Feasibility of the debris ring transit method for the solar-like star HD 107146 by an occulted galaxy

TL;DR

This study explores using the transit of a debris ring around HD 107146 to measure dust properties by analyzing occulted background galaxy images from HST observations in 2004 and 2011.

Contribution

It demonstrates the feasibility of debris ring transit photometry for optical depth increases of 0.04 or more using high-resolution HST data.

Findings

Debris ring transit photometry can detect optical depth changes of Δτ ≥ 0.04.

Modeling the background galaxy with an exponential disk and Sersic profile is effective.

Irregularities from star-forming regions limit precise dust distribution measurements.

Abstract

Occulting galaxy pairs have been used to determine the transmission and dust composition within the foreground galaxy. Observations of the nearly face-on ring-like debris disk around the solar-like star HD 107146 by HST/ACS in 2004 and HST/STIS in 2011 reveal that the debris ring is occulting an extended background galaxy over the subsequent decades. Our aim is to use 2004 HST observations of this system to model the galaxy and apply this to the 2011 observation in order to measure the transmission of the galaxy through the outer regions of the debris disk. We model the galaxy with an exponential disk and a S\'{e}rsic pseudo-bulge in the V- and I-band, but irregularities due to small scale structure from star forming regions limits accurate determination of the foreground dust distribution. We show that debris ring transit photometry is feasible for optical depth increases of $\Delta \tau \geq$ 0.04 ($1 \sigma$) on tens of au scales the width of the background galaxy { when the 2011 STIS data are compared directly with new HST/STIS observations, instead of the use of a smoothed model as a reference.