James Rhoads - ASU

James Rhoads
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James Rhoads
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ASU
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Cosmology and Nongalactic Astrophysics (35)
 
Astrophysics of Galaxies (17)
 
Astrophysics (6)
 
Solar and Stellar Astrophysics (3)
 
Instrumentation and Methods for Astrophysics (3)
 
High Energy Astrophysical Phenomena (1)
 
Earth and Planetary Astrophysics (1)

Publications Authored By James Rhoads

We present the first results from the ongoing LAGER project (Lyman Alpha Galaxies in the Epoch of Reionization), which is the largest narrowband survey for $z\sim$ 7 galaxies to date. Using a specially built narrowband filter NB964 for the superb large-area Dark-Energy Camera (DECam) on the NOAO/CTIO 4m Blanco telescope, LAGER has collected 34 hours NB964 narrowband imaging data in the 3 deg$^2$ COSMOS field. We have identified 27 Lyman Alpha Emitter (LAE) candidates at $z=$ 6. Read More

We studied Lyman-$\alpha$ (Ly$\alpha$) escape in a statistical sample of 43 Green Peas with HST/COS Ly$\alpha$ spectra. Green Peas are nearby star-forming galaxies with strong [OIII]$\lambda$5007 emission lines. Our sample is four times larger than the previous sample and covers a much more complete range of Green Pea properties. Read More

Green Peas are nearby analogs of high-redshift Ly$\alpha$-emitting galaxies. To probe their Ly$\alpha$ escape, we study the spatial profiles of Ly$\alpha$ and UV continuum emission of 24 Green Pea galaxies using the Cosmic Origins Spectrograph (COS) on Hubble Space Telescope (HST). We extract the spatial profiles of Ly$\alpha$ emission from their 2D COS spectra, and of UV continuum from both the 2D spectra and NUV images. Read More

We present a narrowband survey with three adjacent filters for z=2.8--2.9 Lyman Alpha Emitter (LAE) galaxies in the Extended Chandra Deep Field South (ECDFS), along with spectroscopic followup. Read More

Deep rest-frame optical spectroscopy is critical for characterizing and understanding the physical conditions and properties of the ionized gas in galaxies. Here, we present a new spectroscopic survey called "Metal Abundances across Cosmic Time" or $\mathcal{MACT}$, which will obtain rest-frame optical spectra for $\sim$3000 emission-line galaxies. This paper describes the optical spectroscopy that has been conducted with MMT/Hectospec and Keck/DEIMOS for $\approx$1900 $z=0. Read More

2015Sep
Affiliations: 1UT Austin, 2UT Austin, 3ASU, 4ASU, 5ASU, 6STScI, 7STScI, 8NOAO, 9Steward Obsv., 10UC Riverside, 11Gemini Obsv., 12Texas A&M Univ., 13USTC

We present the results from a stellar population modeling analysis of a sample of 162 z=4.5, and 14 z=5.7 Lyman alpha emitting galaxies (LAEs) in the Bootes field, using deep Spitzer/IRAC data at 3. Read More

We analyze archival Ly$\alpha$ spectra of 12 "Green Pea" galaxies observed with the Hubble Space Telescope, model their Ly$\alpha$ profiles with radiative transfer models, and explore the dependence of Ly$\alpha$ escape fraction on various properties. Green Pea galaxies are nearby compact starburst galaxies with [OIII]$\lambda$5007 equivalent widths of hundreds of \AA. All 12 Green Pea galaxies in our sample show Ly$\alpha$ lines in emission, with a Ly$\alpha$ equivalent width distribution similar to high redshift Ly$\alpha$ emitters. Read More

We report on two regularly rotating galaxies at redshift z=2, using high resolution spectra of the bright [CII] 158 micron emission line from the HIFI instrument on the Herschel Space Observatory. Both SDSS090122.37+181432. Read More

We present a sample of 33 spectroscopically confirmed z ~ 3.1 Ly$\alpha$-emitting galaxies (LAEs) in the Cosmological Evolution Survey (COSMOS) field. This paper details the narrow-band survey we conducted to detect the LAE sample, the optical spectroscopy we performed to confirm the nature of these LAEs, and a new near-infrared spectroscopic detection of the [O III] 5007 \AA\ line in one of these LAEs. Read More

Using Ly{\alpha} emission line as a tracer of high redshift star forming galaxies, hundreds of Ly{\alpha} emission line galaxies (LAEs) at z > 5 have been detected. These LAEs are considered to be low mass young galaxies, critical to the reionization of the universe and the metal enrichment of circumgalactic medium (CGM) and intergalactic medium (IGM). It is assumed that outflows in LAEs can help ionizing photons and Ly{\alpha} photons escape out of galaxies. Read More

Ly{\alpha} line EWs provide important clues to the physical nature of high redshift LAEs. However, measuring the Ly{\alpha} EW distribution of high-z narrowband selected LAEs can be hard because many sources do not have broadband photometry. We investigate the possible biases in measuring the intrinsic Ly{\alpha} EW distribution for a LAE sample at z $\sim$ 4. Read More

Motivated by recent observations of galaxies dominated by emission lines, which show evidence of being metal poor with young stellar populations, we present calculations of multiple model grids with a range of abundances, ionization parameters, and stellar ages, finding that the predicted spectral line diagnostics are heavily dependent on all three parameters. These new model grids extend the ionization parameter to larger values than typically explored. We compare these model predictions with previous observations of such objects, including two new Lyman-$\alpha$ emitting galaxies (LAE) that we have observed. Read More

In the absence of spectra, fitting template model spectra to observed photometric fluxes, known as Spectral Energy Distribution (SED) fitting, has become the workhorse for identifying high-z galaxies. In this paper, we present an analysis of the most recent and possibly most distant galaxies discovered in the Hubble Ultra Deep Field using a more robust method of redshift estimation based on Markov Chain Monte Carlo fitting (MCMC), rather than relying on the redshift of "best fit" models obtained using common chi^2 minimization techniques. The advantage of MCMC fitting is the ability to accurately estimate the probability density function of the redshift, as well as any other input model parameters, allowing us to derive accurate credible intervals by properly marginalizing over all other input model parameters. Read More

We present observations of a luminous galaxy at redshift z=6.573 --- the end of the reioinization epoch --- which has been spectroscopically confirmed twice. The first spectroscopic confirmation comes from slitless HST ACS grism spectra from the PEARS survey (Probing Evolution And Reionization Spectroscopically), which show a dramatic continuum break in the spectrum at restframe 1216 A wavelength. Read More

We present the first dynamical mass measurements for Lyman alpha galaxies at high redshift, based on velocity dispersion measurements from rest-frame optical emission lines and size measurements from HST imaging, for a sample of nine galaxies drawn from four surveys. These measurements enable us to study the nature of Lyman alpha galaxies in the context of galaxy scaling relations. The resulting dynamical masses range from 1e9 to 1e10 solar masses. Read More

We present spectroscopic measurements of the [OIII] emission line from two subregions of strong Lyman-alpha emission in a radio-quiet Lyman-alpha blob (LAB). The blob under study is LAB1 (Steidel et al. 2000) at z ~ 3. Read More

We discuss scientific, technical and programmatic issues related to the use of an NRO 2.4m telescope for the WFIRST initiative of the 2010 Decadal Survey. We show that this implementation of WFIRST, which we call "NEW WFIRST," would achieve the goals of the NWNH Decadal Survey for the WFIRST core programs of Dark Energy and Microlensing Planet Finding, with the crucial benefit of deeper and/or wider near-IR surveys for GO science and a potentially Hubble-like Guest Observer program. Read More

We present a full analysis of the Probing Evolution And Reionization Spectroscopically (PEARS) slitess grism spectroscopic data obtained with the Advanced Camera for Surveys on HST. PEARS covers fields within both the Great Observatories Origins Deep Survey (GOODS) North and South fields, making it ideal as a random survey of galaxies, as well as the availability of a wide variety of ancillary observations to support the spectroscopic results. Using the PEARS data we are able to identify star forming galaxies within the redshift volume 0< z<1. Read More

2012Jul

The size, mass, luminosity, and space density of Lyman-alpha emitting (LAE) galaxies observed at intermediate to high redshift agree with expectations for the properties of galaxies that formed metal-poor halo globular clusters (GCs). The low metallicity of these clusters is the result of their formation in low-mass galaxies. Metal-poor GCs could enter spiral galaxies along with their dwarf galaxy hosts, unlike metal-rich GCs which form in the spirals themselves. Read More

Lyman-alpha emitting galaxies can be used to study cosmological reionization, because a neutral intergalactic medium scatters Lyman-alpha photons into diffuse halos whose surface brightness falls below typical survey detection limits. Here we present the Lyman-alpha emitting galaxy LAE J095950.99+021219. Read More

Galaxies selected on the basis of their emission line strength show low metallicities, regardless of their redshifts. We conclude this from a sample of faint galaxies at redshifts between 0.6 < z < 2. Read More

We present a spectroscopically confirmed sample of Lyman alpha emitting galaxies (LAEs) at z ~ 4.5 in the Extended Chandra Deep Field South (ECDFS), which we combine with a sample of z ~ 4.5 LAEs from the Large Area Lyman Alpha (LALA) survey to build a unified Lya luminosity function (LF). Read More

We report a search for z~6.96 Ly-alpha emitters (LAEs) using a Narrow-Band filter, centered at 9680 Angstroms, with the IMACS instrument on the Magellan telescope at Las Campanas Observatory. We obtain a sample of 6 Ly-alpha emitter candidates of luminosity ~10^42 erg/s in a total area of 465 square arcmin corresponding to a comoving volume of ~ 72000 Mpc^3. Read More

2011Jul
Affiliations: 1School of Earth & Space Exploration, Arizona State University, 2School of Earth & Space Exploration, Arizona State University, 3School of Earth & Space Exploration, Arizona State University, 4School of Earth & Space Exploration, Arizona State University

Rapid mass assembly, likely from mergers or smooth accretion, has been predicted to play a vital role in star-formation in high-redshift Lyman-alpha (Lya) emitters. Here we predict the major merger, minor merger, and smooth accreting Lya emitter fraction from z~3 to z~7 using a large dark matter simulation, and a simple physical model that is successful in reproducing many observations over this large redshift range. The central tenet of this model, different from many of the earlier models, is that the star-formation in Lya emitters is proportional to the mass accretion rate rather than the total halo mass. Read More

The study of Ly-alpha emission in the high-redshift universe is a useful probe of the epoch of reionization, as the Ly-alpha line should be attenuated by the intergalactic medium (IGM) at low to moderate neutral hydrogen fractions. Here we present the results of a deep and wide imaging search for Ly-alpha emitters in the COSMOS field. We have used two ultra-narrowband filters (filter width of ~8-9 {\deg}A) on the NEWFIRM camera, installed on the Mayall 4m telescope at Kitt Peak National Observatory, in order to isolate Ly-alpha emitters at z = 7. Read More

We have coadded X-ray flux of all known Lyman Alpha Emitters (LAEs) in the 4 Msec Chandra Deep Field South (CDF-S) region, to place sensitive upper limits on the average unobscured star-formation rate (SFR_X) in these galaxies. A very small fraction of Lyman-Alpha galaxies in the field are individually detected in the X-rays, implying a low fraction of AGN activity. After excluding the few X-ray detected LAEs, we stack the undetected LAEs located in the 4 Ms CDF-S data and 250 ks Extended CDF-S (ECDFS) data, and compute a 1-\sigma upper limit on SFR_X < 14, 28, 28, 140, 440, 880 M$_{\sun}$ yr$^{-1}$ for LAEs located at z = 2. Read More

We show that populations of high redshift galaxies grow more luminous as they grow in linear size. This is because the brightness per unit area has a distinct upper limit due to the self-regulating nature of star-formation. As a corollary, we show that the observed increase in characteristic luminosity of Lyman Break Galaxies (L*) with time can be explained by their increase in size, which scales as 1/H(z). Read More

We have a developed a new method for fitting spectral energy distributions (SEDs) to identify and constrain the physical properties of high-redshift (4 < z < 8) galaxies. Our approach uses an implementation of Bayesian based Markov Chain Monte Carlo (PiMC^2) that allows us to compare observations to arbitrarily complex models and to compute 95% credible intervals that provide robust constraints for the model parameters. The work is presented in 2 sections. Read More

We present the results of an optical spectroscopic study of 12 GALEX-discovered star-forming Lyman alpha emitting galaxies (LAEs) at z ~ 0.3. We measure the emission line fluxes from these galaxies by fitting their observed spectra to stellar population models in order to correct for underlying stellar absorption. Read More

2010Nov
Affiliations: 1Arizona State University, AZ, 2Arizona State University, AZ, 3Arizona State University, AZ, 4Space Telescope Science Institute, Baltimore, MD, 5Arizona State University, AZ, 6Johns Hopkins University, Baltimore, MD, 7NASA Goddard Space Flight Center, Greenbelt, MD, 8Space Telescope Science Institute, Baltimore, MD, 9AAO/OCIW Magellan fellow, University of Melbourne, VIC, Australia

We present spectroscopy of 76 emission-line galaxies (ELGs) in CDF-S taken with the LDSS3 spectrograph on Magellan Telescope. These galaxies are selected to have emission lines with ACS grism data in the Hubble Space Telescope Probing Evolution and Reionization Spectroscopically (PEARS) grism Survey. The ACS grism spectra cover the wavelength range 6000-9700 \AA\ and most PEARS grism redshifts are based on a single emission line + photometric redshifts from broad-band colors; the Magellan spectra cover a wavelength range from 4000 {\AA} to 9000 {\AA}, and provide a check on redshifts derived from PEARS data. Read More

We present the highest redshift detections of resolved Lyman alpha emission, using Hubble Space Telescope/ACS F658N narrowband-imaging data taken in parallel with the Wide Field Camera 3 Early Release Science program in the GOODS CDF-S. We detect Lyman alpha emission from three spectroscopically confirmed z = 4.4 Lyman alpha emitting galaxies (LAEs), more than doubling the sample of LAEs with resolved Lyman alpha emission. Read More

Lyman alpha (Lya) emission lines should be attenuated in a neutral intergalactic medium (IGM). Therefore the visibility of Lya emitters at high redshifts can serve as a valuable probe of reionization at about the 50% level. We present an imaging search for z=7. Read More

We present the first spectroscopic measurements of the [OIII] 5007 A line in two z ~ 3.1 Lyman-alpha emitting galaxies (LAEs) using the new near-infrared instrument LUCIFER1 on the 8.4m Large Binocular Telescope (LBT). Read More

Despite both being outbursts of luminous blue variables (LBVs), SN 2009ip and UGC 2773 OT2009-1 have very different progenitors, spectra, circumstellar environments, and possibly physical mechanisms that generated the outbursts. From pre-eruption HST images, we determine that SN 2009ip and UGC 2773 OT2009-1 have initial masses of >60 and >25 M_sun, respectively. Optical spectroscopy shows that at peak SN 2009ip had a 10,000 K photosphere and its spectrum was dominated by narrow H Balmer emission, similar to classical LBV giant outbursts, also known as "supernova impostors. Read More

2009Dec
Authors: LSST Science Collaboration, Paul A. Abell1, Julius Allison2, Scott F. Anderson3, John R. Andrew4, J. Roger P. Angel5, Lee Armus6, David Arnett7, S. J. Asztalos8, Tim S. Axelrod9, Stephen Bailey10, D. R. Ballantyne11, Justin R. Bankert12, Wayne A. Barkhouse13, Jeffrey D. Barr14, L. Felipe Barrientos15, Aaron J. Barth16, James G. Bartlett17, Andrew C. Becker18, Jacek Becla19, Timothy C. Beers20, Joseph P. Bernstein21, Rahul Biswas22, Michael R. Blanton23, Joshua S. Bloom24, John J. Bochanski25, Pat Boeshaar26, Kirk D. Borne27, Marusa Bradac28, W. N. Brandt29, Carrie R. Bridge30, Michael E. Brown31, Robert J. Brunner32, James S. Bullock33, Adam J. Burgasser34, James H. Burge35, David L. Burke36, Phillip A. Cargile37, Srinivasan Chandrasekharan38, George Chartas39, Steven R. Chesley40, You-Hua Chu41, David Cinabro42, Mark W. Claire43, Charles F. Claver44, Douglas Clowe45, A. J. Connolly46, Kem H. Cook47, Jeff Cooke48, Asantha Cooray49, Kevin R. Covey50, Christopher S. Culliton51, Roelof de Jong52, Willem H. de Vries53, Victor P. Debattista54, Francisco Delgado55, Ian P. Dell'Antonio56, Saurav Dhital57, Rosanne Di Stefano58, Mark Dickinson59, Benjamin Dilday60, S. G. Djorgovski61, Gregory Dobler62, Ciro Donalek63, Gregory Dubois-Felsmann64, Josef Durech65, Ardis Eliasdottir66, Michael Eracleous67, Laurent Eyer68, Emilio E. Falco69, Xiaohui Fan70, Christopher D. Fassnacht71, Harry C. Ferguson72, Yanga R. Fernandez73, Brian D. Fields74, Douglas Finkbeiner75, Eduardo E. Figueroa76, Derek B. Fox77, Harold Francke78, James S. Frank79, Josh Frieman80, Sebastien Fromenteau81, Muhammad Furqan82, Gaspar Galaz83, A. Gal-Yam84, Peter Garnavich85, Eric Gawiser86, John Geary87, Perry Gee88, Robert R. Gibson89, Kirk Gilmore90, Emily A. Grace91, Richard F. Green92, William J. Gressler93, Carl J. Grillmair94, Salman Habib95, J. S. Haggerty96, Mario Hamuy97, Alan W. Harris98, Suzanne L. Hawley99, Alan F. Heavens100, Leslie Hebb101, Todd J. Henry102, Edward Hileman103, Eric J. Hilton104, Keri Hoadley105, J. B. Holberg106, Matt J. Holman107, Steve B. Howell108, Leopoldo Infante109, Zeljko Ivezic110, Suzanne H. Jacoby111, Bhuvnesh Jain112, R113, Jedicke114, M. James Jee115, J. Garrett Jernigan116, Saurabh W. Jha117, Kathryn V. Johnston118, R. Lynne Jones119, Mario Juric120, Mikko Kaasalainen121, Styliani122, Kafka, Steven M. Kahn, Nathan A. Kaib, Jason Kalirai, Jeff Kantor, Mansi M. Kasliwal, Charles R. Keeton, Richard Kessler, Zoran Knezevic, Adam Kowalski, Victor L. Krabbendam, K. Simon Krughoff, Shrinivas Kulkarni, Stephen Kuhlman, Mark Lacy, Sebastien Lepine, Ming Liang, Amy Lien, Paulina Lira, Knox S. Long, Suzanne Lorenz, Jennifer M. Lotz, R. H. Lupton, Julie Lutz, Lucas M. Macri, Ashish A. Mahabal, Rachel Mandelbaum, Phil Marshall, Morgan May, Peregrine M. McGehee, Brian T. Meadows, Alan Meert, Andrea Milani, Christopher J. Miller, Michelle Miller, David Mills, Dante Minniti, David Monet, Anjum S. Mukadam, Ehud Nakar, Douglas R. Neill, Jeffrey A. Newman, Sergei Nikolaev, Martin Nordby, Paul O'Connor, Masamune Oguri, John Oliver, Scot S. Olivier, Julia K. Olsen, Knut Olsen, Edward W. Olszewski, Hakeem Oluseyi, Nelson D. Padilla, Alex Parker, Joshua Pepper, John R. Peterson, Catherine Petry, Philip A. Pinto, James L. Pizagno, Bogdan Popescu, Andrej Prsa, Veljko Radcka, M. Jordan Raddick, Andrew Rasmussen, Arne Rau, Jeonghee Rho, James E. Rhoads, Gordon T. Richards, Stephen T. Ridgway, Brant E. Robertson, Rok Roskar, Abhijit Saha, Ata Sarajedini, Evan Scannapieco, Terry Schalk, Rafe Schindler, Samuel Schmidt, Sarah Schmidt, Donald P. Schneider, German Schumacher, Ryan Scranton, Jacques Sebag, Lynn G. Seppala, Ohad Shemmer, Joshua D. Simon, M. Sivertz, Howard A. Smith, J. Allyn Smith, Nathan Smith, Anna H. Spitz, Adam Stanford, Keivan G. Stassun, Jay Strader, Michael A. Strauss, Christopher W. Stubbs, Donald W. Sweeney, Alex Szalay, Paula Szkody, Masahiro Takada, Paul Thorman, David E. Trilling, Virginia Trimble, Anthony Tyson, Richard Van Berg, Daniel Vanden Berk, Jake VanderPlas, Licia Verde, Bojan Vrsnak, Lucianne M. Walkowicz, Benjamin D. Wandelt, Sheng Wang, Yun Wang, Michael Warner, Risa H. Wechsler, Andrew A. West, Oliver Wiecha, Benjamin F. Williams, Beth Willman, David Wittman, Sidney C. Wolff, W. Michael Wood-Vasey, Przemek Wozniak, Patrick Young, Andrew Zentner, Hu Zhan
Affiliations: 1Stella, 2Stella, 3Stella, 4Stella, 5Stella, 6Stella, 7Stella, 8Stella, 9Stella, 10Stella, 11Stella, 12Stella, 13Stella, 14Stella, 15Stella, 16Stella, 17Stella, 18Stella, 19Stella, 20Stella, 21Stella, 22Stella, 23Stella, 24Stella, 25Stella, 26Stella, 27Stella, 28Stella, 29Stella, 30Stella, 31Stella, 32Stella, 33Stella, 34Stella, 35Stella, 36Stella, 37Stella, 38Stella, 39Stella, 40Stella, 41Stella, 42Stella, 43Stella, 44Stella, 45Stella, 46Stella, 47Stella, 48Stella, 49Stella, 50Stella, 51Stella, 52Stella, 53Stella, 54Stella, 55Stella, 56Stella, 57Stella, 58Stella, 59Stella, 60Stella, 61Stella, 62Stella, 63Stella, 64Stella, 65Stella, 66Stella, 67Stella, 68Stella, 69Stella, 70Stella, 71Stella, 72Stella, 73Stella, 74Stella, 75Stella, 76Stella, 77Stella, 78Stella, 79Stella, 80Stella, 81Stella, 82Stella, 83Stella, 84Stella, 85Stella, 86Stella, 87Stella, 88Stella, 89Stella, 90Stella, 91Stella, 92Stella, 93Stella, 94Stella, 95Stella, 96Stella, 97Stella, 98Stella, 99Stella, 100Stella, 101Stella, 102Stella, 103Stella, 104Stella, 105Stella, 106Stella, 107Stella, 108Stella, 109Stella, 110Stella, 111Stella, 112Stella, 113Stella, 114Stella, 115Stella, 116Stella, 117Stella, 118Stella, 119Stella, 120Stella, 121Stella, 122Stella

A survey that can cover the sky in optical bands over wide fields to faint magnitudes with a fast cadence will enable many of the exciting science opportunities of the next decade. The Large Synoptic Survey Telescope (LSST) will have an effective aperture of 6.7 meters and an imaging camera with field of view of 9. Read More

The time delay between the formation of a population of stars and the onset of type Ia supernovae (SNe Ia) sets important limits on the masses and nature of SN Ia progenitors. Here we use a new observational technique to measure this time delay by comparing the spatial distributions of SNe Ia to their local environments. Previous work attempted such analyses encompassing the entire host of each SN Ia, yielding inconclusive results. Read More

Using HST/ACS slitless grism spectra from the PEARS program, we study the stellar populations of morphologically selected early-type galaxies in the GOODS North and South fields. The sample - extracted from a visual classification of the (v2.0) HST/ACS images and restricted to redshifts z>0. Read More

We present a large sample of Ly-alpha emitting galaxies spectroscopically confirmed at z~4.5, based on IMACS spectroscopic observations of candidate LAEs in the LALA Cetus field. We identify 110 z~4. Read More

2009Jun
Affiliations: 1ASU, 2ASU, 3ASU, 4ASU, 5Saint Mary's University, 6Universitaet Zurich, 7Stockholm University

We present a simple physical model for populating dark matter halos with Lyman Alpha Emiiters(LAEs) and predict the physical properties of LAEs at z~3-7. The central tenet of this model is that the Ly-alpha luminosity is proportional to the star formation rate (SFR) which is directly related to the halo mass accretion rate. The only free parameter in our model is then the star-formation efficiency (SFE). Read More

We investigate the fraction of z ~ 0.3 Lyman alpha emitting galaxies (LAEs) which host active galactic nucleus activity, which is typically from 1 - 5% at 2 < z < 6. Using optical spectroscopy of 23 LAEs at 0. Read More

2009Jun
Affiliations: 1Arizona State University, AZ, 2Arizona State University, AZ, 3Arizona State University, AZ, 4Arizona State University, AZ, 5Arizona State University, AZ, 6University of California, Riverside, CA, 7Arizona State University, AZ, 8Space Telescope Science Institute, Baltimore, MD, 9Space Telescope Science Institute, Baltimore, MD

We apply Bayesian statistics with prior probabilities of galaxy surface luminosity (SL) to improve photometric redshifts. We apply the method to a sample of 1266 galaxies with spectroscopic redshifts in the GOODS North and South fields at 0.1 < z < 2. Read More

2009Apr
Affiliations: 1Arizona State University, 2Arizona State University, 3University of Colorado - Boulder, 4University of Massachusetts, 5Arizona State University, 6STScI, 7University of Wisconsin - Madison, 8Jet Propulsion Laboratory, Caltech, 9Jet Propulsion Laboratory, Caltech, 10Arizona State University, 11University of Exeter, 12Jet Propulsion Laboratory, Caltech, 13University of Virginia, 14University of Michigan, 15IPAC / Caltech, 16Arizona State University, 17NASA - GSFC, 18SSL - UC Berkeley, 19Jet Propulsion Laboratory, Caltech, 20University of California - Berkeley, 21Jet Propulsion Laboratory, Caltech, 22STScI, 23Arizona State University, 24LMCO

The Star Formation Camera (SFC) is a wide-field (~15'x19, >280 arcmin^2), high-resolution (18x18 mas pixels) UV/optical dichroic camera designed for the Theia 4-m space-borne space telescope concept. SFC will deliver diffraction-limited images at lambda > 300 nm in both a blue (190-517nm) and a red (517-1075nm) channel simultaneously. Our aim is to conduct a comprehensive and systematic study of the astrophysical processes and environments relevant for the births and life cycles of stars and their planetary systems, and to investigate and understand the range of environments, feedback mechanisms, and other factors that most affect the outcome of the star and planet formation process. Read More

2009Apr
Affiliations: 1Arizona State University, 2Arizona State University, 3Arizona State University, 4Arizona State University, 5NASA/Jet Propulsion Laboratory, 6University of Virginia, 7Arizona State University, 8University of Colorado - Boulder

[abridged] We propose a tiered, UV--near-IR, cosmological broad- and medium-band imaging and grism survey that covers ~10 deg^2 in two epochs to m_AB=28, ~3 deg^2 in seven epochs to m_AB=28, and ~1 deg^2 in 20 epochs to m_AB=30 mag. Such a survey is an essential complement to JWST surveys (<~0.1 deg^2 to m_AB<~31 mag at lambda>1100nm and z>~8). Read More

We present the results of a stellar population analysis of 30 Lyman alpha emitting galaxies (LAEs) at z ~ 0.3, previously discovered with the Galaxy Evolution Explorer (GALEX). With a few exceptions, we can accurately fit model spectral energy distributions to these objects, representing the first time this has been done for a large sample of LAEs at z < 3, a gap of ~ 8 Gyr in the history of the Universe. Read More

2008Nov

Recent results have shown that a substantial fraction of high-redshift Lyman alpha galaxies contain considerable amounts of dust. This implies that Lyman alpha galaxies are not primordial, as has been thought in the past. However, this dust has not been directly detected in emission; rather it has been inferred based on extinction estimates from rest-frame ultraviolet (UV) and optical observations. Read More

We carry out a comprehensive theoretical examination of the relationship between the spatial distribution of optical transients and the properties of their progenitor stars. By constructing analytic models of star-forming galaxies and the evolution of stellar populations within them, we are able to place constraints on candidate progenitors for core-collapse supernovae (SNe), long-duration gamma ray bursts, and supernovae Ia. In particular we first construct models of spiral galaxies that reproduce observations of core-collapse SNe, and we use these models to constrain the minimum mass for SNe Ic progenitors to approximately 25 solar masses. Read More

The luminosities of short gamma ray burst host galaxies are anticorrelated with both the isotropic equivalent gamma ray energy and the gamma ray luminosity of the explosions. Observational selection effects only strengthen the significance of this correlation. The correlation may indicate that there are two physically distinct groups of SGRBs. Read More

2008Jun
Affiliations: 1Arizona State University Dept. of Physics; Texas A&M University Department of Physics, 2ASU School of Earth and Space Exploration, 3ASU School of Earth and Space Exploration, 4Space Telescope Science Institute; ASU School of Earth and Space Exploration
Category: Astrophysics

We present stellar population modeling results for 10 newly discovered Lyman alpha emitting galaxies (LAEs), as well as four previously known LAEs at z ~ 4.5 in the Chandra Deep Field - South. We fit stellar population models to these objects in order to learn specifically if there exists more than one class of LAE. Read More

We present the faintest spectroscopically confirmed sample of redshift four and five Lyman break galaxies to date. The sample is based on slitless grism spectra of the Hubble Ultra Deep Field region from the GRAPES (Grism ACS Program for Extragalactic Science) and PEARS (Probing Evolution and Reionization Spectroscopically) projects, using the G800L grism on the HST Advanced Camera for Surveys. We report here confirmations of 39 galaxies, pre-selected as candidate Lyman break galaxies using photometric selection criteria. Read More