Abstract

Based on broadband/narrowband photometry and Keck DEIMO spectroscopy, we report a redshift of z = 4.64(-0.08)(+0.06) for AzTEC/COSMOS 1, the brightest submillimeter galaxy (SMG) in the AzTEC/COSMOS field. In addition to the COSMOS-survey X-ray to radio data, we report observations of the source with Herschel/PACS (100, 160 mu m), CSO/SHARC II (350 mu m), and CARMA and PdBI (3 mm). We do not detect CO(5 -> 4) line emission in the covered redshift ranges, 4.56-4.76 (PdBI/CARMA) and 4.94-5.02 (CARMA). If the line is within this bandwidth, this sets 3 sigma upper limits on the gas mass to less than or similar to 8 x 10(9) M-circle dot and less than or similar to 5 x 10(10) M-circle dot, respectively (assuming similar conditions as observed in z similar to 2 SMGs). This could be explained by a low CO-excitation in the source. Our analysis of the UV-IR spectral energy distribution of AzTEC 1 shows that it is an extremely young (less than or similar to 50 Myr), massive (M-* similar to 10(11) M-circle dot), but compact (less than or similar to 2 kpc) galaxy, forming stars at a rate of similar to 1300 M-circle dot yr(-1). Our results imply that AzTEC 1 is forming stars in a "gravitationally bound" regime in which gravity prohibits the formation of a superwind, leading to matter accumulation within the galaxy and further generations of star formation.