A5039259392- Galaxies: Formation, Evolution, Phenomena
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Astronomy and Astrophysical Research
- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Astro and Planetary Science
- Atmospheric Ozone and Climate
- Radio Astronomy Observations and Technology
- Solar and Space Plasma Dynamics
- Spectroscopy and Laser Applications
- Geophysics and Gravity Measurements
- Adaptive optics and wavefront sensing
- Ionosphere and magnetosphere dynamics
- Photocathodes and Microchannel Plates
- Scientific Research and Discoveries
- Cosmology and Gravitation Theories
- History and Developments in Astronomy
- Atomic and Molecular Physics
- Calibration and Measurement Techniques
- Laser-induced spectroscopy and plasma
- CCD and CMOS Imaging Sensors
- Magnetic confinement fusion research
University of Massachusetts Amherst
2015-2024
Northrop Grumman (United States)
2024
Princeton University
1998-2013
University of Massachusetts Boston
2004-2011
Fermi National Accelerator Laboratory
2009
University of Chicago
2009
University of Massachusetts System
2008
Centre National de la Recherche Scientifique
2000
University of Wisconsin–Madison
1994-1998
Washburn University
1997
We analyze the physical conditions of cool, photoionized (T $\sim 10^4$ K) circumgalactic medium (CGM) using COS-Halos suite gas column density measurements for 44 gaseous halos within 160 kpc $L \sim L^*$ galaxies at $z 0.2$. These data are well described by simple photoionization models, with highly ionized (n$_{\rm HII}$/n$_{\rm H} \gtrsim 99\%$) extragalactic ultraviolet background (EUVB). Scaling estimates virial radius, R$_{\rm vir}$, we show that ionization state (tracked...
The circumgalactic medium (CGM) is fed by galaxy outflows and accretion of intergalactic gas, but its mass, heavy element enrichment, relation to properties are poorly constrained observations. In a survey the outskirts 42 galaxies with Cosmic Origins Spectrograph onboard Hubble Space Telescope, we detected ubiquitous, large (150 kiloparsec) halos ionized oxygen surrounding star-forming galaxies, find much less around little or no star formation. This CGM contains substantial mass elements...
We present the design and methods of COS-Halos survey, a systematic investigation gaseous halos 44 z = 0.15-0.35 galaxies using background QSOs observed with Cosmic Origins Spectrograph aboard Hubble Space Telescope. This survey has yielded 39 spectra z_em ~ 0.5 S/N 10-15 per resolution element. The QSO sightlines pass within 150 physical kpc galaxies, which span early late types over stellar mass log M* / Msun= 9.5 - 11.5. find that CGM exhibits strong HI, averaging 1 Ang in Lya equivalent...
We present the equivalent width and column density measurements for low intermediate ionization states of circumgalactic medium (CGM) surrounding 44 low-z, L ≈ L* galaxies drawn from COS-Halos survey. These are derived far-UV transitions observed in HST/COS Keck/HIRES spectra background quasars within an impact parameter R < 160 kpc to targeted galaxies. The data show significant metal-line absorption 33 galaxies, including quiescent systems, revealing common occurrence a cool (T 104–105 K),...
We analyze new far-ultraviolet spectra of 13 quasars from the z~0.2 COS-Halos survey that cover HI Lyman limit 14 circumgalactic medium (CGM) systems. These data yield precise estimates or more constraining limits than previous measurements on column densities NHI. then apply a Monte-Carlo Markov Chain approach 32 systems to estimate metallicity cool (T~10^4K) CGM gas gives rise low-ionization state metal lines, under assumption photoionization equilibrium with extragalactic UV background....
We report new observations of circumgalactic gas from the COS-Dwarfs survey, a systematic investigation gaseous halos around 43 low-mass z ⩽ 0.1 galaxies using background QSOs observed with Cosmic Origins Spectrograph. From projected one-dimensional and two-dimensional distribution C iv absorption, we find that is detected out to ≈100 kpc (corresponding roughly ≈0.5 Rvir) host galaxies. The absorption strength falls off radially as power law, beyond Rvir, no above our sensitivity limit...
The total contribution of diffuse halo gas to the galaxy baryon budget strongly depends on its dominant ionization state. In this paper, we address physical conditions in highly ionized circumgalactic medium (CGM) traced by OVI absorption lines observed COS-Halos spectra. We analyze ionic column densities, absorption-line widths and relative velocities, along with ratios NV/OVI for 39 fitted Voigt profile components OVI. compare these quantities predictions given a wide range models....
Far-UV echelle spectroscopy of the radio-quiet QSO H1821+643 (zem=0.297), obtained with Space Telescope Imaging Spectrograph (STIS) at approximately 7 km s-1 resolution, reveals four definite O vi absorption-line systems and one probable absorber 0.15<zabs<0.27. The absorbers are located near galaxies highly displaced from quasar in redshift; these likely intervening unrelated to background QSO. In case strong system zabs=0.22497, multiple components detected Si iii as well H i Lyman series...
Using high-resolution UV spectra of 16 low-z QSOs, we study the physical conditions and statistics O VI absorption in IGM at z < 0.5. We identify 51 intervening (z_{abs} << z_{QSO}) systems comprised 77 individual components, find 14 "proximate" ~ containing 34 components. For [components] with rest-frame equivalent width W_{r} > 30 mA, number absorbers per unit redshift dN/dz = 15.6(+2.9/-2.4) [21.0(+3.2/-2.8)], this decreases to 0.9(+1.0/-0.5) [0.3(+0.7/-0.3)] for 300 mA. The...
We analyzed absorption features arising from interstellar neutral carbon that appeared in the UV spectra of 89 stars recorded highest resolution echelle modes Space Telescope Imaging Spectrograph on board Hubble so we could determine relative populations collisionally excited fine-structure levels atom's electronic ground state. From this information, combination with molecular hydrogen rotation temperatures, derive distribution thermal pressures diffuse, cold medium (CNM). find a lognormal...
We assess the metal content of cool (∼104 K) circumgalactic medium (CGM) about galaxies at z ≲ 1 using an H i-selected sample 28 Lyman limit systems (LLS; defined here as absorbers with 16.2 log NH i 18.5) observed in absorption against background QSOs by Cosmic Origins Spectrograph on board Hubble Space Telescope. The selection avoids metallicity biases inherent many previous studies low-redshift CGM. compare column densities weakly ionized species (e.g., O ii, Si Mg ii) to strongest...
Outflowing winds of multiphase plasma have been proposed to regulate the buildup galaxies, but key aspects these outflows not probed with observations. Using ultraviolet absorption spectroscopy, we show that "warm-hot" at 10^{5.5} K contains 10-150 times more mass than cold gas in a poststarburst galaxy wind. This wind extends distances >68 kiloparsecs, and least some portion it will escape. Moreover, kinematical correlation warm-hot phases indicates is related interaction matter hotter...
We report new observations of circumgalactic gas in the halos early-type galaxies (ETGs) obtained by COS-Halos Survey with Cosmic Origins Spectrograph on board Hubble Space Telescope. find that detections H i surrounding ETGs are typically as common and strong around star-forming galaxies, implying total mass material is comparable two populations. For ETGs, covering fraction for absorption above 1016 cm−2 ∼40%–50% within ∼150 kpc. Line widths kinematics detected show it to be cold (T ≲ 105...
We used the Space Telescope Imaging Spectrograph (STIS) with its smallest entrance aperture (003 wide slit) and highest resolution echelle gratings (E140H E230H) to record interstellar absorption features for 10 different multiplets of neutral carbon at a resolving power λ/Δλ = 200,000 in UV spectra 21 early-type stars. Our objective was measure amount C I each three fine-structure levels ground electronic state, so that we could determine thermal pressures absorbing gas how much they vary...
To study the nature of low-z Lyα absorbers in spectra QSOs, we have obtained high signal-to-noise ratio (S/N) UV H1821+643 (zem = 0.297) and PG 1116+215 0.177) with Goddard High-Resolution Spectrograph on Hubble Space Telescope. The minimum S/Ns ~70-100 3 σ limiting equivalent widths 50-75 mÅ at a resolution ~150 km s-1. Excluding lines within 3000 s-1 zem, detect 26 Wr > 50 toward 13 (comparable to observed 3C 273 by Morris et al.), which implies density 102 ± 16 per unit redshift for zabs...
Observations obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) have been used to determine column densities of D I, N and O I along seven sight lines that probe local interstellar medium (LISM) at distances from 37 179 pc. Five are within Local Bubble, two penetrate surrounding H wall. Reliable values N(H I) were determined for five Hubble Space Telescope (HST) data, International (IUE) published Extreme (EUVE) measurements. The weighted mean I/H these is (1.52 ± 0.08) × 10-5...
We present Far Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph (STIS) observations of interstellar ultraviolet absorption lines in the Galactic high-velocity cloud Complex C Intermediate Velocity Arch (IV Arch) direction quasar PG 1259+593 (l=120,b=+58 deg). Absorption from CII, NI, NII, OI, AlII, SiII, PII, SII, ArI, FeII, FeIII are used to study atomic abundances these two halo clouds at V_LSR=-130 km/s (Complex C) V_LSR=-55 Arch). The OI/HI ratio...
We present evidence that high-velocity cloud (HVC) complex C is a low-metallicity gas plunging toward the disk and beginning to interact with ambient surrounds Milky Way. This begins new high-resolution (7 km s-1 FWHM) echelle spectrum of 3C 351 obtained Space Telescope Imaging Spectrograph (STIS). lies behind low-latitude edge C, provides accurate measurements O I, Si II, Al Fe III absorption lines at velocity C; N S IV, IV are not detected 3 σ significance in proper. However, as well II...
We study the physical conditions, elemental abundances, and kinematics of high-velocity clouds (HVCs) along sight lines toward active galaxies HE0226-4110 PG0953+414 using Hubble Space Telescope Imaging Spectrograph Far Ultraviolet Spectroscopic Explorer data. Our observations reveal multiple components HVC absorption in HI, CII, CIII, CIV, OVI, SiII, SiIII, SiIV both directions. investigate whether photoionization by extragalactic background radiation or escaping Milky Way can explain...
We present Far Ultraviolet Spectroscopic Explorer and Hubble Space Telescope observations of high-, intermediate-, low-ion absorption in high-velocity cloud (HVC) Complex C along the lines sight toward five active galaxies. Our purpose is to investigate idea that surrounded by an envelope highly ionized material, arising from interaction between a hot surrounding medium. measure column densities high-ion compare kinematics low-, high-ionization gas lines. find all cases, H I O VI components...
We present a study of the Lyαforest at z<0.4 from which we conclude that least 20% total baryons in universe are located highly-ionized gas traced by broad Lyαabsorbers. The cool photoionized low-z intergalactic medium (IGM) probed narrow Lyαabsorbers contains about 30% baryons. further find ratio to is higher than 1.513.2, with column density distribution f(N_HI) \propto N^-β_HI. For (b<40 km/s) absorbers β= 1.76+/-0.06. Doppler parameter b low redshift implies two populations: and...
To probe the distribution and physical characteristics of interstellar gas at temperatures T ~ 3e5 K in disk Milky Way, we have used Far Ultraviolet Spectroscopic Explorer (FUSE) to observe absorption lines OVI toward 148 early-type stars situated distances 1 kpc. After subtracting off a mild excess arising from Local Bubble, combining our new results with earlier surveys OVI, eliminating that show conspicuous localized X-ray emission, find an average mid-plane density n_0 = 1.3e-8 cm^-3....
We present UV and optical observations from the Cosmic Origins Spectrograph on Hubble Space Telescope Keck of a z = 0.27395 Lyman limit system (LLS) seen in absorption against QSO PG1630+377. detect H i with log N(H i) 17.06 ± 0.05 as well Mg ii, C iii, Si O vi this system. The column densities are readily explained if is multi-phase system, intermediate low ions arising very metallicity ([Mg/H] −1.71 0.06) photoionized gas. identify via spectroscopy Large Binocular imaging 0.3 L*...
We present high signal-to-noise optical spectra for 67 low-redshift (0.1 < z 0.4) galaxies that lie within close projected distances (5 kpc rho 150 kpc) of 38 background UV-bright QSOs. The Keck LRIS and Magellan MagE data presented here are part a survey aims to construct statistically sampled map the physical state metallicity gaseous galaxy halos using Cosmic Origins Spectrograph (COS) on Hubble Space Telescope (HST). provide detailed description reduction subsequent spectral analysis...