SHRP_HII (N0): Sharpless Catalog of HII Regions; -40 < Dec (19950125)
FILES:
shrp_hii.n0 (313 HII regions)
shrp_hii.ls (position-list for locating regions)
CONTENTS: Sharpless Catalog of HII Regions; 1959
DATASET: This file comes in HyperSky dataset N-3, version 19950125. Availability on HyperSky CD-ROM: Vol. 2 (1995)
DESCRIPTION: This datafiles contains 313 emission nebulae from the Sharpless Catalog of HII regions, originally published in 1959. The machine-readable version which serves as the basis for the present ADC catalog was obtained from the University of Maryland in 1979. Catalog sky coverage extends no further south than about -40 degrees Declination.
The catalog describes the positions, maximum angular diameters, and classifications according to form, structure, and brightness. It also gives the number of associated stars, which are identified in the published version of the catalog of galactic HII regions. The catalog discriminates what constitutes a separate HII region on the basis of excitation by hot stars.
The HyperSky file is based on the version of the catalog available through the U.S. National Space Sciences Data Center (NSSDC) as Astronomical Data Center (ADC) catalog #7020. It is also available from the Stellar Data Center (CDS), Strasbourg, France, as catalog VII/20.
DATA: The HyperSky datafile contains the following data from the catalog:
POSITION: Right Ascension and Declination are based on the catalog's equinox 1900 coordinates (Lund pole), precessed to equinox 2000. Catalog equinox 1900 positions were provided to an accuracy of 0.1 second in Right Ascension and 1 second in Declination.
MAG: No magnitudes are provided in the Sharpless catalog. For this reason, nebulae in this datafile will cease to appear on your display field if you set the limiting faint magnitude for ".n0" objects brighter than the default. (This is possible only when other nebulae datafiles containing magnitudes are also used.)
IDENTIFICATION: The catalog's Sharpless number, prefixed by "Sh".
COMMENTS: The comment lines contain the following information, provided if available for each HII region:
* A line starting with "dia" giving the maximum angular diameter of the HII region (arc minutes). Owing to the diffuse nature of many of the obects, these diameters may have an uncertainty of the order of 20 percent.
* Following the diameter on the same line, a brief one-word description of the HII region's shape, based on the corresponding catalog code. The description will be one of: {circular, elliptical, irregular}.
* A brief description of the HII region's structure, based on the corresponding catalog code. The description will be one of: {amorphous, amorphous+filamentary, filamentary}
* A brief description of the HII region's brightness, based on the region's appearance on the Palomar Sky Atlas. The description will be one of { faint, intermediate, bright }. Other than this, nothing related to magnitude is provided by the catalog.
* A line giving the number of stars associated with the HII region. The individual stars are given in a subsequent table in the published catalog, but are not in the machine-readable version.
POSITION-LIST: The position-list shrp_hii.ls, if loaded, will enable you locate any one of the catalog HII regions by name.
Remember that this is only a position-list; it does not actually display an object at the position you select. The object you select will appear at the position only if you also load shrp_hii.n0, or some other HyperSky catalog file which contains the object.
REFERENCES Astrophysical Journal Supplement Series, 1959 (number 41, pages 257 - 280)