= Poor Man's Background and Sensitivity maps =

Using
  * [[ExpoMaps]] exposure map V2ero_sun_radec.fits by Jan Robrade
  * xspec12 background models by Thomas Boller (MPE) & Katharina Borm (Bonn) as presented June 13, 2012
  * HI map by Kalberla et al. 2005, A&A, 440, 775, known as the Leiden/Argentine/Bonn (LAB) survey; extracted using http://heasarc.gsfc.nasa.gov/lheasoft/ftools/fhelp/nh.txt

I (Johannes Buchner <jbuchner@mpe.mpg.de>) created simple background maps for the bands chosen by Thomas Boller (MPE) presented June 13, 2012.

Various efficiencies (20%, 50%, 90%) have been computed (product of survey time and quantum efficiency divided by full 4 year survey).

Here is a preview:

 ||<:> ultrasoft ||<:> soft band ||<:> hard band ||
 || {{http://www.mpe.mpg.de/~jbuchner/eROSITA/maps/erosita_eff0.5_ultrasoft_PSF.png|ultrasoft band|width=400}} || {{http://www.mpe.mpg.de/~jbuchner/eROSITA/maps/erosita_eff0.5_soft_PSF.png|soft band|width=400}}  || {{http://www.mpe.mpg.de/~jbuchner/eROSITA/maps/erosita_eff0.5_hard_PSF.png|hard band|width=400}} ||

All background and sensitivity maps are available as FITS files at [[http://www.mpe.mpg.de/~jbuchner/eROSITA/]] under the naming scheme maps/erosita_eff''<efficiency>''_''<band>''_''<area>''.ext. 

== Limitations ==

This computation sidesteps the detection and photon extraction process. I only compute for various areas (FOV 1.03°, 1px, PSF area of (40 arcsec)^2):

   * A spectrum at each RA, DEC (Those background spaxels are available from [[http://www.mpe.mpg.de/~jbuchner/eROSITA/bgspec]])
   * How many photons are expected from the background in each band in this area (background map)
   * Sensitivity (inverse of poisson CDF at probability 1 - 4e-6).

'''Caveat emptor''': I am not overly experienced with xspec and map transformations, so I might have made very basic mistakes. Contact me if you have questions <jbuchner@mpe.mpg.de>.

== Sensitivity/Area curve ==

 ||<:> hard band || {{http://www.mpe.mpg.de/~jbuchner/eROSITA/areacurves_hard.png|hard band area curve|width=500}} ||
 ||<:> soft band || {{http://www.mpe.mpg.de/~jbuchner/eROSITA/areacurves_soft.png|soft band area curve|width=500}} ||

=== Band names ===

 || 'ultrasoft' || 0.2 - 0.5 keV ||
 || 'soft' || 0.5 - 2.0 keV ||
 || 'medium' || 2.0 - 4.5 keV ||
 || 'hard' || 2.0 - 10 keV ||
 || 'uhrd' || 7.5 - 12 keV ||