Using our cosmological radiative transfer code, we study the implications of the updated QSO emissivity and star formation history for the escape fraction (f_esc) of hydrogen ionizing photons from galaxies. We estimate the f_esc that is required to reionize the Universe and to maintain the ionization state of the intergalactic medium in the post-reionization era. At z>5.5, we show that a constant f_esc of 0.14 to 0.22 is sufficient to reionize the Universe. At z<3.5, consistent with various observations, we find that f_esc can have values from 0 to 0.05. However, a steep rise in f_esc, of at least a factor of ~3, is required between z=3.5 to 5.5. It results from a rapidly decreasing QSO emissivity at z>3 together with a nearly constant measured H I photoionization rates at 3<z<5. We show that, this requirement of a steep rise in f_esc over a very short time can be relaxed if we consider the contribution from a recently found large number density of faint QSOs at z>4. In addition, a simple extrapolation of the contribution of such QSOs to high-z suggests that QSOs alone can reionize the Universe. This implies, at z>3.5, that either the properties of galaxies should evolve rapidly to increase the f_esc or most of the low mass galaxies should host massive blackholes and sustain accretion over a prolonged period. These results motivate a careful investigation of theoretical predictions of these alternate scenarios that can be distinguished using future observations. Moreover, it is also very important to revisit the measurements of H I photoionization rates that are crucial to the analysis presented here.
The integrated Sachs-Wolfe (ISW) effect and its non-linear extension Rees-Sciama (RS) effect provide us the information of the time evolution of gravitational potential. The cross-correlation between the cosmic microwave background (CMB) and the large scale structure (LSS) is known as a promising way to extract the ISW (RS) effect. It is known that the RS effect shows the unique behavior by changing the anti-correlated cross correlation between the CMB and the mass tracer into the positively correlated cross correlation compared to the linear ISW effect. We show that the dependence of this flipping scale of the cross-correlation between RS and weak lensing on dark energy models. However, there exists the degeneracy between DE and $\Omega_{\rm{m}0}$ which might be broken by redshift dependent observables. The cross-correlation between the momentum field and the density field might be served as the better observable to be used for this purpose.
The anisotropic 2-point correlation function (2PCF) of galaxies measures pairwise clustering as a function of the pair separation's angle to the line of sight. The latter is often defined as either the angle bisector of the observer-galaxy-pair triangle or the vector from the observer to the separation midpoint. Here we show how to accelerate either of these measurements with Fourier Transforms, using a slight generalization of the Yamamoto et al. (2006) estimator in which each member of the pair is used successively as the line of sight. We also present perturbation theory predictions for our generalized estimator including wide-angle corrections.
We study preheating after hilltop inflation where the inflaton couples to another scalar field, e.g. a right-handed sneutrino, which provides a mechanism for generating the correct initial conditions for inflation and also a decay channel for the inflaton that allows for reheating and non-thermal leptogenesis. In the presence of such a coupling, we find that after the known phases of preheating during which the inflaton field becomes fully inhomogeneous, there can be a subsequent preheating phase where the fluctuations of the other field get resonantly enhanced, from initial vacuum fluctuations up to amplitudes of the same order (and even larger) as the ones of the inflaton field. This resonant enhancement differs from the usual parametric resonance as the inflaton field is highly inhomogeneous at the time the enhancement takes place. We study this effect using lattice simulations as well as semi-analytically with a generalized Floquet analysis for inhomogeneous background fields.
This paper combines observational datasets and cosmological simulations to generate realistic numerical replicas of the nearby Universe. These latter are excellent laboratories for studies of the non-linear process of structure formation in our neighborhood. With measurements of radial peculiar velocities in the Local Universe (cosmicflows-2) and a newly developed technique, we produce Constrained Local UniversE Simulations (CLUES). To assess the quality of these constrained simulations, we compare them with random simulations as well as with local observations. The cosmic variance, defined as the mean one-sigma scatter of cell-to-cell comparison between two fields, is significantly smaller for the constrained simulations than for the random simulations. Within the inner part of the box where most of the constraints are, the scatter is smaller by a factor 2 to 3 on a 5 Mpc/h scale with respect to that found for random simulations. This one-sigma scatter obtained when comparing the simulated and the observation-reconstructed velocity fields is only 104 +/- 4 km/s i.e. the linear theory threshold. These two results demonstrate that these simulations are in agreement with each other and with the observations of our neighborhood. For the first time, simulations constrained with observational radial peculiar velocities resemble the Local Universe up to a distance of 150 Mpc/h on a scale of a few tens of megaparsecs. When focusing on the inner part of the box, the resemblance with our cosmic neighborhood extends to a few megaparsecs (< 5 Mpc/h). The simulations provide a proper Large Scale environment for studies of the formation of nearby objects.
We investigate the impact of coulomb screening on primordial nucleosynthesis in a universe having scale factor that evolves linearly with time. Coulomb screening affects primordial nucleosynthesis via enhancement of thermonuclear reaction rates. This enhancement is determined by the solving Poisson equation within the context of mean field theory (under appropriate conditions during the primordial nucleosynthesis). Using these results, we claim that the mean field estimates of coulomb screening hardly affect the predicted element abundances and nucleosynthesis parameters$, \{\eta_9,\xi_e\}$. The deviations from mean field estimates are also studied in detail by boosting genuine screening results with the screening parameter ($\omega_s$). These deviations show negligible effect on the element abundances and on nucleosynthesis parameters. This work thus rules out the coulomb screening effects on primordial nucleosynthesis in slow evolving models and confirms that constraints in ref.[7] on nucleosynthesis parameters remain unaltered.
Diffuse radio emission in galaxy clusters is known to be related to cluster mass and cluster dynamical state. We collect the observed fluxes of radio halos, relics and mini-halos for a sample of galaxy clusters from literature, and calculate their radio powers. We then obtain the values of cluster mass or mass proxies from previous observations, and also obtain the various dynamical parameters of these galaxy clusters from optical and X-ray data. The radio power of relics, halos and mini-halos are correlated with the cluster masses or mass proxies, as found by previous authors, with the correlations concerning giant radio halos being, in general, the strongest ones. We found that the inclusion of dynamical parameters as the third dimension can significantly reduce the data scatter for the scaling relations, especially for radio halos. We therefore conclude that the substructures in X-ray images of galaxy clusters and the irregular distributions of optical brightness of member galaxies can be used to quantitatively characterize the shock waves and turbulence in intracluster medium responsible for reaccelerating particles to generate the observed diffuse radio emission. The power of radio halos and relics are correlated with cluster mass proxies and dynamical parameters in the form of a fundamental plane.
We explore the hypothesis of having an approximate lepton number conservation as a way to achieve a successful leptogenesis in low-scale seesaw mechanisms. The smallness of the active neutrino masses, as well as a strong degeneracy in the mass spectrum of the heavy sterile states, are both consequence of the assumed approximate symmetry. We propose a minimal extension of the Standard Model in order to implement the idea, and perform an analytical and numerical study to determine the viable solutions in the model and the testability of this leptogenesis scenario in future experiments.
The detection of optical surface brightness structures in the sky with magnitudes fainter than 30 mag/arcsec^2 (3sigma in 10x10 arcsec boxes; r-band) has remained elusive in current photometric deep surveys. Here we show how present-day 10 meter class telescopes can provide broadband imaging 1.5-2 mag deeper than most previous results within a reasonable amount of time (i.e. <10h on source integration). In particular, we illustrate the ability of the 10.4 m Gran Telescopio de Canarias (GTC) telescope to produce imaging with a limiting surface brightness of 31.5 mag/arcsec^2 (3sigma in 10x10 arcsec boxes; r-band) using 8.1 hours on source. We apply this power to explore the stellar halo of the galaxy UGC00180, a galaxy analogous to M31 located at ~150 Mpc, by obtaining a surface brightness radial profile down to mu_r~33 mag/arcsec^2. This depth is similar to that obtained using star counts techniques of Local Group galaxies, but is achieved at a distance where this technique is unfeasible. We find that the mass of the stellar halo of this galaxy is ~4x10^9 Msun, i.e. 3+-1% of the total stellar mass of the whole system. This amount of mass in the stellar halo is in agreement with current theoretical expectations for galaxies of this kind.
We apply the Jeans Axisymmetric Multi-Gaussian Expansion method to the stellar kinematic maps of 40 Sa-Sd EDGE-CALIFA galaxies and derive their circular velocity curves (CVCs). The CVCs are classified using the Dynamical Classification method developed in Kalinova et al. (2015) . We also calculate the observational baryon efficiency, OBE, where $M_*/M_b=M_*/(M_*+M_{HI}+M_{H_2})$ of the galaxies using their stellar mass, total neutral hydrogen mass and total molecular gas from CO luminosities. Slow-rising, Flat and Round-peaked CVC types correspond to specific OBEs, stellar and dark matter (DM) halo mass values, while the Sharp-peaked CVCs span in the whole DM halo mass range of $10^{11}-10^{14} M_{\odot}$.
In this paper, we consider rolling tachyon, with steep run-away type of potentials non-minimally coupled to massive neutrino matter. The coupling dynamically builds up at late times as neutrino matter turns non-relativistic. In case of scaling and string inspired potentials, we have shown that non-minimal coupling leads to minimum in the field potential. Given a suitable choice of model parameters, it is shown to give rise to late-time acceleration with the desired equation of state.
We investigate the pre-inflationary dynamics of inflation with the Starobinsky potential, favored by recent data from the Planck mission, using techniques developed to study cosmological perturbations on quantum spacetimes in the framework of loop quantum gravity. We find that for a large part of the initial data, inflation compatible with observations occurs. There exists a subset of this initial data that leads to quantum gravity signatures that are potentially observable. Interestingly, despite the different inflationary dynamics, these quantum gravity corrections to the powerspectra are similar to those obtained for inflation with a quadratic potential, including suppression of power at large scales. Furthermore, for super horizon modes the tensor modes show deviations from the standard inflationary paradigm that are unique to the Starobinsky potential and could be important for non-Gaussian modulation and tensor fossils.
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We study how the hot Universe evolves and acquires the prevailing vacuum state, demonstrating that in specific conditions which are believed to apply, the Universe becomes frozen into the state with the smallest value of Higgs vacuum field $v=\langle h\rangle$, even if this is not the state of lowest energy. This supports the false vacuum dark energy $\Lambda$-model. Under several likely hypotheses we determine the temperature in the evolution of the Universe at which two vacuua $v_1, v_2$ can swap between being true and false. We evaluate the dynamical surface pressure on domain walls between low and high mass vaccua due to the presence of matter and show that the low mass state remains the preferred vacuum of the Universe.
We report on the energy-momentum correlators obtained with recent numerical simulations of the Abelian Higgs model, essential for the computation of cosmic microwave background and matter perturbations of cosmic strings. Due to significant improvements both in raw computing power and in our parallel simulation framework, the dynamical range of the simulations has increased four-fold both in space and time, and for the first time we are able to simulate strings with a constant physical width in both the radiation and matter eras. The new simulations improve the accuracy of the measurements of the correlation functions at the horizon scale and confirm the shape around the peak. The normalization is slightly higher in the high wave-number tails, due to a small increase in the string density. We study for the first time the behaviour of the correlators across cosmological transitions, and discover that the correlation functions evolve adiabatically, ie the network adapts quickly to changes in the expansion rate. We propose a new method for constructing source functions for Einstein-Boltzmann integrators, comparing it with two other methods previously used. The new method is more consistent, easier to implement, and significantly more accurate.
Observations of the 21 cm line radiation coming from the epoch of reionization have a great capacity to study the cosmological growth of the Universe. Also, CMB polarization produced by gravitational lensing has a large amount of information about the growth of matter fluctuations at late time. In this thesis, we investigate their sensitivities to the impact of neutrino property on the growth of density fluctuations, such as the total neutrino mass, the neutrino mass hierarchy, the effective number of neutrino species (extra radiation), and the lepton asymmetry of our Universe. We will show that by combining the precise CMB polarization observations with Square Kilometer Array (SKA) we can measure the impact of non-zero neutrino mass on the growth of density fluctuation, and determine the neutrino mass hierarchy at 2 sigma level if the total neutrino mass is smaller than 0.1 eV. Additionally, we will show that by using these combinations we can constrain the lepton asymmetry better than big-bang nucleosynthesis (BBN). Besides we discuss constraints on that in the presence of some extra radiation, and show that the 21 cm line observations can substantially improve the constraints obtained by CMB alone, and allow us to distinguish the effects of the lepton asymmetry from those of extra radiation.
We present the first application of a new foreground removal pipeline to the current leading HI intensity mapping dataset, obtained by the Green Bank Telescope (GBT). We study the 15hr and 1hr field data of the GBT observations previously presented in Masui et al. (2013) and Switzer et al. (2013) covering about 41 square degrees at 0.6 < z < 1.0 which overlaps with the WiggleZ galaxy survey employed for the cross-correlation with the maps. In the presented pipeline, we subtract the Galactic foreground continuum and the point source contaminations using an independent component analysis technique (fastica) and develop a description for a Fourier-based optimal weighting estimator to compute the temperature power spectrum of the intensity maps and cross-correlation with the galaxy survey data. We show that fastica is a reliable tool to subtract diffuse and point-source emission by using the non-Gaussian nature of their probability functions. The power spectra of the intensity maps and the cross-correlation with WiggleZ is typically an order of magnitude higher than the previous findings by the GBT team. fastica is a very conservative subtraction technique and is not able to remove anisotropic noise contaminations caused by instrumental systematics unlike the singular value decomposition method which does not discriminate components according to their statistical properties. We confirm that foreground subtraction with fastica is robust against 21cm signal loss as seen by the converged amplitude of the cross-correlation of the intensity maps with the WiggleZ data.
We study the effect of long gradient modes on large scale observables. When defined correctly, genuine observables should not only be gauge invariant but also devoid of any gauge artifacts. One such gauge artifact is a pure gradient mode. Using the relativistic formulation of large scale observables, we confirm that a long gradient mode which is still outside observer's horizon leaves no imprint on the large scale observables at first order. These include the cosmic rulers and the number counts. This confirms the existing method for relativistically defined observables. The general relativistic bias relation for the halos and galaxies is also invariant under the presence of a long gradient mode perturbation. The observed power spectrum is not affected by this long mode.
We evaluate the local variance of the Hubble Constant $H_0$ with low-z Type Ia Supernovae (SNe). Our analyses are performed using a hemispherical comparison procedure to test whether the bulk flow motion can reconcile the measurement of the Hubble Constant $H_0$ from standard candles ($H_0 = 73.8 \pm 2.4 \; \mathrm{km \; s}^{-1}\; \mathrm{Mpc}^{-1}$) with that of the Planck's Cosmic Microwave Background data ($67.8 \pm 0.9 \; \mathrm{km \; s}^{-1} \mathrm{Mpc}^{-1}$). We obtain that $H_0$ ranges from $68.9 \pm 0.5 \; \mathrm{km \; s}^{-1} \mathrm{Mpc}^{-1}$ to $71.2 \pm 0.7 \; \mathrm{km \; s}^{-1} \mathrm{Mpc}^{-1}$ through the celestial sphere, with maximal dipolar anisotropy towards the $(l,b) = (315^{\circ},27^{\circ})$ direction. Interestingly, this result is in good agreement with both $H_0$ estimations, as well as the bulk flow direction reported in the literature. In addition, we assess the statistical significance of this variance with different prescriptions of Monte Carlo simulations, finding a good concordance for its amplitude given the limitation of the SNe data set in terms of celestial coverage and their distance uncertainties. Additionally, we test the null hypothesis of this anisotropic direction being a random effect, albeit we can reject such hypothesis with good statistical significance. We then conclude that the conflict between these different Hubble Constant determinations can be unified by correctly taking into account the bulk flow motion of the local Universe.
We present a simple formula for the average dark energy equation of state at redshifts between those of two observations of baryon acoustic oscillations (BAO). The formula is independent of any parametrization or basis of the dark energy equation of state and essentially independent of the cosmological model. We use this formula to study the well-known tension between Lyman alpha forest BAO and other cosmological probes. Using only the line of sight Lyman alpha forest BAO and BOSS CMASS dataset, there is already more than 2 sigma tension with the standard LambdaCDM cosmological model which implies that either (i) The BOSS Lyman alpha forest measurement of the Hubble parameter was too low as a result of a statistical fluctuation or systematic error or else (ii) the dark energy equation of state falls steeply at high redshift.
Starting with the relativistic Boltzmann equation for a system of particles defined by a distribution function, we have derived the virial relation for a spherical structure within an expanding background in the context of general relativity. This generalized form of the virial relation is then applied to the static case of a spherically symmetric structure to see the difference in the simplest case to the Newtonian relation. A relativistic Mass-Temperature relation for this simple case is also derived which can be applied to compact objects in astrophysics. Our general virial relation is then applied to the non-static case of a structure within an expanding universe where an extra term, usually missed in studies of structures in the presence of the dark energy, appears.
A model of dark sector where $O({\rm few~GeV})$ mass dark matter particles $\chi$ are supplied by a lighter dark force mediator $V$, $m_V \ll m_\chi$, is motivated by the recently discovered mismatch between simulated and observed shapes of galactic haloes. Such models, in general, provide a challenge for direct detection efforts and collider searches. We show that for a large range of coupling constants and masses, the production and decay of the bound states of $\chi$, such as $0^{-+}$ and $1^{--}$ states, $\eta_D$ and $ \Upsilon_D$, is an important search channel. We show that $e^+e^-\to \eta_D +V$ or $\Upsilon_D +\gamma$ production at $B$-factories for $\alpha_D > 0.1$ is sufficiently strong to result in multiple pairs of charged leptons and pions via $\eta_D\to 2V \to 2(l^+l^-)$ and $\Upsilon_D\to 3V \to 3(l^+l^-)$ $(l=e,\mu,\pi)$. The absence of such final states in the existing searches performed at BaBar and Belle sets new constraints on the parameter space of the model. We also show that a search for multiple bremsstrahlung of dark force mediators, $e^+e^-\to \chi\bar\chi+nV$, resulting in missing energy and multiple leptons, will further improve the sensitivity to self-interacting dark matter.
A popular theory of star formation is gravito-turbulent fragmentation, in which self-gravitating structures are created by turbulence-driven density fluctuations. Simple theories of isothermal fragmentation successfully reproduce the core mass function (CMF) which has a very similar shape to the initial mass function (IMF) of stars. However, numerical simulations of isothermal turbulent fragmentation thus far have not succeeded in identifying a fragment mass scale that is independent of the simulation resolution. Moreover, the fluid equations for magnetized, self-gravitating, isothermal turbulence are scale-free, and do not predict any characteristic mass. In this paper we show that, although an isothermal self-gravitating flow does produce a CMF with a mass scale imposed by the initial conditions, this scale changes as the parent cloud evolves. In addition, the cores that form undergo further fragmentation and after sufficient time forget about their initial conditions, yielding a scale-free pure power-law distribution $\mathrm{d} N/\mathrm{d} M\propto M^{-2}$ for the stellar IMF. We show that this problem can be alleviated by introducing a simple model for stellar radiation feedback. Radiative heating, powered by accretion onto forming stars, arrests the fragmentation cascade and imposes a characteristic mass scale that is nearly independent of the time-evolution or initial conditions in the star-forming cloud, and that agrees well with the peak of the observed IMF. In contrast, models that introduce a stiff equation of state for denser clouds but that do not explicitly include the effects of feedback do not yield an invariant IMF.
We give a review on the SIMP paradigm and discuss a consistent model for SIMP dark mesons in the context of a dark QCD with flavor symmetry. The $Z'$-portal interaction is introduced being compatible with stable dark mesons and is responsible for making the SIMP dark mesons remain in kinetic equilibrium with the SM during the freeze-out process. The SIMP parameter space of the $Z'$ gauge boson can be probed by future collider and direct detection experiments.
We propose a novel leptogenesis scenario at the reheating era. Our setup is minimal in the sense that, in addition to the standard model Lagrangian, we only consider an inflaton and higher dimensional operators. The lepton number asymmetry is produced not by the decay of a heavy particle, but by the scattering between the standard model particles. After the decay of an inflaton, the model is described within the standard model with higher dimensional operators. The Sakharov's three conditions are satisfied by the following way. The violation of the lepton number is realized by the dimension-5 operator. The complex phase comes from the dimension-6 four lepton operator. The universe is out of equilibrium before the reheating is completed. It is found that the successful baryogenesis is realized for the wide range of parameters, the inflaton mass and reheating temperature, depending on the cutoff scale. Since we only rely on the effective Lagrangian, our scenario can be applicable to all mechanisms to generate neutrino Majorana masses.
We report constraints on models of composite inflation based on the slow-roll approximation by using the recent Planck measurement. In so doing, we compare the spectral index of curvature perturbation and the tensor-to-scalar ratio predicted by such models with 2015 Planck data. We find that the results predicted by the models present in this work are still consistent with the Planck analysis.
We study the metric perturbations in the context of restricted $f(R)$ gravity, in which a parameter for deviation from the full diffeomorphisms of space-time is introduced. We demonstrate that one can choose the parameter to remove the induced anisotropic stress, which is present in the usual $f(R)$ gravity. Moreover, to prevent instability for the scalar and tensor metric perturbations, some constraints on the model are obtained.
We argue that the exact degeneracy of vacua in N=1 supergravity can shed light on the smallness of the cosmological constant. The presence of such vacua, which are degenerate to very high accuracy, may also result in small values of the quartic Higgs coupling and its beta function at the Planck scale in the phase in which we live.
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The visibility of LyA emitting galaxies during the Epoch of Reionization is controlled by both diffuse HI patches in large-scale bubble morphology and small-scale absorbers. To investigate the impact on LyA photons, we apply a novel combination of analytic and numerical calculations to three scenarios: (i) the `bubble' model, where only diffuse HI outside ionized bubbles is present; (ii) the `web' model, where HI exists only in overdense self-shielded gas; and (iii) the more realistic 'web-bubble' model, which contains both. Our analysis confirms that there is a degeneracy between the ionization structure of the intergalactic medium (IGM) and the HI fraction inferred from LyA surveys, as the three models suppress LyA flux equally with very different HI fractions. We argue that a joint analysis of the LyA luminosity function and the rest-frame equivalent width distribution/LyA fraction can break this degeneracy and provide constraints on the reionization history and its topology. We further show that constraints can improve if we consider the full shape of the M_UV-dependent redshift evolution of the LyA fraction of Lyman break galaxies. Contrary to conventional wisdom, we find that (i) a drop of LyA fraction larger for UV-faint than for UV-bright galaxies can be reproduced with web and web-bubble models and therefore does not provide exclusive evidence of patchy reionization, and (ii) the IGM-transmission PDF is unimodal for bubble models and bimodal in web models. We further highlight the importance of galaxy-absorber cross-correlation. Comparing our models to observations, the neutral fraction at z~7 is likely to be of order of tens of per cent when interpreted with bubble or web-bubble models. Alternatively, we obtain a conservative lower limit ~1% in the web models, if we allow for a drop in the photoionization rate by a factor of ~100 from the post-reionized universe. [abridged]
Empirical methods for connecting galaxies to their dark matter halos have become essential in interpreting measurements of the spatial statistics of galaxies. Among the most successful of these methods is the technique of subhalo abundance matching, which has to date been used to associate galaxy properties with a small set of halo properties. We generalize this set of halo properties to allow variable dependence on halo concentration, and parameterize the degree of concentration dependence with a single parameter. This parameter provides a smooth interpolation between abundance matching to peak halo mass and to peak halo circular velocity. We characterize the influence of this parameter on two-point clustering, the satellite fraction, and the degree of galaxy assembly bias. We also evaluate the degeneracies between the concentration dependence and the scatter in the abundance matching relation. We show that low redshift clustering measurements from SDSS prefer a moderate amount of concentration dependence --- more than would be indicated by matching galaxy luminosity to the peak halo mass, and less than would be indicated by matching to the peak halo circular velocity. We also show that these results are robust to moderate changes in cosmological parameters, and that the best-fit model from two-point clustering agrees with previous measurements of the satellite fraction. We note that statistical constraints on these models have been (and still are, in most regimes) limited primarily by sample variance in the limited-size simulations, and not in the data. We discuss physical interpretations of these results and their implications for the galaxy-halo connection.
Supernova `Refsdal', multiply imaged by cluster MACS1149.5+2223, represents a rare opportunity to make a true blind test of model predictions in extragalactic astronomy, on a time scale that is short compared to a human lifetime. In order to take advantage of this event, we produced seven gravitational lens models with five independent methods, based on Hubble Space Telescope (HST) Hubble Frontier Field images, along with extensive spectroscopic follow-up from HST and from the Very Large Telescope. We compare the model predictions and show that they agree reasonably well with the measured time delays and magnification ratios between the known images, even though these quantities were not used as input. This agreement is encouraging, considering that the models only provide statistical uncertainties, and do not include additional sources of uncertainties such as structure along the line of sight, cosmology, and the mass sheet degeneracy. We then present the model predictions for the other appearances of SN `Refsdal'. A future image will reach its peak in the first half of 2016, while another image appeared between 1994 and 2004. The past image would have been too faint to be detected in archival images. The future image should be approximately one third as bright as the brightest known images and thus detectable in HST images, as soon as the cluster can be targeted again (beginning 2015 October 30). We will find out soon whether our predictions are correct.
The statistical properties of the temperature anisotropies and polarization of the of cosmic microwave background (CMB) radiation offer a powerful probe of the physics of the early universe. In recent works a statistical procedure based upon the calculation of the kurtosis and skewness of the data in patches of CMB sky-sphere has been proposed and used to investigate the large-angle deviation from Gaussianity in WMAP maps. Here we briefly address the question as to how this analysis of Gaussianity is modified if the foreground-cleaned Planck maps are considered. We show that although the foreground-cleaned Planck maps present significant deviation from Gaussianity of different degrees when a less severe mask is used, they become consistent with Gaussianity, as detected by our indicators, when masked with the union mask U73.
We present results obtained by applying our BAyesian HierArchical Modeling
for the Analysis of Supernova cosmology (BAHAMAS) software package to the 740
spectroscopically confirmed supernovae type Ia (SNIa) from the "Joint
Light-curve Analysis" (JLA) dataset. We simultaneously determine cosmological
parameters and standardization parameters, including host galaxy mass
corrections, residual scatter and object-by-object intrinsic magnitudes.
Combining JLA and Planck Cosmic Microwave Background data, we find significant
discrepancies in cosmological parameter constraints with respect to the
standard analysis: we find Omega_M = 0.399+/-0.027, 2.8\sigma\ higher than
previously reported and w = -0.910+/-0.045, 1.6\sigma\ higher than the standard
analysis. We determine the residual scatter to be sigma_res = 0.104+/-0.005.
We confirm (at the 95% probability level) the existence of two
sub-populations segregated by host galaxy mass, separated at
log_{10}(M/M_solar) = 10, differing in mean intrinsic magnitude by
0.055+/-0.022 mag, lower than previously reported. Cosmological parameter
constraints are however unaffected by inclusion of host galaxy mass
corrections. We find ~4\sigma\ evidence for a sharp drop in the value of the
color correction parameter, beta(z), at a redshift z_trans = 0.662+/-0.055. We
rule out some possible explanations for this behaviour, which remains
unexplained.
The most general scalar-tensor theories of gravity predict a weakening of the gravitational force inside astrophysical bodies. There is a minimum mass for hydrogen burning in stars that is set by the interplay of plasma physics and the theory of gravity. We calculate this for alternative theories of gravity, and find that it is always significantly larger than the general relativity prediction. The observation of several low mass Red Dwarf stars therefore rules out a large class of scalar-tensor gravity theories, and places strong constraints on the cosmological parameters appearing in the effective field theory of dark energy.
A relaxed primordial power spectrum (PPS) of scalar perturbations arising from inflation can impact the dark radiation constraints obtained from Cosmic Microwave Background and other cosmological measurements. If inflation produces a non-standard PPS for the initial fluctuations, a fully thermalized light sterile neutrino can be favoured by CMB observations, instead of being strongly disfavoured. In the case of a thermal axion, the constraints on the axion mass are relaxed when the PPS is different from the standard power law.
In this paper, we address a possible impact of radiative corrections from a heavy scalar field $\chi$ on the curvature perturbation $\zeta$. Integrating out $\chi$, we derive the effective action for $\zeta$, which includes the loop corrections of the heavy field $\chi$. When the mass of $\chi$ is much larger than the Hubble scale $H$, the loop corrections of $\chi$ only yield a local contribution in the effective action and hence the effective action simply gives an action for $\zeta$ in a single field model, where, as is widely known, $\zeta$ is conserved in time after the Hubble crossing time. Meanwhile, when the mass of $\chi$ is comparable to $H$, the loop corrections of $\chi$ can give a non-local contribution to the effective action. Because of the non-local contribution from $\chi$, in general, $\zeta$ may not be conserved, even if the classical background trajectory is determined only by the evolution of the inflaton. In this paper, we derive the condition that $\zeta$ is conserved in time in the presence of the radiative corrections from $\chi$. Namely, we show that when the scaling symmetry, which is a part of the diffeomorphism invariance, is preserved at the quantum level, the loop corrections of the massive field $\chi$ do not disturb the constant evolution of $\zeta$ at super Hubble scales. In this discussion, we show the Ward-Takahashi identity for the scaling symmetry, which yields a consistency relation for the correlation functions of the massive field $\chi$.
We calculate the production rate of singlet fermions from the decay of neutral or charged scalar fields in a hot plasma. We find that there are considerable thermal corrections when the temperature of the plasma exceeds the mass of the decaying scalar. We give analytic expressions for the temperature corrected production rates in the regime where the decay products are relativistic. We also study the regime of non-relativistic decay products numerically. If the scalar is a singlet, then the main correction arises from the fact that the effective mass of the decaying particle is temperature dependent. If the scalar has gauge interactions, then at least one of the decay products must also carry gauge quantum numbers and will be in thermal equilibrium in the early universe. This gives rise to Pauli blocking and a modification of the dispersion relation of these charged particles in the plasma, which affects the kinematics of the decay. Moreover, at high temperature, inelastic scatterings can contribute to the singlet fermion production rate. As a result, the production rate of singlet fermions has a non-trivial temperature dependence. This can affect the abundance and momentum distribution of sterile neutrino Dark Matter that is produced in scalar decays. Our results can be used to improve predictions for the free streaming of the Dark Matter particles, which is crucial to test the compatibility of such scenarios with cosmic structure formation.
We present an analytic model for how momentum deposition from stellar feedback simultaneously regulates star formation and drives outflows in a turbulent interstellar medium (ISM). Because the ISM is turbulent, a given patch of ISM exhibits sub-patches with a range of surface densities. The high-density patches are 'pushed' by feedback, thereby driving turbulence and self-regulating local star formation. Sufficiently low-density patches, however, are accelerated to above the escape velocity before the region can self-adjust and are thus vented as outflows. In the turbulent-pressure-supported regime, when the gas fraction is $\gtrsim 0.3$, the ratio of the turbulent velocity dispersion to the circular velocity is sufficiently high that at any given time, of order half of the ISM has surface density less than the critical value and thus can be blown out on a dynamical time. The resulting outflows have a mass-loading factor ($\eta \equiv M_{\rm out}/M_{\star}$) that is inversely proportional to the gas fraction times the circular velocity. At low gas fractions, the star formation rate needed for local self-regulation, and corresponding turbulent Mach number, decline rapidly; the ISM is 'smoother', and it is actually more difficult to drive winds with large mass-loading factors. Crucially, our model predicts that stellar-feedback-driven outflows should be suppressed at $z \lesssim 1$ in $M_{\star} \gtrsim 10^{10} M_{\odot}$ galaxies. This mechanism allows massive galaxies to exhibit violent outflows at high redshifts and then 'shut down' those outflows at late times, thereby enabling the formation of a smooth, extended thin stellar disk. We provide simple fitting functions for $\eta$ that should be useful for sub-resolution and semi-analytic models. [abridged]
Using a radio-quiet subsample of the Sloan Digital Sky Survey spectroscopic quasar catalog, spanning redshifts 0.5-3.5, we derive the mean millimetre and far-infrared quasar spectral energy densities via a stacking analysis of Atacama Cosmology Telescope and Herschel-SPIRE data. We constrain the form and evolution of the far-infrared emission finding 3-4$\sigma$ evidence for the presence of the thermal Sunyaev-Zel'dovich (SZ) effect in the millimetre bands. We find this signal to be characteristic of a hot ionized gas component with thermal energy $(6.2 \pm 1.7) \times 10^{60}$erg. This amount of thermal energy is an order of magnitude greater than would be expected assuming only hot gas in virial equilibrium with the dark matter haloes of $(1-5)\times 10^{12}h^{-1}$M$_\odot$ that these systems are expected to occupy, though the highest quasar mass estimates found in the literature could explain a large fraction of this energy. We find that our measurements are consistent with a scenario in which quasars deposit up to $(14.5 \pm 3.3)~\tau_8^{-1}$ per cent of their radiative energy into their circumgalactic environment if their typical period of quasar activity is $\tau_8\times 10^8$ years. If quasar host masses are high ($\sim10^{13}h^{-1}$M$_\odot$), then this percentage will be reduced significantly. Furthermore, the uncertainty quoted for this percentage is only statistical and additional systematic uncertainties (e.g., on quasar bolometric luminosity) enter at the 40 per cent level. Finally, emission from thermal dust is significant in these systems, with infrared luminosities of $\log_{10}(L_{\rm ir}/{\rm L}_\odot)=11.4-12.2$, increasing to higher redshift. We consider various models for dust emission. While sufficiently complex dust models can obviate the SZ effect, the SZ interpretation remains favoured at the 3-4$\sigma$ level for most models.
The analysis of galaxy properties and the relations among them and the environment, can be used to investigate the physical processes driving galaxy evolution. We study the cluster A209 by using the CLASH-VLT spectroscopic data combined with Subaru photometry, yielding to 1916 cluster members down to a stellar mass of 10^{8.6} Msun. We determine: i) the stellar mass function of star-forming and passive galaxies; ii) the intra-cluster light and its properties; iii) the orbits of low- and high-mass passive galaxies; and iv) the mass-size relation of ETGs. The stellar mass function of the star-forming galaxies does not depend on the environment, while the slope found for passive galaxies becomes flatter in the densest region. The color distribution of the intra-cluster light is consistent with the color of passive members. The analysis of the dynamical orbits shows that low-mass passive galaxies have tangential orbits, avoiding small pericenters around the BCG. The mass-size relation of low-mass passive ETGs is flatter than that of high mass galaxies, and its slope is consistent with that of field star-forming galaxies. Low-mass galaxies are also more compact within the scale radius of 0.65 Mpc. The ratio between stellar and number density profiles shows a mass segregation in the center. The comparative analysis of the stellar and total density profiles indicates that this effect is due to dynamical friction. Our results are consistent with a scenario in which the "environmental quenching" of low-mass galaxies is due to mechanisms such as harassment out to R200, starvation and ram-pressure stripping at smaller radii, as supported by the analysis of the mass function, of the dynamical orbits and of the mass-size relation of passive early-types in different regions. Our analyses support the idea that the intra-cluster light is formed through the tidal disruption of subgiant galaxies.
When did the universe thermalize? In this talk I review the status of this issue and its importance in establishing the expected properties of dark matter, the growth of large-scale structure, and the viability of inflation models when confronted with CMB observations. I also present a novel approach to tackling the theoretical challenges surrounding inflationary (p)reheating, which seeks to extend past work on the Effective Field Theory of Inflation to the time of reheating.
The dust-content of damped Lyman-alpha systems (DLAs) is an important observable for understanding their origin and the neutral gas reservoirs of galaxies. While the average colour-excess of DLAs, E(B-V), is known to be <15 milli-magnitudes (mmag), both detections and non-detections with ~2 mmag precision have been reported. Here we find 3.2-sigma statistical evidence for DLA dust-reddening of 774 Sloan Digital Sky Survey (SDSS) quasars by comparing their fitted spectral slopes to those of ~7000 control quasars. The corresponding E(B-V) is 3.0 +/- 1.0 mmag, assuming a Small Magellanic Cloud (SMC) dust extinction law, and it correlates strongly (3.5-sigma) with the metal content, characterised by the SiII1526 absorption-line equivalent width, providing additional confidence that the detection is due to dust in the DLAs. Evolution of E(B-V) over the redshift range 2.1 < z < 4.0 is limited to <2.5 mmag per unit redshift (1-sigma), consistent with the known, mild DLA metallicity evolution. There is also no apparent relationship with neutral hydrogen column density, N(HI), though the data are consistent with a mean E(B-V)/N(HI) = (3.5 +/- 1.0) x 10^{-24} mag cm^2, approximately the ratio expected from the SMC scaled to the lower metallicities typical of DLAs. We implement the SDSS selection algorithm in a portable code to assess the potential for systematic, redshift-dependent biases stemming from its magnitude and colour-selection criteria. The effect on the mean E(B-V) is negligible (<5 per cent) over the entire redshift range of interest. Given the broad potential usefulness of this implementation, we make it publicly available.
We describe how monomial chaotic inflation becomes compatible with the latest CMB data thanks to radiative corrections producing a plateau. The interactions of the inflation with other fields, required for reheating, can flatten the potential and moderate the production of primordial gravitational waves, keeping these below the current upper bound. We show that the appearance of a plateau requires that the inflaton couples to fermions and to another scalar or a gauge group. We give concrete examples of minimal particle physics models leading to plateaus for quadratic and quartic chaotic inflation. We also provide a three-parameter model-independent description of radiatively corrected inflation that is amenable to CMB analyses.
The late universe's matter distribution obeys the Copernican principle at only the coarsest of scales. The relative importance of such inhomogeneity is still not well understood. Because of the Einstein field equations' non-linear nature, some argue a non-perturbative approach is necessary to correctly model inhomogeneities and may even obviate any need for dark energy. We shall discuss an approach based on Regge calculus, a discrete approximation to general relativity: we shall discuss the Collins--Williams formulation of Regge calculus and its application to two toy universes. The first is a universe for which the continuum solution is well-established, the $\Lambda$-FLRW universe. The second is an inhomogeneous universe, the `lattice universe' wherein matter consists solely of a lattice of point masses with pure vacuum in between, a distribution more similar to that of the actual universe compared to FLRW universes. We shall discuss both regular lattices and one where one mass gets perturbed.
We present the study of the structure and dynamical status of the galaxy system A523. Our analysis is based on new spectroscopic data for 132 galaxies (TNG), new photometric data (INT), X-ray data (Chandra archive), and radio data (VLA archive). We present the first measures of velocity dispersion of the galaxy population, 949 km/s, and global X-ray temperature of the hot ICM, 5.3 keV. We infer that A523 is a massive system, M200 about 7-9 10E14 Msun. Our analysis of optical data confirms the presence of two subclusters, 0.75 Mpc apart, tracing the SSW-NNE direction, finds that they are (little) separated in velocity, and identifies the two dominant galaxies (BCG1 and BCG2). We show that the X-ray surface brightness is strongly elongated towards the NNE direction, and its peak is clearly offsetted from both the BCGs, and quantify the presence of substructure. We confirm the presence of a 1.3 Mpc large central radio source, its main ESE-WNW elongation perpendicular to the optical/X-ray elongation, and the previous halo classification. We determine a large radio/X-ray peaks offset and detect evidence of polarization, being this detected in only very few radio halos. The radio/X-ray offset and polarization might be the result of having most magnetic field energy on large spatial scales, as shown by our ad hoc simulations. Most properties are consistent with scaling relations followed by other clusters hosting radio halos, but A523 is shown to be peculiar in the Pradio-Lx plane, having a higher radio power or a lower X-ray luminosity than expected. According to main optical and X-ray features, A523 can be described as a binary head--on merger after the primary collision in the SSW-NNE direction. However, both optical and radio data show some evidence in favor of a more complex cluster structure with A523 forming at the cross of two filaments, along SSW-NNE and ESE-WNW directions.
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We present a study of cosmological implications of generic dark matter decays. We consider two-body and many-body decaying scenarios. In the two-body case the massive particle has a possibly relativistic kick velocity and thus possesses a dynamical equation of state. This has implications to the expansion history of the universe. We use recent observational data from the cosmic microwave background, baryon acoustic oscillations and supernovae Type Ia to obtain constraints on the lifetime of the dark matter particle. We find that for an energy splitting where more than 40% of the dark matter particle energy is transferred to massless, relativistic particles in the two-body case, or more than 50% in the many-body case, lifetimes less than the age of the universe are excluded at more than 95% confidence. When the energy splitting falls to 10% the lifetime is constrained to be more than roughly half the age.
Future large-scale galaxy surveys have the potential to become leading probes for cosmology provided the influence of baryons on the total mass distribution is understood well enough. As hydrodynamical simulations strongly depend on details in the feedback implementations, no unique and robust predictions for baryonic effects currently exist. In this paper we propose a baryonic correction model that modifies the density field of dark-matter-only $N$-body simulations to mimic the effects of baryons from any underlying adopted feedback recipe. The model assumes haloes to consist of 4 components: 1- hot gas in hydrostatical equilibrium, 2- ejected gas from feedback processes, 3- central galaxy stars, and 4- adiabatically relaxed dark matter, which all modify the initial dark-matter-only density profiles. This altered mass profiles allow to define a displacement field for particles in $N$-body simulations and to modify the total density field accordingly. The main advantage of the baryonic correction model is to connect the total matter density field to the observable distribution of gas and stars in haloes, making it possible to parametrise baryonic effects on the matter power spectrum. We show that the most crucial quantities are the mass fraction of ejected gas and its corresponding ejection radius. The former controls how strongly baryons suppress the power spectrum, while the latter provides a measure of the scale where baryonic effects become important. A comparison with X-ray and Sunyaev-Zel'dovich cluster observations suggests that baryons suppress wave modes above $k\sim0.5$ h/Mpc with a maximum suppression of 10-25 percent around $k\sim 2$ h/Mpc. More detailed observations of the gas in the outskirts of groups and clusters are required to decrease the large uncertainties of these numbers.
The search for the curl component (B mode) in the cosmic microwave background (CMB) polarization induced by inflationary gravitational waves is described. The canonical single-field slow-roll model of inflation is presented, and we explain the quantum production of primordial density perturbations and gravitational waves. It is shown how these gravitational waves then give rise to polarization in the CMB. We then describe the geometric decomposition of the CMB polarization pattern into a curl-free component (E mode) and curl component (B mode) and show explicitly that gravitational waves induce B modes. We discuss the B modes induced by gravitational lensing and by Galactic foregrounds and show how both are distinguished from those induced by inflationary gravitational waves. Issues involved in the experimental pursuit of these B modes are described, and we summarize some of the strategies being pursued. We close with a brief discussion of some other avenues toward detecting/characterizing the inflationary gravitational-wave background.
We compute the complex 3D Fourier transform of the spatial galaxy distribution in a volume-limited sample of the Sloan Digital Sky Survey redshift survey. The direct unbinned transform yields results quite similar to those from the FFT of finely binned galaxy positions. In both cases the sampling window function is deconvolved to yield an estimate of the true 3D transform. The Fourier amplitudes resulting from this simple procedure yield power spectrum estimates consistent with those from other more complicated approaches. We display also measurements of homogeneity, isotropy and Gaussianity, based on an analysis of the complex Fourier transform that is much simpler than the multi-point methods usually employed. Our model-independent analysis avoids statistical interpretations, which have no meaning without detailed assumptions about a hypothetical process generating the initial cosmic density fluctuations.
The Einstein Equivalence Principle is a fundamental principle of the theory of General Relativity. While this principle has been thoroughly tested with standard matter, the question of its validity in the Dark sector remains open. In this paper, we consider a general tensor-scalar theory that allows to test the equivalence principle in the Dark sector by introducing two different couplings to standard matter and to Dark matter. We constrain these couplings by considering galactic observations of strong lensing and of velocity dispersion. Our analysis shows that, in case of a violation of the Einstein Equivalence Principle, data favour violations through couplings to ordinary and Dark matters of opposite signs. At the same time, General Relativity remains perfectly compatible with observations at a 2-$\sigma$ confidence level.
The thermal Sunyaev-Zel'dovich (tSZ) effect is the inverse-Compton scattering of cosmic microwave background (CMB) photons off hot, ionized electrons, primarily located in galaxy groups and clusters. Recent years have seen immense improvement in our ability to probe cosmology and the astrophysics of the intracluster medium using the tSZ signal. Here, I describe cross-correlations of the tSZ effect measured in Planck data with gravitational lensing maps from Planck and the Canada-France-Hawaii Telescope Lensing Survey, as well as hydrodynamical simulations which show that such measurements do not probe "missing baryons," but rather the pressure of ionized gas in groups and clusters over a wide range of halo masses and redshifts. I also present recent measurements of higher-order tSZ statistics using data from the Atacama Cosmology Telescope, which yield strong constraints on the amplitude of density fluctuations. I describe stacking analyses of tSZ data from Planck, focusing on the behavior of the gas pressure in low-mass galaxy groups. I close with a prediction for the tSZ monopole, including relativistic corrections, which is the largest guaranteed spectral distortion signal for the proposed Primordial Inflation Explorer mission. The tSZ monopole will yield a direct measurement of the total thermal energy in ionized electrons in the observable universe.
We supplement the minimal supersymmetric standard model (MSSM) with vector-like copies of standard model particles. Such 4th generation particles can raise the Higgs boson mass to the observed value without requiring very heavy superpartners, improving naturalness and the prospects for discovering supersymmetry at the LHC. Here we show that these new particles are also motivated cosmologically: in the MSSM, pure Bino dark matter typically overcloses the Universe, but 4th generation particles open up new annihilation channels, allowing Binos to have the correct thermal relic density without resonances or co-annihilation. We show that this can be done in a sizable region of parameter space while preserving gauge coupling unification and satisfying constraints from collider, Higgs, precision electroweak, and flavor physics.
The simplest Higgs-portal dark matter model is studied in the light of dark matter self-interacting effects on the formation of large scale structures. We show the direct detection limits on the resonant and large mass regions. Finally, we also compare these limits with those at the LHC and Xenon 1T experiments.
The possibility that dark matter may be in the form of a Bose-Einstein Condensate (BEC) has been extensively explored at galactic scale. In particular, good fits for the galactic rotations curves have been obtained, and upper limits for the dark matter particle mass and scattering length have been estimated. In the present paper we extend the investigation of the properties of the BEC dark matter to the galactic cluster scale, involving dark matter dominated astrophysical systems formed of thousands of galaxies each. By considering that one of the major components of a galactic cluster, the intra-cluster hot gas, is described by King's $\beta$-model, and that both intra-cluster gas and dark matter are in hydrostatic equilibrium, bound by the same total mass profile, we derive the mass and density profiles of the BEC dark matter. In our analysis we consider several theoretical models, corresponding to isothermal hot gas and zero temperature BEC dark matter, non-isothermal gas and zero temperature dark matter, and isothermal gas and finite temperature BEC, respectively. The properties of the finite temperature BEC dark matter cluster are investigated in detail numerically. We compare our theoretical results with the observational data of 106 galactic clusters. Using a least-squares fitting, as well as the observational results for the dark matter self-interaction cross section, we obtain some upper bounds for the mass and scattering length of the dark matter particle. Our results suggest that the mass of the dark matter particle is of the order of $\mu $eV, while the scattering length has values in the range of $10^{-7}$ fm.
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We use particle data from the Illustris simulation, combined with individual kinematic constraints on the mass of the Milky Way (MW) at specific distances from the Galactic center, to infer the radial distribution of the MW's dark matter halo mass. Our method allows us to convert any constraint on the mass of the MW within a fixed distance to a full circular velocity profile to the MW's virial radius. As primary examples, we take two recent measurements of the total mass within 50 kpc of the Galaxy -- $4.2\times 10^{11}\,M_{\odot}$ (Deason et al. 2012) and $2.9\times 10^{11}\,M_{\odot}$ (Gibbons et al. 2014) -- and find they imply very different mass profiles and stellar masses for the Galaxy. The dark-matter-only version of the Illustris simulation enables us to compute the effects of galaxy formation on such constraints on a halo-by-halo basis; on small scales, galaxy formation enhances the density relative to dark-matter-only runs, while the total mass density is approximately 20% lower at large Galactocentric distances. We are also able to quantify how current and future constraints on the mass of the MW at specific radii will be reflected in uncertainties on its virial mass: even a measurement of M(<50 kpc) with essentially perfect precision still results in a 20% uncertainty on the virial mass of the Galaxy, while a future measurement of M(<100 kpc) with 10% errors would result in the same level of uncertainty. We expect that our technique will become even more useful as (1) better kinematic constraints become available at larger distances and (2) cosmological simulations provide even more faithful representations of the observable Universe.
In light of the growing number of cosmological observations, it is important to develop versatile tools to quantify the constraining power and consistency of cosmological probes. Originally motivated from information theory, we use the relative entropy to compute the information gained by Bayesian updates in units of bits. This measure quantifies both the improvement in precision and the 'surprise', i.e. the tension arising from shifts in central values. Our starting point is a WMAP9 prior which we update with observations of the distance ladder, supernovae (SNe), baryon acoustic oscillations (BAO), and weak lensing as well as the 2015 Planck release. We consider the parameters of the flat $\Lambda$CDM concordance model and some of its extensions which include curvature and Dark Energy equation of state parameter $w$. We find that, relative to WMAP9 and within these model spaces, the probes that have provided the greatest gains are Planck (10 bits), followed by BAO surveys (5.1 bits) and SNe experiments (3.1 bits). The other cosmological probes, including weak lensing (1.7 bits) and $\rm H_0$ measures (1.7 bits), have contributed information but at a lower level. Furthermore, we do not find any significant surprise when updating the constraints of WMAP9 with any of the other experiments, meaning that they are consistent with WMAP9. However, when we choose Planck15 as the prior, we find that the weak lensing measurements of CFHTLenS produce a large surprise of 4.4 bits which is statistically significant at the 8 $\sigma$ level. We discuss how the relative entropy provides a versatile and robust framework to compare cosmological probes in the context of current and future surveys.
We use microwave temperature maps from two seasons of data from the Atacama Cosmology Telescope (ACTPol) at 146 GHz, together with the Constant Mass CMASS galaxy sample from the Baryon Oscillation Spectroscopic Survey to measure the kinematic Sunyaev-Ze\v{l}dovich (kSZ) effect over the redshift range z = 0.4 - 0.7. We use galaxy positions and the continuity equation to obtain a reconstruction of the line-of-sight velocity field. We stack the cosmic microwave background temperature at the location of each halo, weighted by the corresponding reconstructed velocity. The resulting best fit kSZ model is preferred over the no-kSZ hypothesis at 3.3sigma and 2.9sigma for two independent velocity reconstruction methods, using 25,537 galaxies over 660 square degrees. The effect of foregrounds that are uncorrelated with the galaxy velocities is expected to be well below our signal, and residual thermal Sunyaev-Ze\v{l}dovich contamination is controlled by masking the most massive clusters. Finally, we discuss the systematics involved in converting our measurement of the kSZ amplitude into the mean free electron fraction of the halos in our sample.
We present the results of the quest for ring-type structures on the maps observed by the Planck satellite.
Precision measurements of the large scale structure of the Universe require large numbers of high fidelity mock catalogs to accurately assess, and account for, the presence of systematic effects. We introduce and test a scheme for generating mock catalogs rapidly using suitably derated N-body simulations. Our aim is to reproduce the large scale structure and the gross properties of dark matter halos with high accuracy, while sacrificing the details of the internal structure of the halos. By adjusting global and local time-steps in an N-body code, we demonstrate that we recover halo masses to better than 2% and the power spectrum (both in real and redshift space, for k = 1h/Mpc) to better than 1%, while requiring a factor of 4 less CPU time. We also calibrate the redshift spacing of outputs required to generate simulated light cones. We find that outputs separated by every z = 0.05 allow us to interpolate particle positions and velocities to reproduce the real and redshift space power spectra to better than 1% (out to k = 1h/Mpc). We apply these ideas to generate a suite of simulations spanning a range of cosmologies, motivated by the Baryon Oscillation Spectroscopic Survey (BOSS) but broadly applicable to future large scale structure surveys including eBOSS and DESI. As an initial demonstration of the utility of such simulations, we calibrate the shift in the baryonic acoustic oscillation peak position as a function of galaxy bias with higher precision than has been possible so far. This paper also serves to document the simulations, which we make publicly available.
NIKA, the prototype of the NIKA2 camera, is an instrument operating at the IRAM 30m telescope that can observe the sky simultaneously at 150 and 260GHz. One of the main goals of NIKA is to measure the pressure distribution in galaxy clusters at high angular resolution using the Sunyaev-Zel'dovich (SZ) effect. Such observations have already proved to be an excellent probe of cluster pressure distributions even at high redshifts. However, an important fraction of clusters host submm and/or radio point sources that can significantly affect the reconstructed signal. Here we report <20arcsec angular resolution observations at 150 and 260GHz of the cluster MACSJ1424, which hosts both radio and submm point sources. We examine the morphological distribution of the SZ signal and compare it to other datasets. The NIKA data are combined with Herschel satellite data to study the SED of the submm point source contaminants. We then perform a joint reconstruction of the ICM electronic pressure and density by combining NIKA, Planck, XMM-Newton and Chandra data, focussing on the impact of the radio and submm sources on the reconstructed pressure profile. We find that the large-scale pressure distribution is unaffected by the point sources due to the resolved nature of the NIKA observations. The reconstructed pressure in the inner region is slightly higher when the contribution of point sources are removed. We show that it is not possible to set strong constraints on the central pressure distribution without removing accurately these contaminants. The comparison with Xray only data shows good agreement for the pressure, temperature and entropy profiles, all indicating that MACSJ1424 is a dynamically relaxed cool core system. The present observations illustrate the possibility of measuring these quantities with a relatively small integration time, even at high redshift and without Xray spectroscopy.
We conduct precise strong lensing mass modeling of four ${\it Hubble}$ Frontier Fields (HFF) clusters, Abell$~$2744, MACS$~$J0416.1$-$2403, MACS$~$J0717.5$+$3745, and MACS$~$J1149.6$+$2223, for which HFF imaging observations are completed. We construct a refined sample of more than 100 multiple images for each cluster by taking advantage of the full depth HFF images, and conduct mass modeling using the ${\small \rm GLAFIC}$ software, which assumes simply parametrized mass distributions. Our mass modeling also exploits a magnification constraint from the lensed Type Ia supernova HFF14Tom for Abell$~$2744 and positional constraints from multiple images of the lensed supernova SN Refsdal for MACS$~$J1149.6$+$2223. We find that our best-fitting mass models reproduce the observed image positions with RMS errors of $\sim 0.4$ arcsec, which are smaller than RMS errors in previous mass modeling that adopted similar numbers of multiple images. We then construct catalogs of $z\sim 6-9$ dropout galaxies behind the four clusters and estimate magnification factors for these dropout galaxies with our best-fitting mass models. The dropout sample from the four cluster fields contains $\sim 120$ galaxies at $z\gtrsim 6$, about 20 of which are predicted to be magnified by a factor of more than 10. Some of the high-redshift galaxies detected in the HFF have lensing-corrected magnitudes of $M_{\rm UV}\sim -15$ to $-14$. Our analysis demonstrates that the HFF data indeed offer an ideal opportunity to study faint high-redshift galaxies. All lensing maps produced from our mass modeling will be made available on the STScI website.
We present a new exploratory framework to model galaxy formation and evolution in a hierarchical universe by using machine learning (ML). Our motivations are two-fold: (1) presenting a new, promising technique to study galaxy formation, and (2) quantitatively analyzing the extent of the influence of dark matter halo properties on galaxies in the backdrop of semi-analytical models (SAMs). We use the influential Millennium Simulation and the corresponding Munich SAM to train and test various sophisticated machine learning algorithms (k-Nearest Neighbors, decision trees, random forests and extremely randomized trees). By using only essential dark matter halo physical properties for haloes of $M>10^{12} M_{\odot}$ and a partial merger tree, our model predicts the hot gas mass, cold gas mass, bulge mass, total stellar mass, black hole mass and cooling radius at z = 0 for each central galaxy in a dark matter halo for the Millennium run. Our results provide a unique and powerful phenomenological framework to explore the galaxy-halo connection that is built upon SAMs and demonstrably place ML as a promising and a computationally efficient tool to study small-scale structure formation.
We use cosmological simulations from the Feedback In Realistic Environments (FIRE) project, which implement a comprehensive set of stellar feedback processes, to study ultra-violet (UV) metal line emission from the circum-galactic medium of high-redshift (z = 2-4) galaxies. Our simulations cover the halo mass range Mh~2x10^11 - 8.5x10^12 Msun at z = 2, representative of Lyman break galaxies. Of the transitions we analyze, the low-ionization C III (977 A) and Si III (1207 A) emission lines are the most luminous, with C IV (1548 A) and Si IV (1394 A) also showing interesting spatially-extended structures that should be detectable by current and upcoming integral field spectrographs such as the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope and Keck Cosmic Web Imager (KCWI). The more massive halos are on average more UV-luminous. The UV metal line emission from galactic halos in our simulations arises primarily from collisionally ionized gas and is strongly time variable, with peak-to-trough variations of up to ~2 dex. The peaks of UV metal line luminosity correspond closely to massive and energetic mass outflow events, which follow bursts of star formation and inject sufficient energy into galactic halos to power the metal line emission. The strong time variability implies that even some relatively low-mass halos may be detectable in deep observations with current generation instruments. Conversely, flux-limited samples will be biased toward halos whose central galaxy has recently experienced a strong burst of star formation.
The Next-Generation Very Large Array (ngVLA) will be critical for understanding how galaxies are built and evolve at the earliest epochs. The sensitivity and frequency coverage will allow for the detection of cold gas and dust in `normal' distant galaxies, including the low-J transitions of molecular gas tracers such as CO, HNC, and HCO+; synchrotron and free-free continuum emission; and even the exciting possibility of thermal dust emission at the highest (z~7) redshifts. In particular, by enabling the total molecular gas reservoirs to be traced to unprecedented sensitivities across a huge range of epochs simultaneously -- something no other radio or submillimeter facility will be capable of -- the detection of the crucial low-J transitions of CO in a diverse body of galaxies will be the cornerstone of ngVLA's contribution to high-redshift galaxy evolution science. The ultra-wide bandwidths will allow a complete sampling of radio SEDs, as well as the detection of emission lines necessary for spectroscopic confirmation of elusive dusty starbursts. The ngVLA will also deliver unique contributions to our understanding of cosmic magnetism and to science accessible through microwave polarimetry. Finally, the superb angular resolution will move the field beyond detection experiments and allow detailed studies of the morphology and dynamics of these systems, including dynamical modeling of disks/mergers, determining the properties of outflows, measuring black hole masses from gas disks, and resolving multiple AGN nuclei. We explore the contribution of a ngVLA to these areas and more, as well as synergies with current and upcoming facilities including ALMA, SKA, large single-dish submillimeter observatories, GMT/TMT, and JWST.
The absence of low energy supersymmetry in run I data at the LHC has pushed the nominal scale for supersymmetry beyond a TeV. While this is consistent with the discovery of the Higgs boson at \approx 125 GeV, simple models with scalar and gaugino mass universality are being pushed into corners of parameter space. Some possibilities within the constrained minimal supersymmetric extension of the standard model (with four parameters) are discussed along with a one parameter extension in which the Higgs soft masses are non-universal. Also discussed are 2-, 3-, and 4-parameter versions of pure gravity mediated models with a wino, Higgsino, or bino LSP respectively.
We incorporate Milky Way dark matter halo profile uncertainties, as well as an accounting of diffuse gamma-ray emission uncertainties in dark matter annihilation models for the Galactic Center Extended gamma-ray excess (GCE) detected by the Fermi Gamma Ray Space Telescope. The range of particle annihilation rate and masses expand when including these unknowns. However, empirical determinations of the Milky Way halo's local density and density profile leave the signal region to be in considerable tension with dark matter annihilation searches from combined dwarf galaxy analyses. Extreme changes to the Milky Way halo, which may be possible in cases of extreme adiabatic contraction, must be adopted to escape these constraints in a dark matter annihilation model for the GCE. Dark matter annihilation models that produce the gamma-ray excess via differential mechanisms in the GCE and dwarfs may circumvent this tension.
We report here on key science topics for the Next Generation Very Large Array in the areas of time domain, fundamental physics, and cosmology. Key science cases considered are pulsars in orbit around the Galactic Center massive black hole, Sagittarius A*, electromagnetic counterparts to gravitational waves, and astrometric cosmology. These areas all have the potential for ground-breaking and transformative discovery. Numerous other topics were discussed during the preparation of this report and some of those discussions are summarized here, as well. There is no doubt that further investigation of the science case will reveal rich and compelling opportunities.
Although QCD axion models are widely studied as solutions to the strong CP problem, they generically confront severe fine-tuning problems to guarantee the anomalous PQ symmetry. In this letter, we propose a simple QCD axion model without any fine-tunings. We introduce an extra dimension and a pair of extra quarks living on two branes separately, which is also charged under a bulk Abelian gauge symmetry. We assume a monopole condensation on our brane at an intermediate scale, which implies that the extra quarks develop the chiral symmetry breaking and the PQ symmetry is broken. In contrast to the original Kim's model, our model explains the origin of the PQ symmetry thanks to the extra dimension and avoids the cosmological domain wall problem because of the chiral symmetry breaking in the Abelian gauge theory.
The formalism to treat quantization and evolution of cosmological perturbations of multiple fluids is described. We first construct the Lagrangian for both the gravitational and matter parts, providing the necessary relevant variables and momenta leading to the quadratic Hamiltonian describing linear perturbations. The final Hamiltonian is obtained without assuming any equations of motions for the background variables. This general formalism is applied to the special case of two fluids, having in mind the usual radiation and matter mix which made most of our current Universe history. Quantization is achieved using an adiabatic expansion of the basis functions. This allows for an unambiguous definition of a vacuum state up to the given adiabatic order. Using this basis, we show that particle creation is well defined for a suitable choice of vacuum and canonical variables, so that the time evolution of the corresponding quantum fields is unitary. This provides constraints for setting initial conditions for an arbitrary number of fluids and background time evolution. We also show that the common choice of variables for quantization can lead to an ill-defined vacuum definition. Our formalism is not restricted to the case where the coupling between fields is small, but is only required to vary adiabatically with respect to the ultraviolet modes, thus paving the way to consistent descriptions of general models not restricted to single-field (or fluid).
We study a level crossing between the QCD axion and an axion-like particle, focusing on the recently found phenomenon, the axion roulette, where the axion-like particle runs along the potential, passing through many crests and troughs, until it gets trapped in one of the potential minima. We perform detailed numerical calculations to determine the parameter space where the axion roulette takes place, and as a result domain walls are likely formed. The domain wall network without cosmic strings is practically stable, and it is nothing but a cosmological disaster. In a certain case, one can make domain walls unstable and decay quickly by introducing an energy bias without spoiling the Peccei-Quinn solution to the strong CP problem.
We consider the construction of gauge theories of gravity, focussing in particular on the extension of local Poincar\'e invariance to include invariance under local changes of scale. We work exclusively in terms of finite transformations, which allow for a more transparent interpretation of such theories in terms of gauge fields in Minkowski spacetime. Our approach therefore differs from the usual geometrical description of locally scale-invariant Poincar\'e gauge theory (PGT) and Weyl gauge theory (WGT) in terms of Riemann--Cartan and Weyl--Cartan spacetimes, respectively. In particular, we reconsider the interpretation of the Einstein gauge and also the equations of motion of matter fields and test particles in these theories. Inspired by the observation that the PGT and WGT matter actions for the Dirac field and electromagnetic field have more general invariance properties than those imposed by construction, we go on to present a novel alternative to WGT by considering an `extended' form for the transformation law of the rotational gauge field under local dilations, which includes its `normal' transformation law in WGT as a special case. The resulting `extended' Weyl gauge theory (eWGT) has a number of interesting features that we describe in detail. In particular, we present a new scale-invariant gauge theory of gravity that accommodates ordinary matter and is defined by the most general parity-invariant eWGT Lagrangian that is at most quadratic in the eWGT field strengths, and we derive its field equations. We also consider the construction of PGTs that are invariant under local dilations assuming either the `normal' or `extended' transformation law for the rotational gauge field, but show that they are special cases of WGT and eWGT, respectively.
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