Direct measurements of dust attenuation in z ∼ 1.5 star-forming galaxies from 3D-HST: Implications for dust geometry and star formation rates
- Astronomy Department, University of California, Berkeley, CA 94720 (United States)
- Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
- Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)
- Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany)
- Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)
- Department of Astronomy, University of Wisconsin, 475 N Charter Street, Madison, WI 53706 (United States)
- Department of Astronomy, Yale University, New Haven, CT 06511 (United States)
- South African Astronomical Observatory, P.O. Box 9, Observatory 7935 (South Africa)
The nature of dust in distant galaxies is not well understood, and until recently few direct dust measurements have been possible. We investigate dust in distant star-forming galaxies using near-infrared grism spectra of the 3D-HST survey combined with archival multi-wavelength photometry. These data allow us to make a direct comparison between dust around star-forming regions (A {sub V,} {sub H} {sub II}) and the integrated dust content (A {sub V,} {sub star}). We select a sample of 163 galaxies between 1.36 ≤ z ≤ 1.5 with Hα signal-to-noise ratio ≥5 and measure Balmer decrements from stacked spectra to calculate A {sub V,} {sub H} {sub II}. First, we stack spectra in bins of A {sub V,} {sub star}, and find that A {sub V,} {sub H} {sub II} = 1.86 A {sub V,} {sub star}, with a significance of σ = 1.7. Our result is consistent with the two-component dust model, in which galaxies contain both diffuse and stellar birth cloud dust. Next, we stack spectra in bins of specific star formation rate (log SSFR), star formation rate (log SFR), and stellar mass (log M {sub *}). We find that on average A {sub V,} {sub H} {sub II} increases with SFR and mass, but decreases with increasing SSFR. Interestingly, the data hint that the amount of extra attenuation decreases with increasing SSFR. This trend is expected from the two-component model, as the extra attenuation will increase once older stars outside the star-forming regions become more dominant in the galaxy spectrum. Finally, using Balmer decrements we derive dust-corrected Hα SFRs, and find that stellar population modeling produces incorrect SFRs if rapidly declining star formation histories are included in the explored parameter space.
- OSTI ID:
- 22356647
- Journal Information:
- Astrophysical Journal, Vol. 788, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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