We present a catalog of 191 extragalactic sources detected by the Atacama Cosmology Telescope ( ACT ) at 148 GHz and/or 218 GHz in the 2008 Southern survey .
Flux densities span 14 to 1700 mJy , and we use source spectral indices derived using ACT-only data to divide our sources into two subpopulations : 167 radio galaxies powered by central active galactic nuclei ( AGN ) , and 24 dusty star-forming galaxies ( DSFGs ) .
We cross-identify 97 % of our sources ( 166 of the AGN and 19 of the DSFGs ) with those in currently available catalogs .
When combined with flux densities from the Australian Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array , the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz , with the trend continuing to 218 GHz .
The ACT dust-dominated source population has a median spectral index , \alpha _ { \mathrm { 148 - 218 } } , of 3.7 ^ { +0.62 } _ { -0.86 } , and includes both local galaxies and sources with redshift around 6 .
Dusty sources with no counterpart in existing catalogs likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups .