Open AccessSpectroscopy of planetary mass brown dwarfs in Orion
Author(s) -
Lucas P. W.,
Weights D. J.,
Roche P. F.,
Riddick F. C.
Publication year - 2006
Publication title -
monthly notices of the royal astronomical society: letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.067
H-Index - 122
eISSN - 1745-3933
pISSN - 1745-3925
DOI - 10.1111/j.1745-3933.2006.00244.x
Subject(s) - brown dwarf , physics , astrophysics , planetary system , astronomy , spectrograph , stars , cluster (spacecraft) , planetary mass , population , spectral line , demography , sociology , computer science , programming language
We report the results of near infrared spectroscopy of 11 luminosity‐selected candidate planetary mass objects (PMOs) in the Trapezium Cluster with Gemini South/Gemini Near‐Infrared Spectrograph and Gemini North/Near‐Infrared Imager. Six have spectral types ≥M9, in agreement with expectations for PMOs. Two have slightly earlier types, and three are much earlier types which are probably field stars. Four of the six sources with types ≥M9 have pseudo‐continuum profiles which confirm them as low gravity cluster members. The gravity status of the other cool dwarfs is less clear but these remain candidate PMOs. The derived number fraction of PMOs with M = 3 – 15 M Jup is 1–14 per cent, these broad limits reflecting the uncertainty in source ages. However, the number fraction with M < 20 M Jup is at least 5 per cent. These detections add significantly to the body of evidence that a planetary mass population is produced by the star formation process.