along this sightline with $\sim0.2$ dex statistical uncertainties.
Large variations in the effective optical depth of the He II Ly$\alpha$ forest have been observed at $z\gtrsim2.7$, but the physical nature of these variations is uncertain: either the Universe is still undergoing the process of He II reionization, or the Universe is highly ionized but the He II-ionizing background fluctuates significantly on large scales. In an effort to build upon our understanding of the latter scenario, we present a novel model for the evolution of ionizing background fluctuations. Previous models have assumed the mean free path of ionizing photons to be spatially uniform, ignoring the dependence of that scale on the local ionization state of the intergalactic medium (IGM). This assumption is reasonable when the mean free path is large compared to the average distance between the primary sources of He II-ionizing photons, $\gtrsim L_\star$ quasars. However, when this is no longer the case, the background fluctuations become more severe, and an accurate description of the average propagation of ionizing photons through the IGM requires additionally accounting for the fluctuations in opacity. We demonstrate the importance of this effect by constructing 3D semi-analytic models of the helium ionizing background from $z=2.5$-$3.5$ that explicitly include a spatially varying mean free path of ionizing photons. The resulting distribution of effective optical depths at large scales in the He II Ly$\alpha$ forest is very similar to the latest observations with HST/COS at $2.5 \lesssim z \lesssim 3.5$.
We extend the study of long mode perturbations to other large scale observables such as cosmic rulers, galaxy number counts and halo bias. The long mode is a pure gradient mode that is still outside observer's horizon. We insist that gradient mode effects on observables vanish. It is also crucial that the expressions for observables are relativistic. This allows us to show that the effects of a gradient mode on the large scale observables vanishes identically in a relativistic frame work. To study the potential modulation effect of the gradient mode on halo bias, we derive a consistency condition to the first order in gradient expansion. We find that the matter variance at a fixed physical scale is not modulated by the long gradient mode perturbations when the consistency condition holds. This shows that the contribution of long gradient modes to bias vanishes in this frame work.
We analyse the clustering of cosmic voids using a numerical simulation and the main galaxy sample from the Sloan Digital Sky Survey. We take into account the classification of voids into two types that resemble different evolutionary modes: those with a rising integrated density profile (void-in-void mode, or R-type) and voids with shells (void-in-cloud mode, or S-type). The results show that voids of the same type have stronger clustering than the full sample. We use the correlation analysis to define void clumps, associations with at least two voids separated by a distance of at most the mean void separation. In order to study the spatial configuration of void clumps, we compute the minimal spanning tree and analyse their multiplicity, maximum length and elongation parameter. We further study the dynamics of the smaller sphere that encloses all the voids in each clump. Although the global densities of void clumps are different according to their member-void types, the bulk motions of these spheres are remarkably lower than those of randomly placed spheres with the same radii distribution. In addition, the coherence of pairwise void motions does not strongly depend on whether voids belong to the same clump. Void clumps are useful to analyse the large-scale flows around voids, since voids embedded in large underdense regions are mostly in the void-in-void regime, were the expansion of the larger region produces the separation of voids. Similarly, voids around overdense regions form clumps that are in collapse, as reflected in the relative velocities of voids that are mostly approaching.
We examine the cosmological constraints that can be achieved with a galaxy cluster survey with the future CORE space mission. Using realistic simulations of the millimeter sky, produced with the latest version of the Planck Sky Model, we characterize the CORE cluster catalogues as a function of the main mission performance parameters. We pay particular attention to telescope size, key to improved angular resolution, and discuss the comparison and the complementarity of CORE with ambitious future ground-based CMB experiments that could be deployed in the next decade. A possible CORE mission concept with a 150 cm diameter primary mirror can detect of the order of 50,000 clusters through the thermal Sunyaev-Zeldovich effect (SZE). The total yield increases (decreases) by 25% when increasing (decreasing) the mirror diameter by 30 cm. The 150 cm telescope configuration will detect the most massive clusters ($>10^{14}\, M_\odot$) at redshift $z>1.5$ over the whole sky, although the exact number above this redshift is tied to the uncertain evolution of the cluster SZE flux-mass relation; assuming self-similar evolution, CORE will detect $\sim 500$ clusters at redshift $z>1.5$. This changes to 800 (200) when increasing (decreasing) the mirror size by 30 cm. CORE will be able to measure individual cluster halo masses through lensing of the cosmic microwave background anisotropies with a 1-$\sigma$ sensitivity of $4\times10^{14} M_\odot$, for a 120 cm aperture telescope, and $10^{14} M_\odot$ for a 180 cm one. [abridged]
The tensor to scalar ratio is affected by the evolution of the large-scale gauge fields potentially amplified during an inflationary stage of expansion. After deriving the exact evolution equations for the scalar and tensor modes of the geometry in the presence of dynamical gauge fields, it is shown that the tensor to scalar ratio is bounded from below by the dominance of the adiabatic contribution and it cannot be smaller than one thousands whenever the magnetogenesis is driven by a single inflaton field.
We construct an updated and extended compilation of growth rate data consisting of 34 points and including corrections for model dependence. In order to maximize the independence of the datapoints we also construct a subsample of this compilation (`Gold' growth dataset) which consists of 18 datapoints. We test the consistency of this dataset with the best fit Planck15/$\Lambda$CDM parameters in the context of General Relativity (GR) using the evolution equation for the growth factor $\delta(a)$ with a $w$CDM background. We find tension at the $\sim 3 \sigma$ level between the best fit parameters $w$ (the dark energy equation of state), $\Omega_{0m}$ (the matter density parameter) and $\sigma_8$ (the matter power spectrum normalization on scales $8h^{-1}$Mpc) and the corresponding Planck15/$\Lambda$CDM parameters. We show that the tension disappears if we allow for evolution of the effective Newton's constant, parametrized as $G_{eff}(a)/G_N = 1 + g_a(1-a)^n-g_a(1-a)^{2n}$ with $n\ge2$ where $g_a$, $n$ are parameters of the model, $a$ is the scale factor and $z = 1/a-1$ is the redshift. This parametrization satisfies three criteria: a. $G_{eff} > 0$, b. Consistency with Big Bang Nucleosynthesis ($G_{eff}(a\ll 1)/G_N=1$), c. Consistency with solar system tests ($G_{eff}(a=1)/G_N=1$ and $G_{eff}'(a=1)/G_N=0$). We show that the best fit form of $G_{eff}(z)$ obtained from the growth data corresponds to weakening gravity at recent redshifts (decreasing function of $z$) and we demonstrate that this behavior is not consistent with any scalar-tensor Lagrangian with a real scalar field. Finally, we use MGCAMB to find the best fit $G_{eff}(z)$ obtained from the Planck CMB power spectrum on large angular scales and show that it is a mildly increasing function of $z$, in $3\sigma$ tension with the corresponding decreasing best fit $G_{eff}(z)$ obtained from the growth data.
The small-scale crisis, discrepancies between observations and N-body simulations, may imply suppressed matter fluctuations on subgalactic distance scales. Such a suppression could be caused by some early-universe mechanism (e.g., broken scale-invariance during inflation), leading to a modification of the primordial power spectrum at the onset of the radiation-domination era. Alternatively, it may be due to nontrivial dark-matter properties (e.g., new dark-matter interactions or warm dark matter) that affect the matter power spectrum at late times, during radiation domination, after the perturbations re-enter the horizon. We show that early- and late-time suppression mechanisms can be distinguished by measurement of the $\mu$ distortion to the frequency spectrum of the cosmic microwave background. This is because the $\mu$ distortion is suppressed, if the power suppression is primordial, relative to the value expected from the dissipation of standard nearly-scale-invariant fluctuations. We emphasize that the standard prediction of the $\mu$ distortion remains unchanged in late-time scenarios even if the dark-matter effects occur before or during the era (redshifts $5\times 10^4 \lesssim z \lesssim 2\times 10^6$) at which $\mu$ distortions are generated.
Matter bounces refer to scenarios wherein the universe contracts at early times as in a matter dominated epoch until the scale factor reaches a minimum, after which it starts expanding. While such scenarios are known to lead to scale invariant spectra of primordial perturbations after the bounce, the challenge has been to construct completely symmetric bounces that lead to a tensor-to-scalar ratio which is small enough to be consistent with the recent cosmological data. In this work, we construct a model involving two scalar fields (a canonical field and a non-canonical ghost field) to drive the symmetric matter bounce and study the evolution of the scalar perturbations in the model. If we consider the scale associated with the bounce to be of the order of the Planck scale, the model is completely described in terms of only one parameter, viz the value of the scale factor at the bounce. We evolve the scalar perturbations numerically across the bounce and evaluate the scalar power spectra after the bounce. We show that, while the scalar and tensor perturbation spectra are scale invariant over scales of cosmological interest, the tensor-to-scalar ratio proves to be much smaller than the current upper bound from the observations of the cosmic microwave background anisotropies by the Planck mission. We also support our numerical analysis with analytical arguments.
We have previously derived the effect of soft graviton modes on the quantum state of de Sitter using spontaneously broken asymptotic symmetries. In the present paper we reinterpret this effect in terms of particle production and relate the quantum states with and without soft modes by means of Bogoliubov transformations. This also enables us to address the much discussed issues regarding the observability of infrared effects in de Sitter from a new perspective. While it is commonly agreed that infrared effects are not visible to a single sub-horizon observer at late times, we argue that the question is less trivial for a {\it patient observer} who has lived long enough to have a record of the state before the soft mode was created. Though classically there is no obstruction to measuring this effect locally, we give several indications that quantum mechanical uncertainties may censor the effect. We then apply our methods to find a non-perturbative description of the quantum state pertaining to the Page time of de Sitter, and derive with these new methods the probability distribution for the local quantum states of de Sitter and slow-roll inflation in the presence of long modes. Finally, we use this to formulate a precise criterion for the existence of eternal inflation in general classes of slow-roll inflation.
We present a systematic introduction to the diagrammatic method for practical calculations in inflationary cosmology, based on Schwinger-Keldysh path integral formalism. We show in particular that the diagrammatic rules can be derived directly from a classical Lagrangian even in the presence of derivative couplings. Furthermore, we use quasi-single-field inflation as an example to show how this formalism, combined with the trick of mixed propagator, can significantly simplify the calculation of some in-in correlation functions. The resulting bispectrum includes the lighter scalar case ($m<3H/2$) that has been previously studied, and the heavier scalar case ($m>3H/2$) that has not been explicitly computed for this model. The latter provides a concrete example of quantum primordial standard clocks, in which the clock signals can be observably large.
While traditionally associated with active galactic nuclei (AGN), the properties of the CII], CIII] and CIV emission lines are still uncertain as large, unbiased samples of sources are scarce. We present the first blind, statistical study of CII], CIII] and CIV emitters at $z\sim0.68,1.05,1.53$, respectively, uniformly selected down to a flux limit of $\sim4\times10^{-17}$ erg s$^{-1}$ cm$^{-1}$ through a narrow band survey covering an area of $\sim1.4$ deg$^2$ over COSMOS and UDS. We detect 16 CII], 35 CIII] and 17 CIV emitters, whose nature we investigate using optical colours as well as HST, X-ray, radio and far infra-red data. We find that $z\sim0.7$ CII] emitters are consistent with a mixture of blue (UV slope $\beta=-2.0\pm0.4$) star forming galaxies with disky HST structure and AGN with Seyfert-like morphologies. Bright CII] emitters have individual X-ray detections as well as high average black hole accretion rates (BHAR) of $\sim0.1$ $M_{\odot}$ yr$^{-1}$. CIII] emitters at $z\sim1.05$ trace a general population of SF galaxies, with $\beta=-0.8\pm1.1$, a variety of optical morphologies, including isolated and interacting galaxies and low BHAR ($<0.02$ $M_{\odot}$ yr$^{-1}$). Our CIV emitters at $z\sim1.5$ are consistent with young, blue quasars ($\beta\sim-1.9$) with point-like optical morphologies, bright X-ray counterparts and large BHAR ($0.8$ $M_{\odot}$ yr$^{-1}$). We also find some surprising CII], CIII] and CIV emitters with rest-frame equivalent widths which could be as large as $50-100$ {\AA}. AGN or spatial offsets between the UV continuum stellar disk and the line emitting regions may explain the large EW. These bright CII], CIII] and CIV emitters are ideal candidates for spectroscopic follow up to fully unveil their nature.
We study the correlation between the specific star formation rate of central galaxies and neighbour galaxies, also known as 'galactic conformity', out to several Mpc scales using three different semi-analytic models (SAMs). It has been suggested that SAMs may not show the strong signal of conformity measured in observations. In all the models, when the selection of primary galaxies is based on an isolation criterion in real space, we measure a strong galactic conformity where the mean quenched fraction around quenched primary galaxies is higher than that around star-forming primary galaxies of the same stellar mass. The cumulative signal-to-noise ratio, which is used to evaluate the significance and extension in distance of conformity, depends strongly on the SAM. The two-halo conformity is significant as far as ~5 Mpc/h. The overall signal of galactic conformity decreases when we remove satellites in the selection of primary galaxies. In this case, there is no significant two-halo conformity in two SAMs. For the other SAM, the two-halo conformity is only detected between isolated, central galaxies in relatively low-mass haloes ($M_{\rm halo}$ $< 10^{12.4}$ $h^{-1}~\rm{ M_{\bigodot}}$) and their neighbours. Finally, we explore the case when the secondary galaxies correspond to central galaxies in the SAMs as an attempt to measure the conformity between distinct haloes. Our results show that there is no conformity beyond ~3 Mpc/h. The conformity measured out to scales of 3$-$4 Mpc/h can be related to the environmental influence of large galaxy clusters around near central galaxies.
We model the cluster A1689 in two modified MOND frameworks (EMOND and what we call generalised MOND or GMOND) with the aim of determining whether it is possible to explain the inferred acceleration profile, from gravitational lensing, without the aid of dark matter. We also compare our result to predictions from MOG/STVG and Emergent Gravity. By using a baryonic mass model, we determine the total gravitational acceleration predicted by the modified gravitational equations and compare the result to NFW profiles of dark matter studies on A1689 from the literature. Theory parameters are inferred empirically, with the aid of previous work. We are able to reproduce the desired acceleration profile of A1689 for GMOND, EMOND and MOG, but not Emergent Gravity. There is much more work which needs to be conducted with regards to understanding how the GMOND parameters behave in different environments. Furthermore, we show that the exact baryonic profile becomes very important when undertaking modified gravity modelling rather than {\Lambda}CDM.
In the $\Lambda$CDM framework, presenting nonrelativistic matter inhomogeneities as discrete massive particles, we develop the second-order cosmological perturbation theory. Our approach relies on the weak gravitational field limit. The derived equations for the second-order scalar, vector and tensor metric corrections are suitable at arbitrary distances including regions with nonlinear contrasts of the matter density. We thoroughly verify fulfilment of all Einstein equations as well as self-consistency of order assignments. In addition, we achieve logical positive results in the Minkowski background limit. Feasible investigations of the cosmological backreaction manifestations by means of relativistic simulations are also outlined.
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