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Balrog matches to deep field, photo-z's, and spectro-z's

Notes by Huan Lin, 21 Mar 2019

Matching Balrog detections to deep field coordinates

The Balrog Run 1 detected objects were matched to the Y3 deep field coadd objects in order to obtain the original true RA and Dec of the respective parent deep field objects.

Query used on DESSCI for the Balrog/COSMOS detections:

select y.bal_id, y.true_id, y.true_tilename, y.true_ra, y.true_dec, y.meas_cm_mag_g, y.meas_cm_mag_r,
y.meas_cm_mag_i, y.meas_cm_mag_z, y.true_cm_mag_deredden_g, y.true_cm_mag_deredden_r, 
y.true_cm_mag_deredden_i, y.true_cm_mag_deredden_z, c.tilename, c.ra, c.dec 
from YANNY.BALROG_MATCHED_CATALOG_FLATTEN y, Y3A2_MISC_MOF_V3_COSMOS c 
where y.true_id = c.coadd_object_id and y.true_tilename like '%COSMOS%'; > balrog_cosmos.fits

Query used on DESSCI for the Balrog/SN detections:

select y.bal_id, y.true_id, y.true_tilename, y.true_ra, y.true_dec, y.meas_cm_mag_g, y.meas_cm_mag_r, 
y.meas_cm_mag_i, y.meas_cm_mag_z, y.true_cm_mag_deredden_g, y.true_cm_mag_deredden_r, 
y.true_cm_mag_deredden_i, y.true_cm_mag_deredden_z, c.tilename, c.ra, c.dec 
from YANNY.BALROG_MATCHED_CATALOG_FLATTEN y, Y3A2_MISC_MOF_V1_COADD_TRUTH c 
where y.true_id = c.coadd_object_id and y.true_tilename like '%SN%'; > balrog_sn.fits

The resulting fits files are here:

The true RA and Dec of the parent deep field objects are actually given by the columns named RA and DEC in the files above (and below).

Matching to COSMOS/Laigle photo-z's

The Balrog/COSMOS data in balrog_cosmos.fits were then matched to the Laigle et al. (2016) high-precision photo-z catalog, using the closest match within a 1-arcsec match radius. Before matching, the Laigle et al. catalog objects were first cut using the following criteria:
  • FLAG_COSMOS = 1 to select the 2 deg^2 COSMOS area
  • FLAG_PETER = 0 to select "good", non-masked areas
  • FLAG_HJMCC = 0 to select overlap with UltraVISTA near-IR data
  • TYPE = 0 to select galaxies
  • ZMIN_CHI2 > 0 to select photo-z > 0
Out of the 466925 Balrog detected objects in balrog_cosmos.fits, 328474 objects have a match in the (cut) Laigle et al. catalog, and the resulting matches are given in these two fits files, which are row-by-row the same objects:

Matching to the DES SV spectroscopic training/validation sets

The Balrog data were also matched (with a 1-arcsec radius) to the spectroscopic redshifts in the standardized training and validation sets used in the DES SV photo-z paper (Sanchez et al. 2014). The results are given in the following files:
  • balrog_cosmos_match_sv_deep_std.fits gives the matches between Balrog/COSMOS detected objects and the SV "deep" training+validation sample (the resulting matches come primarily from the zCOSMOS Bright survey)
  • balrog_sn_match_sv_main_std.fits gives the matches between Balrog/SN detected objects and the SV "main" training+validation sample

Matching to zCOSMOS-bright DR3

The Balrog/COSMOS data in balrog_cosmos.fits were matched to the zCOSMOS-bright DR3 sample, using the closest match within a 1-arcsec match radius. The results are given in this file, including the following 3 columns from zCOSMOS (see here):
  • redshift ZSPEC (originally REDSHIFT in zCOSMOS DR3 catalog)
  • confidence class CC
  • ZCOSMOS_OBJECT_ID (originally OBJECT_ID in zCOSMOS DR3 catalog)

A conservative cut would be 3 <= CC < 5 to select high confidence redshifts (see page 4 of the zCOSMOS DR3 documentation) and ZSPEC > 0.01 to remove stars.