An expanded ultraluminous X-ray source catalogue

Abstract

Context. ULXs ($L_\textrm{X}>10^{39}$ erg s$^{-1}$) are excellent probes of accretion physics, star formation and IMBHs searches. As the sample size of X-ray data from modern observatories increases, producing extensive catalogues of ULXs and studying their collective properties is a possibility and a priority. Aims. We build a ULX catalogue based on one of the latest XMM-Newton releases, 4XMM-DR9, and the galaxy catalogue HECATE and study whether the properties of the expanded XMM-Newton ULX population are consistent with previous findings. Methods. We perform cross-matching between XMM-Newton sources and HECATE objects to identify host galaxies, and flag known interlopers in external catalogues and databases. Manual inspection of image data from PanSTARRS1 and the NASA/IPAC database is occasionally performed. We use distance and luminosity arguments to identify ULX candidates. Spectral, abundance and variability properties of the candidates are studied from 4XMM-DR9, HECATE and 4XMM-DR9s parameters. Results. We identify 779 ULX candidates. In spiral galaxies the number of ULX candidates per star forming rate is consistent with previous studies, and a significant ULX population in elliptical and lenticular is also found. Candidates hosted by late-type galaxies are more abundant, present harder spectra and undergo more and more extreme inter-observation variability than the early-type hosted ones. Around 30 candidates with $L_\textrm{X}>10^{41}$ erg s$^{-1}$ are also identified. Conclusions. Our results on the spectral and abundance properties of ULXs confirm the findings made by previous studies based on XMM-Newton and Chandra data, while our population-scale study on variability properties is unprecedented. Our study provides limited insight on the properties of the brightest ULX candidates due to the small sample size.