An overview of NED's recent content and capabilities, prepared as a handout for the January 2008 AAS meeting in Austin, can be downloaded here (4 MB PDF file).
The most recently updated version of the NED database contains positions, basic data, and over 16,000,000 names for 10,400,000 extragalactic objects, as well as more than 5,000,000 bibliographic references to over 68,000 published papers, and 65,000 notes from catalogs and other publications. NED supports searches for objects and references, and offers browsing capabilities for over 45,000 abstracts of articles of extragalactic interest that have appeared in Astronomy and Astrophysics, AJ, ApJ, MNRAS, and PASP since 1988, in IAU Circulars since 1991, in Publications of the Astronomical Society of Japan, Astronomy Reports, and Astronomy Letters (formerly Soviet Astronomy and Soviet Astronomy Letters) since 1992, in Astrofizika since 1993, in Astronomy and Astrophysics Reviews since 1994, in The Journal of Astronomical Data since 1995, and in New Astronomy since 1996.
Over 40,500,000 detailed photometric measurements, 6,600,000 detailed position measurements, and 6,200,000 detailed diameter measurements, taken from catalogs and the published literature, are currently available through NED. A similar database of over 1.8 million redshift and radial velocity measurements is available, as well as more than 2,300,000 images, most taken from All-Sky release of 2MASS, and from the Digitized Sky Survey (DSS images for all NED objects are available "on-the-fly"). Spectra at all wavelengths for more than 54,000 objects are now available. Also on-line are selected IAU Circulars as well as thesis abstracts of doctoral dissertations on extragalactic topics. Title and abstract searches of the NED literature database can be made by specifying author names. It is also possible to search the main NED database for objects selected by redshift (NED currently has over 1.4 million Basic Data redshifts), in addition to selection by name, by position, or by type (e.g., QSO or infrared source).
If you know that your search will return a large number of objects, you may submit a NED Batch Job, and retrieve the results via ftp at your convenience.
NED's WWW interface allows you to access and search the master list of objects in several ways:
Similarly, you may search for detailed data for a given object. NED currently stores the following data types:
NED also maintains a large collection of references (from 1983 to the present, with many earlier references as well) to literature on extragalactic objects. Abstracts are available for papers published since 1988; and for many theses on extragalactic topics, most more recent than 1980. Catalogue notes are also available.
There are several different ways to search for literature:
NED offers several other services. These currently include:
Finally, there is a list of Frequently Asked Questions (FAQ), with answers, about NED and its various services and features.
We are constantly updating and improving NED, and would very much appreciate hearing from you if you have any comments, suggestions, or questions. You may send comments via e-mail to: NED mail, or you may contact any of the members of the NED group.
Return to beginning of this help page.
Return to NED's home page.
NED's By Name option allows you to search the database for a single object if you know its name. NED recognizes almost all of the names commonly used in extragalactic astronomy. If NED does not recognize a name, it will offer you choices of names it does know about that are similar to the name you typed in.
Back to the Features List.
Return to beginning of this help page.
NED's Near Name is similar to the "By Name" option, but allows you to broaden your search by including a specified area of the sky around your named object. You may specify a search radius up to 300 arcminutes (the default is 5.0 arcminutes).
Back to the Features List.
Return to beginning of this help page.
NED's Near Position option allows a search similar to the "Near Name" search, but here you specify a position on the sky. The default coordinate system is equatorial at the equinox of J2000.0, though you may change this to any equinox between 1500 and 2500, or to ecliptic, Galactic, or supergalactic coordinates. As with the "Near Name" search, you may specify a search radius of up to 300 arcminutes.
Back to the Features List.
Return to beginning of this help page.
NED's IAU Format search allows you to enter a coordinate-based (IAU-style or PKS-like) name, e.g. 0234-37, which NED interprets as an equatorial coordinate. The database is searched around this position and all objects within a certain radius of the position are returned. NED will interpret the position in a "strict" or "liberal" manner; choosing "liberal" searches a larger area of sky.
Back to the Features List.
Return to beginning of this help page.
NED's By Refcode option allows you to retrieve objects from NED using a specific literature reference (for example, all NED objects included in the paper "The Continuum Infrared Emission of AGN" by M.S. Vaceli, S.M. Viegas, R. Grunewald, and P. Benevides-Soares which appeared in PASP 105, 875, 1993,). You may also initiate this search from the "Ref_data" and the "Abs_data" windows that result from reference or abstract searches. In these results windows, clicking on "Retrieve NED Objects" will return a list of extragalactic objects discussed in the paper.
Back to the Features List.
Return to beginning of this help page.
NED's By Parameters lets you retrieve objects from NED by setting various constraints (parameters). Currently available constraints are equatorial and Galactic coordinates, redshift, object type, and catalog name prefix. You may set these constraints individually, or you may combine them. You may also combine object type and name prefix constraints using the "ANY" or "ALL" options (corresponding to logical ORs or ANDs, respectively).
Back to the Features List.
Return to beginning of this help page.
NED's Photometry option allows you to search the database for photometric data for a given object. All the information that you will need to correctly interpret the data is also carried along with the photometry.
Along with the retrieved photometric data for an object, NED provides a spectral energy distribution (SED) plot of those data. The default plot is log f_nu (flux) in Janskys vs. log nu (frequency), though you have options to easily change the units of either axis. You may enlarge any part of the plot, and may also display it with or without labels and/or error bars. You may also download PostScript versions of the SED plot.
As with the "By Name" search, NED will give you various options if it does not recognize the name you type in.
Back to the Features List.
Return to beginning of this help page.
NED's Catalogs option allows you to search several different astronomical catalogs for their data on a given object. The search returns the data as a "snapshot" of the original catalog, reformatted for easy reading on a video monitor. At the moment, you may search the following catalogs:
As with the "By Name" searches, NED will give you various options if it does not recognize the name you type in.
Back to the Features List.
Return to beginning of this help page.
NED's Positions option allows you to search the database for position data from various lists or catalogs for a given object. This provides an easy way to compare positions from different wavelength regimes for the same object. As with the "By Name" search, NED will give you various options if it does not recognize the name you type in.
This option differs from NED's "Near Position" search in that it returns the position data as published, along with all the information from the published source that you will need to usefully interpret the position.
Back to the Features List.
Return to beginning of this help page.
This option allows you to search NED's archive of spectra, and to examine and retrieve the spectra. You may also work with them with Specview, a tool developed by Ivo Busko at STScI. Currently, NED has X-ray, UV, optical, and HI spectra from several different papers.
Back to the Features List.
Return to beginning of this help page.
NED's Redshifts option allows you to search the database for published redshifts or radial velocities for a given object. Currently, NED has optical and HI redshifts from RC3, HMS, LBQS, LCRS, APM, and 75 other surveys and papers.
Back to the Features List.
Return to beginning of this help page.
NED's Diameters option allows you to search the database for published diameters for a given object. Currently, NED has optical, near-infrared, and HI diameters from 2MASS, 2MASS-LGA, RC3, UGC, ESO-B, ESO-LV, MCG, a few radio surveys, and other papers.
Back to the Features List.
Return to beginning of this help page.
Notes from several astronomical catalogs and many papers are included in NED. Among those catalogs presently included are
NED also contains "Essential Notes" (entered by members of the NED team) when the identification, position, redshift, etc. of an object is affected by e.g. an error in a published paper or catalog, confusion by nearby sources, and so forth.
Back to the Features List.
Return to beginning of this help page.
NED's Images option allows you to search the database for published images, or for cutouts from the Digitized Sky Survey, for a given object. While most of the images NED currently has on-line are optical, infrared, and radio images of galaxies, we also collect HI spectra, isophote maps, and other graphical representations of extragalactic data.
For those FITS images that have valid World Coordinate Systems in their
headers, it is also possible to immediately view these images in the
interactive display tools
ALADIN(from CDS) and/or
OASIS
(from IRSA/IPAC).
We gratefully acknowledge the many individuals who have already sent images
in machine-readable formats for integration into NED.
Digitized Sky Survey images in NED
appear courtesy of AURA
/STScI
.
Back to the Features List.
NED's References
option allows you to search the database for references in the
astronomical literature to information about a particular object. You
may also use the "Related Objects" (wildcard) feature which will
return references about all objects with the same root name. For
example, searching for "VV 237" and "Related Objects" returns not only
references concerning just VV 237, but also those about VV 237a, VV
237b, and so on. You may also restrict the search to specific years.
Back to the Features List.
NED's Author Name
option allows searches of the reference database and thesis list
using authors' last names. NED will return references even if the
author requested is not the first author on the paper.
Back to the Features List.
NED's Text Search
page allows you to search for words -- single or in Boolean combinations
-- that occur in NED's literature and thesis abstracts, or in the LEVEL 5
Extragalactic Knowledgebase. The search returns a list of NED or LEVEL 5
files that contain your search string.
Back to the Features List.
LEVEL 5
brings together in a single gateway WEB site (where copyrights allow)
"original" documents and reviews, and/or electronic links to articles of
current and lasting interest to cosmologists, particle physicists, and
extragalactic astronomers.
LEVEL 5 is a hyperlinked document, providing multiple paths to information,
presented at a variety of levels of complexity: from simple definitions up
to essays, recent research articles, detailed monographs, and extensive
reviews. Within each of these articles, the individual extragalactic objects
cited in the text are cross-linked to the NED Basic Data frames, and similarly
all available citations are hyperlinked to
NASA's Abstract
Data Service (ADS) or to
ASTRO-PH,
in some important cases prior to publication. Tabular Data,
images, and graphs are also provided and are being progressively linked to and
from essays and review articles.
Back to the Features List.
LEVEL 5's Glossary and Lexicon is a compilation and
modern updating of terms culled from the published literature. It is designed
to cover all of astronomy, and is in this sense a slight departure from the
extragalactic nature of the rest of NED and LEVEL 5. It has been compiled
from twenty different sources, and has appropriate links to LEVEL 5 articles.
Back to the Features List.
Use NED's Abstracts
option if you want to read the abstract of a specific
article, or if you simply want to keep up with the extragalactic
literature in your favorite journal. You may currently search within
any of the following journals:
NED currently has abstracts from 1988 to the present for A&A, A&AS, AJ,
ApJ, ApJS, MNRAS, and PASP; from 1991 for IAUC; from 1992 for PASJ, ARep,
and AstL; from 1993 for Afz; from 1994 for A&ARv; from 1995 for JAD; and
from 1996 for NewA.
Within those years, you may constrain your search to a given year,
volume number (NED displays the relevant volume numbers for the year
you specify), or even a specific page number if you have it at hand.
You may also choose to search only the Letters (or pink pages) sections
of the journals.
Back to the Features List.
You may use NED's
Thesis Abstracts
option to search for abstracts of theses on
extragalactic topics.
This option supports thesis searches by year ranges as well as
by author name. Thesis searches may also be done with the
"Author Name" option.
Back to the Features List.
NED's Coordinate and
Extinction Calculator
is an easy-to-use coordinate transformation, precession, and position
angle calculator. It also returns the
foreground Galactic extinction (following
Schlegel et al. (ApJ 500, 525, 1998).
The calculator is flexible enough
to convert accurately between Besselian and Julian equinoxes, taking the epoch
of observation into account when needed. Unless you override the defaults,
the calculator assumes that Besselian dates
refer to the FK4 system, and that Julian dates refer to the FK5 optical system
(the more recently adopted International Celestial Reference System (ICRS) is
based
on VLBI of compact radio sources; ICRS is consistent with FK5 to within the
errors of the optical system).
Back to the Features List.
Most redshifts for extragalactic objects are published as "heliocentric"
redshifts -- that is, the earth's rotational and orbital motions have
been removed from the measured velocity. It is often necessary to
further "correct" the redshifts for other motions: Galactic rotation,
peculiar motion of the Galaxy within the Local Group, and motion
within the reference frame defined by the 3K microwave background radiation.
NED's
Velocity Calculator
enables you to make these corrections as needed. NED has
several pre-defined apex vectors that you may use, or you may input your
own apex vector.
Back to the Features List.
NED is providing these links to outside sites at the specific request of
users and as an additional service to extragalactic researchers in general.
The NED Team has not fully validated any of these calculators, and questions
concerning the algorithms used, their range of application and the precision
of the returned results should be directed to the original Web site creators.
Links to five different Cosmology
Calculators enable you to calculate various cosmological
parameters, or to correct your observations for redshift given a variety of
different input parameters.
Similarly, links to five different
Extinction Calculators enable you to calculate Galactic
extinction by several different methods for almost any position on the sky at
Galactic latitudes greater than about 5 degrees.
Back to the Features List.
Many coordinates for celestial objects are published as rectangular
coordinates referred to a "central" object or position, for example in
a cluster of galaxies. NED's
X/Y Offset to RA/Dec Converter allows you to convert these rectangular
coordinates to equatorial coordinates given the equatorial coordinates for
the reference object. If the object is in NED, its name may be used instead
of the position. Any image scale may be used, rotation of the rectangular
grid can be removed, and rectangular coordinates increasing in any direction
can be accommodated.
Back to the Features List.
NED will also process long lists of objects through its
Batch Job
option (batch job forms are available through that link).
You may use batch jobs to search any of the main data
categories in NED (i.e. Basic Data, References, or Photometry). The
input form is flexible enough that you may do several different
searches from a single form. Currently, the limit on the size of
batch jobs is 3,000 objects. As hardware and network capacities
expand, we expect to be able to raise this limit.
When NED has completed your batch job, you will receive an email
message with information on using FTP to retrieve the results.
Or, using your Web browser, you may click on the FTP option on NED's
home Web page.
Back to the Features List.
You may use
NED's Skyplot
feature to plot the results of your object searches
in several different coordinate systems, at any equinox, and at any scale
you wish. You may also include SAO stars on the plot for reference points.
Skyplot, through the link on NED's home page, is also able to produce
finding charts from data that you provide.
Back to the Features List.
For your convenience, we provide a list of
World Wide Web sites that provide services related to NED.
Back to the Features List.
Return to beginning of this help page.
Searching NED for Literature References by
Object Name
Return to beginning of this help page.
Searching NED by Authors' Names
Return to beginning of this help page.
Text Search on NED Journal Abstracts and Theses,
and the LEVEL 5 Extragalactic Knowledgebase
Return to beginning of this help page.
LEVEL 5 -- A Knowledgebase for Extragalactic Astronomy
and Cosmology
Return to beginning of this help page.
LEVEL 5 Glossary and Lexicon
Return to beginning of this help page.
Abstracts in NED
Return to beginning of this help page.
Searching NED for Theses of Extragalactic
Interest
Return to beginning of this help page.
NED's Coordinate Calculator
Return to beginning of this help page.
NED's Velocity Conversion Calculator
Return to beginning of this help page.
Links to External Cosmology and Extinction-Law
Calculators
Return to beginning of this help page.
NED's Rectangular-to-Equatorial Coordinate
Converter
Return to beginning of this help page.
Running NED Batch Jobs
Return to beginning of this help page.
Skyplot: NED's Finding Chart Generator
Return to beginning of this help page.
Web Links to Related Sites
Return to beginning of this help page.
Return to NED's Home Page.