Table information for 'ztf.dataquality'

General

Table Description:

Image and PSF quality metrics for ZTF detections, including pixel statistics, PSF fit parameters, photometric calibration coefficients, and astrometric performance.

This table is available for ADQL queries and through the TAP endpoint.

Resource Description:

Legacy ZTF astronomical catalog containing objects, detections, photometric measurements, classifications, and cross-matches from the Zwicky Transient Facility (ZTF) survey, as processed by the ALeRCE broker pipeline.

For a list of all services and tables belonging to this table's resource, see Information on resource 'ALeRCE ZTF Legacy Catalog'

Citing this table

To cite the table as such, we suggest the following BibTeX entry:

@MISC{vo:ztf_dataquality,
  year=2026,
  title={{ZTF} Data Quality Metrics},
  author={{ALeRCE} Team},
  url={http://tap.alerce.online/tableinfo/ztf.dataquality},
  howpublished={{VO} resource provided by the {ALeRCE} {TAP} service}
}

Columns

Sorted by DB column index. [Sort alphabetically]

NameTable Head DescriptionUnitUCD
candid Candid Candidate identifier N/A meta.id
oid Oid Object identifier N/A meta.id;src
fid Fid Filter identifier N/A meta.id;instr.filter
xpos Xpos X pixel position of candidate on the image pix pos.cartesian.x
ypos Ypos Y pixel position of candidate on the image pix pos.cartesian.y
chipsf Chipsf Reduced chi-squared of PSF fit to the candidate N/A stat.fit.chi2
sky Sky Local sky background estimate N/A instr.background
fwhm Fwhm Full-width at half-maximum of the image PSF arcsec instr.obsty.seeing
classtar Classtar SExtractor star-galaxy classifier score (0=galaxy, 1=star) N/A src.class.starGalaxy
mindtoedge Mindtoedge Minimum distance of candidate to image edge pix pos.angDistance
seeratio Seeratio Ratio of PSF FWHM to the average seeing FWHM in the field N/A stat.ratio
aimage Aimage Semi-major axis of Gaussian fit to candidate arcsec src.morph.param
bimage Bimage Semi-minor axis of Gaussian fit to candidate arcsec src.morph.param
aimagerat Aimagerat Ratio of aimage to PSF semi-major axis N/A stat.ratio;src.morph.param
bimagerat Bimagerat Ratio of bimage to PSF semi-minor axis N/A stat.ratio;src.morph.param
nneg Nneg Number of negative pixels in a 5x5 pixel stamp around the candidate N/A meta.number
nbad Nbad Number of bad pixels in a 5x5 pixel stamp around the candidate N/A meta.number
sumrat Sumrat Ratio of sum of pixel values to sum of absolute pixel values N/A stat.ratio
scorr Scorr Peak S/N in the corrected score image N/A stat.snr
dsnrms Dsnrms Ratio of differential to non-differential RMS noise N/A stat.snr
ssnrms Ssnrms Ratio of science to non-differential RMS noise N/A stat.snr
magzpsci Magzpsci Photometric zero-point of science image mag phot.calib
magzpsciunc Magzpsciunc Uncertainty in photometric zero-point mag stat.error;phot.calib
magzpscirms Magzpscirms RMS scatter of zero-point calibration fit mag stat.rms;phot.calib
nmatches Nmatches Number of catalog stars used for photometric calibration N/A meta.number
clrcoeff Clrcoeff Color coefficient for photometric calibration N/A phot.color;arith.ratio
clrcounc Clrcounc Uncertainty in color coefficient N/A stat.error;phot.color;arith.ratio
zpclrcov Zpclrcov Covariance between zero-point and color coefficient N/A stat.covariance;phot.calib
zpmed Zpmed Median zero-point magnitude across the field mag phot.calib;stat.median
clrmed Clrmed Median color coefficient across the field N/A phot.color;stat.median
clrrms Clrrms RMS scatter of color coefficient fit N/A stat.rms;phot.color
exptime Exptime Exposure time s time.duration;obs.exposure

Columns that are parts of indices are marked like this.

VOResource

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