NASA Extragalactic Database NED
Contents
Background
The NASA/IPAC Extragalactic Database (NED) is built around a master list of extragalactic objects for which cross-identifications of names have been established, accurate positions and redshifts entered to the extent possible, and some basic data collected. Bibliographic references relevant to individual objects have been compiled, and abstracts of extragalactic interest are kept on line. Detailed and referenced photometry, position, and redshift data, have been taken from large compilations and from the literature. NED also includes images from 2MASS, from the literature, and from the Digitized Sky Survey. NED's data and references are being continually updated, with revised versions being put on-line every 2-3 months.
An Extragalactic Database
We emphasize that NED is an extragalactic database. Data and references for Galactic objects may be retrieved from SIMBAD (Set of Identifications, Measurements, and Bibliography for Astronomical Data), maintained by Centre de Données Astronomiques de Strasbourg, France.
Similarly, solar system and planetary data (e.g. for Mars or for Halley's Comet) may be retrieved from NASA's Planetary Data System (PDS) at JPL.
Many of the individual catalogs loaded into NED are available from CDS (Centre données astronomiques de Strasbourg) at the Strasbourg Astronomical Observatory, Strasbourg, France.
Using NED
There are currently three ways to access NED:
- World Wide Web Version
- Batch Mode
- Server Mode
World Wide Web
This is a standard WWW interface which includes access to images of galaxies in various wavebands, and WWW links to many other astronomical data services. It currently supports object searches by name and position, by various parameters, and by reference codes. The extragalactic literature since 1983 (with many earlier entries) may be searched for references to any object, and abstracts for papers published since 1988 are stored on-line. Abstracts of Ph.D. (and a few master's) theses related to extragalactic astronomy are available, and literature searches by authors' names are also supported. Positional, photometric, and spectroscopic data for any NED object may be retrieved directly, as may their entries in selected astronomical catalogs. Return to NED's home page to use the WWW interface.
We have not optimized WWW NED for use with any particular browser. We use HTML 3 whenever possible, with a few extensions from HTML 4 when necessary. We have done this to insure that NED will be accessible by as many of its users as possible. If you experience difficulty using NED with your browser, please check your "Preferences" or "Options" settings for type, color, and font size; or try another browser if possible. If the problem persists, please [ned@ipac.caltech.edu send NED a note] so that we can try to fix the problem.
NOTICE REGARDING AUTOMATED WEB ACCESS TO NED: Automated access to NED's Web (http) services via computer programs and scripts is supported. We encourage such usage over the classic Server Mode (C client library), for reasons explained below. For further information, see "NED for a New Era" (Mazzarella et al. 2007). Specific sample query URLs, which can be accessed via utilities such as wget and curl or from programs written in Perl, Python or Java, can be found in "NED VO Services" (Mazzarella et al. 2008). However, NED's ability to support automated access involving large data volumes or high query rates is limited. Please adhere to the NED Guidelines for Automated Queries. Thank you for your cooperation.
Batch Mode
Batch mode is designed for searches that will return "large" numbers of objects, typically more than a few hundred. Using this mode simply involves submitting to NED via email a "batch form" containing a list of objects or positions, or other parameters (redshift, object type, or name prefix). After the request has been processed, NED will send you a notice by return e-mail, and you may ftp the resulting data files to your own machine. Information and template batch forms are available through the WWW or Interactive Interfaces, or from the following list.
- Batch form templates
- Commented batch job templates
Any of these templates may be used to submit batch jobs. The commented templates are longer, but contain detailed notes on filling out the batch forms.
Server Mode
This mode allows a "client" computer, located anywhere in the world, access to NED. We provide a client library that will allow you to access NED from within your own programs. This library is available upon email request from [ned@ipac.caltech.edu NED's programming group].
Some of the sites currently using NED in server mode include:
- The NASA Astrophysics Data System
- The Space Telescope Science Institute HST Data Archive
- SkyView at NASA/GSFC/HEASARC
- The Canadian Astronomy Data Center
- The European Southern Observatory Space Telescope-European Coordinating Facility Archive
NOTICE REGARDING COMPUTER CLIENT ACCESS VIA THE WEB: Numerous Web services, observation tools and computer programs around the world use the legacy NED "Server Mode" for connectivity to NED. Most often such usage involves the NED "name resolver" (to retrieve the best available coordinates for a source using any of its known cross-identifications), as well as By Name or Near Name (cone search) queries for basic information about objects. The classic Server Mode has been supported for over a decade. However, for the following reasons, we encourage people developing new client applications, or updating old ones, to utilize the modern NED Web services using the available XML/VOTable output format. The legacy C client-server mode is quite limited in the types of queries supported and in the supplied data. For example, all-sky queries to construct samples of objects, redshifts, detailed photometry/SEDs, diameters, images, spectra and literature searches involving keyword filters are only available via Web URLs. Although the basic Server Mode functionality is still supported, it is not being enhanced. Client access via Web URLs provides access to all modern NED services and content, and minimizes problems with local firewalls (since connections are via port 80 rather than port 10011). Also, access is available from any computer language that can retrieve HTTP URLs (not restricted to the C language), and any XML/VOTable parser can be deployed (rather than programming with the custom data structure in the C client library).
NOTICE REGARDING AUTOMATED ACCESS TO NED: The ability of NED to support automated access involving large data volumes or high query rates is limited. Please adhere to the NED Guidelines for Automated Queries. Thank you for your cooperation.
Acknowledging NED
If your research benefits from the use of the NED database, the following acknowledgement in your paper would be appreciated: This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
When citing NED within a paper, the following statement may be inserted as a footnote: The NASA/IPAC Extragalactic Database (NED) is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.
We would also appreciate receiving a preprint or reprint of any publication acknowledging NED. Please send them to NED IPAC, MS 100-22 Caltech Pasadena, CA 91125-2200 USA
