Variation in the dust spectral index across M33
  Using the Herschel PACS and SPIRE FIR/submm data, we investigate variations in the dust spectral index $\beta$ in the nearby spiral galaxy M33 at a linear resolution of 160 pc. We use an iteration method in two different approaches, single and two-component modified black body models. In both approaches, $\beta$ is higher in the central disk than in the outer disk similar to the dust temperature. There is a positive correlation between $\beta$ and Halpha as well as with the molecular gas traced by CO(2-1). A Monte-Carlo simulation shows that the physical parameters are better constrained when using the two-component model. 
F. S. Tabatabaei, J. Braine, C. Kramer, M. Xilouris, M. Boquien, S.   Verley, E. Schinnerer, D. Calzetti, F. Combes, F. Isra...
astro-ph.CO