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

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 (L_HDO) 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 L_HDO for the LMC hot cores fit very well into the L_HDO trends with Lb_ol and metallicity observed toward the Galactic hot cores. Our results indicate 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 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.