Observations of the extragalactic radio background have uncovered a significant isotropic emission across multiple frequencies spanning from 22 MHz to 10 GHz. The intensity of this non-thermal emission component significantly exceeds the expected contribution from known astrophysical sources. Interestingly, models have indicated that the annihilation of dark matter particles may reproduce both the flux and spectrum of the excess. However, the lack of a measurable anisotropy in the residual emission remains challenging for both dark matter and standard astrophysical interpretations of the ARCADE-2 data. We calculate the expected synchrotron anisotropy from dark matter annihilation and show that these models can produce very small anisotropies, though this requires galaxy clusters to have large substructure contributions and strong magnetic fields. We show that this constraint can be significantly relaxed, however, in scenarios where electrons produced via dark matter annihilation can be efficiently reaccelerated by Alfv\'en waves in the intra-Cluster medium. Our analysis indicates that any source capable of explaining the intensity and isotropy of the extragalactic radio excess must have a spatial extension far larger than typical for baryons in galaxies, suggesting a novel physics interpretation.
The Bullet Cluster ($1\mathrm{E}0657\mathrm{-}56 $) is well-known as providing visual evidence of dark matter but it is potentially inconsistent with the standard $\Lambda$CDM cosmology due to the high relative velocity of the two colliding clusters. Previous studies have focussed on the probability of such a high relative velocity amongst selected candidate systems. This notion of `probability' is however difficult to interpret and can lead to paradoxical results. Instead, we consider the expected number of Bullet-like systems on the sky up to a specified redshift, which allows for direct comparison with observations. Using a Hubble volume N-body simulation with high resolution we investigate how the number of such systems depends on the masses of the halo pairs, their separation, and collisional angle. This enables us to extract an approximate formula for the expected number of halo-halo collisions given specific collisional parameters. We use extreme value statistics to analyse the tail of the pairwise velocity distribution and demonstrate that it is fatter than the previously assumed Gaussian form. We estimate that the number of dark matter halo pairs as or more extreme than $1\mathrm{E}0657\mathrm{-}56 $ is $1.3^{+2.0}_{-0.6}$ up to redshift $z=0.3$. The discovery of more such systems would thus be a challenge to the standard cosmology.
We present a comparison of major methodologies of fast generating mock halo or galaxy catalogues. The comparison is done for two-point and the three-point clustering statistics. The reference catalogues are drawn from the BigMultiDark N-body simulation. Both friend-of-friends (including distinct halos only) and spherical overdensity (including distinct halos and subhalos) catalogs have been used with the typical number density of a large-volume galaxy surveys. We demonstrate that a proper biasing model is essential for reproducing the power spectrum at quasilinear and even smaller scales. With respect to various clustering statistics a methodology based on perturbation theory and a realistic biasing model leads to very good agreement with N-body simulations. However, for the quadrupole of the correlation function or the power spectrum, only the method based on semi-N-body simulation could reach high accuracy (1% level) at small scales, i.e., r<25 Mpc/h or k>0.15 h/Mpc. For those methods that only produce distinct haloes, a halo occupation distribution (HOD) scheme is applied to generate substructures. We find however, that it is not trivial to reproduce the clustering properties of the reference SO catalogue that include both distinct haloes and subhaloes with high accuracy. Full N-body solutions will remain indispensable to produce reference catalogues. Nevertheless, we have demonstrated that the far more efficient approximate solvers can reach a few percent accuracy in terms of clustering statistics at the scales interesting for the large-scale structure analysis after calibration with a few reference N-body calculations. This makes them useful for massive production aimed at covariance studies, to scan large parameter spaces, and to estimate uncertainties in data analysis techniques, such as baryon acoustic oscillation reconstruction, redshift distortion measurements, etc.
We study chromo-natural inflation in the axiverse. More precisely, we investigate natural inflation with two axions coupled with a SU(2) gauge field. Assuming a hierarchy between the coupling constants, we find that for certain initial conditions, conventional natural inflation commences and continues for tens of e-foldings, and subsequently chromo-natural inflation takes over from natural inflation. For these solutions, we expect that the predictions are in agreement with observations on CMB scales. Moreover, since chromo-natural inflation occurs in the latter part of the inflationary stage, chiral primordial gravitational waves are produced in the interesting frequency range higher than $10^{-10}$Hz, which might be detectable by future gravitational wave observations.
It has been shown that the gamma-ray flux observed by HESS from the J1745-290 Galactic Center source is well fitted as the secondary gamma-rays photons generated from Dark Matter annihilating into Standard Model particles in combination with a simple power law background. The neutrino flux expected from such Dark Matter source has been also analyzed. The main results of such analyses for 50 TeV Dark Matter annihilating into W+W- gauge boson and preliminary results for antiprotons are presented.
Using a state-of-the-art semi analytic model (SAM) for galaxy formation, we have investigated the statistical effects of assuming two different mechanisms for triggering AGN activity on the properties of AGN host galaxies. We have considered a first accretion mode where AGN activity is triggered by disk instabilities (DI) in isolated galaxies, and a second feeding mode where such an activity is triggered by galaxy mergers and fly-by events (interactions, IT). We obtained the following results:i) for hosts with $M_* \lesssim 10^{11} M_{\bigodot}$, both DI and IT modes are able to account for the observed AGN hosts stellar mass function; for more massive hosts, the DI scenario predicts a lower space density than the IT model, lying below the observational estimates for z>0.8.ii) The analysis of the color-magnitude diagram (CMD) of AGN hosts for redshift z < 1.5 can provide a good observational test to effectively discriminate between the DI and IT mode, since DIs are expected to yield AGN host galaxy colors skewed towards bluer colors, while in the IT scenario the majority of hosts are expected to reside in the red sequence.iii) While both IT and DI scenarios can account for AGN triggered in main sequence or starburst galaxies, DIs fail in triggering AGN activity in passive galaxies.iv) The two modes are characterized by a different duration of the AGN phase, with DIs lasting even on time scales $\sim $ Gyr, much longer with respect to the IT scenario.v) The scatter of the $SFR-L_{bol}$ relation could represent another crucial diagnostics to discriminate between the two triggering modes, since the DI scenario predicts an appreciably lower scatter of the relation than the IT scenario. vi) Disk instabilities are not able to account for the observed fraction of AGN in groups for z < 1 and clusters for z < 0.7, while the IT scenario provides a good match to observational data.
We show that a neutral scalar field, \sigma, of two Higgs doublet extensions of the Standard Model incorporating the seesaw mechanism for neutrino masses can be identified as a consistent {\it warm} dark matter candidate with a mass of order keV. The relic density of $\sigma$ is correctly reproduced by virtue of the late decay of a right-handed neutrino N participating in the seesaw mechanism. Constraints from cosmology determine the mass and lifetime of N to be M_N = 25 GeV - 20 TeV and \tau_N = (10^{-4} - 1) sec. These models can also explain the 3.5 keV X-ray anomaly in the extra-galactic spectrum that has been recently reported in terms of the decay \sigma \to \gamma \gamma. Future tests of these models at colliders and in astrophysical settings are outlined.
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We report Karl G. Jansky Very Large Array (VLA) absorption spectroscopy in four methanol (CH$_3$OH) lines in the $z = 0.88582$ gravitational lens towards PKS1830-211. Three of the four lines have very different sensitivity coefficients $K_\mu$ to changes in the proton-electron mass ratio $\mu$; a comparison between the line redshifts thus allows us to test for temporal evolution in $\mu$. We obtain a stringent statistical constraint on changes in $\mu$ by comparing the redshifted 12.179 GHz and 60.531 GHz lines, $[\Delta mu/\mu] \leq 1.1 \times 10^{-7}$ ($2\sigma$) over $0 < z \leq 0.88582$, a factor of $\approx 2.5$ more sensitive than the best earlier results. However, the higher signal-to-noise ratio (by a factor of $\approx 2$) of the VLA spectrum in the 12.179 GHz transition also indicates that this line has a different shape from that of the other three CH$_3$OH lines (at $> 4\sigma$ significance). The sensitivity of the above result, and that of all earlier CH$_3$OH studies, is thus likely to be limited by unknown systematic errors, probably arising due to the frequency-dependent structure of PKS1830-211. A robust result is obtained by combining the three lines at similar frequencies, 48.372, 48.377 and 60.531 GHz, whose line profiles are found to be in good agreement. This yields the $2\sigma$ constraint $[\Delta \mu/\mu] \lesssim 4 \times 10^{-7}$, the most stringent current constraint on changes in $\mu$. We thus find no evidence for changes in the proton-electron mass ratio over a lookback time of $\approx 7.5$ Gyrs.
SARAS is a correlation spectrometer connected to a frequency independent antenna that is purpose-designed for precision measurements of the radio background at long wavelengths. The design, calibration and observing strategies admit solutions for the internal additive contributions to the radiometer response, and hence a separation of these contaminants from the antenna temperature. We present here a wideband measurement of the radio sky spectrum by SARAS that provides an accurate measurement of the absolute brightness and spectral index between 110 and 175 MHz. Accuracy in the measurement of absolute sky brightness is limited by systematic errors of magnitude 1.2%; errors in calibration and in the joint estimation of sky and system model parameters are relatively smaller. We use this wide-angle measurement of the sky brightness using the precision wide-band dipole antenna to provide an improved absolute calibration for the 150-MHz all-sky map of Landecker & Wielebinski (1970):subtracting an offset of 21.4 K and scaling by factor 1.05 will reduce the overall offset error to 8 K (from 50 K) and scale error to 0.8% (from 5%). The SARAS measurement of the temperature spectral index is in the range -2.3 to -2.45 in the 110 to 175 MHz band and indicates that the region towards the Galactic bulge has a relatively flatter index.
We report the results of the first study of the multi-stream environment of dark matter halos in cosmological N-body simulations in the Lambda-CDM cosmology. The full dynamical state of dark matter can be described as a three-dimensional submanifold in six-dimensional phase space - the dark matter sheet. In our study we use a Lagrangian submanifold x = x (q,t) (where x and q are comoving Eulerian and Lagrangian coordinates respectively), which is dynamically equivalent to the dark matter sheet but is more convenient for numerical analysis. Its convenience is two-fold. Firstly, x is a single-valued function of q at any stage including highly non-linear stages while the phase space sheet in any set of three of six phase space axes is not. And secondly, storing the Lagrangian submanifold does not require additional space for Lagrangian coordinates if the uniform state of the simulation is represented by a uniform three-dimensional mesh. Our major results can be summarized as follows: At the resolution of the simulation i.e. without additional smoothing the cosmic web represents a hierarchical structure: each halo is embedded in the filamentary framework of the web at the filament crossings, and each filament is embedded in the wall like fabric of the web at the wall crossings. Locally, the halos are the regions of highest number of streams, the number of streams in the neighboring filaments is higher than in the neighboring walls, and walls are regions where number of streams is greater or equal to three. Voids are uniquely defined by the local condition requiring to be a single-stream flow region. The shells of streams around halos are quite thin and the closest void region is typically within roughly one and a half of FOF radii of the halo.
We study the stellar, Brightest Cluster Galaxy (BCG) and intracluster medium
(ICM) masses of 14 South Pole Telescope (SPT) selected galaxy clusters with
median redshift $z=0.9$ and median mass $M_{500}=6\times10^{14}M_{\odot}$. We
estimate stellar masses for each cluster and BCG using six photometric bands
spanning the range from the ultraviolet to the near-infrared observed with the
VLT, HST and Spitzer. The ICM masses are derived from Chandra and XMM-Newton
X-ray observations, and the virial masses are derived from the SPT
Sunyaev-Zel'dovich Effect signature.
At $z=0.9$ the BCG mass $M_{\star}^{\textrm{BCG}}$ constitutes $0.12\pm0.01$%
of the halo mass for a $6\times10^{14}M_{\odot}$ cluster, and this fraction
falls as $M_{500}^{-0.58\pm0.07}$. The cluster stellar mass function has a
characteristic mass $M_{0}=10^{11.0\pm0.1}M_{\odot}$, and the number of
galaxies per unit mass in clusters is larger than in the field by a factor
$1.65\pm0.2$. Both results are consistent with measurements on group scales and
at lower redshift. We combine our SPT sample with previously published samples
at low redshift that we correct to a common initial mass function and for
systematic differences in virial masses. We then explore mass and redshift
trends in the stellar fraction (fstar), the ICM fraction (fICM), the cold
baryon fraction (fc) and the baryon fraction (fb). At a pivot mass of
$6\times10^{14}M_{\odot}$ and redshift $z=0.9$, the characteristic values are
fstar=$1.1\pm0.1$%, fICM=$9.6\pm0.5$%, fc=$10.4\pm1.2$% and fb=$10.7\pm0.6$%.
These fractions all vary with cluster mass at high significance, indicating
that higher mass clusters have lower fstar and fc and higher fICM and fb. When
accounting for a 15% systematic virial mass uncertainty, there is no
statistically significant redshift trend at fixed mass in these baryon
fractions.
(abridged)
The delayed cosmology [JCAP 02(2012)046] assumes that the evolution of geometries is delayed relative to that of matter and/or energies. This idea allows inflation to occur without inflaton fields or vacuum energies of any kind as drivings. We considered the production and evolution of primordial perturbations in this model. The result indicate that, with delaying, we could get a nearly scale-free power spectrum of perturbations starting from a radiation dominated early universe.
New severe constraints on the variation of the fine structure constant have been obtained from reactor Oklo analysis in our previous work. We investigate here how these constraints confine the parameter of BSBM model of varying $\alpha$. Integrating the coupled system of equations from the Big Bang up to the present time and taking into account the Oklo limits we have obtained the following margin on the combination of the parameters of BSBM model: $$ |\zeta_m (\frac{l}{l_{pl}})^2|<6\cdot 10^{-7}, $$ where $l_{pl}=(\frac{G\hbar}{c^3})^{\frac{1}{2}} \approx 1.6 \cdot 10^{-33}$ cm is a Plank length and $l$ is the characteristic length of the BSBM model. The natural value of the parameter $\zeta_m$ - the fraction of electromagnetic energy in matter - is about $10^{-4}$. As a result it is followed from our analysis that the characteristic length $l$ of BSBM theory should be considerably smaller than the Plank length to fulfill the Oklo constraints on $\alpha$ variation.
An essential quantity required to understand the physics of the early Universe, in particular the inflationary epoch, is the primordial scalar potential $\Phi$ and its statistics. We present for the first time an all-sky reconstruction of $\Phi$ with corresponding $1\sigma$-uncertainty from WMAP's cosmic microwave background (CMB) temperature data - a map of the very early Universe right after the inflationary epoch. This has been achieved by applying a Bayesian inference method that separates the whole inverse problem of the reconstruction into many independent ones, each of them solved by an optimal linear filter (Wiener filter). In this way, the three-dimensional potential $\Phi$ gets reconstructed slice by slice resulting in a thick shell of nested spheres around the comoving distance to the last scattering surface. Each slice represents the primordial scalar potential $\Phi$ projected onto a sphere with corresponding distance. Furthermore, we present an advanced method for inferring $\Phi$ and its power spectrum simultaneously from data, but argue that applying it requires polarization data with high signal-to-noise levels not available yet. Future CMB data should improve results significantly, as polarization data will fill the present $\ell-$blind gaps of the reconstruction.
We discuss the universality and self-similarity of void density profiles, for voids in realistic mock luminous red galaxy (LRG) catalogues from the Jubilee simulation, as well as in void catalogues constructed from the SDSS LRG and Main Galaxy samples. Voids are identified using a modified version of the ZOBOV watershed transform algorithm, with additional selection cuts. We find that voids in simulation are self-similar, meaning that their average rescaled profile does not depend on the void size, or -- within the range of the simulated catalogue -- on the redshift. Comparison of the profiles obtained from simulated and real voids shows an excellent match. The profiles of real voids also show a universal behaviour over a wide range of galaxy luminosities, number densities and redshifts. This points to a fundamental property of the voids found by the watershed algorithm, which can be exploited in future studies of voids.
This article looks at the combined constraints from a photometric and spectroscopic survey. These surveys will measure cosmology using weak lensing (WL), galaxy cluster- ing, baryon acoustic oscillations (BAO) and redshift space distortions (RSD). We find, contrary to some findings in the recent literature, that overlapping surveys can give important benefits when measuring dark energy. We therefore try to clarify the status of this issue with a full forecast of two stage-IV surveys using a new approach to prop- erly account for covariance between the different probes in the overlapping samples. The benefit of the overlapping survey can be traced back to two factors: additional observables and sample variance cancellation. Both needs to be taken into account and contribute equally when combining 3D power spectrum and 2D correlations for lensing. With an analytic example we also illustrate that for optimal constraints, one should minimize the (Pearson) correlation coefficient between cosmological and nui- sance parameters and maximize the one among nuisance parameters (e.g. galaxy bias) in the two samples. This can be achieved by increasing the overlap between the spec- troscopic and photometric surveys. We show how BAO, WL and RSD contribute to this benefit also look at some other survey designs, such as photometric redshift errors and spectroscopic density.
Groups and clusters of galaxies show a universal, nearly linear entropy radial profile $K(r)$. Using deprojected 13 clusters and 9 groups from the literature, we find that $K(r)\propto r^{0.97\pm0.01}$, consistent with the mean power-law index $\sim(0.9-1.1)$ of previous studies. An equally good fit to the data is given by a $(t_{cool}/t_{ff})\propto r^{0.73\pm0.01}$ ratio between cooling and free-fall times. Both profiles slightly flatten at small radii, as $(t_{cool}/t_{ff})$ becomes of order unity. The entropy profile is usually attributed to the primordial gas crossing the virial shock, to non-standard heat conduction, or to turbulent heating. We argue that a dynamical mechanism is needed to sustain such a simple profile, oblivious to the temperature peak at the edge of the core and to the virial shock at the outskirts, and robust to the presence of ongoing cooling, merger, and AGN activity. In particular, we show that such a profile is naturally obtained in a spiral flow, which is likely to exist in most galaxy aggregates according to the ubiquitous spiral patterns and cold fronts observed. A generalized Schwarzschild criterion shows that the spiral structure observed must involve a convective layer, which may regulate the universal profile. A generalized two-phase model of a spiral flow extending out to the virial radius is presented.
At low redshifts, deviations of the measured luminosity distance from the background FRW universe can be attributed to peculiar velocities of galaxies. Via observing the cosmic standard candles, this is one of the conventional ways to estimate peculiar velocities. However, at intermediate redshifts ($z > 0.5$), deviations from the background FRW model are not uniquely governed by peculiar velocities. Luminosity distances are modified by gravitational lensing which affects the light trajectories. Hence using the conventional peculiar velocity method will result in an overestimate of the measured peculiar velocities at intermediate redshifts. Here we quantify this effect and show that although present data are still incapable of extracting any lensing effect on distance measurement and peculiar velocity estimation, this effect will however be significant for future large-scale structure surveys.
Laser and maser interferometry have proven to be extremely sensitive techniques in searches for exotic new physics, including searches for the aether, tests of Lorentz symmetry and gravitational wave detection. We propose several new uses of laser and maser interferometry for investigating fundamental physics. Any slight variations in the fundamental constants of Nature, which may be induced by dark matter or some yet-to-be-discovered cosmic field, would characteristically alter the phase of a light beam inside an interferometer, which can be measured extremely precisely. Laser and maser interferometry may be applied to searches for the linear-in-time drift of the fundamental constants, detection of topological defect dark matter through transient-in-time effects and for a relic, coherently oscillating condensate, which consists of scalar dark matter fields, through oscillating effects. Our proposed experiments offer sensitivity to variation of the fundamental constants at the fractional level $\sim 10^{-21}$, based on already existing technology.
The mechanism of thermal inflation, a relatively short period of accelerated expansion after primordial inflation, is a desirable ingredient for a certain class of particle physics models if they are not to be in contention with the cosmology of the early Universe. Though thermal inflation is most simply described in terms of a thermal effective potential, a thermal environment also gives rise to thermal fluctuations that must be taken into account. We numerically study the effects of these thermal fluctuations using lattice simulations. We conclude that though they do not ruin the thermal inflation scenario, the phase transition at the end of thermal inflation proceeds through phase mixing and is therefore not accompanied by the formations of bubbles nor appreciable amplitude of gravitational waves.
The subsonic expansion of bubbles in a strongly first-order electroweak phase transition is a convenient scenario for electroweak baryogenesis. For most extensions of the Standard Model, stationary subsonic solutions (i.e., deflagrations) exist for the propagation of phase transition fronts. However, deflagrations are known to be hydrodynamically unstable for wall velocities below a certain critical value. We calculate this critical velocity for several extensions of the Standard Model and compare with an estimation of the wall velocity. In general, we find a region in parameter space which gives stable deflagrations as well as favorable conditions for electroweak baryogenesis.
The gravitational waveforms in the ghost-free bi-gravity theory exhibit deviations from those in general relativity. The main difference is caused by graviton oscillations in the bi-gravity theory. We investigate the prospects for the detection of the corrections to gravitational waveforms from coalescing compact binaries due to graviton oscillations and for constraining bi-gravity parameters with the gravitational wave observations. We consider the bi-gravity model discussed by the De Felice-Nakamura-Tanaka subset of the bi-gravity model, and the phenomenological model in which the bi-gravity parameters are treated as independent variables. In both models, the bi-gravity waveform shows strong amplitude modulation, and there can be a characteristic frequency of the largest peak of the amplitude, which depends on the bi-gravity parameters. We show that there is a detectable region of the bi-gravity parameters for the advanced ground-based laser interferometers, such as Advanced LIGO, Advanced Virgo, and KAGRA. This region corresponds to the effective graviton mass of mu>10^{-17} cm^{-1} for tilde{c}-1>10^{-19} in the phenomenological model, while mu>10^{-16.5} cm^{-1} for kappa xi_c^2 > 10^{0.5} in the De Felice-Nakamura-Tanaka subset of the bi-gravity model, respectively, where tilde{c} is the propagation speed of the massive graviton and kappa xi_c^2 corresponds to the corrections to the gravitational constant in general relativity. These regions are not excluded by existing solar system tests. We also show that, in the case of 1.4M_{sun}-1.4M_{sun} binaries at the distance of 200Mpc, log(mu^2) is determined with an accuracy of O(0.1)% at the 1sigma level for a fiducial model with mu^2=10^{-33} cm}^{-2} in the case of the phenomenological model.
We show that a positive cosmological constant is incompatible with the quantum-corpuscular resolution of de Sitter metric in form of a coherent state. The reason is very general and is due to the quantum self-destruction of the coherent state because of the scattering of constituent graviton quanta. This process creates an irreversible quantum clock, which precludes eternal de Sitter. It also eliminates the possibility of Boltzmann brains and Poincare recurrences. This effect is expected to be part of any microscopic theory that takes into account the quantum corpuscular structure of the cosmological background. This observation puts the cosmological constant problem in a very different light, promoting it, from a naturalness problem, into a question of quantum consistency. We are learning that quantum gravity cannot tolerate exceedingly-classical sources.
Using the reconstruction technique with an auxiliary field, we investigate which $F(R)$ gravities can produce the matter bounce cosmological solutions. Owing to the specific functional form of the matter bounce Hubble parameter, the reconstruction technique leads, after some simplifications, to the same Hubble parameter as in the matter bounce scenario. Focusing the study to the large and small cosmic time $t$ limits, we were able to find which $F(R)$ gravities can generate the matter bounce Hubble parameter. In the case of small cosmic time limit, which corresponds to large curvature values, the $F(R)$ gravity is $F(R)\sim R+\alpha R^2$, which is an inflation generating gravity, and at small curvature, or equivalently, large cosmic time, the $F(R)$ gravity generating the corresponding limit of the matter bounce Hubble parameter, is $F(R)\sim \frac{1}{R}$, a gravity known to produce late-time acceleration. Thus we have the physically appealing picture in which a Jordan frame $F(R)$ gravity that imitates the matter bounce solution at large and small curvatures, can generate Starobinsky inflation and late-time acceleration. Moreover, the scale factor corresponding to the reconstruction technique coincides almost completely to the matter bounce scenario scale factor, when considered in the aforementioned limiting curvature cases. This is scrutinized in detail, in order to examine the validity of the reconstruction method in these limiting cases, and according to our analysis, exact agreement is achieved.
We propose a new solution to the problem of dark matter directional detection based on large parallel arrays of carbon nanotubes. The phenomenon of ion channeling in single wall nanotubes is simulated to calculate the expected number of recoiling carbon ions, due to the hypothetical scattering with dark matter particles, subsequently being driven along their longitudinal extension. As shown by explicit calculation, the relative orientation of the carbon nanotube array with respect to the direction of motion of the Sun has an appreciable effect on the channeling probability of the struck ion and this provides the required detector anisotropic response.
We consider whether Broad Absorption Line Quasars (BAL QSOs) and Narrow Line Seyfert 1 galaxies (NLS1s) are similar, as suggested by Brandt & Gallagher (2000) and Boroson (2002). For this purpose we constructed a sample of 11 BAL QSOs from existing Chandra and Swift observations. We found that BAL QSOs and NLS1s both operate at high Eddington ratios L/Ledd, although BAL QSOs have slightly lower L/Ledd. BAL QSOs and NLS1s in general have high FeII/H$\beta$ and low [OIII]/H$\beta$ ratios following the classic 'Boroson \& Green' eigenvector 1 relation. We also found that the mass accretion rates $\dot{M}$ of BAL QSOs and NLS1s are more similar than previously thought, although some BAL QSOs exhibit extreme mass accretion rates of more than 10 \msun/year. These extreme mass accretion rates may suggest that the black holes in BAL QSOs are relativistically spinning. Black hole masses in BAL QSOs are a factor of 100 larger than NLS1s. From their location on a M-$\sigma$ plot, we find that BAL QSOs contain fully developed black holes. Applying a principal component analysis to our sample we find eigenvector 1 to correspond to the Eddington ratio L/Ledd, and eigenvector 2 to black hole mass.
In this paper we introduce a LTB-Bianchi I (plane symmetric) model of Universe. We study and solve Einstein field equations. We investigate the effects of such model of Universe in particular these results are important in understanding the effect of the combined presence of an inhomogeneous and anisotropic Universe. The observational magnitude-redshift data deviated from UNION 2 catalog has been analyzed in the framework of this LTB-anisotropic Universe and the fit has been achieved without the inclusion of any dark energy.
We examine the relation between the dynamics of Lema\^{\i}tre-Tolman-Bondi (LTB) dust models (with and without $\Lambda$) and the dynamics of dust perturbations in two of the more familiar formalisms used in cosmology: the metric based Cosmological Perturbation Theory (CPT) and the Covariant Gauge Invariant (GIC) perturbations. For this purpose we recast the evolution of LTB models in terms of a covariant and gauge invariant formalism of local and non-local "exact fluctuations " on a Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) background defined by suitable averages of covariant scalars. We examine the properties of these fluctuations, which can be defined for a confined comoving domain or for an asymptotic domain extending to whole time slices. In particular, the non-local density fluctuation provides a covariant and precise definition for the notion of the "density contrast ". We show that in their linear regime these LTB exact fluctuations (local and non-local) are fully equivalent to the conventional cosmological perturbations in the synchronous-comoving gauge of CPT and to GIC perturbations. As an immediate consequence, we show the time-invariance of the spatial curvature perturbation in a simple form. The present work may provide important theoretical connections between the exact and perturbative (linear or no-linear) approach to the dynamics of dust sources in General Relativity.
In light of the recent measurements of the CMB anisotropy by the WMAP and Planck satellite experiments and the observation of CMB $B$-mode polarization announced by the BICEP2 collaboration, we study simple inflationary models in the context of the Gauss-Bonnet brane-world cosmology. The brane-world cosmological effect modifies the power spectra of scalar and tensor perturbations generated by inflation and causes a dramatic change for the inflationary predictions of the spectral index ($n_s$) and the tensor-to-scalar ratio ($r$) from those obtained in the standard cosmology. In particular, the power spectrum of tensor perturbation is suppressed due to the Gauss-Bonnet brane-world cosmological effect, which is in sharp contrast with inflationary scenario in the Randall-Sundrum brane-world cosmology where the power spectrum is enhanced. Hence, these two brane-world cosmological scenarios are distinguishable. With the dramatic change of the inflationary predictions, the inflationary scenario in the Gauss-Bonnet brane-world cosmology can be tested by more precise measurements of $n_s$ and future observations of the CMB $B$-mode polarization.
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We present a framework for calculating super-horizon curvature perturbation from the dynamics of preheating, which gives a reasonable match to the lattice results. Hubble patches with different initial background field values evolve differently. From the bifurcation of their evolution trajectories we find curvature perturbation using Lyapunov theorem and $\delta N$ formulation. In this way we have established a connection between the finer dynamics of preheating and the curvature perturbation produced in this era. From the calculated analytical form of the curvature perturbation we have derived the effective super-horizon curvature perturbation smoothed out on large scales of CMB. The order of the amount of local form non-gaussianity generated in this process has been calculated and problems regarding the precise determination of it have been pointed out.
Recently ACTPol has measured the cosmic microwave background (CMB) B-mode and E-mode polarizations and obtained TE, EE, BB, TB and EB power spectra in the multipole range 225-8725, detecting six peaks and six troughs of acoustic oscillation in both the TE and EE correlation power spectrum giving independent empirical support to the {\Lambda}CDM cosmology. In our previous paper (di Serego Alighieri, Ni and Pan, Ap. J. 792 (2014) 35 [Paper I]), we have analyzed jointly the results of three experiments on the CMB B-mode polarization -- SPTpol, POLARBEAR and BICEP2 to include in the model, in addition to the gravitational lensing and the inflationary gravitational waves components, also the fluctuation effects induced by the cosmic polarization rotation (CPR), if it exists within the upper limits at the time. In this paper, we fit both the mean CPR angle <{\alpha}> and its fluctuation <{\delta}{\alpha}^2> from the ACTPol data, and update our fitting of CPR fluctuations using BICEP2 data taking the Planck dust measurement results into consideration. We follow the method of Paper I. Mean CPR angle is constrained from the EB correlation power spectra to |<{\alpha}>| < 14 mrad (0.8{\deg}) and the fluctuation (rms) is constrained from the BB correlation power spectra to <{\delta}{\alpha}^2>^(1/2) < 29.3 mrad (1.68{\deg}). Assuming that the polarization angle of Tau A does not change from 89.2 to 146 GHz, the ACTPol data give <{\alpha}> = 1.0 {\pm} 0.63{\deg}. These results suggest that the inclusion of the present ACTPol data is consistent with no CPR detection. With the PLANCK dust measurement, we update our fits of the BICEP2 CPR constraint to be 32.8 mrad (1.88{\deg}). The joint ACTpol-BICEP2-POLARBEAR CPR constraint is 23.7 mrad (1.36{\deg}).
In 1914, Planck introduced the concept of a white body. In nature, no true white bodies are known. We assume that the universe after last-scattering is an ideal white body that contains a tremendously large number of thermal photons and is at an extremely high temperature. Bose-Einstein condensation of photons in an ideal white body is investigated within the framework of quantum statistical mechanism. The computation shows that the transition temperature $T_c$ is a monotonically increasing function of the number density $n$ of photons. At finite temperature, we find that the condensate fraction $N_0(T)/N$ decreases continuously from unity to zero as the temperature increases from zero to the transition temperature $T_c$. Further, we study the radiation properties of an ideal white body. It is found that in the condensation region of $T<T_c$, the spectral intensity $I(\omega,T)$ of white body radiation is identical with Planck's law for blackbody radiation.
We present results based on the systematic analysis of high resolution 95\,ks \textit{Chandra} observations of the strong cool core cluster Abell 2390 at the redshift of z = 0.228, which hosts an energetic radio AGN. This analysis has enabled us to investigate five X-ray deficient cavities in the hot atmosphere of Abell 2390 within central 30\arcsec, three of which are newly detected. Presence of these cavities have been confirmed through a various image processing techniques like, the surface brightness profiles, unsharp masked image, as well as 2D elliptical model subtracted residual map. Temperature profile as well as 2D temperature map revealed structures in the distribution of ICM, in the sense that ICM in NW direction is relatively cooler than that on the SE direction. Two temperature jumps, one from 6\,keV to 9.25\,keV at 72 kpc on the north direction, and the other from 6\,keV to 10.27\,keV at 108 kpc in the east direction have been observed. These temperature jumps are associated with the shocks with Mach numbers 1.54$\pm$0.08 and 1.69$\pm$ 0.09, respectively. Unsharp masked image for A2390 reveals an X-ray edge at $\sim$74\arcsec (268\,kpc), which is found to coincide with the complex radio edge due to weak radio sources. The entropy profile at the core reveals a floor at 12.20$\pm$2.54 keV cm$^2$ and hence confirms intermittent heating by AGN. The diffuse radio emission mapped using the 1.4\,GHz VLA L-band data fills in all the X-ray cavities, and exhibit highly irregular morphology with an elongation along the cool ICM region. The mechanical power injected by the AGN in the form of X-ray cavities is found to be 3.3$\times$10$^{46}$ erg\,s$^{-1}$ and is roughly two orders of magnitude higher than that lost by the ICM in the form of X-ray emission, confirming that AGN feedback is capable enough to quench cooling flow in this cluster.
We present results of analysis of the dark matter (DM) pairwise velocity statistics in different Cosmic Web environments. We use the DM velocity and density field from the Millennium 2 simulation together with the NEXUS+ algorithm to segment the simulation volume into voxels uniquely identifying one of the four possible environments: nodes, filaments, walls or cosmic voids. We show that the PDFs of the mean infall velocities $v_{12}$ as well as its spatial dependence together with the perpendicular and parallel velocity dispersions bear a significant signal of the large-scale structure environment in which DM particle pairs are embedded. The pairwise flows are notably colder and have smaller mean magnitude in wall and voids, when compared to much denser environments of filaments and nodes. We discuss on our results, indicating that they are consistent with a simple theoretical predictions for pairwise motions as induced by gravitational instability mechanism. Our results indicate that the Cosmic Web elements are coherent dynamical entities rather than just temporal geometrical associations. In addition it should be possible to observationally test various Cosmic Web finding algorithms by segmenting available peculiar velocity data and studying resulting pairwise velocity statistics
The linear perturbation of a Kerr black hole induced by a rotating massive circular ring is discussed by using the formalism by Teukolsky, Chrzanowski, Cohen and Kegeles. In these formalism, the perturbed Weyl scalars, $\psi_0$ and $\psi_4$, are first obtained from the Teukolsky equation. The perturbed metric is obtained in a radiation gauge via the Hertz potential. The computation can be done in the same way as in our previous paper, in which we considered the perturbation of a Schwarzschild black hole induced by a rotating ring. By adding lower multipole modes such as mass and angular momentum perturbation which are not computed by the Teukolsky equation, and by appropriately setting the parameters which are related to the gauge freedom, we obtain the perturbed gravitational field which is smooth except on the equatorial plane outside the ring.
This is a write-up of a talk given at the Opava RAGtime meeting in 2011, but it has been updated to include some subsequent related developments. The talk focused on discussion of some aspects of black hole and cosmological horizons under rather general circumstances, and on two different topics related to formation of cosmological structures at different epochs of the universe: virialization of cold dark matter during standard structure formation in the matter-dominated era, and primordial black hole formation during the radiative era.
Links to: arXiv, form interface, find, astro-ph, recent, 1412, contact, help (Access key information)
We present a framework for calculating super-horizon curvature perturbation from the dynamics of preheating, which gives a reasonable match to the lattice results. Hubble patches with different initial background field values evolve differently. From the bifurcation of their evolution trajectories we find curvature perturbation using Lyapunov theorem and $\delta N$ formulation. In this way we have established a connection between the finer dynamics of preheating and the curvature perturbation produced in this era. From the calculated analytical form of the curvature perturbation we have derived the effective super-horizon curvature perturbation smoothed out on large scales of CMB. The order of the amount of local form non-gaussianity generated in this process has been calculated and problems regarding the precise determination of it have been pointed out.
Recently ACTPol has measured the cosmic microwave background (CMB) B-mode and E-mode polarizations and obtained TE, EE, BB, TB and EB power spectra in the multipole range 225-8725, detecting six peaks and six troughs of acoustic oscillation in both the TE and EE correlation power spectrum giving independent empirical support to the {\Lambda}CDM cosmology. In our previous paper (di Serego Alighieri, Ni and Pan, Ap. J. 792 (2014) 35 [Paper I]), we have analyzed jointly the results of three experiments on the CMB B-mode polarization -- SPTpol, POLARBEAR and BICEP2 to include in the model, in addition to the gravitational lensing and the inflationary gravitational waves components, also the fluctuation effects induced by the cosmic polarization rotation (CPR), if it exists within the upper limits at the time. In this paper, we fit both the mean CPR angle <{\alpha}> and its fluctuation <{\delta}{\alpha}^2> from the ACTPol data, and update our fitting of CPR fluctuations using BICEP2 data taking the Planck dust measurement results into consideration. We follow the method of Paper I. Mean CPR angle is constrained from the EB correlation power spectra to |<{\alpha}>| < 14 mrad (0.8{\deg}) and the fluctuation (rms) is constrained from the BB correlation power spectra to <{\delta}{\alpha}^2>^(1/2) < 29.3 mrad (1.68{\deg}). Assuming that the polarization angle of Tau A does not change from 89.2 to 146 GHz, the ACTPol data give <{\alpha}> = 1.0 {\pm} 0.63{\deg}. These results suggest that the inclusion of the present ACTPol data is consistent with no CPR detection. With the PLANCK dust measurement, we update our fits of the BICEP2 CPR constraint to be 32.8 mrad (1.88{\deg}). The joint ACTpol-BICEP2-POLARBEAR CPR constraint is 23.7 mrad (1.36{\deg}).
In 1914, Planck introduced the concept of a white body. In nature, no true white bodies are known. We assume that the universe after last-scattering is an ideal white body that contains a tremendously large number of thermal photons and is at an extremely high temperature. Bose-Einstein condensation of photons in an ideal white body is investigated within the framework of quantum statistical mechanism. The computation shows that the transition temperature $T_c$ is a monotonically increasing function of the number density $n$ of photons. At finite temperature, we find that the condensate fraction $N_0(T)/N$ decreases continuously from unity to zero as the temperature increases from zero to the transition temperature $T_c$. Further, we study the radiation properties of an ideal white body. It is found that in the condensation region of $T<T_c$, the spectral intensity $I(\omega,T)$ of white body radiation is identical with Planck's law for blackbody radiation.
We present results based on the systematic analysis of high resolution 95\,ks \textit{Chandra} observations of the strong cool core cluster Abell 2390 at the redshift of z = 0.228, which hosts an energetic radio AGN. This analysis has enabled us to investigate five X-ray deficient cavities in the hot atmosphere of Abell 2390 within central 30\arcsec, three of which are newly detected. Presence of these cavities have been confirmed through a various image processing techniques like, the surface brightness profiles, unsharp masked image, as well as 2D elliptical model subtracted residual map. Temperature profile as well as 2D temperature map revealed structures in the distribution of ICM, in the sense that ICM in NW direction is relatively cooler than that on the SE direction. Two temperature jumps, one from 6\,keV to 9.25\,keV at 72 kpc on the north direction, and the other from 6\,keV to 10.27\,keV at 108 kpc in the east direction have been observed. These temperature jumps are associated with the shocks with Mach numbers 1.54$\pm$0.08 and 1.69$\pm$ 0.09, respectively. Unsharp masked image for A2390 reveals an X-ray edge at $\sim$74\arcsec (268\,kpc), which is found to coincide with the complex radio edge due to weak radio sources. The entropy profile at the core reveals a floor at 12.20$\pm$2.54 keV cm$^2$ and hence confirms intermittent heating by AGN. The diffuse radio emission mapped using the 1.4\,GHz VLA L-band data fills in all the X-ray cavities, and exhibit highly irregular morphology with an elongation along the cool ICM region. The mechanical power injected by the AGN in the form of X-ray cavities is found to be 3.3$\times$10$^{46}$ erg\,s$^{-1}$ and is roughly two orders of magnitude higher than that lost by the ICM in the form of X-ray emission, confirming that AGN feedback is capable enough to quench cooling flow in this cluster.
We present results of analysis of the dark matter (DM) pairwise velocity statistics in different Cosmic Web environments. We use the DM velocity and density field from the Millennium 2 simulation together with the NEXUS+ algorithm to segment the simulation volume into voxels uniquely identifying one of the four possible environments: nodes, filaments, walls or cosmic voids. We show that the PDFs of the mean infall velocities $v_{12}$ as well as its spatial dependence together with the perpendicular and parallel velocity dispersions bear a significant signal of the large-scale structure environment in which DM particle pairs are embedded. The pairwise flows are notably colder and have smaller mean magnitude in wall and voids, when compared to much denser environments of filaments and nodes. We discuss on our results, indicating that they are consistent with a simple theoretical predictions for pairwise motions as induced by gravitational instability mechanism. Our results indicate that the Cosmic Web elements are coherent dynamical entities rather than just temporal geometrical associations. In addition it should be possible to observationally test various Cosmic Web finding algorithms by segmenting available peculiar velocity data and studying resulting pairwise velocity statistics
The linear perturbation of a Kerr black hole induced by a rotating massive circular ring is discussed by using the formalism by Teukolsky, Chrzanowski, Cohen and Kegeles. In these formalism, the perturbed Weyl scalars, $\psi_0$ and $\psi_4$, are first obtained from the Teukolsky equation. The perturbed metric is obtained in a radiation gauge via the Hertz potential. The computation can be done in the same way as in our previous paper, in which we considered the perturbation of a Schwarzschild black hole induced by a rotating ring. By adding lower multipole modes such as mass and angular momentum perturbation which are not computed by the Teukolsky equation, and by appropriately setting the parameters which are related to the gauge freedom, we obtain the perturbed gravitational field which is smooth except on the equatorial plane outside the ring.
This is a write-up of a talk given at the Opava RAGtime meeting in 2011, but it has been updated to include some subsequent related developments. The talk focused on discussion of some aspects of black hole and cosmological horizons under rather general circumstances, and on two different topics related to formation of cosmological structures at different epochs of the universe: virialization of cold dark matter during standard structure formation in the matter-dominated era, and primordial black hole formation during the radiative era.
Links to: arXiv, form interface, find, astro-ph, recent, 1412, contact, help (Access key information)
We present a framework for calculating super-horizon curvature perturbation from the dynamics of preheating, which gives a reasonable match to the lattice results. Hubble patches with different initial background field values evolve differently. From the bifurcation of their evolution trajectories we find curvature perturbation using Lyapunov theorem and $\delta N$ formulation. In this way we have established a connection between the finer dynamics of preheating and the curvature perturbation produced in this era. From the calculated analytical form of the curvature perturbation we have derived the effective super-horizon curvature perturbation smoothed out on large scales of CMB. The order of the amount of local form non-gaussianity generated in this process has been calculated and problems regarding the precise determination of it have been pointed out.
Recently ACTPol has measured the cosmic microwave background (CMB) B-mode and E-mode polarizations and obtained TE, EE, BB, TB and EB power spectra in the multipole range 225-8725, detecting six peaks and six troughs of acoustic oscillation in both the TE and EE correlation power spectrum giving independent empirical support to the {\Lambda}CDM cosmology. In our previous paper (di Serego Alighieri, Ni and Pan, Ap. J. 792 (2014) 35 [Paper I]), we have analyzed jointly the results of three experiments on the CMB B-mode polarization -- SPTpol, POLARBEAR and BICEP2 to include in the model, in addition to the gravitational lensing and the inflationary gravitational waves components, also the fluctuation effects induced by the cosmic polarization rotation (CPR), if it exists within the upper limits at the time. In this paper, we fit both the mean CPR angle <{\alpha}> and its fluctuation <{\delta}{\alpha}^2> from the ACTPol data, and update our fitting of CPR fluctuations using BICEP2 data taking the Planck dust measurement results into consideration. We follow the method of Paper I. Mean CPR angle is constrained from the EB correlation power spectra to |<{\alpha}>| < 14 mrad (0.8{\deg}) and the fluctuation (rms) is constrained from the BB correlation power spectra to <{\delta}{\alpha}^2>^(1/2) < 29.3 mrad (1.68{\deg}). Assuming that the polarization angle of Tau A does not change from 89.2 to 146 GHz, the ACTPol data give <{\alpha}> = 1.0 {\pm} 0.63{\deg}. These results suggest that the inclusion of the present ACTPol data is consistent with no CPR detection. With the PLANCK dust measurement, we update our fits of the BICEP2 CPR constraint to be 32.8 mrad (1.88{\deg}). The joint ACTpol-BICEP2-POLARBEAR CPR constraint is 23.7 mrad (1.36{\deg}).
In 1914, Planck introduced the concept of a white body. In nature, no true white bodies are known. We assume that the universe after last-scattering is an ideal white body that contains a tremendously large number of thermal photons and is at an extremely high temperature. Bose-Einstein condensation of photons in an ideal white body is investigated within the framework of quantum statistical mechanism. The computation shows that the transition temperature $T_c$ is a monotonically increasing function of the number density $n$ of photons. At finite temperature, we find that the condensate fraction $N_0(T)/N$ decreases continuously from unity to zero as the temperature increases from zero to the transition temperature $T_c$. Further, we study the radiation properties of an ideal white body. It is found that in the condensation region of $T<T_c$, the spectral intensity $I(\omega,T)$ of white body radiation is identical with Planck's law for blackbody radiation.
We present results based on the systematic analysis of high resolution 95\,ks \textit{Chandra} observations of the strong cool core cluster Abell 2390 at the redshift of z = 0.228, which hosts an energetic radio AGN. This analysis has enabled us to investigate five X-ray deficient cavities in the hot atmosphere of Abell 2390 within central 30\arcsec, three of which are newly detected. Presence of these cavities have been confirmed through a various image processing techniques like, the surface brightness profiles, unsharp masked image, as well as 2D elliptical model subtracted residual map. Temperature profile as well as 2D temperature map revealed structures in the distribution of ICM, in the sense that ICM in NW direction is relatively cooler than that on the SE direction. Two temperature jumps, one from 6\,keV to 9.25\,keV at 72 kpc on the north direction, and the other from 6\,keV to 10.27\,keV at 108 kpc in the east direction have been observed. These temperature jumps are associated with the shocks with Mach numbers 1.54$\pm$0.08 and 1.69$\pm$ 0.09, respectively. Unsharp masked image for A2390 reveals an X-ray edge at $\sim$74\arcsec (268\,kpc), which is found to coincide with the complex radio edge due to weak radio sources. The entropy profile at the core reveals a floor at 12.20$\pm$2.54 keV cm$^2$ and hence confirms intermittent heating by AGN. The diffuse radio emission mapped using the 1.4\,GHz VLA L-band data fills in all the X-ray cavities, and exhibit highly irregular morphology with an elongation along the cool ICM region. The mechanical power injected by the AGN in the form of X-ray cavities is found to be 3.3$\times$10$^{46}$ erg\,s$^{-1}$ and is roughly two orders of magnitude higher than that lost by the ICM in the form of X-ray emission, confirming that AGN feedback is capable enough to quench cooling flow in this cluster.
We present results of analysis of the dark matter (DM) pairwise velocity statistics in different Cosmic Web environments. We use the DM velocity and density field from the Millennium 2 simulation together with the NEXUS+ algorithm to segment the simulation volume into voxels uniquely identifying one of the four possible environments: nodes, filaments, walls or cosmic voids. We show that the PDFs of the mean infall velocities $v_{12}$ as well as its spatial dependence together with the perpendicular and parallel velocity dispersions bear a significant signal of the large-scale structure environment in which DM particle pairs are embedded. The pairwise flows are notably colder and have smaller mean magnitude in wall and voids, when compared to much denser environments of filaments and nodes. We discuss on our results, indicating that they are consistent with a simple theoretical predictions for pairwise motions as induced by gravitational instability mechanism. Our results indicate that the Cosmic Web elements are coherent dynamical entities rather than just temporal geometrical associations. In addition it should be possible to observationally test various Cosmic Web finding algorithms by segmenting available peculiar velocity data and studying resulting pairwise velocity statistics
The linear perturbation of a Kerr black hole induced by a rotating massive circular ring is discussed by using the formalism by Teukolsky, Chrzanowski, Cohen and Kegeles. In these formalism, the perturbed Weyl scalars, $\psi_0$ and $\psi_4$, are first obtained from the Teukolsky equation. The perturbed metric is obtained in a radiation gauge via the Hertz potential. The computation can be done in the same way as in our previous paper, in which we considered the perturbation of a Schwarzschild black hole induced by a rotating ring. By adding lower multipole modes such as mass and angular momentum perturbation which are not computed by the Teukolsky equation, and by appropriately setting the parameters which are related to the gauge freedom, we obtain the perturbed gravitational field which is smooth except on the equatorial plane outside the ring.
This is a write-up of a talk given at the Opava RAGtime meeting in 2011, but it has been updated to include some subsequent related developments. The talk focused on discussion of some aspects of black hole and cosmological horizons under rather general circumstances, and on two different topics related to formation of cosmological structures at different epochs of the universe: virialization of cold dark matter during standard structure formation in the matter-dominated era, and primordial black hole formation during the radiative era.
Links to: arXiv, form interface, find, astro-ph, recent, 1501, contact, help (Access key information)