X-ray Halo Around the Spiral Galaxy NGC 4631 Observed with Suzaku

TL;DR

This study used Suzaku X-ray observations to analyze the metal content and temperature of the halo around galaxy NGC 4631, revealing insights into galactic winds and supernova contributions.

Contribution

First detailed measurement of metal abundance and temperature in NGC 4631's halo, indicating effective metal transport via galactic winds from supernovae.

Findings

Halo extends about 10 kpc from the disk.

Metal abundance pattern matches type II supernova yields.

Upper limit on hard X-ray flux suggests magnetic field > 0.5 μG.

Abstract

Suzaku observation of the edge-on spiral galaxy NGC 4631 confirmed its X-ray halo extending out to about 10 kpc from the galactic disk. The XIS spectra yielded the temperature and metal abundance for the disk and the halo regions. The observed abundance pattern for O, Ne, Mg, Si and Fe is consistent with the metal yield from type II supernovae, with an O mass of about 1E6 Msun contained in the halo. These features imply that metal-rich gas produced by type II supernova is brought into the halo region very effectively, most likely through a galactic wind. Temperature and metal abundance may be affected by charge exchange and dust. An upper limit for the hard X-ray flux was obtained, corresponding to a magnetic field higher than 0.5 uG.