ACT (ACTPol) Data Products - ACT Maps

ACT DR4 Frequency Maps at 98 and 150 GHz presented in Aiola et al. 2020


These 376 FITS files are the maps made with the nighttime 2013(s13) to 2016(s16) data from the ACTPol camera on the ACT telescope at 98(f090) and 150(f150) GHz.

These maps and their properties are described in Aiola et al. (2020) and Choi et al. (2020)

Naming and products

The maps are released both as 2- or 4-way independet splits, used to compute the power spectra, and as inverse-variance map-space co-added.

File naming


  • "release": these maps are part of the DR4 data release, and versioning allows for future modifications of thise relase [possible tags: dr4.xy]
  • "season": observation season [possible tags: s13, s14, s15, s16]
  • "patch": survey patch [possible tags: D1, D5, D6, D56, D8, BN, AA]
  • "array": telescope optic module on ACTPol camera [possible tags: pa1, pa2, pa3]
  • "freq": frequency tag [possible tags: f090, f150]
  • "nway": number of independet splits [possible tags: 2way, 4way]
  • "set": split identifier or co-add version [possible tags: set0, set1, set2, set3, coadd]
  • "product": see below for list of released products

Available products

More detailes availble in Sec. 5 of Aiola et al (2020)

  • "map_srcfree": observed I,Q,U Stokes components with signal from point sources subtracted [uK]
  • "srcs": I,Q,U Stokes components of the point sources signal [uK]
    NOTE: "map_srcfree"+"srcs" is the observed sky
  • "ivar": inverse-variance pixel weight [uK^-2]
  • "xlink": cross-linking information encoded as I,Q,U Stokes components [uK^-2]


The "map_srcfree", "srcs", and "ivar" maps are calibrated with a single coefficient, which is measured for each field and reported in Choi et al (2020). An extra polarization efficiency parameter is included (and let to vary) in the likelihood analysis and NOT considered here.


  • These maps are released following the IAU polarization convention (POLCCONV='IAU' in FITS header).
  • Baseline software to handle these maps is Pixell (

Back To ACT (ACTPol): DR4 2013-2016 Derived Maps

A service of the HEASARC and of the Astrophysics Science Division at NASA/GSFC
Goddard Space Flight Center, National Aeronautics and Space Administration
HEASARC Director: Dr. Andrew F. Ptak
LAMBDA Director: Dr. Thomas M. Essinger-Hileman
NASA Official: Dr. Thomas M. Essinger-Hileman
Web Curator: Mr. Michael R. Greason