We report the discovery of two methane dwarfs in the dark cloud L 1688 of the \rho Oph star-forming region .
The two objects were among the T dwarf candidates with possible methane absorption and cool atmospheres , as diagnosed by infrared colors using deep WIRCam/CFHT HK plus CH4ON images , and IRAC/Spitzer c2d data .
Follow-up spectroscopic observations with the FLAMINGOS-2/Gemini South confirmed the methane absorption at 1.6 µm .
Compared with spectral templates of known T dwarfs in the field , i.e. , of the old populations , Oph J162738 - 245240 ( Oph-T3 ) is a T0/T1 type , whereas Oph J162645 - 241949 ( Oph-T17 ) is consistent with a T3/T4 type in the H band but an L8/T1 in the K band .
Compared with the BT-Settl model , both Oph-T3 and Oph-T17 are consistent with being cool , \sim 1000 K and \sim 900 K , respectively , and of low surface gravity , \log ( g ) = 3.5 .
With an age no more than a couple Myr , these two methane dwarfs thereby represent the youngest T dwarfs ever confirmed .
A young late L dwarf , Oph J162651 - 242110 , was found serendipitously in our spectroscopic observations .