S20B0089abst
S20B0089
We are executing NIR surveys of nearby young clusters to understand the formation mechanisms young brown dwarfs and planetary-mass objects and their IMFs. Hundreds of substellar-mass objects with NIR excesses have been newly identified using UKIRT/WFCAM. There is not any cutoff at low-mass end in the derived IMFs and it could be dependent on the forming cloud gas/dust density. However, the mass estimate from JHK photometry alone is somewhat uncertain due to the age assumption, uncertain temperature and contaminated background sources. We propose NIR multi-object spectroscopy of our previously identified substellar-mass YSO candidates in the most nearby cluster forming cloud of Corona Australis and Serpens South for comparison. We will confirm them bona-fide YSOs and determine their temperature from depths of water absorption bands from MOIRCS HK spectra. Together the derived temperature with our previously determined luminosity, we will place the substellar-mass YSOs on the HR diagram to characterize the mass and age with the evolutionary models. Our goal is to clarify whether substellar IMF is not universal and to search possible environmental differences through comparison of it with core MF in the same region.
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