Spitzer mid-infrared study of compact H II regions in the Magellanic Clouds

Abstract

Aims: We present a study of the mid-infrared properties and dust content of a sample of 27 H ii “blobs”, a rare class of compact H ii regions in the Magellanic Clouds. A unique feature of this sample is that even though these H ii regions are of high and low excitation they have nearly the same physical sizes ~1.5-3 pc.
Methods: We base our analysis on archival 3-8 μm infrared imagery obtained with the Infrared Array Camera (IRAC) on board the Spitzer Space Telescope.
Results: We find that despite their youth, sub-solar metallicity and varied degrees of excitation, the mid-infrared colors of these regions are similar to those of typical H ii regions. Higher excitation “blobs” (HEBs) display stronger 8 μm emission and redder colors than their low-excitation counterparts (LEBs).