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Radio observations of massive stars in the Galactic centre: The Arches Cluster

Gallego-Calvente et al., A&A, 2021

We present high-angular-resolution radio observations of the Arches cluster in the Galactic centre, one of the most massive young clusters in the Milky Way. The data were acquired in two epochs and at 6 and 10 GHz with the Karl G. Jansky Very Large Array. The rms noise reached is three to four times better than during previous observations and we have almost doubled the number of known radio stars in the cluster. Nine of them have spectral indices consistent with thermal emission from ionised stellar winds, one is a confirmed colliding wind binary, and two sources are ambiguous cases. Regarding variability, the radio emission appears to be stable on timescales of a few to ten years. Finally, we show that the number of radio stars can be used as a tool for constraining the age and/or mass of a cluster and also its mass function.

arches_cluster
JHKs false colour image of the Arches cluster from the GALACTICNUCLEUS survey (Nogueras-Lara et al. 2018, 2019a).

 

arches_cluster
Top: closeup onto the Arches cluster from the 2016 X-band image not corrected for primary beam attenuation. The clean beam is 0.48′′×0.18′′,PA=20.84◦. The off-source rms noise level is 2.5 μJy beam−1. The contour levels represent −1, 1, 3, 5, 10, 15, 25, 35, 45, 55, and 60 times the off-source rms noise level multiplied by 5. Bottom: closeup onto the Arches cluster showing most of the detected sources from the 2018 C-band image not corrected for primary beam attenuation. The resolution is 0.62′′×0.28′′, PA=2.82◦. The off-source rms noise level is 4.7 μJy beam−1. The contour levels represent 3, 5, 10, 15, 25, 35, 45, 55 and 60 times the off-source rms noise level multiplied by 3.

Original source
https://www.aanda.org/articles/aa/pdf/2021/03/aa39172-20.pdf