EDP Sciences
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Volume 410, Number 3, November II 2003
Page(s) 795 - 801
Section Galactic structure and dynamics
DOI http://dx.doi.org/10.1051/0004-6361:20031286

A&A 410, 795-801 (2003)
DOI: 10.1051/0004-6361:20031286

Carbon star survey in the Local Group

VII. NGC 3109 a galaxy without a stellar halo
S. Demers1, P. Battinelli2 and B. Letarte1

1  Département de Physique, Université de Montréal, CP 6128, Succursale Centre-Ville, Montréal, Québec H3C 3J7, Canada
    e-mail: bruno@astro.rug.nl
2  INAF, Osservatorio Astronomico di Roma Viale del Parco Mellini 84, 00136 Roma, Italia
    e-mail: battinel@oarhp1.rm.astro.it

(Received 4 June 2003 / Accepted 19 August 2003)

We present a CFH12K wide field survey of the carbon star population in and around NGC 3109. Carbon stars, the brightest members of the intermediate-age population, were found nearly exclusively in and near the disk of NGC 3109, ruling out the existence of an extensive intermediate-age halo like the one found in NGC 6822. Over 400 carbon stars identified have $\langle M_I\rangle = -4.71$, confirming the nearly universality of mean magnitude of C star populations in Local Group galaxies. Star counts over the field reveal that NGC 3109 is a truncated disk shaped galaxy without an extensive stellar halo. The minor axis star counts reach the foreground density between 4 ' and 5 ', a distance that can be explained by an inclined disk rather than a spheroidal halo. We calculate a global C/M ratio of $1.75 \pm 0.20$, a value expected for such a metal poor galaxy.

Key words: galaxies: individual: NGC 3109 -- galaxy stellar content -- galaxy structure

Offprint request: S. Demers, demers@astro.umontreal.ca

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