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Description
The galaxy NGC 1512 is interacting with the smaller galaxy NGC 1510 and shows a peculiar morphology, characterized by two extended arms immersed in an HI disc whose size is about four times larger than the optical diameter of NGC 1512. The authors have performed the first deep X-ray observation of the galaxies NGC 1512 and NGC 1510 with XMM-Newton to gain information on the population of X-ray sources and diffuse emission in this system of interacting galaxies. They have identified and classified the sources detected in the XMM-Newton field of view by means of spectral analysis, hardness-ratios calculated with a Bayesian method, X-ray variability, and cross-correlations with catalogs in optical, infrared, and radio wavelengths. They also made use of archival Swift (X-ray) and Australia Telescope Compact Array (radio) data to better constrain the nature of the sources detected with XMM-Newton. They detected 106 sources in the energy range of 0.2 - 12 keV, out of which 15 are located within the D<sub>25</sub> regions of NGC 1512 and NGC 1510 and at least six sources coincide with the extended arms. They identified and classified six background objects and six foreground stars. In the reference paper, they discuss the nature of a source within the D<sub>25</sub> ellipse of NGC 1512, whose properties indicate a quasi-stellar object or an intermediate ultra-luminous X-ray source. Taking into account the contribution of low-mass X-ray binaries and active galactic nuclei, the number of high-mass X-ray binaries detected within the D<sub>25</sub> region of NGC 1512 is consistent with the star formation rate obtained in previous works based on radio, infrared optical, and UV wavelengths. The authors detected diffuse X-ray emission from the interior region of NGC 1512 with a plasma temperature of kT = 0.68(0.31-0.87) keV and a 0.3 - 10 keV X-ray luminosity of 1.3E+38erg/s, after correcting for unresolved discrete sources. The galaxy pair NGC 1512/1510 was observed with XMM-Newton (ObsID: 0693160101) between 2012 June 16 (20:31 UTC) and 2012 June 17 (16:24 UTC) in a single, 63-ks exposure observation. The data analysis was performed through the XMM-Newton Science Analysis System (SAS) software (version 12.0.1). The observation was largely contaminated by high background due to proton flares. After rejecting time intervals affected by high background, the net good exposure time was reduced to 26.0 ks for PN, 39.8 ks for the MOS1 and 34.8 ks for the MOS2. For each instrument, the data were divided into five energy bands: <pre> B<sub>1</sub> : 0.2 - 0.5 keV B<sub>2</sub> : 0.5 - 1.0 keV B<sub>3</sub> : 1.0 - 2.0 keV B<sub>4</sub> : 2.0 - 4.5 keV B<sub>5</sub> : 4.5 - 12.0 keV </pre> For the PN, data were filtered to include only single events (PATTERN = 0) in the energy band B__1, and single and double events (PATTERN <= 4) for the other energy bands. The authors excluded the energy range 7.2 - 9.2 keV to reduce the background produced by strong fluorescence lines in the outer detector area. For the MOS, single to quadruple events (PATTERN <= 12) were selected. The source detection procedure is described in Section 2.1 of the reference paper. In the final step, the authors adopted a minimum likelihood of L = 6. They removed false detections (artifacts on the detectors or diffuse emission structures) by visual inspection. They detected 106 total point sources in the NGC 1512/1510 field of view. This table was created by the HEASARC in July 2014 based on <a href="https://cdsarc.cds.unistra.fr/ftp/cats/J/A+A/566/A115">CDS Catalog J/A+A/566/A115</a> files tableb1.dat and tableb2.dat. This is a service provided by NASA HEASARC .
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