ISO related formulae

ISO Related Formulae


Note: for reasons obvious to those who know me, these pages will mostly contain ISOCAM information

One important point to remember is that the whole photometric system of CAM rests on the spectral shape convention that incoming flux densities are such that:


So what will you find on this page? here is the list of topics


Sensitivity factors

Conversion of detector units into physical ones, i.e. mJy per pixel, is simply done by dividing the reduced data by a constant value. As listed in the ISOCAM handbook, these factors have varied little since their pre-launch values (the largest variation observed was in fact due to an error in ground-based calibration). For completeness I list in the following table the conversion coefficient, for LW and SW as their appear in Version ## of the document (July 99). If you suspect they could have changed, check the ISOCAM section on the ISO explanatory supplement.

FilterReference WavelengthaConversion Factorrms
LW14.50.774.1
LW26.72.323.3
LW314.31.964.8
LW46.00.787.5
LW56.80.357.5
LW67.71.036.4
LW79.61.336.7
LW811.30.785.4
LW914.90.652.8
LW1012.04.233.9
SW13.60.414.6
SW23.30.124.9
SW34.50.263.4
SW42.80.302.9
SW54.00.774.8
SW63.70.196.0
SW73.00.164.5
SW84.050.0387.2
SW93.90.0745.8
SW104.60.0922.5
SW114.260.0585.5
a Note that the reference wavelength have changed since the beginning of the mission. These new values are more consistent with the filter shapes and allow direct comparison with PHOT filters.

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Bandwidths of CAM filters

The bandwidth is a crucial when you want to properly compute a luminosity in a filter. Yet, since the filters are not perfectly rectangular (to say the least), deriving their bandwidth requires some computation. Furthermore, given that a spectral shape convention was used you need to compute the bandwidths with the same convention. This is what has been done here, using the filter curves in the ISOCAM cookbook as quantum efficiencies.

FilterBandwidth
 1012Hz
LW114.39
LW216.18
LW36.75
LW48.86
LW53.69
LW67.06
LW76.61
LW82.71
LW92.29
LW10b13.20
bThe LW10 filter is almost equivalent to the IRAS 12 Ám filter that has a bandwidth of 13.48 1012 Hz (see also the IRAS pages on this site).

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