Figure 2. Color composite image of the core region of NGC 253, from T-ReCS images using the filters Si-2 (blue), [NeII] (green) and Qa (red). The nucleus candidate IRC appears as the brightest object in the infrared. The wavelength range covered by T-ReCS images goes from 8 to 20 μm. The field of view is 32 x 23 arcseconds.
The nearest spiral galaxy with a nuclear starburst (greatly enhanced star formation near a galaxy’s center) is also the site of a long-standing astronomical mystery. Designated NGC 253, or by amateurs as the Silver Dollar Galaxy, the core of this galaxy is so shrouded by gas and dust that the exact location of its core has remained unresolved for years. Now, thanks to research by Guillermo Günthardt of the National University of Cordoba (Argentina), Gemini South infrared data appear to have unambiguously pinpointed the galaxy’s core. In the process, evidence for a lowish-mass, but rapidly growing, black hole as the starburst’s trigger is painting a new picture of this enigmatic galaxy (Figure 1).
In the team’s paper, to appear in the next issue of The Astronomical Journal the team presents kinematic, spectrophotometric, and morphological evidence that support the hypothesis that the IRC is NGC 253's galactic nucleus. This includes the fact that the IRC is the most massive object in NGC 253's central region, the major source of the nuclear starburst outflow, the molecular gas rotation center, and it is almost coincident with the galactic bar symmetry center.
This work is available on Astro-ph at: http://arxiv.org/abs/1509.00330