Spitzer Space Telescope - General Observer Proposal #30720


The Red Halos of Blue Compact Galaxies - Constraining the Dust
Content.

Principal Investigator: Nils Bergvall
           Institution: Uppsala Astronomical Observatory

Co-Investigators: 
Thomas Marquart, Uppsala Astronomical Observatory                     
Erik Zackrisson, Uppsala Astronomical Observatory                     
Göran Östlin, Stockholm Observatory                                   
Matthew Hayes, Stockholm Observatory                                  
Eija Laurikainen, Astronomy, Dept. of Physical Sciences, University   
Genoveva Micheva, Uppsala Astronomical Observatory                    
Kjell Olofsson, Uppsala Astronomical Observatory                      

Science Category: nearby galaxies (z<0.05, v_sys<15,000 km/s) 
 Observing Modes: IracMap MipsPhot 
  Hours Approved: 8.2 

Abstract:
The halos of BCGs play a crucial role in the understanding of the star
formation history of BCGs and provide unique information about the
starburst host.  We intend to investigate the outer regions of a
sample of luminous Blue Compact Galaxies (BCGs) that show a red color
excess in our previous deep optical and near-IR data.  These colours
have been compared to spectral evolutionary models and found to be
inconsistent with an expected old metal poor stellar population.
Possible models for the excess include reddening by a dusty
circumgalactic shell.  We propose to use Spitzer to test this option
in a search for cold dust at 70  and 160  micron in 5 BCGs.  For
comparison we will also observe 7 starburst host galaxy and postburst
candidates for which we recently obtained deep optical/near-IR
photometry.  In addition, we propose to use IRAC to search for excess
emission from hot circumstellar dust from late type stars in halos of
two of the BCGs.