2022ApJ...933...64S

We report the first detection of deuterated water (HDO) toward an extragalactic hot core. The HDO 2₁₁-2₁₂ line has been detected toward hot cores N 105-2 A and 2 B in the N 105 star-forming region in the low-metallicity Large Magellanic Cloud (LMC) dwarf galaxy with the Atacama Large Millimeter/submillimeter Array (ALMA). We have compared the HDO line luminosity (L_HDO) measured toward the LMC hot cores to those observed toward a sample of 17 Galactic hot cores covering three orders of magnitude in L_HDO, four orders of magnitude in bolometric luminosity (L_bol), and a wide range of Galactocentric distances (thus metallicities). The observed values of L_HDO for the LMC hot cores fit very well into the L_HDO trends with L_bol and metallicity observed toward the Galactic hot cores. We have found that L_HDO seems to be largely dependent on the source luminosity, but metallicity also plays a role. We provide a rough estimate of the H₂O column density and abundance ranges toward the LMC hot cores by assuming that HDO/H₂O toward the LMC hot cores is the same as that observed in the Milky Way; the estimated ranges are systematically lower than Galactic values. The spatial distribution and velocity structure of the HDO emission in N 105-2 A is consistent with HDO being the product of the low-temperature dust grain chemistry. Our results are in agreement with the astrochemical model predictions that HDO is abundant regardless of the extragalactic environment and should be detectable with ALMA in external galaxies.