High spatial resolution observations of CUDSS14A: a SCUBA-selected ultraluminous galaxy at high redshift

We present a high-resolution millimetre interferometric image of the brightest SCUBAselected galaxy from the Canada-UK deep SCUBA survey (CUDSS). We make a very clear detection at 1.3 mm, but fail to resolve any structure in the source. The interferometric position is within 1.5 arcsec of the SCUBA 850 � m centroid, and also within 1.5 arcsec of a 44 � Jy radio source and a very faint, extremely red galaxy which we had previously identified as the submillimetre source. We also present new optical and infrared imaging, and infrared spectroscopy of this source. We model the overall spectral energy distribution and conclude that it lies within the redshift range 2< z < 4.5. The submm/FIR luminosity of CUDSS14A is very weakly dependent on redshift within the constrained range, and is roughly 4×10 12 L⊙ (for H0=75 and an assumed Arp220-like spectrum), which implies a star-formation rate �1000 M⊙ yr −1 . We derive an approximate gas mass of � 10 10 M⊙ which would imply the current starforming activity cannot be sustained for longer than about 10 million years. With the present data however we are unable to rule out a significant AGN contribution to the total luminosity.

[1]  I. Smail,et al.  A Deep Submillimeter Survey of Lensing Clusters: A New Window on Galaxy Formation and Evolution , 1997, astro-ph/9708135.

[2]  Cambridge,et al.  Molecular Gas in the Z = 2.8 Submillimeter Galaxy SMM 02399-0136 , 1998 .

[3]  David Crampton,et al.  The Canada-United Kingdom Deep Submillimeter Survey. II. First Identifications, Redshifts, and Implications for Galaxy Evolution* , 1999 .

[4]  C. Bennett,et al.  The Spectrum of the Extragalactic Far-Infrared Background from the COBE FIRAS Observations , 1998, astro-ph/9803021.

[5]  E. Richards,et al.  Radio Identification of Submillimeter Sources in the Hubble Deep Field , 1998, astro-ph/9811098.

[6]  R. J. Ivison,et al.  Radio Constraints on the Identifications and Redshifts of Submillimeter Galaxies , 1999, astro-ph/9907083.

[7]  U. Lisenfeld,et al.  Dust and gas in luminous infrared galaxies – results from SCUBA observations , 1999, astro-ph/9907035.

[8]  R. J. Ivison,et al.  The discovery of ERO counterparts to faint submillimetre galaxies , 1999 .

[9]  L. Cowie,et al.  Submillimetre-wavelength detection of dusty star-forming galaxies at high redshift , 1998, Nature.

[10]  J. Dunlop,et al.  High-redshift star formation in the Hubble Deep Field revealed by a submillimetre-wavelength survey , 1998, Nature.

[11]  C. L. Carilli,et al.  The Radio-to-Submillimeter Spectral Index as a Redshift Indicator , 1998, astro-ph/9812251.

[12]  Simon J. E. Radford,et al.  Molecular gas mass and far-infrared emission from distant luminous galaxies , 1993 .

[13]  P. Clegg,et al.  A discussion on infared astronomy - Millimetre and submillimetre astronomy , 1969, Philosophical Transactions of the Royal Society of London. Series A, Mathematical and Physical Sciences.

[14]  Steve Rawlings,et al.  High-redshift radio galaxies and quasars at submillimetre wavelengths: assessing their evolutionary status , 1997, astro-ph/9705094.

[15]  D. Clements,et al.  The SCUBA Local Universe Galaxy Survey — I. First measurements of the submillimetre luminosity and dust mass functions , 2000, astro-ph/0002234.

[16]  I. Smail,et al.  Observations of a z = 1.44 Dusty, Ultraluminous Galaxy and Implications for Deep Submillimeter Surveys* ** *** , 1999 .

[17]  W. B. Burton,et al.  Millimetre and submillimetre astronomy , 1988 .

[18]  O. Fèvre,et al.  15 Micron Infrared Space Observatory Observations of the 1415+52 Canada-France Redshift Survey Field: The Cosmic Star Formation Rate as Derived from Deep Ultraviolet, Optical, Mid-Infrared, and Radio Photometry , 1999 .

[19]  S. Rawlings,et al.  Infrared spectroscopy of 11 radio galaxies at Z equals 2-4 - Evidence that some high-redshift radio galaxies may be protogalaxies , 1993 .

[20]  Andrew W. Blain.  Dust temperature and the submillimetre—radio flux density ratio as a redshift indicator for distant galaxies , 1999 .

[21]  C. L. Carilli,et al.  The Scatter in the Relationship between Redshift and the Radio-to-Submillimeter Spectral Index , 1999, astro-ph/9910316.

[22]  R. F. Mushotzky,et al.  Resolving the extragalactic hard X-ray background , 2000, Nature.

[23]  I. Smail,et al.  Testing the connection between the X-ray and submillimetre source populations using Chandra , 2000 .

[24]  I. Smail,et al.  Molecular Gas in the z = 2.565 Submillimeter Galaxy SMM J14011+0252 , 1999 .

[25]  E. A. Richards,et al.  Mapping the Evolution of High-Redshift Dusty Galaxies with Submillimeter Observations of a Radio-selected Sample , 2000, astro-ph/0001096.

[26]  R. Windhorst,et al.  The micro-jansky radio source population at 5 GHz , 1991 .

[27]  O. Fèvre,et al.  The Canada-UK Deep Submillimeter Survey: First Submillimeter Images, the Source Counts, and Resolution of the Background , 1998, astro-ph/9808040.

[28]  Jean-Paul Kneib,et al.  The diversity of SCUBA-selected galaxies , 2000 .