The Old Moving Groups in the Field of Taurus

Abstract

In this work, we present a systematic search for stellar groups in the Taurus field by applying the DBSCAN algorithm to the data from Gaia DR2. We find 22 groups, consisting of 8 young groups (Groups 1–8) at ages of 2–4 Myr and distances of ∼130–170 pc, and 14 old groups (Groups 9–22) at ages of 8–49 Myr and distances of ∼110–210 pc. We characterize the disk properties of group members and find 19 new disk-bearing stars, 8 of which are in the young groups with 11 others belonging to the comparatively old groups at the ages of 8–11 Myr. We characterize the accretion properties of the group members with Hα emission lines in their Large Sky Area Multi-Object Fibre Spectroscopic Telescope spectra, and discover one source in Group 10 at an age of 10 Myr which still shows accretion activity. We investigate the kinematic relations among the old groups, find that Group 9 is kinematically related to the known Taurus members, and exclude any kinematic relations between Groups 10–22 and the known Taurus members.

The Ages of Optically Bright Subclusters in the Serpens Star-forming Region

“…In a Gaia DR2 study of the Orion OB association, Zari et al (2019) found that multiple star-forming events occurred and led to the subgroups. In a search for stellar groups in the Taurus field, Liu et al (2021) identified eight groups younger than ∼4 Myr and 14 older groups (8-49 Myr). In a smaller region, Esplin & Luhman (2022) found older stars in Corona Australis and inferred a past burst of star formation, likely related to the ongoing star formation in the Coronet cluster.…”

“…Stars formed in previous bursts are often still located in small subclusters, while some have been dispersed throughout the cloud or were born in small groups. In many clouds the older stars are not colocated with the youngest stars, indicating that the site for star formation changes with time within a cloud complex (e.g., Getman et al 2014aGetman et al , 2014bKounkel et al 2018;Kristensen & Dunham 2018;Vázquez-Semadeni et al 2018;Liu et al 2021).…”

Observational Bias and Young Massive Cluster Characterisation I. 2D Perspective Effects

“…We employ the Density-Based Spatial Clustering of Applications with Noise (DBSCAN; Ester et al 1996) algorithm to detect discrete subclusters of stars in the datasets, chosen for this work as it tends to be favoured by observers to quantify structure in cluster regions (Gao 2014, Bhattacharya et al 2017, Joncour et al 2019, Zari et al 2019, Anais Vilchez et al 2020, Gao et al 2021, Liu et al 2021, Gao et al 2021) perhaps because it offers several advantages over other well-established clustering algorithms. First, it does not require a priori knowledge of the number of clusters in a region as this is determined by the algorithm itself.…”

The Ages of Optically Bright Sub-Clusters in the Serpens Star-Forming Region

“…In a Gaia DR2 study of the Orion OB association , Zari et al (2019) found in that multiple star-forming events occurred and leaded to the subgroups. In a search for stellar groups in the Taurus field, Liu et al (2021) identified 8 groups younger than ∼ 4 Myr and 14 older groups (8-49 Myr). In a smaller region, Esplin & Luhman (2022) found older stars in Corona Australis and inferred a past burst of star formation, likely related to the ongoing star formation in the Coronet Cluster.…”

“…Stars formed in previous bursts are often still located in small subclusters, while some have been dispersed throughout the cloud or were born in small groups. In many clouds the older stars are not co-located with the youngest stars, indicating that the site for star formation changes with time within a cloud complex (e.g., Getman et al 2014b,a;Vázquez-Semadeni et al 2018;Kounkel et al 2018;Kristensen & Dunham 2018;Liu et al 2021).…”