The Herschel Comprehensive (U)lirg Emission Survey (Hercules): Co Ladders, Fine Structure Lines, and Neutral Gas Cooling
Journal article, 2015

(Ultra) luminous infrared galaxies ((U)LIRGs) are objects characterized by their extreme infrared (8-1000 mu m) luminosities (L-LIRG > 10(11) L-circle dot and L-ULIRG > 10(12) L-circle dot). The Herschel Comprehensive ULIRG Emission Survey (PI: van derWerf) presents a representative flux-limited sample of 29 (U)LIRGs that spans the full luminosity range of these objects (10(11)L(circle dot) <= L-IR <= 10(13)L(circle dot)). With the Herschel Space Observatory, we observe [CII] 157 mu m, [O I] 63 mu m, and [O I] 145 mu m line emission with Photodetector Array Camera and Spectrometer, CO J = 4-3 through J = 13-12, [C I] 370 mu m, and [C I] 609 mu m with SPIRE, and low-J CO transitions with ground-based telescopes. The CO ladders of the sample are separated into three classes based on their excitation level. In 13 of the galaxies, the [O I] 63 mu m emission line is self absorbed. Comparing the CO excitation to the InfraRed Astronomical Satellite 60/100 mu m ratio and to far infrared luminosity, we find that the CO excitation is more correlated to the far infrared colors. We present cooling budgets for the galaxies and find fine-structure line flux deficits in the [C II], [Si II], [O I], and [C I] lines in the objects with the highest far IR fluxes, but do not observe this for CO 4 <= J(upp) <= 13. In order to study the heating of the molecular gas, we present a combination of three diagnostic quantities to help determine the dominant heating source. Using the CO excitation, the CO J = 1-0 linewidth, and the active galactic nucleus (AGN) contribution, we conclude that galaxies with large CO linewidths always have high-excitation CO ladders, and often low AGN contributions, suggesting that mechanical heating is important.

galaxies: individual (ULIRGs)

photon-dominated region (PDR)

galaxies: ISM

molecular data

submillimeter: ISM


M. J. F. Rosenberg

Leiden University

P.P. van der Werf

Leiden University

Susanne Aalto

Chalmers, Earth and Space Sciences, Radio Astronomy and Astrophysics

L. Armus

Spitzer Science Center

V. Charmandaris

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

University of Crete

National Observatory of Athens

T. Diaz-Santos

Spitzer Science Center

A. S. Evans

University of Virginia

National Radio Astronomy Observatory

J. Fischer

Naval Research Laboratory

Y. Gao

Chinese Academy of Sciences

E. Gonzalez-Alfonso

University of Alcalá

T. R. Greve

University College London (UCL)

A. I. Harris

University of Maryland

C. Henkel

Max Planck Society

King Abdulaziz University

F. P. Israel

Leiden University

K. Isaak

European Space Research and Technology Centre (ESA ESTEC)

C. Kramer

Institut de Radioastronomie Millimétrique (IRAM)

R. Meijerink

Leiden University

D. A. Naylor

University of Lethbridge

D. B. Sanders

University of Hawaii

H. A. Smith

Harvard-Smithsonian Center for Astrophysics

M. Spaans

University of Groningen

L. Spinoglio

Istituto nazionale di astrofisica (INAF)

G. J. Stacey

Cornell University

I. Veenendaal

University of Lethbridge

S. Veilleux

University of Maryland

F. Walter

Max Planck Society

A. Weiss

Max Planck Society

M. C. Wiedner

LERMA - Laboratoire d'Etudes du Rayonnement et de la Matiere en Astrophysique et Atmospheres

M. H. D. van der Wiel

University of Lethbridge

E. M. Xilouris

National Observatory of Athens

Astrophysical Journal

0004-637X (ISSN) 1538-4357 (eISSN)

Vol. 801 2 72

Subject Categories

Astronomy, Astrophysics and Cosmology



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