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Last modified: 16 February 2021

URL: https://cxc.cfa.harvard.edu/csc/csc_crossmatches.html

CSC 2.0 Crossmatches

Introduction

This page contains links and short descriptions of the tables of crossmatches between the Chandra Source Catalog 2.0 and catalogs of sources from several multi-wavelength surveys. All crossmatches have been performed with a Bayesian method developed by Budavari & Szalay (2008) as implemented and extended by A. Rots (2020) that takes into account local source density as well as both error ellipses and raw-size ellipses of the sources.

CSC 2.0 sources are extracted from the CSC 2.0 Master Sources table. For each crossmatched source pair the match probability (between 0.0 and 1.0), match type (E when positional error ellipse is used, R if source raw size is used) and match grade (D for definite matches, L for likely matches) are provided. The details on these columns can be found here. In addition, ambiguous matches are provided in separate tables.


SDSS

CSC 2.0-SDSS unambiguous matches

The table (CSV format) linked below contains the pairs of unambiguous matches between CSC 2.0 and the SDSS DR15 catalog. CSC 2.0 sources are from the "Master Sources" table while SDSS DR15 are from the "Star" or "Galaxy" views. The descriptions of all the columns provided in the table can be found below the link. A web-based query tool for the table provided by the VizieR service can be found here.

Files:

Final CSC 2.0-SDSS matches (CSV, TSV)

Column Name Class Description
1 CSC2_ID String CSC 2.0 name, 2CXO JHHMMSS.s+DDMMSS (name)
2 CSC2_Type String CSC source type (P for point sources, X for extended compact sources < 1 arcmin)
3 CSC2_RA Double CSC 2.0 Right Ascension (ICRS) (ra)
4 CSC2_Dec Double CSC 2.0 Declination (ICRS) (dec)
5 CSC2_ErrMaj_95% Double CSC 2.0 semi-major axis of the 95% confidence level position error ellipse (errellipser0)
6 CSC2_ErrMin_95% Double CSC 2.0 semi-minor axis of the 95% confidence level position error ellipse (errellipser1)
7 CSC2_ErrPA Double CSC 2.0 position angle relative to the local true N of the major axis of the 95% confidence level position error ellipse
8 CSC2_RawMaj_1-sigma Double CSC 2.0 semi-major axis of the 1σ ellipse fitted to the source as seen in the image
9 CSC2_RawMin_1-sigma Double CSC 2.0 semi-minor axis of the 1σ ellipse fitted to the source as seen in the image
10 CSC2_RawPA Double CSC 2.0 position angle of the 1σ ellipse fitted to the source as seen in the image
11 CSC2_MatchMaj_1-sigma Double CSC 2.0 match major axis of the ellipse used for the crossmatch
12 CSC2_MatchMin_1-sigma Double CSC 2.0 match semi-minor of the ellipse used for the crossmatch
13 CSC2_MatchPA_1-sigma Double CSC 2.0 match position angle of the ellipse used for the crossmatch
14 SDSSDR15_ID Long SDSS unique identifier
15 SDSSDR15_Type String SDSS Type classification (type) (S for stars, G for galaxies)
16 SDSSDR15_RA Double SDSS Right Ascension (J2000)
17 SDSSDR15_Dec Double SDSS Declination (J2000)
18 SDSSDR15_ErrMaj_1-sigma Double SDSS semi-major axis of the 1σ error ellipse (SDSS semi-major axis of the 1σ error ellipse, i.e larger of raErr and decErr [arcsec])
19 SDSSDR15_ErrMin_1-sigma Double SDSS semi-minor axis of the 1σ error ellipse (SDSS semi-minor axis of the 1σ error ellipse, i.e smaller between raErr and decErr [arcsec])
20 SDSSDR15_ErrPA_1-sigma Float SDSS position angle (local true N) of the 1σ error ellipse with major and minor axes
21 SDSSDR15_RawMaj_1-sigma Double SDSS semi-major axis of the source raw 1σ size ellipse, calculated from adaptive moments
22 SDSSDR15_RawMin_1-sigma Double SDSS semi-minor axis of the source raw 1σ size ellipse, calculated from adaptive moments
23 SDSSDR15_RawPa_1-sigma Double SDSS position angle of the source raw 1σ size ellipse, calculated from adaptive moments
24 SDSSDR15_MatchMaj_1-sigma Double SDSS match semi-major of the ellipse used for the crossmatch
25 SDSSDR15_MatchMin_1-sigma Double SDSS match semi-minor of the ellipse used for the crossmatch
26 SDSSDR15_MatchPA_1-sigma Double SDSS match position relative to the local true N of the ellipse used for the crossmatch
27 CSC2-SDSSDR15_separation Double Angular distance between CSC 2.0 and SDSS DR15 sources
28 Match_probability Double Match probability
29 Match_type String Match type (E when positional error ellipse is used, R if source raw size is used)
30 Match_grade String Match grade (D for definite matches, L for likely matches)

CSC 2.0-SDSS ambiguous matches

The two tab-delimited tables linked below contain the sources from each catalog that have multiple accepted matches in the other catalog (i.e. CSC 2.0 sources with multiple SDSS crossmatches and vice versa). Please notice that these ambiguous crossmatches are not to be confused with ambiguous matches between per-observation sources and master sources internal to the CSC 2.0 catalog. The ambiguous matches tables (CSV format) contain a variable number of columns (but never less than three) with compound formats described below:

  • The first column (format %s (%c):) contains the IDs of that catalog's sources that have multiple matches, followed by a space, a single character in parentheses indicating the source's type, and a colon.

All subsequent columns have a single compound format (%s (%c %5.3f %5.3f %c)), containing:

  • the ID of a matching source from the other catalog, followed by a space and an opening parenthesis
  • a single character indicating that source's type, followed by a space
  • the separation of the matched pair, followed by a space
  • the match probability, followed by a space
  • the match type (E for error ellipse, R for raw size ellipse), followed by a closing parenthesis

Files:

Ambiguous CSC 2.0 matches with SDSS DR15 (CSV, TSV)

Ambiguous SDSS DR15 matches with CSC 2.0 (CSV, TSV)