===========================================================================
COSMOS Chandra Data   (X-ray band)                              Version 2.0
===========================================================================

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, including the VLA radio telescope, ESO's
VLT in Chile, ESA's XMM X-ray satellite, NASA's Chandra X-ray Observatory and
the Japanese 8-meter Subaru telescope in Hawaii.

These data represent the first public release of the COSMOS observations from
the ACIS instrument on Chandra. Included in this release are Chandra standard
data products from the archive and subsequent derived products that are
required in X-ray image and spectral data analysis.

The key characteristics of these data:

	Instrument:		Chandra ACIS-I
	Dates of observations:	(Nov 2006 - Jun 2007)
	Observing time:		1.8 Msec
	Energy band:		0.5 - 7 keV
	Area:			0.9 sq deg
	Resolution:		0.5"/pixel

These data were reduced primarily by Tom Aldcroft (taldcroft@cfa.harvard.edu)
using the CIAO software tools (http://cxc.harvard.edu/ciao/) and a
fully-automated reduction pipeline implemented with yaxx
(http://cxc.harvard.edu/contrib/yaxx/).  Nico Cappelluti and Antonella
Fruscione also made significant contributions.

The data products are organized hierarchically for each Chandra observation 
and include:

	(1) X-ray event files (custom processed with fine astrometry corrections)
        (2) Exposure maps for each CCD and X-ray band (full, soft, hard)
        (3) Supporting data products (bad pixel, aspect solution, etc)
        (4) Celldetect and wavedetect source lists (per-CCD)
        (5) Source and background extraction region files

The files follow a standard naming scheme:

File type             Description                            File name
-----------------     ------------------------------------   -------------------------
obs_dir               Directory for observation obsid        obs<obsid>/
obs_asol              Corrected aspect solution file         obs<obsid>/asol1.fits
obs_uncor_asol        Original asol file (SDP level-1)       obs<obsid>/uncor_asol1.fits
obs_evt1              Event file (SDP level-1)               obs<obsid>/acis_evt1.fits
obs_evt2              Level-2 event file                     obs<obsid>/acis_evt2.fits
obs_pbk0              Parameter block file (SDP level-0)     obs<obsid>/acis_pbk0.fits
obs_bias0             Bias map (SDP level-0)                 obs<obsid>/acis_bias0.fits
obs_fov1              Field of view file (SDP level-1)       obs<obsid>/acis_fov1.fits
obs_msk1              Instrument mask file (SDP level-1)     obs<obsid>/acis_msk1.fits
obs_mtl1              Mission timeline file (SDP level-1)    obs<obsid>/acis_mtl1.fits
obs_flt1              Good time interval file (SDP level-1)  obs<obsid>/acis_flt1.fits
obs_bpix1             Bad pixel file (SDP level-1)           obs<obsid>/acis_bpix1.fits
obs_src2              Celldetect source list (SDP level-2)   obs<obsid>/acis_src2.fits
obs_img               JPEG image of obs_evt (0.5-7 keV)      obs<obsid>/acis_img.fits
obs_acisi_img         FITS image of ACIS-I (0.5-7 keV)       obs<obsid>/obs<obsid>acis_0123_img.fits
obs_acisi_img         JPEG image of ACIS-I (0.5-7 keV)       obs<obsid>/obs<obsid>acis_0123_img.jpg
obs_celldet_filt_src  Source list from celldetect            obs<obsid>/celldet_filt_src.fits
obs_asphist           Aspect histogram for obsid             obs<obsid>/asphist.fits
ccd_dir               Directory for one band of one CCD      obs<obsid>/ccd<ccd>/<band>
ccd_img               JPEG image for CCD (0.5-7 keV)         obs<obsid>/ccd<ccd>/<band>/acis_img.fits
ccd_evt               Events for one band of one CCD         obs<obsid>/ccd<ccd>/<band>/acis_evt2.fits
ccd_instmap           Instrument map (one CCD band)          obs<obsid>/ccd<ccd>/<band>/instmap.fits
ccd_expmap            Exposure map (one CCD band)            obs<obsid>/ccd<ccd>/<band>/expmap.fits
celldet_src           Celldetect source list (one CCD band)  obs<obsid>/ccd<ccd>/<band>/celldet_src.fits
celldet_filt_src      Celldetect source list (filtered)      obs<obsid>/ccd<ccd>/<band>/celldet_filt_src.fits
wavdet_src            Wavdetect source list (one CCD band)   obs<obsid>/ccd<ccd>/<band>/wavdet_src.fits
wavdet_scell          Wavdetect source cells (one CCD band)  obs<obsid>/ccd<ccd>/<band>/wavdet_scell.fits
wavdet_imgfile        Wavdetect source image (one CCD band)  obs<obsid>/ccd<ccd>/<band>/wavdet_imgfile.fits
wavdet_nbkg           Wavdetect background (one CCD band)    obs<obsid>/ccd<ccd>/<band>/wavdet_nbkg.fits
src_dir               Directory for one detected source      obs<obsid>/ccd<ccd>/<band>/src<srcid>
src_img               JPEG image of source evts (0.5-7 keV)  obs<obsid>/ccd<ccd>/<band>/src<srcid>/acis_img.fits
src_reg               Source extraction region               obs<obsid>/ccd<ccd>/<band>/src<srcid>/src.reg
bkg_reg               Background region                      obs<obsid>/ccd<ccd>/<band>/src<srcid>/bkg.reg

Further information may be obtained from the main COSMOS web page:

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

and the Chandra-COSMOS web page:

	http://chandracosmos.cfa.harvard.edu/

===========================================================================
The COSMOS Team, Patrick Shopbell (Archive Lead), and Tom Aldcroft
pls@astro.caltech.edu, taldcroft@cfa.harvard.edu

July 22, 2008