1998/10/29 by Dante Minniti, Albert Zijlstra, Albert A. Zijlstra, +1 · 7 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/300735
Accepted for publication in the Astronomical Journal 23 pages, latex, 12 Figures (Fig 1 not available in electronic format)
arxiv created 1998/10/29 · openalex publication_date 1999/02/01 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We have obtained V - and I -band photometry for about 17,500 stars in the field of the dwarf irregular galaxy NGC 3109, located in the outskirts of the Local Group. The photometry allows us to study the stellar populations present inside and outside the disk of this galaxy. From the VI color-magnitude diagram, we infer metallicities and ages for the stellar populations in the main body and in the halo of NGC 3109. The stars in the disk of this galaxy have a wide variety of ages, including very young stars of age ∼10 7 yr. Our main result is to establish the presence of a halo consisting of Population II stars, extending out to about 4 5 (or 1.8 kpc) above and below the plane of this galaxy. For these old stars we derive an age of over 10 10 yr and a metallicity of [Fe/H] = -1.8 ± 0.2. We construct a deep luminosity function, obtaining an accurate distance modulus ( m - M ) 0 = 25.62 ± 0.1 for this galaxy based on the I -magnitude of the red giant branch tip and adopting E ( V - I ) = 0.05.