H. Spinrad

University of California, Berkeley, Berkeley, California, United States

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Publications (231)683.18 Total impact

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    ABSTRACT: We present the evidence that strong Hα emitters (HAEs) comprise more than 70% of galaxies with spectroscopic redshifts of 3.8 < z < 5.0, from the clear flux excess observed in the Spitzer/IRAC 3.6-μm band. HAEs are strongly star-forming galaxies with star formation rate of 20–500 M⊙yr–1, with unusually large Hα equivalent widths (EW) of > 350 Å. The rest-frame UV to optical morphologies for half of the HAEs do not show any signs of mergers or tidal interactions. The large Hα EW of HAEs despite their relatively old stellar population age suggests that HAEs are producing stars continuously at a constant rate, rather than through multiple bursts invoked by major mergers. The observed number density of HAEs is consistent with the predicted number of halos which have gas infall rate comparable to the observed star formation rate. Therefore, HAEs provide indirect evidence supporting that star formation mechanism other than mergers, such as cold gas accretion, is the dominant driver of star formation at z ˜ 4.
    No preview · Article · Oct 2013
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    ABSTRACT: We use ultra-deep ultraviolet VLT/VIMOS intermediate-band and VLT/FORS1 narrow-band imaging in the GOODS Southern field to derive limits on the distribution of the escape fraction (f_esc) of ionizing radiation for L >~ L*(z=3) Lyman Break Galaxies (LBGs) at redshift 3.4--4.5. Only one LBG, at redshift z=3.795, is detected in its Lyman continuum (LyC; S/N~5.5), the highest redshift galaxy currently known with a direct detection. Its ultraviolet morphology is quite compact (R_eff=0.8, kpc physical). Three out of seven AGN are also detected in their LyC, including one at redshift z=3.951 and z850 = 26.1. From stacked data (LBGs) we set an upper limit to the average f_esc in the range 5%--20%, depending on the how the data are selected (e.g., by magnitude and/or redshift). We undertake extensive Monte Carlo simulations that take into account intergalactic attenuation, stellar population synthesis models, dust extinction and photometric noise in order to explore the moments of the distribution of the escaping radiation. Various distributions (exponential, log-normal and Gaussian) are explored. We find that the median f_esc is lower than ~6% with an 84% percentile limit not larger than 20%. If this result remains valid for fainter LBGs down to current observational limits, then the LBG population might be not sufficient to account for the entire photoionization budget at the redshifts considered here, with the exact details dependent upon the assumed ionizing background and QSO contribution thereto. It is possible that f_esc depends on the UV luminosity of the galaxies, with fainter galaxies having higher f_esc, and estimates of f_esc from a sample of faint LBG from the HUDF (i775<28.5) are in broad quantitative agreement with such a scenario. Comment: 58 pages, 23 figures; submitted to ApJ, revised version in response to referee's comments
    Full-text · Article · Sep 2010 · The Astrophysical Journal
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    ABSTRACT: We report on the identification of the highest redshift submillimetre-selected source currently known LESS J033229.4−275619. This source was detected in the Large Apex Bolometer Camera (LABOCA) Extended Chandra Deep Field-South (ECDF-S) Submillimetre Survey (LESS), a sensitive 870-μm survey (σ870 μm∼ 1.2 mJy) of the full 30 × 30 arcmin2 ECDF-S with the LABOCA on the Atacama Pathfinder Experiment telescope. The submillimetre emission is identified with a radio counterpart for which optical spectroscopy provides a redshift of z= 4.76. We show that the bolometric emission is dominated by a starburst with a star formation rate of ∼1000 M⊙ yr−1, although we also identify a moderate luminosity active galactic nucleus (AGN) in this galaxy. Thus it has characteristics similar to those of z∼ 2 submillimetre galaxies (SMGs), with a mix of starburst and obscured AGN signatures. This demonstrates that ultraluminous starburst activity is not just restricted to the hosts of the most luminous (and hence rare) quasi-stellar objects at z∼ 5, but was also occurring in less extreme galaxies at a time when the Universe was less than 10 per cent of its current age. Assuming that we are seeing the major phase of star formation in this galaxy, then we demonstrate that it would be identified as a luminous distant red galaxy at z∼ 3 and that the current estimate of the space density of z > 4 SMGs is only sufficient to produce ≳10 per cent of the luminous red galaxy population at these early times. However, this leaves open the possibility that some of these galaxies formed through less intense, but more extended star formation events. If the progenitors of all of the luminous red galaxies at z∼ 3 go through an ultraluminous starburst at z≳ 4 then the required volume density of z > 4 SMGs will exceed that predicted by current galaxy formation models by more than an order of magnitude.
    Full-text · Article · May 2009 · Monthly Notices of the Royal Astronomical Society
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    ABSTRACT: We present and discuss optical continuum images made with the Hubble Space Telescope of the radio galaxy 1138-262 at z = 2.2. This object possesses one of the clumpiest optical morphologies of all known high-redshift radio galaxies, consisting of a bright nucleus aligned along the radio axis and a number of smaller components distributed over a region as large as the radio source (130 kpc). The clumps have sizes ranging from 3 to 13 kpc and absolute visual magnitudes between MV = -21.8 and MV = -19.4. On the basis of HST and previous observations, we claim that these clumps are star-forming galaxies that will be accreted by the host galaxy of 1138-262. We compare this radio galaxy with other high-redshift objects and with the predictions of current scenarios of galaxy formation.
    Full-text · Article · Jan 2009 · The Astrophysical Journal
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    ABSTRACT: We have measured the rest-frame λ ~ 1500 Å comoving specific luminosity density of star-forming galaxies at redshift 3.5 < z < 6.5 (Lyman break galaxies [LBGs]) selected from deep, multiband images taken with the Hubble Space Telescope and the Advanced Camera for Surveys, obtained as part of the Great Observatories Origins Deep Survey (GOODS). The samples cover ~0.09 deg2 and are also relatively deep, reaching between 0.2L and 0.5L, depending on the redshift, where L is the characteristic UV luminosity of LBGs at z ~ 3. The specific luminosity density appears to be nearly constant with redshift over the range 3 < z < 6, although the measure at z ~ 6 remains relatively uncertain, because it depends on the accurate estimate of the faint counts of the z ~ 6 sample. If LBGs are fair tracers of the cosmic star formation activity, our results suggest that at z ~ 6, namely, at less than ~7% of the current cosmic age, the universe was already producing stars as vigorously as it did near its maximum several gigayears later, at 1 z 3.
    No preview · Article · Dec 2008 · The Astrophysical Journal
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    ABSTRACT: This special issue of the Astrophysical Journal Letters is dedicated to presenting initial results from the Great Observatories Origins Deep Survey (GOODS) that are primarily, but not exclusively, based on multiband imaging data obtained with the Hubble Space Telescope and the Advanced Camera for Surveys (ACS). The survey covers roughly 320 arcmin2 in the ACS F435W, F606W, F814W, and F850LP bands, divided into two well-studied fields. Existing deep observations from the Chandra X-Ray Observatory and ground-based facilities are supplemented with new, deep imaging in the optical and near-infrared from the European Southern Observatory and from the Kitt Peak National Observatory. Deep observations with the Space Infrared Telescope Facility are scheduled. Reduced data from all facilities are being released worldwide within 3-6 months of acquisition. Together, this data set provides two deep reference fields for studies of distant normal and active galaxies, supernovae, and faint stars in our own Galaxy. This Letter serves to outline the survey strategy and describe the specific data that have been used in the accompanying letters, summarizing the reduction procedures and sensitivity limits.
    Full-text · Article · Dec 2008 · The Astrophysical Journal
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    ABSTRACT: We report early results on galaxies at z ~ 6 selected from Hubble Space Telescope imaging for the Great Observatories Origins Deep Survey. Spectroscopy of one object with the Advanced Camera for Surveys grism and from the Keck and Very Large Telescope observatories shows a strong continuum break and asymmetric line emission, identified as Lyα at z = 5.83. We find only five spatially extended candidates with signal-to-noise ratios greater than 10, two of which have spectroscopic confirmation. This is much fewer than would be expected if galaxies at z = 6 had the same luminosity function as those at z = 3. There are many fainter candidates, but we expect substantial contamination from foreground interlopers and spurious detections. Our best estimates favor a z = 6 galaxy population with fainter luminosities, higher space density, and similar comoving ultraviolet emissivity to that at z = 3, but this depends critically on counts at fluxes fainter than those reliably probed by the current data.
    Full-text · Article · Dec 2008 · The Astrophysical Journal
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    ABSTRACT: We present the serendipitous discovery of molecular gas CO emission lines with the IRAM Plateau de Bure interferometer coincident with two luminous submillimeter galaxies (SMGs) in the Great Observatories Origins Deep Survey North (GOODS-N) field. The identification of the millimeter emission lines as CO[4-3] at z = 4.05 is based on the optical and near-IR photometric redshifts, radio-infrared photometric redshifts, and Keck+DEIMOS optical spectroscopy. These two galaxies include the brightest submillimeter source in the field (GN20; S 850 μm = 20.3 mJy, z CO = 4.055 ± 0.001) and its companion (GN20.2; S 850 μm = 9.9 mJy, z CO = 4.051 ± 0.003). These are among the most distant submillimeter-selected galaxies reliably identified through CO emission and also some of the most luminous known. GN20.2 has a possible additional counterpart and a luminous active galactic nucleus inside its primary counterpart revealed in the radio. Continuum emission of 0.3 mJy at 3.3 mm (0.65 mm in the rest frame) is detected at 5σ for GN20, the first dust continuum detection in an SMG at such long wavelength, unveiling a spectral energy distribution that is similar to local ultra luminous IR galaxies. In terms of CO to bolometric luminosities, stellar mass, and star formation rates (SFRs), these newly discovered z > 4 SMGs are similar to z ~ 2-3 SMGs studied to date. These z ~ 4 SMGs have much higher specific star formation rates than those of typical B-band dropout Lyman break galaxies at the same redshift. The stellar mass-SFR correlation for normal galaxies does not seem to evolve much further, between z ~ 2 and z ~ 4. A significant z = 4.05 spectroscopic redshift spike is observed in GOODS-N, and a strong spatial overdensity of B-band dropouts and IRAC selected z > 3.5 galaxies appears to be centered on the GN20 and GN20.2 galaxies. This suggests a protocluster structure with total mass ~1014M ☉. Using photometry at mid-IR (24 μm), submillimeter (850 μm), and radio (20 cm) wavelengths, we show that reliable photometric redshifts (Δz/(1 + z) ~ 0.1) can be derived for SMGs over 1 z 4. This new photometric redshift technique has been used to provide a first estimate of the space density of 3.5 < z < 6 hyper-luminous starburst galaxies, and to show that they both contribute substantially to the SFR density at early epochs and that they can account for the presence of old galaxies at z ~ 2-3. Many of these high-redshift starbursts will be within reach of Herschel. We find that the criterion S 1.4 GHzS 24 μm, coupled to optical, near-IR and mid-IR photometry, can be used to select z > 3.5 starbursts, regardless of their submillimeter/millimeter emission.
    Full-text · Article · Oct 2008 · The Astrophysical Journal

  • No preview · Article · Jan 2007
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    ABSTRACT: The depth ( ˜ 26 mag) and large contiguous areas ( ˜ 2 x 9 deg2) covered by the NOAO Deep Wide-Field Survey provide an unprecedented opportunity to study the evolution and large-scale spatial distribution of galaxy samples over a large range in redshift. In this talk I will review our studies of two populations, the z ˜3.7 star-forming galaxies and the z ˜1 red galaxy population, and discuss their global properties, spatial distribution and evolution. Our research is supported by the National Optical Astronomy Observatory which is operated by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with the National Science Foundation.
    No preview · Conference Paper · Nov 2006
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    ABSTRACT: We report the discovery of the hottest cluster known at z > 1. It was identified as an extended X-ray source in the XMM Cluster Survey (XCS, Romer et al., 2001) and optical spectroscopy shows that 6 galaxies within a 60 arcsec diameter region lie at z = 1.45 ± 0.01. Hence its redshift is the highest currently known for a spectroscopically-confirmed cluster. Analysis of the X-ray spectra yields kT = 7.9+2.8-1.8 keV (90% confidence) and suggests that it is relatively massive for such a high redshift cluster.We acknowledge financial support from NASA grant NAG-11634 (AKR, RCN, KS, MD, PTPV), The Royal Astronomical Society's Hosie Request (MD, KS), PPARC (ARL, STK, RGM), the NASA XMM program (KS), the Institute of Astronomy at the University of Edinburgh (MD), Liverpool John Moores University (MH), Carnegie Mellon University (KS, AKR), and NSF grant AST-0205960 (MJW).
    No preview · Article · May 2006
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    ABSTRACT: A 172 ks long Chandra exposure was carried out in the LALA-Bootes field and a similar one for the LALA cetus field. These exposure were deep enough to detect LALA sources, if they were type-II quasars. Lyman-alpha emitters found with LALA show high equivalent widths and AGN phenomenon is one explanation. A total of 101 Ly-alpha emitters are covered by the two Chandra images. No Ly-alpha emitters are detected individually or in the co-added X-ray images. Our analysis indicates that fewer than 4.8 Ly-alpha emitters could be possible AGNs based on the upper limit of their average X-ray to Ly-alpha ratio. The two X-ray images are among the deepest taken by Chandra, with a total of 348 X-ray sources detected, similar to the number of X-ray sources in Chandra Deep Field South. We also see field-to-field variations of the hard X-ray source counts in different Chandra fields, due to large scale structure.
    No preview · Conference Paper · May 2004
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    ABSTRACT: Because strong Lyman alpha emission is expected from young star forming galaxies at high redshift, it offers an efficient tool for identifying these galaxies. The Large Area Lyman Alpha survey is one of the first and largest successful searches for Lyman alpha emitting galaxies at high redshift. In the LALA Bootes field (which lies within the NOAO Deep Wide-Field Survey's Bootes field) we have obtained deep narrowband images covering 1/3 square degree in each of eight filters, sampling redshifts z=4.5, 5.7, and 6.5. We focus here on the higher redshift windows, where we have confirmed a luminous Lyman alpha emitting galaxy at z=6.535 and several others in the z=5.7 window. We discuss the physical properties of these objects, including their contribution to star formation rates and metal production. We also discuss the implications of Lyman alpha galaxy observations at z=6.5 for reionization.
    No preview · Conference Paper · May 2004
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    ABSTRACT: We present results of a comprehensive multi-frequency study of the radio galaxy B3 J2330+3927. The 1.9 arcsec wide radio source, consisting of 3 components, is bracketed by 2 objects in our Keck K-band image. Optical and near-IR Keck spectroscopy of these two objects yield z=3.087+/- 0.004. The brightest (K=18.8) object has a standard type II AGN spectrum, and is the most likely location of the AGN, which implies a one-sided jet radio morphology. Deep 113 GHz observations with the IRAM Plateau de Bure Interferometer reveal CO J=4-3 emission, which peaks at the position of the AGN. The CO line is offset by 500 km s-1 from the systemic redshift of the AGN, but corresponds very closely to the velocity shift of an associated HI absorber seen in Lyα. This strongly suggests that both originate from the same gas reservoir surrounding the AGN host galaxy. Simultaneous 230 GHz interferometer observations find a ~ 3 x lower integrated flux density when compared to single dish 250 GHz observations with MAMBO at the IRAM 30 m telescope. This can be interpreted as spatially resolved thermal dust emission at scales of 0.5 arcsec to 6 arcsec. Finally, we present a tau < 1.3% limit to the HI 21 cm absorption against the radio source, which represents the seventh non-detection out of 8 z>2 radio galaxies observed to date with the WSRT. We present mass estimates for the atomic, neutral, and ionized hydrogen, and for the dust, ranging from M(HI )=2x 107 Msun derived from the associated HI absorber in Lya up to M(H_2)=7x 1010 Msun derived from the CO emission. This indicates that the host galaxy is surrounded by a massive reservoir of gas and dust. The K-band companion objects may be concentrations within this reservoir, which will eventually merge with the central galaxy hosting the AGN. Based on observations obtained with the IRAM Plateau de Bure Interferometer, the W. M. Keck telescope, the Westerbork Synthesis Radio Telescope and the Very Large Array.
    Full-text · Article · Apr 2003 · Astronomy and Astrophysics
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    ABSTRACT: We present results of a morphological study of galaxies from SPICES, the Spectroscopic Photometric Infrared-Chosen Extragalactic Survey. SPICES is a deep BRIzJKs imaging and spectroscopic survey covering over 100 arcmin2 spread over four fields. We have extracted a K-selected sample complete to K=20 of over 1700 objects, for which we have obtained 626 spectroscopic redshifts. In addition, we have HST WFPC2 F814W imaging in all four fields. Morphologies for 1139 objects matched between the HST and the K
    No preview · Article · Dec 2002
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    ABSTRACT: Deep spectroscopy of the two Leiden–Berkeley Deep Survey mJy radio galaxies LBDS 53W069 and 53W091 has previously shown them to have old (≳3 Gyr) stellar populations at z≃ 1.5. Here we present the results of Hubble Space Telescope (HST) observations with the Wide Field and Planetary Camera 2 (WFPC2) in F814W and with the Near-Infrared Camera and Multi-Object Spectrograph (NICMOS) in F110W. We find that 53W069 has a de Vaucouleurs r1/4 profile in both the F814W and F110W data, with a mean effective radius of 0.30 ± 0.06 arcsec (2.7 ± 0.5 kpc). The rest-frame U−B colour gradient is consistent with that of present-day ellipticals, requiring a stellar population of supersolar (3 Z⊙) metallicity that formed on a very short time-scale at high redshift (z > 5). 53W091 has a regular r1/4 profile in F110W with an effective radius of 0.32 ± 0.08 arcsec (2.9 ± 0.7 kpc). The F814W profile is more extended and is consistent with the presence of a blue exponential disc that contributes 20 ± 10 per cent of the flux within re. We find a rest-frame U−B colour gradient that is significantly larger than that observed in field ellipticals at z≤ 1, implying a stellar population of mixed metallicity (1–3 Z⊙) that formed in a high-redshift rapid burst. We have compared these two LBDS radio galaxies with the Kormendy relations of ten 3CR radio galaxies at z≃ 0.8 and a sample of cluster ellipticals at z∼ 0.4. The LBDS galaxies follow the Kormendy relation for the more radio-luminous 3CR galaxies, assuming passive evolution of their stellar populations, although they are smaller than the 3CR galaxies whose mean effective radius is 12 kpc. Their sizes and radio luminosities are consistent with scaling relations applied to the 3CR galaxies, in which both radio power and effective radius scale with galaxy mass. Compared with the sample of cluster ellipticals, 53W069 and 53W091 lie well within the scatter of the Kormendy relation. We conclude that the hosts of these millijansky radio sources at z≃ 1.5 are passively evolving elliptical galaxies that will evolve into ordinary L* ellipticals by the present day.
    Preview · Article · Aug 2002 · Monthly Notices of the Royal Astronomical Society
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    ABSTRACT: We have obtained deep long-slit spectroscopy at moderate resolution (R&ap; 1500) with Keck/LRIS of the high redshift QSO PC0953+4749 (z&ap; 4.5), and have discovered extended Lyman-alpha emission around the QSO. The line emission extends 5arcsec beyond the continuum of the QSO and is spatially asymmetric. This extended line emission has a spectral extent of 1000km/s, much narrower in velocity spread than the broad Lyman-alpha from the QSO itself and slightly offset in redshift. No evidence of continuum is seen for the extended emission line region, suggesting that this recombination line is powered by reprocessed QSO Lyman continuum flux rather than by local star formation. This phenomenon is rare in QSOs which are not radio loud, and this is the first time it has been observed at z>4. The QSO is illuminating the surrounding cold gas of the host galaxy, with the ionizing photons producing Lyman-alpha fluorescence. As suggested by Haiman & Rees (2001 ApJ 556, 87), this ``fuzz" around a distant quasar places strong constraints on galaxy formation and the extended distribution of cold, infalling gas. The HI cloud of the host galaxy is 35kpc in extent (H0=70km/s/Mpc and Omega M=0.3). We have also detected a second, separate galaxy in Lyman-alpha emission 24arcsec away (160kpc projected) at z=4.489, within 200km/s of the redshift of the extended Ly-alpha emission surrounding the QSO.
    No preview · Article · Jun 2002
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    ABSTRACT: We present our discovery observations and analysis of RDCS1317+2911, z = 0.805, and RDCS1350+6007, z= 0.804, two clusters of galaxies identified through X-ray emission in the ROSAT Deep Cluster Survey (RDCS). We find a temperature of 3.7 +1.5 -0.9 keV and a bolometric luminosity of 8.2e43 +1.7e43 -1.6e43 erg/s for RDCS1317+2911, and a temperature of 4.9 +1.3 -0.9 keV and a bolometric luminosity of 4.1e44 +0.5e44 -0.4e44 erg/s for RDCS1350+6007. Our weak lensing analysis of RDCS1350+6007 confirms the general shape of the inner density profile but predicts twice the mass of the model based on the X-ray profile. We combine the X-ray luminosities and temperatures for RDCS clusters of galaxies with such measurements of other clusters at high redshift (z>0.7) and fit the luminosity-temperature relation. We find no statistically significant evolution in the slope or zero-point of this relation at a median of z=0.83. This result is in agreement with models of intracluster medium evolution with significant pre-heating or high initial entropy values. We discuss how low temperature, high redshift clusters of galaxies will allow us to improve on this result and announce the discovery of two such objects, CXOU J0910.1+5419 and CXOU J1316.9+2914. Comment: 33 pages, Latex 2e using the AASTEX v5 macros, with 13 figures. Figures number one and six are color jpegs. Abstract abridged. Error in Table 1 corrected
    Preview · Article · Mar 2002 · The Astronomical Journal
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    ABSTRACT: We report the serendipitous detection in high--resolution spectroscopy of an emission--line galaxy (hereafter ES1) with a strong, asymmetric Lyalpha emission line at z = 5.189. The spectroscopic observations of ES1 were obtained on 25 February 2001 with the Echelle Spectrograph and Imager on the Keck II telescope. The echellogram has a resolution of ~ 75 km/s; the position angle from the nearby target galaxy (D16 in the HDF North West Flanking Field) was set at 150o. As the spectrograph configuration only covered 20 square arcseconds, the detection of ES1 was highly providential; we estimate the likelihood of such discoveries to be less than one chance in 100. ES1 lies in the HDF North West Flanking Field, for which a single--orbit I814 HST Wide Field Planetary Camera image is available. The faint galaxy responsible for the Lyalpha emission line is quite compact: the full width at half maximum on its I814 flanking field image is only 0''.3. Hence, the emitting region and continuum of the galaxy are observable over only ~ 2 kpc. One very intriguing aspect of this unlikely discovery is the spectral extent of the red wing of the Lyalpha line. A 3--parameter Gaussian fit suggests an outflow velocity of over 400 km/s. This young galaxy may therefore present evidence for both a high star formation rate and a starburst--driven galactic wind.
    No preview · Article · May 2001
  • S. Malhotra · J. Rhoads · A. Dey · B. Jannuzi · D. Stern · H. Spinrad
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    ABSTRACT: We find many candidate z=4.5 Lyman-alpha emitting galaxies in our LALA (Large Area Lyman Alpha) survey. More than half of these sources have rest frame equivalent widths greater than 200 Angstroms, which is the largest equivalent width expected for a standard stellar initial mass function (IMF). Either these sources are type II quasars or galaxies with an IMF dominated by massive stars. From Chandra Deep Field X-ray source counts, we estimate that only 10-20% of the LALA sources can be type II quasars. This then indicates that some galaxies at high redshifts had top heavy IMFs.
    No preview · Article · May 2001

Publication Stats

4k Citations
683.18 Total Impact Points

Institutions

  • 1975-2010
    • University of California, Berkeley
      • Department of Astronomy
      Berkeley, California, United States
  • 2002
    • California Institute of Technology
      • Jet Propulsion Laboratory
      Pasadena, California, United States
  • 1995
    • Cardiff University
      Cardiff, Wales, United Kingdom
  • 1993
    • University of Virginia
      • Department of Astronomy
      Charlottesville, Virginia, United States
  • 1988
    • Durham University
      Durham, England, United Kingdom
  • 1979
    • Pasadena City College
      Pasadena, Texas, United States
    • University of Sydney
      Sydney, New South Wales, Australia
  • 1978
    • University of California, San Diego
      San Diego, California, United States
  • 1974-1978
    • University of California, Santa Cruz
      Santa Cruz, California, United States
  • 1977
    • University of Washington Seattle
      Seattle, Washington, United States