Sixteen overlooked open clusters in the fourth Galactic quadrant. A combined analysis of UBVI photometry and Gaia DR2 with ASteCA

• Main Authors: Perren, G. I, Giorgi, E. E, Moitinho, A, Carraro, G, Pera, M. S, Vázquez, R. A
• Format: Journal Article
• Language: English
• Published: 26-03-2020
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.2003.12138

A&A 637, A95 (2020) Aims: This paper has two main objectives: (1) To determine the intrinsic
properties of 16 faint and mostly unstudied open clusters in the poorly known
sector of the Galaxy at 270$^\circ-$300$^\circ$, to probe the Milky Way
structure in future investigations. (2) To address previously reported
systematics in Gaia DR2 parallaxes by comparing the cluster distances derived
from photometry with those derived from parallaxes. Methods: Deep UBVI
photometry of 16 open clusters was carried out. Observations were reduced and
analyzed in an automaticway using the ASteCA package to get individual
distances, reddening, masses, ages and metallicities. Photometric distances
were compared to those obtained from a Bayesian analysis of Gaia DR2
parallaxes. Results: Ten out of the 16 clusters are true or highly probable
open clusters. Two of them are quite young and follow the trace of the Carina
Arm and the already detected warp. The rest of the clusters are placed in the
interarm zone between the Perseus and Carina Arms as expected for older
objects. We found that the cluster van den Berg-Hagen 85 is 7.5$\times$10$^9$
yrs old becoming then one of the oldest open cluster detected in our Galaxy so
far. The relationship of these ten clusters with the Galaxy structure in the
solar neighborhood is discussed. The comparison of distances from photometry
and parallaxes data, in turn, reveals a variable level of disagreement.
Conclusions: Various zero point corrections for Gaia DR2 parallax data recently
reported were considered for a comparison between photometric and parallax
based distances. The results tend to improve with some of these corrections.
Photometric distance analysis suggest an average correction of $\sim$+0.026 mas
(to be added to the parallaxes). The correction may have a more intricate
distance dependency, but addressing that level of detail will require a larger
cluster sample.