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dc.contributor.authorTakata, Tadafumien_US
dc.contributor.authorSekiguchi, Kazuhiroen_US
dc.contributor.authorSmail, Ianen_US
dc.contributor.authorChapman, Scott C.en_US
dc.contributor.authorGeach, J. E.en_US
dc.contributor.authorSwinbank, A. M.en_US
dc.contributor.authorBlain, Andrewen_US
dc.contributor.authorIvison, R. J.en_US
dc.date.accessioned2014-03-12T19:21:00Z
dc.date.available2014-03-12T19:21:00Z
dc.date.issued2006-11-10en_US
dc.identifier.citationTakata, Tadafumi, Kazuhiro Sekiguchi, Ian Smail, Scott C. Chapman, et al. 2006. "Restframe Optical Spectroscopic Classifications for Submillimeter Galaxies." The Astrophysical Journal 651(2): 713-727en_US
dc.identifier.issn0004-637Xen_US
dc.identifier.urihttp://dx.doi.org/10.1086/507985en_US
dc.identifier.urihttp://hdl.handle.net/10222/45448
dc.description.abstractWe 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.en_US
dc.titleRestframe Optical Spectroscopic Classifications for Submillimeter Galaxiesen_US
dc.title.alternativeThe Astrophysical Journalen_US
dc.typearticleen_US
dc.identifier.volume651en_US
dc.identifier.issue2en_US
dc.identifier.startpage713en_US
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