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For default processing, there will be one table per band and one entry for
each mode of coaddition. If
processing for each individual scan was requested, there will be entries for
each scan as well as the coadded
strings.
For each source, the first page of tabular output will summarize some of the
input parameters. More
information about modified processing is
available.
Each table contains the following columns:
scan- This is the scan number as identified on the scan track plot. The scans
are numbered in the order
they crossed the target. The coadded strings have the following SCAN
numbers:
999 is the weighted mean with weights of 1 or 0.5 (for a few noisy
detectors)
1001 is the straight mean.
1002 is the statistical median, formed at each point, of all the data scans
coadded. If the number of
strings is even, the average of the two middle data values is taken at each
point. The final median string is
Hanning smoothed to reduce high frequency noise.
1003 is the noise-weighted mean string. The weighting factor is
1/SIGMA2, where SIGMA is the
root-mean-square residual on each scan after a baseline is fit to the data
outside the signal range and
subtracted.
x(EW)- The distance in arcminutes between the detector center and target position
along the East-West
axis.
offset- The distance in arcminutes between the detector center and the target
position in the cross-scan
direction.
pa- Scan angle measured in degrees East of North.
sop.obs- Satellite Operations Plan (SOP) and Observation (OBS) numbers for
individual scans. For coadded
data strings SOP = 0 and OBS = total number of data strings coadded.
det- For individual scans, the detector number (see the IRAS Catalogs and
Atlases: Explanatory
Supplement[1988, ed. C.A. Beichman, G. Neugebauer, H.J. Habing, P.E. Clegg
and T.J. Chester, Washington,
DC: GPO]).For coadded data it is the negative of the total number of strings
coadded.
size- The detector size (in arcminutes) cross-scan. It is set to -1 for coadded
data.
sigma- The rms deviation in mJy of the residuals after the baseline
subtraction.
snr- The signal-to-noise ratio (PEAK/SIGMA). This quantity and the next four
are given only if a
plausible signal could be identified by SCANPI.
Otherwise, the words "Improbable Signal Range" appear. To determine if a
real signal exists, the three
highest points within the signal range are identified; if the middle one is the
maximum of the three and the
peak is larger than twice SIGMA, then a plausible source is considered to
exist.
peak- The maximum (in Jy) within the signal range specified.
zero xings- Locations of zero-crossings, X(1), X(2), in arcminutes. The zero crossings
are defined as
he first locations, moving outward from PEAK, where the string crosses the
baseline for one or more
samples.
fnu(z)- An estimate of the total flux density (in Jy) from integration of the
coadded string or scan between
the zero crossings.
fnu(t)- An estimate of the total flux density (in Jy) from integration of the
coadded string or scan between
fixed points defining an integration range. This range is set using the input
parameter SIGLS and defaults to
2, 2, 2.5 and 4 arcminutes at 12, 25, 60 and 100 µm.
w25- The width in arcminutes of the signal at 25% of PEAK.
w50- The width in arcminutes of the signal at 50% of PEAK.
miss- The in-scan deviation of signal peak from the user-specified target
position in arcminutes. The
location of the peak is taken to be the center of the best-fitting template. The
position of signal maximum
is used if no template was fit.
Template amp- The flux density (in Jy) from the best-fitting point source template.
Tmp. corr. coeff.- The correlation coefficient characterizing the best fitting template. It
should be emphasized that this
cannot be compared directly to the correlation coefficients in the IRAS Point
Source Catalog. These
coefficients run much higher, mostly because of the larger number of points
produced by over-sampling. A
typical ``good" point source will have a coefficient greater than 0.995 at an
SNR above 20.
Optional Detailed SCANPI Printout
Optionally setting NOPRNT=0 causes additional detailed information to be
printed, including:
baseline- The polynomial fit for the baseline (Cx2+Bx+A), where the
coefficients are in mJy and x is in
arcminutes.
rms- This is the same as SIGMA in the tabular summary.
background- Background value at input position (same as A in baseline, above)
expressed in MJy/steradian.
total flux- Integrated signal estimates, same as fnu(t) and fnu(z), with the signal
range and zero crossings given
in arcminutes.
width- The full width at various fractional levels.
Coadded/Scan Profile Plots
By default, profile plots are made for the four coadded strings only. The
plots are labeled by scan number
as described under the tabular output. The horizontal axis is distance from the
target position in the
in-scan direction in arcminutes; the vertical axis is flux in
W/m2.
The plot for SCAN 999 shows the interpolated and resampled data with the
baseline left in and the baseline
fit indicated. The other three coadded strings (SCANs 1001, 1002 and 1003) have
the baseline fit subtracted
but indicate the signal range and the background range. All four types of plots
(and the individual scans, if
requested) show the template fit, if a template was successfully fit to the
data.
Summary Plots for Individual Scans
Summary plots are generated only if the option to plot individual scans is
activated. The following
quantities are plotted vs OFFSET (in arcminutes): TEMPLAT AMPL, fnu(Z), and
WIDTH (50%). Measurements from
each scan are represented by a horizontal bar whose size equals the detector
cross-scan size. Measurements on
scan 999 are also shown, with a bar size equal to 1'.
Scan Track Plots
Scan tracks (showing the paths of the detector centers) are plotted for all
the data. These plots are in
the usual astronomical convention, with North up and East to the left. Each scan
is labeled by scan number at
its beginning.
File Output (optional)
The median scans file "spimed" contains the coadded data strings in an ASCII
format. Note that the fluxes
are in DC calibrated W/m2. (See the section on IRAS data
characteristics for more information on the "AC/DC effect".)
In order to get fluxes in Jy from the raw fluxes, you must divide by the
equivalent band pass and apply
the DC to AC correction factor. The correction factors used are listed at the
bottom of the SCANPI tabular
output and are about 1.308, 1.277, 1.060 and 0.98 at 12, 25, 60 and 100 µm.
The equivalent band passes
are (13.48, 5.16, 2.58 and 1.0)x1012 Hz. In addition, when computing
integrated fluxes from the
raw fluxes, the integral must be normalized by the integrated point source
response which is 0.82, 0.844,
1.437, and 3.234.
The summary table files "spisum" are the same as the printed tables.
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