Authors: Rosa González, D.; Terlevich, E.; Jiménez Bailón, E.¹; Terlevich, R.; Ranalli, P.²; Comastri, A.³; Laird, E.⁴; Nandra, K.⁴

Source: Monthly Notices of the Royal Astronomical Society, Volume 399, Number 1, October 2009 , pp. 487-496(10)

Publisher: Wiley-Blackwell

Abstract:

In an effort to understand the correlation between X-ray emission and present star formation rate, we obtained XMM-Newton data to estimate the X-ray luminosities of a sample of actively star-forming H iigalaxies. The obtained X-ray luminosities are compared to other well-known tracers of star formation activity such as the far-infrared and the ultraviolet luminosities. We also compare the obtained results with empirical laws from the literature and with recently published analysis applying synthesis models. We use the time delay between the formation of the stellar cluster and that of the first X-ray binaries, in order to put limits on the age of a given stellar burst. We conclude that the generation of soft X-rays, as well as the Hα or infrared luminosities is instantaneous. The relation between the observed radio and hard X-ray luminosities, on the other hand, points to the existence of a time delay between the formation of the stellar cluster and the explosion of the first massive stars and the consequent formation of supernova (SN) remnants and high-mass X-ray binaries, which originate the radio and hard X-ray fluxes, respectively. When comparing hard X-rays with a star formation indicator that traces the first million years of evolution (e.g. Hα  luminosities), we found a deficit in the expected X-ray luminosity. This deficit is not found when the X-ray luminosities are compared with infrared luminosities, a star formation tracer that represents an average over the last 10⁸ yr. The results support the hypothesis that hard X-rays are originated in X-ray binaries which, as SN remnants, have a formation time delay of a few mega years after the star-forming burst.

Keywords: galaxies: evolution; galaxies: starburst; X-rays: galaxies

Document Type: Research article

DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15300.x

Affiliations: 1: Instituto de Astronomía, Universidad Nacional Autónoma de México, Apartado Postal 70-264, 04510-México DF, México 2: Universitá di Bologna, Dipartimento di Astronomia, via Ranzani 1, 40127 Bologna, Italy 3: INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127 Bologna, Italy 4: Astrophysics Group, Imperial College London, Blackett Laboratory, Prince Consort Road, London SW7 2AZ

Publication date: 2009-10-01

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