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In search for the oldest star forming regions in Holmberg II

J. Kerp·F. Walter
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Abstract

We present an X-ray study of the irregular dwarf galaxy Holmberg II based on deep ROSAT PSPC observations. Holmberg II is one of the most famous examples of an irregular dwarf galaxy with a disrupted interstellar medium (ISM): expanding HI holes are present across the entire face of the galaxy. Huge HI cavities of kpc extent are found even outside current starforming regions. We search for faint X-ray sources (stellar end points as well as hot gas), touching the limits of the ROSAT PSPC detector and link the newly detected X-ray sources to features detected in other wavelengths. Using an X-ray hardness ratio color-color diagram we show that it is possible to differentiate between thermal plasma and power-law X-ray spectra, which helps to track down the physical nature of the individual sources.

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J. Kerp, F. Walter. 2000-12-12. In search for the oldest star forming regions in Holmberg II. https://arxiv.org/abs/astro-ph/0012255

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