A revisit to agglomerates of early-type Hipparcos stars

Abstract

We study the spatial structure and sub-structure of regions rich in Hipparcos stars with blue B_T-V_T colours. These regions, which comprise large stellar complexes, OB associations, and young open clusters, are tracers of on-going star formation in the Galaxy. The DBSCAN (Density-Based Spatial Clustering of Applications with Noise) data clustering algorithm is used to look for spatial overdensities of early-type stars. Once an overdensity, "agglomerate", is identified, we carry out a data and bibliographic compilation of their star member candidates. The actual membership in agglomerate of each early-type star is studied based on its heliocentric distance, proper motion, and previous spectro-photometric information. We identify 35 agglomerates of early-type Hipparcos stars. Most of them are associated to previously known clusters and OB associations. The previously unknown P Puppis agglomerate is subject of a dedicated study with Virtual Observatory tools. It is actually a new, nearby, young open cluster (d ~ 470 pc, age ~ 20 Ma) with a clear radial density gradient. We list P Puppis and other six agglomerates (including NGC 2451 A, vdBH 23, and Trumpler 10) as new sites for substellar searches because of their youth, closeness, and spatial density. We investigate in detail the sub-structure in the Orion, CMa-Pup and Pup-Vel OB complexes ("super-agglomerates"). We confirm or discover some stellar overdensities in the Orion complex, like the 25 Ori group, the Horsehead region (including the sigma Orionis cluster), and the eta Orionis agglomerate. Finally, we derive accurate parallactic distances to the Pleiades, NGC 2451 A, and IC 2391, describe several field early-type stars at d < 200 pc, and discuss the incompleteness of our search.

Accepted for publication in Astronomische Nachrichten

References in corpus (12)

• Spitzer 24 Micron Observations of Open Cluster IC 2391 and Debris Disk Evolution of FGK Stars
• Groups of galaxies in the SDSS Data Release 5. A group-finder and a catalogue
• Kinematic structure in the young Sigma Orionis association
• The Monitor project: Rotation of low-mass stars in the open cluster NGC 2547
• Stars and brown dwarfs in the sigma Orionis cluster: the Mayrit catalogue
• Debris Disks in NGC 2547
• Southern wide very low-mass stars and brown dwarfs in resolved binary and multiple systems
• Spatial distribution of stars and brown dwarfs in sigma Orionis
• Dynamical parallax of sigma Ori AB: mass, distance and age
• WIYN Open Cluster Study. XXVI. Improved kinematic membership and spectroscopy of IC 2391
• Young stars and brown dwarfs surrounding Alnilam (eps Ori) and Mintaka (del Ori)
• The Structure and the Distance of Collinder 121 from Hipparcos and Photometry: Resolving the Discrepancy

Cited by in corpus (6)

• OB associations and their origins
• LACEwING: A New Moving Group Analysis Code
• A census of $\rho$ Oph candidate members from Gaia DR2
• The Structure and 3D Kinematics of Vela OB2
• Report on Optimal Substructure Techniques for Stellar, Gas and Combined Samples
• Open superclusters I: The most populated primordial groups of open clusters in the third quadrant of the Galactic disc