Ascii version of World Wide Web presentation of the IAU Recommendations for Nomenclature which is based upon LaTex version 1.7 26 January 1995 The latter does not include the Table of Contents but it has some of the text in bold and italics for emphasis. Address comments to: Prof. Helene R. Dickel Chair of the Task Group on Designations of IAU Commision 5 Internet: lanie@astro.uiuc.edu --------------------------------------------------------------------------- Specifications concerning designations for astronomical radiation sources outside the solar system Contents 1. General Recommendations All source listings should always contain positional information and/or a second designation next to a principal designation. 2. Case of existing designations 3. Creation of new designations Acronym Sequence Use of coordinates Specifier Punctuation and special characters Examples Examples of complete designations Examples of improper designations 4. Advice on designations 5. Further information Both latex and DVI versions of this document are accessible by anonymous ftp at node cdsarc.u-strasbg.fr ................................................................................. Specifications concerning designations for astronomical radiation sources outside the solar system Short title: IAU Recommendations for Nomenclature Key words: Designations IAU (version 23 January 1995) A look at the current literature reveals that unclear, ambiguous or confusing designations of astronomical sources of radiation are too often encountered. Therefore, all contributors to databases, and authors of papers, catalogues and surveys, are urged to adhere to the following set of specifications (developed and endorsed by the International Astronomical Union); otherwise significant data may be irretrievably lost. 1. General recommendations All source listings should always contain positional information and/or a second designation next to a principal designation in order to avoid ambiguities that can arise with a single designation. 2. Case of existing designations > When existing designations are used in listings, they should never be altered (e.g., neither truncated nor rounded, nor shortened). > In a publication, the bibliographical reference of the designation should be given. 3. Creation of new designations The designation of an astronomical source should consist of the following parts : Acronym^Sequence^(Specifier) Note that the ^ is used here to denote a blank. It is used for emphasis in showing where spaces occur in a designation. (Users are expected to use an actual blank and not this character.) Parentheses are required if a specifier is included. Acronym and sequence are essential, specifier is optional; the number of blanks may be larger in machine-readable files to right justify numerical or tabular data. The following examples illustrate the recommended form of astronomical designations : NGC^205 PKS^1817-43 CO^J0326.0+3041.0 H2O^G123.4+57.6^(VLSR=-185) 3CR^196 3.1 Acronym The acronym (earlier called origin) is a code (i.e., alphanumerical string of characters) that specifies the catalog or collection of sources. It may be constructed from catalog names (e.g., NGC, BD), the names of authors (RCW), instruments or observatories used (VLA, IRAS, 3C, 51W), etc. The following rules apply to the construction of new acronyms: > an acronym shall consist of at least three characters. > an acronym shall consist of letters and/or numerals only; special characters, including superscripts, subscripts, and blanks should be avoided. > an acronym shall be unique, i.e., the appropriate reference literature (especially the Second Dictionary of Nomenclature --- see below) should be checked to avoid duplication with existing catalog designations, constellation names, abbreviations of source types, etc. > The title of a catalog shall include the acronym by which it is to be known, [e.g., Fifth Fundamental Catalogue (FK5)]. > Avoid excessively long acronyms. Conversely, users shall never abbreviate an acronym. 3.2 Sequence The sequence (or numbering) is an alphanumeric string of characters, normally only numerical, that uniquely determines the source within a catalog or collection. It may be a sequence number within a catalog (e.g., HD^224801), a combination of fields, or it may be based on coordinates. 3.2.1 Use of coordinates Coordinate-based designations are just "names" and should have enough significant figures to unambiguously identify the sources. It is expected that precise coordinates will be provided in the paper (e.g., in a table), accompanied by any needed explanations and other relevant information. If coordinates in any form are used to encode a source of radiation, a set of rules applies, which we will illustrate with a source, namely the QSO with coordinates: (B1950.0) RA = 00h 48m 48.97s DEC = -42deg42' 52.1" (J2000.0) RA = 00h 51m 09.38s DEC = -42deg26' 33.8" > A designation involving only coordinates, often improperly referred to in the in the literature as an "IAU designation", is not sufficient to identify a source unambiguously. An acronym should also be given. > Equatorial coordinates shall always be preceded by J if they are for the new standard equinox of J2000.0 (i.e., IAU 1976 FK5-based, Julian equinox 2000.0 system). They should be preceded by B if they are for the old standard equinox of B1950.0 (i.e., Bessel-Newcomb FK4-based, Besselian equinox 1950.0 system). Galactic coordinates shall be preceded by a G. The absence of code at the beginning of recognizable equatorial coordinates will be interpreted, by default, as a missing B. Ex: QSO^004848-4242.8 = QSO^B004848-4242.8 = QSO^J005109-4226.5 A galactic-based designation is inappropriate for extragalactic sources such as a QSO. Examples of galactic-based designations for sources within the Milky Way Galaxy may be found in section 3 (Ex. H2O) and section 3.5.1 (Ex. PN). > The "flag" letters J, B, and G have a special role : the flag letter should immediately precede the coordinates and should be separated from the acronym by a space (^). This space is particularly important, as there are acronyms ending with J, B, and G. > Coordinates shall contain leading zeroes (in RA and DEC) and the plus or minus sign : +BB.bb or -BB.bb, +DDMMSS.s or -DDMMSS.s > Coordinates shall be specified as LLL.ll+BB.bb or LLL.ll-BB.bb for galactic coordinates, and as HHMMSS.ss+DDMMSS.s or HHMMSS.ss-DDMMSS.s for equatorial coordinates (without spaces); fewer digits may be used as appropriate. Ex: QSO^004848-4242.8 could have been designated by QSO^0048-427 or QSO^0048-42 > Coordinates using an even number of digits (in either RA or DEC), fewer than seven, are expressed in the sexagesimal system. The sequences HHMM.mm or DD.dd where mm and dd are decimal parts of a minute or degree, respectively, should be avoided. If the number of digits is odd and fewer than six, the right-most digit represents a decimal part of hours, degrees or minutes (as, e.g., in the PKS-style HHMM+DDd or in IRAS source designation HHMMm+DDMM) and not tens of minutes or seconds (e.g. the formats HHMMS or +DDM should be avoided). If the number of digits is more than six, the digits in excess of six are decimal parts of seconds of time for RA or of angle for DEC; explicit use of the decimal points is encouraged (e.g. HHMMSS.ss or DDMMSS.s). > Coordinates shall be truncated (not rounded), thus defining a unique (small) field on the sky in which the source is located. The truncation should also operate when the right-most digit represents a decimal part. The right-most digit of the field HHMMm should be computed as m=int(SS/6). The same should be done when transforming from +DDMM to DDd (as in the PKS-style) with d=int(MM/6). Ex: QSO^004848-4242.8 could be named QSO^00488-4242 but not QSO^00484-4242 (wrong truncation of RA) nor QSO^00488-4243 (rounded DEC). > Designations that include coordinates shall be treated as proper names; therefore, they shall not be changed even if the positions change or become more accurately known. Ex: BD^+25^9 stays, even though its declination has now changed to +26 degrees due to precession from its original position (at the 1855 equinox). 3.3 Specifier The specifier is optional and allows one to indicate other source parameters. However, they are not required syntax and are enclosed in parentheses. 3.4 Punctuation and special characters If the designation requires the use of punctuation or special characters, the recommendations are the following : " " (blank character) should be used as separator rather than a ".", or "/". "_" (underscore) may be used in place of a blank, if necessary, such as within an electronic catalog. "-" should be reserved for the minus sign as much as possible. However, if there is no ambiguity with the minus sign, then it may be used as a separator although such useage is discouraged. "." should be reserved for a decimal point. "/" should be used for concatenation of the sources quoted. Ex: DR^21/23 refers to DR^21 and DR^23, not (DR^21, DR^22, DR^23) ":" should be reserved to indicate subdivision (subcomponent). If at some stage subcomponents or multiplicity of sources is recognized, the best designation solution is to name the subcomponents with letters or numerals, which then are added to the sequence with a colon; e.g., NGC^1818:B^12. 3.5 Examples 3.5.1 Examples of complete designations Designation Position Acronym^Sequence^(Specifier) RA(J2000.0) DEC(2000.0) BD^-3^5750 00 02 02.4 -02 45 59 PSR^J1302-6350 13 02 47.72 -63 50 08.5 AC^211^(=1E^2127+119; M^15) 21 30 15.54 +11 43 39.0 PN^G001.2-00.3 17 49 36.9 -28 03 59 R^136:a3^(30^Dor) 05 38 42.4 -69 06 03 The examples in the table above are from pre-existing designations. A look at the "Second Dictionary of Nomenclature" reveals that unique 2-letter combinations for acronyms are nearly exhausted. That is the reason for the change in the rule for new acronyms where at least three characters are now required. Note that "R^136" is a pre-existing designation, and therefore it is not altered when creating the designation for a subcomponent even though "R^136" does not conform to the rules for creating a new acronym. 3.5.2 Examples of improper designations BD^4deg14 use of "deg symbol", declination sign missing N221 no space, unclear source : NGC or N in LMC ? DLB^J204+2 leading zero missing; poor position P^43578 one letter acronym is ambiguous RC^0401+0456 missing flag letter J for Julian 2000 equatorial coordinates, corrected to RC^J0401+0456 in an erratum 4. Advice on designations Advice on specific problems may be obtained from representatives of the "Clearing house", a subset of the Task Group on Designations of IAU Commission 5: H. R. Dickel Astronomy Dept. Univ. of Illinois, 1002 W. Green Street, Urbana, IL 61801-3000, USA Internet: lanie@astro.uiuc.edu Phone (217) 244-7044 Fax (217) 244-7638 P. Dubois Observatoire de Strasbourg 11, rue de l'Universiti F-67000 Strasbourg, FRANCE Internet: dubois@simbad.u-strasbg.fr Phone (33) 88-35-84-37 Fax (33) 88-25-01-60 Telex 890506 Code Starobs NSI/DECnet SIMBAD::DUBOIS W. H. Warren Jr Laboratory for Astronomy and Solar Physics, Code 681 NASA Goddard Space Flight Center Greenbelt, MD 20771, USA Internet: w3whw@gibbs.gsfc.nasa.gov Phone (301) 286-5419 Fax (301) 286-1753 NSI/DECnet STARS:WARREN M.-C. Lortet Observatoire de Paris, 25 place Janssen, F-92195 Meudon Cedex, FRANCE Internet: lortet@mesiob.obspm.fr Phone (33) 1 4507-7414 Fax (33) 1 4507-7469 NSI/DECnet MESIOB::LORTET S. Borde Observatoire de Paris, 61 avenue de l'Observatoire, F-75014 Paris, FRANCE Phone (33) 1 4051-2238 Fax (33) 1 4354-1804 Internet: borde@memaga.obspm.fr J. M. Dickey Univ. of Minnesota Dept. of Astron., 116 Church St. SE Minneapolis, MN 55455 USA Internet: john@ast1.spa.umn.edu Phone (612) 624-2895 Fax (612) 626-2029 H. J. Andernach IUE Observatory, Villafranca Apartado 50727, E-28080 Madrid, FRANCE Internet: heja@vilspa.esa.es Phone (34) 1-8131-110/102 FAX (34) 1-8131-139/119 5. Further information For general information, in particular about existing designations, consult the following references : Lortet, M.-C., Borde, S., Ochsenbein, F. 1994, The Second Reference Dictionary of the Nomenclature of Celestial Objects, A&AS 107, 193 > The complete paper edition appeared as Publication Speciale du C.D.S. 24 Volumes I and II. Observatoire Astronomique de Strasbourg. > Postscript, LaTex or dvi versions available from CDS via anonymous ftp at the Internet node cdsarc.u-strasbg.fr in the directory /pub/dic2, following the procedure described in the Editorial note in A&A 280 E1-E2 Annual Index 1993 > The On-line Dictionary is updated regularly and is available on the free info account installed on the Internet node simbad.u-strasbg.fr (130.79.128.4) or NSI/DECnet node SIMBAD (18099=17.691). Login as "info"; no password is required. > A World-Wide-Web Mosaic access to the "On-line" version is under development; access will be announced in the home pages of the Centre de Donnies de Strasbourg (CDS) at the URL address: http://cdsweb.u-strasbg.fr/CDS.html Fernandez, A., Lortet, M.-C., Spite, F. 1983, The first Dictionary of the Nomenclature of Celestial Objects, A&AS, 52, No 4 Lortet, M.-C., Spite, F. 1986, First Supplement to the First Dictionary of the Nomenclature of Celestial Objects, A&AS 64, 329 Dickel, H. R., Lortet M.-C., de Boer, K. S. 1987, Designation and Nomenclature for Diffuse Radiating Sources , A&AS, 68, 75 Jaschek C. 1989, Data in Astronomy, Cambridge University Press