The Zwicky Transient Facility: Data Processing, Products, and Archive

Abstract

The Zwicky Transient Facility (ZTF) is a new robotic time-domain survey currently in progress using the Palomar 48-inch Schmidt Telescope. ZTF uses a 47 square degree field with a 600 megapixel camera to scan the entire northern visible sky at rates of ∼3760 square degrees/hour to median depths of g∼20.8 and r∼20.6 mag (AB, 5σ in 30 sec). We describe the Science Data System that is housed at IPAC, Caltech. This comprises the data-processing pipelines, alert production system, data archive, and user interfaces for accessing and analyzing the products. The real-time pipeline employs a novel image-differencing algorithm, optimized for the detection of point-source transient events. These events are vetted for reliability using a machine-learned classifier and combined with contextual information to generate data-rich alert packets. The packets become available for distribution typically within 13 minutes (95th percentile) of observation. Detected events are also linked to generate candidate moving-object tracks using a novel algorithm. Objects that move fast enough to streak in the individual exposures are also extracted and vetted. We present some preliminary results of the calibration performance delivered by the real-time pipeline. The reconstructed astrometric accuracy per science image with respect to Gaia DR1 is typically 45 to 85 milliarcsec. This is the RMS per-axis on the sky for sources extracted with photometric S/N10 and hence corresponds to the typical astrometric uncertainty down to this limit. The derived photometric precision (repeatability) at bright unsaturated fluxes varies between 8 and 25 millimag. The high end of these ranges corresponds to an airmass approaching ∼2-the limit of the public survey. Photometric calibration accuracy with respect to Pan-STARRS1 is generally better than 2%. The products support a broad range of scientific applications: fast and young supernovae; rare flux transients; variable stars; eclipsing binaries; variability from active galactic nuclei;

The First Ultracompact Roche Lobe–Filling Hot Subdwarf Binary

“…The ZTF light curves of ZTF J2130+4420 consist of 759 epochs in the ZTF-r band and 175 epochs in the ZTF-g band. Image processing and light curve extraction of ZTF data is described in detail by Masci et al (2019).…”

LAMOST J040643.69+542347.8: The Fastest Rotator in the Galaxy

“…The light curves of the star LAMOST J040643.69+542347.8 are found in the data archives of the Zwicky Transient Facility (ZTF) (Masci et al 2019) and the Wide Angle Search for Planets (WASP) (Butters et al 2010), but there are no photometric variations larger than their photometric errors. Mann & von Braun (2015).…”

Cataclysmic Variables in the First Year of the Zwicky Transient Facility

“…The Zwicky Transient Facility (ZTF) is a northern all-sky survey that uses the Palomar 48-inch telescope equipped with a 47 deg 2 field of view camera (Bellm et al 2019a,b;Graham et al 2019;Masci et al 2019). The advantages of the ZTF survey compared to past and on-going northern sky surveys are the combination of large sky coverage that includes the Galactic plane, along with color information and increased temporal coverage, and the availability of nightly alerts.…”