Volume 418, Number 1, April IV 2004
|Page(s)||33 - 40|
|Published online||02 April 2004|
Carbon star survey in the Local Group*
VIII. Probing the stellar halo of NGC 147
INAF, Osservatorio Astronomico di Roma, Viale del Parco Mellini 84, 00136 Roma, Italia
2 Département de Physique, Université de Montréal, C.P.6128, Succursale Centre-Ville, Montréal, Québec, H3C 3J7, Canada e-mail: firstname.lastname@example.org
Corresponding author: P. Battinelli, email@example.com
Accepted: 12 January 2004
We have imaged a 42 field centered on the spheroidal galaxy NGC 147 to study its AGB population and determine the main structural properties of this M 31 companion. This field was observed through two broadband (R and I) and two narrowband (CN and TiO) filters, following the standard approach of our systematic survey of C stars in nearby galaxies. We identified 288 C stars in NGC 147. The average I-magnitude of such sample of C stars is with . If we adopt a distance modulus , derived from the luminosity of both the tip of the red giant branch (TRGB) and the horizontal branch (HB) by Han et al., we conclude that the average absolute I-magnitude of C stars is = –4.39, thus slightly under luminous with respect to what was found for other galaxies in our survey. From the radial surface profile we derive a scale length of 4.1 ± and a tidal radius rt = 33.9 ± , a value quite larger than previous estimates. The C star population shows a scale length remarkably similar, thus suggesting that intermediate-age stars in NGC 147 are well mixed with the older population. Finally, the overall ratio is 0.24 ± 0.02 and its local values increase monotonically from the center up to 3.5 scale lengths (beyond which counts become too low to yield reliable ratios). Such radial behaviour implies a corresponding decrease of about 0.4 dex in [Fe/H], confirming a well defined metallicity gradient in NGC 147.
Key words: galaxies: individual: NGC 147 / galaxies: stellar content / galaxies: structure
© ESO, 2004
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.