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

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Main Authors: Harrington, Kevin C., Aranda, Román Fernández, Boogaard, Leindert, Weiß, Axel, Santos, Tanio Diaz, Aravena, Manuel, Assef, Roberto J., Tsai, Chao-Wei, Eisenhardt, Peter, Stern, Daniel
Format: Preprint
Published: 2025
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author Harrington, Kevin C.
Aranda, Román Fernández
Boogaard, Leindert
Weiß, Axel
Santos, Tanio Diaz
Aravena, Manuel
Assef, Roberto J.
Tsai, Chao-Wei
Eisenhardt, Peter
Stern, Daniel
author_facet Harrington, Kevin C.
Aranda, Román Fernández
Boogaard, Leindert
Weiß, Axel
Santos, Tanio Diaz
Aravena, Manuel
Assef, Roberto J.
Tsai, Chao-Wei
Eisenhardt, Peter
Stern, Daniel
contents 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 $\sim 8\times10^{10}$\,\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.
format Preprint
id arxiv_https___arxiv_org_abs_2504_17639
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Hot Diggity Dog: Simultaneous CO and Dust Modeling of the Most Luminous WISE Hot Dust-Obscured Galaxy Unveils Extreme Molecular Gas Excitation
Harrington, Kevin C.
Aranda, Román Fernández
Boogaard, Leindert
Weiß, Axel
Santos, Tanio Diaz
Aravena, Manuel
Assef, Roberto J.
Tsai, Chao-Wei
Eisenhardt, Peter
Stern, Daniel
Astrophysics of Galaxies
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 $\sim 8\times10^{10}$\,\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.
title Hot Diggity Dog: Simultaneous CO and Dust Modeling of the Most Luminous WISE Hot Dust-Obscured Galaxy Unveils Extreme Molecular Gas Excitation
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2504.17639