VO Simple Cone Search

IRSA's Simple Cone Search (SCS) is a program-friendly service that allows users to search an IRSA catalog for sources within a specified (small) radius of a single search position. This service is compliant with the SCS protocol defined by the International Virtual Observatory Alliance. Users interested in very large search radii, more complex search constraints, or multiple search positions should consider using IRSA's Table Access Protocol (TAP) service.

IRSA's Simple Cone Search Service:

Available Catalogs

All of IRSA's catalogs can be accessed through a SCS query.

Users new to IRSA can explore the available catalogs in IRSA's Catalog Search Tool.

Alternatively, the following URL will give you a list of catalogs in IPAC Table Format:

https://irsa.ipac.caltech.edu/cgi-bin/Gator/nph-scan?mode=ascii

You can paste this URL into a browser window or get the results from the command line using one of the following:

wget -O list_of_catalogs.tbl "https://irsa.ipac.caltech.edu/cgi-bin/Gator/nph-scan?mode=ascii"
curl -o list_of_catalogs.tbl "https://irsa.ipac.caltech.edu/cgi-bin/Gator/nph-scan?mode=ascii"

The table that results will contain a column labeled "catname"; this is the input for the parameter "table" described below.

Base URL

Constructing a query involves creating a query URL that consists of a base URL with appended input parameters. For IRSA's implementation of SCS, the base URL is:

https://irsa.ipac.caltech.edu/SCS?

Input Parameters

There are five input parameters allowed, listed below. Each input parameter is appended to the Base URL as a "parameter=value" pair. That is, the parameter name is followed by an equals sign followed by the value. No extra spaces are allowed. The pairs are separated from each other by ampersands (&).

Parameter Possible Values Default Description Examples
table See "Available Catalogs" above. NA IRSA catalog to search. table=allwise_p3as_psd (AllWISE Source Catalog)

table=fp_psc (2MASS Point Source Catalog)
RA 0 -- 360 NA Right Ascension* in degrees of search region center. RA=250
DEC -90 -- 90 NA Declination* in degrees of search region center. DEC=50
SR 0 -- 1

(Larger values may time out.) 		NA Cone search radius in degrees. SR=0.25
format votable
ipac_table
csv
tsv
fits 		votable Format of the output table (optional). format=ipac_table

*The protocol for VO Simple Cone Searches is for RA and Dec values to be in ICRS coordinates. IRSA catalog RA and Dec values are generally in the system adopted by the catalog provider, usually FK5 for older data and ICRS for newer. Query positions will be interpreted (and results delivered) in the catalog's system. Differences between FK5 and ICRS axes are less than 30 mas, so this should not be a problem for most purposes.

Examples

Command Line

Below are two commands that each query the 2MASS Point Source Catalog ("fp_psc") for all sources within 0.05 degrees of the coordinate RA = 180 degrees, DEC = 0 degrees, and put the output in IPAC Table Format. The only difference is that one uses the curl command and the other uses the wget command.

curl -o out.tbl "https://irsa.ipac.caltech.edu/SCS?table=fp_psc&RA=180.0&DEC=0.0&SR=0.05&format=ipac_table"
wget -O out.tbl "https://irsa.ipac.caltech.edu/SCS?table=fp_psc&RA=180.0&DEC=0.0&SR=0.05&format=ipac_table"

If you choose IPAC Table Format, you can use IRSA's IDL Tools to read the table into an IDL structure.

IDL> .run read_ipac_table.pro
IDL> data_str = read_ipac_table('out.tbl')
IDL> plot,data_str.j_m-data_str.k_m,data_str.k_m,ys=1,
yr=[16,13],psym=4

Python

Python's PyVO is an affiliated package for the AstroPy package, and provides access to IRSA catalogs through the SCS service.

Below is an example showing how to search the 2MASS Point Source Catalog for all sources within 0.05 degrees of the position RA = 180 degrees, DEC = 0 degrees. See the PyVO webpage for more information.

>>>import pyvo
>>>url = "https://irsa.ipac.caltech.edu/SCS?table=fp_psc"
>>>objects = pyvo.conesearch(url, pos=(180, 0), radius = 0.05)
>>>objects.table
>>>objects.fieldnames
>>>objects.getdesc('k_m').description