About NED

Vision

The NASA/IPAC Extragalactic Database (NED) aims to capture the most reliable census of extragalactic objects and provide essential data and tools to facilitate astrophysics research and exploration.

Mission

NED accelerates science discovery in astrophysics within NASA's strategic plan by providing a census of extragalactic objects augmented with data joined from across the electromagnetic spectrum for use by the research and lay communities worldwide with access through computer query protocols and user-friendly interfaces. This data synthesis is continually updated by the fusion of fundamental data, prioritizing objects with measured redshifts and distances in refereed publications and major catalogs, and by providing external links to additional data. NED provides its reliable compendium and suite of query tools to support many research areas including spectral energy distributions, statistical studies, and time-domain astronomy.

Guiding Principles

NED increases the science yield from NASA missions with services that help astronomers address the Big Questions in NASA’s strategic plan for astrophysics: (a) "How does the universe work?" (b) "How did we get here?" Answering these questions involves studies of the evolution of the Universe via measuring dark matter and dark energy, tracing the formation and evolution of galaxies along with their supermassive blackholes, capturing the dynamic phenomena of multi-messenger transient events and source variability across all of astrophysics, and many more methods.

Data are being published in astrophysical journals and in large survey catalogs at an ever increasing rate. NED's goal is to assist the research community in making effective and efficient use of a subset of these data that are selected and synthesized with the following guiding principles:

  • Provide one-stop shopping for open science research that benefits from a 3D census of extragalactic objects with their fundamental properties methodically combined from thousands of primary data sources spanning the EM spectrum and joined across NASA astrophysics missions, sky surveys, and journal articles.
  • Facilitate time domain and multi-messenger astronomy (TDAMM) with a synthesis of additional parameters for galaxies in the local Universe as required to optimize rapid follow-up observations to identify the host galaxies of transient events including gravitational waves, gamma ray bursts, and neutrino detections.

Scope of Data Selection

The specific data below will be prioritized for ingestion following the guiding principles above:

  1. Provide a multi-wavelength 3D census of extragalactic objects:
    • Where is it in 3D? This requires coordinates and redshifts, with uncertainties, to cross-match sources and to derive Hubble distances. Catalogs and journal articles with redshift measurements are prioritized above others. Spectroscopic redshifts (spec-z's) are prioritized over photometric redshifts (photo-z's).
    • What is it? Source/object names and basic physical types are captured: galaxy, quasar, pair, group, cluster, etc.
    • How bright is it? Unique photometry in previously unobserved spectral regions are prioritized over redundant measurements, to maximize coverage of the EM spectrum. Global integrated flux measurements or photometry in the largest available aperture are selected over measurements of small-scale features and components.
  2. Facilitate time domain and multi-messenger science: Additional fundamental data are integrated for relatively nearby galaxies to support TDAMM research, focusing on the unique NED Local Volume Sample (LVS) of galaxies with distances D < 1 Gpc (z < 0.23), which is used by the NED Gravitational Wave Follow-up (GWF) service in ranking host galaxy candidates for rapid follow-up of GW events.
    • Distances: Due to 'peculiar velocities' induced by gravitational attraction from nearby galaxies and clusters, redshifts do not provide accurate Hubble distances for galaxies in the Local Group and in galaxy clusters in the local universe. Therefore, NED will ingest distances measured using other methods enabling derivation of reliable physical quantities used to prioritize candidates for the host galaxies of transient events.
    • Additional classifications: In addition to the most basic source/object types captured for all galaxies, activity types (e.g., AGN) will also be ingested.
    • How big is it? Diameters are fundamental structural parameters for galaxies essential to understanding galaxy evolution, merger events, and scaling relations used to derive physical properties such as stellar masses, mean densities, and star formation rates. Diameters are also important for making reliable associations between transient events and their host galaxies.

NED is currently integrating data from the following journals:
Astronomical Journal (AJ), Astrophysical Journal (ApJ), Astrophysical Journal Letters (ApJL), Astrophysical Journal Supplements (ApJS), Astronomy & Astrophysics (A&A), Monthly Notices of the Royal Astronomical Society (MNRAS), and Nature.

Practical limitations to data selection and ingest

Various issues with the presentation of data in many journal articles impede or prevent their efficient integration into NED. Therefore, in addition to focusing on publications that contain the types of data outlined above, we give priority to articles that adhere to Best Practices for Data Publication in the Astronomical Literature (Chen et al. 2022).

Key Functionalities

NED provides a unique object directory and name resolver for distinct extragalactic objects in the Universe and their corresponding sources observed at multiple wavelengths, with links to additional data content in NASA's mission archives, and in complementary catalogs and journal articles. Information about the holdings are provided, including nomenclature, counts and graphical summaries of the current database content, descriptions of how data are integrated into NED, and explanations of NED's processing of large data sets.

NED also provides derived value-added quantities including Galactic extinction estimates, velocity corrections, Hubble flow distances and scales, cosmological corrections, quick-look luminosities, and spectral energy distributions (SEDs).

Objects can be queried by name, near name or near position (cone), or by reference. Galaxy samples can be constructed using joint parameter constraints on sky area, redshift, flux density, etc. More on the usage of NED can be found in the User Guides.

The NED Gravitational Wave Follow-up (GWF) service facilitates searches for electromagnetic (EM) counterparts to gravitational wave events.

NED's data and references are continually updated in an internal production database, and revised versions are released on the public website every few months. New or improved science functionality is also released on a regular basis.

Automated Queries

Automated access to NED web services is supported via application program interfaces (APIs). See Program Interfaces for further information. Please adhere to the Guidelines for Automated Queries as NED's ability to support automated access involving large data volumes or high query rates is limited.

Acknowledging NED

If your research benefits from the use of NED, please include an Acknowledgement.

Last Change: 2025年04月14日