The large-scale structure samples have a bright star mask. We center circular mask on the positions of bright stars in the Tycho2 catalog. The radii of the masks are determined using a formula originally determined by Iskra Strateva.
Here is the IDL code which determines the radii in degrees:
tycho=tycho_read(columns=['ramdeg','demdeg','btmag'])
indx_tycho=where(tycho.btmag lt 13. and $
(tycho.ramdeg ne 0. or tycho.demdeg ne 0.))
tycho=tycho[indx_tycho]
tychobmag=(tycho.btmag > 6.) < 11.5
tychorad=(0.0802*tychobmag^2 - 1.860*tychobmag + 11.625)/60.
Thus, we include Tycho catalog stars brighter than B=13, and vary the radius of the mask between B=6 and B=11.5 (bigger mask for brighter stars). The radius corresponds to about where Iskra found that the number counts of galaxies around Tycho stars of that magnitude had decreased 1/3 from the counts at large radii.
The mask is designed such that it does not exceed the window as described by the lss_geometry file. In addition, each bright star mask is fully contained within a polygon in that file (such that a single star might have its mask broken into several pieces if it crosses field boundaries).
This file can be read in using the
read_fits_polygons
tool in idlutils.
The columns are:
There is an ASCII version of this file in mangle format called lss_bsmask.ply. Also, there is an associated file called lss_bsmask_info.dat with the columns:
[ilss] [itycho]