NASA/IPAC EXTRAGALACTIC DATABASE
Date and Time of the Query: 2019-06-18 T21:23:26 PDT
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For refcode 2004A&A...418...33B:
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Copyright by European Southern Observatory (ESO). Reproduced by permission
2004A&A...418...33B Carbon star survey in the Local Group VIII. Probing the stellar halo of NGC 147 P. Battinelli and S. Demers Received 27 June 2003 / Accepted 12 January 2004 We have imaged a 42' x 28' 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 <I> = 20.31 with {sigma} = 0.40. If we adopt a distance modulus {mu}_0_ = 24.39, 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 <M_I>_ = -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 +/- 0.1' and a tidal radius r_t_ = 33.9 +/- 2.4', 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 C/M 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 C/M 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. Keywords: galaxies: individual: NGC 147, galaxies: stellar content, galaxies: structure
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