Spatial distribution of stars and brown dwarfs in sigma Orionis

Abstract

I have re-visited the spatial distribution of stars and high-mass brown dwarfs in the sigma Orionis cluster (~3 Ma, ~360 pc). The input was a catalogue of 340 cluster members and candidates at separations less than 30 arcmin to sigma Ori AB. Of them, 70 % have features of extreme youth. I fitted the normalised cumulative number of objects counting from the cluster centre to several power-law, exponential and King radial distributions. The cluster seems to have two components: a dense core that extends from the centre to r ~ 20 arcmin and a rarified halo at larger separations. The radial distribution in the core follows a power-law proportional to r^1, which corresponds to a volume density proportional to r^(-2). This is consistent with the collapse of an isothermal spherical molecular cloud. The stars more massive than 3.7 Msol concentrate, however, towards the cluster centre, where there is also an apparent deficit of very low-mass objects (M < 0.16 Msol). Last, I demonstrated through Monte Carlo simulations that the cluster is azimuthally asymmetric, with a filamentary overdensity of objects that runs from the cluster centre to the Horsehead Nebula.

MNRAS, accepted

References in corpus (5)

• Gas expulsion and the destruction of massive young clusters
• Evidence for the Strong Effect of Gas Removal on the Internal Dynamics of Young Stellar Clusters
• Kinematic structure in the young Sigma Orionis association
• The brightest stars of the sigma Orionis cluster
• Circumstellar discs in the young sigma Orionis cluster

Cited by in corpus (19)

• The Spatial Structure of Young Stellar Clusters. I. Subclusters
• Stars and brown dwarfs in the sigma Orionis cluster: the Mayrit catalogue
• Dynamical parallax of sigma Ori AB: mass, distance and age
• A spectroscopic census in young stellar regions: the Sigma Orionis cluster
• The Villafranca catalog of Galactic OB groups. II. From Gaia DR2 to EDR3 and ten new systems with O stars
• A deep look into the cores of young clusters I. sigma-Orionis
• Young stars and brown dwarfs surrounding Alnilam (eps Ori) and Mintaka (del Ori)
• A Herschel view of protoplanetary disks in the $\sigma$ Ori cluster
• Statistical fractal analysis of 25 young star clusters
• Low-resolution spectroscopy and spectral energy distributions of selected sources towards sigma Orionis
• A revisit to agglomerates of early-type Hipparcos stars
• ${\mathcal{Q}}^{+}$: Characterising the structure of young star clusters
• New deep XMM-Newton observations to the west of the sigma Orionis cluster
• Testing viscous disc theory using the balance between stellar accretion and external photoevaporation of protoplanetary discs
• A novel survey for young substellar objects with the W-band filter VI: Spectroscopic census of sub-stellar members and the IMF of $\sigma$ Orionis cluster
• Hierarchical star formation in nearby galaxies
• Reaching the boundary between stellar kinematic groups and very wide binaries. IV. The widest Washington double star systems with rho > 1000 arcsec in Gaia DR3
• Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes
• Spatial differences between stars and brown dwarfs: a dynamical origin?