Discovery and astrophysical properties of Galactic open clusters in dense stellar fields using Gaia DR2

Abstract

<jats:title>ABSTRACT</jats:title> <jats:p>We report the discovery of 25 new open clusters resulting from a search in dense low Galactic latitude fields. We also provide, for the first time, structural and astrophysical parameters for the new findings and 34 other recently discovered open clusters using Gaia Data Release 2 (DR2) data. The candidates were confirmed by jointly inspecting the vector point diagrams and spatial distribution. The discoveries were validated by matching near known objects and comparing their mean astrometric parameters with the available literature. A decontamination algorithm was applied to the three-dimensional astrometric space to derive membership likelihoods for clusters stars. By rejecting stars with low membership likelihoods, we built decontaminated colour–magnitude diagrams and derived the clusters astrophysical parameters by isochrone fitting. The structural parameters were also derived by King-profile fittings over the stellar distributions. The investigated clusters are mainly located within 3 kpc from the Sun, with ages ranging from 30 Myr to 3.2 Gyr and reddening limited to E(B − V) = 2.5. On average, our cluster sample presents less concentrated structures than Gaia DR2 confirmed clusters, since the derived core radii are larger while the tidal radii are not significantly different. Most of them are located in the IV quadrant of the Galactic disc at low latitudes, therefore, they are immersed in dense fields characteristic of the inner Milky Way.</jats:p>

The Spiral Structure in the Solar Neighborhood

“…Since the publication of Gaia DR2 (Brown et al, 2018), on the one hand, the parameters of known OCs have been updated (Cantat-Gaudin et al, 2018;Soubiran et al, 2018;Bossini et al, 2019;Monteiro and Dias, 2019;Dias et al, 2021;Tarricq et al, 2021). On the other hand, a large number of new OCs and candidates have been identified (e.g., see Castro-Ginard et al, 2018;Cantat-Gaudin et al, 2019;Castro-Ginard et al, 2019;Sim et al, 2019;Liu and Pang, 2019;Hao et al, 2020;Castro-Ginard et al, 2020;Ferreira et al, 2020;He et al, 2021a;Hunt and Reffert, 2021;Ferreira et al, 2021). With OCs, the nearby spiral arms were studied by Cantat-Gaudin et al ( 2018 2021) compiled a catalogue of more than 3,700 OCs from the references above, and re-calculated the parameters (parallaxes, mean proper motions, radial velocities) based on the latest Gaia EDR3 (Brown et al, 2021).…”

The Distribution of Open Clusters in the Galaxy

“…In this work, we selected the clusters with published individual stellar membership, determined from Gaia DR2 astrometric data by Castro-Ginard et al (2019, Liu and Pang (2019), Sim et al (2019), Ferreira et al (2020, and Monteiro et al (2020), to estimate distance and ages from isochrone fittings. Most open clusters had stellar membership probabilities determined by Cantat-Gaudin et al (2018) using the UPMASK procedure (Krone-Martins and Moitinho, 2014) applied to the astrometric parameters (proper motion and parallax) considering their uncertainty and the correlations between those three parameters.…”

“…The open clusters are known to constitute one of the best classes of objects to investigate the Galactic structure and Stellar Dynamics, since they have relatively precise ages estimated from isochrone fits. Recently, the Gaia DR2 catalog (Gaia Collaboration et al, 2018) released data on more than 1 billion stars with magnitudes G ≤ 21, with high precision astrometric and photometric data, which allows to improve the stellar membership determination and characterization of thousands of open clusters (Castro-Ginard et al, 2019Liu and Pang, 2019;Sim et al, 2019;Cantat-Gaudin et al, 2020;Ferreira et al, 2020;Monteiro et al, 2020), resulting in more reliable determination of their fundamental parameters. The data obtained on velocities, distances and ages allow us to present the analyses of the distribution of the open clusters in the solar neighborhood, exploring the birthplaces and actual positions on the Galactic plane.…”

A low density wave's spiral pattern speed, from the tracer separations (age gradient) across a spiral arm in the Milky Way

“…8 in Cantat-Gaudin et al (2020), Fig. 12 in Ferreira et al (2020). From the open star cluster distributions, the arm width appears to be large.…”