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

M. J. F. Rosenberg ; P. P. van der Werf ; Susanne Aalto (Institutionen för rymd- och geovetenskap, Radioastronomi och astrofysik) ; L. Armus ; V. Charmandaris ; T. Diaz-Santos ; A. S. Evans ; J. Fischer ; Y. Gao ; E. Gonzalez-Alfonso ; T. R. Greve ; A. I. Harris ; C. Henkel ; F. P. Israel ; K. G. Isaak ; C. Kramer ; R. Meijerink ; D. A. Naylor ; D. B. Sanders ; H. A. Smith ; M. Spaans ; L. Spinglio ; G. J. Stacey ; I. Veenendaal ; S. Veilleux ; F. Walter ; A. Weiss ; M. C. Wiedner ; M. H. D. van der Wiel ; E. M. Xilouris
Astrophysical Journal (0004-637X). Vol. 801 (2015), 2,
[Artikel, refereegranskad vetenskaplig]

(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.

Nyckelord: galaxies: individual (ULIRGs), galaxies: ISM, molecular data, photon-dominated region (PDR), submillimeter: ISM

Denna post skapades 2015-04-21. Senast ändrad 2015-11-13.
CPL Pubid: 215467


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