High Redshift Dust Obscured Galaxies, A Morphology-SED Connection Revealed by Keck Adaptive Optics

TL;DR

This study uses high-resolution Keck AO imaging to explore the morphology and SED connection in dust-obscured galaxies at z~2, revealing diverse structures and a correlation between concentration and mid-IR luminosity.

Contribution

It provides the first detailed morphological analysis of DOGs using AO imaging, linking their optical structures with IR luminosity and SED characteristics.

Findings

Most DOGs are small disks or ellipticals, with some unresolved.

Higher IR luminosity correlates with higher concentration and possible AGN activity.

Evidence of ongoing mergers in some DOGs.

Abstract

A simple optical to mid-IR color selection, R-[24] > 14, i.e. f_nu(24) / f_nu(R) > 1000, identifies highly dust obscured galaxies (DOGs) with typical redshifts of z~2 +/- 0.5. Extreme mid-IR luminosities (L_{IR} > 10^{12-14}) suggest that DOGs are powered by a combination of AGN and star formation, possibly driven by mergers. In an effort to compare their photometric properties with their rest frame optical morphologies, we obtained high spatial resolution (0.05 -0.1") Keck Adaptive Optics (AO) K'-band images of 15 DOGs. The images reveal a wide range of morphologies, including: small exponential disks (8 of 15), small ellipticals (4 of 15), and unresolved sources (2 of 15). One particularly diffuse source could not be classified because of low signal to noise ratio. We find a statistically significant correlation between galaxy concentration and mid-IR luminosity, with the most luminous DOGs exhibiting higher concentration and smaller physical size. DOGs with high concentration also tend to have spectral energy distributions (SEDs) suggestive of AGN activity. Thus central AGN light may be biasing the morphologies of the more luminous DOGs to higher concentration. Conversely, more diffuse DOGs tend to show an SED shape suggestive of star formation. Two of fifteen in the sample show multiple resolved components with separations of ~1 kpc, circumstantial evidence for ongoing mergers.