K. Glazebrook

Publications (104)80.98 Total impact

• Article: Discovery of Lyman Break Galaxies at z~7 from the ZFOURGE Survey

  V. Tilvi, C. Papovich, K. -V. H. Tran, I. Labbe, L. R. Spitler, C. M. S. Straatman, S. E. Persson, A. Monson, K. Glazebrook, R. F. Quadri, [......], H. C. Ferguson, N. A. Grogin, G. G. Kacprzak, D. D. Kelson, A. M. Koekemoer, D. Murphy, P. J. McCarthy, J. A. Newman, B. Salmon, S. P. Willner
  [show abstract] [hide abstract]
  ABSTRACT: Star-forming galaxies at redshifts z>6 are likely responsible for the reionization of the universe, and it is important to study the nature of these galaxies. We present three candidates for z~7 Lyman-break galaxies (LBGs) from a 155 arcmin^2 area in the CANDELS/COSMOS field imaged by the deep FourStar Galaxy Evolution (zFourGE) survey. The FourStar medium-band filters provide the equivalent of R~10 spectroscopy, which cleanly distinguishes between z~7 LBGs and brown dwarf stars. The distinction between stars and galaxies based on an object's angular size can become unreliable even when using HST imaging; there exists at least one very compact z~7 candidate (FWHM~0.5-1 kpc) that is indistinguishable from a point source. The medium-band filters provide narrower redshift distributions compared with broad-band-derived redshifts. The UV luminosity function derived using the three z~7 candidates is consistent with previous studies, suggesting an evolution at the bright end (MUV -21.6 mag) from z~7 to z~5. Fitting the galaxies' spectral energy distributions, we predict Lyman-alpha equivalent widths for the two brightest LBGs, and find that the presence of a Lyman-alpha line affects the medium-band flux thereby changing the constraints on stellar masses and UV spectral slopes. This illustrates the limitations of deriving LBG properties using only broad-band photometry. The derived specific star-formation rates for the bright LBGs are ~13 per Gyr, slightly higher than the lower-luminosity LBGs, implying that the star-formation rate increases with stellar mass for these galaxies.
  04/2013;
• Article: Suppression of the near-infrared OH night sky lines with fibre Bragg gratings - first results

  S. C. Ellis, J. Bland-Hawthorn, J. Lawrence, A. J. Horton, C. Trinh, S. G. Leon-Saval, K. Shortridge, J. Bryant, S. Case, M. Colless, [......], K. Glazebrook, R. Haynes, S. Lee, H. -G. Loehmannsroeben, J. O. Byrne, S. Miziarski, M. Roth, B. Schmidt, C. G. Tinney, J. Zheng
  [show abstract] [hide abstract]
  ABSTRACT: The background noise between 1 and 1.8 microns in ground-based instruments is dominated by atmospheric emission from hydroxyl molecules. We have built and commissioned a new instrument, GNOSIS, which suppresses 103 OH doublets between 1.47 - 1.7 microns by a factor of ~1000 with a resolving power of ~10,000. We present the first results from the commissioning of GNOSIS using the IRIS2 spectrograph at the AAT. The combined throughput of the GNOSIS fore-optics, grating unit and relay optics is ~36 per cent, but this could be improved to ~46 per cent with a more optimal design. We measure strong suppression of the OH lines, confirming that OH suppression with fibre Bragg gratings will be a powerful technology for low resolution spectroscopy. The integrated OH suppressed background between 1.5 and 1.7 microns is reduced by a factor of 9 compared to a control spectrum using the same system without suppression. The potential of low resolution OH suppressed spectroscopy is illustrated with example observations. The GNOSIS background is dominated by detector dark current below 1.67 microns and by thermal emission above 1.67 microns. After subtracting these we detect an unidentified residual interline component of ~ 860 +/ 210 ph/s/m^2/micron/arcsec^2. This component is equally bright in the suppressed and control spectra. We have investigated the possible source of the interline component, but were unable to discriminate between a possible instrumental artifact and intrinsic atmospheric emission. Resolving the source of this emission is crucial for the design of fully optimised OH suppression spectrographs. The next generation OH suppression spectrograph will be focussed on resolving the source of the interline component, taking advantage of better optimisation for a FBG feed. We quantify the necessary improvements for an optimal OH suppressing fibre spectrograph design.
  06/2012;
• Article: On the Shapes and Structures of High-Redshift Compact Galaxies

  M. Chevance, A. Weijmans, I. Damjanov, R. G. Abraham, L. Simard, S. van den Bergh, E. Caris, K. Glazebrook
  [show abstract] [hide abstract]
  ABSTRACT: Recent deep Hubble Space Telescope WFC3 imaging suggests that a majority of compact quiescent massive galaxies at z~2 may contain disks. To investigate this claim, we have compared the ellipticity distribution of 31 carefully selected high-redshift massive quiescent compact galaxies to a set of mass-selected ellipticity and Sersic index distributions obtained from 2D structural fits to ~40,000$ nearby galaxies from the Sloan Digital Sky Survey. A Kolmogorov-Smirnov test shows that the distribution of ellipticities for the high-redshift galaxies is consistent with the ellipticity distribution of a similarly chosen sample of massive early-type galaxies. However the distribution of Sersic indices for the high-redshift sample is inconsistent with that of local early-type galaxies, and instead resembles that of local disk-dominated populations. The mismatch between the properties of high-redshift compact galaxies and those of both local early-type and disk-dominated systems leads us to conclude that the basic structures of high-redshift compact galaxies probably do not closely resemble those of any single local galaxy population. Any galaxy population analog to the high-redshift compact galaxies that exists at the current epoch is either a mix of different types of galaxies, or possibly a unique class of objects on their own.
  06/2012;
• Article: An Efficient Approach to Obtaining Large Numbers of Distant Supernova Host Galaxy Redshifts

  C. Lidman, V. Ruhlmann-Kleider, M. Sullivan, J. Myzska, P. Dobbie, K. Glazebrook, J. Mould, P. Astier, C. Balland, M. Betoule, [......], J. Guy, D. Hardin, I. Hook, D. A. Howell, R. Pain, N. Palanque-Delabrouille, K. Perrett, C. Pritchet, N. Regnault, J. Rich
  [show abstract] [hide abstract]
  ABSTRACT: We use the wide-field capabilities of the 2dF fibre positioner and the AAOmega spectrograph on the Anglo-Australian Telescope (AAT) to obtain redshifts of galaxies that hosted supernovae during the first three years of the Supernova Legacy Survey (SNLS). With exposure times ranging from 10 to 60 ksec per galaxy, we were able to obtain redshifts for 400 host galaxies in two SNLS fields, thereby substantially increasing the total number of SNLS supernovae with host galaxy redshifts. The median redshift of the galaxies in our sample that hosted photometrically classified Type Ia supernovae (SNe Ia) is 0.77, which is 25% higher than the median redshift of spectroscopically confirmed SNe Ia in the three-year sample of the SNLS. Our results demonstrate that one can use wide-field fibre-fed multi-object spectrographs on 4m telescopes to efficiently obtain redshifts for large numbers of supernova host galaxies over the large areas of sky that will be covered by future high-redshift supernova surveys, such as the Dark Energy Survey.
  05/2012;
• Source

  Available from: caltech.edu

  Article: Afterglow Observations of Fermi Large Area Telescope Gamma-ray Bursts and the Emerging Class of Hyper-energetic Events

  S. B. Cenko, D. A. Frail, F. A. Harrison, J. B. Haislip, D. E. Reichart, N. R. Butler, B. E. Cobb, A. Cucchiara, E. Berger, J. S. Bloom, [......], A. V. Filippenko, K. Glazebrook, K. M. Ivarsen, M. M. Kasliwal, S. R. Kulkarni, A. P. LaCluyze, S. Lopez, A. N. Morgan, M. Pettini, and V. R. Rana
  [show abstract] [hide abstract]
  ABSTRACT: We present broadband (radio, optical, and X-ray) light curves and spectra of the afterglows of four long-duration gamma-ray bursts (GRBs; GRBs 090323, 090328, 090902B, and 090926A) detected by the Gamma-Ray Burst Monitor and Large Area Telescope (LAT) instruments on the Fermi satellite. With its wide spectral bandpass, extending to GeV energies, Fermi is sensitive to GRBs with very large isotropic energy releases (1054 erg). Although rare, these events are particularly important for testing GRB central-engine models. When combined with spectroscopic redshifts, our afterglow data for these four events are able to constrain jet collimation angles, the density structure of the circumburst medium, and both the true radiated energy release and the kinetic energy of the outflows. In agreement with our earlier work, we find that the relativistic energy budget of at least one of these events (GRB 090926A) exceeds the canonical value of 1051 erg by an order of magnitude. Such energies pose a severe challenge for models in which the GRB is powered by a magnetar or a neutrino-driven collapsar, but remain compatible with theoretical expectations for magnetohydrodynamical collapsar models (e.g., the Blandford-Znajek mechanism). Our jet opening angles (θ) are similar to those found for pre-Fermi GRBs, but the large initial Lorentz factors (Γ0) inferred from the detection of GeV photons imply θΓ0 70-90, values which are above those predicted in magnetohydrodynamic models of jet acceleration. Finally, we find that these Fermi-LAT events preferentially occur in a low-density circumburst environment, and we speculate that this might result from the lower mass-loss rates of their lower-metallicity progenitor stars. Future studies of Fermi-LAT afterglows at radio wavelengths with the order-of-magnitude improvement in sensitivity offered by the Extended Very Large Array should definitively establish the relativistic energy budgets of these events.
  The Astrophysical Journal 04/2011; 732(1):29. · 6.02 Impact Factor
• Source

  Available from: Joshua B. Haislip

  Article: Afterglow Observations of Fermi-LAT Gamma-Ray Bursts and the Emerging Class of Hyper-Energetic Events

  S. B. Cenko, D. A. Frail, F. A. Harrison, J. B. Haislip, D. E. Reichart, N. R. Butler, B. E. Cobb, A. Cucchiara, E. Berger, J. S. Bloom, [......], A. V. Filippenko, K. Glazebrook, K. M. Ivarsen, M. M. Kasliwal, S. R. Kulkarni, A. P. LaCluyze, S. Lopez, A. N. Morgan, M. Pettini, V. R. Rana
  [show abstract] [hide abstract]
  ABSTRACT: We present broadband (radio, optical, and X-ray) light curves and spectra of the afterglows of four long-duration gamma-ray bursts (GRBs 090323, 090328, 090902B, and 090926A) detected by the Gamma-Ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on the Fermi satellite. With its wide spectral bandpass, extending to GeV energies, Fermi is sensitive to GRBs with very large isotropic energy releases (10e54 erg). Although rare, these events are particularly important for testing GRB central-engine models. When combined with spectroscopic redshifts, our afterglow data for these four events are able to constrain jet collimation angles, the density structure of the circumburst medium, and both the true radiated energy release and the kinetic energy of the outflows. In agreement with our earlier work, we find that the relativistic energy budget of at least one of these events (GRB 090926A) exceeds the canonical value of 10e51 erg by an order of magnitude. Such energies pose a severe challenge for models in which the GRB is powered by a magnetar or neutrino-driven collapsar, but remain compatible with theoretical expectations for magneto-hydrodynamical (MHD) collapsar models. Our jet opening angles (theta) are similar to those found for pre-Fermi GRBs, but the large initial Lorentz factors (Gamma_0) inferred from the detection of GeV photons imply theta Gamma_0 ~ 70-90, values which are above those predicted in MHD models of jet acceleration. Finally, we find that these Fermi-LAT events preferentially occur in a low-density circumburst environment, and we speculate that this might result from the lower mass-loss rates of their lower-metallicity progenitor stars. Future studies of Fermi-LAT afterglows in the radio with the order-of-magnitude improvement in sensitivity offered by the EVLA should definitively establish the relativistic energy budgets of these events. Comment: 29 pages, 11 figures, submitted to ApJ. Comments welcome. v2 - Minor typos corrected.
  04/2010;
• Source

  Available from: ArXiv

  Article: The Science Case for PILOT II: the Distant Universe

  J. S. Lawrence, M. C. B. Ashley, A. Bunker, R. Bouwens, D. Burgarella, M. G. Burton, N. Gehrels, K. Glazebrook, K. Pimbblet, R. Quimby, W. Saunders, J. W. V. Storey, J. C. Wheeler
  [show abstract] [hide abstract]
  ABSTRACT: PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed 2.5 m optical/infrared telescope to be located at Dome C on the Antarctic plateau. The atmospheric conditions at Dome C deliver a high sensitivity, high photometric precision, wide-field, high spatial resolution, and high-cadence imaging capability to the PILOT telescope. These capabilities enable a unique scientific potential for PILOT, which is addressed in this series of papers. The current paper presents a series of projects dealing with the distant (redshift >) Universe, that have been identified as key science drivers for the PILOT facility. The potential for PILOT to detect the first populations of stars to form in the early Universe, via infrared projects searching for pair-instability supernovae and gamma-ray burst afterglows, is investigated. Two projects are proposed to examine the assembly and evolution of structure in the Universe: an infrared survey searching for the first evolved galaxies at high redshift, and an optical survey aimed at characterising moderate-redshift galaxy clusters. Finally, a large-area weak-lensing survey and a program to obtain supernovae infrared light-curves are proposed to examine the nature and evolution of dark energy and dark matter. Comment: 19 pages, 14 figures, accepted for publication in PASA
  05/2009;
• Source

  Available from: Paolo Persi

  Article: The Science Case for PILOT I: Summary and Overview

  J. S. Lawrence, M. C. B. Ashley, J Bailey, D. Barrado y Navascues, T. Bedding, J. Bland-Hawthorn, I. Bond, F. Boulanger, R. Bouwens, H. Bruntt, [......], K. Pimbblet, R. Quimby, W. Saunders, B Schmidt, D. Stello, J. W. V. Storey, C. Tinney, P. Tremblin, J. C. Wheeler, P. Yoc
  [show abstract] [hide abstract]
  ABSTRACT: PILOT (the Pathfinder for an International Large Optical Telescope) is a proposed 2.5 m optical/infrared telescope to be located at Dome C on the Antarctic plateau. Conditions at Dome C are known to be exceptional for astronomy. The seeing (above ~30 m height), coherence time, and isoplanatic angle are all twice s good as at typical mid-latitude sites, while the water-vapour column, and the atmosphere and telescope thermal emission are all an order of magnitude better. These conditions enable a unique scientific capability for PILOT, which is addressed in this series of papers. The current paper presents an overview of the optical and instrumentation suite for PILO and its expected performance, a summary of the key science goals and observational approach for the facility, a discussion of the synergies between the science goals for PILOT and other telescopes, and a discussion of the future of Antarctic astronomy. Paper II and Paper III present details of the science projects divided, respectively, between the distant Universe (i.e., studies of first light, and the assembly and evolution of structure) and the nearby Universe (i.e., studies of Local Group galaxies, the Milky Way, and the Solar System). Comment: 19 pages, 8 figures, accepted for publication in PASA
  05/2009;
• Source

  Available from: arxiv.org

  Article: A near-infrared excess in the continuum of high-redshift galaxies: a tracer of star formation and circumstellar disks?

  E. Mentuch, R. G. Abraham, K. Glazebrook, P. J. McCarthy, H Yan, D. V. O'Donnell, D. Le Borgne, S. Savaglio, D. Crampton, R. Murowinski, S. Juneau, R. G. Carlberg, I. Jorgensen, K. Roth, H Chen, R. O. Marzke
  [show abstract] [hide abstract]
  ABSTRACT: A broad continuum excess in the near-infrared, peaking in the rest-frame at 2-5 micron, is detected in a spectroscopic sample of 88 galaxies at 0.5<z<2.0 taken from the Gemini Deep Deep Survey. Line emission from polycyclic aromatic hydrocarbons (PAHs) at 3.3 micron alone cannot explain the excess, which can be fit by a spectral component consisting of a template of PAH emission lines superposed on a modified blackbody of temperature T~850 K. The luminosity of this near-infrared excess emission at 3 micron is found to be correlated with the star formation rate of the galaxy. The origin of the near-infrared excess is explored by examining similar excesses observed locally in massive star forming regions, reflection and planetary nebulae, post-asymptotic giant branch stars and in the galactic cirrus. We also consider the potential contribution from dust heated around low-luminosity active galactic nuclei. We conclude that the most likely explanation for the 2-5 micron excess is the contribution from circumstellar disks around massive young stellar objects seen in the integrated light of high-redshift galaxies. Assuming circumstellar disks extend down to lower masses, as they do in our own Galaxy, the excess emission presents us with an exciting opportunity to measure the formation rate of planetary systems at cosmic epochs before our own solar system formed. Comment: 17 pages, 12 Figures, Accepted to ApJ
  05/2009;
• Source

  Available from: ArXiv

  Article: The Host Galaxies of Swift Dark Gamma-Ray Bursts: Observational Constraints on Highly Obscured and Very High-Redshift GRBs

  D. A. Perley, S. B. Cenko, J. S. Bloom, H. -W. Chen, N. R. Butler, D. Kocevski, J. X. Prochaska, M. Brodwin, K. Glazebrook, M. M. Kasliwal, S. R. Kulkarni, S. Lopez, E. O. Ofek, M. Pettini, A. M. Soderberg, D. Starr
  [show abstract] [hide abstract]
  ABSTRACT: In this work we present the first results of our imaging campaign at Keck Observatory to identify the host galaxies of "dark" gamma-ray bursts (GRBs), events with no detected optical afterglow or with detected optical flux significantly fainter than expected from the observed X-ray afterglow. We find that out of a uniform sample of 29 Swift bursts rapidly observed by the Palomar 60-inch telescope through March 2008 (14 of which we classify as dark), all events have either a detected optical afterglow, a probable optical host-galaxy detection, or both. Our results constrain the fraction of Swift GRBs coming from very high redshift (z > 7), such as the recent GRB 090423, to between 0.2-7 percent at 80% confidence. In contrast, a significant fraction of the sample requires large extinction columns (host-frame A_V > 1 mag, with several events showing A_V > 2-6 mag), identifying dust extinction as the dominant cause of the dark GRB phenomenon. We infer that a significant fraction of GRBs (and, by association, of high-mass star formation) occurs in highly obscured regions. However, the host galaxies of dark GRBs seem to have normal optical colors, suggesting that the source of obscuring dust is local to the vicinity of the GRB progenitor or highly unevenly distributed within the host galaxy. Comment: 21 pages, 10 figures. Published in AJ
  05/2009;
• Article: GRB 080503: Implications of a Naked Short Gamma-Ray Burst Dominated by Extended Emission

  D. A. Perley, B. D. Metzger, J. Granot, N. R. Butler, T. Sakamoto, E. Ramirez-Ruiz, A. J. Levan, J. S. Bloom, A. A. Miller, A. Bunker, [......], K. C. Hurley, D. Kocevski, W. Li, S. Lopez, J. Norris, A. L. Piro, D. Poznanski, J. X. Prochaska, E. Quataert, and N. Tanvir
  [show abstract] [hide abstract]
  ABSTRACT: We report on observations of GRB 080503, a short gamma-ray burst (GRB) with very bright extended emission (about 30 times the gamma-ray fluence of the initial spike) in conjunction with a thorough comparison to other short Swift events. In spite of the prompt-emission brightness, however, the optical counterpart is extraordinarily faint, never exceeding 25 mag in deep observations starting at ~1 hr after the Burst Alert Telescope (BAT) trigger. The optical brightness peaks at ~1 day and then falls sharply in a manner similar to the predictions of Li & Paczyński (1998) for supernova-like emission following compact binary mergers. However, a shallow spectral index and similar evolution in X-rays inferred from Chandra observations are more consistent with an afterglow interpretation. The extreme faintness of this probable afterglow relative to the bright gamma-ray emission argues for a very low density medium surrounding the burst (a "naked" GRB), consistent with the lack of a coincident host galaxy down to 28.5 mag in deep Hubble Space Telescope imaging. The late optical and X-ray peak could be explained by a slightly off-axis jet or by a refreshed shock. Our observations reinforce the notion that short GRBs generally occur outside regions of active star formation, but demonstrate that in some cases the luminosity of the extended prompt emission can greatly exceed that of the short spike, which may constrain theoretical interpretation of this class of events. This extended emission is not the onset of an afterglow, and its relative brightness is probably either a viewing-angle effect or intrinsic to the central engine itself. Because most previous BAT short bursts without observed extended emission are too faint for this signature to have been detectable even if it were present at typical level, conclusions based solely on the observed presence or absence of extended emission in the existing Swift sample are premature.
  The Astrophysical Journal 04/2009; 696(2):1871. · 6.02 Impact Factor
• Article: Unveiling the dynamics of galaxies with SPIRAL

  A. Green, K. Glazebrook, G. Poole, P. McGregor, B. Abraham, I. Damjanov, P. McCarthy, R. Sharp
  Anglo-Australian Observatory Epping Newsletter. 01/2009; 115:10.
• Source

  Available from: psu.edu

  Article: Measurements of the Cosmological Parameters Ω and Λ from the First Seven Supernovae at z ≥ 0.35

  S. Perlmutter, S. Gabi, G. Goldhaber, A. Goobar, E. Groom, M. Hook, G. Kim, Y. Kim, C. Lee, R. Pain, [......], J. Boyle, S. Bunclark, D. Carter, J. Irwin, K. Glazebrook, M. Newberg, V. Filippenko, T. Matheson, M. Dopita, J. Couch
  [show abstract] [hide abstract]
  ABSTRACT: We have developed a technique to systematically discover and study high-redshift supernovae that can be used to measure the cosmological parameters. We report here results based on the initial seven of more than 28 supernovae discovered to date in the high-redshift supernova search of the Supernova Cosmology Project. We find an observational dispersion in peak magnitudes of σMB=0.27; this dispersion narrows to σMB, corr=0.19 after "correcting" the magnitudes using the light-curve "width-luminosity" relation found for nearby (z ≤ 0.1) Type Ia supernovae from the Calán/Tololo survey (Hamuy et al.). Comparing light-curve width-corrected magnitudes as a function of redshift of our distant (z = 0.35-0.46) supernovae to those of nearby Type Ia supernovae yields a global measurement of the mass density, ΩM=0.88+ 0.69−0.60 for a Λ = 0 cosmology. For a spatially flat universe (i.e., ΩM + ΩΛ = 1), we find ΩM=0.94+ 0.34−0.28 or, equivalently, a measurement of the cosmological constant, ΩΛ=0.06+ 0.28−0.34 ( < 0.51 at the 95% confidence level). For the more general Friedmann-Lemaître cosmologies with independent ΩM and ΩΛ, the results are presented as a confidence region on the ΩM-ΩΛ plane. This region does not correspond to a unique value of the deceleration parameter q0. We present analyses and checks for statistical and systematic errors and also show that our results do not depend on the specifics of the width-luminosity correction. The results for ΩΛ-versus-ΩM are inconsistent with Λ-dominated, low-density, flat cosmologies that have been proposed to reconcile the ages of globular cluster stars with higher Hubble constant values.
  The Astrophysical Journal 01/2009; 483(2):565. · 6.02 Impact Factor
• Source

  Available from: D. A. Kann

  Article: Observations of the Naked-Eye GRB 080319B: Implications of Nature's Brightest Explosion

  J. S. Bloom, D. A. Perley, W. Li, N. R. Butler, A. A. Miller, D. Kocevski, D. A. Kann, R. J. Foley, H.-W. Chen, A. V. Filippenko, [......], B. Macomber, J. X. Prochaska, R. Chornock, D. Poznanski, S. Klose, M. F. Skrutskie, S. Lopez, P. Hall, K. Glazebrook, and C. H. Blake
  [show abstract] [hide abstract]
  ABSTRACT: The first gamma-ray burst (GRB) confirmed to be bright enough to be seen with the naked eye, GRB 080319B at redshift z = 0.937, allowed for exquisite follow-up observations across the electromagnetic spectrum. We present our detailed optical and infrared (IR) observations of the afterglow, consisting of over 5000 images starting 51 s after the GRB trigger, in concert with our own analysis of the Swift UVOT, Burst Alert Telescope (BAT), and XRT data. The event is extreme not only in observed properties but also intrinsically: it was the most luminous event ever recorded at optical and IR wavelengths and had an exceedingly high isotropic-equivalent energy release in γ-rays. At early times, the afterglow evolution is broadly consistent with being reverse-shock dominated, but then is subsumed by a forward shock at around 1000 s. The overall spectral energy distribution, spanning from ultraviolet through near-IR wavelengths, shows no evidence for a significant amount of dust extinction in the host frame. The afterglow evolution, however, is highly chromatic: starting at about 1000 s the index shifts blueward before shifting back to the red at late times. In our deepest late-time observations, we find tentative evidence for an optical jet break and a luminous supernova. Finally, we examine the detectability of such events with current and future facilities and find that such an event could be detected in gamma rays by BAT out to z = 10.7 (8σ), while the nominal EXIST sensitivity would allow detection to z 32. At the K band, this source would have been easily detected with meter-class telescopes to z 17.
  The Astrophysical Journal 01/2009; 691(1):723. · 6.02 Impact Factor
• Article: The Hawaii+Anglo-Australian Observatory K-Band Galaxy Redshift Survey. I. The Local K-Band Luminosity Function

  J.-S. Huang, K. Glazebrook, L.L. Cowie, and C. Tinney
  [show abstract] [hide abstract]
  ABSTRACT: We present the K-band local luminosity function derived from a sample of 1056 bright (K < 15) K-selected galaxies from the Hawaii+Anglo-Australian Observatory (AAO) K-band redshift survey. The Hawaii+AAO K-band redshift survey covers four equatorial fields with a total area of 8.22 deg2. We derive both the nonparametric and Schechter luminosity function from our data and determine M*(K) = -23.70 ± 0.08 + 5 log10(h), α = -1.37 ± 0.10, and * = 0.013 ± 0.003 h3 Mpc-3 for a universe with Ωm = 0.3 and ΩΛ = 0.7. We also measure the K-band luminosity function for the early- and later type galaxies from our morphologically classified subsample. It appears that later type galaxies have a fainter M* and a steep slope, while early-type galaxies have a much brighter M* and a quite flat slope in their K-band luminosity functions. This is consistent with what has been found in optical-type dependent luminosity function. The K-band luminosity density derived using our luminosity function is now measured at a similar redshift depth to optical luminosity densities in the Sloan Digital Sky Survey redshift survey. It is 2 times higher than the previous measurement from the shallower 2MASS sample and resolves the previously reported discrepancies between optical and near-infrared luminosity densities.
  The Astrophysical Journal 12/2008; 584(1):203. · 6.02 Impact Factor
• Source

  Available from: ArXiv

  Article: GRB 080503: Implications of a Naked Short Gamma-Ray Burst Dominated by Extended Emission

  D. A. Perley, B. D. Metzger, J. Granot, N. R. Butler, T Sakamoto, E. Ramirez-Ruiz, A. J. Levan, J. S. Bloom, A. A. Miller, A. Bunker, [......], K. C. Hurley, D. Kocevski, W Li, S. Lopez, J. Norris, A. L. Piro, D. Poznanski, J. X. Prochaska, E. Quataert, N. Tanvir
  [show abstract] [hide abstract]
  ABSTRACT: We report on observations of GRB 080503, a short gamma-ray burst with very bright extended emission (about 30 times the gamma-ray fluence of the initial spike) in conjunction with a thorough comparison to other short Swift events. In spite of the prompt-emission brightness, however, the optical counterpart is extraordinarily faint, never exceeding 25 mag in deep observations starting at ~1 hr after the BAT trigger. The optical brightness peaks at ~1 day and then falls sharply in a manner similar to the predictions of Li & Paczynski (1998) for supernova-like emission following compact-binary mergers. However, a shallow spectral index and similar evolution in X-rays inferred from Chandra observations are more consistent with an afterglow interpretation. The extreme faintness of this probable afterglow relative to the bright gamma-ray emission argues for a very low-density medium surrounding the burst (a "naked" GRB), consistent with the lack of a coincident host galaxy down to 28.5 mag in deep HST imaging. Our observations reinforce the notion that short GRBs generally occur outside regions of active star formation, but demonstrate that in some cases the luminosity of the extended prompt emission can greatly exceed that of the short spike, which may constrain theoretical interpretation of this class of events. Because most previous BAT short bursts without observed extended emission are too faint for this signature to have been detectable even if it were present at typical level, conclusions based solely on the observed presence or absence of extended emission in the existing Swift sample are premature. (abridged) Comment: 16 pages, 11 figures; accepted for publication in ApJ
  11/2008;
• Source

  Available from: Simon P. Driver

  Article: On the galaxy stellar mass function, the mass-metallicity relation, and the implied baryonic mass function

  I. K. Baldry, K. Glazebrook, S. P. Driver
  [show abstract] [hide abstract]
  ABSTRACT: A comparison between published field galaxy stellar mass functions (GSMFs) shows that the cosmic stellar mass density is in the range 4--8 per cent of the baryon density (assuming Omega_b = 0.045). There remain significant sources of uncertainty for the dust correction and underlying stellar mass-to-light ratio even assuming a reasonable universal stellar initial mass function. We determine the z < 0.05 GSMF using the New York University - Value-Added Galaxy Catalog sample of 49968 galaxies derived from the Sloan Digital Sky Survey and various estimates of stellar mass. The GSMF shows clear evidence for a low-mass upturn and is fitted with a double Schechter function that has alpha_2 =~ -1.6. At masses below ~ 10^8.5 Msun, the GSMF may be significantly incomplete because of missing low surface-brightness galaxies. One interpretation of the stellar mass-metallicity relation is that it is primarily caused by a lower fraction of available baryons converted to stars in low-mass galaxies. Using this principal, we determine a simple relationship between baryonic mass and stellar mass and present an `implied baryonic mass function'. This function has a faint-end slope, alpha_2 =~ -1.9. Thus, we find evidence that the slope of the low-mass end of the galaxy mass function could plausibly be as steep as the halo mass function. We illustrate the relationship between halo baryonic mass function --> galaxy baryonic mass function --> GSMF. This demonstrates the requirement for peak galaxy formation efficiency at baryonic masses ~ 10^11 Msun corresponding to a minimum in feedback effects. The baryonic-infall efficiency may have levelled off at lower masses. Comment: Changes to section 4.3 and figs 12, 13; 15 pages (10 pages excluding Appendix and refs), accepted by MNRAS; binned GSMF data file is available at http://www.astro.ljmu.ac.uk/~ikb/research/gsmf-paper.html
  04/2008;
• Source

  Available from: ArXiv

  Article: The Galaxy Population Hosting Gamma-Ray Bursts

  S. Savaglio, K. Glazebrook, D. Le Borgne
  [show abstract] [hide abstract]
  ABSTRACT: We present the most extensive and complete study of the properties for the largest sample (46 objects) of gamma-ray burst (GRB) host galaxies. The redshift interval and the mean redshift of the sample are 0<z<6.3 and z=0.96 (look-back time: 7.2 Gyr), respectively; 89% of the hosts are at z <~ 1.6. Optical-near-infrared (NIR) photometry and spectroscopy are used to derive stellar masses, star formation rates (SFRs), dust extinctions and metallicities. The average stellar mass is 10^9.3 M_sun, with a 1 sigma dispersion of 0.8 dex. The average metallicity for a subsample of 17 hosts is about 1/6 solar and the dust extinction in the visual band (for a subsample of 10 hosts) is A_V=0.5. We obtain new relations to derive SFR from [OII] or UV fluxes, when Balmer emission lines are not available. SFRs, corrected for dust extinction, aperture-slit loss and stellar Balmer absorption are in the range 0.01-36 M_sun yr^-1. The median SFR per unit stellar mass (specific SFR) is 0.8 Gyr^-1. Equivalently the inverse quantity, the median formation timescale is 1.3 Gyr. Most GRBs are associated with the death of young massive stars, more common in star-forming galaxies. Therefore GRBs are an effective tool to detect star-forming galaxies in the universe. Star-forming galaxies at z<1.6 are a faint and low-mass population, hard to detect by conventional optical-NIR surveys, unless a GRB event occurs. There is no compelling evidence that GRB hosts are peculiar galaxies. More data on the subclass of short GRB are necessary to establish the nature of their hosts. Comment: 33 pages, 18 figures, 11 tables, final version to appear in ApJ, January 20 issue. Figure 18 corrected
  03/2008;
• Article: Near-Infrared Photometry and Spectroscopy of L and T Dwarfs: The Effects of Temperature, Clouds, and Gravity

  G. R. Knapp, S. K. Leggett, X. Fan, M. S. Marley, T. R. Geballe, D. A. Golimowski, D. Finkbeiner, J. E. Gunn, J. Hennawi, Z. Ivezić, [......], C. C. Williams, A. Uomoto, F. J. Vrba, A. A. Henden, C. B. Luginbuhl, H. H. Guetter, J. A. Munn, B. Canzian, Donald P. Schneider, and J. Brinkmann
  [show abstract] [hide abstract]
  ABSTRACT: We present new JHK photometry on the MKO-NIR system and JHK spectroscopy for a large sample of L and T dwarfs. Photometry has been obtained for 71 dwarfs, and spectroscopy for 56. The sample comprises newly identified very red objects from the Sloan Digital Sky Survey (SDSS) and known dwarfs from the SDSS and the Two Micron All Sky Survey (2MASS). Spectral classification has been carried out using four previously defined indices from Geballe et al. that measure the strengths of the near infrared water and methane bands. We identify nine new L8–9.5 dwarfs and 14 new T dwarfs from SDSS, including the latest yet found by SDSS, the T7 dwarf SDSS J175805.46+463311.9. We classify 2MASS J04151954-0935066 as T9, the latest and coolest dwarf found to date. We combine the new results with our previously published data to produce a sample of 59 L dwarfs and 42 T dwarfs with imaging data on a single photometric system and with uniform spectroscopic classification. We compare the near-infrared colors and absolute magnitudes of brown dwarfs near the L–T transition with predictions made by models of the distribution and evolution of photospheric condensates. There is some scatter in the Geballe et al. spectral indices for L dwarfs, suggesting that these indices are probing different levels of the atmosphere and are affected by the location of the condensate cloud layer. The near-infrared colors of the L dwarfs also show scatter within a given spectral type, which is likely due to variations in the altitudes, spatial distributions, and thicknesses of the clouds. We have identified a small group of late-L dwarfs that are relatively blue for their spectral type and that have enhanced FeH, H2O, and K I absorption, possibly due to an unusually small amount of condensates. The scatter seen in the H-K color for late-T dwarfs can be reproduced by models with a range in surface gravity. The variation is probably due to the effect on the K-band flux of pressure-induced H2 opacity. The correlation of H-K color with gravity is supported by the observed strengths of the J-band K I doublet. Gravity is closely related to mass for field T dwarfs with ages greater than108 yr and the gravities implied by the H-K colors indicate that the T dwarfs in our sample have masses in the range 15–75MJupiter. One of the SDSS dwarfs, SDSS J111010.01+011613.1, is possibly a very low mass object, with log g ~ 4.2–4.5 and mass ~ 10–15MJupiter.
  The Astronomical Journal 12/2007; 127(6):3553. · 4.03 Impact Factor
• Source

  Available from: ArXiv

  Article: L' and M' Photometry of Ultracool Dwarfs

  D. A. Golimowski, S. K. Leggett, M. S. Marley, X. Fan, T. R. Geballe, G. R. Knapp, F. J. Vrba, A. A. Henden, C. B. Luginbuhl, H. H. Guetter, J. A. Munn, B. Canzian, W. Zheng, Z. I. Tsvetanov, K. Chiu, K. Glazebrook, E. A. Hoversten, D. P. Schneider, and J. Brinkmann
  [show abstract] [hide abstract]
  ABSTRACT: We have compiled L' (3.4–4.1 μm) and M' (4.6–4.8 μm) photometry of 63 single and binary M, L, and T dwarfs obtained at the United Kingdom Infrared Telescope using the Mauna Kea Observatory filter set. This compilation includes new L' measurements of eight L dwarfs and 13 T dwarfs and new M' measurements of seven L dwarfs, five T dwarfs, and the M1 dwarf Gl 229A. These new data increase by factors of 0.6 and 1.6, respectively, the numbers of ultracool dwarfs (Teff 2400 K) for which L' and M' measurements have been reported. We compute Lbol, BCK, and Teff for 42 dwarfs whose flux-calibrated JHK spectra, L' photometry, and trigonometric parallaxes are available, and we estimate these quantities for nine other dwarfs whose parallaxes and flux-calibrated spectra have been obtained. BCK is a well-behaved function of near-infrared spectral type with a dispersion of ~0.1 mag for types M6–T5; it is significantly more scattered for types T5–T9. Teff declines steeply and monotonically for types M6–L7 and T4–T9, but it is nearly constant at ~1450 K for types L7–T4 with assumed ages of ~3 Gyr. This constant Teff is evidenced by nearly unchanging values of L'–M' between types L6 and T3. It also supports recent models that attribute the changing near-infrared luminosities and spectral features across the L-T transition to the rapid migration, disruption, and/or thinning of condensate clouds over a narrow range of Teff. The L' and M' luminosities of early-T dwarfs do not exhibit the pronounced humps or inflections previously noted in the I through K bands, but insufficient data exist for types L6–T5 to assert that ML' and MM' are strictly monotonic within this range of types. We compare the observed K, L', and M' luminosities of L and T dwarfs in our sample with those predicted by precipitating-cloud and cloud-free models for varying surface gravities and sedimentation efficiencies. The models indicate that the L3–T4.5 dwarfs generally have higher gravities (log g = 5.0–5.5) than the T6–T9 dwarfs (log g = 4.5–5.0). The predicted M' luminosities of late-T dwarfs are 1.5–2.5 times larger than those derived empirically for the late-T dwarfs in our sample. This discrepancy is attributed to absorption at 4.5–4.9 μm by CO, which is not expected under the condition of thermochemical equilibrium assumed in the models. Our photometry and bolometric calculations indicate that the L3 dwarf Kelu-1 and the T0 dwarf SDSS J042348.57-041403.5 are probable binary systems. We compute log (Lbol/L) = -5.73 ± 0.05 and Teff = 600–750 K for the T9 dwarf 2MASSI J0415195-093506, which supplants Gl 570D as the least luminous and coolest brown dwarf presently known.
  The Astronomical Journal 12/2007; 127(6):3516. · 4.03 Impact Factor