The first spectroscopically confirmed brown dwarfs in NGC 2264
Abstract
We present spectroscopic follow-up observations of 68 red, faint candidates from our multi-epoch, multi-wavelength, previously published survey of NGC 2264. Using near-infrared spectra from VLT/KMOS, we measure spectral types and extinction for 32 young low-mass sources. We confirm 13 as brown dwarfs in NGC 2264, with spectral types between M6 and M8, corresponding to masses between 0.02 and 0.08 M⊙. These are the first spectroscopically confirmed brown dwarfs in this benchmark cluster. 19 more objects are found to be young M-type stars of NGC 2264 with masses of 0.08 to 0.3 M⊙. 7 of the confirmed brown dwarfs as well as 15 of the M-stars have IR excess caused by a disc. Comparing with isochrones, the typical age of the confirmed brown dwarfs is <0.5 to 5 Myr. More than half of the newly identified brown dwarfs and very low mass stars have ages <0.5 Myr, significantly younger than the bulk of the known cluster population. Based on the success rate of our spectroscopic follow-up, we estimate that NGC 2264 hosts 200-600 brown dwarfs in total (in the given mass range). This would correspond to a star-to-brown dwarf ratio between 2.5:1 and 7.5:1. We determine the slope of the substellar mass function as α=0.43+0.41−0.56, these values are consistent with those measured for other young clusters. This points to a uniform substellar mass function across all star forming environments.
Citation
Pearson , S , Scholz , A , Teixeira , P S , Mužić , K & Almendros-Abad , V 2021 , ' The first spectroscopically confirmed brown dwarfs in NGC 2264 ' , Monthly Notices of the Royal Astronomical Society , vol. 507 , no. 3 , pp. 4074–4085 . https://doi.org/10.1093/mnras/stab2394
Publication
Monthly Notices of the Royal Astronomical Society
Status
Peer reviewed
ISSN
0035-8711Type
Journal article
Description
Support from STFC through grant number ST/R000824/1. K.M. acknowledges funding by the Science and Technology Foundation of Portugal (FCT), grants No. IF/00194/2015, PTDC/FISAST/28731/2017 and UIDB/00099/2020.Collections
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