2018MNRAS.479.5686K

We present high resolution H I 21 cm Giant Meterwave Radio Telescope observations of the superthin galaxy FGC 1540 with a spatial resolution of 10 arcsec x 8 arcsec and a spectral resolution of 1.73 km s^–1 and an rms noise of 0.9 mJy per beam. We obtain its rotation curve as well as deprojected radial H I surface density profile by fitting a 3D tilted-ring model directly to the H I data cubes using the publicly available software, Fully Automated TIRRIFIC. We also present the rotation curve of FGC 1540 derived from its optical spectroscopy study using the 6-m BTA telescope of the Special Astrophysical Observatory of the Russian Academy of Sciences. We use the rotation curve, the H I surface density profile together with Spitzer 3.6 µm, and the SDSS i-band data to construct the mass models for FGC 1540. We find that both the Pseudo-isothermal () as well as Navarro-Frenk-White dark matter (DM) haloes, fit the observed rotation curve equally well. The PIS model indicates a compact DM halo (R_C/R_D < 2), with the best-fitting core radius (R_C) approximately half the exponential stellar disc scale length (R_D), which is in agreement with the mass models of superthin galaxies studied earlier in the literature. Since the vertical thickness of the galactic stellar disc is determined by a balance between the net gravitational field and the velocity dispersion in the vertical direction, the compact DM halo may be primarily responsible in regulating the superthin vertical structure of the stellar disc in FGC 1540 as was found in case of the superthin galaxy UGC7321.