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We examine the HI total intensity maps of the VLA LITTLE-THINGS galaxies andidentify an HI bar in the dwarf irregular galaxy DDO 168 which has a dense andcompact dark matter halo that dominates at all radii. This is only the thirdgalaxy found to host an HI bar. Using the HI kinematic data, we apply theTremaine-Weinberg method to estimate the pattern speed of the bar. The HI baris found to have an average pattern speed of $23.3 \pm 5.9$ km/s/kpc.Interestingly, for the first time, we find that the observed pattern speeds ofthe bar in the two kinematic halves are different. We identify the origin ofthis difference to be the kinematic asymmetry. This observed offset in thepattern speed serves to put a stringent constraint on the lifetime of the barset 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 ofthe disc. We also find the HI bar in DDO 168 to be a weak bar with a strengthof $\sim 0.2$. If HI bar being weak can be easily disturbed, this couldpossibly explain why it is extremely rare to observe HI bars in galaxies. Weestimate 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 resultsconfirm the proposition that the dynamical friction with the halo slows down arotating bar in a galaxy dominated by dark matter halo from inner radii.

Detection of a slow HI bar in the dwarf irregular galaxy DDO 168