Sabine Mengel

Dynamical masses of young star clusters in NGC 4038/4039

In order to estimate the masses of the compact, young star clusters in the merging galaxy pair, NGCxa04038/4039 (“the Antennae”), we have obtained medium and high resolution spectroscopy using ISAAC on VLT-UT1 and UVES on VLT-UT2 of five such clusters. The velocity dispersions were estimated using the stellar absorption features of CO at 2.29 μ m and metal absorption lines at around 8500 A, including lines of the Calcium Triplet. The size scales and light profiles were measured from HST images. From these data and assuming Virial equilibrium, we estimated the masses of five clusters. The resulting masses range from 6.5

K-Band Spectroscopy of Compact Star Clusters in NGC 4038/4039

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Imaging the universe in 3D with the VLT: the next-generation field spectrometer SPIFFI

10 5 to 4.7

Westerlund 1: bound or unbound?

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Phase-resolved spectroscopy and photometry of the eclipsing polar EP Draconis (=H1907+690)

10 6

SINFONI: a near-infrared AO-assisted integral field spectrometer for the VLT

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SPIFFI image slicer: revival of image slicing with plane mirrors

. These masses are large, a factor of a few to more than 10 larger than the typical mass of a globular cluster in the Milky Way. The mass-to-light ratios for these clusters in the V - and K -bands in comparison with stellar synthesis models suggest that to first order the IMF slopes are approximately consistent with Salpeter for a mass range of 0.1 to 100

New era of spectroscopy: SINFONI NIR integral field spectroscopy at the diffraction limit of an 8-m telescope

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Dynamical masses of young star clusters in interacting galaxies

. However, the clusters show a significant range of possible IMF slopes or lower mass cut-offs and that these variations may correlate with the interstellar environment of the cluster. Comparison with the results of Fokker-Planck simulations of compact clusters with properties similar to the clusters studied here suggest that they are likely to be long-lived and may lose a substantial fraction of their total mass. This mass loss would make the star clusters obtain masses which are comparable to the typical mass of a globular cluster.

Star Formation in NGC 4038/4039

Integral field spectroscopy in the K band (1.9-2.4 μm) was performed on four IR-bright star clusters and the two nuclei in NGC 4038/4039 (the Antennae). Two of the clusters are located in the overlap region of the two galaxies and together comprise ≈25% of the total 15 μm emission of the total 4.8 GHz emission from this pair of merging galaxies. The other two clusters, each of them spatially resolved into two components, are located in the northern galaxy, one in the western and one in the eastern loop of blue clusters. Comparing our analysis of Brγ, CO band heads, He I 2.058 μm, Hα (from archival Hubble Space Telescope data), and V-K colors to stellar population synthesis models indicates that the clusters are extincted (AV ≈ 0.7-4.3 mag) and young, displaying a significant age spread (4-13 Myr). The starbursts in the nuclei are much older (65 Myr), with the nucleus of NGC 4038 displaying a region of recent star formation northward of its K-band peak. Using our derived age estimates and assuming the parameters of the initial mass function (Salpeter slope, upper mass cutoff of 100 M☉, Miller-Scalo between 1 and 0.1 M☉), we find that the clusters have masses between 0.4 × 106 and 3 × 106 M☉.