Uncovering a 260 pc wide, 35-Myr-old filamentary relic of star formation

Abstract

Several recent studies have shown that the Vela OB2 region hosts a complex constellation of sub-populations with ages in the range 10 to 50 Myr. Such populations might represent the best example of the outcome of clustered star formation in Giant Molecular clouds (GMC). We use Gaia DR2 data over an area of 40 deg radius around the open cluster Collinder 135 to extend the study of the stellar populations of the Vela OB2 region over an area of several hundreds of parsecs on sky. Detailed clustering algorithms combined with the exquisite astrometric quality of the GAIA catalogue allow us to detect a new cluster named BBJ 1 that shows the same age as NGC 2547 (30 to 35 Myr), but located at a distance of 260 pc from it. Deeper investigation of the region via clustering in 5D parameter space and in the colour-magnitude diagram allows us to detect a filamentary structure of stars that bridges the two clusters. Given the extent in space of such structure (260 pc) and the young age (∼35 Myr), we exclude that such population originates by the same mechanism responsible to create tidal streams around older clusters. Even if we miss a complete picture of the 3D motion of the studied stellar structure because of the lack of accurate radial velocity measurements, we propose that such structure represent the detection of a 35 Myr old outcome of a mechanism of filamentary star formation in a GMC.

Extended stellar systems in the solar neighborhood

“…This observational evidence highlights that the observed coronae could be a consequence of the filamentary, highly substructured nature of starforming regions. In reference to Beccari et al (2020), we note that NGC 2547 is part of their identified structure (see also Cantat-Gaudin et al 2019a,b). Our analysis of this cluster, however, does not produce unambiguous evidence that the cluster is embedded in a larger structure.…”

The JCMT BISTRO Survey: Magnetic Fields Associated with a Network of Filaments in NGC 1333

“…We utilize densitybased clustering (Ester et al 1996;Kriegel et al 2011) to the data set. It is a general statistical method that recently has begun to be applied to classify astronomical sources in a multidimensional data space (e.g., Beccari et al 2018Beccari et al , 2020Jerabkova et al 2019). This method can identify clusters in a multidimensional space not only for their crests but also for their spatial extent, without assuming that their underlying spatial structures are filamentary or clumpy.…”

Collinder 135 and UBC 7: A physical pair of open clusters

“…Cr 135 and UBC 7 are located at a distance of approximately 300 pc in the Vela-Puppis star formation region (245 deg l 265 deg, −15 deg b −5 deg), which was recently thoroughly investigated with respect to its large-scale structure and kinematics using Gaia DR2 data (Cantat-Gaudin et al 2019a,b;Beccari et al 2020). In particular, the region at distances between 250 and 500 pc hosts several young open clusters divided into groups of similar age.…”

“…The oldest group (30-50 Myr according to different authors, e.g. Cantat-Gaudin et al 2019a;Beccari et al 2020) includes Cr 135 and UBC 7.…”

“…The resulting selections provide between zero and seven false members in the area. Thus, the extended structures hosting tens of probable members around Cr 135 and UBC 7 are not due to occasional field contamination and may be a part of the extended common halo of the two clusters, or a signature of filamentary structures discovered by Beccari et al (2020). Sometimes, it is difficult to attribute a star satisfying the membership conditions to one cluster or the other, or to the outer structure.…”