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A Hubble Space Telescope NICMOS and ACS morphological study of z ~ 2 submillimetre galaxies

Swinbank, A. M. and Smail, Ian and Chapman, S. C. and Borys, C. and Alexander, D. M. and Blain, A. W. and Conselice, C. J. and Hainline, L. J. and Ivison, R. J. (2010) A Hubble Space Telescope NICMOS and ACS morphological study of z ~ 2 submillimetre galaxies. Monthly Notices of the Royal Astronomical Society, 405 (1). pp. 234-244. ISSN 0035-8711.

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We present a quantitative morphological analysis using Hubble Space Telescope Near Infrared Camera and Multi-Object SpectrometerH160-band imaging and Advanced Camera for Surveys I_(775)-band imaging of 25 spectroscopically confirmed submillimetre galaxies (SMGs) which have redshifts between z = 0.7 and 3.4 (z = 2.1). Our analysis also employs a comparison sample of more typical star-forming galaxies at similar redshifts (such as Lyman-break Galaxies) which have lower far-infrared luminosities. This is the first large-scale study of the morphologies of SMGs in the near-infrared at ~0.1 arcsec resolution (≾1 kpc). We find that the half-light radii of the SMGs (r_h = 2.3 ± 0.3 and 2.8 ± 0.4 kpc in the observed I and H bands, respectively) and asymmetries are not statistically distinct from the comparison sample of star-forming galaxies. However, we demonstrate that the SMG morphologies differ more between the rest-frame UV and optical bands than typical star-forming galaxies and interpret this as evidence for structured dust obscuration. We show that the composite observed H-band light profile of SMGs is better fitted with a high Sersic index (n ~ 2) than with an exponential disc suggesting the stellar structure of SMGs is best described by a spheroid/elliptical galaxy light distribution. We also compare the sizes and stellar masses of SMGs to local and highredshift populations and find that the SMGs have stellar densities which are comparable to (or slightly larger than) local early-type galaxies and comparable to luminous, red and dense galaxies at z ~ 1.5 which have been proposed as direct SMG descendants, although the SMG stellar masses and sizes are systematically larger. Overall, our results suggest that the physical processes occurring within the galaxies are too complex to be simply characterized by the rest-frame UV/optical morphologies which appear to be essentially decoupled from all other observables, such as bolometric luminosity, stellar or dynamical mass.

Item Type:Article
Related URLs:
URLURL TypeDescription
Smail, Ian0000-0003-3037-257X
Alexander, D. M.0000-0002-5896-6313
Blain, A. W.0000-0001-7489-5167
Conselice, C. J.0000-0003-1949-7638
Ivison, R. J.0000-0001-5118-1313
Additional Information:© 2010 The Authors. Journal compilation © 2010 RAS. Accepted 2010 February 4. Received 2010 February 4; in original form 2009 November 18. We are very grateful to the referee for their constructive comments which significantly improved the content and clarity of this paper. We would like to thank Alfred Schultz at STScI for advice on dealing with the effects of the SAA on our NICMOS data. We gratefully acknowledge Eric Richards for providing us with his reduced maps of HDF and SSA13 and David Law and Jim Dunlop for useful discussions. AMS gratefully acknowledges a Sir Norman Lockyer Royal Astronomical Society fellowship. SCC acknowledges support from NASA grants 9174 and 9856. IRS acknowledges support from STFC. AWB acknowledges NSF grant AST-0205937 and the Alfred P. Sloan Foundation. DMA thanks the Royal Society and Leverhume trust.
Funding AgencyGrant Number
Science and Technology Facilities Council (STFC)UNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Leverhume trustUNSPECIFIED
Subject Keywords:galaxies: evolution – galaxies: formation – galaxies: high-redshift – submillimetre.
Issue or Number:1
Record Number:CaltechAUTHORS:20100628-085611076
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:18825
Deposited By: Tony Diaz
Deposited On:05 Aug 2010 22:25
Last Modified:23 Nov 2019 00:37

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