Natale, G. and Tuffs, R. J. and Xu, C. K. and Popescu, C. C. and Fischera, J. and Lisenfeld, U. and Lu, N. and Appleton, P. and Dopita, M. and Duc, P.-A. and Gao, Y. and Reach, W. and Sulentic, J. and Yun, M. (2010) Dust Emission and Star Formation in Stephan's Quintet. Astrophysical Journal, 725 (1). pp. 955-984. ISSN 0004-637X http://resolver.caltech.edu/CaltechAUTHORS:20101223-095608763
- Published Version
See Usage Policy.
Use this Persistent URL to link to this item: http://resolver.caltech.edu/CaltechAUTHORS:20101223-095608763
We analyze a comprehensive set of MIR/FIR observations of Stephan's Quintet (SQ), taken with the Spitzer Space Telescope. Our study reveals the presence of a luminous (L_(IR) ≈ 4.6 × 10^(43) erg s^(-1)) and extended component of infrared dust emission, not connected with the main bodies of the galaxies, but roughly coincident with the X-ray halo of the group. We fitted the inferred dust emission spectral energy distribution of this extended source and the other main infrared emission components of SQ, including the intergalactic shock, to elucidate the mechanisms powering the dust and polycyclic aromatic hydrocarbon emission, taking into account collisional heating by the plasma and heating through UV and optical photons. Combining the inferred direct and dust-processed UV emission to estimate the star formation rate (SFR) for each source we obtain a total SFR for SQ of 7.5 M_☉ yr^(-1), similar to that expected for non-interacting galaxies with stellar mass comparable to the SQ galaxies. Although star formation in SQ is mainly occurring at, or external to the periphery of the galaxies, the relation of SFR per unit physical area to gas column density for the brightest sources is similar to that seen for star formation regions in galactic disks. We also show that available sources of dust in the group halo can provide enough dust to produce up to L_(IR) ≈ 10^(42) erg s^(-1) powered by collisional heating. Though a minority of the total infrared emission (which we infer to trace distributed star-formation), this is several times higher than the X-ray luminosity of the halo, so could indicate an important cooling mechanism for the hot intergalactic medium (IGM) and account for the overall correspondence between FIR and X-ray emission. We investigate two potential modes of star formation in SQ consistent with the data, fueled either by gas from a virialized hot IGM continuously accreting onto the group, whose cooling is enhanced by grains injected from an in situ population of intermediate mass stars, or by interstellar gas stripped from the galaxies. The former mode offers a natural explanation for the observed baryon deficiency in the IGM of SQ as well as for the steep L_(X)-T_(X) relation of groups such as SQ with lower velocity dispersions.
|Additional Information:||© 2010 American Astronomical Society. Received 2010 June 11; accepted 2010 October 6; published 2010 November 22. We thank Pierre Guillard for fruitful discussions on the shock region of SQ, and Francois Boulanger and FabianWalter for discussions and comments on the manuscript. G.N. acknowledges support from the International Max–Planck Research School (IMPRS) Heidelberg. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.|
|Subject Keywords:||dust, extinction; galaxies: groups: individual (HGC92); galaxies: interactions; galaxies: star formation; infrared: general; intergalactic medium|
|Classification Code:||PACS: 98.65.Bv; 98.62.Ra; 98.70.Qy; 98.58.Ca; 95.85.Hp; 98.62.Ai|
|Official Citation:||G. Natale et al 2010 ApJ 725 955 doi: 10.1088/0004-637X/725/1/955|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Jason Perez|
|Deposited On:||23 Dec 2010 19:36|
|Last Modified:||26 Dec 2012 12:47|
Repository Staff Only: item control page