XMM-Newton Science Analysis System
omdetect (omdetect-5.6) [xmmsas_20060628_1801-7.0.0]
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SourceListFile
The source-list file produced by omdetect contains a list of
the positions of all the detected sources, the parameterizations of their shapes,
their extracted count-rates, and corrected count-rateswhich contain
some of the corrections that are needed to convert the raw rates to the
rates that can be used to compute instrumental magnitutes. To get the fully-corrected
count-rates the user should run ommag to fully process the count-rates
and compute instrumental magnitudes.
- COLUMN NO NAME UNITS DESCRIPTION
- 1 SRCNUM none
- 2 XPOS pixels x-coordinate of
centroided source centre
- 3 YPOS pixels y-coordinate of
centroided source centre
- 4 POSERR pixels error in x and y
centroided position
- 5 RATE counts/sec Total measured source
counts (after background subtraction) within default source extraction aperture
(r=12 un-binned pixels), divided by exposure time.
- 6 RATE_ERR counts/sec
- 7 BACKGROUND_RATE counts/sec Total estimated
background counts (scaled by area ratio, from the background annulus)
within default source extraction aperture, divided by exposure time
- 8 SIGNIFICANCE none source counts /
sqrt(source + 2 * background counts) (i.e. signal-to-noise ratio)
The significances are computed for a radius that is filter-dependent.
For V the radius is 6 unbinned pixels- this radius contains 95.4% of the
total area of the point-spread function. The radii for the other filters have been
computed using this area and the radii are U(6.48), B(6.66), UVW2(8.38),
UVM2(8.41), UVW2(8.72). Filter WHITE is set to 6 pixels.
- 9 CORR_RATE counts/sec Background subtracted
source count rate after extrapolating (if necessary) for the wings of the PSF
where they extend beyond the default extraction aperture, and correcting
for coincidence losses.
Please note that ommag corrects the count-rates for the time-dependent
sensitivity degradatation and also applies the correction factor 1/(1-deadfraction).
- 10 CORR_RATE_ERR counts/sec
- 11 CORR_BACKGROUND_RATE counts/sec BACKGROUND_RATE after
correcting for coincidence losses.
- 12 PSF1_CORR percentage Point-spread function
correction applied to extrapolate the RATE value from measurement aperture area
to the default extraction area of 12 unbinned pixels
- 13 BK_COILOSS Coincidence-loss correction applied
to the raw-background rate (coincidence-loss corrected background count-rate/raw background count-rate)
- 14 SPB_COILOSS Coincidence-loss correction applied
to the total-background rate (coincidence-loss corrected total count-rate/raw total count-rate)
Please note that this correction does not include the factor 1 / (1-deadfraction),
which is applied by ommag.
- 15 NOPIXELS none Number of pixels contained by an
extended source (EFLAG=1). Point-sources (EFLAG=1) will have this value set to zero.
- 16 APERTURE unbinned pixels For point sources
(EFLAG=0), the aperture radius (unbinned pixels) used in the photometry. For
extended-sources (EFLAG=1) this value will be set to NULL.
- 17 FWHM_MAJ arcsecs The full-width-at-half-maximum
of the semi-major axis of the ellipse describing the shape of the source
(computed by moments - Set to NULL if a reliable value couldn't be computed.)
- 18 FWHM_MAJ_ERR arcsecs The computed error of the FWHM_MAJ
- 19 FWHM_MIN arcsecs The full-width-at-half-maximum
of the semi-minor axis of the ellipse describing the shape of the source
(computed by moments - Set to NULL if a reliable value couldn't be computed.)
- 20 FWHM_MMIN_ERR arcsecs The computed error of the FWHM_MIN
- 21 PA degrees The postion-angle (measured
counterclockwise from the x-axis) of the semi-major axis of the ellipse
describing the shape of the source (computed from moments - Set to NULL if a reliable value couldn't be computed.)
- 22 PA_ERR degrees The computed error of the PA
- 23 QFLAG none Source quality flag - Please see below
- 24 CFLAG none Source confusion flag - Please see below
- 25 EFLAG none (source extension flag) Either 0
point-source (none-extended) or 1 extended.
Quality flag settings
- Bit set, integer value, reason
- 0, 1, Source lies above one or more bad pixels
- 1, 2, Source may be affected by a read-out streak
- 2, 4, Source may be affected by a smoke-ring
- 3, 8, Source may be affected by a star diffraction spike
- 4, 16, Very bright source with a strong modula 8 pattern
- 5, 32, Source lies near to a bright source
- 6, 64, Source lies within central enhanced region
For example, a source with a bad pixel and lying on or close to a read-out streak
would have bits 0 and 1 set and thus have a quality flag value of 3.
Confusion flag settings
- Bit set, integer value, reason
- 0, 1, Point source has one or more sources within a radius of 6-12 unbinned pixels
- 1, 2, Point source has one or more sources within a radius of 3-6 unbinned pixels
- 2, 4, Point source lies within a radius of 12 unbinned pixels from an image edge/
or one or more pixels of an extended source are at an image edge
- 3, 8, Point source lies partly or totally within an extended region
For example, a source lying near to an image edge and having a neighbour at a distance
of 10 unbinned pixels would have bits 2 and 1 set and would thus have a confusion flag value of
5.
XMM-Newton SOC/SSC -- 2006-06-28