The first detection of deuterated water toward extragalactic hot cores with ALMA

Abstract We discuss the first detection of deuterated water (HDO) in extragalactic hot cores. The HDO 211–212 line has been detected with the Atacama Large Millimeter/submillimeter Array (ALMA) 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), the nearest star-forming galaxy. We compared the HDO line luminosity (LHDO) measured toward two hot cores in N 105 to those observed toward a sample of 17 Galactic hot cores and found that the observed values of LHDO for the LMC hot cores fit very well into the LHDO trends with Lbol and metallicity observed toward the Galactic hot cores. Our results indicate that LHDO 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 N 105–2 A and 2 B by assuming that HDO/H2O toward the LMC hot cores is the same as that observed in the Milky Way; the obtained values are systematically lower than those measured in the Galactic hot cores. 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.