B. Hußmann1, A. Stolte1, W. Brandner2, M. Gennaro2⋆⋆⋆⋆ and A. Liermann3
1 Argelander Institut für Astronomie, Universität Bonn, Auf dem Hügel 71, 53121 Bonn, Germany
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2 Max-Planck-Institut für Astronomie, Königsstuhl 17, 69117 Heidelberg, Germany
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3 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany
Received: 5 July 2011
Accepted: 14 February 2012
Context. The stellar mass function is a probe for a potential dependence of star formation on the environment. Only a few young clusters are known to reside within the central molecular zone and can serve as testbeds for star formation under the extreme conditions in this region.
Aims. We determine the present-day mass function of the Quintuplet cluster, a young massive cluster in the vicinity of the Galactic centre.
Methods. We use two epochs of high resolution near infrared imaging data obtained with NAOS/CONICA at the ESO VLT to measure the individual proper motions of stars in the Quintuplet cluster in the cluster reference frame. An unbiased sample of cluster members within a radius of 0.5 pc from the cluster centre was established based on their common motion with respect to the field and a subsequent colour-cut. Initial stellar masses were inferred from four isochrones covering ages from 3 to 5 Myr and two sets of stellar evolution models. For each isochrone, the present-day mass function of stars was determined for the full sample of main sequence cluster members using an equal number binning scheme.
Results. We find the slope of the present-day mass function in the central part of the Quintuplet cluster to be α = -1.68+0.13-0.09 for an approximate mass range from 5 to 40 M⊙, which is significantly flatter than the Salpeter slope of α = −2.35. The flattening of the present-day mass function may be caused by rapid dynamical evolution of the cluster in the strong Galactic centre tidal field. The derived mass function slope is compared to the values found in other young massive clusters in the Galaxy.
Key words: Galaxy: center / open clusters and associations: individual: Quintuplet cluster / stars: early-type / infrared: stars / stars: luminosity function, mass function / stars: kinematics and dynamics
Based on observations collected at the ESO/VLT under Program ID 71.C-0344(A) (PI: F. Eisenhauer, retrieved from the ESO archive) and Program ID 081.D-0572(B) (PI: W. Brandner).
Appendices are available in electronic form at http://www.aanda.org
Full Table 4 is available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (126.96.36.199) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/540/A57
© ESO, 2012