This is an experiment in “live blogging science” and an attempt to report on the X-ray properties of a system, which I am assuming (for now) to be a galaxy group. There are follow-up X-ray observations, by the XMM-Newton and Suzaku telescopes, which become public in the very-near future, which will hopefully provide extra data on this group.
The discovery image
I have been developing, as part of my job at the Chandra X-ray Center, a set of scripts to simplify the creation of exposure-corrected images from multiple Chandra observations. In looking around for test systems, I noted the recent set of observations on the galaxy cluster MACSJ0717.5+3745, which is a really interesting looking system, that have been used to detect a Dark-Matter filament in 3D, which is a really interesting result! There have been two Chandra observations of this target; the first, a relatively short “discovery” observation in 2001, followed by a longer observation in 2003.
If you have CIAO 4.4 installed, then you can quickly query the public Chandra archive from the command line using:
% find_chandra_obsid '7 17 33.8' '37 45 20'
# obsid sepn inst grat time obsdate piname target
1655 0.6 ACIS-I NONE 20.1 2001-01-29 VANSPEYBROECK "MACS J0717.5+3745"
4200 0.6 ACIS-I NONE 59.9 2003-01-08 Ebeling MACSJ0717.5+3745or you can use the Chandra Footprint Service.
Downloading the data and re-processing (using Chandra CALDB 4.5.3), with the following:
% download_chandra_obsid 1655,4200
... screen output removed ...
% chandra_repro 1655,4200 outdir=
% merge_obs '*/repro/*evt*[ccd_id=0:3]' quick8/ bands=csc
... a lot of screen output removed ...creates three exposure-corrected images, in the soft (0.5 to 1.2 keV), medium (1.2 to 2.0 keV), and hard (2.0 to 7.0 keV) bands, which can be viewed using ds9 (or other tool):
% cd quick8
% ds9 -scale sqrt -smooth -rgb -red soft_flux.img -green medium_flux.img -blue hard_flux.img &to create
A three-color image of MACSJ0717.7+3745
which shows the cluster in the center, as the blue-white blob, and the target of this investigation, a faint red point source with possible extended emission around it. The question is, is this really a group? Note that in the image the red channel corresponds to the soft band, the green channel the medium band, and the blue channel is the hard band, so the system is very soft (esentially no emission above 1.2 keV).
The coordinates of the point source are (as determined by eye, rather than with a source-detection algorithm) a Right Ascension of 07h 16m 44.3s and Declination of +37d 39’ 55" (J2000). Plugging these coordinates into NED, the NASA/IPAC Extragalactic Database, return what looks to be an Elliptical galaxy detected in the 2MASS survey. Here are the NED search results for 2MASX J07164427+3739556.
The Digital-Sky Survey image of the galaxy
This image is taken from the Digital Sky Survey and was created by the NED DSS service (I am not sure how long-lived this URL is).
