E. O. Ofek, R. Laher, N. Law, J. Surace, D. Levitan, B. Sesar, A. Horesh, D. Poznanski, J. C. van Eyken, S. R. Kulkarni, P. Nugent, J. Zolkower, R. Walters, M. Sullivan, M. Agueros, L. Bildsten, J. Bloom, S. B. Cenko, A. Gal-Yam, C. Grillmair, G. Helou, M. M. Kasliwal, R. Quimby
The Palomar Transient Factory (PTF) provides multiple epoch imaging for a
large fraction of the sky. Here we describe the photometric calibration of the
PTF data products that relates the PTF magnitudes to other mag systems. The
calibration process utilizes SDSS r~16 mag point source objects as photometric
standards. During photometric conditions, this allows us to solve for the
extinction coefficients and color terms, and to estimate the camera
illumination correction. This also enables the calibration of fields that are
outside the SDSS footprint. We test the precision and repeatability of the PTF
photometric calibration. Given that PTF is observing in a single filter each
night, we define a PTF calibrated magnitude system for R-band and g-band. We
show that, in this system, 59% (47%) of the photometrically calibrated PTF
R-band (g-band) data achieve a photometric precision of 0.02-0.04 mag. Given
the objects' color, the PTF magnitude system can be converted to other systems.
A night-by-night comparison of the calibrated magnitudes of individual stars
observed on multiple nights shows that they are consistent to a level of ~0.02
mag. Most of the data that were taken under non-photometric conditions can be
calibrated relative to other epochs of the same sky footprint obtained during
photometric conditions. We provide a guide describing the use of the PTF
photometric calibration data products, as well as the transformations between
the PTF magnitude system and the SDSS and Johnson-Cousins systems. (abridged).
View original:
http://arxiv.org/abs/1112.4851
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