findNearestVLBISources

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Reads a VLBI catalog from astrogeo.org and finds all sources within specified radius of the specified target. Downloads the file first, if necessary.

Usage:

au.findNearestVLBISources(radecString, radius=3, catalog='rfc_2014b_cat.txt',
            server='http://asa.alma.cl/sourcecat/xmlrpc', phasecalFluxLimit=0.15,
            checksourceFluxLimit=0.05, ageLimit=30)
Inputs:
  • radecString: various acceptable formats, including '17:20:05.3 -03:20:15' (see help radec2rad for a complete description)
  • radius: search radius (in degrees)
  • server: this is only needed to instantiate the calDatabaseQuery object that holds the catalog parsing logic
  • phasecalFluxLimit: minimum flux required (in Janskys)
  • checksourceFluxLimit: minimum flux required (in Janskys)
  • ageLimit: maximum age (in days) to consider flux measurement current

Returns:
  • a dictionary, keyed by source name, with values equal to the separation (in degrees)

Examples:

1. Example without flux densities

CASA <4>: au.findNearestVLBISources('12:30:00 -19:50:00', 2)
number of VLBI sources  9101
Found 3 sources within 2 degrees
  Out[4]:
{'J1226-1904': 1.1038003580273426,
 'J1232-1836': 1.3887205245946872,
 'J1238-1959': 1.9819660154049168}

2. Example with flux density at 230 GHz

CASA <5>: au.findNearestVLBISources('12:30:00 -19:50:00', 3, 230)
number of VLBI sources  9101
Found 3 sources within 3 degrees
Querying ALMA catalog for flux densities.
The highest flux density object is J1238-1959 with 90.6+-18.3 mJy at 2.0 deg.
  Out[5]:
{'J1226-1904': {'ageDifference': 0,
                'fluxDensity': 0.009157436914833325,
                'fluxDensityUncertainty': 0.0010773455193921558,
                'meanAge': 292,
                'separationDegrees': 1.1038003580273426,
                'spectralIndex': -0.7,
                'spectralIndexUncertainty': 0.2},
 'J1232-1836': None,
 'J1238-1959': {'ageDifference': 0.0,
                'fluxDensity': 0.090572419131667262,
                'fluxDensityUncertainty': 0.018278865452864206,
                'meanAge': 307.0,
                'separationDegrees': 1.9819660154049168,
                'spectralIndex': -0.13444847788140779,
                'spectralIndexUncertainty': 0.039941467673884526}}
-- ToddHunter - 2015-07-24
Topic revision: r3 - 2015-08-02, ToddHunter
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