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Quasar (QSO) Redshift Catalog

Overview

See Section 6.2 of Chaussidon et al. (2023).

The Mg II Absorber VAC uses this as a parent catalog.

Citation

The catalog pipeline is described in Chaussidon et al. (2023) and were validated in Alexander el al. (2023). Please cite these two papers as root for all the catalogues that are based on these initial ones.

Data Access

Data URL: https://data.desi.lbl.gov/public/edr/vac/edr/qso/

NERSC access for DESI collaborators: 

/global/cfs/cdirs/desi/public/edr/vac/edr/qso/

Data Model

These catalogues were built with build_qso_catalog_from_tiles (for tiles version) and build_qso_catalog_from_healpix (for healpix version) functions from https://github.com/desihub/LSS/blob/main/py/LSS/qso_cat_utils.py

All the columns of these catalogues are described here:

Note: See qso_catalog_maker function for the explicit cuts. In particular, redrock redshift is rename Z_RR and the best redshift after the pipeline is called Z (it can be from a new redrock fit) and the associated redrock error is ZERR.

File description

Remarks

  • These catalogs contain the updated cuts for non-qso targets selection provided by the GQP group for non-QSO targets. See qso_catalog_maker for the explicit cut used.
  • Redshift column: the final redshift (best estimate that we have) is ‘Z’ and its correponding redrock error ‘Z_ERR’. This redshift is provided by Redrock either by the initial run or by the new run with QN prior and only QSO templates.
  • Other redshift columns: Z_RR is the initial redshift from Redrock. Z_QN is the redshift given by QuasarNet which is used as prior in the new run of RR in case where | Z_RR - Z_QN | > 0.05.

Content

  • QSO_cat_fuji_cumulative.fits: Contains all the objects detected as QSO by the pipeline in the cumulative directory. TARGETID is not unique since some objects have more than one observation. For combined observations, see the healpix catalogue where the TARGETID is unique.
  • QSO_cat_fuji_healpix.fits: Contains all the objects detected as QSO by the pipeline (concatenation from every survey/program in the release). Targetid is unique for a considered survey/program! (for instance some qsos were observed in dark and bright time WARNING: the pipeline is well tested in QSO targets. Optimal cuts were provided by GQP group but should have additional valiation. The most extended catalogue for cosmological analysis is _for_lyalpha.)
  • QSO_cat_fuji_healpix_only_qso_targets.fits: Contains all the QSO targets detected as QSO by the pipeline (concatenation from every survey / program in the release)
  • QSO_cat_fuji_healpix_for_lyalpha.fits: It is an extended catalogue design for Lyman-alpha group. Keep all the QSO targets detected as QSO by the pipeline + add non QSO targets which are SPECTYPE == QSO. For the moment this the largest QSO ‘certified’ catalogue. –> If you have any questions, contact me.
  • QSO_cat_fuji_healpix_all_targets.fits: Contains all the targets with the relevant information for the selection. No cut on if the object is or is not a QSO. (Note that the column QSO_MASKBITS gives you the selection with QSO_MASKBITS > 0 ). Objects in this file are not all considered as QSO. They do not incorporate the qualitative cuts!

Notes

  • The catalogs are available for cumulative and healpix directory.
  • Remove the bump at z~3.7 (29/03/22 update the cut).
  • Quality cuts (based on TS/VI papers): No cut ZWARN and keep only FIBERSTATUS == 0 | 8388608 | 16777216.
  • Maskbits available in the column QSO_MASKBITS:
    • 2**1 = spectype = qso (ie) selected by RR
    • 2**2 = selected by MgII
    • 2**3 = selected by QN
    • 2**4 = selected by QN and have a new redshift from new run of redrock with prior
  • Should contain all the relevant column to trace back the associated coaad file for each object. Add SURVEY / PROGRAM column for an easier selection.

Contact

Contact Edmond Chaussidon with any questions, comments, bugs, etc.