The Search for Extragalactic Lithium Hydride

TL;DR

This study reports the detection of lithium hydride in an extragalactic source using millimeter-wave observations, providing insights into interstellar chemistry at high redshifts.

Contribution

First detection of extragalactic lithium hydride in absorption, demonstrating the feasibility of using millimeter-wave observations for such studies.

Findings

LiH detected toward B0218+357 with a specific column density

Upper limit set on the ^6Li/^7Li isotopic ratio

LiH not detected in other observed quasars

Abstract

We have conducted Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of LiH, in absorption, toward three quasars. These quasars, B0218+357, PKS1830-211, and PKS0201+113, have redshifts of z = 0.685 - 3.387$, and shift the LiH J=1-0 transition to the 1 mm and 3mm wavelength bands, where atmospheric absorption is sharply reduced from that predominating near the rest frequency of 443 GHz. We report a 3$\sigma$ detection of LiH toward B0218+357 with a column density of 1.4x10^{12} cm^{-2} and place an upper limit on the ^6Li/^7Li ratio of <0.16. LiH was not detected toward any other source.