Magellanic Clues to Spatially-resolved Extinction Corrections for Distant Galaxies in the HST/JWST Era
Abstract
Extinction by dust hampers our understanding of galaxies at all redshifts, and is not constant within or across the face of a galaxy, nor from galaxy to galaxy. We presented an empirical method to correct galaxy images for extinction due to interstellar dust on a pixel by pixel basis, using only rest-frame 3.6 and 0.55 micron images. While this "β_V" method is approximate in nature, in its first application to a nearby spiral galaxy we produced extinction maps and revealed hidden coherent galaxy structures like a stellar bar and ridges of dust, while anomalous inferred central extinctions in several earlier-type disk galaxies proved powerful tracers of hidden AGN. This method is particularly promising for deep mid-IR imaging surveys with the James Webb Space Telescope in fields covered by HST in visible light, since their resolutions will be well-matched. Here we report on our follow-up investigation to explore the applicability, robustness, and fidelity of the β_V method on linear size scales from pc to kpc and in regions of varying star formation histories, metallicities, and dust content/distribution. We do so by combining WISE 3.4(Spitzer/IRAC 3.6) micron images of the LMC and SMC ---the nearest astrophysical laboratories with a range of sub-solar metallicities--- with 2MASS near-IR and OGLE-III multi-year V and I reference images and catalogs. We assess at ~1" 0.25--0.35pc) resolution the properties of the stellar populations that contribute to the flux in each WISE(IRAC) resolution element using the 2MASS and OGLE-III data. That allows us to measure the observed and derive through modelling the inherent V-to-3.4(3.6) micron flux ratio per WISE(IRAC) resolution element. Subsequent resampling and PSF-matching at geometrically increasing scales from pc to kpc resolution elements allows us to assess the accuracy and fidelity of the method as a multi-variate function of the resolution, underlying stellar population mixture, physical environments, and projected distribution of dust. Resulting predicted β_{V,0} will serve as calibrations for the spatially-resolved extinction correction of galaxies at all redshifts where the method is proved reliable. This work is funded by NASA/ADAP grant NNX12AE47G.
- Publication:
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American Astronomical Society Meeting Abstracts #223
- Pub Date:
- January 2014
- Bibcode:
- 2014AAS...22324620J