The low mass star and sub-stellar populations of the 25 Orionis group

Abstract

We present the results of a survey of the low mass star and brown dwarf population of the 25 Orionis group. Using optical photometry from the CIDA Deep Survey of Orion, near IR photometry from the Visible and Infrared Survey Telescope for Astronomy and low resolution spectroscopy obtained with Hectospec at the MMT, we selected 1246 photometric candidates to low mass stars and brown dwarfs with estimated masses within $0.02\lesssim M/M_{\odot }\lesssim 0.8$ and spectroscopically confirmed a sample of 77 low mass stars as new members of the cluster with a mean age of $\sim$7 Myr. We have obtained a system initial mass function of the group that can be well described by either a Kroupa power-law function with indices ${\alpha }_3=-1.73\pm 0.31$ and ${\alpha }_2=0.68\pm 0.41$ in the mass ranges $0.03\le M/M_{\odot }\le 0.08$ and $0.08\le M/M_{\odot }\le 0.5$ respectively, or a Scalo log-normal function with coefficients $m_c=0.21_{-0.02}^{+0.02}$ and $\sigma =0.36\pm 0.03$ in the mass range $0.03\le M/M_{\odot }\le 0.8$. From the analysis of the spatial distribution of this numerous candidate sample, we have confirmed the East-West elongation of the 25 Orionis group observed in previous works, and rule out a possible southern extension of the group. We find that the spatial distributions of low mass stars and brown dwarfs in 25 Orionis are statistically indistinguishable. Finally, we found that the fraction of brown dwarfs showing IR excesses is higher than for low mass stars, supporting the scenario in which the evolution of circumstellar discs around the least massive objects could be more prolonged.

Accepted for publication in MNRAS

References in corpus (17)

• The UKIRT Wide Field Camera ZYJHK Photometric System: Calibration from 2MASS
• A Spitzer view of protoplanetary disks in the gamma Velorum cluster
• Spitzer observations of the Orion OB1 association: disk census in the low mass stars
• Young Nearby Loose Associations
• The Jeans mass and the origin of the knee in the IMF
• New brown dwarfs in Upper Sco using UKIDSS Galactic Cluster Survey science verification data
• On the Constancy of the Characteristic Mass of Young Stars
• Brown dwarfs and very low mass stars in the Hyades cluster : a dynamically evolved mass function
• Multiplicity and Optical Excess Across the Substellar Boundary in Taurus
• The Keele-Exeter young cluster survey: I. Low mass pre-main sequence stars in NGC 2169
• The low-mass Initial Mass Function in the young cluster NGC 6611
• The spatial distribution of substellar objects in IC348 and the Orion Trapezium Cluster
• Sloan/Johnson-Cousins/2MASS Color Transformations for Cool-Stars
• Star Forming Regions in Cepheus
• The Young Cluster and Star Forming Region NGC 2264
• A large-scale optical-near infrared survey for brown dwarfs and very low-mass stars in the Orion OB1 association
• The Southern Flanking Fields of the 25 Orionis Group

Cited by in corpus (11)

• Ultracool Dwarfs Observed with the Spitzer Infrared Spectrograph. II. Emergence and Sedimentation of Silicate Clouds in L Dwarfs, and Analysis of the Full M5--T9 Field Dwarf Spectroscopic Sample
• The Gaia-ESO Survey: Membership probabilities for stars in 63 open and 7 globular clusters from 3D kinematics
• The Origin of the Stellar Mass Distribution and Multiplicity
• Gaia-ESO Survey: Role of magnetic activity and starspots on pre-main sequence lithium evolution
• System IMF of the 25 Ori Group from Planetary-Mass Objects to Intermediate/High-Mass Stars
• Orion revisited III. The Orion Belt population
• Search for Brown Dwarfs in IC 1396 with Subaru HSC: Interpreting the Impact of Environmental Factors on Sub-stellar Population
• Using binary statistics in Taurus-Auriga to distinguish between brown dwarf formation processes
• The NEMESIS Catalogue of Young Stellar Objects for the Orion Star Formation Complex. I. General description of data curation
• Clumpy dust rings around non-accreting young stars
• Evidence that the planetary candidate CVSO30c is a background star from optical, seeing-limited data