Firstly, a ratio of the apparent magnitude ofĪn object in a 2” aperture and the apparent magnitude in a 3” aperture should be unity for point-like Try and resolve this we considered several alternatives. This is not good, as data points were flung out all over the plots.
Meaning our catalogue would still contain galaxies after the galaxy criterion was applied.įurthermore, many entries in the catalogue had a colour magnitude of +/-99.9 as there is no actualĭata on that colour magnitude. There are many galaxies below the line in figure 1, However, there are a few issues with our method. The equation of the black line was used as the criterion to define stars and galaxies.įigure 2: TOPCAT subsets table for the J-K against B-V plot. Galaxies are the red data points and stars the blue. Figure 1: TOPCAT plot of J-K against B-V. Stars were defined as having a redshift of zero, and an object in the catalogue was classed as a galaxy if it had z>0.1. An example of this is shown below for a J-K against B-V plot. Using the TOPCAT subsets function, the number of galaxies retained and stars lost was found and then used to decide the most effective criterion.
#Topcat leiden software
To find a criterion by which to separate stars and galaxies, we plotted J-K against various combinations of other colour indices on the software TOPCAT. The J-K index can be used to distinguish between stars and galaxies because the redshift of an object effects the apparent magnitude of that object in the J and K filters more significantly than in other filters. J and K are two filters with central wavelengths in the near-infrared. There was also progress in the removal of galaxies from our CFHT CaHK catalogue. Our chiefĮrror analyser is in the process of making a numerical error Python script. However, since many of the errors we will beĭealing with are not symmetrical about the mean, numerical errors will have to be used. A script for analytical error was completed.
Of G-type stars generated by us, and see if we get the same magnitudes out from the script as we In future, we can extend the same script to stars to a distribution A python script to correctly determine the This week, on the coding side of things all was well.
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