A5007488473- Astronomy and Astrophysical Research
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Stellar, planetary, and galactic studies
- Astronomical Observations and Instrumentation
- Astrophysical Phenomena and Observations
- Astrophysics and Cosmic Phenomena
- Astrophysics and Star Formation Studies
- Radio Astronomy Observations and Technology
- Adaptive optics and wavefront sensing
- Astro and Planetary Science
- CCD and CMOS Imaging Sensors
- Scientific Research and Discoveries
- History and Developments in Astronomy
- Pulsars and Gravitational Waves Research
- Calibration and Measurement Techniques
- Cosmology and Gravitation Theories
- Solar and Space Plasma Dynamics
- SAS software applications and methods
- Geophysics and Gravity Measurements
- Particle Detector Development and Performance
- Space Technology and Applications
- Dark Matter and Cosmic Phenomena
- Plant Molecular Biology Research
- Medical Imaging Techniques and Applications
Goddard Space Flight Center
2017-2024
Deleted Institution
2017-2024
Arizona State University
2014-2023
Max Planck Institute for Astronomy
2019
Max Planck Society
2019
California Institute of Technology
2018
Australian Astronomical Observatory
2018
Instituto de Astrofísica de Andalucía
2018
Institute For Defense Analyses
2014
The University of Sydney
2009
The Swift mission, scheduled for launch in 2004, is a multiwavelength observatory gamma-ray burst (GRB) astronomy. It first-of-its-kind autonomous rapid-slewing satellite transient astronomy and pioneers the way future rapid-reaction missions. will be far more powerful than any previous GRB observing 100 bursts yr-1 performing detailed X-ray UV/optical afterglow observations spanning timescales from 1 minute to several days after burst. objectives are (1) determine origin of GRBs, (2)...
The energy requirements of gamma-ray bursts have in past been poorly constrained because three major uncertainties: the distances to bursts, degree burst beaming, and efficiency production. first these has resolved, with both indirect evidence (the distribution flux position) direct (redshifted absorption features afterglow spectrum GRB 970508) pointing cosmological distances. We now wish address second uncertainty. Afterglows allow a statistical test described an earlier paper. In this...
We report on a complete sample of seven luminous early-type galaxies in the Hubble Ultra Deep Field (UDF) with spectroscopic redshifts between 1.39 and 2.47, to KAB < 23. Using BzK selection criterion, we have preselected set objects over UDF, which fulfill photometric conditions for being passively evolving at z > 1.4. Low-resolution spectra these been extracted from Space Telescope (HST) ACS grism data taken UDF by Grism Program Extragalactic Science (GRAPES) project. Redshifts identified...
Gamma-ray bursts (GRBs) serve as powerful probes of the early Universe, with their luminous afterglows revealing locations and physical properties star forming galaxies at highest redshifts, potentially locating first generation (Population III) stars. Since GRB have intrinsically very simple spectra, they allow robust redshifts from low signal to noise spectroscopy, or photometry. Here we present a photometric redshift z~9.4 for Swift-detected 090429B based on deep observations...
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...
The Early Release Observations (EROs) of JWST beautifully demonstrate the promise in characterizing universe at cosmic dawn. We analyze ERO spectra three $z \sim 8$ galaxies to determine their metallicities, gas temperatures and ionization. These offer first opportunity understand physical properties epoch-of-reionization through detailed rest-optical emission line spectroscopy. show that these objects have metal abundances $12+\log[O/H] \approx 6.9 - 8.2$, based on both $T_e$ method a...
If gamma-ray bursts are highly collimated, radiating into only a small fraction of the sky, energy requirements each event may be reduced by several (~4-6) orders magnitude, and rate is increased correspondingly. Extreme conditions in bursters lead to relativistic motions (bulk Lorentz factors Γ ≳ 100). This results strong forward beaming emitted radiation observer's rest frame. Thus, all information on comes from those ejecta narrow cone (opening angle ~1/Γ) pointing toward observer. We at...
Lyman-alpha emission from galaxies should be suppressed completely or partially at redshifts beyond reionization. Without knowing the instrinsic properties of z = 6.5, this attenuation is hard to infer in any one source, but can infered a comparison luminosity functions lyman-alpha emitters just before and after We combine published surveys widely varying depths areas construct z=6.5 5.7, where characteristic L_star density phi_star are well constrained while faint-end slope function...
The Large Area Lyman Alpha survey has found ≈150 Lyα emitters at z = 4.5. While stellar models predict a maximum equivalent width (EW) of 240 Å, 60% the have EWs exceeding this value. We attempt to model observed EW distribution by combining population with an extrapolation break galaxy luminosity function 4, incorporating observational selection effects and Malmquist bias. To reproduce high seen in sample, we need postulate initial mass extreme slope α 0.5 (instead 2.35), zero-metallicity...
Continued photometric monitoring of the gravitational lens system 0957+561A, B in g and r bands with Apache Point Observatory (APO) 3.5 m telescope during 1996 shows a sharp g-band event trailing (B) image light curve at precise time predicted an earlier paper. The prediction was based on observation 1995 leading (A) differential delay 415 days. This success confirms so-called short delay, absence any such feature near 540 days rejects "long delay" for this system, thus resolving...
We report on a new survey for z=4.5 Lyman alpha sources, the Large Area Alpha (LALA) survey. Our achieves an unprecedented combination of volume and sensitivity by using narrow-band filters 8192x8192 pixel CCD Mosaic Camera at 4 meter Mayall telescope Kitt Peak National Observatory. Well-detected sources with flux equivalent width matching known high redshift galaxies (i.e., observed above 80 Angstroms line+continuum between 2.6e-17 5.2e-17 erg/cm^2/sec in Angstrom filter) have surface...
Narrowband searches for Lyα emission are an efficient way of identifying star-forming galaxies at high redshifts. We present Keck Telescope spectra confirming redshifts z ≈ 5.7 three objects discovered in the Large-Area Lyman Alpha (LALA) survey Kitt Peak National Observatory. All show strong, narrow lines with asymmetric profile that is characteristically produced high-redshift emitters by preferential H I absorption blue wing line. These undetected deep BW, V, R, and λ 6600 Å narrowband...
view Abstract Citations (311) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Radio Transients from Gamma-Ray Bursters Paczynski, Bohdan ; Rhoads, James E. The rapid time variability of gamma-ray bursts implies the sources are very compact, and peak luminosities so high that some matter must be ejected at ultra-relativistic speeds. large Lorentz factors bulk flow also indicated by broad hard spectra. It is natural to expect when relativistic...
Despite both being outbursts of luminous blue variables (LBVs), SN 2009ip and UGC 2773 OT2009-1 have very different progenitors, spectra, circumstellar environments, possibly physical mechanisms that generated the outbursts. From pre-eruption HST images, we determine initial masses >60 >25 M_sun, respectively. Optical spectroscopy shows at peak had a 10,000 K photosphere its spectrum was dominated by narrow H Balmer emission, similar to classical LBV giant outbursts, also known as "supernova...
Abstract We present the first results from ongoing Lyman Alpha Galaxies in Epoch of Reionization (LAGER) project, which is largest narrowband survey for z ∼ 7 galaxies to date. Using a specially built filter NB964 superb large-area Dark Energy Camera (DECam) on NOAO/CTIO 4 m Blanco telescope, LAGER has collected 34 hr imaging data 3 deg 2 COSMOS field. have identified 23 Ly α Emitter candidates at = 6.9 central 2-deg region, where DECam and public multi-band images exist. The resulting...
While most of the inter-galactic medium (IGM) today is permeated by ionized hydrogen, it was largely filled with neutral hydrogen for first 700 million years after Big Bang. The process that IGM (cosmic reionization) expected to be spatially inhomogeneous, fainter galaxies playing a significant role. However, we still have only few direct constraints on reionization process. Here report spectroscopic confirmation two and very likely third galaxy in group (hereafter EGS77) at redshift z =...
Abstract We present a new measurement of the Ly α luminosity function (LF) at redshift z = 6.9, finding moderate evolution from 5.7 that is consistent with fully or largely ionized ∼ 7 intergalactic medium. Our result based on four fields LAGER (Lyman Alpha Galaxies in Epoch Reionization) project. survey volume 6.1 × 10 6 Mpc 3 double next largest survey. combine two (WIDE12 and GAMA15A) previously reported (COSMOS CDFS). In fields, we identify N 95 6.9 emitter (LAEs) candidates,...
We present photometry and spectroscopy of the afterglow GRB 030323. VLT spectra show damped Lyα (DLA) absorption low- high-ionization lines at a redshift . The inferred neutral hydrogen column density, , is larger than any (GRB- or QSO-) DLA density directly from in absorption. From photometry, we derive conservative upper limit to host-galaxy extinction: mag. iron abundance while metallicity gas as measured sulphur an on H2 molecular fraction In trough, emission line detected, which...
We report on the results of a search for Ly-alpha emission from host galaxy z=2.140 GRB 011211 and other galaxies in its surrounding field. detect as well six The restframe equivalent width line is about 21 AA. This fifth detection out five possible detections galaxies, strongly indicating that hosts, at least high redshifts, are emitters. intriguing only 25% Lyman-Break selected similar redshifts have lines with larger than 20 Possible explanations i) preference progenitors to be metal-poor...
We show that if all γ-ray bursts emit X-rays in a way similar to those observed by BeppoSAX, much of the extinction along line sight host galaxy burst can be destroyed. Two mechanisms are principally responsible for dust destruction: grain heating and charging. The latter, which lead electrostatic stresses greater than tensile strength grains, is often more important. Grains may regularly destroyed at distances as large ~100 pc. This destruction permit us see UV/optical afterglow even when...
High redshift galaxies selected on the basis of their strong Lyman-alpha emission tend to be young ages and small physical sizes. We show this by analyzing spectral energy distribution (SED) 9 emitting (LAE) at 4.0 < z 5.7 n Hubble Ultra Deep Field (HUDF). Rest-frame UV optical 700A lambda 7500A luminosities, or upper limits, are used constrain old stellar populations. derive best fit, as well maximally massive old, properties all objects. that these faint distant objects very young, being...
Lyα galaxies at high redshifts offer a powerful probe of both the formation and reionization intergalactic medium. line emission is an efficient tool for identifying young redshift because it strong in systems with stars little or no dust—properties expected undergoing their first burst star formation. also provide robust test epoch that independent Gunn-Peterson trough observations quasar spectra better able to distinguish line-center optical depths τ ~ 5 from 105. This neutral gas scatters...