AlfalfaClass¶

class astroquery.alfalfa.AlfalfaClass[source]¶

Bases: BaseQuery

Attributes Summary

`CATALOG_PREFIX`
`FITS_PREFIX`
`PLACEHOLDER`

Methods Summary

`get_catalog`()	Download catalog of ALFALFA source properties.
`get_spectrum`(agc[, show_progress])	Download spectrum from ALFALFA catalogue.
`get_spectrum_async`(agc[, show_progress])	Download spectrum from ALFALFA catalogue.
`query_region`(coordinates[, radius, ...])	Perform object cross-ID in ALFALFA.

Attributes Documentation

CATALOG_PREFIX = 'http://egg.astro.cornell.edu/alfalfa/data/a40files/a40.datafile1.csv'¶

FITS_PREFIX = 'http://arecibo.tc.cornell.edu/hiarchive/alfalfa/spectraFITS'¶

PLACEHOLDER = -999999¶

Methods Documentation

get_catalog()[source]¶

Download catalog of ALFALFA source properties.

Returns:

resultDictionary of results, each element is a masked array.

Notes

This catalog has ~15,000 entries, so after it’s downloaded, it is made global to save some time later.

get_spectrum(agc, show_progress=True)[source]¶

Download spectrum from ALFALFA catalogue.

Parameters:

agcint: Identification number for object in ALFALFA catalog.
asciibool: Download spectrum from remote server in ASCII or FITS format?

Returns:

spectrumHDUList: Spectrum is in hdulist[0].data[0][2]

See also

get_catalog: method that downloads ALFALFA catalog
query_region: find object in catalog closest to supplied position (use this to determine AGC number first)

query_region(coordinates, radius=<Quantity 3. arcmin>, optical_counterpart=False)[source]¶

Perform object cross-ID in ALFALFA.

Search for objects near position (ra, dec) within some radius.

Parameters:

coordinatesstr or astropy.coordinates object: The target around which to search. It may be specified as a string in which case it is resolved using online services or as the appropriate astropy.coordinates object. ICRS coordinates may also be entered as strings as specified in the astropy.coordinates module.
radiusstr or Quantity object, optional: The string must be parsable by astropy.coordinates.Angle. The appropriate Quantity object from astropy.units may also be used. Defaults to 3 arcmin.
optical_counterpartbool: Search for position match using radio positions or position of any optical counterpart identified by ALFALFA team? Keep in mind that the ALFA beam size is about 3x3 arcminutes.
See documentation for astropy.coordinates.angles for more information
about (‘ra’, ‘dec’, ‘unit’) parameters.

Returns:

resultAGC number for object nearest supplied position.

Examples

>>> from astroquery.alfalfa import Alfalfa
>>> from astropy import coordinates as coords
>>> C = coords.SkyCoord('0h8m05.63s +14d50m23.3s')
>>> agc = Alfalfa.query_region(C,'3 arcmin')

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AlfalfaClass¶