NRAO Queries (astroquery.nrao)

Getting started

This module provides access to the NRAO Archive, backed by its Table Access Protocol (TAP) service. It supersedes the module that queried the retired pre-2024 NRAO archive interface. The API follows the ALMA module, on which this implementation is based.

The archive can be queried around a position with query_region:

>>> import astropy.units as u
>>> from astropy.coordinates import SkyCoord
>>> from astroquery.nrao import Nrao
>>> coordinates = SkyCoord(187.27791 * u.deg, 2.05238 * u.deg)
>>> result = Nrao.query_region(coordinates, radius=3 * u.arcmin, maxrec=5)
>>> print(result['project_code', 'instrument_name', 'target_name'][:5])
project_code instrument_name target_name
------------ --------------- -----------
     13B-318            EVLA       3C273
     ...

or by object name (resolved with from_name) with query_object:

>>> result = Nrao.query_object('3C273', maxrec=5)

General queries combining any of the supported constraints can be run with query:

>>> result = Nrao.query({'source_name': 'L1157', 'band_list': ['Q', 'K']},
...                     maxrec=5)

The list of supported query keywords is printed by help:

>>> Nrao.help()

Advanced queries

The underlying TAP service accepts ADQL queries against the tap_schema.obscore table through query_tap:

>>> result = Nrao.query_tap(
...     "select top 5 obs_id, project_code, proprietary_status "
...     "from tap_schema.obscore where "
...     "CONTAINS(POINT('ICRS',s_ra,s_dec),"
...     "CIRCLE('ICRS',187.27791,2.05238,0.05))=1")

Note that the NRAO TAP server stores s_region as text, so position constraints must use CONTAINS(POINT(...), CIRCLE(...)) rather than INTERSECTS with s_region.

Reference/API

astroquery.nrao Package

NRAO Archive service.

Classes

NraoClass()	Create an instance of BaseVOQuery.
Conf()	Configuration parameters for astroquery.nrao.