PPMXL and Gaia Morphological Analysis of Melotte 22 (Pleaides) and 25 (Hyades)

TL;DR

This study conducts a detailed morphological, photometric, and kinematic analysis of the open clusters Melotte 22 (Pleiades) and Melotte 25 (Hyades) using Gaia DR2 and PPMXL data, estimating their physical parameters and dynamical states.

Contribution

It provides new estimates of cluster parameters, masses, and kinematic properties, and assesses their dynamical relaxation status using Gaia and PPMXL data.

Findings

Clusters are dynamically relaxed based on relaxation times.

Estimated cluster masses are approximately 662 and 514 solar masses.

Derived kinematic parameters agree with existing literature.

Abstract

In this article, we present a morphological study of the well-known extended sized open clusters in the sky, Melotte 22 (Pleiades) and Melotte 25 (Hyades) with J, H, and Ks regions due to Gaia DR2 and PPMXL catalogues. Based on proper motions of these clusters, we extract our candidates and hence constructing fitting isochrones with Solar metallicity Z = 0.019, log (age) = 8.2 +- 0.05 for Melotte 22, and metallicity Z = 0.024, log (age) = 8.9 +- 0.10 for Melotte 25. Some photometric parameters are estimated, e.g. cluster heliocentric distances are 135 +- 3.6 and 47.51 +- 2.15 pc respectively, luminosity and mass functions with mass-luminosity relation MLR of the second order polynomial, and we have estimated the masses of Melotte 22 and Melotte 25 as 662.476 +- 25.73 Msun and 513.819 +- 22.65 Msun. The relaxation times of these clusters are smaller than the estimated cluster ages, which indicate that these clusters are dynamically relaxed. The second part is devoted to some kinematics of these clusters due to internal and/or motion of members, the apex position is 95.60 +- 0.10, -48.21 +- 0.14 for Melotte 22, and 96.72 +- 1.15, 5.66 +- 0.12 for Melotte 25. Also we have determined the components of space velocity and the cluster centers in pc as well as elements of the Solar motion. The results are in good agreement with those in the literature.