http://sdss.physics.nyu.edu/spitzer/fls/

The Spitzer Space Telescope (or SIRTF) First-Look Survey (FLS): Visual data from the Sloan Digital Sky Survey (SDSS)

Michael R. Blanton^a / Douglas P. Finkbeiner^b / David W. Hogg^a / Nikhil Padmanabhan^c / David J. Schlegel^b

^a Center for Cosmology and Particle Physics, New York University
^b Princeton University Observatory, Princeton University
^c Department of Physics, Princeton University

SDSS Image mosaics

We have assembled all SDSS imaging in the Spitzer Extragalactic FLS field into four giant mosaics in each of five visual bands. These mosaics have the following properties:

5-band ugriz visual image mosaics composed of hundreds of SDSS drift-scan fields
sets of four 1.75 deg × 1.25 deg mosaics, north-up
each mosaic is 15912×11364
0.396 arcsec × 0.396 arcsec square pixels (at fiducial point RA=259.5 deg, Dec=59.5 deg J2000)
correct, FITS-compliant WCS astrometry headers
the four mosaics “snap together” into one immense (31824×22728) mosaic with no overlaps or edge distortion issues
calibrated in intensity units of [nMgy (0.396 arcsec)^-2], where 1 nMgy (“nano maggy”) in flux is equivalent to 22.5 mag (AB system)

NB: If a source in one of the mosaics is measured to have total flux N in nMgy, its magnitude m is then

m = [22.5 mag] − 2.5 log₁₀ N .

The above files are unwieldy, so we have made some lower-resolution, single-field mosaics with the following properties:

same 5 bands
individual 3.5 deg × 2.5 deg mosaics, north-up
each mosaic is 10608×7576
1.188 arcsec × 1.188 arcsec square pixels (at fiducial point RA=259.5 deg, Dec=59.5 deg J2000)
correct, FITS-compliant WCS astrometry headers
calibrated in intensity units of [nMgy (1.188 arcsec)^-2]

NB: Unlike the high resolution images, these lower-resolution images are not band-limited and should be used with caution.

There are some defects in these mosaics, which need to be worked out, worked around, or avoided by scientific users:

sky noise variance is not constant but varies inversely with the number of overlapping SDSS fields (1 or 2 for most of the image area); in particular there are diagonal “stripes” of low noise in the images where SDSS camera columns overlap
sky background level is not exactly zero everywhere; use local sky estimation when photometering sources
bright stars are saturated and have bleed trails
the PSF is variable across the fields
filter reflections in the SDSS cameras cause bright stars to show nearby flares in sky brightness
some cosmic rays have slipped through
small CCD readout defects near extremely bright sources
many bright single-band satellite trails

SDSS Photometric Catalog

Obtain photometric catalog information from SDSS Data Release 1.

SDSS Spectroscopy

We have also assembled all SDSS spectroscopy in the FLS region into a pair of FITS files:

one FITS file containing all of the Spitzer FLS region SDSS spectra and their observational uncertainties on a common wavelength grid, with common calibration
one FITS binary table file containing the positions of the spectroscopic sources and all of the parameters derived from the SDSS spectra by the Princeton pipelines

Essentially everything a user needs to know about the format and contents of these files, including calibration, is available at the Princeton/MIT SDSS Spectroscopy page.

Version information

These data are assembled, calibrated, mosaiced, and arranged by a set of IDL (6.0) and C code in four CVS modules at Princeton and NYU. The current version of the downloadable data is:

version v1_0_2

The current version was created with the following tag versions of the following CVS modules:

module name	CVS tag	location
`sirtf`	`v1_0_2`	NYU
`photoop`	`v1_1_3`	Princeton
`idlspec2d`	`v4_10_7`	Princeton
`idlutils`	`v4_10_8`	Princeton

Obtaining the data

The mosaics and JPGs can all be individually downloaded from this WWW page (below), or else you can run the following auto-download command if you have wget. Make sure you download only inside a working directory in which you have about 25 Gb free space. The wget command puts everything in a directory structure below your working directory.

wget -N -r -nH http://sdss.physics.nyu.edu/spitzer/

Please be considerate of NYU bandwidth by trying to run downloads late at night, New York time.

Conditions of use

Any use of these data must be accompanied by citation of the following papers:

Hogg, D. W., Blanton, M. R., Finkbeiner, D. P., Padmanabhan, N., & Schlegel, D. J., “The Spitzer Space Telescope First Look Survey: Visual data from the Sloan Digital Sky Survey,” in preparation.
Abazajian, K. et al, “The second data release of the Sloan Digital Sky Survey,” AJ, in press (astro-ph/0403325).

All users of these data products must send email to david.hogg@nyu.edu to register. This lets us maintain an email list of users for updates and notifications.

Data

low-resolution SDSS mosaic of the full field: center of mosaic at fiducial point (RA=259.5 deg, Dec=59.5 deg, J2000); 1.188 arcsec × 1.188 arcsec square pixels at fiducial point; calibrated in intensity units of [nMgy (1.188 arcsec)^-2] (see above); u-band mosaic — 10608×7576 FITS file (307 Mb); g-band mosaic — 10608×7576 FITS file (307 Mb); r-band mosaic — 10608×7576 FITS file (307 Mb); i-band mosaic — 10608×7576 FITS file (307 Mb); z-band mosaic — 10608×7576 FITS file (307 Mb); gri color composite — 5304×3788 JPG (binned 2×2) (4 Mb)
full-resolution SDSS mosaic 0 — NW quadrant: lower-left corner at fiducial point; 0.396 arcsec × 0.396 arcsec square pixels at fiducial point; calibrated in intensity units of [nMgy (0.396 arcsec)^-2] (see above); u-band mosaic — 15912×11364 FITS file (690 Mb); g-band mosaic — 15912×11364 FITS file (690 Mb); r-band mosaic — 15912×11364 FITS file (690 Mb); i-band mosaic — 15912×11364 FITS file (690 Mb); z-band mosaic — 15912×11364 FITS file (690 Mb); gri color composite — 7956×5682 JPG (binned 2×2) (12 Mb)
full-resolution SDSS mosaic 1 — NE quadrant: lower-right corner at fiducial point; same pixel scale (at fiducial point) and calibration as mosaic 0; u-band mosaic — 15912×11364 FITS file (690 Mb); g-band mosaic — 15912×11364 FITS file (690 Mb); r-band mosaic — 15912×11364 FITS file (690 Mb); i-band mosaic — 15912×11364 FITS file (690 Mb); z-band mosaic — 15912×11364 FITS file (690 Mb); gri color composite — 7956×5682 JPG (binned 2×2) (12 Mb)
full-resolution SDSS mosaic 2 — SE quadrant: upper-right corner at fiducial point; same pixel scale (at fiducial point) and calibration as mosaic 0; u-band mosaic — 15912×11364 FITS file (690 Mb); g-band mosaic — 15912×11364 FITS file (690 Mb); r-band mosaic — 15912×11364 FITS file (690 Mb); i-band mosaic — 15912×11364 FITS file (690 Mb); z-band mosaic — 15912×11364 FITS file (690 Mb); gri color composite — 7956×5682 JPG (binned 2×2) (12 Mb)
full-resolution SDSS mosaic 3 — SW quadrant: upper-left corner at fiducial point; same pixel scale (at fiducial point) and calibration as mosaic 0; u-band mosaic — 15912×11364 FITS file (690 Mb); g-band mosaic — 15912×11364 FITS file (690 Mb); r-band mosaic — 15912×11364 FITS file (690 Mb); i-band mosaic — 15912×11364 FITS file (690 Mb); z-band mosaic — 15912×11364 FITS file (690 Mb); gri color composite — 7956×5682 JPG (binned 2×2) (12 Mb)
SDSS spectroscopic data files: formats and calibration explained in the “data model” section of the Princeton/MIT SDSS Spectroscopy page; all FLS spectra, spPlate format, gzipped FITS file (46 Mb); all derived spectroscopic quantitied, spZbest format, gzipped FITS binary table (<1 Mb)

Acknowledgements

It is a pleasure to thank Tom Soifer, Lisa Storrie-Lombardi, and the entire Spitzer Team for beginning the mission with the generous First Look Survey. We also thank Aaron Barth, Scott Burles, Jim Gunn, Wayne Landsman, Robert Lupton and Uros Seljak for very useful software and discussions.

This results presented on this WWW page were obtained with generous support from NASA (grant NAG5-11669) and NSF (grant PHY-0101738). The opinions presented on this page do not represent those of either NASA or NSF.

Funding for the creation and distribution of the SDSS Archive has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Aeronautics and Space Administration, the National Science Foundation, the U.S. Department of Energy, the Japanese Monbukagakusho, and the Max Planck Society. The SDSS Web site is http://www.sdss.org/.

The SDSS is managed by the Astrophysical Research Consortium (ARC) for the Participating Institutions. The Participating Institutions are The University of Chicago, Fermilab, the Institute for Advanced Study, the Japan Participation Group, The Johns Hopkins University, Los Alamos National Laboratory, the Max-Planck-Institute for Astronomy (MPIA), the Max-Planck-Institute for Astrophysics (MPA), New Mexico State University, University of Pittsburgh, Princeton University, the United States Naval Observatory, and the University of Washington.

Hogg / david.hogg@nyu.edu