Gas and dust in a submillimeter galaxy at z = 4.24 from the Herschel ATLAS

TL;DR

This study presents detailed observations of a high-redshift, gravitationally lensed submillimeter galaxy, ID141, revealing its properties as a dense, warm starburst galaxy with intense star formation and PDR characteristics similar to local ULIRGs.

Contribution

First detailed multi-line analysis of a z=4.24 submillimeter galaxy, revealing its physical conditions and starburst nature with new observational data.

Findings

ID141 is at z=4.243 with strong CO emission lines.

ID141 is a gravitationally lensed, ultraluminous starburst galaxy.

The galaxy has dense, warm, and highly excited interstellar medium.

Abstract

We report ground-based follow-up observations of the exceptional source, ID141, one the brightest sources detected so far in the H-ATLAS cosmological survey. ID141 was observed using the IRAM 30-meter telescope and Plateau de Bure interferometer (PdBI), the Submillimeter Array (SMA) and the Atacama Pathfinder Experiment (APEX) submillimeter telescope to measure the dust continuum and emission lines of the main isotope of carbon monoxide and carbon ([C I] and [C II]). The detection of strong CO emission lines with the PdBI confirms that ID141 is at high redshift (z=4.243 +/- 0.001). The strength of the continuum and emission lines suggests that ID141 is gravitationally lensed. The width (Delta V (FWHM) ~ 800 km/s}) and asymmetric profiles of the CO and carbon lines indicate orbital motion in a disc or a merger. The properties derived for ID141 are compatible with a ultraluminous (L_FIR ~ 8.5 +/- 0.3 x 10^13/mu_L Lsun, where mu_L is the amplification factor, dense (n ~ 10^4 cm^-3) and warm (T_kin ~ 40K) starburst galaxy, with an estimated star-formation rate of (0.7 to 1.7) x 10^4/mu_L Msun/yr. The carbon emission lines indicate a dense (n ~ 10^4 cm^-3) Photo-Dominated Region, illuminated by a far-UV radiation field a few thousand times more intense than that in our Galaxy. In conclusion, the physical properties of the high-z galaxy, ID141, are remarkably similar to those of local ultraluminous infrared galaxies.