First Hubble Space Telescope observations of the brightest stars in the Virgo galaxy M100 = NGC 4321
As part of both the Early Release Observations from the Hubble Space Telescope and the Key Project on the Extragalactic Distance Scale, we have obtained multiwavelength BVR WFPC2 images for the face-on Virgo cluster spiral galaxy M100 = NGC 4321. We report here preliminary results from those observations, in the form of a color-magnitude diagram for -11,500 stars down to V ~ 27 mag and a luminosity function for the brightest blue stars which is found to have a slope of 0.7, in excellent agreement with previous results obtained for significantly nearer galaxies. With the increased resolution now available using WFPC2, the number of galaxies in which we can directly measure Population I stars and thereby quantify the recent evolution, as well as test stellar evolution theory, has dramatically increased by at least a factor of 100. Finally, we find that stars are present in M100 at the colors and luminosities expected for the brightest Cepheid variables in galaxies.
© 1994 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1994 May 17; accepted 1994 August 17. Support for this work was provided by NASA through grant number 2227-87A from the Space Telescope Science Institute which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5- 26555. B. F. M. was supported in part by the Jet Propulsion Laboratory, California Institute of Technology, under the sponsorship of the Astrophysics Division of NASA's Office of Space Science and Applications. W. L. F.'s work on the extragalactic distance scale is supported in part by NSF grant AST 91-16496. This research has made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, Caltech, under contract with NASA.
Published - 1994ApJ___435L__31F.pdf