XMM-Newton observations of the hot spot galaxy NGC 2903

Abstract

We report on the first deeper X-ray broad-band observation of the hot spot galaxy NGC 2903 obtained with XMM-Newton. X-ray imaging and spectra of the spiral barred galaxy NGC 2903 were obtained from XMM-Newton archival data to study its X-ray population and the conditions of the hot gas in its central region. We investigate the spectral properties of the discrete point-source population and give estimates of their X-ray spectral parameters. By analysing the RGS spectra, we derive temperature and abundances for the hot gas located in its central region. A total of six X-ray point sources (four of them ULX candidates) were detected in the energy range of 0.3-10.0 keV located within the galaxy D₂₅ optical disk. Three of these sources are detected for the first time, and one of them, XMM-NGC2903 X2 with a luminosity of higher than 10³⁹ erg s^-1. After fitting three different models, we were able to estimate their luminosities, which are compatible with those of binaries with a compact object in the form of black holes (BHs) rather than neutron stars (NSs). We extracted the combined first-order RGS1 and RGS2 spectra of its central region, which display several emission lines. The spectrum is dominated by a strong O viii Lyα emission line along with Ne x Lyα and several Fe xvii features. The O vii complex is also significantly detected, although only the forbidden and resonance lines could be resolved. Both O vii f and r lines seem to be of similar strength, which is consistent with the presence of the collisionally ionized gas that is typical of starburst galaxies. We fitted the spectrum to a model for a plasma in collisional ionization equilibrium (CIE) and the continuum was modelled with a power law, resulting in a plasma temperature of T = 0.31 ± 0.01 keV and an emission measure EM ≡ n_Hn_eV = 6.4_-0.4^+0.5 × 10⁶¹ cm^-3. We also estimated abundances that are consistent with solar values.