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Rest‐Frame OpticalSpectroscopicClassifications forSubmillimeterGalaxies Tadafumi TakataK. SekiguchiIan Smail2006 год

Rest‐Frame Optical Spectroscopic Classifications for Submillimeter Galaxies
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Аннотация: We report the results of a systematic near-infrared spectroscopic survey using the Subaru, VLT and Keck Telescopes of a sample of high redshift Ultra-luminous Infrared Galaxies (ULIRGs) mainly composed of submillimeter-selected galaxies. Our observations span the restframe optical range containing nebular emission lines such as H_beta, [OIII], and [OII], which are essential for making robust diagnostics of the physical properties of these ULIRGs. Using the H_alpha/H_beta emission line ratios, we derive internal extinction estimates for these galaxies similar to those of local ULIRGs:A_v~2.9+-0.5. Correcting the H_alpha estimates of the star formation rate for dust extinction using the Balmer decrement, results in rates which are consistent with those estimated from the far-infrared luminosity. The majority (>60%) of our sample show spectral features characteristic of AGN, with ~65% exhibiting broad Balmer emission lines. A proportion of these sources show relatively low [OIII]/H_beta line ratios, which are similar to those of Narrow Line Seyfert 1 galaxies suggesting small mass black holes which are rapidly growing. In the subsample of our survey with both [OIII] and hard X-ray coverage, at least ~60% show an excess of [OIII] emission, by a factor of 5-10 times, relative to the hard X-ray luminosity compared to the correlation between these two properties seen in Seyferts and QSOs locally. From our spectral diagnostics, we propose that the strong [OIII] emission in these galaxies arises from shocks in dense gaseous regions in this vigorously star-forming population.
Год издания: 2006
Авторы: Tadafumi Takata, K. Sekiguchi, Ian Smail, S. C. Chapman, J. E. Geach, A. M. Swinbank, A. W. Blain, R. J. Ivison
Издательство: IOP Publishing
Источник: The Astrophysical Journal
Ключевые слова: Galaxies: Formation, Evolution, Phenomena, Astrophysical Phenomena and Observations, Gamma-ray bursts and supernovae
Другие ссылки: The Astrophysical Journal (PDF)
The Astrophysical Journal (HTML)
CaltechAUTHORS (California Institute of Technology) (PDF)
CaltechAUTHORS (California Institute of Technology) (HTML)
arXiv (Cornell University) (PDF)
arXiv (Cornell University) (HTML)
DataCite API (HTML)