CSOLOGO1 CSOLOGO2SHARCII  Captures Images of Distant Dust-Enshrouded Galaxies


  Galaxies formed many billions of years ago in violent bursts of star-formation.  A by-product of these stellar factories is a large amount of dust, which can often obscure optical light coming from the newly formed stars, unfortunately making the stars sometimes extremely difficult to see using optical telescopes.  However, we can pinpoint these distant dusty galaxies using submillimeter cameras which are sensitive to the signatures of the cold dust emission.  In this vein, a large UK-led international consortium undertook the SCUBA HAlf Degree Extragalactic Survey (SHADES), using the 850 micron SCUBA camera at the James Clerk Maxwell Telescope in Hawaii, to map large contiguous regions of sky in order to find these galaxies in the throes of formation.  But to elucidate the physics of these galaxies (such as their dust content, power output, and temperatures), we need additional measurements across a broad range of wavelengths in order to construct their spectral energy distributions (SEDs).  Critical information comes from measuring the location and height of the SED peak at shorter submillimeter wavelengths, such as with the 350 micron channel of the CSO's SHARCII camera.

  Dr. Kristen Coppin at Durham University in the UK and the SHADES consortium took 350 micron SHARCII snapshots of several distant dusty star-forming galaxies from SHADES.  These new observations have shown us these high-redshift 'submillimeter galaxies' contain about a billion-suns -worth of cold dust (only ~30 degrees Kelvin above absolute zero!) and that they are producing stars at hundreds of times the rate of our own Milky Way galaxy.  These distant submillimeter galaxies are unlike nearby star-forming galaxies with similar temperatures in that they are an order of magnitude more luminous and dusty on average.  This could mean that either the submillimeter galaxies are much more massive compared with local starburst galaxies, or possess a higher fraction of gas and dust than local galaxies, or even that dust at high redshift could have different properties altogether than local dust.  Future surveys with BLAST, Herschel, and SCUBA2 will be able to make the next leap in understanding the physics in these extreme galaxies.  This result was published by Coppin et al. 2008 in the Monthly Notices of the Royal Astronomical Society. 



Figure 1. A zoomed in SHARCII snapshot of a few of brightest submillimetre galaxies. These galaxies are very distant (it took o
ver 5-10 billion years for the light we see to reach us!) and are much smaller in extent than the resolution of the CSO, which is wh
y they appear unresolved here as bright 'blobs'.


Figure 2. Dust emits thermal radiation in the far-infrared and so we have fit simple thermal curves to the data points for each galaxy in order to describe their energy output as a function of wavelength (the solid lines are the 'best-fit' and the dotted lines indicate the error bounds).  The names on each plot indicate the region of sky that the galaxies were found in (LOCK=Lockman Hole, SXDF=Subaru XMM Deep Field), and the galaxy redshifts are also provided.  You can see how the new SHARCII data is crucial for constraining the location of the peak of the model curves - which physically translates to measuring the temperature of the dust that is emitting the radiation we are seeing in Figure 1.