Bibcode
Meidt, S.; Schinnerer, E.; Querejeta, M.; van de Ven, G.; Zaritsky, D. F.; Peletier, R.; Knapen, J.; Sheth, K.; S4G; DAGAL
Bibliographical reference
American Astronomical Society, AAS Meeting #223, #453.16
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1
2014
Citations
0
Refereed citations
0
Description
We present a new approach for estimating the 3.6 μm stellar
mass-to-light ratio Υ3.6 in terms of the [3.6]-[4.5]
colors of old stellar populations. Our approach avoids several of the
largest sources of uncertainty in existing techniques using population
synthesis models. By focusing on mid-IR wavelengths, we gain a virtually
dust extinction-free tracer of the old stars, avoiding the need to adopt
a dust model to correctly interpret optical or optical/NIR colors
normally leveraged to assign the mass-to-light ratio Υ. By
calibrating a new relation between NIR and mid-IR colors of giant stars
observed in GLIMPSE we also avoid the discrepancies in model predictions
for the [3.6]-[4.5] colors of old stellar populations due to
uncertainties in the molecular line opacities assumed in template
spectra. We find that the [3.6]-[4.5] color, which is driven primarily
by metallicity, provides a tight constraint on Υ3.6,
which varies intrinsically less than at optical wavelengths. The
uncertainty on Υ3.6 of ~0.07 dex due to unconstrained
age variations marks a significant improvement on existing techniques
for estimating the stellar M/L with shorter wavelength data. A single
Υ3.6=0.6 (assuming a Chabrier IMF), independent of
[3.6]-[4.5] color, is also feasible as it can be applied simultaneously
to old, metal-rich and young, metal-poor populations, and still with
comparable (or better) accuracy 0.1 dex) as alternatives. Our
Υ3.6 is optimal for mapping stellar mass
distributions in S4G/DAGAL, for which we are first
constructing a new catalog of images using an Independent Component
Analysis technique to isolate the old stellar light at 3.6 μm from
non-stellar emission (e.g. hot dust and the 3.3 μm PAH feature). Our
estimate should also be useful for determining the fractional
contribution of non-stellar emission to global (rest-frame) 3.6 μm
fluxes, e.g., in WISE imaging and establishes a reliable basis for
exploring variations in the stellar IMF.