Exploring Planetary-Mass Brown Dwarfs in Young Star Clusters with JWST
Ray Jayawardhana (Johns Hopkins University)
Tuesday 01/10/2024 @ 14:00, Sala Antonio Sollima (IV piano Battiferro)
The discovery and characterization of free-floating planetary-mass objects (FFPMOs) is fundamental to our understanding of star and planet formation. The James Webb Space Telescope affords the opportunity to search for objects down to the opacity limit for fragmentation in nearby star-forming regions. We have conducted an extremely deep spectroscopic survey of the young star cluster NGC1333, using the NIRISS instrument on the JWST. The observations cover 19 known brown dwarfs, for most of which we confirm spectral types using NIRISS spectra. We discover six new candidates with L-dwarf spectral types that are plausible planetary-mass members of the cluster, with estimated masses between 5-15 times that of Jupiter. One, at 5 Jupiter masses, shows clear infrared excess emission and is a good candidate to be the lowest mass object known to have a disk. We do not find any objects later than mid-L spectral type. Our findings put the fraction of FFPMOs in NGC1333 at ~10 % of the number of cluster members. The paucity of ~Jupiter-mass objects, despite the survey’s unprecedented sensitivity, suggests that our observations reach the lowest mass objects formed like stars in NGC1333. We also search for wide binaries in our images and find a young brown dwarf with a planetary-mass companion. I will compare our results for NGC1333 with those reported recently for a few other regions. Finally, I will preview our on-going JWST program aimed at characterizing a sample of FFPMOs with indications of disks.