Giant H II Regions in M101. I. X-ray Analysis of Hot Gas

TL;DR

This study uses Chandra X-ray observations to analyze hot gas in three giant H II regions in M101, revealing thermal components, outflows, and potential hypernova remnants, advancing understanding of energetic processes in star-forming regions.

Contribution

First detailed X-ray analysis of multiple GHRs in M101, identifying hot gas properties, outflows, and hypernova remnant candidates, providing new insights into their energetic phenomena.

Findings

Thermal X-ray component at ~0.2 keV detected in all GHRs.

Evidence of hot gas outflows from star-forming regions.

Identification of a hypernova remnant candidate with ~10^52 ergs energy.

Abstract

We performed a Chandra X-ray study of three giant H II regions (GHRs), NGC 5461, NGC 5462, and NGC 5471, in the spiral galaxy M101. The X-ray spectra of the three GHRs all contain a prominent thermal component with a temperature of ~0.2 keV. In NGC 5461, the spatial distribution of the soft (< 1.5 keV) X-ray emission is generally in agreement with the extent of H1105, the most luminous H II region therein, but extends beyond its southern boundary, which could be attributed to outflows from the star cloud between H1105 and H1098. In NGC 5462, the X-ray emission is displaced from the H II regions and a ridge of blue stars; the H-alpha filaments extending from the ridge of star cloud to the diffuse X-rays suggest that hot gas outflows have occurred. The X-rays from NGC 5471 are concentrated at the B-knot, a "hypernova remnant" candidate. Assuming a Sedov-Taylor evolution, the derived explosion energy, on the order of 10^52 ergs, is consistent with a hypernova origin. In addition, a bright source in the field of NGC 5462 has been identified as a background AGN, instead of a black hole X-ray binary in M101.