Spatial Distribution of Abundance Patterns in the Starburst Galaxy NGC 3079 Revealed with Chandra and Suzaku

Abstract

We performed simultaneous spectral analyses of Chandra (26.6 ks) and Suzaku (102.3 ks) X-ray data of the starburst galaxy NGC 3079. The spectra were extracted from four regions: 0.'5 (2.25 kpc) circle, an inner 0.'5-1' (2.25-4.5 kpc) ring, and an outer 1'-2' (4.5-9 kpc) ring from Chandra, and 4' (18 kpc) circle from Suzaku, all centered on the nucleus. Fittings of thermal plasma models yield interstellar medium (ISM) temperatures of 0.65^+0.05_-0.04 (0.'5 circle), 0.45^+0.07_-0.06 (0.'5-1' ring), and 0.24^+0.03_-0.02 (1'-2' ring) keV in the three regions. The combination of Chandra's high angular resolution and Suzaku's high spectral sensitivity enabled us to spatially resolve and measure the abundances of the metals O, Ne, Mg, Si, and Fe within the hot ISM. In particular, the abundance patterns of O/Fe, Ne/Fe, Mg/Fe, and Si/Fe in the central region (<4.5 kpc) are consistent with those expected from a supernova (SN) II synthesis. On the other hand, the pattern in the region beyond 4.5 kpc is closer to solar. The central region is also where copious polycyclic aromatic hydrocarbon infrared emission related to the recent starburst activity is known to occur. This suggests that we are seeing starburst-related SN II metal enrichment in the hot X-ray-emitting nuclear ISM. The spatial extent of SN II-like abundance patterns is consistent with that of NGC 3079 being in a relatively-early phase of starburst activity.