First Detection of HCO${}^{+}$ Absorption in the Magellanic System

Abstract

We present the first detection of HCO${}^{+}$ absorption in the Magellanic System. Using the Australia Telescope Compact Array (ATCA), we observed 9 extragalactic radio continuum sources behind the Magellanic System and detected HCO${}^{+}$ absorption towards one source located behind the leading edge of the Magellanic Bridge. The detection is located at LSR velocity of $v=214.0\pm 0.4\mathrm{km}{\mathrm{s}}^{-1}$, with a full width at half maximum of $\Delta v=4.5\pm 1.0\mathrm{km}{\mathrm{s}}^{-1}$ and optical depth of $\tau (\mathrm{HC}{\mathrm{O}}^{+})=0.10\pm 0.02$. Although there is abundant neutral hydrogen (HI) surrounding the sightline in position-velocity space, at the exact location of the absorber the HI column density is low, $<10^{20}\mathrm{c}{\mathrm{m}}^{-2}$, and there is little evidence for dust or CO emission from Planck observations. While the origin and survival of molecules in such a diffuse environment remains unclear, dynamical events such as HI flows and cloud collisions in this interacting system likely play an important role.

Accepted for publication in ApJ. 6 pages, 2 figures, 2 tables

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Cited by in corpus (6)

• The Magellanic Stream: Circumnavigating the Galaxy
• An HST/COS legacy survey of high-velocity ultraviolet absorption in the Milky Way's circumgalactic medium and the Local Group
• Gas Accretion onto the Milky Way
• Young stars in the periphery of the Large Magellanic Cloud
• A Search for 3-mm Molecular Absorption Line Transitions in the Magellanic Stream
• In-Situ Star Formation in the Outskirts of the Large Magellanic Cloud: Gaia DR2 Confirmation