A search for stellar X-ray sources in the Sagittarius and Carina dwarf galaxies

I. X-ray observations

¹ Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK e-mail: gtbr@mssl.ucl.ac.uk
² School of Physics A28, University of Sydney, NSW 2006, Australia

Received: 3 July 2006
Accepted: 26 August 2006

Abstract

ROSAT observations found no convincing evidence for X-ray sources located in local dwarf spheroidal galaxies (dSph). Now with more sensitive instruments on board Chandra and XMM-Newton we can reach fainter luminosity levels. We report on an observation of the Sagittarius (Sgr) dSph made using Chandra and an observation of the Carina (Car) dSph made using XMM-Newton. Our observations are sensitive to sources with X-ray luminosities in the 0.1–10 keV band of ~ erg s^-1 and 3 erg s^-1 for the Sgr and Car fields respectively. We have identified a total of 80 sources in the Sgr field and 53 sources in the Car field. Although the source numbers are roughly consistent with the expected number of background AGN, we found a small fraction of X-ray sources which were soft and could be located in the host dSph. Follow-up optical/IR observations may help to identify their optical counterparts and hence determine their nature.