Strong Lensing Model and Dust Extinction Maps of the Host Galaxy of Type Ia Supernova H0pe

TL;DR

This paper develops a detailed strong lensing model of galaxy cluster G165 using multiple image constraints, including extended surface brightness, to improve mass estimates and map dust extinction in the host galaxy of SN H0pe, a high-redshift Type Ia supernova.

Contribution

It introduces an extended-image modeling approach that significantly reduces uncertainties in lens models and enables spatially resolved analysis of host galaxy dust properties.

Findings

Extended-image modeling reduces mass model uncertainties by over an order of magnitude.

The supernova exploded in a high-extinction region (~0.9 mag) about 1 kpc from the host galaxy center.

The dust extinction estimate agrees within 1σ with independent spectral energy distribution fitting methods.

Abstract

Strong gravitational lensing by massive galaxy clusters offers rare opportunities to observe multiple images of distant ($z \gtrsim 2$) Type Ia supernovae (SNe) and to resolve the properties of their host galaxies. A recent outstanding example is the Type Ia SN H0pe ($z = 1.78$), which the James Webb Space Telescope (JWST) discovered in NIRCam images, when the galaxy cluster PLCK G165.7+67.0 (G165, $z = 0.35$) still produced three images of it. In this work, we build a new strong lensing model of G165, first using only the positions of multiple images of background galaxies. We then significantly increase the number of constraints around the position of SN H0pe by modeling the extended surface brightness of the SN host galaxy. Including extended image information reduces the average uncertainty on mass model parameters by more than an order of magnitude. We also study the spatial distribution of dust in the arc to estimate the dust extinction at the position of SN H0pe. We find good statistical agreement of the extinction estimate, at $\lesssim 1\sigma$, with three fully independent methods based on spectral energy distribution fitting. Moreover, our extended-image lens model of G165 allows us to map the dust distribution of the host galaxy from the image plane to the source plane. Supernova H0pe exploded in a region with a relatively high extinction ($A_V \approx 0.9$ mag) at around $\sim 1$ kpc from its host center. This work shows that extended image modeling in lensing clusters simultaneously reduces the uncertainty on lens model parameters and enables spatially resolved analyses of lensed transients' host galaxies. Such modeling advances are expected to play an important role in future cosmological analyses using strongly lensed SNe.