Atomic Data Needs in Astrophysics: The Galactic Center “Scandium Mystery”

Abstract

Investigating the Galactic center offers unique insights into the buildup and history of our Galaxy and is a stepping stone to understand galaxies in a larger context. It is reasonable to expect that the stars found in the Galactic center might have a different composition compared to stars found in the local neighborhood around the Sun. It is therefore quite exciting when recently there were reports of unusual neutral scandium, yttrium, and vanadium abundances found in the Galactic center stars, compared to local neighborhood stars. To explain the scandium abundances in the Galactic center, we turn to recent laboratory measurements and theoretical calculations done on the atomic oscillator strengths of neutral scandium lines in the near infrared. We combine these with measurements of the hyper fine splitting of neutral scandium. We show how these results can be used to explain the reported unusual scandium abundances and conclude that in this respect, the environment of the Galactic center is not that different from the environment in the local neighborhood around the sun.

A Wide Metallicity Range for Gyr-old Stars in the Nuclear Star Cluster

“…The effective temperature, T eff , has already been determined by Nishiyama et al (2016), and is included in Table 1 under the column T eff,N16 . We also employ the method developed by Thorsbro et al (2020) to derive T eff using the high temperature sensitivity of the scandium lines arising from the 3d 2 4 s-3d4s4p transition (Thorsbro et al 2018;Thorsbro 2020). The effective temperature determined using this method is included in Table 1 under the column T eff,Sc .…”