A Survey of Molecular Gas in Luminous Sub-millimetre Galaxies
Oct 10, 2012
3:20PM to 4:20PM
Date(s) - 10/10/2012
3:20 pm - 4:20 pm
Title: A Survey of Molecular Gas in Luminous Sub-millimetre Galaxies
Speaker: Dr. Scott Chapman
Institute: Dalhousie University
Location: ABB 102
We present the results from a survey for CO emission in luminous sub-millimetre galaxies (SMGs), conducted with the Plateau de Bure Interferometer (PdBI). We observed a total of 40 SMGs at z=1-4 with 850-um fluxes of S850um=4.2-20.3 mJy. We detect CO emission in 32 SMGs, including 16 SMGs not previously observed in CO, which doubles the number of
unlensed SMGs with measured molecular gas properties. Using multiple CO line (J=2-7) observations, we derive a median spectral line energy distribution (SLED) for luminous SMGs. We report the discovery of a fundamental relationship between CO FWHM and CO line luminosity of high-z starbursts,
which we interpret as a natural consequence of the baryon-dominated dynamics within the regions probed by our observations. We use far-infrared luminosities to assess the star-formation efficiency in our SMGs, finding an
approximately linear slope of the L’CO-LFIR relation for SMGs. We derive dynamical masses and molecular gas masses, which allow us to place dynamical constraints on the value of the CO/H2 conversion factor alpha~1.0. We discuss the redshift evolution of the gas content of SMGs, finding that SMGs do not appear to have significantly higher baryonic gas fractions than less vigorously star-forming galaxies at comparable redshifts.
I will also highlight our ALMA imaging and CO-line survey of gravitationally lensed SMGs discovered from the South Pole Telescope survey, and how they shed light on an unbiased redshift distribution for the SMG population.