We examine the H i total intensity maps of the VLA LITTLE-THINGS galaxies and identify an H i bar in the dwarf irregular galaxy DDO 168 which has a dense and compact dark matter halo that dominates at all radii .
This is only the third galaxy found to host an H i bar .
Using the H i kinematic data , we apply the Tremaine-Weinberg method to estimate the pattern speed of the bar .
The H i bar is found to have an average pattern speed of 23.3 \pm 5.9 km \thinspace s ^ { -1 } \thinspace kpc ^ { -1 } .
Interestingly , for the first time , we find that the observed pattern speeds of the bar in the two kinematic halves are different .
We identify the origin of this difference to be the kinematic asymmetry .
This observed offset in the pattern speed serves to put a stringent constraint on the lifetime of the bar set by the winding timescale .
The lifetime of the bar is found to be \sim 5.3 \times 10 ^ { 8 } years , which is \sim 2 times the local dynamical time scale of the disc .
We also find the H i bar in DDO 168 to be a weak bar with a strength of \sim 0.2 .
If H i bar being weak can be easily disturbed , this could possibly explain why it is extremely rare to observe H i bars in galaxies .
We estimate the bar radius to be \sim 1 kpc and the dimensionless ratio , R _ { L } / R _ { b } to be \geq 2.1 indicating a ‘ slow ’ bar in DDO 168 .
Our results confirm the proposition that the dynamical friction with the halo slows down a rotating bar in a galaxy dominated by dark matter halo from inner radii .