Galactic Center Project Pages



Radio

About

The X-ray data were collected with several goals in mind: to identify rare classes of objects, such as high-mass X-ray binaries, using multi-wavelength observations; to study the distribution of hot plasma in the Galactic center, and how it interacts with the molecular clouds; to learn about the particle acceleration that occurs in the mysterious radio filaments; and to characterize the general population of X-ray sources (most of which are accreting white dwarfs). The original proposal is linked here.

The Chandra data incorporates all observations taken through the end of July 2007. It includes 1 Msec on the central 20 pc around Sgr A*, thirty shallow (12 ks) exposures from the Wang et al. (2002) survey, several deep pointings toward the Arches, Sgr B2 and Sgr C, and fifteen 40 ks exposures that were design to improve the sensitivity and astrometric accuracy of the Wang et al. (2002) data. The new catalog supersedes those in earlier papers by Muno et al. (2003-2005).

Catalogs

I have produced a catalog of 9067 point sources. The catalog is described in the paper submitted to ApJS (version 3 on 9/2/2008). I have made electronic tables (ASCII format) that list the positions and extraction information and the photometry for the sources. There are also tables summarizing the properties of sources with long-term and short-term variability. As an alternate way of accessing the table, I also have generated a FITS file (updated 8/30/2008 to reflect the final version). There is a README file that describes the colums of the FITS file, and region file for DS9. Photometry in individual observations is available in this FITS file (this will not be published electronically with the catalog paper). Finally, FITS images that provide maps of the completeness limits are available for 90% confidence and 50% confidence. The absolute astrometry has been registered to 2MASS, and appears accurate to 0.1-0.2" for all the deep (>20 ks) fields (0.6" for the rest).

Published Images

I have generated several images in FITS format. They are gzipped, so hopefully your browser won't treat them like text files. All of them have been normalized to an exposure map. The following can be used for looking at point sources and diffuse emission. The 1-3, 3-5, and 5-8 keV smoothed images were used to make the jpeg at the top of the page.

Here is the composite event list from all of the observations that was used to create the above images.

Preliminary Images

I have made a number of images to examine the distribution of line-emitting plasma in the Galactic center. These should be used with caution. There are no well-established techniques for producing these kinds of maps, because (1) there tends to be low signal from each line, and (2) the sensitivity for the mosaicked image varies strongly from point-to-point. As a result, my attempts so far have produced images that contain numerous artifacts. Most of what you see in the images is probably real, but there will be a non-trivial amount of spurious features that are misleading. Therefore, these images should not be used in publications. That said, they are interesting to look at.

For the following images, I excised the point sources, and filled the holes with Poisson noise from an annular region surrounding each source. They can be used for examining the diffuse emission. I had to rotate the images to turn them into Galactic coordinates, so you will notice that events look like ``islands'' consisting of several pixels; this is because I interpolated bins onto a new grid when I rotated the images. Also, the images processed with csmooth contain many, many artifacts, because csmooth is a pathological piece of work. I would look at the count images to see if features are real. Yes, I am suggesting that you compare two crappy sets of images, because coincident crap is more likely to be real.

Access to raw data

We are making the following data products available:

  • For each observation:
    • the astrometrically-corrected event files,
    • the astrometrically-corrected aspect solutions,
    • an exposure map covering the field,
    • bad pixels and pbk files, and
    • a mask for removing point sources.
  • For each source:
    • the combined list of events, for all observations,
    • the combined source and background spectra,
    • the combined effective area (arf) and response files (rmf),
    • the composite PSF image, and
    • and image of the source.

We have placed the data on an ftp site, ftp://hassif.srl.caltech.edu. If you want to download data in bulk, we recommend that you access data using a script that calls wget. Determine which sources you are interested using one or more of the tables in the paper, and save their names to a file, one per line. Then, write a script that loops over their names, and downloads the relevant directories. If the filename is called "sources.txt", then a csh version might look like this:

foreach file (`cat sources.txt`) wget -r ftp://hassif.srl.caltech.edu/pub/gc_project/${file}/ end You will now have one directory for each source listed in "sources.txt".

The event files can be accessed by

wget ftp://hassif.srl.caltech.edu/pub/gc_project/evtfiles.tar

Contacts: Michael Muno

Mid-IR

Infrared

X-ray

Transients

 

 

 

 

 

 

 

 

 

Last modified: Tue Jun 16 19:08:14 EDT 2009