Herschel observations of FIR emission lines in brightest cluster galaxies
Alastair C. Edge
(1)
,
J. B. Raymond Oonk
(2)
,
Rupal Mittal
(3)
,
S. W. Allen
(4)
,
Stefi A. Baum
(3)
,
Hans Böhringer
(5)
,
J. N. Bregman
(6)
,
Malcolm N. Bremer
(7)
,
Françoise Combes
(8, 9)
,
C. S. Crawford
(10)
,
Megan Donahue
(11)
,
E. Egami
(12)
,
Andy C. Fabian
(10)
,
Gary J. Ferland
(13)
,
Stephen Hamer
(1)
,
Nina A. Hatch
(14)
,
Walter J. Jaffe
(2)
,
Roderick M. Johnstone
(10)
,
Brian R. Mcnamara
(15)
,
C. P. O'Dea
(16)
,
Paola Popesso
(5)
,
Alice C. Quillen
(17)
,
Philippe Salomé
(8, 9)
,
Craig L. Sarazin
(18)
,
G. M. Voit
(11)
,
R. J. Wilman
(19)
,
Michael W. Wise
(20)
1
ICC -
Institute for Computational Cosmology, Department of Physics, Durham University, Durham
2 Leiden Observatory [Leiden]
3 Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology
4 Stanford University
5 MPE - Max-Planck-Institut für Extraterrestriche Physik
6 Astronomy Department, University of Michigan
7 H. H. Wills Physics Laboratory [Bristol]
8 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
9 Galaxies et cosmologie
10 IoA - Institute of Astronomy, University of Cambridge
11 Physics and Astronomy Department, Michigan State University
12 Steward Observatory
13 Department of Physics, University of Kentucky
14 UON - University of Nottingham, UK
15 University of Waterloo [Waterloo]
16 Department of Physics, Rochester Institute of Technology
17 Department of Physics and Astronomy, University of Rochester
18 Astronomy Department, University of Virginia, Charlottesville
19 School of Physics, University of Melbourne
20 ASTRON - Netherlands Institute for Radio Astronomy
2 Leiden Observatory [Leiden]
3 Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology
4 Stanford University
5 MPE - Max-Planck-Institut für Extraterrestriche Physik
6 Astronomy Department, University of Michigan
7 H. H. Wills Physics Laboratory [Bristol]
8 LERMA - Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique
9 Galaxies et cosmologie
10 IoA - Institute of Astronomy, University of Cambridge
11 Physics and Astronomy Department, Michigan State University
12 Steward Observatory
13 Department of Physics, University of Kentucky
14 UON - University of Nottingham, UK
15 University of Waterloo [Waterloo]
16 Department of Physics, Rochester Institute of Technology
17 Department of Physics and Astronomy, University of Rochester
18 Astronomy Department, University of Virginia, Charlottesville
19 School of Physics, University of Melbourne
20 ASTRON - Netherlands Institute for Radio Astronomy
Résumé
The question of how much gas cools in the cores of clusters of galaxies has been the focus of many, multiwavelength studies in the past 30 years. In this letter we present the first detections of the strongest atomic cooling lines, [Cii], [Oi] and [Nii] in two strong cooling flow clusters, A1068 and A2597, using Herschel-PACS. These spectra indicate that the substantial mass of cold molecular gas (> 109 M_&sun;) known to be present in these systems is being irradiated by intense UV radiation, most probably from young stars. The line widths of these FIR lines indicate that they share dynamics similar but not identical to other ionised and molecular gas traced by optical, near-infrared and CO lines. The relative brightness of the FIR lines compared to CO and FIR luminosity is consistent with other star-forming galaxies indicating that the properties of the molecular gas clouds in cluster cores and the stars they form are not unusual. These results provide additional evidence for a reservoir of cold gas that is fed by the cooling of gas in the cores of the most compact clusters and provide important diagnostics of the temperature and density of the dense clouds this gas resides in.