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
Author
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 72Subject Categories
Astronomy, Astrophysics and Cosmology
DOI
10.1088/0004-637x/801/2/72