LWS02
AOT LWS02 (Medium Resolution Line Spectrum and Narrow Band Photometry)
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Raster Map Parameters: A map has N Map Lines (sometimes called Rasters or
Raster Legs). In each Map Line there are M points. The relevant parameters
are:
o Number of Points M o Number of Points N
o Step Size in M o Step Size in N
o Reference Frame o Orientation Angle (0-180)
When Reference Frame=N, the Orientation angle is the standard astronomical
Position Angle, measured CCW to the East from celestial North. When
Reference Frame=Y, Orientation angle=0 and Map Lines are fixed along the
ISO telescope Y-axis. The spacing of points along these Map lines is the
"Step Size in M" in arcseconds. The spacing between the Map Lines is the
"Step Size in N" in arcseconds.
The observer enters up to 10 spectral lines for observation with this AOT
into the table below. The program counts the number of lines for you.
Example inputs are given.
Spectral Continuum Number of Lines: 2
Sampling Flux
Interval |
Line | Scan | Integrated Line Fast -- Requested --
Wavelength | Width | Line Flux Width Scans S/N I.time/Step
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158.611 4 2 8.2 13.4 0.0000 N 16.1 0.0000
63.532 4 2 13.5 10.1 0.0000 N 23.4 0.0000
o Line Wavelength: Between 43.0 and 196.7 If the redshift is > 1
resolution element, the wavelength should be corrected from the rest
wavelength to the source V(helio), Note, a resolution element = 0.29 um for
lambda < 90 um, and 0.60 um for lambda > 90 um.
o Spectral Sampling Interval: The number of spectral samples per spectral
resolution element. (1, 2, 4, or 8). (4 are recommended).
o Scan Width: the number of additional resolution elements to scan on
either side of the central resolution element which is centered at the line
wavelength. (0, 2, 3, or 4). (2 are recommended). For the Narrow Band
Photometry AOT02, set this parameter to zero.
This example will let you figure out how your samples will be arranged
vs. wavelength and how many will be done for LWS02 and LWS04. Suppose
the scan width is 3. There will be 3 resolution elements on
either side of the central one:
X X X X X X X X
wavelength -->
If there are 4 samples per resolution element,
these are filled in like this:
X...X...X...X...X...X...X...X
wavelength -->
Finally, the LWS02 and LWS04 algorithm leaves
the endpoints off:
...X...X...X...X...X...X...
wavelength -->
o Continuum Flux: (Jy) at the line wavelength.
o Integrated Line Flux: (in units of 10^(-17) W/m^2).
o Line Width (in um) (set to 0 if the line is unresolved, which is always
true when the line width is less than 900 km/s).
* Fast scans: Y or N. Always answer YES.
Fast Scanning should alway be used. See notes on
Fast Scanning.
o S/N: This is the signal to noise where the "signal" includes the line
and continuum flux. If S/N[line] is the desired signal to noise on the
line, then S/N = S/N[line] x (C+L)/L, where L and C are the line and
continuum fluxes within the resolution element.
o Int. time/step: This is the fixed integration time per spectral step
(sample). (This may be left zero; only one of the above two parameters must
entered).
If questions, contact: iso@ipac.caltech.edu, or Steve Lord,
lord@heaven.ipac.caltech.edu