Statistical studies of HII regions in nearby galaxies. I. Spitzer near-IR luminosities and temperatures, compared with Hα luminosities, from selected HII regions in M100

Chan, S. J.; Beckman, J. E.
Referencia bibliográfica

Astronomy and Astrophysics, Volume 553, id.A54, 11 pp.

Fecha de publicación:
5
2013
Número de autores
2
Número de autores del IAC
1
Número de citas
2
Número de citas referidas
0
Descripción
Aims: We systematically study the relations between the Hα luminosity and the near-IR luminosity and temperature of a set of selected HII regions in the disc of M100. Methods: By using the technique of cross-reference between the optical Hα image (the catalogue of HII regions in M100) and the Spitzer IRAC images, we locate the selected HII regions in the IRAC image frames. By using the chi-squared non-linear fitting technique, we estimate the IRAC-3-band colour temperature Tcol(IRAC) of selected HII regions, and calculate their near-IR luminosities. Results: The spectral fits allow us to separate the PAH emission in the 3.6 μm band from the thermal dust emission that dominates the other three bands, thereby assigning values for the colour temperature of the dust. These values lie in the range 250 K to 350 K. There is a well defined linear relation between the Hα luminosity and the derived IRAC luminosity for the HII regions, but no apparent relation between the latter and the colour temperature. While the range in Hα luminosity is almost two orders of magnitude, the range in temperature is less than a factor two. We also find that the colour temperature is independent of galactocentric radius, in contrast to previous findings for electron temperatures in HII regions. These results could be understood in scenarios where the OB association pushes the surrounding dust and gas out to radii that are larger for higher luminosity regions or, alternatively, where the dust we are measuring consists of tiny stochastically heated grains.
Proyectos relacionados
Poster Almeria Astronomy week
Estudios Cinemáticos, Estructurales y de Composición, de los Medios Interestelares e Intergalácticos
El objetivo básico del proyecto es investigar la evolución de las galaxias mediante el entendimiento de la interacción del medio interestelar y las estrellas. La técnica principal que utilizamos es la cinemática bidimensional de galaxias enteras observada por nuestro instrumento GHaFaS, un interferometro Fabry Perot en el telescopio William
Prof.
John E. Beckman