X-ray properties of the starburst-driven outflow in NGC 253 .
Abstract
For a further understanding of a galactic-scale starburst-driven outflow, the X-ray properties of the hot interstellar gas in a well-studied nearby edge-on starburst galaxy, NGC 253, were investigated. Spectroscopic analysis was performed in three regions of the galaxy characterized by multiwavelength observations, i.e., the superwind region, the disk region and the halo region. The hot gas can be represented by two thin thermal plasmas (kT ∼0.2 and ∼0.6 keV) with various emission lines such as O, Ne, Mg, Si and Fe, in all three regions. Abundance patterns, i.e., O/Fe, Ne/Fe, Mg/Fe and Si/Fe, are consistent among the three regions, which suggests a common origin of the hot gas. Abundance patterns are heavily contaminated by type II supernova, which supports an indication that the hot gas in the halo region originates from the central starburst activity. Energetics can also provide the same conclusion if 0.01-50 eta 1/2 % of the total emission in the nuclear region has been transported into the halo region. The obtained polytropic equation of state of the hot gas between the density and the temperature suggests that the hot gas expands adiabatically in the disk region while it moves as free expansion in the halo region towards the outer part of the halo region as the outflow. The outflow velocity of >100 km s-1 is required and it is indicated that the hot gas can escape from the gravitational potential of NGC 253 by combining the outflow velocity and the thermal velocity.
- Publication:
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Memorie della Societa Astronomica Italiana
- Pub Date:
- 2013
- Bibcode:
- 2013MmSAI..84..758M
- Keywords:
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- starburst;
- X-ray;
- NGC 253