EDP Sciences
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Volume 417, Number 2, April II 2004
Page(s) 479 - 486
Section Extragalactic astronomy
DOI http://dx.doi.org/10.1051/0004-6361:20034272

A&A 417, 479-486 (2004)
DOI: 10.1051/0004-6361:20034272

Carbon star survey of Local Group galaxies

IX. The spheroidal galaxy NGC 185
P. Battinelli1 and S. Demers2

1  INAF, Osservatorio Astronomico di Roma, Viale del Parco Mellini 84, 00136 Roma, Italia
2  Département de Physique, Université de Montréal, CP 6128, Succursale Centre-Ville, Montréal, Québec, H3C 3J7, Canada
    e-mail: demers@astro.umontreal.ca

(Received 2 September 2003 / Accepted 15 December 2003 )

We used the CFH12K wide field camera to survey the carbon star population of NGC 185 using the CN-TiO technique. 145 C stars are identified with a mean $\langle I \rangle = 19.99\pm0.05$, corresponding to $\langle M_I\rangle = -4.41\pm0.05$, a mean luminosity similar to what was recently found for the C star population of NGC 147. The stellar surface density profile of NGC 185 follows a power law with an exponential scale length of 2.53 $\pm$ 0.07 '. The surface density of C stars follows also a power law but with a smaller scale length, $1.56 \pm 0.06$, demonstrating that the intermediate-age population of NGC 185 is more concentrated than its old population. A tidal radius, $r_{\rm t} = 22.5\pm2.2'$ is determined from red giant star counts. The C/M ratio of NGC 185 is $0.17 \pm 0.02$ with no apparent sign of a radial gradient. We compare the carbon star populations of NGC 185 and NGC 147 to conclude that it is unlikely that they form a close pair.

Key words: galaxies: individual: NGC 185 -- galaxies: stellar content -- galaxies: structure

Offprint request: P. Battinelli, battinel@oarhp1.rm.astro.it

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