Advanced Topics

Here we describe how to use some selected features of Nemo that are not necessarily covered in the Tutorials.

Forced photometry

Forced photometry is the extraction of flux or SZ-signal measurements at fixed prior positions - i.e., an external catalog is used to supply a list of object positions, instead of using Nemo to detect the objects. Nemo offers two modes in which forced photometry is performed, depending on whether you are interested in performing forced photometry on sources or clusters.

If you have already run the nemo command and produced an output directory containing filtered maps on which you wish to perform cluster photometry, the nemoMass command can be used. For example,:

nemoMass S18d_202003.yml -c externalCatalogChecks/mergeMaDCoWS/MADCOWSUnion.fits

runs nemoMass using the configuration file S18d_202003.yml on the external catalog specified using the -c switch (in this case, externalCatalogChecks/mergeMaDCoWS/MADCOWSUnion.fits, which contains the union of Tables 4, 5, and 6 in the Gonzalez et al. (2019) MaDCoWS galaxy cluster catalog paper). This will extract the SZ signal at the location of each object in the catalog that lies in the filtered map. For objects that have redshift estimates in the catalog, the mass will be estimated using the scaling relation parameters given in the configuration file (S18d_202003.yml in this example). By default, nemoMass will look for a column named redshift, but a few possible variations are detected, e.g., Photz, as in this example. You can also specify the name of the redshift column using the -z switch.

The output will be written to a file with the same name as the catalog specified by the -c switch, but with _M500.fits appended (externalCatalogChecks/mergeMaDCoWS/MADCOWSUnion_M500.fits for the example above). One could perform a stacking analysis to look at, e.g., mass versus richness, by binning and averaging the fixed_y_c values in the output file and feeding the resulting catalog through the nemoMass script.

Alternatively, forced photometry can be performed by the main nemo command. In this case, the path to the catalog that provides the object prior positions is given by the forcedPhotometryCatalog key in the nemo configuration file. Forced photometry on sources of any kind can be done using this method.

Making model images

The nemoModel script can make model images from a Nemo catalog. If run using MPI, it will break the map into tiles to speed up processing, based on the given mask file. For example,:

mpiexec nemoModel S18d_202003_test/S18d_202003_test_optimalCatalog.fits maps/Mar2020/AdvACTSurveyMask_v7_S18.fits Beams/190809/b20190809_s16_pa2_f150_nohwp_night_beam_profile_jitter_cmb.txt testModel_f150.fits -f 149.6 -M

will make a model image over the whole AdvACT footprint.

Using the selection function

Using the selection function…

Modifying GNFW parameters

How to do…

Source injection and flux recovery tests

Refer to examples…