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Full-Text Articles in Astrophysics and Astronomy
Mapping The Dark Matter From Uv Light At High Redshift: An Empirical Approach To Understand Galaxy Statistics, Kyoung-Soo Lee, Mauro Giavalisco, Charlie Conroy, Risa H. Wechsler, Henry C. Ferguson, Rachel S. Somerville, Mark E. Dickinson, Claudia M. Urry
Mapping The Dark Matter From Uv Light At High Redshift: An Empirical Approach To Understand Galaxy Statistics, Kyoung-Soo Lee, Mauro Giavalisco, Charlie Conroy, Risa H. Wechsler, Henry C. Ferguson, Rachel S. Somerville, Mark E. Dickinson, Claudia M. Urry
Astronomy Department Faculty Publication Series
We present a simple formalism to interpret the observations of two galaxy statistics, the UV luminosity function (LF) and two-point correlation functions for star-forming galaxies at z∼4, 5, and 6 in the context of Λ cold dark matter cosmology. Both statistics are the result of how star formation takes place in dark matter halos, and thus are used to constrain how UV light depends on halo properties, in particular halo mass. The two physical quantities we explore are the star formation duty cycle, and the range of UV luminosity that a halo of mass M can have (mean and …
The Nature Of Red Dwarf Galaxies, Y Wang, Xh Yang, Hj Mo, Fc Van Den Bosch, N Katz, A Pasquali, Dh Mcintosh, Sm Weinmann
The Nature Of Red Dwarf Galaxies, Y Wang, Xh Yang, Hj Mo, Fc Van Den Bosch, N Katz, A Pasquali, Dh Mcintosh, Sm Weinmann
Astronomy Department Faculty Publication Series
Using dark matter halos traced by galaxy groups selected from the Sloan Digital Sky Survey Data Release 4, we find that about 1/4 of the faint galaxies (0.1 Mr – 5log h> – 17.05, hereafter dwarfs) that are the central galaxies in their own halo are not blue and star forming, as expected in standard models of galaxy formation, but are red. In contrast, this fraction is about 1/2 for dwarf satellite galaxies. Many red dwarf galaxies are physically associated with more massive halos. In total, about ~45% of red dwarf galaxies reside in massive halos as satellites, …
Noise-Driven Evolution In Stellar Systems: Theory, Martin D. Weinberg
Noise-Driven Evolution In Stellar Systems: Theory, Martin D. Weinberg
Astronomy Department Faculty Publication Series
We present a theory for describing the evolution of a galaxy caused by stochastic events such as weak mergers, transient spiral structure, orbiting blobs, etc. This noise excites large-scale patterns that drives the evolution of the galactic density profile. In dark-matter haloes, the repeated stochastic perturbations preferentially ring the lowest-order modes of the halo with only a very weak dependence on the details of their source. Shaped by these modes, the profile quickly takes on a nearly self-similar form. We show that this form has the features of the “universal profile” reported by Navarro, Frenk, & White independent of initial …
The Bar-Halo Interaction - I. From Fundamental Dynamics To Revised N-Body Requirements, Md Weinberg, N Katz
The Bar-Halo Interaction - I. From Fundamental Dynamics To Revised N-Body Requirements, Md Weinberg, N Katz
Astronomy Department Faculty Publication Series
A galaxy remains near equilibrium for most of its history. Only through resonances can non-axisymmetric features, such as spiral arms and bars, exert torques over large scales and change the overall structure of the galaxy. In this paper, we describe the resonant interaction mechanism in detail, derive explicit criteria for the particle number required to simulate these dynamical processes accurately using N-body simulations, and illustrate them with numerical experiments. To do this, we perform a direct numerical solution of perturbation theory, in short, by solving for each orbit in an ensemble and make detailed comparisons with N-body simulations. The criteria …
Dark Matter Halo Response To The Disc Growth, Jh Choi, Y Lu, Hj Mo, Md Weinberg
Dark Matter Halo Response To The Disc Growth, Jh Choi, Y Lu, Hj Mo, Md Weinberg
Astronomy Department Faculty Publication Series
We consider the sensitivity of the circular-orbit adiabatic contraction approximation to the baryon condensation rate and the orbital structure of dark matter haloes in the Λ cold dark matter (ΛCDM) paradigm. Using one-dimensional hydrodynamic simulations including the dark matter halo mass accretion history and gas cooling, we demonstrate that the adiabatic approximation is approximately valid even though haloes and discs may assemble simultaneously. We further demonstrate the validity of the simple approximation for ΛCDM haloes with isotropic velocity distributions using three-dimensional N-body simulations. This result is easily understood: an isotropic velocity distribution in a cuspy halo requires more circular orbits …
From Galaxy-Galaxy Lensing To Cosmological Parameters, J Yoo, Jl Tinker, Dh Weinberg, Z Zheng, N Katz, R Dave
From Galaxy-Galaxy Lensing To Cosmological Parameters, J Yoo, Jl Tinker, Dh Weinberg, Z Zheng, N Katz, R Dave
Astronomy Department Faculty Publication Series
Galaxy-galaxy lensing uses the weak distortion of background sources to measure the mean excess surface density profile, ΔΣ(r), around a sample of foreground lensing galaxies. We develop a method for combining ΔΣ(r) with the galaxy-galaxy correlation function ξgg(r) to constrain the matter density parameter Ωm and the matter fluctuation amplitude σ8, going beyond the linear biasing model to reach the level of accuracy demanded by current and future measurements. We adopt the halo occupation distribution (HOD) framework and test its applicability to this problem by examining the effects of …
On The Origin Of Cold Dark Matter Halo Density Profiles, Y Lu, Hj Mo, N Katz, Md Weinberg
On The Origin Of Cold Dark Matter Halo Density Profiles, Y Lu, Hj Mo, N Katz, Md Weinberg
Astronomy Department Faculty Publication Series
N-body simulations predict that cold dark matter (CDM) halo-assembly occurs in two phases: (i) a fast-accretion phase with a rapidly deepening potential well; and (ii) a slow-accretion phase characterized by a gentle addition of mass to the outer halo with little change in the inner potential well. We demonstrate, using one-dimensional simulations, that this two-phase accretion leads to CDM haloes of the Navarro, Frenk & White (NFW) form and provides physical insight into the properties of the mass-accretion history that influence the final profile. Assuming that the velocities of CDM particles are effectively isotropized by fluctuations in the gravitational potential …
Pre-Heating By Pre-Virialization And Its Impact On Galaxy Formation, Hj Mo, Xh Yang, Fc Van Den Bosch, N Katz, I Zehavi, T Tripp, Dv Bowen, Kr Sembach, Eb Jenkins, Bd Savage, P Richter
Pre-Heating By Pre-Virialization And Its Impact On Galaxy Formation, Hj Mo, Xh Yang, Fc Van Den Bosch, N Katz, I Zehavi, T Tripp, Dv Bowen, Kr Sembach, Eb Jenkins, Bd Savage, P Richter
Astronomy Department Faculty Publication Series
We use recent observations of the H i mass function to constrain galaxy formation. The data conflict with the standard model where most of the gas in a low-mass dark matter halo is assumed to settle into a disc of cold gas that is depleted by star formation and supernova-driven outflows until the disc becomes gravitationally stable. Assuming a star formation threshold density supported by both theory and observations, this model predicts H i masses that are much too large. The reason is simple: supernova feedback requires star formation, which in turn requires a high surface density for the gas. …
Bar-Driven Dark Halo Evolution: A Resolution Of The Cusp-Core Controversy, Md Weinberg, N Katz
Bar-Driven Dark Halo Evolution: A Resolution Of The Cusp-Core Controversy, Md Weinberg, N Katz
Astronomy Department Faculty Publication Series
Simulations predict that the dark matter halos of galaxies should have central cusps, while those inferred from observed galaxies do not have cusps. We demonstrate, using both linear perturbation theory and n-body simulations, that a disk bar, which should be ubiquitous in forming galaxies, can produce cores in cuspy cold dark matter profiles within five bar orbital times. Simulations of forming galaxies suggest that one of Milky Way size could have a 10 kpc primordial bar; this bar will remove the cusp out to ~2.5 kpc in ~1.5 Gyr, while the disk would lose only ~8% of its original angular …
High-Redshift Galaxies In Cold Dark Matter Models, Dh Weinberg, L Hernquist, N Katz
High-Redshift Galaxies In Cold Dark Matter Models, Dh Weinberg, L Hernquist, N Katz
Astronomy Department Faculty Publication Series
We use hydrodynamic cosmological simulations to predict the star formation properties of high-redshift galaxies (z = 2-6) in five variants of the inflationary cold dark matter scenario, paying particular attention to z = 3, the redshift of the largest "Lyman break galaxy" (LBG) samples. Because we link the star formation timescale to the local gas density, the rate at which a galaxy forms stars is governed mainly by the rate at which it accretes cooled gas from the surrounding medium. At z = 3, star formation in most of the simulated galaxies is steady on ~200 Myr timescales, and …
Noise-Driven Evolution In Stellar Systems - Ii. A Universal Halo Profile, Md Weinberg
Noise-Driven Evolution In Stellar Systems - Ii. A Universal Halo Profile, Md Weinberg
Astronomy Department Faculty Publication Series
Disc instabilities such as arm and bar formation, minor mergers and tidal encounters drive a galaxy from equilibrium. Using the theory that describes the evolution of a galaxy halo as a result of stochastic fluctuations developed in the companion paper to this one, we show that this sort of noise evolves a halo toward a standard profile, independent of its initial profile and concentration. This process can substantially redistribute the mass in dark-matter haloes in the 10 Gyr since formation. Three different noise processes are studied: (i) a bombardment by blobs of mass that are small compared to the halo …
Noise-Driven Evolution In Stellar Systems - I. Theory, Md Weinberg
Noise-Driven Evolution In Stellar Systems - I. Theory, Md Weinberg
Astronomy Department Faculty Publication Series
We present a theory for describing the evolution of a galaxy caused by stochastic events such as weak mergers, transient spiral structure, orbiting blobs, etc. This noise excites large-scale patterns that drive the evolution of the galactic density profile. In a dark matter halo, the repeated stochastic perturbations preferentially ring the lowest-order modes with only a very weak dependence on the details of their source. The subsequent redistribution of halo mass is determined only by the mechanics of these modes. The halo profile then evolves toward a universal asymptotic form for a wide variety of noise sources. Such a convergence …
Intergalactic Helium Absorption In Cold Dark Matter Models, Rac Croft, Dh Weinberg, N Katz, L Hernquist
Intergalactic Helium Absorption In Cold Dark Matter Models, Rac Croft, Dh Weinberg, N Katz, L Hernquist
Astronomy Department Faculty Publication Series
Observations from the Hopkins Ultraviolet Telescope and the Hubble Space Telescope have recently detected He II absorption along the lines of sight to two high-redshift quasars. We use cosmological simulations with gas dynamics to investigate He II absorption in the cold dark matter (CDM) theory of structure formation. We consider two Ω = 1 CDM models with different normalizations and one open universe (Ω0 = 0.4) CDM model. The simulations incorporate the photoionizing UV background spectrum computed by Haardt & Madau, which is based on the output of observed quasars and reprocessing by the Lyα forest. The simulated …