Welcome to the new version of CaltechAUTHORS. Login is currently restricted to library staff. If you notice any issues, please email coda@library.caltech.edu
Published March 1997 | Published
Journal Article Open

Stellar Populations in the Dwarf Elliptical Galaxy NGC 147


Deep V and I CCD images in a central and an outer field of the Local Group dwarf elliptical galaxy NGC 147 have been obtained with the Wide Field and Planetary Camera-2 (WFPC2) on board of the Hubble Space Telescope. The color-magnitude diagram shows a number of interesting features, including a well defined red giant branch (RGB), a red horizontal branch (HB), a strong red clump, and a small number of extended asymptotic giant branch (EAGB) stars. A mean distance modulus of (m- M)_0=24.39 is derived based on both the HB and the RGB tip brightness. The metallicity [Fe/H] as determined from the RGB color has a mean value of -0.91 in the central field, and -1.0 in the outer field; and the outer field shows a weak tendency of increasing metallicity with galactocentric radius. A metallicity dispersion is also present in the galaxy, and it shows a clear radial variation in the sense that a larger dispersion is seen at smaller radii. The small population of EAGB stars indicates the presence of intermediate-aged (several Gyr) stars in the galaxy, while the absence of the main sequence stars with M v< 1 shows that star formation ceased at least 1 Gyr ago. The distribution of the EAGB stars indicates that the younger stars are more centrally concentrated than the majority of older stars. A similar age gradient is also implied by the relative distribution of the HB stars, which appear to be more populous at larger radii. These results are considered within the context of theoretical models for the evolution of dwarf elliptical galaxies.

Additional Information

© 1997 American Astronomical Society. Provided by the NASA Astrophysics Data System. Received 1996 August 7; revised 1996 December 10. We would like to thank Abi Saha for useful discussions and for his help with DoPHOT photometry, which allowed us to make an independent check on our photometry based on the DAO/ALLFRAME package. This work has been supported by NASA Contract NAS7-1260 to JPL.

Attached Files

Published - 1997AJ____113_1001H.pdf


Files (1.7 MB)
Name Size Download all
1.7 MB Preview Download

Additional details

August 19, 2023
October 19, 2023