The strange case of a sub-DLA with very little HI

We report a deep search for HI 21cm emission from the $z=0.00632$ sub-DLA toward PG1216+069 with the Giant Metrewave Radio Telescope. No emission was detected and our $5\sigma$ upper limit on the mass of any associated galaxy is $M_{\mathrm{H}\mathrm{I}}\lesssim {10}^7{M}_{\odot }$, nearly 3 orders of magnitude less than M${}_{\mathrm{H}\mathrm{I}}^{\star }$. The $z\sim 0.006$ absorber is thus the most extreme known deviation from the standard paradigm in which high column density quasar absorption lines arise in the disks of gas-rich galaxies.