We present ALMA long-baseline observations toward the Class 0 protostar IRAS 16253-2429 ( hereafter IRAS 16253 ) with a resolution down to 0 \farcs 12 ( \sim 15 au ) .
The 1.3 mm dust continuum emission has a deconvolved Gaussian size of 0 \farcs 16 \times 0 \farcs 07 ( 20 au \times 8.8 au ) , likely tracing an inclined dusty disk .
Interestingly , the position of the 1.38 mm emission is offset from that of the 0.87 mm emission along the disk minor axis .
Such an offset may come from a torus-like disk with very different optical depths between these two wavelengths .
Furthermore , through CO ( 2 - 1 ) and C ^ { 18 } O ( 2 - 1 ) observations , we study rotation and infall motions in this disk-envelope system and infer the presence of a Keplerian disk with a radius of 8 - 32 au .
This result suggests that the disk could have formed by directly evolving from a first core , because IRAS 16253 is too young to gradually grow a disk to such a size considering the low rotation rate of its envelope .
In addition , we find a quadruple pattern in the CO emission at low velocity , which may originate from CO freeze out at the disk/envelope midplane .
This suggests that the “ cold disk ” may appear in the early stage , implying a chemical evolution for the disk around this proto-brown dwarf ( or very low-mass protostar ) different from that of low-mass stars .