H I studies of extremely metal-poor dwarfs in voids - I

Abstract

We present and discuss the results of the Giant Metrewave Radio Telescope H I 21-cm line mapping for five isolated low-mass (M$_{\rm bary}$$\sim$(2-8)$\times 10^7$ M$\odot$) eXtremely Metal Poor dwarfs [12+$\log$(O/H) = 7.13-7.28], selected from the nearby void galaxy sample. All the studied void dwarfs show disturbed morphology in the H I maps with the angular resolutions of $\sim 11$ to $\sim 40\,{\rm arcsec}$. We examine the H I morphology and velocity field and the relative orientation of their stellar and gas body spins. We discuss the overall non-equilibrium state of their gas and the possible origin and evolution of the studied void dwarfs. The most straightforward interpretation of the ubiquitous phenomenon of the gas component non-equilibrium state in these and similar void dwarfs is the cold accretion from the void filaments and/or minor mergers. The cold gas accretion in voids could be linked to the presence of small filaments that constitute the substructure of voids.