Black Hole Masses and Star Formation Rates of z >1 Dust Obscured Galaxies (DOGs): Results from Keck OSIRIS Integral Field Spectroscopy

TL;DR

This study uses high-resolution integral field spectroscopy to analyze four dust-obscured galaxies at z~1.5, revealing insights into their black hole masses, star formation rates, and nuclear activity with implications for galaxy evolution.

Contribution

First high-resolution spatially resolved spectroscopy of z>1 Dust Obscured Galaxies, distinguishing nuclear activity from star formation regions.

Findings

Black hole masses estimated between 1-9 x 10^8 solar masses.

Star formation rates are less than 100 solar masses per year.

No evidence of extended rotating gas disks in the sample galaxies.

Abstract

We have obtained high spatial resolution Keck OSIRIS integral field spectroscopy of four z~1.5 ultra-luminous infrared galaxies that exhibit broad H-alpha emission lines indicative of strong AGN activity. The observations were made with the Keck laser guide star adaptive optics system giving a spatial resolution of 0.1", or <1 kpc at these redshifts. These high spatial resolution observations help to spatially separate the extended narrow-line regions --- possibly powered by star formation --- from the nuclear regions, which may be powered by both star formation and AGN activity. There is no evidence for extended, rotating gas disks in these four galaxies. Assuming dust correction factors as high as A(H-alpha)=4.8 mag, the observations suggest lower limits on the black hole masses of (1 - 9) x 10^8 solar masses, and star formation rates <100 solar masses per year. The black hole masses and star formation rates of the sample galaxies appear low in comparison to other high-z galaxies with similar host luminosities. We explore possible explanations for these observations including, host galaxy fading, black hole growth, and the shut down of star formation.