An independent determination of the local Hubble constant

TL;DR

This paper presents a new independent measurement of the local Hubble constant using HII galaxies and regions, achieving a value of approximately 71 km/s/Mpc, with potential for future refinement.

Contribution

It introduces a novel method utilizing HII regions as standard candles and provides new data for 36 giant HII regions, improving the local Hubble constant estimate.

Findings

Hubble constant estimated at 71.0 km/s/Mpc

New data for 36 giant HII regions in 13 galaxies

Method shows potential for future precision improvements

Abstract

The relationship between the integrated H$\beta$ line luminosity and the velocity dispersion of the ionized gas of HII galaxies and giant HII regions represents an exciting standard candle that presently can be used up to redshifts z ~ 4. Locally it is used to obtain precise measurements of the Hubble constant by combining the slope of the relation obtained from nearby ($z \leq $ 0.2) HII galaxies with the zero point determined from giant HII regions belonging to an `anchor sample' of galaxies for which accurate redshift-independent distance moduli are available. We present new data for 36 giant HII regions in 13 galaxies of the anchor sample that includes the megamaser galaxy NGC 4258. Our data is the result of the first four years of observation of our primary sample of 130 giant HII regions in 73 galaxies with Cepheid determined distances. Our best estimate of the Hubble parameter is $71.0\pm2.8(random)\pm2.1(systematic)$ km /s Mpc This result is the product of an independent approach and, although at present less precise than the latest SNIa results, it is amenable to substantial improvement.