NED Frequently Asked Questions -- Nomenclature


  • Q.: What is the meaning of the acronyms used as the catalog prefix in most object names in NED?

    A.: See Source Nomenclature

  • Q.: How do I read that 19-digit REFCODE of yours?

    A.: NED reference codes are 19-character strings of the form:


    Unused characters are padded with dots ".". The fields within the string are as follows:

    YYYYThe four digits of the year of publication
    PUBLNThe journal code, left-justified within the five-digit field
    The codes for those journals regularly entered into NED are:
    A&A..Astronomy and Astrophysics
    A&AS.Astronomy and Astrophysics Supplement Series
    AJ...Astronomical Journal
    ApJ..Astrophysical Journal
    ApJS.Astrophysical Journal Supplement Series
    ARep.Astronomy Reports (formerly Soviet Astronomy)
    AstL.Astronomy Letters (formerly Soviet Astronomy Letters)
    IAUC.IAU Circulars
    MNRASMonthly Notices of the Royal Astronomical Society
    PASP.Publications of the Astronomical Society of the Pacific
    PASJ.Publications of the Astronomical Society of Japan

    VVVVVolume number of the journal, right-justified within the four-digit field
    MTie-breaker code. Where ambiguity is possible (e.g. between the main journal section,
    and the "letters" section of a journal), the following characters or digits in this field break the ambiguity:

    LLetters sections in various journals
    pPink pages in MNRAS (changed to "L" in 1993)
    1, 2, ..., 9,Issue numbers 1 through 0, then "a" through "o", within the same volume of a journal
    0, a, b, c,(e.g. Sky and Telescope, Physics Today)
    ..., o
    A, B, ...Issue designations used by the publisher within the same volume, where each issue starts with page one
    Two or more articles appearing on the same page within a single issue of a journal
    (e.g. Nature, IAU Circulars) are lettered successively beginning with A - Z

    PPPPStarting page number of the article, right-justified
    AFirst letter of the first author's last name, or a ":" when no authors are specified for a reference

    More information on reference codes is available in a paper by members of the NED and SIMBAD groups.

  • Q.: What do the notations like "NED01", "ID", and "NOTES02" mean?

    A.: These are suffixes which we add to a root name to distinguish physically separate objects which do not otherwise carry separate names. For example, UGC 01562 is a double galaxy, but has only one entry in UGC. In order to include both galaxies in NED with unique names, we add the notation "NED01" and "NED02" to "UGC 01562".

    Similarly, we add "NOTES01" to UGC 01562 to refer to a galaxy included only in the UGC Notes for UGC 01562.

    We typically use the "ID" suffix to indicate that a non-optical source (e.g. an infrared source) has been associated with an otherwise unnamed physical object, usually a galaxy. An example is "IRAS 00182+1130". This has been identified as a galaxy, but not given a separate name. The "ID" notation makes it clear that the object has been reclassified from its original type.

    Other suffixes that we use include "COM" for a nearby companion, not necessarily physically connected to the main object (e.g. "3C 227 COM01"), "ABS" for an absorption line system seen along the line of sight to a background object (e.g. "[HB89] 1727+502 ABS01"), and "ARC" for gravitationally-lensed arcs usually found in rich clusters (e.g. "ABELL 0164 ARC01").

  • Q.: I would like to add a table to my paper with a list of background galaxies and their coordinates. What nomenclature should I use?

    A.: The IAU recommendations for nomenclature are presented at the CDS site How to refer to a source or designate a new one. Here is a summary.

    There are three basic categories of names presently in use.

    1. acronym + coordinate-based names
    2. acronym + sequential number
    3. special format

    The "acronym" should be one which makes sense for your program so that future researchers can easily recognize the origin. For example, the acronym could be the last-name initials of the first few authors, or an imaginative scheme to indicate how or why the objects were discovered. You should be sure to clearly define the acronym in your paper. You may also register the acronym with the IAU at the CDS site Proposal for Registering a New Acronym.

    Coordinate-based names may be based on B1950 or J2000 coordinates. If the latter, a "J" must precede the name. For example, a galaxy with J2000 (or ICRS) coordinates of 12h 34m 56.7s, +76d 54m 32s would be given a name like "GALCAT J123456.7+765432". Note that coordinate-based names without a leading "B" or "J" are ALWAYS interpreted as B1950, NOT J2000.

    Whatever name you choose for your objects, it is vital that you include coordinates for the objects to insure that other observers can locate them on the sky. Positional uncertainties are helpful, too.

  • Q.: Some object names have the form "xxx T1-001", but I don't see any T1 in the paper. Where does the "T1" come from?

    A.: There are instances where NED has to create a name for an object, but two or more tables in a reference re-use the sequential numbers. Thus, there is ambiguity between similarly named objects in different tables from the same paper. To provide uniqueness, NED sometimes adds a "T1-", or "A1-" before the number to indicate "Table 1" or "Appendix 1". This is not done for every paper, but if there is a need to differentiate between redundant names, this technique is sometimes used.