The Herschel Comprehensive (U)lirg Emission Survey (Hercules): Co Ladders, Fine Structure Lines, and Neutral Gas Cooling
Artikel i vetenskaplig tidskrift, 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.

photon-dominated region (PDR)

submillimeter: ISM

galaxies: individual (ULIRGs)

galaxies: ISM

molecular data


M. J. F. Rosenberg

Universiteit Leiden

P.P. van der Werf

Universiteit Leiden

Susanne Aalto

Chalmers, Rymd- och geovetenskap, Radioastronomi och astrofysik

L. Armus

Spitzer Science Center

V. Charmandaris

National Observatory of Athens

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

Panepistimio Kritis

T. Diaz-Santos

Spitzer Science Center

A. S. Evans

National Radio Astronomy Observatory

University of Virginia

J. Fischer

Naval Research Laboratory

Y. Gao

Chinese Academy of Sciences

E. Gonzalez-Alfonso

Universidad de Alcala

T. R. Greve

University College London (UCL)

A. I. Harris

University of Maryland

C. Henkel

Max Planck-institutet

King Abdulaziz University

F. P. Israel

Universiteit Leiden

K. Isaak


C. Kramer

Instituto de Radioastronomía Milimétrica

R. Meijerink

Universiteit Leiden

D. A. Naylor

University of Lethbridge

D. B. Sanders

University of Hawaii

H. A. Smith

Harvard-Smithsonian Center for Astrophysics

M. Spaans

Rijksuniversiteit 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-institutet

A. Weiss

Max Planck-institutet

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


Astronomi, astrofysik och kosmologi



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