Abstract
Abstract IC 166 is an intermediate-age open cluster (OC) (∼1 Gyr) that lies in the transition zone of the metallicity gradient in the outer disk. 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 disk with R GC ∼ 12.7 kpc. High-resolution H-band spectra were analyzed using observations from the SDSS-IV Apache Point Observatory Galactic Evolution Experiment survey. We made use of the Brussels Automatic Stellar Parameter 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 α-element (Mg, Si, Ca, and whenever available Ti) abundances, and their trends with Fe abundances have been analyzed 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 disk, supporting its nature as an unremarkable Galactic OC with an orbit bound to the Galactic plane.
Highlights
We selected a sample of potential stellar members for IC 166 using the following high quality control cuts: 1. Spatial Location: We focus on stars that are located inside half of the tidal radius, where rt = 35.19 ± 6.10 pc (Kharchenko et al 2012)
We find the orbit of IC 166 lies in the Galactic disk and it appears to be an unremarkable typical Galactic open cluster (OC)
We have presented the first high-resolution spectroscopic observations of the stellar cluster IC 166, which was recently surveyed in the H-band of Apache Point Observatory Galactic Evolution Experiment (APOGEE)
Summary
Galactic open clusters (OCs) have a wide age range, from 0 to almost 10 Gyr, and they are spread throughout the Galactic. Interactions with giant molecular clouds along their orbit in the Galactic disk have a high probability to eventually disrupt star clusters (Lamers et al 2005; Gieles et al 2006; Lamers & Gieles 2006) These effects can lead to the dissolution of a typical OC in ∼108 years (Friel 2013). Intermediate-age and old OCs ( 1.0 Gyr) are rare by nature and are of great interest (Donati et al 2014; Friel et al 2014; Magrini et al 2015; Tang et al 2017) As these effects are generally less severe in the outer disk, OCs there have a higher chance of survival, providing a great opportunity to study this part of the Galaxy both chemically and dynamically.
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