M33_WFM (S0): Catalog of Selected M33 Star Fields (19930508)
FILE: m33_wfm.s0 (100 stars)
CONTENTS: Catalog of Selected M33 Star Fields
DATASET: This file is part of HyperSky dataset M-8 (M8.3), version 19930508 Availability on HyperSky CD-ROM: Vol. 1 (1993)
DESCRIPTION: This file contains a catalog of 100 field stars in four fields (25/field) in the nearby spiral (Sc) galaxy M33. M33 is a Local Group member also known as the Triangulum galaxy and NGC 598; its position is RA=1h 33.9m, Dec=+30 39' (2000). Since M33 is so nearby, so open, and nearly face-on, detailed studies of its structure and composition are easier than similar studies of more distant galaxies.
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 individual catalog objects. A 1-degree HyperSky field scale gives perhaps the best overview of M33. A scale <= 30 arc minutes (30') is suggested to allow adequate separation of catalog objects for easy identification.
Data for m33_wfm.s0 has been extracted from the paper "STELLAR CONTENT OF NEARBY GALAXIES. III. THE LOCAL GROUP GALAXY M33" by Christine D. Wilson, Wendy L. Freedman and Barry F. Madore [Astron. J. 99(1), January 1990].
The paper provides BVRI CCD photometry for selected stars brighter than magnitude 20, in four field (centered on known Cepheids) spread across the face of M33. Each field contains 25 stars, and for each star the paper provides the visual magnitude. For nearly all stars the paper provides one or more of the photometric magnitude difference values B-V (blue-visual), V-R (visual-red) and R-I (red-infrared).
The images used in the paper were obtained at the prime focus of the Canada-France-Hawaii 3.5-meter Telescope in Sept 1987.
For HyperSky users, one potential use of these stars is as comparison stars for M33 novae and supernovae. Note that all stars in this catalog are magnitude 15-19, and will by default be very small on your HyperSky display. If you want to make such star sizes larger when you "zoom-in" your field scale to examine M33, reset your BRIGHT magnitude limit for stars to a value somewhat brighter than that of the brightest star you expect see. For example, set your BRIGHT stellar magnitude limit to anywhere from 10th to 14th magnitude. Once you do this, 15th magnitude stars will be much larger (the faintest stars will still be small). Stellar magnitude limits may be reset using HyperSky menu options. Because stars brighter than your BRIGHT limit will no longer appear on your field display, be sure to reset your BRIGHT limit to its default value before returning to normal field scales.
DATA: The HyperSky datafile contains the following data from the paper:
POSITION: Position accuracies provided in the paper are 0.01 second in RA and 0.1" in Dec. These position accuracies are reduced to 0.1 second in RA and 1" in Dec in the HyperSky file, the maximum accuracy currently storable.
MAG: The magnitude on each star's identification line is the photometric visual magnitude rounded to the nearest 0.1 mag. The full magnitude, to an accuracy of .01, is provided in the comments below the identification line, as discussed below.
TYPE: Normally stellar spectral type appears under "TY". However, no such information is provided in the paper, and so all stellar types are given simply as "--" in the HyperSky file.
IDENTIFICATION: The paper identifies each star by its field number and a sequence letter from a to y (ie, 1-25). HyperSky adheres to this scheme, providing identifications of the form "FieldN:L", where N is a number from 1-4 and L is an upper-case letter from A to Y.
COMMENTS: The comment lines contain the following additional information, provided if available for each star:
* The visual magnitude to the full accuracy of .01 magnitude
* The values B-V, V-R and R-I, each to an accuracy of .01 magnitude