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ldetect xray.xspatial.detect



ldetect -- determine source positions from an input qpoe


ldetect qpoe tab cell_size eband


LDETECT runs the detect tasks (CELLMAP, SNRMAP, LPEAKS, BKDEN, and BEPOS) for a single detect cell size and threshold. Intermediate files are saved. An overview of the detect algorithms and implementation is available in the EXPLAIN_DETECT on-line documentation.


qpoe = "" prompt = qpoe file

Name of the input qpoe file.

tab = "" prompt = Output table root

Required output table root. The is specified by supplying the rootname and the intermediate files will use the root in their names. See helps for lpeaks and bepos for for a list of what's included in their tables.

rh_cellsize = "" prompt = ROSAT HRI Cellsize in arcsecs -
                                 6 | 9 | 12 | 24 | 36 | 48
Cellsizes for ROSAT HRI qpoe.

rp_cellsize = "" prompt = ROSAT PSPC Cellsize in arcsecs -
                                 30 [h/b]| 45 [s]| 60 [s/h/b]| 120 [s/h/b]
Cellsizes for ROSAT PSPC qpoe.

eh_cellsize = "" prompt = Einstein HRI Cellsize in arcsecs -
                                 6 | 9 | 12 | 24 | 48
Cellsizes for Einstein HRI qpoe.

ei_cellsize = "" prompt = Einstein IPC Cellsize in arcsecs -
                                  144 [h/b]| 240 [s]
Cellsizes for Einstein IPC qpoe.

eband = "broad" prompt = Energy Band (soft|hard|broad)

Energy band. Prompted when instrument is PSPC or IPC. Choice of Soft, hard, or broad. The PI filter appropriate to the band choice is appended to the qpoe filename. PI bands must be respecified when running BEPOS.

region = "default" prompt=Region Descriptor from which to compute bkden

Required Region from which the background density is computed. If "default" is specified, a default region is defined. The default region is (circle img_cenx img_ceny radius), where radius is the specified bkden parameter below specified in arc-minutes.

(radius = 7.5) [real]

circle radius for default background density region

(fluctuation = 1.0) [real]

Acceptable Fluctuation, F above.

(max_bkiter = 3) [int]

Maximum iterations for computing bkden.

(value = 0.0) [real]

Output parameters. It is the computed background density, from the last run of the task.

(snr_thresh = 2.75) [real]

Minimum SNR threshold for local detect (lpeaks). Sources with computed SNR's below this threshold are thrown out.

(mlsnr_thresh - 3.0) [real]

Minimum SNR threshold for Maximum likelihood determination (bepos). Sources with computed SNR's below this threshold are thrown out.

(prf_sigma = 0.0) [real]

PRF Sigma of the field in arcseconds. When 0.0, the PRF sigma is computed by keying on Telescope, instrument (from input header) & in a PRF lookup table (ldetect.prf_table) and using the coefficients that are returned to compute the PRF.

(energy = 0.0) [real]

Energy (KeV), key look up in PRF coefficients table, coeffs are used to compute the Sigma for a Gaussian Point Response Function.

(prf_table = "xspatialdata$") [string]

PRF coefficients table. Entries for ROSAT PSPC/HRI & Einstein IPC/HRI. Lookup based on value of Returns coefficients assiciated with a default lookup when energy = 0.0, returns coefficients closest to the energy when exact match is not found.

(max_iter = 50) [int]

Maximum iterations for convergence to best positions values.

(max_conf_iterations = 20) [int]

Maximum iterations for confidence error calculations.

(num_conf_lev = 2) [int]

Number of confidence levels that confidence errors are determined for below.

(conf_= 2.3) [real]

The 68 percent confidence level for minimum c-statistic calculation.

(conf_= 4.61) [real]

The 90 percent confidence level for minimum c-statistic calculation.

(refine_limit = 45. ) [real]

Pixel limit between LPEAKS and BEPOS position. When the difference between the 2 positions is greater that this limit the source is thrown out.

(optimum_radius = 1.8) [real]

Factor in calculating the radius of the bin over which we will search for the position. (bin_radius = optimum_radius * src_sigma)

(c_conv_epsilon = 1.0) [real]

Convergence minimum for c-statistic

(s_conv_epsilon = 1.0) [real]

Convergence minimum for source

(cenx_keywd = "CRPIX1") [string]

X center header keyword for off-axis angle calculation

(ceny_keywd = "CRPIX2") [string]

Y center header keyword for off-axis angle calculation

(clobber = no) [boolean]

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

(display = 2) [int]

Display info to screen. Integer of range 0-5. The higher the number more verbose the display.



xp> ldetect 
qpoe file : xdata$rp110590.qp
Output table root: parlac45
ROSAT PSPC Cellsize in arcsecs - 30 [h/b]| 45 [s]| 60 [s/h/b]| 120 [s/h/b]: 45
Energy Band (soft|hard|broad) (broad): soft

... Running Cellmap ...

xdata$rp110590.qp[bl=30,pi=11:41] -> parlac45.imh
add parlac45.imh,cellsize = 45
parlac45.imh updated

... Running Snrmap ...

Convolving 3x3 cells

Convolving 5x5 cells

Calculating Snrmap with equation:


Writing Snrmap Image:

... Running Lpeaks ...

src#  logx    logy     physx     physy    cellx/y     snr

   1  233.00  260.00   6990.00   7800.00   45   45     3.527
   2  232.00  312.00   6960.00   9360.00   45   45    17.798

Writing to Output file:

... Running Bkden ...

Bkden region is circle 256.00 256.00 7.50'

Bkden = 1.1024632 counts/arcmin**2

... Running Bepos ...

*** PI bands must be Respecified with input QPOE ***

Input Qpoe: xdata$rp110590.qp[pi=11:41]
bkden = 1.1024632 (cts/sq arc-min), 0.0000766 (cts/sq pixel)

2 Rough Position(s) Input

 src#      ra            dec       physx    physy  cellcnts framecnts snr
   1    22:08:38.3    45:31:50.5   6996.9   7802.5      32      18     3.4
   2    22:08:41.4    45:44:49.5   6934.5   9360.6    2046    2086    16.8

Writing 2 Sources to Output file:



Documentation giving an overview of the detect package and run order of tasks. (help using_detect )

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

Documentation Match Source task. (help lmatchsrc )

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