Chandra Deep Field South
========================

The Chandra Deep Field South is centered on:
  RA(ICRS) = 03 32 28.2  Dec(ICRS) = -27 48 36


We have combined 12 CDF-S observations (ObsId = 8591, 8592, 8593,
8594, 8595, 8596, 8597, 9578, 9593, 9596, 9718, 9575) taken during
Sep. - Nov. 2007. Total exposure: 980 ks.
We cleaned ACIS background events in level 1 processing (by setting
check_vf_pha=yes in acis_process_events to utilize a 5x5 pixel event
island available in VFAINT mode), and refined astrometry based on the
matched source positions and reprojected onto a  common tangent plane
(using a CIAO tool, reproject_aspect).
The relative offsets  (from obsid 9575) for individual observations
are listed below for reference.


The main merged data products are:

acismCDFS_vf_N000_evt2.fits      final merged event list for ccdid=0-3
acismCDFS_vf_N000_expmap.fits    final merged exposure map 
acismCDFS_vf_N000_full_img2.fits full image in energy band 0.5-6 keV
acismCDFS_vf_N000_colorimg.jpg   true color image made with
                                   3 energy bands (0.5-1, 1-2, 2-6 keV).


We also provide the event list and aspect solution for each ObsId
so that users may merge a sub-sample (e.g,. those with similar roll
angles):

pcad_[obsid]_reproject_asol1.fits       aspect solution per observation
acism[obsid]N000_reproj_vf_evt2.fits    Level 2 event list per observation



 Table 1. Relative positional offsets of individual observations

+------+-----------+-----------+-----------+--------------------------+
|      |  Rotation |  X Transl |  Y Transl |                          |
|Obsid | Angle deg | in pixels | in pixels | date-obs                 |
+------+-----------+-----------+-----------+--------------------------+
| 8591 | -0.002689 | -0.190693 |  0.273417 | Sep 20 2007              |
| 9593 | -0.005447 |  0.016670 |  0.509791 | Sep 22 2007              |
| 9718 | -0.004962 |  0.111269 |  0.188725 | Oct  3 2007              |
| 8593 | -0.001654 |  0.420111 |  0.054327 | Oct  6 2007              |
| 8597 |  0.000681 |  0.046893 |  0.423655 | Oct 17 2007              |
| 8595 |  0.012526 |  0.251524 |  0.594546 | Oct 19 2007              |
| 9575 | -0.000000 |  0.000000 |  0.000000 | Oct 27 2007 ** reference |
| 8592 | -0.013634 | -0.203369 |  0.199928 | Oct 22 2007              |
| 8596 |  0.016394 | -0.146683 |  0.222187 | Oct 24 2007              |
| 9578 | -0.005973 |  0.057269 | -0.550306 | Oct 30 2007              |
| 8594 | -0.006194 | -0.064804 |  0.297714 | Nov  1 2007              |
| 9596 |  0.017150 |  0.034316 |  0.147677 | Nov  4 2007              |
+------+-----------+-----------+-----------+--------------------------+

(1 pixel = 0.492 arcsec)

The aspect solution and offset (by reproject_aspect) are the same as 
we used for the previous set of merged data at:
  ftp://cda.harvard.edu/pub/arcftp/cdfs2000-2007/
  ftp://cda.harvard.edu/pub/arcftp/cdfs2007/


 Table 2. Dates, exposure times, and roll angles of individual observations

+-----+-------------+--------+-----+
|      |             |Exposure| Roll|     
|Obsid | date-obs    |  (ks)  |(deg)|
+------+-------------+--------+-----+
| 8591 | 20 Sep 2007 |   46   |  73 |
| 9593 | 22 Sep 2007 |   47   |  73 |
| 9718 |  3 Oct 2007 |   50   |  62 |
| 8593 |  6 Oct 2007 |   50   |  62 |
| 8597 | 17 Oct 2007 |   60   |  44 |
| 8595 | 19 Oct 2007 |  117   |  41 |
| 9575 | 27 Oct 2007 |  110   |  32 |
| 8592 | 22 Oct 2007 |   88   |  32 |
| 8596 | 24 Oct 2007 |  117   |  32 |
| 9578 | 30 Oct 2007 |   39   |  24 |
| 8594 |  1 Nov 2007 |  143   |  24 |
| 9596 |  4 Nov 2007 |  113   |  20 |
+------+-------------+--------+-----+
