IRSA Queries (astroquery.irsa)

Getting started

This module can has methods to perform different types of queries on the catalogs present in the IRSA general catalog service. All queries can be performed by calling query_region(), with different keyword arguments. There are 4 different region queries that are supported: Cone, Box, Polygon and All-Sky. All successful queries return the results in a Table. We now look at some examples.

Available catalogs

All region queries require a catalog keyword argument, which is the name of the catalog in the IRSA database, on which the query must be performed. To take a look at all the available catalogs:

>>> from astroquery.irsa import Irsa
>>> Irsa.list_catalogs()

{'a1763t2': 'Abell 1763 Source Catalog',
 'a1763t3': 'Abell 1763 MIPS 70 micron Catalog',
 'acs_iphot_sep07': 'COSMOS ACS I-band photometry catalog September 2007',
 'akari_fis': 'Akari/FIS Bright Source Catalogue',
 'akari_irc': 'Akari/IRC Point Source Catalogue',
 'astsight': 'IRAS Minor Planet Survey',
 ...
 ...
 'xmm_cat_s05': "SWIRE XMM_LSS Region Spring '05 Spitzer Catalog"}

This returns a dictionary of catalog names with their description. If you would rather just print out this information:

>>> from astroquery.irsa import Irsa
>>> Irsa.print_catalogs()

wise_allsky_2band_p1bm_frm      WISE Post-Cryo Single Exposure (L1b) Image Inventory Table
wise_allsky_4band_p3as_psr      WISE All-Sky Reject Table
cosmos_morph_col_1              COSMOS Zamojski Morphology Catalog v1.0
wise_prelim_p3al_lod            WISE Preliminary Release Atlas Inventory Table (Superseded)
com_pccs1_100                   Planck PCCS 100GHz Catalog
swire_lhisod                    SWIRE Lockman Hole ISOCAM Deep Field Catalog
...
...
sdwfs_ch1_epoch3                SDWFS Aug '09 DR1.1 IRAC 3.6um-Selected 3x30sec Coadd, epoch 3 (Feb '08)

Queries over a polygon

Polygon queries can be performed by setting spatial='Polygon'. The search center is optional in this case. One additional parameter that must be set for these queries is polygon. This is a list of coordinate pairs that define a convex polygon. The coordinates may be specified as usual by using the appropriate astropy.coordinates object (Again ICRS coordinates may be directly passed as properly formatted strings). In addition to using a list of astropy.coordinates objects, one additional convenient means of specifying the coordinates is also available - Coordinates may also be entered as a list of tuples, each tuple containing the ra and dec values in degrees. Each of these options is illustrated below:

>>> from astroquery.irsa import Irsa
>>> from astropy import coordinates
>>> table = Irsa.query_region("m31", catalog="fp_psc", spatial="Polygon",
... polygon=[coordinates.SkyCoord(ra=10.1, dec=10.1, unit=(u.deg, u.deg), frame='icrs'),
...          coordinates.SkyCoord(ra=10.0, dec=10.1, unit=(u.deg, u.deg), frame='icrs'),
...          coordinates.SkyCoord(ra=10.0, dec=10.0, unit=(u.deg, u.deg), frame='icrs')
...         ])
>>> print(table)

      ra     dec       clon         clat     err_maj ...  j_h   h_k   j_k   id
------- ------- ------------ ------------ ------- ... ----- ----- ----- ---
 10.016  10.099 00h40m03.77s 10d05m57.22s     0.1 ... 0.602 0.154 0.756   0
 10.031  10.063 00h40m07.44s 10d03m47.10s    0.19 ... 0.809 0.291   1.1   1
 10.037  10.060 00h40m08.83s 10d03m37.00s    0.11 ... 0.468 0.372  0.84   2
 10.060  10.085 00h40m14.39s 10d05m07.60s    0.23 ... 0.697 0.273  0.97   3
 10.016  10.038 00h40m03.80s 10d02m17.02s    0.09 ... 0.552 0.313 0.865   4
 10.011  10.094 00h40m02.68s 10d05m38.05s    0.23 ... 0.378 0.602  0.98   5
 10.006  10.018 00h40m01.33s 10d01m06.24s    0.16 ... 0.662 0.566 1.228   6

Another way to specify the polygon is directly as a list of tuples - each tuple is an ra, dec pair expressed in degrees:

>>> from astroquery.irsa import Irsa
>>> table = Irsa.query_region("m31", catalog="fp_psc", spatial="Polygon",
... polygon = [(10.1, 10.1), (10.0, 10.1), (10.0, 10.0)])
>>> print(table)

      ra     dec       clon         clat     err_maj ...  j_h   h_k   j_k   id
------- ------- ------------ ------------ ------- ... ----- ----- ----- ---
 10.016  10.099 00h40m03.77s 10d05m57.22s     0.1 ... 0.602 0.154 0.756   0
 10.031  10.063 00h40m07.44s 10d03m47.10s    0.19 ... 0.809 0.291   1.1   1
 10.037  10.060 00h40m08.83s 10d03m37.00s    0.11 ... 0.468 0.372  0.84   2
 10.060  10.085 00h40m14.39s 10d05m07.60s    0.23 ... 0.697 0.273  0.97   3
 10.016  10.038 00h40m03.80s 10d02m17.02s    0.09 ... 0.552 0.313 0.865   4
 10.011  10.094 00h40m02.68s 10d05m38.05s    0.23 ... 0.378 0.602  0.98   5
 10.006  10.018 00h40m01.33s 10d01m06.24s    0.16 ... 0.662 0.566 1.228   6

Other Configurations

By default the maximum number of rows that is fetched is set to 500. However, this option may be changed by changing the astroquery configuration file. To change the setting only for the ongoing python session, you could also do:

>>> from astroquery.irsa import Irsa
>>> Irsa.ROW_LIMIT = 1000 # value of new row limit here.

Reference/API

astroquery.irsa Package

IRSA Query Tool

This module contains various methods for querying the IRSA Catalog Query Service(CatQuery).

Classes

IrsaClass()
Conf Configuration parameters for astroquery.irsa.