Chandra Observation of the Starburst Galaxy NGC 2146

Abstract

We present six monitoring observations of the starburst galaxy NGC 2146 using the Chandra X-ray Observatory. We have detected 67 point sources in the 8'.7 x 8'.7 field of view of the ACIS-S detector. Six of these sources were Ultra-Luminous X-ray Sources, the brightest of which has a luminosity of 5 x 10^{39} ergs s^{-1}. One of the source, with a luminosity of ~1 x 10^{39} ergs s^{-1}, is coincident with the dynamical center location, as derived from the ^{12}CO rotation curve. We suggest that this source may be a low-luminosity active galactic nucleus. We have produced a table where the positions and main characteristics of the Chandra-detected sources are reported. The comparison between the positions of the X-ray sources and those of compact sources detected in NIR or radio does not indicate any definite counterpart. Taking profit of the relatively large number of sources detected, we have derived a logN-logS relation and a luminosity function. The former shows a break at \~10^{-15} ergs cm^{-2} s^{-1}, that we interpret as due to a detection limit. The latter has a slope above the break of 0.71, which is similar to those found in the other starburst galaxies. In addition, a diffuse X-ray emission has been detected in both, soft (0.5--2.0keV) and hard (2.0--10.0keV), energy bands. The spectra of the diffuse component has been fitted with a two (hard and soft) components. The hard power-law component, with a luminosity of ~4 x 10^{39} ergs s^{-1}, is likely originated by unresolved point sources, while the soft component is better described by a thermal plasma model with a temperature of 0.5keV and high abundances for Mg and Si.