Observed at z = 4.601 and with L bol = 3.5 × 10 14 L ⊙ , W2246-0526 is the most luminous galaxy known in the Universe, and hosts a deeply-buried active galactic nucleus (AGN)/super-massive black hole (SMBH). Discovered using the Wide-field Infrared Survey Explorer (WISE), W2246-0526 is classified as a Hot Dust Obscured Galaxy (Hot DOG), based on its luminosity and dust temperature. Here we present spatially resolved ALMA [C ii]157.7 µm observations of W2246-0526, providing unique insight into the kinematics of its interstellar medium (ISM). The measured [C ii] -to-far-infrared ratio is ∼ 2 × 10 −4 , implying ISM conditions that compare only with the most obscured, compact starbursts and AGN in the local Universe today. The spatially resolved [C ii] line is strikingly uniform and very broad, 500-600 km s −1 wide, extending throughout the entire galaxy over about 2.5 kpc, with modest shear. Such a large, homogeneous velocity dispersion indicates a highly turbulent medium. W2246-0526 is unstable in terms of the energy and momentum that are being injected into the ISM, strongly suggesting that the gas is being blown away from the system isotropically, likely reflecting a cathartic state on its road to becoming an un-obscured quasar. W2246-0526 provides an extraordinary laboratory to study and model the properties and kinematics of gas in an extreme environment under strong feedback, at a time when the Universe was 1/10 of its current age: a system pushing the limits that can be reached during galaxy formation.

Hot dust-obscured galaxies (Hot DOGs) are among the most luminous galaxies in the universe. Powered by highly obscured, possibly Compton-thick, active galactic nuclei (AGNs), Hot DOGs are characterized by spectral energy distributions that are very red in the mid-infrared yet dominated by the host galaxy stellar emission in the UV and optical. An earlier study identified a subsample of Hot DOGs with significantly enhanced UV emission. One target, W0204-0506, was studied in detail and, based on Chandra observations, it was concluded that the enhanced emission was most likely due to either extreme unobscured star formation (star formation rate>1000 M e yr −1) or to light from the highly obscured AGN scattered by gas or dust into our line of sight. Here, we present a follow-up study of W0204-0506 as well as two more Hot DOGs with excess UV emission. For the two new objects we obtained Chandra/ACIS-S observations, and for all three targets we obtained Hubble Space Telescope/WFC3 F555W and F160W imaging. The analysis of these observations, combined with multiwavelength photometry and UV/optical spectroscopy suggests that UV emission is most likely dominated by light from the central highly obscured, hyperluminous AGN that has been scattered into our line of sight, by either gas or dust. We cannot decisively rule out, however, that star formation or a second AGN in the system may significantly contribute to the UV excess of these targets.

The cluster 037-B327 is of interest because it is both the most luminous and the most highly reddened cluster known in M31. Deep observations with the Advanced Camera for Surveys on the Hubble Space Telescope provide photometric data in the F606W band and also show that this cluster is crossed by a dust lane. We have determined the structural parameters of 037-B327 by fitting the observed surface brightness distribution to a King model with r c p 0Љ .72 (p2.69 pc), r t p 5Љ .87 (p21.93 pc), and a concentration index c p log (r t /r c ) p 0.91. The surface brightness profile appears to be essentially flat within 0Љ .25 of the center and shows no signs of core collapse. Although the dust lane affects the photometry, the King model fits the surface brightness profile well except for the regions badly affected by the dust lane. We also calculate the half-light radius, r h p 1Љ .11 (p4.15 pc). Combined with previous photometry, we find that this object falls in the same region of the M V versus log R h diagram as do q Centauri, M54, and NGC 2419 in the Milky Way and the massive cluster G1 in M31. All four of these objects have been claimed to be the stripped cores of former dwarf galaxies. This suggests that 037-B327 may also be the stripped core of a former dwarf companion to M31.