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OSIRIS View of Submillimeter Galaxies: A 2–D Spectroscopic Insight to Starburst Galaxies in the High-Redshift Universe

Published online by Cambridge University Press:  03 June 2010

K. Menéndez-Delmestre
Affiliation:
NSF Astronomy and Astrophysics Postdoctoral Fellow, Carnegie Observatories, 813 Santa Barbara St., Pasadena, CA 91101, USA Email: kmd@obs.carnegiescience.edu
A. W. Blain
Affiliation:
California Institute of Technology, MC 105-24, Pasadena, CA 91125, USA
M. Swinbank
Affiliation:
Institute for Computational Cosmology, Durham University, Durham DH1 3LE, UK
I. Smail
Affiliation:
Institute for Computational Cosmology, Durham University, Durham DH1 3LE, UK
S. C. Chapman
Affiliation:
Institute of Astronomy, Madingley Road, Cambridge, CB3 0HA, UK
R. J. Ivison
Affiliation:
UK Astronomy Technology Centre, Blackford Hill, Edinburgh EH9 3HJ, UK Institute for Astronomy, Blackford Hill, Edinburgh EH9 3HJ, UK
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Abstract

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Ultra-luminous infrared galaxies (LIR > 1012L) are locally rare, but appear to dominate the co-moving energy density at higher redshifts (z > 2). Many of these are optically faint, dust-obscured galaxies that have been identified by the detection of their thermal dust emission in the sub-mm. Multi-wavelength spectroscopic follow-up observations of these sub-mm galaxies (SMGs) have shown that they are massive (Mstellar ~ 1011M) objects undergoing intense star-formation (SFRs ~ 102–103M yr−1) with a mean redshift of z ~ 2, coinciding with the epoch of peak quasar activity. Furthermore, the presence of AGNs in ~ 28–50% of SMGs has been unveiled in the X-ray and near-IR. When both AGN and star-formation activity are present, long-slit spectroscopic techniques face difficulties in disentangling their independent contributions from integrated spectra. We have observed Hα emission from a sample of three SMGs in the redshift range z ~ 1.4–2.4 with the integral field spectrograph OSIRIS on Keck, in conjunction with Laser Guide Star Adaptive Optics. The spatially resolved, two-dimensional spectroscopic insight that these observations provide is the only viable probe of the spatial distribution and line-of-sight motion of ionized gas within these galaxies. We detect multiple galactic-scale sub-components, distinguishing the compact, broad Hα emission arising from an AGN from the more extended narrow-line emission of star-forming regions spreading over ~ 8–17 kpc. We explore the dynamics of gas in the inner galaxy halo to improve our understanding of the internal dynamics of this enigmatic galaxy population. We find no evidence of ordered orbital motion such as would be found in a gaseous disk, but rather large velocity offsets of a few hundred kilometers per second between distinct galactic-scale sub-components. Considering the disturbed morphology of SMGs, these sub-components are likely remnants of originally independent gas-rich galaxies that are in the process of merging, hence triggering the ultraluminous SMG phase.

Type
Contributed Papers
Copyright
Copyright © International Astronomical Union 2010

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