Photometry of a Galactic field at l = 232, b = -6. The old open cluster Auner 1, the Norma-Cygnus spiral arm and the signature of the warped Galactic Thick Disk

Abstract

We perform a detailed photometric study of the stellar populations in a Galactic Field at l = 232, b = -6 in the Canis Major (CMa) constellation. We present the first U,B,V,I photometry of the old open cluster Auner1 and determine it to be 3.25 Gyr old and to lie at 8.9 kpc from the Sun. In the background of the cluster, at more than 9 kpc, we detect a young population most probably associated to the Norma Cygnus spiral arm. Furthermore, we detect the signature of an older population and identify its Turn Off and Red Giant Branch. This population is found to have a mean age of 7 Gyrs and a mean metallicity of Z = 0.006 . We reconstruct the geometry of the stellar distribution and argue that this older population - often associated to the Canis Major {\it galaxy}- belongs in fact to the warped old thin/thick disk component along this line of sight.

19 pages, 7 eps figures (some degraded), accepted for publication in the Astronomical Journal

References in corpus (3)

• Outer structure of the Galactic warp and flare: explaining the Canis Major over-density
• Spiral structure of the Third Galactic Quadrant and the solution to the Canis Major debate
• The population in the background of open clusters: Tracer of the Norma-Cygnus arm

Cited by in corpus (8)

• Spiral structure in the outer Galactic disk. I. The Third Galactic Quadrant
• Reaffirming the connection between the Galactic stellar warp and the Canis Major overdensity
• VVVX-Gaia Discovery of a Low Luminosity Globular Cluster in the Milky Way Disk
• Modeling the Stellar Populations in the Canis Major Over-Density: the Relation Between the Old and Young Populations
• The thickening of the thin disk in the third Galactic quadrant
• Stellar populations in the Canis Major over-density
• Galactic structure in the outer disk: the field in the line of sight to the intermediate-age open cluster Tombaugh 1
• The nearby Galaxy structure toward the Vela Gum nebula