Discovery of OH absorption from a galaxy at z~0.05: implications for large surveys with SKA pathfinders
We present the first detection of OH absorption in diffuse gas at $z>0$, along with another eight stringent limits on OH column densities for cold atomic gas in galaxies at $0 $13.6) to be $n_{\rm OH}$ = $0.008^{+0.018}_{-0.008}$ at $z\sim0.1$. Based on this we expect to detect 10$^{+20}_{-10}$ such OH absorbers from the MeerKAT Absorption Line Survey. Using HI 21-cm and OH 1667 MHz absorption lines detected towards Q0248+430, we estimate ($ΔF/F$) = (5.2$\pm$4.5)$\times 10^{-6}$, where $F \equiv g_p (α^2/μ)^{1.57}$, $α$ $-$ the fine structure constant, $μ$ $-$ the electron-proton mass ratio and $g_p$ $-$ the proton gyromagnetic ratio. This corresponds to $Δα/α$($z=0.0519$) = (1.7 $\pm$ 1.4)$\times 10^{-6}$, which is among the stringent constraints on the fractional variation of $α$.