Near-infrared (JHK) spectroscopy of young stellar and substellar objects in Orion.
INGRAHAM P., ALBERT L., DOYON R. and ARTIGAU E.
Abstract (from CDS):
We performed low-resolution (R ∼ 40) near-infrared (0.9-2.4 µm) multi-object spectroscopy of 240 isolated point sources having apparent H-band magnitudes between 9 and 18 in the central 5'x6' of the Orion Trapezium cluster. The observations were performed over four nights at the Canada-France-Hawaii Telescope using the visiting instrument SIMON, an infrared imager and multi-object spectrograph. We present the spectra of 104 objects with accurately derived spectral types including 7 new objects having masses below the hydrogen-burning limit, and 6 objects with masses below the deuterium-burning limit. The spectral classification is performed by fitting previously classified spectral templates of dwarf stars (K4-M3) and optically classified young stellar and substellar objects (M4-L0), to the entire 0.9-2.4 µm spectral energy distribution in order to assign a spectral type and visual extinction for each object. Of the 104 objects studied, 44 have been previously classified spectroscopically using various techniques. We perform a rigorous comparison between the previous classifications and our own and find them to be in good agreement. Using the dereddened H-band magnitudes, the classified objects are used to create an Hertzsprung-Russell diagram for the cluster. We find that the previous age estimates of ∼1 Myr to be consistent with our results. Consistent with previous studies, numerous objects are observed to have luminosities several magnitudes above the 1 Myr isochrone. Numerous objects exhibiting emission features in the J band are also reported.
brown dwarfs - infrared: stars - open clusters and associations: individual: Orion Nebular Cluster - stars: formation - stars: low-mass - stars: luminosity function, mass function
VizieR on-line data:
<Available at CDS (J/ApJ/782/8): table4.dat table5.dat>