eta Chameleontis: abnormal initial mass function or dynamical evolution?

Abstract

Eta Chamaeleontis is a unique young (~9 Myr) association with 18 systems concentrated in a radius of ~35 arcmin, i.e. 1pc at the cluster distance of 97pc. No other members have been found up to 1.5 degrees from the cluster centre. The cluster mass function is consistent with the IMF of other rich young open clusters in the higher mass range but shows a clear deficit of low mass stars and brown dwarfs with no objects below 0.1Msun. The aim of this paper is to test whether this peculiar mass function could result from dynamical evolution despite the young age of the cluster. We performed N-body numerical calculations starting with a log-normal IMF and different initial conditions in terms of number of systems and cluster radius using the code NBODY3. We simulated the cluster dynamical evolution over 10 Myr and compared the results to the observations. We found that it is possible to reproduce eta Cha when starting with a very compact configuration (with Ninit=40 and R0=0.005pc) which suggests that the IMF of the association might not be abnormal. The high initial density might also explain the deficit of wide binaries that is observed in the cluster.

10 pages, 5 figures, accepted by A&A

References in corpus (24)

• Galactic Stellar and Substellar Initial Mass Function
• On the variation of the Initial Mass Function
• Embedded Clusters in Molecular Clouds
• The Formation of a Bound Star Cluster: From the Orion Nebula Cluster to the Pleiades
• The hierarchical formation of a stellar cluster
• The Luminosity & Mass Function of the Trapezium Cluster: From B stars to the Deuterium Burning Limit
• The maximum stellar mass, star-cluster formation and composite stellar populations
• 2MASS Observations of the Perseus, Orion A, Orion B, and Monoceros R2 Molecular Clouds
• Early Evolution of Stellar Groups and Clusters: Environmental Effects on Forming Planetary Systems
• Evidence for the Strong Effect of Gas Removal on the Internal Dynamics of Young Stellar Clusters
• The Effect of Gas Loss on the Formation of Bound Stellar Clusters
• Binarity as a key factor in protoplanetary disk evolution: Spitzer disk census of the eta Chamaeleontis cluster
• The Eta Chamaeleontis Cluster: Origin in the Sco-Cen OB Association
• Spectroscopy of Candidate Members of the Eta Cha and MBM12 Young Associations
• On the origin of the distribution of binary-star periods
• The dynamical evolution of Taurus--Auriga-type aggregates
• Deficit of wide binaries in the eta Chamaeleontis young cluster
• The lower mass function of the young open cluster Blanco 1: from 30 Mjup to 3 Mo
• Infrared study of the eta Chamaeleontis cluster and the longevity of circumstellar discs
• ECHA J0843.3-7905: Discovery of an 'old' classical T Tauri star in the eta Chamaeleontis cluster
• A Survey for Low-Mass Stars and Brown Dwarfs in the Eta Cha and Eps Cha Young Associations
• Population and dynamical state of the eta Chamaeleontis sparse young open cluster
• A deep photometric survey of the eta Chamaeleontis cluster down to the brown dwarf - planet boundary
• Probing the Low Mass Stellar End of the eta Chamaeleontis Cluster

Cited by in corpus (21)

• A Universal Stellar Initial Mass Function? A Critical Look at Variations
• Timescale of Mass Accretion in Pre-Main-Sequence Stars
• An Infrared/X-ray Survey for New Members of the Taurus Star-Forming Region
• A Spitzer Census of Transitional Protoplanetary Disks with AU-Scale Inner Holes
• The early dynamical evolution of cool, clumpy star clusters
• The effects of dynamical interactions on planets in young substructured star clusters
• Testing the universality of star formation - I. Multiplicity in nearby star-forming regions
• The Long-Lived Disks in the Eta Chamaeleontis Cluster
• Maximum stellar mass versus cluster membership number revisited
• Search for associations containing young stars (SACY). VI. Is multiplicity universal? Stellar multiplicity in the range 3-1000 au from adaptive-optics observations
• Binaries in star clusters and the origin of the field stellar population
• Properties of Stellar Clusters around High-Mass Young Stars
• System IMF of the 25 Ori Group from Planetary-Mass Objects to Intermediate/High-Mass Stars
• First detection of a low-mass stellar halo around the young open cluster Eta Chamaeleontis
• Episodic disk accretion in the halo of the 'old' Pre-Main Sequence cluster Eta Chamaeleontis
• The dynamical evolution of very-low mass binaries in open clusters
• A formation scenario of young stellar groups in the region of the Scorpio Centaurus OB association
• Disk Evolution Study Through Imaging of Nearby Young Stars (DESTINYS): A close low mass companion to ET Cha
• Deep XMM-Newton observation of the Eta Chamaleontis cluster
• Reverse dynamical evolution of Eta Chamaeleontis
• RX J0942.7-7726AB: an isolated pre-main sequence wide binary