2008/07/06 by J. A. Caballero, L. Dinis, Luis Dinís
Chemistry · Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Star Formation Studies #Cluster (spacecraft) #Computer science #Galaxy #Open cluster #Physics #Pleiades #ROSAT #Sky #Spectroscopy and Laser Applications #Star cluster #Stars #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1002/asna.200811024
Accepted for publication in Astronomische Nachrichten
arxiv created 2008/07/06 · openalex publication_date 2008/09/25 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
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 σ Orionis cluster), and the η 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. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)