A5003646453- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Cosmology and Gravitation Theories
- Stellar, planetary, and galactic studies
- Remote Sensing in Agriculture
- Scientific Research and Discoveries
- Dark Matter and Cosmic Phenomena
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Gamma-ray bursts and supernovae
- Black Holes and Theoretical Physics
- Impact of Light on Environment and Health
- Plant Water Relations and Carbon Dynamics
- Radio Astronomy Observations and Technology
- Climate variability and models
- Geophysics and Gravity Measurements
- Stochastic processes and statistical mechanics
- Statistical and numerical algorithms
- Advanced Statistical Methods and Models
- Astrophysics and Star Formation Studies
- Relativity and Gravitational Theory
- Methane Hydrates and Related Phenomena
- Ionosphere and magnetosphere dynamics
- Gaussian Processes and Bayesian Inference
- Spectroscopy and Laser Applications
University of Pennsylvania
2015-2024
The Abdus Salam International Centre for Theoretical Physics (ICTP)
2014-2024
California University of Pennsylvania
2016-2024
Center for Theoretical Physics
2024
Dharmsinh Desai University
2023-2024
Yale University
2022
Institut d'Astrophysique de Paris
2018-2019
Sorbonne Université
2018-2019
Université Paris Sciences et Lettres
2018-2019
Université Paris Cité
2018-2019
We measure cosmological parameters using the three-dimensional power spectrum $P(k)$ from over 200 000 galaxies in Sloan Digital Sky Survey (SDSS) combination with Wilkinson Microwave Anisotropy Probe (WMAP) and other data. Our results are consistent a ``vanilla'' flat adiabatic cold dark matter model constant without tilt ${(n}_{s}=1),$ running tilt, tensor modes, or massive neutrinos. Adding SDSS information more than halves WMAP-only error bars on some parameters, tightening...
Dark matter haloes are biased tracers of the underlying dark distribution. We use a simple model to provide relation between abundance and their spatial distribution on large scales. Our shows that knowledge unconditional mass function alone is sufficient an accurate estimate large-scale bias factor. then measured in numerical simulations SCDM, OCDM ΛCDM compute this bias. Comparison with these way estimating its evolution for less massive as well ones. In particular, we show less/more than...
We measure the large-scale real-space power spectrum P(k) using a sample of 205,443 galaxies from Sloan Digital Sky Survey, covering 2417 square degrees with mean redshift z~0.1. employ matrix-based method pseudo-Karhunen-Loeve eigenmodes, producing uncorrelated minimum-variance measurements in 22 k-bands both clustering and its anisotropy due to redshift-space distortions, narrow well-behaved window functions range 0.02 h/Mpc < k 0.3h/Mpc. pay particular attention modeling, quantifying...
The Press—Schechter, excursion set approach allows one to make predictions about the shape and evolution of mass function bound objects. combines assumption that objects collapse spherically with initial density fluctuations were Gaussian small. predicted is reasonably accurate, although it has fewer high-mass more low-mass than are seen in simulations hierarchical clustering. We show discrepancy between theory simulation can be reduced substantially if structures assumed form from an...
We measure the large-scale real-space power spectrum $P(k)$ using luminous red galaxies (LRGs) in Sloan Digital Sky Survey (SDSS) and use this measurement to sharpen constraints on cosmological parameters from Wilkinson Microwave Anisotropy Probe (WMAP). employ a matrix-based estimation method Pseudo-Karhunen-Lo\`eve eigenmodes, producing uncorrelated minimum-variance measurements 20 $k$-bands of both clustering its anisotropy due redshift-space distortions, with narrow well-behaved window...
The excursion set approach allows one to estimate the abundance and spatial distribution of virialized dark matter haloes efficiently accurately. predictions this depend on how non-linear processes collapse virialization are modelled. We present simple analytic approximations that allow us compare associated with spherical ellipsoidal collapse. In particular, we formulae for universal unconditional mass function bound objects conditional which describes progenitors in a given range today....
We study the luminosity and color dependence of galaxy two-point correlation function in Sloan Digital Sky Survey, starting from a sample ~200,000 galaxies over 2500 deg2. concentrate our analysis on volume-limited subsamples specified ranges, for which we measure projected wp(rp), is directly related to real-space ξ(r). The amplitude wp(rp) rises continuously with Mr ≈ -17.5 -22.5, most rapid increase occurring above characteristic L* (Mr -20.5). Over scales 0.1 h-1 Mpc < rp 10 Mpc,...
We present in this paper a detailed analysis of the effect environment on star formation activity galaxies within Early Data Release (EDR) Sloan Digital Sky Survey (SDSS). have used Hα emission line to derive rate (SFR) for each galaxy volume-limited sample 8598 with 0.05 ≤ z 0.095 and M(r*) -20.45. find that SFR is strongly correlated local (projected) density, thus we here density-SFR relation analogous density-morphology relation. The density seen three ways. First, overall distribution...
We present the first measurements of clustering in Sloan Digital Sky Survey (SDSS) galaxy redshift survey. Our sample consists 29,300 galaxies with redshifts 5,700 km/s < cz 39,000 km/s, distributed several long but narrow (2.5-5 degree) segments, covering 690 square degrees. For full, flux-limited sample, redshift-space correlation length is approximately 8 Mpc/h. The two-dimensional function ξ(r_p,π) shows clear signatures both small-scale, ``fingers-of-God'' distortion caused by...
We study galaxy clustering in the framework of halo models, where gravitational is described terms dark matter halos. At small scales, statistics are dominated by density profiles, whereas at large correlations result combining nonlinear perturbation theory with biasing. Galaxies assumed to follow profiles they inhabit, and formation efficiency characterized number galaxies that populate a given mass. This approach leads generic predictions: power spectrum shows power-law behavior even...
We present a model for the distribution of void sizes and its evolution in context hierarchical scenarios gravitational structure formation. find that at any cosmic epoch voids have size is well-peaked about characteristic evolves self-similarly time. This distinct contrast to virialized halo masses, which does not small-scale cut-off.
We present a fast method of producing mock galaxy catalogues that can be used to compute covariance matrices large-scale clustering measurements and test the methods analysis. Our populates 2nd-order Lagrangian Perturbation Theory (2LPT) matter field, where we calibrate masses dark halos by detailed comparisons with N-body simulations. demonstrate is recovered at ~10 per cent accuracy. populate galaxies using Halo Occupation Distribution (HOD) prescription, which has been calibrated...
The relationship between galaxy and matter overdensities, bias, is most often assumed to be local. This however unstable under time evolution, we provide proofs several sets of assumptions. In the simplest model galaxies are created locally linearly biased at a single time, subsequently move with (no velocity bias) conserving their comoving number density merging). We show that, after this formation bias becomes unavoidably non-local non-linear large scales. identify gravitationally induced...
In addition to the large systematic differences arising from assumptions about stellar mass-to-light ratio, massive end of mass function is rather sensitive how one fits light profiles most luminous galaxies. We quantify this by comparing luminosity and functions based on SDSS cmodel magnitudes, PyMorph single-Sersic Sersic-Exponential surface brightness galaxies in SDSS. The return more light, so that predicted masses are larger than when magnitudes used. As a result, total density at z~0.1...
We compare the set of local galaxies having dynamically measured black holes with a large, unbiased sample extracted from Sloan Digital Sky Survey. confirm earlier work showing that majority hole hosts have significantly higher velocity dispersions sigma than similar stellar mass. use Monte-Carlo simulations to illustrate effect on scaling relations if this bias arises requirement sphere influence must be resolved measure masses spatially kinematics. find selection artificially increases...
The abundance of galaxy clusters can constrain both the geometry and growth structure in our Universe. However, this probe could be significantly complicated by recent claims nonuniversality -- non-trivial dependences with respect to cosmological model redshift. In work we analyse dependance mass function on way haloes are identified establish if cause departures from universality. order explore dependance, use a set different N-body simulations (Le SBARBINE simulations), latest parameters...
In this paper, we argue and show numerically that the threshold to form primordial black holes from an initial spherically symmetric perturbation is, excellent approximation, universal, whenever given in terms of compaction function averaged over a sphere radius ${r}_{m}$, where ${r}_{m}$ is scale on which maximum. This can be understood as requirement that, for hole form, each shell should have amplitude exceeding so-called Harada-Yoo-Kohri limit. For radiation dominated universe argued,...
A magnitude-limited sample of nearly 9000 early-type galaxies in the redshift range 0.01 ≤ z 0.3 was selected from Sloan Digital Sky Survey (SDSS) using morphological and spectral criteria. The fundamental plane relation this is Ro ∝ σ1.49±0.05I r* band. It approximately same g*, i*, z* bands. Relative to population at median sample, lower higher redshifts have evolved only a little. If used quantify evolution, then apparent magnitude limit can masquerade as evolution; once selection effect...
We measure the projected correlation function w_p(r_p) from Sloan Digital Sky Survey for a flux-limited sample of 118,000 galaxies and volume limited subset 22,000 with absolute magnitude M_rM_1=4.74 X 10^{13}\msun/h is _M=(M/M_1)^{0.89}, 75% residing in less massive, single-galaxy halos. This physically motivated model has same number free parameters as power law, it fits data better, χ^2/d.o.f.=0.93 compared to 6.12 (for 10 degrees freedom, incorporating covariance errors). Departures...
A generic prediction of hierarchical gravitational clustering models is that the distribution halo formation times should depend relatively strongly on mass, massive haloes forming more recently, and only weakly, if at all, large scale environment haloes. We present a novel test this assumption which uses statistic proves to be particularly well-suited detecting quantifying weak correlations with environment. find close pairs form slightly higher redshifts than do widely separated pairs,...
A magnitude limited sample of nearly 9000 early-type galaxies, in the redshift range 0.01 < z 0.3, was selected from Sloan Digital Sky Survey using morphological and spectral criteria. The used to study how galaxy observables, including luminosity L, effective radius R_o, surface brightness I_o, color, velocity dispersion sigma, are correlated with one another. Measurement biases understood mock catalogs which reproduce all observed scaling relations their dependences on fitting...
We provide fits to the distribution of galaxy luminosity, size, velocity dispersion and stellar mass as a function concentration index C_r morphological type in SDSS. also quantify how estimates fraction `early' or `late' galaxies depend on whether samples were cut color, light profile shape, compare with similar based morphology. Our show that Es account for about 20% r-band luminosity density, rho_Lr, 25% rho_*; including S0s Sas increases these numbers 33% 40%, 50% 60%, respectively....
The angular distribution of galaxies encodes a wealth information about large scale structure. Ultimately, the Sloan Digital Sky Survey (SDSS) will record positions order 10^8 in five bands, adding significantly to cosmological constraints. This is first series papers analyzing rectangular stripe 2.5x90 degrees from early SDSS data. We present correlation function for four separate magnitude bins on scales ranging 0.003 15 degrees. Much focus this paper potential systematic effects. show...