Astrophysical and Structural Parameters, And Dynamical Evolution Of The Open Clusters NGC 1245 And NGC 2099

TL;DR

This study analyzes the astrophysical, structural, and dynamical properties of open clusters NGC 1245 and NGC 2099 using Gaia DR2 and 2MASS data, revealing mass segregation and external perturbation effects.

Contribution

It provides new detailed measurements of cluster parameters and dynamical states, highlighting mass segregation patterns and external influences on these clusters.

Findings

NGC 1245 shows signs of small-scale mass segregation.

NGC 2099 exhibits strong mass segregation with low-mass stars moving outward.

Both clusters are affected by external perturbations due to their large masses and locations.

Abstract

We derive astrophysical and structural parameters of open clusters NGC 1245 and NGC 2099 from 2MASS JHKs and Gaia DR2 photometric / astrometric data bases. Their likely members have been determined from Gaia DR2 proper motion data. Our E(B-V) values (2MASS) are slightly smaller than the literature values, whereas our E(B-V) values (Gaia DR2) agree with the literature within the uncertainties. Their distance moduli/distances and ages are in good coincident with the literature. NGC 1245 has steep negative core mass function slope (MFs) ({\chi}_core=-1.24). Its halo ({\chi}_halo=+0.78) and overall ({\chi}_overall=-0.95) MFs mean that it presents signs of small-scale mass segregation to the outer regions from its core, due to its [{\tau}_rlx (overall),{\tau}_overall ]=[302 Myr,5]. The MFs of NGC 2099 is very negative steep ({\chi}_core=-2.67) in the core, and quite positive steep ({\chi}_halo=+1.41) in the halo. This kind of MF slope steeping from the core to the outskirts indicates that low-mass stars in the core are transferred to the cluster's outskirts, while massive stars sink in the core, because of mass segregation. NGC 2099's flat overall MFs ({\chi}_overall=+0.91) and its {\tau}_overall=8 presents a sign of mass segregation. These OCs with the relatively large masses 8700 Msolar (NGC 1245) and 5660 Msolar (NGC 2099), which locate at RGC > 9 kpc, expose to external perturbations such as tidal effects and shock waves, and they lose their stars in low-proportions.