Open Access
Table B.1
Description of the columns of our cross-match catalogs between eRASS:4 and 4FGL-DR4.
| Name | Units | Description |
|---|---|---|
| # | Rank of X-ray source by match probability | |
| Name_ero | eROSITA source ID following IAU naming conventions | |
| RA_ero | deg | Right ascension (ICRS) of X-ray source |
| DEC_ero | deg | Declination (ICRS) of X-ray source |
| sigma_ero | arcsec | One-sigma(a) positional error of X-ray source |
| CR_ero | cts−1 | X-ray count rate in 0.2 – 2.3 keV |
| F_ero | erg cm−2 s−1 | X-ray source flux in 0.2 – 2.3 keV, determined via an energy conversion factor (Merloni et al. 2024) from the count rate |
| DET_LIKE_ero | X-ray detection likelihood (Brunner et al. 2022; Merloni et al. 2024) | |
| EXT_LIKE_ero | X-ray extent likelihood (Brunner et al. 2022; Merloni et al. 2024) | |
| Name_4FGL | Name of γ-ray source in 4FGL-DR4 catalog (Ballet et al. 2023) | |
| Class2_4FGL | Class of low-probability association(b) of γ-ray source in 4FGL-DR4 catalog (Abdollahi et al. 2020) | |
| Assoc2_4FGL | Low-probability association(b) of γ-ray source in 4FGL-DR4 catalog (Abdollahi et al. 2020) | |
| RA_4FGL | deg | Right ascension (ICRS) of γ-ray source |
| DEC_4FGL | deg | Declination (ICRS) of γ-ray source |
| aerr_4FGL | arcmin | Semi-major axis of γ-ray 95% error ellipse |
| berr_4FGL | arcmin | Semi-minor axis of γ-ray 95% error ellipse |
| phierr_4FGL | deg (east of north) | Position angle of γ-ray error ellipse on the sky |
| nu_4FGL | deg−2 | Density of eRASS:4 X-ray sources within a 2° radius around γ-ray source |
| exp_Field | Expectation value for the number of X-ray chance alignments (denominator in Eq. 4) | |
| F_4FGL | erg cm−2 s−1 | γ-ray source flux in the range 100 MeV – 100 GeV |
| Prior_PSR | Prior probability  for a source to be a pulsar, rather than blazar, based on its γ-ray properties |
|
| Prior_youngold | Prior probability  for a source to be a young pulsar, rather than a millisecond pulsar, based on its γ-ray properties |
|
| d_mahalanobis | Mahalanobis distance, i.e., the distance between X-ray and γ-ray source positions, normalized by the total positional error in the given direction | |
| BF_pos | Purely positional Bayes factor of the association, i.e., value of Eq. 4 with c = 1. | |
| log_flux_ratio | Logarithmic γ-to-X-ray flux ratio, i.e., log Fγ/Fx | |
| Prior_fr_AGN | Likelihood ratio, assuming AGN nature, of having a match rather than a background X-ray source based on only X-ray and γ-ray fluxes, i.e., ϕt(log Fx | log Fγ)/ϕB(log Fx) (Eqs. 6 and 7) | |
| Prior_fr_YNG | Same as above, but assuming young pulsar nature | |
| Prior_fr_MSP | Same as above, but assuming millisecond pulsar nature | |
| P_i_PSR | Combined posterior probability  (Eq. 8) for the given X-ray and γ-ray source to be matched, and to be of pulsar nature |
|
| P_i_YNG | Same as above, but only for young pulsar nature | |
| P_i_MSP | Same as above, but only for millisecond pulsar nature | |
| P_i_AGN | Same as above, but for AGN (blazar) nature | |
| P_i | Same as above, for any nature, i.e.,  |
|
| Comment | Comment on the match, for instance, on possible alternative nature of the X-ray source or possible spurious origin. | |
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