X-Raying Chemical Evolution and Galaxy Formation in the Antennae

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Abstract
We present the integrated 411 ks Chandra ACIS-S exposure of the Antennae galaxies (NGC 4038/39). Besides a rich population of pointlike sources, this spectacular image reveals a spatially and spectrally complex hot diffuse gaseous component. For the first time we detect intense line emission from Fe, Ne, Mg, and Si in the Antennae and obtain a detailed picture of spatially varied metal abundances in the hot interstellar medium (ISM) of a galaxy. In certain regions, the abundances of α-elements may be many times solar, while the Fe abundance is subsolar or near-solar. The differences in the local metal enrichment of the hot ISM may be related to the local star formation rates and to the degree of confinement of the enriched hot ISM. We also report large-scale gaseous features, including two gigantic, ~10 kpc scale "loops" extending to the south of the merging disks and a low surface brightness hot halo, extending out to ~18 kpc. These features may be related to superwinds from the starburst in the Antennae or result from the merger hydrodynamics. Their long cooling times suggest that they may persist to form the hot X-ray halo of the emerging elliptical galaxy.
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