E-Locus - Institutional Repository of the University of Crete - Ultra-luminous X-ray sources in the most metal poor galaxies

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Identifier

000364748

Title

Ultra-luminous X-ray sources in the most metal poor galaxies

Alternative Title

Υπέρλαμπρες πηγές ακτίνων Χ στους πιο μεταλλικά φτωχούς γαλαξίες

Author

Τσαντάκη, Μαρία

Thesis advisor

Ζέζας, Ανδρέας

Abstract

We investigated the Ultra-luminous X-ray source (ULX) population in a sample of 25 extremely metal poor galaxies (XMPGs) in the local universe. We processed recent observations from the Chandra X-ray Observatory with the CIAO software and detected 6 X-ray sources in the 0.3-8.0 keV band. We obtained spectra for these sources and found their X-ray luminosities to be in the range (0.7-7.5)×10³⁹ erg/sec, characterizing them as ULX sources. In addition, we processed infrared data for these galaxies from the Spitzer Space telescope in the 24 micron band and performed aperture photometry in order to measure their luminosities. We used the 24μm luminosity to estimate their Star Formation Rate (SFR). Moreover, we compared the XMPGs with 33 galaxies from the Spitzer Infrared Nearby Galaxies Survey (SINGS) sample. For the SINGS galaxies we calculated the SFR using IR and Hα data as well as the number of their ULXs, from the literature. Comparing these samples of different metallicities (High, Intermediate and Low), we reached the conclusion that there is a trend showing that the number of ULXs per SFR is decreasing with metallicity which means that ULXs may prefer metal poor environments. This conclusion comes in agreement with models that derive the ULX population from High Mass X-ray Binaries (HMXBs) with mass transfer through Roche Lobe Overflow (RLO).

Language

English

Subject

Binaries

Metallicity

ULXs

Ακτίνες-Χ

Διπλά συστήματα αστέρων

Μεταλλικότητα

Issue date

2011-03-18

Collection