M33_6M (N0): Catalog of M33 HII Regions from Russian 6-meter survey (930506)
FILE: m33_6m.n0 (748 nebulae)
CONTENTS: Catalog of 748 M33 HII Regions from Russian 6-meter survey
DATASET: This file is part of HyperSky dataset M-8 (M8.1), version 19930506 Availability on HyperSky CD-ROM: Vol. 1 (1993)
DESCRIPTION: This file contains an extensive catalog of HII regions in the nearby galaxy M33. M33 is a Local Group member also known as the Triangulum galaxy and as NGC 598. Its position is RA=1h 33.9m, Dec=+30 39' (2000). M33 is a type Sc II-III spiral galaxy. Because it is so nearby, nearly face-on and very open, detailed studies of its structure and composition are more easily done than studies of more distant galaxies. Because the HII regions are closely related to the morphology (form and structure) of M33, use of the HyperSky file reveals hints of the spiral arms of M33 along which many of the HII regions lie.
The HyperSky file for this catalog is a "small-scale" datafile. That is, the file covers only the very small area of the sky occupied by M33. HyperSky treats such small-scale files in a special way: it will display only the outline of the catalog area, NOT its contents, until you reduce the HyperSky field scale appropriately. For this file, you must reduce your HyperSky vertical field scale to 2.7 degrees or less before you can see the individual HII regions. A 1-degree HyperSky field scale gives perhaps the best overview of M33, and shows hints of its spiral structure. A scale <= 30 arc minutes (30') is suggested to allow adequate separation of the many HII regions for easy identification.
Data for m33_6m.n0 has been extracted from a paper in Astronomy and Astrophysics [Astron. Astrophys. 174, 28-56 (1987)] by G. Courtes, H. Petit, J.-P. Sivan, S. Dodonov and M. Petit. The paper is titled: ``H-alpha survey of M33 with the six-meter telescope: morphology of the general diffuse emission, evidence for a chaotic medium of bubbles and filaments.''
The catalog of 748 distinct HII regions (glowing ionized hydrogen gas) was compiled from photographs of a complete H-alpha survey of M33, carried out with the Russian 6-meter telescope of the Soviet Special Astrophysical Observatory in Zelentchuk. The photographs, obtained by using the 6-meter with an f/1 focal reducer, reveal that the "classical" HII regions are embedded within a very chaotic background of H-alpha emission. Rings, loops, and structures shaped like arcs and filaments are present everywhere in M33, both in and between its arms.
This catalog builds on earlier studies of the HII regions in M33, both by the same authors and others. These earlier works include a complete H-alpha survey of M33 by Boulesteix et al (1974) and studies by Lequeux et al (1986). HII region names assigned in these earlier studies are retained here, or noted as appropriate (see below).
DATA: The HyperSky datafile contains the following data from the paper:
POSITION: HII region positions are stored in the HyperSky file for equinox 1950, just as they are provided in the catalog. Position accuracies are 0.1 second RA and 1" Dec, as provided in the paper.
MAG: No HII region magnitudes were provided in the paper.
IDENTIFICATION: The HII region identification number, which will begin with either a B or Z. B-numbers are region numbers assigned in the 1974 study by Boulesteix et al. as mentioned above. Z-numbers are new region numbers assigned by the 6-meter survey catalog. A small number of the HII regions have NGC/IC identifications.
COMMENTS: The comment lines contain the following additional information, provided if available for each HII region:
* Region dimensions, in the general form DxD", where each D is a value in arc seconds.
* Lequeux identifications, from catalog notes.
* Short descriptive remarks ("arc", "bubble", "filament", "loop", etc)