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COSMOS MAGELLAN Data                                            Version 3.1
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The Cosmic Evolution Survey (COSMOS) is an HST Treasury Project to survey
a 2 square degree equatorial field, centered on RA=10:00:28.6 and
DEC=+02:12:21.0, using the ACS camera. The project also incorporates major
commitments from other observatories around the world.

These data represent some of the first spectra of objects in the COSMOS
field, obtained with the IMACS instrument on the Magellan telescope.
Included in this release are optical spectra of some 678 targets.

The key characteristics of these data:

	Telescope:		Magellan (Baade)
	Instrument:		Inamori Magellan Areal Camera (IMACS) 
	Dates of observations:	January - May, 2005-2007
	Filter:           OG570 (Jan-Feb, year 1), 565-920 (all others)
      Disperser:        200 l/mm grism (year 1), 150 l/mm grism (year 2,3)
	Bandwidth:	      5600-9200 Angstroms
	Objects:	      678
	Area:             ~2 sq deg
	Resolution:       0.200 x 0.999 arcsec/pixel
	Dispersion:       10.00000 [Angstrom/resolution element]

The data products available here include the following for each spectrum:

	(1) flux-calibrated FITS spectrum [".fits" file]
	(2) flux-calibrated ASCII spectrum [".tbl" file]

	    Both of these spectra have 4 columns:

	    wl - wavelength, in Angstroms
	    fl - flux, in units of erg/s/cm^2/Ang
	    flerr - 1 sigma error in the flux
	    mask - pixel mask, 1=good, 0=bad

	(3) flux-calibrated spectrum previews [".jpg" file]

In addition, there is a supplementary file with details for each object:

    http://irsa.ipac.caltech.edu/data/COSMOS_INT/tables/magellan_opt_spec_30.tbl

The supplementary file contains the same relevant details as in the FITS 
file header keywords for the individual spectra, including:

column   column name      
  1        'Object_Name' - COSMOS designation (of form 'hhmmss+ddmmss')    
  2        'ra'   - J(2000) coordinates
  3        'dec'  - J(2000) coordinates
  4        'imag' - i(AB) magnitude, from CFHT    
  5        'SN' - signal-to-noise per pixel    
  6        'expi' - exposure time from IMACS observations
  7        'expm' - exposure time from supplemental MMT/Hectospec observations
  8        'class' - classification, can have the following values:    
                    'bl': broad emission lines (Type 1 AGN)    
                    'nl': narrow emission lines (Type 2 AGN or emission line galaxy)    
                    'a': no emission lines, red galaxy-type spectrum (obscured AGN)    
                    'nla': red galaxy continuum with absorption and strong emission lines    
                    'star': star    
                    '?': unknown    
  9        'redshift' - redshift, -1 if redshift is unknown (zconf=0,-1)    
 10        'z_err' - redshift error, determined using idlspec2d or manually    
 11        'z_conf' - redshift confidence, can have the following values:    
                     4: high-confidence redshift (>90% likely)
                     3: likely redshift (~75% likely)
                     2: degenerate redshift (~50% likely)
                     1: redshift guess (~25% likely)
                     0: unknown redshift    
                    -1: spectrum corrupted by artifacts
 12        'field' - field of observation: the 2nd character refers to the year observed
                     (i1: 2005, i2: 2006, i3: 2007)

The files follow a standard naming scheme where, for example:

        magellan_opt_100058+021139_spec_31.fits

refers to a Magellan optical spectrum, centered at RA=10:00:58 and
DEC=+02:11:39, version 3.1. Both FITS spectra (".fits" suffix) and ascii
tables (".tbl" suffix) are provided.  IRSA has created JPG previews for
each spectra, with suffix ".jpg".  Please note that the spectral previews
show only data points with mask=1 from the spectrum data files.

The paper describing the observations is posted here:

    http://adsabs.harvard.edu/abs/2008arXiv0811.3977T

And more information is available from the main COSMOS web page:

    http://cosmos.astro.caltech.edu/

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v3.1: Fixed CRVAL1 header values, which had the incorrect zero
      wavelength values for about ~30 spectra.

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The COSMOS Team, Patrick Shopbell (Archive Lead), Jonathan Trump, and
  Anastasia Alexov
pls@astro.caltech.edu, jtrump@as.arizona.edu, aalexov@ipac.caltech.edu

July 3, 2009