===================================================
SSGSS Data Release                                              Version 1.0
===================================================

The Spitzer SDSS Galaxy Spectroscopic Survey (SSGSS) is a Cycle-3 
Spitzer program to acquire 5 to 40 micron mid-infrared spectroscopy 
of a representative sample of galaxies from SDSS, selected for having
full prior photometric coverage from the UV to the far-IR.  

The full SSGSS sample includes 101 star forming galaxies from the
SWIRE/Lockman Hole region. These galaxies were selected from those
with full SDSS, GALEX and IRAC (4 channel) and MIPS (24 and 70 micron)
photometry, with a 5.8 micron surface brightness limit of 0.75 MJy/sr
and a 24 micron flux limit of 1.5 mJy.

These data represent the first public data release of the full SSGSS
sample. The dataset includes short-low and long-low IRS spectroscopy
for the full sample, and short-high IRS spectroscopy for a subsample
of the 33 brightest galaxies.

The characteristics of these data are:

Instrument: IRS
Modules: SL1, SL2, LL1, LL2, SH
Resolution:
     Low Res: R~57-127
     Hi Res: R~600
Exposure time per pointing: 
     Low Res: 487.6 sec
     Hi Res: 975.17 sec
Observation dates:
     Low Res: 12-10-2006 to 12-17-2006
     Hi Res: 11-18-2006, 10-12-2006, and 11-12-2006


The file sets are named as follows:

1. SSGSS_[#]_[SL/LL]_[A/B]_[1 to 4].fits
     The uncombined short-low (SL) or long-low (LL) spectra for galaxy
     number [#], in the SL2/LL2 (A) or SL1/LL1 (B) order, for slit
     positions 1 to 4. 

2. SSGSS_[#]_[SL/LL]_[A/B]_Comb.fits
     The combined short-low (SL) or long-low (LL) spectrum for galaxy
     number [#], in the SL2/LL2 (A) or SL1/LL1 (B) order. 

3. SSGSS_[#]_[SL/LL].fits
     The combined short-low (SL) or long-low (LL) spectrum for galaxy
     number [#], with the two orders concatenated. 

4. SSGSS_[#]_SL-LL.fits
     The concatenated short-low and long-low spectrum for galaxy
     number [#]. 

5. SSGSS_[#]_lores.fits
     The concatenated short-low and long-low spectrum for galaxy
     number [#]. Order overlap regions are combined by weighted mean
     and channel overlap regions are combined by either a cut or
     weighted mean.  

6. SSGSS_[#]_SH.fits
     The short-high spectrum for galaxy number [#]. Order overlap
     regions are not combined 

7. SSGSS_[#]_hires.fits
     The short-high spectrum for galaxy number [ID]. Order overlap
     regions are combined by weighted mean. 


The spectra are stored in fits format and contain structures with
the following tags: 

WAVE (all file sets):
     Wavelength in micrometers

FLUX (all file sets):
     Flux in Janskys

ERROR (all file sets):
     Error in the flux 

ORDER (all file sets):
     Order number

BITFLAG (all file sets):
     Bit-flags generated by SPICE. In the case of combined files (all
     but file set 1), the bit flag of the first position is used 

ORDERFLAG (file sets 1, 2, 3, 4, 6):
     1 for regions in which order overlap occurs, 0 otherwise.

CHANNELFLAG (file set 5):
     Set to 1, 2, 3, or 4 for channels: short-low right, short-low
     left, long-low right, and long-low left respectively. For channel
     overlap regions combined by weighted mean, CHANNELFLAG is set to 
     the mean of the two flags. For example, the long-low right and
     long-low level combined overlap region is set to 3.5.

Note: ORDER appears after BITFLAG in spectra from file set 1.

These data and the SSGSS project in general are described in full in:
     Schiminovich, D. et al. (2008), in prep

Further information may also be found at the SSGSS home page:
     http://astro.columbia.edu/ssgss

Additional information on the data reduction process, including
definition of BITFLAG values can be found in the SPICE GUI help tool: 
     http://ssc.spitzer.caltech.edu/postbcd/spice.html

===================================================
SSGSS team contacts: David Schiminovich, Ben Johnson, Matt O'Dowd
ds@astro.columbia.edu, bjohnson@astro.columbia.edu, matt@astro.columbia.edu

April 2008

Edited by J. Howell, IRSA, January 2009
change log: standard terminology for IRS orders, added ORDER to list of 
columns, added note that ORDER and BITFLAG columns are in reverse order 
in one file set.