Table information for 'alerce_tap.ztf_dataquality'

General

Table Description:

Detailed data quality metrics for ZTF detections including image position, PSF-fit quality (chi-square, FWHM), SExtractor properties, pixel statistics, photometric calibration parameters, and signal-to-noise measurements.

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

Resource Description:

Multi-survey astronomical object catalog containing astrometric and statistical information from multiple surveys. This table provides aggregated properties for astronomical objects including position, detection statistics, and temporal coverage.

For a list of all services and tables belonging to this table's resource, see Information on resource 'ALeRCE Multi-Survey Object Catalog'

Citing this table

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

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

Columns

Sorted alphabetically. [Sort by DB column index]

NameTable Head DescriptionUnitUCD
aimage Aimage Windowed profile RMS along major axis from SExtractor pix phys.angSize.smajAxis
aimagerat Aimagerat Ratio: aimage / fwhm N/A arith.ratio
bimage Bimage Windowed profile RMS along minor axis from SExtractor pix phys.angSize.sminAxis
bimagerat Bimagerat Ratio: bimage / fwhm N/A arith.ratio
chipsf Chipsf Reduced chi-square for PSF-fit N/A stat.fit.goodness
classtar Classtar Star/Galaxy classification score from SExtractor N/A src.class.starGalaxy
clrcoeff Clrcoeff Color coefficient from linear fit from photometric calibration of science image N/A arith.factor
clrcounc Clrcounc Color coefficient uncertainty from linear fit (corresponding to clrcoeff) N/A stat.error;arith.factor
clrmed Clrmed Median color of all PS1 photometric calibrators used from science image processing: for filter (fid) = 1, 2, 3, PS1 color used = g-r, g-r, r-i respectively N/A stat.median
clrrms Clrrms RMS color (deviation from average) of all PS1 photometric calibrators used from science image processing N/A stat.stdev
created_date Created_date Date record was created N/A time.creation
dsnrms Dsnrms Ratio: D/stddev(D) on event position where D = difference image N/A stat.stdev
exptime Exptime Integration time of camera exposure s time.duration;obs.exposure
fwhm Fwhm Full Width Half Maximum assuming a Gaussian core, from SExtractor pix instr.obsty.seeing
magzpsci Magzpsci Magnitude zero point for photometry estimates mag phot.calib
magzpscirms Magzpscirms RMS (deviation from average) in all differences between instrumental photometry and matched photometric calibrators from science image processing mag stat.stdev;phot.calib
magzpsciunc Magzpsciunc Magnitude zero point uncertainty (in magzpsci) mag stat.error;phot.calib
measurement_id Measurement_id Unique identifier for the subtraction candidate N/A meta.id
mindtoedge Mindtoedge Distance to nearest edge in image pix phys.angSize
nbad Nbad Number of prior-tagged bad pixels in a 5 x 5 pixel stamp N/A meta.number
nmatches Nmatches Number of PS1 photometric calibrators used to calibrate science image from science image processing N/A meta.number
nneg Nneg Number of negative pixels in a 5 x 5 pixel stamp N/A meta.number
oid Oid Unique identifier for this object N/A meta.id;src
scorr Scorr Peak-pixel signal-to-noise ratio in point source matched-filtered detection image N/A stat.correlation
seeratio Seeratio Ratio: difffwhm / fwhm N/A stat.fit.goodness
sky Sky Local sky background estimate [DN] N/A instr.skyLevel
ssnrms Ssnrms Ratio: S/stddev(S) on event position where S = image of convolution: D (x) PSF(D) N/A stat.stdev
sumrat Sumrat Ratio: sum(pixels) / sum(abs(pixels)) in a 5 x 5 pixel stamp where stamp is first median-filtered to mitigate outliers N/A arith.ratio
xpos Xpos X-image position of candidate on CCD pix pos.cartesian.x
ypos Ypos Y-image position of candidate on CCD pix pos.cartesian.y
zpclrcov Zpclrcov Covariance in magzpsci and clrcoeff from science image processing [mag^2] N/A stat.covariance
zpmed Zpmed Magnitude zero point from median of all differences between instrumental photometry and matched photometric calibrators from science image processing mag phot.calib;stat.median

Columns that are parts of indices are marked like this.

VOResource

VO nerds may sometimes need VOResource XML for this table.