A chemical and kinematical analysis of the intermediate-age open cluster IC 166 from APOGEE and Gaia DR2

TL;DR

This study provides the first detailed chemical and kinematic analysis of the intermediate-age open cluster IC 166, revealing its likely formation in the Galactic disc and its orbit within the Milky Way.

Contribution

It offers the first high-resolution spectroscopic and kinematic characterization of IC 166, including chemical abundances and orbital parameters, enhancing understanding of its origin and evolution.

Findings

IC 166 has a uniform chemical composition with no significant abundance scatter.

The cluster's orbit is bound to the Galactic plane, indicating a disc origin.

IC 166 likely formed in the Galactic disc, consistent with its orbital properties.

Abstract

IC 166 is an intermediate-age open cluster ($\sim 1$ Gyr) which lies in the transition zone of the metallicity gradient in the outer disc. Its location, combined with our very limited knowledge of its salient features, make it an interesting object of study. We present the first high-resolution spectroscopic and precise kinematical analysis of IC 166, which lies in the outer disc with $R_{GC} \sim 12.7$ kpc. High resolution \textit{H}-band spectra were analyzed using observations from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. We made use of the Brussels Automatic Stellar Parameter (BACCHUS) code to provide chemical abundances based on a line-by-line approach for up to eight chemical elements (Mg, Si, Ca, Ti, Al, K, Mn and Fe). The $\alpha-$element (Mg, Si, Ca and whenever available Ti) abundances, and their trends with Fe abundances have been analysed for a total of 13 high-likelihood cluster members. No significant abundance scatter was found in any of the chemical species studied. Combining the positional, heliocentric distance, and kinematic information we derive, for the first time, the probable orbit of IC 166 within a Galactic model including a rotating boxy bar, and found that it is likely that IC 166 formed in the Galactic disc, supporting its nature as an unremarkable Galactic open cluster with an orbit bound to the Galactic plane.