Detalles de publicación
PP 013014
Statistical Studies of HII Regions in the Nearby Galaxies. 1. Spitzer NIR luminosities and temperatures, compared with Halpha luminosities, of selecte4d HII regions in M100
1 43 Tamar Way, Didcot, OX11 7QH, United Kingdom
e-mail: sjchan2012@gmail.com
2 Instututo de Astrofisica de Canarias, 38205 La Laguna, Spain
e-mail: jeb@iac.es
3 CSIC, 28006 Madrid, Spain
4 Department of Astrophysics, University of La Laguna, E-38200 La Laguna, Tenerife, Spain
Aims. To study systematically the relations between the H! 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 H! 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; we also calculate their NIR
luminosities.
Results. The spectral fits allow us to separate the PAH emission in the 3.6 μm band from the
thermal dust emission which dominates the other three bands, and thereby to assign values for
the colour temperature of the dust. These values lie in the range 250 K - 350 K. There is a well
defined linear relation between the H! 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 H! luminosity is almost two orders of magnitude, the range in dust temperature is less than a
factor 2. This can be understood in scenarios where the OB association pushes the surrounding
dust and gas out to radii which are larger for higher luminosity regions and/or ablation of dust
particles close to the star cluster.
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 H! 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; we also calculate their NIR
luminosities.
Results. The spectral fits allow us to separate the PAH emission in the 3.6 μm band from the
thermal dust emission which dominates the other three bands, and thereby to assign values for
the colour temperature of the dust. These values lie in the range 250 K - 350 K. There is a well
defined linear relation between the H! 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 H! luminosity is almost two orders of magnitude, the range in dust temperature is less than a
factor 2. This can be understood in scenarios where the OB association pushes the surrounding
dust and gas out to radii which are larger for higher luminosity regions and/or ablation of dust
particles close to the star cluster.