NAME

lbmap -- Generate a background and variance map at sub-cell resolution

USAGE

lbmap image outimg

DESCRIPTION

LBMAP generates a background image from an input image of raw counts at the same resolution (the output of cellmap). The image header is checked for instrument, mission, and detect cell size so that the appropriate alpha (integral of the PSF over the detect cell) and beta (integral of the PSF over the detect cell + background cell) are used in computing the the background map. The user may provide their own alpha & beta for cellsizes not defined (outside choices offered in CELLMAP).

These maps are for illustrative purposes only and are not used in other DETECT tasks. The equations used to build the background map use the same algorithms as implemented in bepos.

PARAMETERS

image = "" prompt = Input xray image

Required Input Image at detect subcell resolution. Output of CELLMAP.

outimg = "" prompt = Output bkmap image [root_bkd.imh]

Required Output filename. Background image map at detect subcell resolution.

(alpha = 0.0) [real]

The integral of the PSF over the detect cell. When the value is 0.0 the task defaults to the calibrated value for the Mission/Instrument/ detect cell size of the data.

(beta = 0.0) [real]

The integral of the PSF over the detect cell + background cell. When the value is 0.0 the task defaults to the calibrated value for the Mission/ Instrument/detect cell size of the data.

(clobber = no) [boolean]

Boolean flag specifying whether or not the output Table file can be overwritten, if it already exists.

EXAMPLES

1. Generate a background map data at detect sub-cell resolution.

de> lbmap
Input xray image (output of cellmap): harlac12.imh
Output bkmap image [root_bkd.imh]: harlac12

Assigning Alpha & Beta for ROSAT HRI, cellsize 12"

Convolving 3x3 cells

Convolving 5x5 cells

Calculating a background map with equation:
bmap=(0.867*cell5-0.995*cell3)/(2.77777*0.867-0.995)

Calculating a variance map with equation:
vmap=(0.867**2*cell5+0.995*cell3*(0.995-2*0.867))/(2.77777*0.867-0.995)**2


Writing Background Map:
harlac12_bkd.imh

Writing Variance Map:
harlac12_var.imh

TIME REQUIREMENTS

BUGS

SEE ALSO

Documentation on the detect algorithms and philosophy along with limitations in (help explain_detect ).

Documentation on making an image at detect sub-cell resolution. (previous task to run) (help cellmap )