While the output from the chains is ready for analysis, OM does have some
peculiarities, as discussed in §9.1. While these
usually have only an aesthetic effect, they can also affect source brightness
measurements, since they increase the background. In light of this,
users are strongly encouraged to verify the consistency of the data prior to
analysis. There are a few ways to do this. Users can examine
the combined source list with fv, which will let them see if interesting
sources have been detected in all the filters where they are visible. Users can
also overlay the image source list on to the sky image with implot by
downloading the relevant files to the user's local machine. This can also be done
with ds9 or gaia by using slconv to change source lists
into region files and downloading the relevant files to your local machine.
The task slconv allows users to set the regions radii in arcseconds to a constant
value or scale them to header keywords, such as RATE. By default, ds9 region
files have suffixes of .reg; gaia region files have suffixes of .gaia.
In the example below, we make a region file from the source list for the
mosaicked, V-band sky image.
To make a ds9 region file from a source list with the GUI:
To make a ds9 region file from a source list in the Command Window, type:
We have downloaded the image and region file for examination on a local machine. The mosaicked, V-band sky image, P0123700101OMS000RSIMAGV.FIT, with the region file from slconv overlayed, is shown in Fig. 9.1. There clearly are spurious detections; these can be removed by hand, or by rerunning omichain with a different background-level threshold or source significance.