Chandra/ACIS Catalog of Faint X-ray sources in Galactic globular clusters

This catalog was made as a wingman to the MAVERIC catalogs.

This catalog is created and maintained by Arash Bahramian. Reference: Bahramian et al., ApJ. in press.

• April 13: Final V1 Catalog prepared for publication.

• For the following clusters, the used images for the plots are not the stacked images: NGC 6388 and M 62. Thus, if a source's spectral plots appears to contradict its images (i.e., spectrum shows lots of counts, but the image looks empty), it's likely a detection in the other observations not included in the image. This choice for imaging is mainly driven by high off-axis angle difference between the data sets (or presence of a bright transient) in these clusters.

• CXOU_J : Source Name (following the Chandra convention for naming unregistered sources)
• plots : Link to source image and spectrum plots. The top left panel shows the location of the source within the cluster, to allow assessment of membership and impact of artifacts (the red circle denotes the extent of the cluster core,t the yellow circle display the cluster half-light radius, and the cyan box denotes the source region. These are superimposed on the \acis image). The top right panel is a zoom-in on the source, with various localization estimates marked (as green, yellow, and red circles for the centroiding, correlation and reconstruction techniques, respectively) and the extraction region pointed out as a blue polygo. The lower panels show results of spectral fitting for each of the three models (from top to bottom: power-law, blackbody, APEC). These include a representation of the binned spectrum and the posterior sample of fits, plus a corner plot showing the posterior distribution of model parameters. Note: the uncertainties annotated in the corner plots are 1-sigma estimates. The values tabulated in the catalog are 10% and 90% credible intervals.
• detection_quality_flag : 0 means good detection, 1 means marginal, 2 means likely false. All our population analysis are only considering 0s, 1s are included for cases where there is other independent evidence for presence of a source (e.g., multi-wavelength catalogs). 2s are mostly false and should be discarded in most cases, but are included to allow comparison and benchmark testing.
• spectrum_quality_flag : 0 means sufficient counts for moderate constraints on spectral parameters. 1 means parameters are loosely constrained, 2 means fitting (and determination of the best-fit model) are likely not trust-worthy.
• pile_up_flag : Whether the source is in danger of piled up. If True, photometry and spectroscopy presented in this catalog are likely inaccurate.
• foreground_flag : True means that the source could be a foreground object. This is determined based on comparing the upper limit on the source NH (from the best-fit model) compared to the host cluster NH (estimated based on E(B-V)). False doesn't necessarily reject that source is a foreground object. Just that the source NH is not inconsistent with the host cluster.
• Prob_AGN : Probability that the source may be a background AGN. Estimated based on source flux, population of sources in the cluster and the location of the source in the cluster (see the paper for details)
• abs_astrometry_flag : If the coordinates are corrected for absolute astrometry. This is currently only done for Terzan 5. For the rest of the catlaog, one should consider an additional 0.5'' uncertainty due to Chandra's astrometry.
• RA_centroid : Source RA estimated via centroiding
• Dec_centroid : Source Dec estimated via centroiding
• Centroid_error : Centroiding uncertainty radius (arcsec)
• RA_recon : Source RA estimated via image reconstruction
• Dec_recon : Source Dec estimated via image reconstruction
• RA_correlate : Source RA estimated via correlating image and PSF
• Dec_correlate : Source Dec estimated via correlating image and PSF
• Num_obs_total : Total number of observations
• Num_obs_merged : Number of observations merged for this source
• Exposure : Total exposure time (s)
• Primary_ccd : Primary CCD
• theta_avg : Average off-axis angle (arcmin)
• theta_low : Minimum off-axis angle (arcmin)
• theta_high : Maximum off-axis angle (arcmin)
• psf_fraction : Average PSF fraction
• src_cnts_* : Total source counts in different bands
• bkg_cnts_* : Total background counts in different bands
• backscale_* : Background scaling factor in different bands
• net_cnts_* : Net source counts in different bands
• net_cnts_sigma_up_* : 1-sigma upper-limit on net source counts in different bands
• net_cnts_sigma_low_* : 1-sigma lower-limit on net source counts in different bands
• significance_* : Photometric signal to noise ratio in different bands
• prob_no_source_* : p-value for no-source hypothesis in different bands
• min_KS_single_obs : Minimum p-value for KS variability test within each observation. YOU SHOULD NOT TRUST KS TEST FOR SOURCES WITH EXTREMELY LOW COUNTS.
• KS_all_data : p-value for KS variability test for all observations. YOU SHOULD NOT TRUST KS TEST FOR SOURCES WITH EXTREMELY LOW COUNTS.
• ae_abs_flx_0.5-2kev : Absorbed flux in the 0.5-2 keV band based on a power-law fit (erg/s/cm2)
• ae_abs_flx_2-8kev : Absorbed flux in the 2-8 keV band based on a power-law fit (erg/s/cm2)
• ae_abs_flx_0.5-8kev : Absorbed flux in the 0.5-8 keV band based on a power-law fit (erg/s/cm2)
• ae_abs_flx_0.5-10kev : Absorbed flux in the 0.5-10 keV band based on a power-law fit (erg/s/cm2)
• ae_abs_flx_1-10kev : Absorbed flux in the 1-10 keV band based on a power-law fit (erg/s/cm2)
• ae_unabs_flx_0.5-2kev : Unabsorbed flux in the 0.5-2 keV band based on a power-law fit (erg/s/cm2)
• ae_unabs_flx_2-8kev : Unabsorbed flux in the 2-8 keV band based on a power-law fit (erg/s/cm2)
• ae_unabs_flx_0.5-8kev : Unabsorbed flux in the 0.5-8 keV band based on a power-law fit (erg/s/cm2)
• ae_unabs_flx_0.5-10kev : Unabsorbed flux in the 0.5-10 keV band based on a power-law fit (erg/s/cm2)
• ae_unabs_flx_1-10kev : Unabsorbed flux in the 1-10 keV band based on a power-law fit (erg/s/cm2)
• fit1_pl_nh : Power-law fit NH (cm^-2)
• fit1_pl_nh_er- : Power-law fit lower uncertainty (cm^-2)
• fit1_pl_nh_er+ : Power-law fit upper uncertainty (cm^-2)
• fit1_pl_gamma : Power-law fit photon index
• fit1_pl_gamma_er- : Power-law fit photon index lower uncertainty
• fit1_pl_gamma_er+ : Power-law fit photon index upper uncertainty
• fit1_pl_flx_0.5-10 : Power-law fit unabsorbed flux in the 0.5-10 keV band (erg/s/cm2)
• fit1_pl_flx_0.5-10_er- : Power-law fit unabsorbed flux lower uncertainty in the 0.5-10 keV band (erg/s/cm2)
• fit1_pl_flx_0.5-10_er+ : Power-law fit unabsorbed flux upper uncertainty in the 0.5-10 keV band (erg/s/cm2)
• fit1_pl_lum_0.5-10 : Power-law fit Luminosity in the 0.5-10 keV band (assuming cluster distance; erg/s)
• fit1_pl_lum_0.5-10_er- : Power-law fit Luminosity lower uncertainty in the 0.5-10 keV band (erg/s)
• fit1_pl_lum_0.5-10_er+ : Power-law fit Luminosity upper uncertainty in the 0.5-10 keV band (erg/s)
• fit1_pl_logrelprob : Log10 of goodness probability of the power-law model (normalized relative to the best model, which will have a probability of 1).
• fit2_apec_nh : APEC fit NH (cm^-2)
• fit2_apec_nh_er- : APEC fit lower uncertainty (cm^-2)
• fit2_apec_nh_er+ : APEC fit upper uncertainty (cm^-2)
• fit2_apec_kT : APEC temperature (keV)
• fit2_apec_kT_er- : APEC temperature lower uncertainty (keV)
• fit2_apec_kT_er+ : APEC temperature upper uncertainty (keV)
• fit2_apec_flx_0.5-10 : APEC fit unabsorbed flux in the 0.5-10 keV band (erg/s/cm2)
• fit2_apec_flx_0.5-10_er- : APEC fit unabsorbed flux lower uncertainty in the 0.5-10 keV band (erg/s/cm2)
• fit2_apec_flx_0.5-10_er+ : APEC fit unabsorbed flux upper uncertainty in the 0.5-10 keV band (erg/s/cm2)
• fit2_apec_lum_0.5-10 : APEC fit Luminosity in the 0.5-10 keV band (assuming cluster distance; erg/s)
• fit2_apec_lum_0.5-10_er- : APEC fit Luminosity lower uncertainty in the 0.5-10 keV band (erg/s)
• fit2_apec_lum_0.5-10_er+ : APEC fit Luminosity upper uncertainty in the 0.5-10 keV band (erg/s)
• fit2_apec_logrelprob : Log10 of goodness probability of the APEC model (normalized relative to the best model, which will have a probability of 1).
• fit3_bbodyrad_nh : Blackbody fit NH (cm^-2)
• fit3_bbodyrad_nh_er- : Blackbody fit lower uncertainty (cm^-2)
• fit3_bbodyrad_nh_er+ : Blackbody fit upper uncertainty (cm^-2)
• fit3_bbodyrad_kT : Blackbody temperature (keV)
• fit3_bbodyrad_kT_er- : Blackbody temperature lower uncertainty (keV)
• fit3_bbodyrad_kT_er+ : Blackbody temperature upper uncertainty (keV)
• fit3_bbodyrad_flx_0.5-10 : Blackbody fit unabsorbed flux in the 0.5-10 keV band (erg/s/cm2)
• fit3_bbodyrad_flx_0.5-10_er- : Blackbody fit unabsorbed flux lower uncertainty in the 0.5-10 keV band (erg/s/cm2)
• fit3_bbodyrad_flx_0.5-10_er+ : Blackbody fit unabsorbed flux upper uncertainty in the 0.5-10 keV band (erg/s/cm2)
• fit3_bbodyrad_lum_0.5-10 : Blackbody fit Luminosity in the 0.5-10 keV band (assuming cluster distance; erg/s)
• fit3_bbodyrad_lum_0.5-10_er- : Blackbody fit Luminosity lower uncertainty in the 0.5-10 keV band (erg/s)
• fit3_bbodyrad_lum_0.5-10_er+ : Blackbody fit Luminosity upper uncertainty in the 0.5-10 keV band (erg/s)
• fit3_bbodyrad_logrelprob : Log10 of goodness probability of the Blackbody model (normalized relative to the best model, which will have a probability of 1).
• best_fit : Model with highest probability
• dist_from_gc_center : Source distance from the cluster center (arcmin)
• N_bg_agn_soft : Number of expected bkg sources with flux higher than the source in the 0.5-2 keV, within the half-light radius of the GC
• N_bg_agn_hard : Number of expected bkg sources with flux higher than the source in the 2-10 keV, within the half-light radius of the GC
• gc_name : Host globular cluster name
• gc_distance : globular cluster distance (kpc)
• gc_nh : Host cluster NH as estimated based on cluster E(B-V) (cm^-2)
• gc_nh_er : Host cluster NH uncertainy estimated based on cluster E(B-V) (cm^-2)
• gc_cr_rad : Host cluster core radius (arcmin)
• gc_hl_rad : Host cluster half-light radius (arcmin)