A5026197430- Galaxies: Formation, Evolution, Phenomena
- Stellar, planetary, and galactic studies
- Astrophysics and Star Formation Studies
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Gamma-ray bursts and supernovae
- Scientific Research and Discoveries
- Cosmology and Gravitation Theories
- Pulsars and Gravitational Waves Research
- Astrophysics and Cosmic Phenomena
- Adaptive optics and wavefront sensing
- Astrophysical Phenomena and Observations
- CCD and CMOS Imaging Sensors
- Radio Astronomy Observations and Technology
- History and Developments in Astronomy
- Analog and Mixed-Signal Circuit Design
- Sensor Technology and Measurement Systems
- Advancements in Semiconductor Devices and Circuit Design
- Calibration and Measurement Techniques
- Experimental Learning in Engineering
- Atomic and Molecular Physics
- Semiconductor Lasers and Optical Devices
- Sparse and Compressive Sensing Techniques
- Photocathodes and Microchannel Plates
- Diamond and Carbon-based Materials Research
Maria Mitchell Association
2001-2024
Willamette University
2016
State Street (United States)
2016
University of Hawaii System
1989-2015
University of Cambridge
2009-2014
Institute of Astronomy
2010-2012
University of California, San Diego
2006-2010
University of Puget Sound
2000
We report the discovery of deuterium absorption in very metal-poor ([Fe/H] = -2.88) damped Lyman-alpha system at z_abs 3.06726 toward QSO SDSS J1358+6522. On basis 13 resolved D I lines and damping wings H Lyman alpha transition, we have obtained a new, precise measure primordial abundance deuterium. Furthermore, to bolster present statistics precision D/H measures, reanalyzed all known absorption-line systems that satisfy set strict criteria. adopted blind analysis strategy (to remove human...
We report the discovery and analysis of most metal-poor damped Lyman-alpha (DLA) system currently known, which also displays Lyman series absorption lines neutral deuterium. The average [O/H] abundance this is = -2.804 +/- 0.015, includes an component with -3.07 0.03. Despite unfortunate blending many weak D I lines, we a precise measurement deuterium system. Using six highest quality self-consistently analyzed measures D/H in DLAs, tentative evidence for subtle decrease increasing...
In this paper we analyze the kinematics, chemistry, and physical properties of a sample most metal-poor damped Lyman-alpha systems (DLAs), to uncover their links modern-day galaxies. We present evidence that DLA population as whole exhibits `knee' in relative abundances alpha-capture Fe-peak elements when metallicity is [Fe/H] ~ -2.0, assuming Zn traces build-up elements. respect, chemical evolution DLAs clearly different from experienced by Milky Way halo stars, but resembles dwarf...
Abstract We present a high-resolution analysis of the host galaxy fast radio burst (FRB) 190608, an SB(r)c at z = 0.11778 (hereafter HG 190608), to dissect its local environment and contributions FRB properties. Our Hubble Space Telescope Wide Field Camera 3 ultraviolet visible light image reveals that subarcsecond localization 190608 is coincident with knot star formation (Σ SFR 1.5 × 10 −2 M ⊙ yr −1 kpc ) in northwest spiral arm 190608. Using H β emission our Keck Cosmic Web Imager...
Abstract We present Keck Cosmic Web Imager Ly α integral field spectroscopy of the fields surrounding 14 damped absorbers (DLAs) at z ≈ 2. Of these DLAs, nine have high metallicities ([M/H] > − 0.3), and four those feature a CO-emitting galaxy an impact parameter ≲30 kpc. Our search reaches median line flux sensitivities ∼2 × 10 −17 erg s −1 cm −2 over apertures ∼6 kpc out to parameters ∼50 recover three known -emitting H i -selected galaxies in our sample. In addition, we find two...
We present high resolution observations of an extremely metal-poor damped Lyman-alpha system, at z_abs = 2.3400972 in the spectrum QSO J0035-0918, exhibiting abundance pattern consistent with model predictions for supernova yields Population III stars. Specifically, this DLA has [Fe/H] -3.04, shows a clear `odd-even' effect, and is C-rich [C/Fe] +1.53, factor about 20 greater than reported any other system. In analogy to carbon-enhanced stars Galactic halo (with > +1.0), first case determine...
We present the chemical abundance measurements of first large, medium-resolution, uniformly selected damped Lyman alpha system (DLA) survey. The sample contains 99 DLAs towards 89 quasars from SDSS DR5 DLA in a uniform way. analyze metallicities and kinematic diagnostics, including velocity width 90% optical depth, \Delta v_{90}, equivalent widths SiII 1526, CIV 1548 MgII 2796 transitions. To avoid strong line-saturation effects on measured medium-resolution spectra (FWHM~71 km/s), we...
Abstract Fast radio burst (FRB) 190608 was detected by the Australian Square Kilometre Array Pathfinder (ASKAP) and localized to a spiral galaxy at <?CDATA ${z}_{\mathrm{host}}=0.11778$?> in Sloan Digital Sky Survey (SDSS) footprint. The has large dispersion measure ( ${\mathrm{DM}}_{\mathrm{FRB}}=339.8\,\mathrm{pc}\,{\mathrm{cm}}^{-3}$?> ) compared expected cosmic average its redshift. It also rotation ${\mathrm{RM}}_{\mathrm{FRB}}=353\,\mathrm{rad}\,{{\rm{m}}}^{-2}$?> scattering timescale...
As large optical quasar surveys for DLAs become a reality and the study of star-forming gas in early universe achieves statistical robustness, it is now vital to identify quantify sources systematic error. Because nature optically selected makes them vulnerable dust obscuration, we have undertaken radio-selected survey address this bias. We present definition results survey. then combine our sample with CORALS data set investigate H I column density distribution function f(N,X) toward...
We probe the physical conditions in high-redshift galaxies, specifically, damped Lyα systems (DLAs) using neutral carbon (C i) fine structure lines and molecular hydrogen (H2). report five new detections of C i analyze an additional two DLAs with previously published data. also present one detection H2 a DLA. method analysis that simultaneously constrains both volume density temperature gas, as opposed to previous studies priori assumed gas temperature. use only column measured states...
Supernova (SN) 2008ax in NGC 4490 was discovered within hours after shock breakout, presenting the rare opportunity to study a core-collapse SN beginning with initial envelope-cooling phase immediately following breakout. We present an extensive sequence of optical and near-infrared spectra, as well three epochs spectropolarimetry. Our taken two days are dominated by hydrogen Balmer lines at high velocity. However, maximum light, He i which closely resembled those normal Type Ib supernovae...
We report that the neutral hydrogen (HI) mass density of Universe ($\rho_{HI}$) increases with cosmic time since $z \sim 5$, peaks at 3$, and then decreases toward 0$. This is first result Qz5, our spectroscopic survey 63 quasars \gtrsim 5$ VLT/X-SHOOTER Keck/ESI aimed characterizing intervening HI gas absorbers 5$. The main feature Qz5 high resolution ($R 7000 - 9000$) spectra, which allows us to (1) accurately detect column in an increasingly intergalactic medium (2) determine reliability...
Abstract We report that the neutral hydrogen (H i ) mass density of Universe ( ρ H increases with cosmic time since z ∼ 5, peaks at 3, and then decreases toward 0. This is first result Qz5, our spectroscopic survey 63 quasars ≳ 5 VLT/X-SHOOTER Keck/ESI aimed characterizing intervening gas absorbers 5. The main feature Qz5 high resolution R 7000–9000) spectra, which allows us to (1) accurately detect column in an increasingly intergalactic medium (2) determine reliability previous...
We report evidence for a bimodality in damped Lyα systems (DLAs). Using [C II] 158 μm cooling rates, ℓc, we find distribution with peaks at ℓc = 10−27.4 and 10−26.6 ergs s−1 H−1 separated by trough ℓcritc ≈ 10−27.0 H−1. divide the sample into "low cool" DLAs ⩽ "high > K-S probabilities that velocity width, metallicity, dust-to-gas ratio, Si II equivalent width two subsamples are drawn from same parent population small. These quantities significantly larger high cool population, while H I...
Abstract We present observations from the Gemini Multi-Conjugate Adaptive Optics System/Gemini South Imager at of five fast radio burst (FRB) host galaxies FRBs with subarcsecond localizations. examine and quantify spatial distributions locations respect to their galaxy light distributions, finding a median host-normalized offset 2.09 half-light radii ( r e ) trend that these occur in fainter regions galaxies. When combined FRB sample Mannings et al., we find are statistically distinct...
We present the first direct evidence for cold gas in a high redshift DLA galaxy. measured several multiplets of weak neutral carbon (CI) transitions order to perform curve growth analysis. A delta chi-squared test constrains best fit Doppler parameter, b = 0.33_{-0.04}^{+0.05} km/s, and logN(CI) 13.30 +- 0.2 cm^-2. This parameter kinetic temperature T <= 78 K (T 115 K, 2 sigma). used associated CI fine structure lines constrain volume density gas, n(HI) ~ 40 - 200 cm^-3 (2 sigma), resulting...
We present the first Keck/OSIRIS infrared IFU observations of a high redshift damped Lyman-alpha (DLA) galaxy detected in line sight to background quasar. By utilizing Laser Guide Star Adaptive Optics (LGSAO) reduce quasar PSF FWHM~0.15 arcsec, we were able search for and map foreground DLA emission free from contamination. maps H-alpha [OIII] $\lambda \lambda$ 5007, 4959 2222-0946 at z ~ 2.35. From composite spectrum over region measure star formation rate 9.5 $\pm$ 1.0 M$_{\odot}$...
We present the first large, blind and uniformly selected survey for molecular hydrogen (H2) in damped Lyman α systems (DLAs) with moderate-to-high resolution spectra. 86 DLAs were searched absorption many Werner H2 transitions, ≈79 per cent completeness column densities above N(H2) = 1017.5 cm−2 an assumed Doppler broadening parameter b 2 km s−1. Only a single strong absorber was found – system detected previously Very Large Telescope/Ultraviolet Visual Echelle Spectrograph Given our...
We report two detections of deuterated molecular hydrogen (HD) in QSO absorption-line systems at $z > 2$. Toward J2123-0500, we find $N$(HD) $= 13.84 \pm 0.2$ for a sub-DLA with metallicity $\simeq 0.5Z_{\odot}$ and $N$(H$_2$) = $17.64 0.15$ 2.0594$. FJ0812+32, 15.38 0.3$ solar-metallicity DLA $19.88 2.6265$. These have ratios HD to H$_2$ above that observed dense clouds within the Milky Way disk apparently consistent simple conversion from cosmological ratio D/H. are not readily explained...
We examine the velocity structure in gas associated with H i damped Lyα absorption system at redshift z= 1.7764 towards QSO 1331 + 170 using Arecibo 21-cm data, optical spectra from Keck High Resolution Echelle Spectrograph (HIRES) and European Southern Observatory (ESO) Very Large Telescope (VLT) Ultraviolet Visual (UVES), a previously published Hubble Space (HST) Imaging (STIS) ultraviolet spectrum. From data we find least two, possibly three, components showing C lines. One of these has...
By comparing the widths of absorption lines from OI, SiII and FeII in redshift z=2.076 single-component damped Lyman alpha system spectrum Q2206-199 we establish that these arise Warm Neutral Medium gas at ~12000 +/- 3000K. This is consistent with thermal equilibrium model estimates ~ 8000K for galaxies, but not presence a significant cold component. It also with, required by, absence CII* fine structure this system. Some possible implications concerning abundance narrow-line WNM absorbers...
The relative abundances of the Fe-peak elements (Ti-Zn) at lowest metallicities are intimately linked to physics core-collapse supernova explosions. With a sample 25 very metal-poor damped Lyman-alpha systems, we investigate trends element ratios with metallicity. For nine DLAs, direct measurement (or useful upper limit) one or more Ti,Cr,Co,Ni,Zn/Fe abundance could be determined from detected absorption lines. remaining systems (without detections), devised new form spectral stacking...
Abstract The Fermi Bubbles are two giant gamma-ray emitting lobes extending 55° above and below the Galactic center. While Northern Bubble has been extensively studied in ultraviolet (UV) absorption, little is known about gas kinematics of southern Bubble. We use UV absorption-line spectra from Cosmic Origins Spectrograph (COS) on Hubble Space Telescope to probe using a sample 17 background AGNs projected behind or near measure incidence high-velocity clouds (HVC), finding that 4 out 6...