Abstract
The hot ISM in early type galaxies (ETGs) plays a crucial role in understanding their formation and evolution. The structural features of the hot gas identified by Chandra observations point to key evolutionary mechanisms, (e.g., AGN and stellar feedback, merging history). In our Chandra Galaxy Atlas (CGA) project, taking full advantage of the Chandra capabilities, we systematically analyzed the archival Chandra data of 70 ETGs and produced uniform data products for the hot gas properties. The primary data products are spatially resolved 2D spectral maps of the hot gas from individual galaxies. We emphasize that new features can be identified in the spectral maps which are not readily visible in the surface brightness maps. The high-level images can be viewed at the dedicated CGA website, and the CGA data products can be downloaded to compare with data at other wavelengths and to perform further analyses. Utilizing our data products, we address a few focused science topics.
Highlights
For the past two decades, the Chandra X-ray Observatory has revolutionized many essential science subjects in astronomy and astrophysics
To remove the time intervals of background flares,13 we generate light curves from the point-source removed event files, determine the mean rate and its standard deviation, apply a CIAO tool deflare with 2σ clipping. While this method works for most observations, it fails in extreme cases when the flare occurs during a significant fraction of a given observation or the background rate changes gradually throughout the observation
We note that while we use the merged data to detect point sources and to perform spatial binning, we analyze the individual observations for extracting the X-ray spectra and producing the corresponding calibration files, rmf/ arf, because the CCD responses and pointspread function (PSF) vary as a function of detector location, photon energy, and observing time
Summary
For the past two decades, the Chandra X-ray Observatory has revolutionized many essential science subjects in astronomy and astrophysics. Various structural features of the hot ISM, which was previously considered as smooth and featureless, have been identified by Chandra They include cavities, cold fronts, filaments, and tails, which are closely related to critical astrophysical mechanisms for the galaxy formation and evolution, e.g., AGN feedback, merging history, accretion, stripping, and star formation (SF) and its quenching (e.g., see Kim & Pellegrini 2012 and references therein). Using the first four years of Chandra observations, Diehl & Statler (2007, 2008a, 2008b) assembled a sample of 54 nearby (D 100 Mpc) ETGs (or 36 with temperature profiles) These authors produced a systematic characterization of the hot gas morphology and compared this morphology with the optical stellar distribution, radio emission, and AGN properties.
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