Age and Dust Degeneracy for Starburst Galaxies Solved?

Abstract

A spectral evolution model of galaxies that includes both stellar and dust effects is newly built. xApplying the model to 22 nearby starburst galaxies, we have shown that far infrared luminosity of galaxies helps to break the age-dustiness degeneracy. We have derived a unique solution of age and the dustiness for each starburst galaxy. The resulting starburst ages and optical depths are in the range $10 \le t (Myr) \le 500$ and $0.5 \le τ_{V} \le 5.0$, respectively. The result is robust and is almost independent of model assumptions such as dust distributions, extinction curves, and burst strengths. With the rapidly growing sensitivity of submillimeter detectors, it should become possible in the near future to determine the age and $τ_{V}$ of star-forming galaxies at redshifts $z \simeq 3$ and beyond. Accurate estimates of $τ_{V}$ for Lyman-break galaxies and high-z galaxies might require a substantial revision of the previously claimed picture of star formation history over the Hubble time.