README FOR HELMS_V0.2 SANEPIC MAPS V0.3 - 2016-03-29 V0.2 - 2012-09-24 V0.1 - 2012-07-20 Viktoria Asboth (vasboth@phas.ubc.ca) ##################################################################### UPDATES FOR VERSION 0.3 These new maps were made from the time-streams pre-processed with the newer HIPE version. Additionally, they correct a problem with the noise maps that were erroneous in version 0.2 where the noise was around 10 times its actual value. ##################################################################### UPDATES FOR VERSION 0.2 * All 11 AORS are now included in the maps. The maps are now complete, although part of the field may be re-observed in the future due to the scattered light from Jupiter contaminating the map (described below in the V0.1 description). * The regions containing Uranus and the scattered light from Jupiter have been masked. Since only the horizontal scans were affected, there is still partial coverage throughout. The masked regions are easily visible by viewing the coverage map (3rd FITS extension). * Maps matching the ACT coordinate system (CEA: Cylindrical Equal Area) are now available: HELMS-ACT_image_???_SANEPIC_v0.2.fits These are in CEA coordinates, and have custom pixels sizes so that the maps can easily be rebbined to the ACT pixelisation: the pixels sizes are 7.425, 9.900 and 14.850 arcsec at 250, 350 and 500 micron, respectively. These are 4, 3 and 2 times smaller than the ACT pixels, which are 29.7 arcsec. * These maps should still be considered preliminary, as: - no aboslute astrometry correction (about 1 arcsec, so fairly insignificant) has yet been applied - there may be room for improvement in our despiking algorithm (particularly at 500 micron) ##################################################################### NOTES FROM VERSION 0.1 This is a preliminary release of HELMS maps. The maps are made using the SANEPIC. See arXiv:0711.3462 or ApJ. 681 (2008) 708-725 for a description This code was adapted from the original by Alex Beelen and Viktoria Asboth. These maps are a HerMES/ACT Collaborative data product and are available under the terms of the ACT/HerMES Collaborative MOU. The HELMS observations are comprised of 11 AORs (Astronomical Observation Requests) that cover the ~300 sq. deg in two roughly orthogonal scan directions. These preliminary maps are made from 10 of the 11 AORs that make up the full HELMS region. There is therefore one region (of roughly 67 sq. deg.) through the middle of the map that has been observed in only 1 direction. The integration time in this region is half that in the rest of the map, and the noise is therefore ~sqrt(2) times higher. Additionally, please note: * Uranus appears in these observations, at roughly 0:04:46 -0:15:32. The data in this region have been strongly clipped due to cosmic ray rejection algorithms. * There is a bright extended region at roughly 23:57:18 -0:03:15 showing strong striping artifacts. This emission is thought to be stray scattered light from Jupiter. We are currently investigating how to deal with this. * These maps are in tangent plane projection (the standard projection used by SMAP). This is non-ideal for HELMS, which extends +/-15 degrees in RA. Future releases will additionally include maps made in cylindrical equal-area (CEA) projection with custom pixel sizes tailored to match the ACT maps (for purposes of the ACT/HerMES HELMS collaboration). * Future releases will also include jack-knife maps (made by dividing up the data set in various ways). * These maps are incomplete. The 250 um and 350 um maps do not include data from the last three AORs, and therefore, in addition to the excess noise and striping mentioned above, there is a hole in the maps corresponding to an absence of data where the missing AOR provide the only coverage. ####################### FILE CONTENTS Each fits file in this data release contains 5 extensions: 1 - signal map [Jy / beam] 2 - error map, based on propagation of time-stream weights [Jy / beam] 3 - coverage map [number of hits per pixel] 4 - inifile [binary file listing the map-making parameters] 5- inputfiles [binary file listing the inputfiles]