PHYSICAL PROPERTIES AND MORPHOLOGY OF A NEWLY IDENTIFIED COMPACT z = 4.04 LENSED SUBMILLIMETER GALAXY IN ABELL 2218

Journal Article · Wed Jan 20 04:00:00 EST 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/709/1/210· OSTI ID:21392249

Knudsen, Kirsten K ^[1]; Kneib, Jean-Paul ^[2]; Richard, Johan ^[3]; Petitpas, Glen ^[4]; Egami, Eiichi ^[5]

---

1. Argelander Institut fuer Astronomie, Auf dem Huegel 71, D-53121 Bonn (Germany)
2. Laboratoire d'Astrophysique de Marseille, OAMP, Universite, Aix-Marseilles and CNRS, 38 rue Frederic Joliot Curie, 13388 Marseille cedex 13 (France)
3. California Institute of Technology, MS 105-24, Pasadena, CA 91125 (United States)
4. Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States)
5. Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tuscon, AZ 85721 (United States)

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 lambda = 6140 A to Lyalpha. This redshift identification is in good agreement with the optical/near-infrared photometric redshift as well as the submm flux ratio S{sub 450}/S{sub 850}approx 1.6, the radio-submm flux ratio S{sub 1.4}/S{sub 850} < 0.004, and the 24 mum to 850 mum flux ratio S{sub 24}/S{sub 850} < 0.005. Correcting for the gravitational lensing amplification of approx5.5, we find that the source has a far-infrared luminosity of 1.3 x 10{sup 12} L{sub sun}, which implies a star formation rate (SFR) of 230 M{sub sun} yr{sup -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{sub CO}{sup '}= 0.3x10{sup 10} K km s{sup -1} pc{sup -2}, which is not inconsistent with the L{sup '}{sub CO}-L{sub 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 x 10{sup 10} M{sub sun}. The optical morphology is compact and in the source plane the galaxy has an extent of approx6 x 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 x 3 kpc, which implies a lower limit on the SFR surface density of 12 M{sub sun} yr{sup -1} kpc{sup 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.

• OSTI ID: 21392249
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 1 Vol. 709; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CHALCOGENIDES
GALAXIES
LUMINOSITY
MORPHOLOGY
OPTICAL PROPERTIES
OXIDES
OXYGEN COMPOUNDS
PHOTOMETRY
PHYSICAL PROPERTIES
RED SHIFT
STARS