A5017618068- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Dark Matter and Cosmic Phenomena
- Cosmology and Gravitation Theories
- Astrophysics and Star Formation Studies
- Scientific Research and Discoveries
- Gamma-ray bursts and supernovae
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- History and Developments in Astronomy
- Astrophysics and Cosmic Phenomena
- Remote Sensing in Agriculture
- Adaptive optics and wavefront sensing
- Radio Astronomy Observations and Technology
- Atomic and Subatomic Physics Research
- Astro and Planetary Science
- Plant Water Relations and Carbon Dynamics
- CCD and CMOS Imaging Sensors
- Black Holes and Theoretical Physics
- Impact of Light on Environment and Health
- Relativity and Gravitational Theory
- Advanced Thermodynamics and Statistical Mechanics
- Species Distribution and Climate Change
- Microscopic Colitis
University of California, Irvine
2015-2024
UC Irvine Health
2005-2021
Max Planck Institute for Astronomy
2019
Max Planck Society
2019
Urology San Antonio
2019
California Institute of Technology
2014
University of Chicago
2007
Imaging Center
2007
Center for Astrophysics Harvard & Smithsonian
2003-2006
The University of Texas Southwestern Medical Center
2005
(Abridged) We describe here the most ambitious survey currently planned in optical, Large Synoptic Survey Telescope (LSST). A vast array of science will be enabled by a single wide-deep-fast sky survey, and LSST have unique capability faint time domain. The design is driven four main themes: probing dark energy matter, taking an inventory Solar System, exploring transient optical sky, mapping Milky Way. wide-field ground-based system sited at Cerro Pach\'{o}n northern Chile. telescope 8.4 m...
We study dark matter halo density profiles in a high-resolution N-body simulation of ΛCDM cosmology. Our statistical sample contains ∼5000 haloes the range 1011−1014 h−1 M⊙, and resolution allows subhaloes inside host haloes. The are parametrized by an NFW form with two parameters, inner radius rs virial Rvir, we define concentration cvir=Rvirrs. First, find that, for given mass, redshift dependence median is cvir∝(1+z)−1. This corresponds to rs(z)∼constant, contrary earlier suspicions that...
We show that dissipationless LCDM simulations predict the majority of most massive subhaloes Milky Way are too dense to host any its bright satellites (L_V > 10^5 L_sun). These dark have circular velocities at infall 30-70 km/s and masses [0.2-4] x 10^10 M_sun. Unless is a statistical anomaly, this implies galaxy formation becomes effectively stochastic these masses. This in marked contrast well-established monotonic relation between luminosity halo velocity (or mass) for more haloes....
We present a series of high-resolution cosmological simulations galaxy formation to z=0, spanning halo masses ~10^8-10^13 M_sun, and stellar ~10^4-10^11. Our include fully explicit treatment both the multi-phase ISM (molecular through hot) feedback. The feedback inputs (energy, momentum, mass, metal fluxes) are taken directly from population models. These sources feedback, with zero adjusted parameters, reproduce observed relation between mass up M_halo~10^12 M_sun (including dwarfs,...
A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of exciting science opportunities next decade. The Large Synoptic Survey Telescope (LSST) have an effective aperture 6.7 meters and imaging camera field view 9.6 deg^2, be devoted ten-year 20,000 deg^2 south +15 deg. Each pointing imaged 2000 times fifteen second exposures six broad from 0.35 1.1 microns, total point-source depth r~27.5. LSST Science Book describes basic...
We study the relation between density profiles of dark matter halos and their mass assembly histories using a statistical sample in high-resolution N-body simulation ΛCDM cosmology. For each halo at z = 0, we identify its merger history tree determine concentration parameters cvir for all progenitors, thus providing structural halo. fit accretion by universal function with one parameter, formation epoch ac, defined when log rate d M/d falls below critical value S. find that late-forming...
If the favored hierarchical cosmological model is correct, then Milky Way system should have accreted ~100-200 luminous satellite galaxies in past \~12 Gyr. We this process using a hybrid semi-analytic plus N-body approach which distinguishes explicitly between evolution of light and dark matter satellites. This distinction essential to our ability produce realistic stellar halo, with mass density profile much like that own Galaxy, surviving population matches observed number counts...
The Feedback In Realistic Environments (FIRE) project explores feedback in cosmological galaxy formation simulations. Previous FIRE simulations used an identical source code (FIRE-1) for consistency. Motivated by the development of more accurate numerics - including hydrodynamic solvers, gravitational softening, and supernova coupling algorithms exploration new physics (e.g. magnetic fields), we introduce FIRE-2, updated numerical implementation GIZMO code. We run a suite compare against...
[Abridged] We study the angular-momentum profiles of a statistical sample halos drawn from high-resolution N-body simulation LCDM cosmology. find that cumulative mass distribution specific angular momentum, j, in halo Mv is well fit by universal function, M(<j) = \mu j/(j_0+j). This profile defined one shape parameter (\mu or j_0) addition to global spin \lambda. It follows power-law over most mass, and flattens at large with flattening more pronounced for small values \mu. Compared uniform...
We use the Aquarius simulations to show that most massive subhalos in galaxy-mass dark matter halos LCDM are grossly inconsistent with dynamics of brightest Milky Way dwarf spheroidal galaxies. While best-fitting hosts spheroidals all have 12 < Vmax 25 km/s, predict at least ten > km/s. These also among earlier times, and significantly exceed UV suppression mass back z ~ 10. No LCDM-based model satellite population explains this result. The problem lies satellites' densities: it is...
We use cosmological simulations to study the effects of self-interacting dark matter (SIDM) on density profiles and substructure counts halos from scales spiral galaxies galaxy clusters, focusing explicitly models with cross sections over particle mass \sigma/m = 1 0.1 cm^2/g. Our rely a new SIDM N-body algorithm that is derived self-consistently Boltzmann equation reproduces analytic expectations in controlled numerical experiments. find well-resolved have constant-density cores,...
We present spectroscopic metallicities of individual stars in seven gas-rich dwarf irregular galaxies (dIrrs), and we show that dIrrs obey the same mass-metallicity relation as spheroidal (dSph) satellites both Milky Way M31: Z_* ~ M_*^(0.30 +/- 0.02). The uniformity is contradiction to previous estimates metallicity based on photometry. This relationship roughly continuous with stellar mass-stellar for massive M_* = 10^12 M_sun. Although average depend only mass, shapes their distributions...
We derive an accurate mass estimator for dispersion-supported stellar systems and demonstrate its validity by analyzing resolved line-of-sight velocity data globular clusters, dwarf galaxies, elliptical galaxies. Specifically, manipulating the spherical Jeans equation we show that dynamical enclosed within 3D deprojected half-light radius r_1/2 can be determined with only mild assumptions about spatial variation of dispersion anisotropy. find M_1/2 = 3 \sigma_los^2 / G ~ 4 R_eff G, where is...
One of the main challenges facing standard hierarchical structure formation models is that predicted abundance Galactic subhalos with circular velocities vc ~ 10-30 km s-1 an order magnitude higher than number satellites actually observed within Local Group. Using a simple model for and evolution dark halos, based on extended Press-Schechter formalism tested against N-body results, we show theoretical predictions can be reconciled observations if gas accretion in low-mass halos suppressed...
The dark energy plus cold matter ($\Lambda$CDM) cosmological model has been a demonstrably successful framework for predicting and explaining the large-scale structure of Universe its evolution with time. Yet on length scales smaller than $\sim 1$ Mpc mass 10^{11} M_{\odot}$, theory faces number challenges. For example, observed cores many dark-matter dominated galaxies are both less dense cuspy naively predicted in $\Lambda$CDM. small dwarf satellites Local Group is also far below count...
Using six high resolution dissipationless simulations with a varying box size in flat LCDM universe, we study the mass and redshift dependence of dark matter halo shapes for M_vir = 9.0e11 - 2.0e14, over range z=0-3, two values sigma_8=0.75 0.9. Remarkably, find that redshift, mass, sigma_8 mean smallest-to-largest axis ratio halos is well described by simple power-law relation (0.54 +- 0.02)(M_vir/M_*)^(-0.050 0.003), where s measured at 0.3 R_vir z dependences are governed characteristic...
We investigate the dependence of dark matter halo clustering on formation time, density profile concentration, and subhalo occupation number, using high-resolution numerical simulations a LCDM cosmology. confirm results that is function this trend depends mass. For first we show unequivocally concentration bias mass, redshift can be accurately parameterized in simple way: b(c,M|z) = b(M|z) b(c|M/M*). The scaling between changes sign with value M/M*: high (early forming) objects cluster more...
(Abridged) The violent hierarchical nature of the LCDM cosmology poses serious difficulties for formation disk galaxies. To help resolve these issues, we describe a new, merger-driven scenario cosmological galaxies at high redshifts that supplements standard model based on dissipational collapse.In this picture, large gaseous disks may be produced from high-angular momentum mergers systems are gas-dominated, i.e. M_gas/(M_gas +M_star > 0.5 height merger. Pressurization multiphase...
If dark matter has a large self-interaction scattering cross-section, then interactions among dark-matter particles will drive galaxy and cluster haloes to become spherical in their centres. Work the past used this effect rule out velocity-independent, elastic cross-sections larger than σ/m ≃ 0.02 cm2 g−1 based on comparisons shapes of lensing potentials X-ray isophotes. In paper, we use cosmological simulations show that these constraints were off by more an order magnitude because (a) they...
The cold dark matter (CDM) cosmological model has been remarkably successful in explaining cosmic structure over an enormous span of redshift, but it faced persistent challenges from observations that probe the innermost regions halos and properties Milky Way's dwarf galaxy satellites. We review current observational theoretical status these "small scale controversies." Cosmological simulations incorporate only gravity collisionless CDM predict with abundant substructure central densities...
The standard treatment of cooling in cold dark matter haloes assumes that all the gas within a 'cooling radius' cools and contracts monolithically to fuel galaxy formation. Here we take into account expectation hot galactic is thermally unstable prone fragmentation during show implications are more far-reaching than previously expected: allowing multiphase fundamentally alters expectations about infall naturally gives rise characteristic upper limit on masses galaxies, as observed....
We present results of a convergence study in which we compare the density profiles cold dark matter halos simulated with varying mass and force resolutions. show that although increasing resolution allows one to probe deeper into inner halo regions, converge on scales larger than "effective" spatial simulation. This is defined by both softening resolution. On radii resolution, do not experience any systematical trends when number particles or increases further. In simulations presented this...
We have used data from the Sloan Digital Sky Survey (SDSS) Data Release 5 to explore overall structure and substructure of stellar halo Milky Way using about 4 million color-selected main sequence turn-off stars. fit oblate triaxial broken power-law models data, found a `best-fit' oblateness 0.5~100pc, after accounting for (known) contribution Poisson uncertainties. The fractional RMS deviation actual distribution any smooth, parameterized model is >~40%: hence, highly structured....
In this paper we present the MOSFIRE Deep Evolution Field (MOSDEF) survey. The MOSDEF survey aims to obtain moderate-resolution (R=3000-3650) rest-frame optical spectra (~3700-7000 Angstrom) for ~1500 galaxies at 1.37<z<3.80 in three well-studied CANDELS fields: AEGIS, COSMOS, and GOODS-N. Targets are selected redshift intervals: 1.37<z<1.70, 2.09<z<2.61, 2.95<z<3.80, down fixed H_AB (F160W) magnitudes of 24.0, 24.5 25.0, respectively, using photometric spectroscopic catalogs from 3D-HST We...