Determining the shape of dwarf irregular ( dIrr ) galaxies is controversial because if one assumes that these objects are disks and if these disks are randomly distributed over the sky , then their projected minor-to-major axis ratios should follow a particular statistical distribution , which is not observed .
Thus , different studies have led to different conclusions .
Some believe that the observed distributions can be explained by assuming the dIrrs are thick disks while others have concluded that dIrrs are triaxial .
Fortunately , the central stellar velocity dispersion , \sigma _ { z, 0 } , combined with maximum rotation speed , V _ { max } , provides a kinematic measure , V _ { max } / \sigma _ { z, 0 } , which gives the three dimensional shape of a system .
In this work , we present the stellar and gas kinematics of DDO 46 and DDO 168 from the LITTLE THINGS survey and determine their respective V _ { max } / \sigma _ { z, 0 } values .
We used the Kitt Peak National Observatory ’ s Mayall 4-meter telescope with the Echelle spectrograph as a long-slit spectrograph , which provided a two dimensional , 3 ^ { \prime } -long slit .
We acquired spectra of DDO 168 along four position angles by placing the slit over the morphological major and minor axes and two intermediate position angles .
However , due to poor weather conditions during our observing run for DDO 46 , we were able to extract only one useful data point from the morphological major axis .
We determined a central stellar velocity dispersion perpendicular to the disk , \sigma _ { z, 0 } , of 13.5 \pm 8 km s ^ { -1 } for DDO 46 and < \sigma _ { z, 0 } > of 10.7 \pm 2.9 km s ^ { -1 } for DDO 168 .
We then derived the maximum rotation speed in both galaxies using the LITTLE THINGS H i data .
We separated bulk motions from non-circular motions using a double Gaussian decomposition technique and applied a tilted-ring model to the bulk velocity field .
We corrected the observed H i rotation speeds for asymmetric drift and found a maximum velocity , V _ { max } , of 77.4 \pm 3.7 and 67.4 \pm 4.0 for DDO 46 and DDO 168 , respectively .
Thus , we derived a kinematic measure , V _ { max } / \sigma _ { z, 0 } , of 5.7 \pm 0.6 for DDO 46 and 6.3 \pm 0.3 for DDO 168 .
Comparing these values to ones determined for spiral galaxies , we find that DDO 46 and DDO 168 have V _ { max } / \sigma _ { z, 0 } values indicative of thin disks , which is in contrast to minor-to-major axis ratio studies .