J/MNRAS/491/5317 The SDSS extended PSFs (Infante-Sainz+, 2020)
The Sloan Digital Sky Survey extended point spread functions.
Infante-Sainz R., Trujillo I., Roman J.
<Mon. Not. R. Astron. Soc. 491, 5317 (2020)>
=2020MNRAS.491.5317I 2020MNRAS.491.5317I (SIMBAD/NED BibCode)
ADC_Keywords: Combined data ; Galaxies, photometry ; Photometry, SDSS ;
Photometry, ugriz ; Stars, bright
Keywords: instrumentation: detectors - methods: data analysis -
techniques: image processing - techniques: photometric -
galaxies: haloes
Abstract:
A robust and extended characterization of the Point Spread Function
(PSF) is crucial to extract the photometric information produced by
deep imaging surveys. Here we present the extended PSFs of the Sloan
Digital Sky Survey (SDSS), one of the most productive astronomical
surveys of all time. By stacking ∼1000 images of individual stars with
different brightness, we obtain the bidimensional SDSS PSFs extending
over 8 arcmin in radius for all the SDSS filters (u, g, r, i, z). This
new characterization of the SDSS PSFs is near a factor of 10 larger in
extension than previous PSFs characterizations of the same survey. We
found asymmetries in the shape of the PSFs caused by the drift
scanning observing mode. The flux of the PSFs is larger along the
drift scanning direction. Following a reproducible science philosophy,
we make all the PSF models and the used tools publicly available.
Finally, we illustrate with an example how the PSF models can be used
to remove the scattered light field produced by the brightest stars in
the Coma Cluster central region. This particular example shows the
huge importance of PSFs in the study of the low surface brightness
Universe, especially with the upcoming of ultra-deep surveys such as
the Large Synoptic Survey Telescope (LSST).
Description:
These are the SDSS extended PSF which have been created by Raul
Infante-Sainz and colaborators at the Instituto de Astrofisica de
Canarias (IAC): http://research.iac.es/proyecto/stripe82/ Git
repository of this project can be found at
https://gitlab.com/infantesainz/sdss-psf-paper
They are 5 PSFs images in fits format, one per each SDSS filter (u, g,
r, i, z). The PSFs models can be used to remove the scattered light of
point-like sources as described in Sect. 3.2 of the paper. In addition
to this, the PSFs can be also used to model galaxies and other
astronomical objects with the goal of correcting the scattered light
of the object itself (for example using astronomical software like
Imfit or GALFIT).
IMPORTANT NOTE: all the PSFs present asymmetries in their shape (i.e.
they are not circulary symmetric). As a consequence, they must to be
rotated according to each particular field of the sky in order to
match the drift scanning direction of the PSFs (which goes from left
to right) with the orientation of the SDSS object image.
Each fits file contains 2 extensions
-----
Column 1: Index
Column 2: Extension Name
Column 3: Image data type
Column 4: Size of data in HDU
-----
0 n/a no-data 0
1 n/a float32 2425x2425
The detailed description of the methods used for the creation of these
dedicated extended PSFs is fully available in the paper.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 67 10 List of fits PSF images
fits/* . 10 Individual fits PSF images
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 I4 --- Nx Number of pixels along X-axis
6- 9 I4 --- Ny Number of pixels along Y-axis
11- 15 I5 Kibyte size Size of FITS file
17- 38 A22 --- FileName Name of FITS file, in subdirectory fits
40- 67 A28 --- Title Title of the FITS file
--------------------------------------------------------------------------------
Acknowledgements:
Raul Infante-Sainz, infantesainz(at)gmail.com
(End) Raul Infante-Sainz [IAC], Patricia Vannier [CDS] 31-Oct-2019