The distance, supernova rate and supernova progenitors of NGC 6946

Abstract

The distance to the fireworks galaxy NGC 6946 is highly uncertain. Recent distance estimates using the tip of the red giant branch of 7.7 to 7.8 Mpc are larger than the distance commonly assumed for studying supernovae in this galaxy of 5.9 Mpc. Here we use the high supernova rate of the galaxy to derive the star-formation rate and predict the galaxy's FUV flux. We also account for dust extinction by different methods to derive a distance of 7.9+/-4.0 Mpc for NGC 6946. We then use the new distance to re-evaluate the understanding of the supernova progenitors 2002hh, 2004et, 2017eaw, the possible electron capture event 2008S and the possible black-hole forming event N6946-BH1. For the latter two exotic events the new distance improves the consistency between the observed progenitors and the stellar models that give rise to these events. From our findings we strongly recommend that all future studies of NGC~6946 must use the greater distance to the galaxy of 7.72+/-0.32 Mpc of Anand et al. (2018).

Accepted for publication in MNRAS letters, 5 pages, 1 figure, 1 table

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• Connecting the Light Curves of Type IIP Supernovae to the Properties of their Progenitors
• Progenitor properties of type II supernovae: fitting to hydrodynamical models using Markov chain Monte Carlo methods
• Comparing the Inner and Outer Star Forming Complexes in the Nearby Spiral Galaxies NGC 628, NGC 5457 and NGC 6946 using UVIT Observations
• BVRI Photometry of the Classic Type II-P Supernova 2017eaw in NGC 6946: Day 3 to Day 594
• The Supernova Remnant Population of NGC6946 as Observed in [Fe II] 1.644 $\mu$m with HST
• Metal-THINGS: The association and optical characterization of SNRs with HI holes in NGC 6946
• The Masses of Supernova Remnant Progenitors in NGC 6946
• What can Gaussian Processes really tell us about supernova lightcurves? Consequences for Type II(b) morphologies and genealogies
• The $\kappa$-model, a minimal model alternative to dark matter. Application to the galactic rotation problem
• A Multiwavelength Classification and Study of Red Supergiant Candidates in NGC 6946
• Pa$\beta$, H$\alpha$, and Attenuation in NGC 5194 and NGC 6946