Journal Article

Open cluster survival within the solar circle: Teutsch 145 and Teutsch 146*

C. Bonatto, S. Ortolani, B. Barbuy and E. Bica

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 402, issue 3, pages 1685-1692
Published in print March 2010 | ISSN: 0035-8711
Published online February 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2009.15980.x
Open cluster survival within the solar circle: Teutsch 145 and Teutsch 146*

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Teutsch 145 and Teutsch 146 are shown to be open clusters (OCs) orbiting well inside the solar circle, a region where several dynamical processes combine to disrupt most OCs on a time-scale of a few 108 yr. BVI photometry from the GALILEO telescope is used to investigate the nature and derive the fundamental and structural parameters of the optically faint and poorly known OCs Teutsch 145 and 146. These parameters are computed by means of field-star-decontaminated colour–magnitude diagrams and stellar radial density profiles (RDPs). Cluster mass estimates are made based on the intrinsic mass functions (MFs). We derive the ages 200+100−50 and 400 ± 100 Myr, and the distances from the Sun d= 2.7 ± 0.3 and 3.8 ± 0.2 kpc, respectively, for Teutsch 145 and 146. Their integrated apparent and absolute magnitudes are mV≈ 12.4 and 13.3 and MV≈−5.6 and −5.3. The MFs (detected for stars with m≳ 1 M) have slopes similar to Salpeter's initial mass function. Extrapolated to the H-burning limit, the MFs would produce total stellar masses of ∼1400 M, typical of relatively massive OCs. Both OCs are located deep into the inner Galaxy and close to the Crux–Scutum arm. Since cluster-disruption processes are important, their primordial masses must have been higher than the present-day values. The conspicuous stellar density excess observed in the innermost bin of both RDPs might reflect the dynamical effects induced by a few 108 yr of external tidal stress.

Keywords: open clusters and associations: general; Galaxy: structure

Journal Article.  4538 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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