A5049471465- Astronomy and Astrophysical Research
- Stellar, planetary, and galactic studies
- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Gamma-ray bursts and supernovae
- Cosmology and Gravitation Theories
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Scientific Research and Discoveries
- Astrophysics and Cosmic Phenomena
- History and Developments in Astronomy
- Adaptive optics and wavefront sensing
- Astro and Planetary Science
- Animal Ecology and Behavior Studies
- Wildlife Ecology and Conservation
- Dark Matter and Cosmic Phenomena
- Calibration and Measurement Techniques
- Radio Astronomy Observations and Technology
- Geophysics and Gravity Measurements
- Phase Equilibria and Thermodynamics
- CCD and CMOS Imaging Sensors
- Solar and Space Plasma Dynamics
- Statistical and numerical algorithms
- Zoonotic diseases and public health
- Species Distribution and Climate Change
Cheikh Anta Diop University
2025
Space Telescope Science Institute
2014-2023
Johns Hopkins University
1986-2023
Animal and Plant Health Inspection Service
1998-2020
United States Department of Agriculture
2020
Michigan Science Center
1996-2019
Medical University of South Carolina
2015-2017
Tennessee State University
2012-2015
MBDA (Germany)
2012
Institute for Advanced Study
1983-2009
This special issue of the Astrophysical Journal Letters is dedicated to presenting initial results from Great Observatories Origins Deep Survey (GOODS) that are primarily, but not exclusively, based on multiband imaging data obtained with Hubble Space Telescope and Advanced Camera for Surveys (ACS). The survey covers roughly 320 arcmin2 in ACS F435W, F606W, F814W, F850LP bands, divided into two well-studied fields. Existing deep observations Chandra X-Ray Observatory ground-based facilities...
We present a new model for computing the effects of dust on integrated spectral properties galaxies, based an idealized description main features interstellar medium (ISM). The includes ionization H II regions in interiors dense clouds which stars form and influence finite lifetime these absorption radiation. compute production emission lines continuum radiation subsequent transfer line surrounding I ambient ISM. This enables us to interpret simultaneously all observations...
We consider a picture in which disc galaxies formed from collapsing gas extended haloes of dark material. It is assumed that these systems were produced by hierarchical clustering and endowed with their angular momenta tidal torques. In order to test the theory, we have developed some models determine structure terms observable properties discs. A comparison sample 25 leads following conclusions: (1) Collapse factors 10 or more halo-to-disc mass ratios five are required explain rapid...
The Spitzer-COSMOS survey (S-COSMOS) is a Legacy program (Cycles 2+3) designed to carry out uniform deep of the full 2 sq deg COSMOS field in all seven Spitzer bands (3.6, 4.5, 5.6, 8.0, 24.0, 70.0, 160.0 u). This paper describes parameters, mapping strategy, data reduction procedures, achieved sensitivities date, and complete set for future reference. We show that observed infrared backgrounds S-COSMOS are within 10% predicted background levels. fluctuations at 24u have been measured do not...
The Wide Field Planetary Camera 2 of the Hubble Space Telescope has been used to obtain high-resolution images NGC 4038/4039 that go roughly 3 mag deeper in V than previous observations made during cycle 2. These new allow us measure luminosity functions (LFs) clusters and stars over a range 8 (-14 < MV -6). To first order, LF is power law, with exponent α = -2.12 ± 0.04. However, using variety different techniques decouple cluster stellar LFs, which overlap -9 ≲ -6, we find an apparent bend...
view Abstract Citations (681) References (78) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The kinematic properties of faint elliptical galaxies. Davies, R. L. ; Efstathiou, G. Fall, S. M. Illingworth, Schechter, P. Rotation curves and velocity dispersion profiles are obtained for 11 galaxies, together with central dispersions an additional six ellipticals. It is noted that ellipticals rotate more rapidly than bright ellipticals, almost as predicted by...
The Cosmic Evolution Survey (COSMOS) was initiated with an extensive allocation (590 orbits in Cycles 12-13) using the Hubble Space Telescope (HST) for high resolution imaging. Here we review characteristics of HST imaging Advanced Camera Surveys (ACS) and parallel observations NICMOS WFPC2. A square field (1.8$\sq$\deg) has been imaged single-orbit ACS I-F814W exposures 50% completeness sources 0.5\arcsec diameter at I$_{AB} $ = 26.0 mag. is a key part COSMOS survey, providing very...
We have measured the rest--frame lambda~1500 Ang comoving specific luminosity density of star--forming galaxies at redshift 3.5
view Abstract Citations (431) References (83) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Structure of Young Star Clusters in the Large Magellanic Cloud Elson, Rebecca A. W. ; Fall, S. Michael Freeman, Kenneth C. authors present surface brightness profiles, based on star counts and aperture photometry, for 10 rich young clusters Cloud. To investigate dynamical evolution clusters, they derive mass-to-light ratios from stellar population models. They...
view Abstract Citations (516) References (53) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A theory for the origin of globular clusters. Fall, S. M. ; Rees, J. The authors present a clusters during collapse protogalaxy. thermal instability promotes development two-phase structure in gas when cooling time is comparable to free-fall time. hot component, which remains near virial temperature, compresses cold component into discrete clouds with temperatures...
We study the stellar angular momentum of thousands galaxies in Illustris cosmological simulation, which captures gravitational and gas dynamics within galaxies, as well feedback from stars black holes. find that simulated matches observations well, particular two distinct relations are found for late-type versus early-type galaxies. The relation corresponds to value expected full conservation specific generated by tidal torques. retention only ∼30% that, but we those with low at z = 0...
The Wide Field Infrared Survey Telescope (WFIRST) is a 2.4m space telescope with 0.281 deg^2 field of view for near-IR imaging and slitless spectroscopy coronagraph designed > 10^8 starlight suppresion. As background information Astro2020 white papers, this article summarizes the current design anticipated performance WFIRST. While WFIRST does not have UV imaging/spectroscopic capabilities Hubble Space Telescope, wide surveys hundreds times more efficient. Some most ambitious multi-cycle...
We present a series of simple, largely analytical models to compute the effects disruption on mass function star clusters. Our calculations include evaporation by two-body relaxation and gravitational shocks loss stellar evolution. find that, for wide variety initial conditions, develops turnover or peak after 12 Gyr, this is remarkably close observed globular clusters, at M_p = 2 10^5 solar masses. Below peak, evolution dominated relaxation, always tail form psi(M) const, reflecting that...
We determine the mass function of young star clusters in merging galaxies known as "Antennae" (NGC 4038/9) from deep images taken with Wide Field Planetary Camera 2 on refurbished Hubble Space Telescope. This is accomplished by means reddening-free parameters and a comparison stellar population synthesis tracks to estimate intrinsic luminosity age, hence mass, each cluster. find that (with ages less, similar160 Myr) well represented power law form psi&parl0;M&parr0;~M-2 over range 104...
view Abstract Citations (327) References (75) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Lyman-Alpha Emission from Galaxies Charlot, Stephane ; Fall, S. Michael We use new models of stellar population synthesis to compute the Lyα emission galaxies with different star formation histories and initial mass functions. The include all phases evolution recent advances in theories interiors atmospheres. find that dust-free would have equivalent widths 50-200 Å,...
Hubble Space Telescope images of high-redshift galaxies selected via color and photometric redshifts are used to examine the size axial ratio distribution as a function redshift at look-back times t > 8 Gyr. These parameters measured rest-frame UV wavelengths (1200 Å < λ 2000 Å) on with resolution less than 0.8 kpc. Galaxy radii found scale approximately parameter H-1(z). This is in accord theoretical expectation that typical sizes luminous parts should track expected evolution virial radius...
view Abstract Citations (335) References (80) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Chemical evolution of the galactic disk with radial gas flows. Lacey, C. G. ; Fall, S. M. Models are presented for chemical disc inflows at a velocity constant time, but that may vary galactocentric radius. The models include infall metal-free from outside rate decaying exponentially star formation varies as surface density layer to power m, m = 1 or 2, and in some...
We investigate a set of coupled equations that relates the stellar, gaseous, chemical, and radiation contents universe averaged over whole population galaxies. Using as input available data from quasar absorption-line surveys, optical imaging redshift COBE DIRBE FIRAS extragalactic infrared background measurements, we obtain solutions for cosmic histories stars, interstellar gas, heavy elements, dust, stars dust in Our reproduce remarkably well wide variety observations were not used input....
We compile a new sample of 115 nearby, non-Seyfert galaxies spanning wide range star formation activities, from starburst to nearly dormant, based on ultraviolet (UV) observations with various satellites. combine these infrared (IR) study the relation between ratio total far-IR UV luminosities and spectral slope (the `IRX-UV' relation). show that, at fixed slope, quiescent star-forming in our have systematically lower than galaxies. The strengths indices sensitive history, such as 4000 A...
We present results of our large area survey for z'-band dropout galaxies at z = 7 in a 1568 arcmin2 sky covering the SDF and GOODS-N fields. Combining ultra-deep Subaru/Suprime-Cam z'- y-band (λeff 1 μm) images with legacy data Subaru Hubble Space Telescope, we have identified 22 bright z-dropout down to y 26, one which has spectroscopic redshift 6.96 determined from Lyα emission. The luminosity function yields best-fit Schechter parameters ϕ* 0.69+2.62−0.55 × 10−3 Mpc−3, M*UV −20.10 ± 0.76...
We determine the age distribution of star clusters in Antennae galaxies (NGC 4038/9) for two mass-limited samples (M > 3 × 104 M☉ and M 2 105 M☉). This is based on integrated broadband UBVI narrowband Hα photometry from deep images taken with Hubble Space Telescope. find that declines steeply, approximately as dN/dτ ∝ τ-1. The median ~107 yr, which we interpret evidence rapid disruption ("infant mortality"). It very likely most young are not gravitationally bound were disrupted near times...
view Abstract Citations (279) References (51) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Obscuration of Quasars by Dust in Damped Lyman-Alpha Systems Fall, S. M. ; Pei, Yichuan C. We present a largely analytical method to compute the obscuration quasars dust damped Lyα absorption systems. The inputs required our are observed luminosity function and typical dust-to-gas ratio empirical distribution H I column densities use inferred from reddening...
We present new U, B, V, and I images of the prototypical merger remnant NGC 7252 obtained with WFPC2 instrument Hubble Space Telescope. The photometry reaches about 3 mag deeper than previous observations WF/PC1 we detect 499 cluster candidates, most them previously undiscovered. can distinguish three populations star clusters. confirm existence a very luminous, blue population clusters narrow range in color. Comparisons Bruzual & Charlot (1996, preparation) models incorporating Salpeter...
Motivated by new kinematic data in the outer parts of early-type galaxies (ETGs), we re-examine angular momentum (AM) all galaxy types. We present methods for estimating specific AM j, focusing on ETGs, to derive relations between stellar j_* and mass M_* (after Fall 1983). perform analyses 8 out ~10 R_e, finding that at 2 R_e are sufficient estimate total j_*. Our results contravene suggestions ellipticals (Es) harbor large reservoirs hidden from transport major mergers. carry a j_*-M_*...