Chandra crossmatch lab


Let's continue studying Abell 2065.

Abell 2065
RA
Dec
Sexegesimal
15:22:42.6
+27:43:21
Degrees
230.6776
+27.7226
(these are rough coordinates -- you worked out better ones last week from the SDSS imaging.)

We worked out how to make a color magnitude diagram from SDSS data, and make qualitative judgements of the likelihood of cluster membership based on a galaxies position on that diagram. So now let's take a look at the Chandra catalog to see if there are any X-ray sources in the cluster.

Go to the Chandra/SDSS Cross-Match catalog here:
http://cxc.cfa.harvard.edu/cgi-gen/cda/CSC-SDSSxmatch.html

(General information on the Chandra Source Catalog is here.)

This site takes the Chandra point source catalog and matches it up with the SDSS source catalog, just what we want. Ask the crossmatch catalog to search for sources within 40' or so of the cluster center, giving you information on the following:

MSID
Chandra ID
OBJID
SDSS ID
SDSS_TYPE
sdss classification
3=galaxy, 6=star
SEPARATION
X-Opt in arcsec
PROBABILITY
of match
RA_SDSS, DEC_SDSS
position
G, ERR_G
g mag
R, ERR_R
r mag
SIGNIFICANCE
X-ray detection significance
ERR_ELLIPSE_R0
X-ray pos uncertainty
FLUX_APER90_B etc X-ray flux
HARD_HS X-ray hardness

Ask for a fixed width format for the output file and save it to your computer as a text file. We need to get it into a better format for reading, so open the file in a text editor and do the following:
Now you should be able to read the file by saying:

from astropy.io import ascii
chandradata=ascii.read(filename,header_start=-3,data_start=0)

And then access the data by saying, for example:

gc=chandradata['G']
rc=
chandradata['R']
etc

Make the following plots to work out if the following parameters make sense:
Now load your SDSS data and remake the cluster color magnitude plot (g-r versus r), showing the red sequence, etc. Overplot on top of this the g-r and r SDSS photometry for the Chandra detected sources.  Have we detected any cluster AGN?

Now go back to SDSS skyserver's Navigate interface and put in the coordinates for some of your candidate cluster AGN. See what you can learn about them. What do they look like? Do they have spectra? Do they have redshifts? If they are part of the cluster, how far from the cluster center are they -- are they in the core? the outskirts? Is there any ancillary information on them from other sources (Once you have an object up in Explorer, try hitting "NED search", for example)?