SPATIALLY RESOLVED DUST MAPS FROM BALMER DECREMENTS IN GALAXIES AT z ∼ 1.4

Abstract

ABSTRACT We derive average radial gradients in the dust attenuation toward H ii regions in 609 galaxies at z ∼ 1.4, using measurements of the Balmer decrement out to r ∼ 3 kpc. The Balmer decrements are derived from spatially resolved maps of Hα and Hβ emission from the 3D-HST survey. We find that with increasing stellar mass M both the normalization and strength of the gradient in dust attenuation increases. Galaxies with a mean mass of ⟨ log M ⟩ = 9.2 ?> M ⊙ have little dust attenuation at all radii, whereas galaxies with ⟨ log M ⟩ = 10.2 ?> M ⊙ have A Hα ≈ 2 mag in their central regions. We parameterize this as A H &agr; = b + c log r ?> , with b = 0.9 + log 1.0 M 10 ?> , c = −1.9–2.2 log M 10, r in kpc, and M 10 the stellar mass in units of 1010 M ⊙. This expression can be used to correct spatially resolved measurements of Hα to radial distributions of star formation. When applied to our data, we find that the star formation rates (SFRs) in the central r < 1 kpc of galaxies in the highest mass bin are ∼6 M ⊙ yr−1, six times higher than before correction and approximately half of the total SFR of these galaxies. If this high central SFR is maintained for several Gyr, a large fraction of the stars in present-day bulges likely formed in situ.