A Near-Infrared Period-Luminosity Relation for Miras in NGC 4258, an Anchor for a New Distance Ladder

Understand

We present year-long, near-infrared Hubble Space Telescope WFC3 observations of Mira variables in the water megamaser host galaxy NGC 4258.

• Miras are AGB variables that can be divided into oxygen- (O-) and carbon- (C-) rich subclasses.
• Oxygen-rich Miras follow a tight (scatter $\sim 0.14$ mag) Period-Luminosity Relation (PLR) in the near-infrared and can be used to measure extragalactic distances.
• The water megamaser in NGC 4258 gives a geometric distance to the galaxy accurate to 2.6% that can serve to calibrate the Mira PLR.