3.3. Photometry

3.3.1. The science products

3.3.1.1. Level 0 to 1: not yet fully-reduced data

The photometry pipeline products are Frames and Simpleimages. The PACS pipeline products, as you would have seen in some of the screenshots in Section 2.4, are multi-layered, these variously including: a BlockTable, Meta data, a Status table, Masks, and various datasets that have been produced by the pipeline.

Table 3.2. The contents of PACS pipeline products

Name What it is / task that made it What product it is found in
signal the flux dataset in units of digital units/pixel Frames
Mask (PDRG) contains all the individual masks / there from the Level0 and added to as pipeline proceeds Frames
BlockTable organisation table of data blocks / created by findBlocks and added to by a few other tasks Frames
Status a table of the status of PACS during the entire observation / there from the Level0 and added to as pipeline proceeds Frames
image the flux dataset in Jy/pixel SimpleImage
coverage a measure of the number of readouts that were used to assign flux to a spatial map pixel. In mappers using photProject, the general level of the coveage values strongly depends on the parameter pixfrac in the task. SimpleImage
error (PDRG) the error dataset SimpleImage
stDev the standard deviation of the projected pixels in JScanam and HPF maps SimpleImage (only JScanam and HPF)
HPF Mask the mask used for high-pass filtering SimpleImage(only for HPF)
naive (PDRG) the naive map of UNIMAP SimpleImage(only for UNIMAP)
gls (PDRG) the map processed with UNIMAP (still contains gls artifacts) SimpleImage(only for UNIMAP)
pgls (PDRG) the final map after removing gls artifacts in UNIMAP SimpleImage(only for UNIMAP)

The methods you will use to access these parts of these products can be found in their PACS DRM entries.

3.3.1.2. Level 2, 2.5 and 3: science-quality data

The photometry pipeline product from Level 2 are Maps. These maps contain the image in Jy/pixel, the coverage, some measure of error plus several mapmaker-related auxiliary. There are two ways to access these layers. The easy way is to right-click on the desired product in the Observation viewer and select Open with→Image Viewer for ArrayDatasets. The other way is to use the Display tool from the command line:

Display(obs.refs["level2_5"].product.refs["HPPCORMAPB"].product["error"].data)

here you need to type in the exact reference to your product. The syntax for this can be taken from Name entry in the table above (e.g. "error" in the example), the level you want to take it from, and the context name from the table above (e.g. HPPCORMAPB in the example).

If your observation is of point sources, e.g. as will usually be the case with mini-map observations of individual stars, the maps at Level 2 are of science quality, however it is recommended to use the Level 2.5 or Level 3 if you can, since these maps have a better S/N (being a combination). For extended sources or large maps, the Level 2 products should not be used for science.