Continuum Observations at 350 Microns of High-Redshift Molecular Emission Line Galaxies

TL;DR

This study observes high-redshift galaxies at 350 microns, analyzing their dust and star formation properties, and tests a model of star formation occurring in numerous dense clumps similar to those in the Milky Way.

Contribution

It provides new observational data at 350 microns for high-redshift galaxies and supports a model of star formation in many dense, opaque clumps, linking galaxy luminosity to clump properties.

Findings

Detected emission in 8 out of 15 galaxies

Galaxy luminosities can be modeled with 0.9-30 million dense clumps

Gas mass estimates from dust and CO are in good agreement

Abstract

We report observations of 15 high redshift (z = 1-5) galaxies at 350 microns using the Caltech Submillimeter Observatory and SHARC-II array detector. Emission was detected from eight galaxies, for which far-infrared luminosities, star formation rates, total dust masses, and minimum source size estimates are derived. These galaxies have star formation rates and star formation efficiencies comparable to other high redshift molecular emission line galaxies. The results are used to test the idea that star formation in these galaxies occurs in a large number of basic units, the units being similar to star-forming clumps in the Milky Way. The luminosity of these extreme galaxies can be reproduced in a simple model with (0.9-30) *10^6 dense clumps, each with a luminosity of 5 *10^5 Lsun, the mean value for such clumps in the Milky Way. Radiative transfer models of such clumps can provide reasonable matches to the overall SEDs of the galaxies. They indicate that the individual clumps are quite opaque in the far-infrared. Luminosity to mass ratios vary over two orders of magnitude, correlating strongly with the dust temperature derived from simple fits to the SED. The gas masses derived from the dust modeling are in remarkable agreement with those from CO luminosities, suggesting that the assumptions going into both calculations are reasonable.