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  • 1
    Electronic Resource
    Electronic Resource
    Spectral constraints on the redshift of the optical counterpart to the γ-ray burst of 8 May 1997 (1997)
    [s.l.] : Macmillan Magazines Ltd.
    Nature 387 (1997), S. 878-880 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Brief, intense bursts of γ-rays occur approximately daily from random directions in space, but their origin has remained unknown since their initial detection almost 25 years ago. Arguments based on their observed isotropy and apparent brightness distribution are not sufficient to ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/387878a0
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    Paper (German National Licenses)
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  • 2
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    Observing the epoch of galaxy formation (1999)
    National Academy of Sciences
    Details
    Publication Date: 1999-04-13
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 3
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    Galaxies and large scale structure at high redshifts (1998)
    National Academy of Sciences
    Details
    Publication Date: 1998-01-06
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
    Published by National Academy of Sciences
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  • 4
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    A millimetre-wave redshift search for the unlensed HyLIRG, HS1700.850.1 (2015)
    Oxford University Press
    Details
    Publication Date: 2015-08-24
    Description: We report the redshift of an unlensed, highly obscured submillimetre galaxy (SMG), HS1700.850.1, the brightest SMG ( S 850 μm  = 19.1 mJy) detected in the James Clerk Maxwell Telescope/Submillimetre Common-user Bolometer Array-2 (JCMT/SCUBA-2) Baryonic Structure Survey, based on the detection of its 12 CO line emission. Using the Institute Radio Astronomie Millimetrique Plateau de Bure Interferometer with 3.6 GHz band width, we serendipitously detect an emission line at 150.6 GHz. From a search over 14.5 GHz in the 3- and 2-mm atmospheric windows, we confirm the identification of this line as 12 CO(5–4) at z  = 2.816, meaning that it does not reside in the z  ~ 2.30 proto-cluster in this field. Measurement of the 870 μm source size (〈0.85 arcsec) from the Sub-Millimetre Array (SMA) confirms a compact emission in a S 870 μm = 14.5 mJy, L IR  ~ 10 13  L component, suggesting an Eddington-limited starburst. We use the double-peaked 12 CO line profile measurements along with the SMA size constraints to study the gas dynamics of a HyLIRG, estimating the gas and dynamical masses of HS1700.850.1. While HS1700.850.1 is one of the most extreme galaxies known in the Universe, we find that it occupies a relative void in the Lyman-Break Galaxy distribution in this field. Comparison with other extreme objects at similar epochs (HyLIRG Quasars), and cosmological simulations, suggests such an anti-bias of bright SMGs could be relatively common, with the brightest SMGs rarely occupying the most overdense regions at z = 2–4.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 5
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    Detection of hot, metal-enriched outflowing gas around z {approx} 2.3 star-forming galaxies in the Keck Baryonic Structure Survey (2015)
    Oxford University Press
    Details
    Publication Date: 2015-05-02
    Description: We use quasar absorption lines to study the physical conditions in the circumgalactic medium of redshift z 2.3 star-forming galaxies taken from the Keck Baryonic Structure Survey. In Turner et al. we used the pixel optical depth technique to show that absorption by H i and the metal ions O vi , N v , C iv , C iii , and Si iv is strongly enhanced within | v | 170 km s –1 and projected distances | d | 180 proper kpc from sightlines to the background quasars. Here we demonstrate that the O vi absorption is also strongly enhanced at fixed H i , C iv , and Si iv optical depths, and that this enhancement extends out to ~350 km s –1 . At fixed H i the increase in the median O vi optical depth near galaxies is 0.3–0.7 dex and is detected at 2–3 confidence for all seven H i bins that have $\log _{10}\tau _{\rm H\, {\small I}} \ge -1.5$ . We use ionization models to show that the observed strength of O vi as a function of H i is consistent with enriched, photoionized gas for pixels with $\tau _{\rm H\, {\small I}} \gtrsim 10$ . However, for pixels with $\tau _{\rm H\, {\small I}} \lesssim 1$ this would lead to implausibly high metallicities at low densities if the gas were photoionized by the background radiation. This indicates that the galaxies are surrounded by gas that is sufficiently hot to be collisionally ionized ( T 〉 10 5 K) and that a substantial fraction of the hot gas has a metallicity 10 –1 of solar. Given the high metallicity and large velocity extent (out to ~1.5 v circ ) of this gas, we conclude that we have detected hot, metal-enriched outflows arising from star-forming galaxies.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 6
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    Herschel protocluster survey: a search for dusty star-forming galaxies in protoclusters at z = 2-3 (2016)
    Oxford University Press
    Details
    Publication Date: 2016-06-26
    Description: We present a Herschel /Spectral and Photometric Imaging Receiver (SPIRE) survey of three protoclusters at z = 2–3 (2QZCluster, HS1700, SSA22). Based on the SPIRE colours ( S 350 / S 250 and S 500 / S 350 ) of 250 μm sources, we selected high-redshift dusty star-forming galaxies potentially associated with the protoclusters. In the 2QZCluster field, we found a 4 overdensity of six SPIRE sources around 4.5 arcmin (~2.2 Mpc) from a density peak of H α emitters at z = 2.2. In the HS1700 field, we found a 5 overdensity of eight SPIRE sources around 2.1 arcmin (~1.0 Mpc) from a density peak of Lyman-break galaxies at z = 2.3. We did not find any significant overdensities in SSA22 field, but we found three 500 μm sources are concentrated 3 arcmin (~1.4 Mpc) east to the Ly α emitters overdensity. If all the SPIRE sources in these three overdensities are associated with protoclusters, the inferred star formation rate densities are 10 3 –10 4 times higher than the average value at the same redshifts. This suggests that dusty star formation activity could be very strongly enhanced in z ~ 2–3 protoclusters. Further observations are needed to confirm the redshifts of the SPIRE sources and to investigate what processes enhance the dusty star formation activity in z ~ 2–3 protoclusters.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 7
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    Correlation between star formation activity and electron density of ionized gas at z = 2.5 (2015)
    Oxford University Press
    Details
    Publication Date: 2015-06-07
    Description: In the redshift interval of 2 〈 z 〈 3, the physical conditions of the interstellar medium (ISM) in star-forming galaxies are likely to be different from those in the local Universe because of lower gaseous metallicities, higher gas fractions, and higher star formation activities. In fact, observations suggest that higher electron densities, higher ionization parameters, and harder UV radiation fields are common. In this paper, based on the spectra of H α-selected star-forming galaxies at z = 2.5 taken with Multi-Object Spectrometer for InfraRed Exploration on Keck-1 telescope, we measure electron densities ( n e ) using the oxygen line ratio ([O ii ] 3726,3729), and investigate the relationships between the electron density of ionized gas and other physical properties. As a result, we find that the specific star formation rate (sSFR) and the surface density of SFR ( SFR ) are correlated with the electron density at z = 2.5 for the first time. The SFR – n e relation is likely to be linked to the star formation law in H ii regions (where star formation activity is regulated by interstellar pressure). Moreover, we discuss the mode of star formation in those galaxies. The correlation between sSFR and SFR suggests that highly star-forming galaxies (with high sSFR) tend to be characterized by higher surface densities of star formation ( SFR ) and thus higher n e values as well.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 8
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    Correlation between star formation activity and electron density of ionized gas at z = 2.5 (2015)
    Oxford University Press
    Details
    Publication Date: 2015-06-12
    Description: In the redshift interval of 2 〈 z 〈 3, the physical conditions of the interstellar medium (ISM) in star-forming galaxies are likely to be different from those in the local Universe because of lower gaseous metallicities, higher gas fractions, and higher star formation activities. In fact, observations suggest that higher electron densities, higher ionization parameters, and harder UV radiation fields are common. In this paper, based on the spectra of H α-selected star-forming galaxies at z = 2.5 taken with Multi-Object Spectrometer for InfraRed Exploration on Keck-1 telescope, we measure electron densities ( n e ) using the oxygen line ratio ([O ii ] 3726,3729), and investigate the relationships between the electron density of ionized gas and other physical properties. As a result, we find that the specific star formation rate (sSFR) and the surface density of SFR ( SFR ) are correlated with the electron density at z = 2.5 for the first time. The SFR – n e relation is likely to be linked to the star formation law in H ii regions (where star formation activity is regulated by interstellar pressure). Moreover, we discuss the mode of star formation in those galaxies. The correlation between sSFR and SFR suggests that highly star-forming galaxies (with high sSFR) tend to be characterized by higher surface densities of star formation ( SFR ) and thus higher n e values as well.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 9
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    Metal-line absorption around z {approx} 2.4 star-forming galaxies in the Keck Baryonic Structure Survey (2014)
    Oxford University Press
    Details
    Publication Date: 2014-10-02
    Description: We study metal absorption around 854 z   2.4 star-forming galaxies taken from the Keck Baryonic Structure Survey. The galaxies examined in this work lie in the fields of 15 hyperluminous background quasi-stellar objects, with galaxy impact parameters ranging from 35 proper kpc (pkpc) to 2 proper Mpc (pMpc). Using the pixel optical depth technique, we present the first galaxy-centred 2D maps of the median absorption by O vi , N v , C iv , C iii , and Si iv , as well as updated results for H i . At small galactocentric radii we detect a strong enhancement of the absorption relative to randomly located regions that extend out to at least 180 pkpc in the transverse direction, and ±240 km s –1 along the line of sight (LOS, ~1 pMpc in the case of pure Hubble flow) for all ions except N v . For C iv (and H i ) we detect a significant enhancement of the absorption signal out to 2 pMpc in the transverse direction, corresponding to the maximum impact parameter in our sample. After normalizing the median absorption profiles to account for variations in line strengths and detection limits, in the transverse direction we find no evidence for a sharp drop-off in metals distinct from that of H i . We argue instead that non-detection of some metal-line species in the extended circumgalactic medium is consistent with differences in the detection sensitivity. Along the LOS, the normalized profiles reveal that the enhancement in the absorption is more extended for O vi , C iv , and Si iv than for H i . We also present measurements of the scatter in the pixel optical depths, covering fractions, and equivalent widths as a function of projected galaxy distance. Limiting the sample to the 340 galaxies with redshifts measured from nebular emission lines does not decrease the extent of the enhancement along the LOS compared to that in the transverse direction. This rules out redshift errors as the source of the observed redshift-space anisotropy and thus implies that we have detected the signature of gas peculiar velocities from infall, outflows, or virial motions for H i , O vi , C iv , C iii , and Si iv .
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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  • 10
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    Testing metallicity indicators at z ~ 1.4 with the gravitationally lensed galaxy CASSOWARY 20 (2014)
    Oxford University Press
    Details
    Publication Date: 2014-04-15
    Description: We present X-shooter observations of CASSOWARY 20 (CSWA 20), a star-forming (SFR ~ 6 M yr –1 ) galaxy at z  = 1.433, magnified by a factor of 11.5 by the gravitational lensing produced by a massive foreground galaxy at z  = 0.741. We analysed the integrated physical properties of the H ii regions of CSWA 20 using temperature- and density-sensitive emission lines. We find the abundance of oxygen to be ~1/7 of solar, while carbon is ~50 times less abundant than in the Sun. The unusually low C/O ratio may be an indication of a particularly rapid time-scale of chemical enrichment. The wide wavelength coverage of X-shooter gives us access to five different methods for determining the metallicity of CSWA 20, three based on emission lines from H ii regions and two on absorption features formed in the atmospheres of massive stars. All five estimates are in agreement, within the factor of ~2 uncertainty of each method. The interstellar medium (ISM) of CSWA 20 only partially covers the star-forming region as viewed from our direction; in particular, absorption lines from neutrals and first ions are exceptionally weak. We find evidence for large-scale outflows of the ISM with speeds of up 750 km s –1 , similar to the values measured in other high- z galaxies sustaining much higher rates of star formation.
    Print ISSN: 0035-8711
    Electronic ISSN: 1365-2966
    Topics: Physics
    Published by Oxford University Press
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