Universidad de Granada Digibug

Repositorio Institucional de la Universidad de Granada >
1.-Investigación >
Departamentos, Grupos de Investigación e Institutos >
Departamento de Física Teórica y del Cosmos >
DFTC - Artículos >

Please use this identifier to cite or link to this item: http://hdl.handle.net/10481/28359

Title: Turbulent molecular gas and star formation in the shocked intergalactic medium of Stephan's Quintet
Authors: Guillard, P.
Boulanger, F.
Pineau des Forêts, G.
Falgarone, E.
Gusdorf, A.
Cluver, M. E.
Appleton, P. N.
Lisenfeld, Ute
Duc, P.-A.
Ogle, P. M.
Xu, C. K.
Issue Date: 2012
Abstract: We report on single-dish radio CO observations towards the inter-galactic medium (IGM) of the Stephan's Quintet (SQ) group of galaxies. Extremely bright mid-IR H2 rotational line emission from warm molecular gas has been detected by Spitzer in the kpc-scale shock created by a galaxy collision. We detect in the IGM CO(1-0), (2-1) and (3-2) line emission with complex profiles, spanning a velocity range of 1000 km/s. The spectra exhibit the pre-shock recession velocities of the two colliding gas systems (5700 and 6700 km/s), but also intermediate velocities. This shows that much of the molecular gas has formed out of diffuse gas accelerated by the galaxy-tidal arm collision. A total H2 mass of 5x10^9 Msun is detected in the shock. The molecular gas carries a large fraction of the gas kinetic energy involved in the collision, meaning that this energy has not been thermalized yet. The turbulent kinetic energy of the H2 gas is at least a factor of 5 greater than the thermal energy of the hot plasma heated by the collision. The ratio between the warm H2 mass derived from Spitzer IRS spectroscopy and the H2 mass derived from CO fluxes is ~0.3 in the IGM of SQ, which is 10-100 times higher than in star-forming galaxies. In the shocked region, the ratio of the PAH-to-CO surface luminosities, commonly used to measure the star formation efficiency of the H2 gas, is lower (up to a factor 75) than the observed values in star-forming galaxies. We suggest that turbulence fed by the galaxy-tidal arm collision maintains a high heating rate within the H2 gas. This interpretation implies that the velocity dispersion on the scale of giant molecular clouds in SQ is one order of magnitude larger than the Galactic value. The high amplitude of turbulence may explain why this gas is not forming stars efficiently. [abridged version]
Sponsorship: IRAM is supported by INSU/CNRS (France), MPG (Germany) and IGN (Spain). PG also would like to acknowledge in particular the IRAM staff for help provided during the observations. UL acknowledges support by the research project AYA2007-67625-C02-02 from the Spanish Ministerio de Ciencia y Educación and the Junta de Andalucía (Spain) grant FQM-0108.
Publisher: American Astronomical Society; Institute of Physics
Keywords: Galaxies
Stephan's Quintet
Intergalactic medium
URI: http://hdl.handle.net/10481/28359
ISSN: 004-637X
Rights : Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License
Citation: Guillard, P. Turbulent molecular gas and star formation in the shocked intergalactic medium of Stephan's Quintet. Astrophysical Journal, 749(2): 158 (2012). [http://hdl.handle.net/10481/28359]
Appears in Collections:DFTC - Artículos

Files in This Item:

File Description SizeFormat
Guillard_turbulentmoleculargas.pdf571.63 kBAdobe PDFView/Open
Recommend this item

This item is licensed under a Creative Commons License
Creative Commons

Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.


Valid XHTML 1.0! OpenAire compliant DSpace Software Copyright © 2002-2007 MIT and Hewlett-Packard - Feedback

© Universidad de Granada