The Anatomy of an Unusual Edge-on Protoplanetary Disk. II. Gas Temperature and a Warm Outer Region

We present high-resolution $^{12}$CO and $^{13}$CO 2-1 ALMA observations, as well optical near-infrared spectroscopy, of the highly-inclined protoplanetary disk around SSTC2D J163131.2-242627. The spectral type we derive for source is consistent with a $\rm 1.2 \, M_{\odot}$ star inferred from observations. Despite its massive circumstellar disk, find little to no evidence ongoing accretion on star. CO maps reveal that unusually compact along vertical direction, appearance in scattered light images. gas extends about twice far away both submillimeter continuum light. detected two surface layers separated by midplane region which emission suppressed, expected freeze-out cold midplane. apply modified version Topographically Reconstructed Distribution method presented Dutrey et al. 2017 temperature structure disk. CO-emitting $\sim$33 K $\sim$20 at R<200$ au, respectively. Outside R>200$ disk's increases $\sim$30 K, nearly vertically isothermal profile. transition coincides dramatic reduction sub-micron sub-millimeter interpret this interstellar UV radiation providing an additional heating outer part