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

Abstract

The Zwicky Transient Facility (ZTF) is a new robotic time-domain survey\ncurrently in progress using the Palomar 48-inch Schmidt Telescope. ZTF uses a\n47 square degree field with a 600 megapixel camera to scan the entire northern\nvisible sky at rates of ~3760 square degrees/hour to median depths of g ~ 20.8\nand r ~ 20.6 mag (AB, 5sigma in 30 sec). We describe the Science Data System\nthat is housed at IPAC, Caltech. This comprises the data-processing pipelines,\nalert production system, data archive, and user interfaces for accessing and\nanalyzing the products. The realtime pipeline employs a novel\nimage-differencing algorithm, optimized for the detection of point source\ntransient events. These events are vetted for reliability using a\nmachine-learned classifier and combined with contextual information to generate\ndata-rich alert packets. The packets become available for distribution\ntypically within 13 minutes (95th percentile) of observation. Detected events\nare also linked to generate candidate moving-object tracks using a novel\nalgorithm. Objects that move fast enough to streak in the individual exposures\nare also extracted and vetted. The reconstructed astrometric accuracy per\nscience image with respect to Gaia is typically 45 to 85 milliarcsec. This is\nthe RMS per axis on the sky for sources extracted with photometric S/N >= 10.\nThe derived photometric precision (repeatability) at bright unsaturated fluxes\nvaries between 8 and 25 millimag. Photometric calibration accuracy with respect\nto Pan-STARRS1 is generally better than 2%. The products support a broad range\nof scientific applications: fast and young supernovae, rare flux transients,\nvariable stars, eclipsing binaries, variability from active galactic nuclei,\ncounterparts to gravitational wave sources, a more complete census of Type Ia\nsupernovae, and Solar System objects.\n

Keywords

Affiliated Institutions

• University of Maryland, College Park US
• Adler Planetarium US
• National Central University TW
• Northwestern University US
• Jet Propulsion Laboratory US
• Deleted Institution
• California Institute of Technology US
• Carnegie Observatories US
• City University of Seattle US
• University of Michigan US
• University of Wisconsin–Milwaukee US
• University of California, Santa Barbara US
• Infrared Processing and Analysis Center US
• University of Washington US
• Goddard Space Flight Center US
• Weizmann Institute of Science IL

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