ACT Data Products - CMB Masks 2014, 148 & 220 GHz
The point source masks are maps, in FITS format, with the same footprint and World Coordinate System as the associated 148 GHz and 220 GHz data. The mask is unity everywhere except in circles of 10 arcminute diameter around sources detected in the data. These sources were detected in the combined 148 GHz and 220 GHz data from the 2009+2010 season data with a matched filter, which uses the ACT beam profile along with an estimation of the map noise. After filtering, sources detected with a signal to noise ratio of 5 and with a 148/220 GHz flux density of 15 mJy were identified for masking. Due to edge effects, some spurious detections are masked in regions of low hits-per-pixel. Such edge regions are generally undesirable for analysis.
In addition to the 15mJy cut for both southern and equatorial point sources, a dust template is added to the mask used for equatorial data only. The equatorial dust mask was generated from the 100 \mu m dust maps from IRIS, by identifying and setting to zero all pixels above a flux density of 5.44 MJy/sr as well as pixels that fall inside significantly clustered structures.
To use the mask, read in both the data and the mask and multiply the data, pixel-wise, by the mask.
For more information about the matched filtering used to detect sources in ACT data, see http://adsabs.harvard.edu/abs/2011ApJ...731..100M.