N.FLAGEY(1), N. BILLOT(2), S. CAREY(1), A. NORIEGA-CRESPO(1), R. PALADINI(1), S. SHENOY(1), D. MIZUNO(3), K. KRAEMER(4)
(1)Spitzer Science Center, (2)NASA HERSCHEL SCIENCE CENTER, (3)Institute for Scientific Research, Boston College, (4)Air Force Research Laboratory.
We present a catalog of compact sources detected in the Spitzer/MIPSGAL 24 microns survey data. These small (< 1 arcminute) rings, bubbles, disks or shells are pervasive through the entire Galactic plane in the mid-infrared. Over 400 such sources are detected from visual inspection of the MIPSGAL mosaic images. Their average density is found to be around 1.5 bubbles per square degree. We identify 10% of these objects by extensive cross matching with available catalogs. We find that the majority are planetary nebulae (PNe), three are supernova remnants (SNR) and one is a post-AGB star. The remaining 90% of the bubbles are yet unknown objects. Most of them are detected at 24 microns but neither at 8 nor 70 microns. We also present Spitzer/IRS spectroscopic observations of a limited sub-sample of 15 objects. Their spectra show significant variations in the low to high excitation gas lines ratio, as well as in the dust continuum intensity, suggesting some are dust free objects. We compare these spectroscopic data to templates of evolved stars, including PNe, SNRs and extremely rare and massive luminous blue variables to constrain their true nature.
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