Spatial distribution of emission in unidentified infrared bands from the midcourse space experiment survey

Abstract

The Midcourse Space Experiment (MSX) has surveyed the Galactic plane in four infrared bands between 6 and 25 µm. Two of these bands cover several Unidentified Infrared emission Bands (UIBs). With the aim of extracting the spatial distribution of the UIB emission on a large scale, a scheme has been developed to model the MSX data with emission in the UIBs alongwith the underlying thermal continuum from the interstellar dust. In order to test this scheme, a sample of five Galactic compact H II regions (Sh-61, Sh-138, Sh-152, Sh-156, Sh-186; Zavagno & Ducci 2001) for which imaging data in some individual UIBs is available from ISOCAM measurements, has been studied. The results of this comparative study on a small angular scale are as follows: (i) the morphological details extracted from our scheme agree very well with those from the superior ISOCAM measurements; (ii) the integrated strength of UIBs extracted from the MSX database correlates extremely well with the sum of the strengths of individual UIBs measured from ISOCAM. This tight correlation is very encouraging and promises the potential of MSX database for the study of large-scale spatial distribution of UIB emission (and the carriers of UIBs) in the entire Galactic plane.