1. X-ray Astronomy Group Richard Owen, Bob Warwick University of Leicester The X-ray Morphology and Spectra of Galactic Disks X-rays from Nearby Galaxies

2. X-ray Astronomy Group Introduction We use XMM-Newton to analyze disk emission from a sample of nearby face-on spiral galaxies. After exclusion of bright X-ray point sources, we investigate: The spectral components in the galactic disk The morphology of the residual X-ray emission Correlation with NUV emission X-rays from Nearby Galaxies

3. X-ray Astronomy Group Exclusion of bright X-ray point sources (1) XMM-Newton soft-band (0.3-1 keV) image of M83. Simulated PSF image of bright point sources. X-rays from Nearby Galaxies

4. X-ray Astronomy Group Exclusion of bright X-ray point sources (2) Surface brightness cut on simulated image forms source mask. Tails of PSF extending beyond mask are subtracted to produce residual image. X-rays from Nearby Galaxies

5. X-ray Astronomy Group Galaxies in the sample GalaxyM51M83M101 Hubble TypeSbcScScd Distance (Mpc)7.13.77.2 D 25 (arcmin)6.912.828.4 N H (10 20 cm -2 )1.33.91.1 MBMB -20.3-19.6-21.0 Total L X (10 39 erg s -1 ) (0.3-6 keV) 19.47.48.7 X-rays from Nearby Galaxies

6. X-ray Astronomy Group GALEX NUV OM UOM V M101: Soft X-ray and NUV emission (1) Warwick et al 2007 10’ ~ 22.6 kpc The central 5’ of the soft X-ray image above and NUV map shown compressed on right with X-ray contours. 0.3-1 keV

7. X-ray Astronomy Group M101: Soft X-ray and NUV emission (2) The correlation between soft X-ray and emission from the XMM OM UVW1 filter is studied within the central 5’ of M101. Warwick et al 2007 UVW1 0.3-1 keV 10’ ~ 22.6 kpc

8. X-ray Astronomy Group For 0.2 keV component: τ cool ≈ 1.8 x 10 8 η ½ yr Not compatible with η~1 due to narrow spiral features in soft X-ray. Implies clumpy thin-disk component. M101: Radial distribution and spectral analysis Warwick et al 2007 Radial distribution: exponential with scalelength 2.6’ (5.4 kpc). Best fit spectral model: two-temperature mekal, kT ≈ 0.2 and 0.7 keV. L X (0.3-2 keV) ≈ 2.6 x 10 39 erg s -1

9. X-ray Astronomy Group M83: Soft X-ray and NUV emission (1) Owen et al 2007 (in prep) 12.8’ ~ 13.8 kpc XMM-Newton soft X-ray and OM UVW1 images of M83 overlaid with soft X-ray contours. 0.3-1 keV UVW1

10. X-ray Astronomy Group M83: Soft X-ray and NUV emission (2) Soft X-ray residual and OM UVW1 images are shown overlaid with the bright source mask, showing areas used in correlation analysis. Owen et al 2007 (in prep) 0.3-1 keVUVW1 8’ ~ 8.6 kpc

11. X-ray Astronomy Group M83: Spectral analysis Best fit spectral model: two-temperature mekal with kT ≈ 0.2 and 0.6 keV. L X (0.3-2 keV) ≈ 1.9 X 10 39 erg s -1. Owen et al 2007 (in prep)

12. X-ray Astronomy Group M51: Soft X-ray and NUV emission (1) 7’ ~ 14 kpc 0.3-1 keV UVW1 Soft X-ray image and UVW1 image of M51, with X-ray contours shown. X-rays from Nearby Galaxies

13. X-ray Astronomy Group M51: Soft X-ray and NUV emission (2) 0.3-1 keV UVW1 Correlation is performed for the regions of M51 not obscured by the source mask, extending out to its D 25 radius. 7’ ~ 14 kpc

14. X-ray Astronomy Group M51: Spectral analysis Best fit spectral model: two-temperature mekal (kT ≈ 0.2, 0.6 keV) with added power-law component (Γ~2.7). L X (0.3-2 keV) ≈ 5.2 x 10 39 erg s -1. X-rays from Nearby Galaxies

15. X-ray Astronomy Group Comparison of soft X-ray versus NUV correlations M101 M51 M83 Correlations give the best fit gradients: M51: 0.040 ± 0.005 M83: 0.088 ± 0.010 M101: 0.041 ± 0.005 These must be corrected for extinction in both X-ray and UV. X-rays from Nearby Galaxies Extinction corrected 0.038 ± 0.005 0.079 ± 0.010 0.039 ± 0.005

16. X-ray Astronomy Group Summary results for diffuse emission GalaxyM51M83M101 Source L X threshold (10 37 erg s -1 ) 5.02.01.0 Diffuse L X (10 39 erg s -1 ) (0.3-1 keV) 4.41.61.7 % attributed to sources~35~25~20 Ratio of soft/hard emission 1.51.13.8 X-ray/UV count-rate ratio 0.0380.0790.039 X-rays from Nearby Galaxies

17. X-ray Astronomy Group Conclusions X-ray spectra of spiral galaxy disks are typically characterized by two-temperature fits, with kT ≈ 0.2 and 0.6-0.7 keV. Diffuse emission can be separated into a clumpy component tracing the spiral arms and a broadly exponential lower halo component. In this study we find very good correlation between soft X-ray emission and NUV emission. The X-ray/UV count-rate ratio derived is consistent between M51 and M101, but is twice as large in M83. We note that the result derived for M83 appears to be due to a genuine soft X-ray excess rather than a UV deficit. X-rays from Nearby Galaxies