NVSS query and cross-matching script

[o-smirnov]

Just discussing this with @IanHeywood. He's still seeing flux scale issues, and there's reports of the same problem from some Caracal users. There seems to be some doubt and confusion about the issue in various quarters. Anyway, that's a separate discussion -- what I'd like to see is a reliable diagnostic that we could run routinely with any eligible observation.

Occurs to me that aimfast offers the best base. So, could we have a scipt that, given an image:

• Runs PyBDSF on it

• Queries NVSS to find all suitable sources in the field

• Cross-matches fluxes and plots the results (optionally, correcting for the primary beam using one of our models, if the input image is not already PB-corrected)

There are some subtleties to this, so @IanHeywood let's document and discuss them here.

If we can get this into a state where this is a standard pipeline product (or at least zero-effort to run), we can put a lot more firm ground under our flux scale discussions.

[o-smirnov]

On a related note, what's the quickest to make an LSM from an image? My BDSM-fu is lapsed, so I was hoping someone could give me a quick recipe.

[Athanaseus]

If you have stimela installed then you can spin a pybdsf cab as follows (this should return a model in fits and lsm):

import stimela


INPUT = 'input'
OUTPUT = 'output'
MSDIR = 'msdir'

IMAGE = ''
PIX_THRESH = 10
ISL_THRESH = 5


stimela.register_globals()

recipe = stimela.Recipe('Source Finder', ms_dir=MSDIR)
#JOB_TYPE='singularity', singularity_image_dir=os.environ["STIMELA_PULLFOLDER"])


recipe.add('cab/pybdsm', 'source_finder',
        {
            "filename"        :   "{}:output".format(IMAGE),
            "outfile"            :   "pybdsm_{}".format(IMAGE[:-5]),
            "thresh_pix"     :    PIX_THRESH,
            "thresh_isl"      :    ISL_THRESH,
            "clobber"          :    True,
            "catalog_type" :    "gaul",
        },
            input=INPUT,
            output=OUTPUT,
            label='src_finder:: Sourcery')

recipe.run()

PS: In the upcoming release aimfast will provide this functionality.

[IanHeywood]

Or if you just want a pure* python solution, I still use this function which is based on one that Sphe wrote years ago:

https://github.com/IanHeywood/oxkat/blob/master/tools/identify_dE_directions.py#L17

If you give it a PyBDSF gaul file it should give you a Tigger LSM. Remember to adjust the cluster distance setting if you want the COPART business to make sense. It's being used in a weird way in this script:

https://github.com/IanHeywood/oxkat/blob/master/tools/identify_dE_directions.py#L181

• almost pure, it does assume tigger-convert is available from the command line.

[o-smirnov]

Hmmm, at this stage even getting a .gaul is proving elusive... BDSM is hanging, seemingly forever, on fitting islands. Any idea how to tell it not to fit so hard?