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  • 1
    Language: English
    In: Science (New York, N.Y.), 24 March 2017, Vol.355(6331), pp.1285-1288
    Description: Gas surrounding high-redshift galaxies has been studied through observations of absorption line systems toward background quasars for decades. However, it has proven difficult to identify and characterize the galaxies associated with these absorbers due to the intrinsic faintness of the galaxies compared with the quasars at optical wavelengths. Using the Atacama Large Millimeter/Submillimeter Array, we report on detections of [C ii] 158-μm line and dust-continuum emission from two galaxies associated with two such absorbers at a redshift of ~ 4. Our results indicate that the hosts of these high-metallicity absorbers have physical properties similar to massive star-forming galaxies and are embedded in enriched neutral hydrogen gas reservoirs that extend well beyond the star-forming interstellar medium of these galaxies.
    Keywords: Star Formation ; Galaxies ; Absorption ; Hydrogen ; Emission ; Quasars ; Enrichment ; Arrays ; Miscellaneous Sciences (So) ; (An);
    ISSN: 00368075
    E-ISSN: 1095-9203
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  • 2
    Article
    Article
    Language: English
    In: Nature, July 22, 2010, Vol.466(7305), p.444(2)
    Keywords: Astrophysics -- Research ; Cosmological Physics -- Models ; Galaxies -- Natural History
    ISSN: 0028-0836
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  • 3
    Article
    Article
    Language: English
    In: Nature, 7/2010, Vol.466(7305), pp.444-445
    Description: An innovative approach to map the large-scale structure in the Universe sidesteps the conventional need to observe millions of galaxies individually, and holds promise for both astrophysical and cosmological studies. Comment: Invited Nature 'News and Views' Commentary on Chang et al. 2010, Nature, 466, 463; 6pages, 1 figure
    Keywords: Astrophysics - Cosmology And Nongalactic Astrophysics;
    ISSN: 0028-0836
    E-ISSN: 1476-4687
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  • 4
    Language: English
    In: Science, March 24, 2017, Vol.355(6331), p.1285(3)
    Description: Gas surrounding high-redshift galaxies has been studied through observations of absorption line systems toward background quasars for decades. However, it has proven difficult to identify and characterize the galaxies associated with these absorbers due to the intrinsic faintness of the galaxies compared with the quasars at optical wavelengths. Using the Atacama Large Millimeter/Submillimeter Array, we report on detections of [C II] 158-[micro]m line and dust-continuum emission from two galaxies associated with two such absorbers at a redshift of z ~ 4. Our results indicate that the hosts of these high-metallicity absorbers have physical properties similar to massive star-forming galaxies and are embedded in enriched neutral hydrogen gas reservoirs that extend well beyond the star-forming interstellar medium of these galaxies.
    Keywords: Redshift – Research ; Galaxies – Research
    ISSN: 0036-8075
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  • 5
    Language: English
    In: Physical review letters, 22 June 2018, Vol.120(25), pp.251301
    Description: Detecting neutral hydrogen (H i) via the 21 cm line emission from the intergalactic medium at z≳6 has been identified as one of the most promising probes of the epoch of cosmic reionization-a major phase transition of the Universe. However, these studies face severe challenges imposed by the bright foreground emission from cosmic objects. Current techniques require precise instrumental calibration to separate the weak H i line signal from the foreground continuum emission. We propose to mitigate this calibration requirement by using measurements of the interferometric bispectrum phase. The bispectrum phase is unaffected by antenna-based direction-independent calibration errors and hence for a compact array it depends on the sky brightness distribution only (subject to the usual thermal-like noise). We show that the bispectrum phase of the foreground synchrotron continuum has a characteristically smooth spectrum relative to the cosmological line signal. The two can be separated effectively by exploiting this spectral difference using Fourier techniques, while eliminating the need for precise antenna-based calibration of phases introduced by the instrument, and the ionosphere, inherent in existing approaches. Using fiducial models for continuum foregrounds, and for the cosmological H i signal, we show the latter should be detectable in bispectrum phase spectra, with reasonable significance at |k_{∥}|≳0.5h  Mpc^{-1}, using existing instruments. Our approach will also benefit other H i intensity mapping experiments that face similar challenges, such as those measuring baryon acoustic oscillations (BAO).
    Keywords: Astrophysics - Cosmology And Nongalactic Astrophysics;
    ISSN: 00319007
    E-ISSN: 1079-7114
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  • 6
    In: Nature, 2010, Vol.464(7287), p.380
    Description: The most distant quasars known, at redshifts z [approximately equal to] 6, generally have properties indistinguishable from those of lower-redshift quasars in the rest-frame ultraviolet/optical and X-ray bands (1-3). This puzzling result suggests that these distant quasars are evolved objects even though the Universe was only seven per cent of its current age at these redshifts. Recently one z [approximately equal to] 6 quasar was shown not to have any detectable emission from hot dust (4), but it was unclear whether that indicated different hot-dust properties at high redshift or if it is simply an outlier. Here we report the discovery of a second quasar without hot-dust emission in a sample of 21 z [approximately equal to] 6 quasars. Such apparently hot-dust-free quasars have no counterparts at low redshift. Moreover, we demonstrate that the hot-dust abundance in the 21 quasars builds up in tandem with the growth of the central black hole, whereas at low redshift it is almost independent of the black hole mass. Thus z [approximately equal to] 6 quasars are indeed at an early evolutionary stage, with rapid mass accretion and dust formation. The two hot-dust-free quasars are likely to be first-generation quasars born in dust-free environments and are too young to have formed a detectable amount of hot dust around them.
    Keywords: Quasars -- Observations ; Redshift -- Observations;
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 7
    Article
    Article
    Apollo - University of Cambridge Repository
    Description: Detecting neutral Hydrogen (H\,{\sc i}) via the 21~cm line emission from the intergalactic medium at $z\gtrsim 6$ has been identified as one of the most promising probes of the epoch of cosmic reionization -- a major phase transition of the Universe. However, these studies face severe challenges imposed by the bright foreground emission from cosmic objects. Current techniques require precise instrumental calibration to separate the weak H\,{\sc i} line signal from the foreground continuum emission. We propose to mitigate this calibration requirement by using measurements of the interferometric bi-spectrum phase. Bi-spectrum phase is unaffected by antenna-based direction-independent calibration errors and hence for a compact array it depends on the sky brightness distribution only (subject to the usual thermal-like noise). We show that the bi-spectrum phase of foreground synchrotron continuum has a characteristically smooth spectrum relative to the cosmological line signal. The two can be separated effectively by exploiting this spectral difference using Fourier techniques, while eliminating the need for precise antenna-based calibration of phases introduced by the instrument, and the ionosphere, inherent in existing approaches. Using fiducial models for continuum foregrounds, and for the cosmological H\,{\sc i} signal, we show the latter should be detectable in bi-spectrum phase spectra, with...
    ISSN: 0031-9007
    Source: DataCite
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  • 8
    Article
    Article
    Language: English
    In: Nature, 22 July 2010, Vol.466(7305), pp.444-5
    Description: An innovative way of mapping the large-scale structure in the Universe sidesteps the need to observe millions of galaxies individually. The approach holds promise for both astrophysical and cosmological studies.
    Keywords: Sciences (General) ; Physics;
    E-ISSN: 1476-4687
    Source: MEDLINE/PubMed (U.S. National Library of Medicine)
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  • 9
    In: Nature, April 9, 1998, Vol.392(6676), p.575(3)
    Description: Radio observations of the supergiant star Betelgeuse indicate the temperature structure of the extended atmosphere from two to seven times the photospheric radius. The atmosphere close to the star has an irregular structure, while the temperature is consistent with the photospheric temperature but substantially lower than that of gas in the same region. It is concluded that the relatively cool gas responsible for the observed stellar radio emission spans the same height range as the hotter gas that creates the optical and ultraviolet chromospheric signatures.
    Keywords: Betelgeuse -- Research
    ISSN: 0028-0836
    E-ISSN: 14764687
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  • 10
    Article
    Article
    In: Nature, 2010, Vol.466(7305), p.444
    ISSN: 0028-0836
    Source: Nature Publishing Group
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