Seminars and Colloquia

Efficient Mapmaking of the Stochastic Gravitational Wave Background

by Dr. Anirban Ain (IUCAA Pune (India))

Tuesday, 5 September 2017 from to (Europe/Rome)
at aula 131
Gravitational waves from the early universe and unresolved astrophysical 
sources are expected to create a stochastic GW background (SGWB). Radiometric 
techniques are used to make upper-limit maps of an anisotropic SGWB by cross-
correlating data from pairs of detectors. We have developed algorithms to 
perform this analysis in a highly efficient way. We fold the cross-spectral 
density of data from pairs of detectors, the core data set for a radiometer 
search, for a whole observation run to one sidereal day's data, providing 
enormous data compression and computational speed-up. To take full advantage 
of folded data and to make use of the well-known HEALPix pixelization and 
tools, we have developed a new code called PyStoch. PyStoch incorporates tools 
healpy packages and some more computational tricks that give a factor of few 
speed-up. Folding and PyStoch together has made it possible to perform 
radiometer map making in just a few minutes on a typical laptop. Moreover, 
PyStoch generates sky maps at every frequency bins as an intermediate data 
product. We hope that these techniques will make stochastic analysis very 
convenient and enable searches, e.g., blind narrowband search, which was not 
feasible so far due to computational limitations.