We report the detection of H _ { 2 } in a z _ { abs } = 0.0963 Damped Lyman- \alpha ( DLA ) system towards z _ { em } = 0.4716 QSO J1619+3342 .
This DLA has log N ( H i ) = 20.55 \pm 0.10 , 18.13 \leq log N ( H _ { 2 } ) \leq 18.40 , [ S/H ] = -0.62 \pm 0.13 , [ Fe/S ] = -1.00 \pm 0.17 and the molecular fraction -2.11 \leq log [ f ( { H _ { 2 } } ) ] \leq - 1.85 .
The inferred gas kinetic temperature using the rotational level population is in the range 95 - 132 K. We do not detect C i or C ii ^ { * } absorption from this system .
Using R and V band deep images we identify a sub-L _ { * } galaxy at an impact parameter of 14 kpc from the line of sight , having consistent photometric redshift , as a possible host for the absorber .
We use the photoionization code cloudy to get the physical conditions in the H _ { 2 } component using the observational constrains from H _ { 2 } , C i , C ii ^ { * } and Mg i .
All the observations can be consistently explained if one or more of the following is true : ( i ) Carbon is underabundant by more than 0.6 dex as seen in halo stars with Z \sim 0.1 Z _ { \odot } , ( ii ) H i associated with H _ { 2 } component is less than 50 % of the H i measured along the line of sight and ( iii ) the H _ { 2 } formation rate on the dust grains is at least a factor two higher than what is typically used in analytic calculations for Milky Way interstellar medium .
Even when these are satistifed , the gas kinetic temperature in the models are much lower than what is inferred from the ortho-to-para ratio of the molecular hydrogen .
Alternatively the high kinetic temperature could be a consequence of contribution to the gas heating from non-radiative heating processes seen in hydrodynamical simulations .