Ground- and Space-Based Dust Observations of VV 191 Overlapping Galaxy Pair
arxiv(2024)
摘要
The Balmer decrement (Hα/Hβ) provides a constraint on
attenuation, the cumulative effects of dust grains in the ISM. The ratio is a
reliable spectroscopic tool for deriving the dust properties of galaxies that
determine many different quantities such as star formation rate, metallicity,
and SED models. Here we measure independently both the attenuation and
Hα/Hβ of an occulting galaxy pair: VV 191. Attenuation
measurements in the visible spectrum (A_V,stars) from dust maps derived
from the F606W filter of HST and the F090W filter of JWST are matched with
spaxel-by-spaxel Hα/Hβ observations from the George and Cynthia
Mitchell Spectrograph (GCMS) of the McDonald Observatory. The 0.5 to 0.7 micron
bandpass covers the Balmer lines for VV 191. The dust maps of JWST and HST
provide the high sensitivity necessary for comparisons and tracking trends of
the geometrically favorable galaxy. We present maps and plots of the Balmer
lines for the VV 191 galaxy pair and for a specific region highlighting dust
lanes for VV 191b in the overlap region. We compute A_V, HII from
Hα/Hβ and plot both quantities against A_V, stars. Our results
show that regions with higher dust content, residing closer to the spiral
center, dominate ionized gas attenuation, leading to an overestimation of
A_V, HII by a factor or 2. Further out in the spiral arms, the lower dust
content leads to more agreement between the attenuations, indicating lower SFR
and larger contribution from older stars to the stellar continuum outside the
Petrosian radius.
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