Journal Article

Soft-band X/K luminosity ratios in late-type galaxies and constraints on the population of supersoft X-ray sources

Á. Bogdán and M. Gilfanov

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 412, issue 1, pages 401-410
Published in print March 2011 | ISSN: 0035-8711
Published online March 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17916.x
Soft-band X/K luminosity ratios in late-type galaxies and constraints on the population of supersoft X-ray sources

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We study X-ray to K-band luminosity ratios (LX/LK) of late-type galaxies in the 0.3–0.7 keV energy range. From the Chandra archive, we selected nine spiral and three irregular galaxies with point source detection sensitivity better than 5 × 1036 erg s−1 in order to minimize the contribution of unresolved X-ray binaries. In late-type galaxies cold gas and dust may cause significant interstellar absorption, therefore we also demanded the existence of publicly available H i maps. The obtained LX/LK ratios vary between (5.4 and 68) × 1027 erg s−1 L−1K,⊙ exceeding by factors of 2–20 the values obtained for gas-poor early-type galaxies. Based on these results we constrain the role of supersoft X-ray sources as progenitors of Type Ia supernovae (SNe Ia). For the majority of galaxies the upper limits range from ∼ 3 to ∼15 per cent of the SN Ia frequency inferred from K-band luminosity, but for a few of them no meaningful constraints can be placed. On a more detailed level, we study individual structural components of spiral galaxies: bulge and disc, and, for grand design spiral galaxies, arm and interarm regions.

Keywords: supernovae: general; galaxies: irregular; galaxies: spiral; galaxies: stellar content; X-rays: galaxies; X-rays: stars

Journal Article.  6926 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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