These summary notes have been lifted from the NED webpages.
NED’s ongoing mission is to provide a comprehensive and easy-to-use, multi-wavelength fusion of fundamental data for all known (cataloged and published) objects beyond the Milky Way.
As new observations are published, they are cross-identified or statistically associated with previous data and integrated into a unified database to simplify queries and retrieval. Note, these high fidelity cross-ids are non-trivial1.
The Data Available
Available data include positions, redshifts, morphological and spectral types, sizes, photometry, images, spectra, distances, diameters, cross-IDs, associations, reference abstracts, and detailed notes.
Derived quantities include Galactic extinction, velocity corrections, Hubble flow distances and scales, cosmological corrections, quick-look luminosities, and spectral energy distributions (SEDs).
Updates to the public database occur approximately every three months after periods of data entry, quality assurance, and testing. Many of the individual catalogs integrated into NED are available from CDS (Centre données astronomiques de Strasbourg)
Links to External Cosmology and Extinction-Law Calculators
There are links to five different Cosmology Calculators enable you to calculate various cosmological parameters and to five different Extinction Calculators enable you to calculate Galactic extinction
Unprocessed Catalog Sources versus NED Objects
Note NED’s Search Objects, With Unprocessed Catalog Sources option allows a search similar to the “Near Position” search, but optionally returns unprocessed catalog sources from very large catalogs that have yet to be cross-matched with NED.
A Status of S (catalog source) indicates an astronomical observation which has not yet been fully integrated into NED’s representation of the hierarchy of the universe.
A Status of O (NED object) indicates a physical thing or a group of things in the universe, or a region of space, which has been cross-identified or associated by NED with one or more vetted catalog sources.
The Status column returned by the Search Objects, With Unprocessed Catalog Sources service indicates the NED processing status.
Note when you return to NED in the future, you may find that some entries previously identified as S have been promoted to O or added as cross-identifications to other entries, due to new runs or refinements of NED’s cross-matching algorithms.
Current Object Counts in NED
Using NED
World Wide Web: Automated access to NED’s Web (http) services via computer programs and scripts is supported.
Batch Mode: designed for searches that will return typically more than a few hundred objects. Using this mode simply involves submitting to NED via email a “batch form” containing a list of objects or positions. When NED has completed your batch job, you will receive an email message with information on using FTP to retrieve the results.
NED will also process long lists of objects through its Batch Job option - the limit on the size of batch jobs is 3,000 objects.
Query Types
Objects can be queried:
- By Name,
- Near Name or
- Near Position (cone search), and
- With Unprocessed Catalog Sources (to include very large catalog sources that are not yet cross-matched with NED objects).
You may specify a search radius of up to 300 arcminutes. (i.e. 5 deg radius)
NED VO/XML Services
NED web services use the HTTP GET protocol whenever possible, with query filters encoded as URL name–value pairs.
Conesearches
To construct a conesearch URL use the format:
http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?search_type=Near+Position+Search&of=xml_main& RA=Value&DEC=Value&SR=Value
Note:
- RA and DEC are in decimal degrees (J2000) and
- SR (search radius) is in degrees.
For example to query objects within 15 arcminute radius around M 83 use the URL:
http://nedwww.ipac.caltech.edu/cgi-bin/nph-objsearch?search_type=Near+Position+Search&of=xml_main& RA=204.253833&DEC=-29.865750&SR=0.25
Results are returned in VO Table XML format.
nph-objsearch
The main search program, nph-objsearch, has a number of options that affect the results.
- of
- The output format option. When set to value xml_all it returns a VOTable containing nested tables (“table of tables”), each containing a specific type of source data.
- Specific data types are also available separately by specification of xml_main (main source table), xml_names (source cross-IDs), xml_posn (source position, with uncertainties when available), xml_basic (Basic Data), and xml_extern (links to External Resources at the source position).
- extend
- extend=no requests data for only the object name specified by objname. extend=yes also returns data for objects associated to the queried objname, for example, H II regions within a galaxy or members of a galaxy group.
nph-datasearch
- search_type
- examples include search_type= Diameters , search_type= Redshifts , search_type= Notes , search_type= Positions
Types of NED Searches
NED will return only 50,000 objects with a Near Position search. Searches that are likely to return more than 50,000 objects are best done with NED Batch Jobs.
Choose the format of your tabular output list:
- preformatted HTML text
- an HTML table of all data for all the returned sources,
- an ASCII bar-separated variable table of the list of sources,
- an ASCII tab-separated variable table of the list of sources,
- an XML table of the list of sources,
- an XML table of the returned source names (cross-identifications),
- an XML table of the returned source positions (equatorial B1950 and J2000, ecliptic B1950 and J2000, Galactic, and supergalactic)
- an XML table of the returned source Basic Data,
- an XML table of the returned source quantities derived from its redshift (if any),
- an XML table of links to external archives and services with data for the returned source,
- an XML table of all data for the returned sources,
Note you can change the way in which redshifts are displayed
Search Objects, With Unprocessed Catalog Sources
This search allows you to search NED’s master list of astronomical objects for entries near a given position.
Search with a List of Positions
WIth near position lists you can cut-and-paste up to 500 positions, one per line, of the object(s) you wish to search for in the “Input List Equatorial J2000 Positions or Object Names” box.
You may choose a search radius up to 30.0 arcsec.
The output you can select includes:
- Identifications
- Basic Data
- Data Counts and Links
- Classifications
- Photometry
- Diameters
-
A galaxy pair resolved at 2 μm may be unresolved at 24 μm. Astrophysics makes sources look different as a function of wavelength; for example, in dusty starburst galaxies, centroids in the IR often do not match those in the UV. In addition, objects reside in a hierarchical Universe: galaxies contain components (AGNs, supernovae, star clusters, HII regions, etc.); galaxies occur in pairs, group and clusters; and clusters string together in superclusters separated by vast voids. ↩