Vilnius Photometry and Gaia Astrometry of Melotte 105

TL;DR

This study combines Vilnius photometry and Gaia DR2 data to analyze the properties, structure, and kinematics of the heavily reddened star cluster Melotte 105, providing updated estimates of its parameters and orbit.

Contribution

It offers new photometric and astrometric data, resolves previous discrepancies in cluster parameters, and estimates the cluster's metallicity, age, and orbital characteristics.

Findings

Reddening E(B-V) = 0.34 mag from Vilnius photometry.

Distance modulus of 12.85 mag from ZAMS fitting.

Cluster age estimated at 240 +/- 25 Myr.

Abstract

Archival Vilnius CCD photometric observations are presented for the heavily reddened star cluster Melotte 105, resulting in colour-magnitude diagrams and spectral class estimates. There is considerable lack of agreement between studies for reddening, age, and distance for this cluster explaining why the archival data are being made available by this paper. The derived reddening E(B-V =0.34 +/- 0.04 mag and the distance V-M =12.9 +/- 0.3 mag directly from the Vilnius photometry. The Gaia Data Release 2 (DR2) and Vilnius photometric data of the cluster were used to estimate the structural parameters of the cluster, probability of stellar membership in the cluster, the distance modulus and the cluster age. Lack of $Y$ band observations prevented determination of metal abundance. The values of the colour excess and distance module are determined by two different methods (i.e., Q and Zero Age Main Sequence, or ZAMS, methods). A distance modulus of 12.85 +/- 0.07 mag was derived by ZAMS fitting, in good agreement with the above estimate. ZAMS fitting indicates a reddening of 0.403 +/- 0.02 mag, within two sigma of the estimate above. The cluster's metallicity and age are estimated to be 0.24 dex and 240 +/-25 Myr, respectively. The derived mass function is in good agreement with the Salpeter slope. The cluster space velocity components (U, V, W) were determined as (-3.90 +/- 3.34, -13.76 +/- 5.69, +3.45 +/- 0.41) km/s. Perigalactic and apogalactic distances were obtained as R_{p} = 6.85 and R_{a} = 7.44 kpc respectively. The maximum vertical distance from the Galactic plane was calculated as Z_{max} = 84 pc and the eccentricity of the orbit was determined as e = 0.042.