The expanding light echoes from supernova 2014J in M82

TL;DR

This study measures the size, brightness, and evolution of light echoes from supernova 2014J in M82, revealing complex interstellar medium structures through multi-epoch HST observations.

Contribution

First detailed measurement of expanding light echoes from SN 2014J, including size, brightness, and color evolution, highlighting complex ISM structures in M82.

Findings

Light echoes expanded from 0.60" to 0.75" over ~139 days.

Foreground scattering material is at 222 extpm37 pc and 367 extpm61 pc.

Light echo brightness increased, indicating varying scattering material distribution.

Abstract

We present the measurement of the size and surface brightness of the expanding light echoes from supernova (SN) 2014J in the nearby starburst galaxy M82. Hubble Space Telescope (HST) ACS/WFC images were taken ~277 and ~416 days (after the time of B-band maximum light) in the filters F475W, F606W, and F775W, each combined with the three polarizing filters: POL0V, POL60V, and POL120V. The two epochs' imaging reveals the time evolution of at least two major echoes. Three concentric bright regions between position angles (PA, 0^{\circ} from North, counterclockwise). 80^{\circ} ~ 170^{\circ} have projected radius of 0.60" on the sky on ~277 days and expanding to 0.75" on ~416 days, corresponding to scattering materials at a foreground distance of 222\pm37 pc. Another fainter but evident light echo extending over a wide range of PA has radii of 0.75" and 0.96" on ~277 and ~416 days. This corresponds to scattering material at a foreground distance of 367\pm61 pc. Multiple light echoes with S/N > 2.5 reside at smaller radii on ~277 days but become less significant on ~416 days indicating a complex structure of foreground interstellar medium (ISM). The light echo shows bluer color than predicted under a Rayleigh scattering case. We also found the light echo brightened from V_{echo}=21.68\pm0.07 on 2014 September 5, to V_{echo}=21.05\pm0.08 on 2014 November 6, suggesting an enhancement of echoing materials at different distances projected on to the plane of the sky.