2020/10/20 by Luke Finnerty, Kirsten Larson, B. T. Soifer +10 · 1 citation
Physics and Astronomy · #astro-ph.GA
paper · pdf · doi:10.3847/1538-4357/abc3bf
26 pages, 5 figures, accepted to ApJ
arxiv created 2020/10/20 · arxiv updated 2020/12/09
We present rest-frame optical spectroscopic observations of 24 Hot Dust-Obscured Galaxies (Hot DOGs) at redshifts 1.7-4.6 with KECK/NIRES. Our targets are selected based on their extreme red colors to be the highest luminosity sources from the WISE infrared survey. In 20 sources with well-detected emission we fit the key [O III], Hβ, Hα, [N II], and [S II] diagnostic lines to constrain physical conditions. Of the 17 targets with a clear detection of the [O III]\rm λ5007A emission line, 15 display broad blueshifted and asymmetric line profiles, with widths ranging from 1000 to 8000 \rm km s-1 and blueshifts up to 3000 \rm km s-1. These kinematics provide strong evidence for the presence of massive ionized outflows of up to 8000 \rm M_\odot yr-1, with a median of 150 \rm M_\odot yr-1. As many as eight sources show optical emission line ratios consistent with vigorous star formation. Balmer line star-formation rates, uncorrected for reddening, range from 30--1300 \rm M_\odot yr-1, with a median of 50 \rm M_\odot yr-1. Estimates of the SFR from SED fitting of mid and far-infrared photometry suggest significantly higher values. We estimate the central black hole masses to be of order 108-10\rm M_\odot, assuming the present-day \rm MBH-σ_* relation. The bolometric luminosities and the estimated masses of the central black holes of these galaxies suggest that many of the AGN-dominated Hot DOGs are accreting at or above their Eddington limit. The combination of ongoing star formation, massive outflows, and high Eddington ratios suggest Hot DOGs are a transitional phase in galaxy evolution.