Open AccessA highly abnormal massive star mass function in the Orion Nebula cluster and the dynamical decay of trapezium systems
Author(s) -
PflammAltenburg J.,
Kroupa P.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.058
H-Index - 383
eISSN - 1365-2966
pISSN - 0035-8711
DOI - 10.1111/j.1365-2966.2006.11028.x
Subject(s) - physics , orion nebula , stars , astrophysics , proper motion , radius , initial mass function , mass segregation , star cluster , nebula , star formation , cluster (spacecraft) , star (game theory) , population , computer security , demography , sociology , computer science , programming language
The Orion Nebula cluster (ONC) appears to be unusual on two grounds: the observed constellation of the OB stars of the entire ONC and its Trapezium at its centre implies a time‐scale problem given the age of the Trapezium, and an initial mass function (IMF) problem for the whole OB star population in the ONC. Given the estimated crossing time of the Trapezium, it ought to have totally dynamically decayed by now. Furthermore, by combining the lower limit of the ONC mass with a standard IMF it emerges that the ONC should have formed at least about 40 stars heavier than 5 M ⊙ while only 10 are observed. Using the N ‐body experiments we (i) confirm the expected instability of the Trapezium and (ii) show that beginning with a compact OB‐star configuration of about 40 stars both the number of observed OB stars after 1 Myr within 1 pc radius and a compact trapezium configuration can be reproduced. These two empirical constraints thus support our estimate of 40 initial OB stars in the cluster. Interestingly, a more‐evolved version of the ONC resembles the Upper Scorpius OB association. The N ‐body experiments are performed with the new C‐code catena by integrating the equations of motion using the chain‐multiple‐regularization method. In addition, we present a new numerical formulation of the IMF.