Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published January 20, 2010 | Published
Journal Article Open

Physical Properties and Morphology of a Newly Identified Compact z = 4.04 Lensed Submillimeter Galaxy in Abell 2218

Abstract

We present the identification of a bright submillimeter (submm) source, SMM J163555.5+661300, detected in the lensing cluster Abell 2218, for which we have accurately determined the position using observations from the Submillimeter Array (SMA). The identified optical counterpart has a spectroscopic redshift of z = 4.044 ± 0.001 if we attribute the single emission line detected at λ = 6140 Å to Lyα. This redshift identification is in good agreement with the optical/near-infrared photometric redshift as well as the submm flux ratio S_(450)/S_(850)~ 1.6, the radio-submm flux ratio S_(1.4)/S_(850) < 0.004, and the 24 μm to 850 μm flux ratio S_(24)/S_(850) < 0.005. Correcting for the gravitational lensing amplification of ~5.5, we find that the source has a far-infrared luminosity of 1.3 × 10^(12) L_☉, which implies a star formation rate (SFR) of 230 M_☉ yr^(–1). This makes it the lowest-luminosity submillimeter galaxy (SMG) known at z>4 to date. Previous CO(4-3) emission line observations yielded a non-detection, for which we derived an upper limit of the CO line luminosity of L'_(CO) = 0.3 × 10^(10) K km s^(–1) pc^(–2), which is not inconsistent with the L'_(CO)-L_(FIR) relation for starburst galaxies. The best-fit model to the optical and near-infrared photometry give a stellar population with an age of 1.4 Gyr and a stellar mass of 1.6 × 10^(10) M_☉. The optical morphology is compact and in the source plane the galaxy has an extent of ~6 × 3 kpc with individual star-forming knots of <500 pc in size. J163556 is not resolved in the SMA data, and we place a strict upper limit on the size of the starburst region of 8 kpc × 3 kpc, which implies a lower limit on the SFR surface density of 12 M_☉ yr^(–1) kpc^2. The redshift of J163556 extends the redshift distribution of faint, lensed SMGs, and we find no evidence that these have a different redshift distribution than bright SMGs.

Additional Information

© 2010 American Astronomical Society. Print publication: Issue 1 (2010 January 20); received 2009 January 7; accepted for publication 2009 November 9; published 2009 December 30. We thank an anonymous referee for insightful comments, which help improve the manuscript. The authors recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This program is based on observations made with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555, the Subaru Telescope, which is operated by the National Astronomical Observatory of Japan, the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. The Submillimeter Array is a joint project between the Smithsonian Astrophysical Observatory and the Academia Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academia Sinica. We thank Federica Govoni and Marie Machacek for providing the Chandra X-ray upper limit. K.K. acknowledges support from the Deutsche Forschungsgemeinschaft (DFG) Priority Programme 1177. J.P.K. thanks CNRS for support. J.R. acknowledges support from a EU Marie-Curie fellowship. Facilities: SMA, Keck (LRIS), JCMT (SCUBA), HST (ACS, NICMOS), Spitzer (IRAC, MIPS), WSRT, VLA, Subaru (MOIRCS).

Attached Files

Published - Knudsen2010p6907Astrophys_J.pdf

Files

Knudsen2010p6907Astrophys_J.pdf
Files (1.1 MB)
Name Size Download all
md5:c734dd48401116990594a5ddf96c759c
1.1 MB Preview Download

Additional details

Created:
August 21, 2023
Modified:
October 19, 2023