Diffuse X-ray emission in spiral galaxies

Krystal Tyler, A. C. Quillen, Amanda LaPage, George H. Rieke

Research output: Contribution to journalArticle

30 Citations (Scopus)

Abstract

We compare the soft diffuse X-ray emission from Chandra images of 12 nearby intermediate-inclination spiral galaxies to the morphology seen in Hα, molecular gas, and mid-infrared emission. We find that diffuse X-ray emission is often located along spiral arms in the outer parts of spiral galaxies but tends to be distributed in a more nearly radially symmetric morphology in the center. The X-ray morphology in the spiral arms matches that seen in the mid-infrared or H α and thus implies that the X-ray emission is associated with recent active star formation. In the spiral arms there is a good correlation between the level of diffuse X-ray emission and that in the mid-infrared in different regions. The correlation between X-ray and mid-IR flux in the galaxy centers is less strong. We also find that the central X-ray emission tends to be more luminous in galaxies with brighter bulges, suggesting that more than one process is contributing to the level of central diffuse X-ray emission. We see no strong evidence for X-ray emission trailing the location of high-mass star formation in spiral arms. However, population synthesis models predict a high mechanical energy output rate from supernovae for a time period that is about 10 times longer than the lifetime of massive ionizing stars, conflicting with the narrow appearance of the arms in X-rays. The fraction of supernova energy that goes into heating the interstellar medium must depend on environment and is probably higher near sites of active star formation. The X-ray estimated emission measures suggest that the volume filling factors and scale heights are low in the outer parts of these galaxies but higher in the galaxy centers. The differences between the X-ray properties and morphology in the centers and outer parts of these galaxies suggest that galactic fountains operate in outer galaxy disks but that winds are primarily driven from galaxy centers.

Original languageEnglish (US)
Pages (from-to)213-225
Number of pages13
JournalAstrophysical Journal
Volume610
Issue number1 I
DOIs
StatePublished - Jul 20 2004

Fingerprint

spiral galaxies
x rays
galaxies
star formation
supernovae
scale height
disk galaxies
molecular gases
inclination
energy
heating
stars
life (durability)

Keywords

  • Galaxies: ISM
  • Galaxies: spiral
  • X-rays: galaxies

ASJC Scopus subject areas

  • Space and Planetary Science

Cite this

Diffuse X-ray emission in spiral galaxies. / Tyler, Krystal; Quillen, A. C.; LaPage, Amanda; Rieke, George H.

In: Astrophysical Journal, Vol. 610, No. 1 I, 20.07.2004, p. 213-225.

Research output: Contribution to journalArticle

Tyler, K, Quillen, AC, LaPage, A & Rieke, GH 2004, 'Diffuse X-ray emission in spiral galaxies', Astrophysical Journal, vol. 610, no. 1 I, pp. 213-225. https://doi.org/10.1086/421544
Tyler, Krystal ; Quillen, A. C. ; LaPage, Amanda ; Rieke, George H. / Diffuse X-ray emission in spiral galaxies. In: Astrophysical Journal. 2004 ; Vol. 610, No. 1 I. pp. 213-225.
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AB - We compare the soft diffuse X-ray emission from Chandra images of 12 nearby intermediate-inclination spiral galaxies to the morphology seen in Hα, molecular gas, and mid-infrared emission. We find that diffuse X-ray emission is often located along spiral arms in the outer parts of spiral galaxies but tends to be distributed in a more nearly radially symmetric morphology in the center. The X-ray morphology in the spiral arms matches that seen in the mid-infrared or H α and thus implies that the X-ray emission is associated with recent active star formation. In the spiral arms there is a good correlation between the level of diffuse X-ray emission and that in the mid-infrared in different regions. The correlation between X-ray and mid-IR flux in the galaxy centers is less strong. We also find that the central X-ray emission tends to be more luminous in galaxies with brighter bulges, suggesting that more than one process is contributing to the level of central diffuse X-ray emission. We see no strong evidence for X-ray emission trailing the location of high-mass star formation in spiral arms. However, population synthesis models predict a high mechanical energy output rate from supernovae for a time period that is about 10 times longer than the lifetime of massive ionizing stars, conflicting with the narrow appearance of the arms in X-rays. The fraction of supernova energy that goes into heating the interstellar medium must depend on environment and is probably higher near sites of active star formation. The X-ray estimated emission measures suggest that the volume filling factors and scale heights are low in the outer parts of these galaxies but higher in the galaxy centers. The differences between the X-ray properties and morphology in the centers and outer parts of these galaxies suggest that galactic fountains operate in outer galaxy disks but that winds are primarily driven from galaxy centers.

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