Hot Diggity Dog: Simultaneous CO and Dust Modeling of the Most Luminous WISE Hot Dust-Obscured Galaxy Unveils Extreme Molecular Gas Excitation

Abstract

Hot dust-obscured galaxies (Hot DOGs), the most infrared (IR) luminous objects selected by the WISE all-sky mid-IR survey, have yielded a sample of intrinsically luminous quasars (QSOs) with obscured nuclear activity and hot dust temperatures. The molecular gas excitation properties have yet to be examined in detail under such extreme conditions. Here we study the most far-IR luminous \textit{WISE} Hot DOG W2246-0526, focusing on ALMA observations of the central host galaxy. Multi-J CO transition measurements at J=2-1, 5-4, 7-6, 12-11, and 17-16 provide the first self-consistent modeling constraints on the molecular gas and dust properties of any WISE Hot DOG to date, providing a benchmark for future studies of dust-obscured QSOs. We implement a state-of-the-art TUrbulent Non-Equilibrium Radiative transfer model (TUNER) that simultaneously models both the line and dust continuum measurements. The extreme CO spectral line energy distribution seems to turnover around the CO(12-11) transition, likely making this among the most highly excited galaxies ever reported. The model infers a molecular gas mass $\sim 8\times 10^{10}$\,\Msun, and we conclude that J$\ge$3 CO line luminosities trace the bulk of the molecular gas mass for this extreme system unlike low-excitation conditions calibrated locally. W2246-0526 is a rapidly evolving system, with a high mean value of the molecular gas kinetic temperature versus dust temperature $T_{\mathrm{k}}$ / $T_{\mathrm{d}}\sim 4.3$. This may be due to the shocks and outflows injecting kinetic energy within the central kpc of this host that have previously been reported. These signs of highly excited molecular gas in W2246-0526 motivates obtaining well-sampled CO ladders in larger samples to better understand the conditions within these short-lived episodes associated with the most obscured supermassive black hole activity.

Accepted by A&A. 7 pages, 4 Appendix pages, 6 figures

References in corpus (17)

• Infrared Emission from Interstellar Dust. IV. The Silicate-Graphite-PAH Model in the Post-Spitzer Era
• Highly-excited CO emission in APM08279+5255 at z=3.9
• The First Hyper-Luminous Infrared Galaxy Discovered by WISE
• The Most Luminous Galaxies Discovered by WISE
• Submillimeter Follow-up of WISE-Selected Hyperluminous Galaxies
• ISM properties of a Massive Dusty Star-Forming Galaxy discovered at z ~ 7
• The ALMA Spectroscopic Survey in the HUDF: CO Excitation and Atomic Carbon in Star-Forming Galaxies at $z=1-3$
• Turbulent Gas in Lensed Planck-selected Starbursts at redshifts 1-3.5
• First CO(17-16) emission line detected in a z > 6 quasar
• Molecular Line Observations in Two Dusty Star-Forming Galaxies at z = 6.9
• PASSAGES: The Large Millimeter Telescope and ALMA Observations of Extremely Luminous High Redshift Galaxies Identified by the Planck
• Cold Molecular Gas and Free-Free Emission from Hot, Dust-Obscured Galaxies at $z$~3
• An Overdensity of Lyman Break Galaxies Around the Hot Dust-Obscured Galaxy WISE J224607.56$-$052634.9
• Physical properties of hyperluminous, dust-obscured quasars at $z\sim 3$: multiwavelength Spectral Energy Distribution analysis and cold gas content revealed by ALMA
• Spatially resolved dust properties over 50 kpc in a hyperluminous galaxy merger at $z=4.6$
• Overdensity of Lyman-Break Galaxy Candidates Around Hot Dust-Obscured Galaxies
• CO spectra of the ISM in the Host Galaxies of the Most Luminous WISE-Selected AGNs

Cited by in corpus (1)

• Vz-GAL: Probing Cold Molecular Gas in Dusty Star-forming Galaxies at z=1-6