Ultraluminous X-ray sources in the first eROSITA survey I. Candidate catalogs
Abstract
Ultraluminous X-ray sources (ULXs) are luminous non-nuclear X-ray point sources embedded in galaxies. Their luminosities exceeding 10^39 erg/s potentially require sub-Eddington accretion by objects with masses from ~10^2M⊙ to ~10^4M⊙ or supercritical accretion beyond the Eddington limit by stellar mass black holes or neutron stars. We identified ULXs by searching for X-ray counterparts in the ~10^5 galaxies of the HECATE catalog in the footprint of the first eROSITA all-sky survey, while excluding nuclear regions to avoid the selection of active galactic nuclei (AGN). We characterized the completeness of the sample and its contamination by unidentified AGN and determined the influence of source confusion. The catalog is unaffected by X-ray selection biases. We removed known contaminants such as supernovae, stars, and AGN, and manually vetted all candidates to further remove contaminants. We derived the X-ray selection function and fraction of unidentified AGN interlopers using a simulation with subsequent source detection. We present two samples of ULX candidates. The main sample consists of 90 sources with highly confident X-ray detections, 53 of which are identified for the first time. This sample is complete to a distance of ~7Mpc, contains at most 29% of unknown background AGN, and is mostly unaffected by source confusion. Several candidates are newly identified even though their locations have been observed by other instruments before, and some previously reported candidates we expected to identify are absent from our sample, demonstrating the transient behavior of ULXs. Based on our list of less confident detections, we also provide an extended catalog of 260 sources identified as potential candidates for further ULX identifications. Of these, 245 are identified as potential candidates for the first time. (Abridged)
Related
- A statistical hardness classification of ultraluminous X-ray sources using long-term Swift/XRT monitoring
- A statistical hardness classification of ultraluminous X-ray sources using long-term Swift /XRT monitoring
- eROSITA all-sky survey - stars and optical loading
- The SRG/eROSITA All-Sky Survey. Early dark energy and Hubble constant from the cluster mass function
- The NIKA2 Cosmological Legacy Survey in COSMOS: Final 1.2,mm and 2,mm source catalogs and redshift distribution of dusty star-forming galaxies
BibTeX
@article{weber2026ultraluminous,
title = {{Ultraluminous X-ray sources in the first eROSITA survey I. Candidate catalogs}},
author = {P Weber and T.P Roberts and S Hämmerich and E Kyritsis and A Zezas and M.G.F Mayer and A Zainab and I Kreykenbohm and A Merloni and M Sasaki and A Schwope and M Middleton and A Basu-Zych and A Hornschemeier and N Vulic and M Salvato and N Webb and H Tranin and N Schettino and C Kirsch and S Saeedi and F Zangrandi and M Lorenz and L Dauner and T Dauser and F Haberl and C Maitra and Z Igo and A Santangelo and L Ducci and J Wilms},
journal = {Astronomy \& Astrophysics - A\&A},
year = {2026},
month = sep,
doi = {10.1051/0004-6361/202659942},
eprint = {2608.25620},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05735455v1},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Ultraluminous X-ray sources in the first eROSITA survey I. Candidate catalogs
AU - P Weber
AU - T.P Roberts
AU - S Hämmerich
AU - E Kyritsis
AU - A Zezas
AU - M.G.F Mayer
AU - A Zainab
AU - I Kreykenbohm
AU - A Merloni
AU - M Sasaki
AU - A Schwope
AU - M Middleton
AU - A Basu-Zych
AU - A Hornschemeier
AU - N Vulic
AU - M Salvato
AU - N Webb
AU - H Tranin
AU - N Schettino
AU - C Kirsch
AU - S Saeedi
AU - F Zangrandi
AU - M Lorenz
AU - L Dauner
AU - T Dauser
AU - F Haberl
AU - C Maitra
AU - Z Igo
AU - A Santangelo
AU - L Ducci
AU - J Wilms
PY - 2026
DA - 2026/09/03
JO - Astronomy & Astrophysics - A&A
DO - 10.1051/0004-6361/202659942
UR - https://hal.science/hal-05735455v1
AB - Ultraluminous X-ray sources (ULXs) are luminous non-nuclear X-ray point sources embedded in galaxies. Their luminosities exceeding 10^39 erg/s potentially require sub-Eddington accretion by objects with masses from ~10^2M_⊙ to ~10^4M_⊙ or supercritical accretion beyond the Eddington limit by stellar mass black holes or neutron stars. We identified ULXs by searching for X-ray counterparts in the ~10^5 galaxies of the HECATE catalog in the footprint of the first eROSITA all-sky survey, while excluding nuclear regions to avoid the selection of active galactic nuclei (AGN). We characterized the completeness of the sample and its contamination by unidentified AGN and determined the influence of source confusion. The catalog is unaffected by X-ray selection biases. We removed known contaminants such as supernovae, stars, and AGN, and manually vetted all candidates to further remove contaminants. We derived the X-ray selection function and fraction of unidentified AGN interlopers using a simulation with subsequent source detection. We present two samples of ULX candidates. The main sample consists of 90 sources with highly confident X-ray detections, 53 of which are identified for the first time. This sample is complete to a distance of ~7Mpc, contains at most 29% of unknown background AGN, and is mostly unaffected by source confusion. Several candidates are newly identified even though their locations have been observed by other instruments before, and some previously reported candidates we expected to identify are absent from our sample, demonstrating the transient behavior of ULXs. Based on our list of less confident detections, we also provide an extended catalog of 260 sources identified as potential candidates for further ULX identifications. Of these, 245 are identified as potential candidates for the first time. (Abridged)
SN - 0004-6361
SN - 1432-0746
ER -