Restframe Optical Spectroscopic Classifications for Submillimeter Galaxies

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dc.creatorTakata, Tadafumi
dc.creatorSekiguchi, Kazuhiro
dc.creatorSmail, Ian
dc.creatorChapman, Scott C.
dc.creatorGeach, J. E.
dc.creatorSwinbank, A. M.
dc.creatorBlain, Andrew
dc.creatorIvison, R. J.
dc.date2006-07-26
dc.date.accessioned2026-07-07T10:39:40Z
dc.date.available2026-07-07T10:39:40Z
dc.descriptionWe 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.
dc.description21 pages, accepted to ApJ
dc.identifierhttps://arxiv.org/abs/astro-ph/0607580
dc.identifierhttp://arxiv.org/abs/astro-ph/0607580
dc.identifierAstrophys.J.651:713-727,2006
dc.identifierdoi:10.1086/507985
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/181108
dc.subjectAstrophysics
dc.titleRestframe Optical Spectroscopic Classifications for Submillimeter Galaxies
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