A5078455868- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Astronomy and Astrophysical Research
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Scientific Research and Discoveries
- Astronomical Observations and Instrumentation
- Dark Matter and Cosmic Phenomena
- Astro and Planetary Science
- Cosmology and Gravitation Theories
- Astrophysics and Cosmic Phenomena
- Advanced Data Storage Technologies
- Astrophysical Phenomena and Observations
- History and Developments in Astronomy
- Computational Physics and Python Applications
- Cloud Computing and Resource Management
- Impact of Light on Environment and Health
- Geophysics and Gravity Measurements
- CCD and CMOS Imaging Sensors
- Adaptive optics and wavefront sensing
- Data Mining Algorithms and Applications
- Science Education and Pedagogy
- Historical Geography and Cartography
- Caching and Content Delivery
- Particle physics theoretical and experimental studies
University of California, Merced
2021-2025
University of California, Davis
2018-2022
University of Michigan
2014-2018
Society of Actuaries
2015
University College London
2015
University of Washington
2008-2013
McMaster University
2008
Institute for Advanced Study
2008
University of Central Lancashire
2008
Abstract We describe a public data release of the FIRE-2 cosmological zoom-in simulations galaxy formation (available at http://flathub.flatironinstitute.org/fire ) from Feedback In Realistic Environments (FIRE) project. achieve parsec-scale resolution to explicitly model multiphase interstellar medium while implementing direct models for stellar evolution and feedback, including winds, core-collapse Type Ia supernovae, radiation pressure, photoionization, photoelectric heating. complete...
ABSTRACT Increasingly, uncertainties in predictions from galaxy formation simulations (at sub-Milky Way masses) are dominated by stellar evolution inputs. In this paper, we present the full set of updates Feedback Realistic Environment (FIRE)-2 version FIRE project code, to next version, FIRE-3. While transition FIRE-1 FIRE-2 focused on improving numerical methods, here update tracks used determine feedback inputs, e.g. mass-loss (O/B and AGB), spectra (luminosities ionization rates),...
ABSTRACT As they grow, galaxies can transition from irregular/spheroidal with ‘bursty’ star formation histories (SFHs), to discy smooth SFHs. But even in simulations, the direct physical cause of such transitions remains unclear. We therefore explore this a large suite numerical experiments re-running portions cosmological simulations widely varied physics, further validated existing FIRE simulations. show that gas supply, cooling/thermodynamics, model, Toomre scale, galaxy dynamical times,...
We study Milky Way kinematics using a sample of 18.8 million main-sequence stars with r<20 and proper-motion measurements derived from SDSS POSS astrometry, including ~170,000 radial-velocity the spectroscopic survey. Distances to are determined photometric parallax relation, covering distance range ~100 pc 10 kpc over quarter sky at high Galactic latitudes (|b|>20 degrees). find that in region defined by 1 <Z< 5 3 <R< 13 kpc, rotational velocity for disk smoothly decreases, all three...
The separation of the Milky Way disk into a thin and thick component is supported by differences in spatial, kinematic metallicity distributions their stars. These have led to view that formed early via cataclysmic event constitutes fossil evidence hierarchical growth Way. We show here, using N-body simulations, how double-exponential vertical structure, with stellar populations displaying similar dichotomies can arise purely through internal evolution. In this picture, stars migrate...
We examine the present-day total stellar-to-halo mass (SHM) ratio as a function of halo for new sample simulated field galaxies using fully cosmological, ΛCDM, high-resolution SPH + N-body simulations. These simulations include an explicit treatment metal line cooling, dust and self-shielding, H2-based star formation (SF), supernova-driven gas outflows. The 18 halos have masses ranging from few times 108 to nearly 1012 M☉. At z = 0, our baryon content morphology typical galaxies. Over...
The ultra-faint dwarf galaxy Reticulum 2 (Ret 2) was recently discovered in images obtained by the Dark Energy Survey. We have observed four brightest red giants Ret at high spectral resolution using Michigan/Magellan Fiber System. present detailed abundances for as many 20 elements per star, including 12 heavier than Fe group. confirm previous detection of levels r-process material (mean [Eu/Fe]=+1.69+/-0.05) found three these stars [Fe/H]=-2.88+/-0.10). closely match pattern well-studied...
We describe the construction of a highly reliable sample approximately 7,000 optically faint periodic variable stars with light curves obtained by asteroid survey LINEAR across 10,000 sq.deg northern sky. Majority these variables have not been cataloged yet. The flux limit is several magnitudes fainter than for most other wide-angle surveys; photometric errors range from ~0.03 mag at $r=15$ to ~0.20 r=18. Light include on average 250 data points, collected over about decade. Using SDSS-based...
With Gaia Data Release 2, the astronomical community is entering a new era of multidimensional surveys Milky Way. This phase-space view our Galaxy demands tools for comparing observations to simulations Milky-Way-mass galaxies in cosmological context, test physics both dark matter and galaxy formation. We present ananke, framework generating synthetic from high-resolution baryonic simulations, use it generate suite resembling DR2 data structure, magnitude limits, observational errors. three...
While many tensions between Local Group (LG) satellite galaxies and LCDM cosmology have been alleviated through recent cosmological simulations, the spatial distribution of satellites remains an important test physical models versus numerical disruption in simulations. Using FIRE-2 zoom-in baryonic we examine radial distributions with Mstar > 10^5 Msun around 8 isolated Milky Way- (MW) mass host 4 hosts LG-like pairs. We demonstrate that these simulations resolve survival destruction >~...
The disc structure of the Milky Way is marked by a chemical dichotomy, with high-alpha and low-alpha abundance sequences, traditionally identified geometric thick thin discs. This identification aided old ages stars, lower average ones. Recent large scale surveys such as APOGEE have provided wealth data on this structure, including showing that an discs not exact, but origin dichotomy has remained unclear. Here we demonstrate arises naturally if early gas-rich fragments, leading to some...
ABSTRACT We develop a hybrid model of galactic chemical evolution that combines multiring computation enrichment with prescription for stellar migration and the vertical distribution populations informed by cosmological hydrodynamic disc galaxy simulation. Our fiducial adopts empirically motivated forms star formation law history, gradient in outflow mass loading tuned to reproduce observed metallicity gradient. With this approach, reproduces many striking qualitative features Milky Way...
Abstract Stars that formed with an initial mass of over 50 M ⊙ are very rare today, but they thought to be more common in the early Universe. The fates those early, metal-poor, massive stars highly uncertain. Most expected directly collapse black holes, while some may explode as a result rotationally powered engines or pair-creation instability. We present chemical abundances J0931+0038, nearby low-mass star identified follow-up SDSS-V Milky Way Mapper, which preserves signature unusual...
We use high resolution Hydro$+$N-Body cosmological simulations to compare the assembly and evolution of a small field dwarf (stellar mass ~ 10$^{6-7}$ M$\odot$, total 10$^{10}$ M$\odot$ in $\Lambda$ dominated CDM 2keV WDM cosmologies. find that star formation (SF) model is reduced delayed by 1-2 Gyr relative model, independently details SF feedback. Independent DM but proportionally efficiency, gas outflows lower central density through `dynamical heating', such all realizations have...
We present evidence that isolated growing discs, subject to internal spiral perturbations, thicken due both heating \emph{and} radial migration. show this by demonstrating the thickness and vertical velocity dispersions of coeval stars depend on their age as well change in radii. While disc thickens processes, we find induces only a minor amount flaring. further demonstrate consequences such thickening structural properties stellar populations they qualitatively agree with recent studies...
ABSTRACT We present results from spectroscopic observations with the Michigan/ Magellan Fiber System (M2FS) of 147 stellar targets along line sight to newly discovered “ultrafaint” systems Tucana 2 (Tuc 2) and Grus 1 (Gru 1). Based on simultaneous estimates velocity stellar-atmospheric parameters, we identify 8 7 stars as probable members Tuc Gru 1, respectively. Our sample for is sufficient resolve an internal dispersion <?CDATA ${8.6}_{-2.7}^{+4.4}$?> <?MML <mml:math> <mml:msubsup>...
Kinematic studies of disk galaxies, using individual stars in the Milky Way or statistical global kinematics over time, provide insight into how disks form and evolve. We use a high-resolution, cosmological zoom-simulation Way-mass galaxy h277 to tie together local evolution time. The present-day stellar age-velocity relationship (AVR) is nearly identical that analogous solar-neighborhood measurement Way. A crucial element this success simulation's dynamically cold multi-phase ISM, which...
We present the first measurement of lifetimes Giant Molecular Clouds (GMCs) in cosmological simulations at $z = 0$, using Latte suite FIRE-2 Milky Way-mass galaxies. track GMCs with total gas mass $\gtrsim 10^5$ M$_\odot$ high spatial ($\sim1$ pc), ($7100$ M$_{\odot}$), and temporal (1 Myr) resolution. Our simulated are consistent distribution masses for massive Way nearby find GMC $5-7$ Myr, or 1-2 freefall times, on average, less than 2$\%$ clouds living longer 20 Myr. decreasing...
ABSTRACT We study the kinematics of stars both at their formation and today within 14 Milky Way (MW)-mass galaxies from FIRE-2 cosmological zoom-in simulations. quantify relative importance disc settling post-formation dynamical heating. identify three eras: a Pre-Disc Era (typically ≳ 8 Gyr ago), when formed on dispersion-dominated orbits; an Early-Disc (≈8–4 started to form rotation-dominated orbits but with high velocity dispersion, σform; Late-Disc (≲ 4 low σform. σform increased time...
ABSTRACT Recent analysis of the SDSS-III/Apache Point Observatory Galactic Evolution Experiment (APOGEE) Data Release 12 stellar catalog has revealed that Milky Way’s (MW) metallicity distribution function (MDF) changes shape as a radius, transitioning from being negatively skewed at small Galactocentric radii to positively large radii. Using high-resolution, N -body+SPH simulation, we show changing skewness arises radial migration—metal-rich stars form in inner disk and subsequently migrate...
We present robust constraints from the Sloan Digital Sky Survey (SDSS) on shape and distribution of dark matter halo within Milky Way (MW). Using number density kinematics SDSS stars, we probe to heliocentric distances exceeding 10 kpc galactocentric 20 kpc. Our analysis utilizes Jeans equations generate two-dimensional acceleration maps throughout volume; this approach is thoroughly tested a cosmologically derived N-body+SPH simulation MW-like galaxy. show that known accelerations...
Pressure balance plays a central role in models of the interstellar medium (ISM), but whether and how pressure is realized realistic multiphase ISM not yet well understood. We address this question using set FIRE-2 cosmological zoom-in simulations Milky Way-mass disk galaxies, which self-consistently shaped by gravity, cooling, stellar feedback. analyze gravity determines vertical profile as total partitioned between different phases components (thermal, dispersion/turbulence, bulk flows)....
Giant molecular clouds (GMCs) are well-studied in the local Universe, however, exactly how their properties vary during galaxy evolution is poorly understood due to challenging resolution requirements, both observational and computational. We present first time-dependent analysis of giant a Milky Way-like an LMC-like dwarf FIRE-2 (Feedback In Realistic Environments) simulation suite, which have sufficient predict bulk GMCs cosmological formation self-consistently. show explicitly that...
We use FIRE-2 simulations to examine 3-D variations of gas-phase elemental abundances [O/H], [Fe/H], and [N/H] in 11 Milky Way (MW) M31-mass galaxies across their formation histories at $z \leq 1.5$ ($t_{\rm lookback} 9.4$ Gyr), motivated by characterizing the initial conditions stars for chemical tagging. Gas within $1$ kpc disk midplane is vertically homogeneous $\lesssim 0.008$ dex all 1.5$. find negative radial gradients (metallicity decreases with galactocentric radius) times, which...