Spectroscopy of globular clusters in the low-luminosity spiral galaxy NGC 45 - AstrophysicsReport as inadecuate

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Abstract: CONTEXT: Extragalactic globular clusters have been studied in ellipticalgalaxies and in a few luminous spiral galaxies, but little is known aboutglobular clusters in low-luminosity spirals.AIMS: Past observations with the ACS have shown that NGC 45 hosts a largepopulation of globular clusters 19, as well as several young star clusters.In this work we aim to confirm the bona fide globular cluster status for 8 of19 globular cluster candidates and to derive metallicities, ages, andvelocities.METHODS: VLT-FORS2 multislit spectroscopy in combination with the Lick-IDSsystem was used to derive velocities and to constrain metallicities andalpha-Fe element ratio of the globular clusters.RESULTS: We confirm the 8 globular clusters as bona fide globular clusters.Their velocities indicate halo or bulge-like kinematics, with little or nooverall rotation. From absorption indices such as H beta, H gamma, and H deltaand the combined MgFe- index, we found that the globular clusters aremetal-poor Z-H<=-0.33 dex and alpha-Fe<=0.0 element ratio. These resultsargue in favor of a population of globular clusters formed during theassembling of the galaxy.

Author: Marcelo D. Mora, Soeren S. Larsen, Markus Kissler-Patig

Source: https://arxiv.org/

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