An Outflow-driven Water Maser Associated with Positive Black Hole Feedback in the Dwarf Galaxy Henize 2–10

Abstract

Henize 2–10 is a dwarf galaxy experiencing positive black hole (BH) feedback from a radio-detected low-luminosity active galactic nucleus. Previous Green Bank Telescope (GBT) observations detected a H _2 O “kilomaser” in Henize 2–10, but the low angular resolution (33″) left the location and origin of the maser ambiguous. We present new Karl G. Jansky Very Large Array observations of the H _2 O maser line at 22.23508 GHz in Henize 2–10 with ∼2″ resolution. These observations reveal two maser sources distinct in position and velocity. The first maser source is spatially coincident with the known BH outflow and the region of triggered star formation ∼70 pc to the east. Combined with the broad width of the maser ( W _50 ∼ 66 km s ^−1 ), this confirms our hypothesis that part of the maser detected with the GBT is produced by the impact of the BH outflow shocking the dense molecular gas along the flow and at the interface of the eastern star-forming region. The second maser source lies to the southeast, far from the central BH, and has a narrow width ( W _50 ∼ 8 km s ^−1 ), suggesting a star formation–related origin. This work has revealed the nature of the H _2 O kilomaser in Henize 2–10 and illustrates the first known connection between outflow-driven H _2 O masers and positive BH feedback.

Keywords

• Dwarf galaxies
• Water masers
• Molecular gas
• Active galactic nuclei