The atacama cosmology telescope: Two-season ACTPol extragalactic point sources and their polarization properties

Rahul Datta, Simone Aiola, Steve K. Choi, Mark Devlin, Joanna Dunkley, Rolando Dünner, Patricio A. Gallardo, Megan Gralla, Mark Halpern, Matthew Hasselfield, Matt Hilton, Adam D. Hincks, Shuay Pwu P. Ho, Johannes Hubmayr, Kevin M. Huffenberger, John P. Hughes, Arthur Kosowsky, Carlos H. López-Caraballo, Thibaut Louis, Marius LunguTobias Marriage, Loïc Maurin, Jeff McMahon, Kavilan Moodley, Sigurd K. Naess, Federico Nati, Michael D. Niemack, Lyman A. Page, Bruce Partridge, Heather Prince, Suzanne T. Staggs, Eric R. Switzer, Edward J. Wollack, Gerrit Farren

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


We report onmeasurements of the polarization of extragalactic sources at 148GHzmade during the first two seasons of the Atacama Cosmology Telescope Polarization (ACTPol) survey. The survey covered 680 deg2 of the sky on the celestial equator. Polarization measurements of 169 intensity-selected sources brighter than 30 mJy, that are predominantly active galactic nuclei, are presented. Above a total flux of 215 mJy where the noise bias removal in the polarization measurement is reliable, we detect 26 sources, 14 of which have a detection of linear polarization at greater than 3σ significance. The distribution of the fractional polarization as a function of total source intensity is analysed. Our result is consistent with the scenario that the fractional polarization of our measured radio source population is independent of total intensity down to the limits of our measurements and well described by a Gaussian distribution with a mean fractional polarization pm = 0.028 ± 0.005 and standard deviation σpm = 0.054, truncated at p = 0. Extrapolating this model for the distribution of source polarization below the ACTPol detection threshold, we predict that one could get a clean measure of the Emode polarization power spectrum of the microwave background out to l ≈ 6000 with 1 μK-arcminute maps over 10% of the sky from a future survey. We also study the spectral energy distribution of the total and polarized source flux densities by cross-matching with low radio frequency catalogues. We do not find any correlation between the spectral indices for total flux and polarized flux.

Original languageEnglish (US)
Pages (from-to)5239-5262
Number of pages24
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Jul 1 2019

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Catalogues
  • Cosmology: observations
  • Galaxies: active
  • Polarization
  • Surveys
  • Techniques: polarimetric


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