THE MOSDEF SURVEY: MEASUREMENTS OF BALMER DECREMENTS AND THE DUST ATTENUATION CURVE AT REDSHIFTS z ∼ 1.4–2.6

By Naveen A. Reddy, M. Kriek, A. Shapley, William Robert Freeman, B. Siana, A. Coil, B. Mobasher, S. Price, R. Sanders, I. Shivaei. 2015

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We present results on the dust attenuation curve of z ∼ 2 galaxies using early observations from the MOSFIRE Deep Evolution Field survey. Our sample consists of 224 star-forming galaxies with zspec = 1.36–2.59 and high signal-to-noise ratio measurements of Hα and Hβ obtained with Keck/MOSFIRE. We construct composite spectral energy distributions (SEDs) of galaxies in bins of Balmer decrement to measure the attenuation curve. We find a curve that is similar to the SMC extinction curve at λ ≳ 2500 Å. At shorter wavelengths, the shape is identical to that of the Calzetti et al. relation, but with a lower normalization. Hence, the new attenuation curve results in star formation rates (SFRs) that are ≈ 20 % ?> lower, and stellar masses that are Δ log ( M * / M ⊙ ) ≃ 0.16 ?> dex lower, than those obtained with the Calzetti relation. We find that the difference in the total attenuation of the ionized gas and stellar continuum correlates strongly with SFR, such that for dust-corrected SFRs ≳ 20 M⊙ yr−1, assuming a Chabrier initial mass function, the nebular emission lines suffer an increasing degree of obscuration relative to the continuum. A simple model that can account for these trends is one in which the UV through optical stellar continuum is dominated by a population of less-reddened stars, while the nebular line and bolometric luminosities become increasingly dominated by dustier stellar populations for galaxies with large SFRs, as a result of the increased dust enrichment that accompanies such galaxies. Consequently, UV- and SED-based SFRs may underestimate the total SFR at even modest levels of ≈20 M⊙ yr−1.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/403709b0a4a11bfe084be7ebcfb3b99f6d9d475a

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In Astronomy and Astrophysics

1. P. Hopkins
2. P. V. van Dokkum
3. C. Conroy
4. R. Dav'e
5. L. Hernquist
6. M. Franx
7. I. Labbé
8. Naveen A. Reddy

Citations in the corpus

• An extreme [O III] emitter at z = 3.2: a low metallicity Lyman continuum source (2015, methodology): “However, Scoville et al. (2015) report that their data are consistent with the presence of the 2175Å bump, while for Reddy et al. (2015) this presence is only marginal.”
• Deriving Physical Properties from Broadband Photometry with Prospector: Description of the Model and a Demonstration of its Accuracy Using 129 Galaxies in the Local Universe (2016, background): “…with serious differences between the Milky Way (Cardelli et al. 1989), Small Magellanic Cloud (SMC; Prevot et al. 1984; Bouchet et al. 1985), and Large Magellanic Cloud (LMC; Fitzpatrick 1986), as well as in high redshift galaxies (Buat et al. 2012; Reddy et al. 2015; Salmon et al. 2016).”
• THE MOSDEF SURVEY: ELECTRON DENSITY AND IONIZATION PARAMETER AT z ∼ 2.3 (2015, methodology): “These strong optical emission lines are powerful diagnostics for determining physical properties of galaxies including dust content (Reddy et al. 2015), starformation rate (SFR) (Shivaei et al. 2015), chemical abundance (Sanders et al. 2015), gas density, ionization state, and black hole activity…”
• CIGALE: a python Code Investigating GALaxy Emission (2018, background): “Numerous studies have focussed on determining attenuation laws in galaxies, finding a remarkable diversity (e.g. Wild et al. 2011; Reddy et al. 2015, 2016; Lo Faro et al. 2017; Buat et al. 2018; Salim et al. 2018, Decleir et al., in prep., and many others).”
• Dust Attenuation Curves in the Local Universe: Demographics and New Laws for Star-forming Galaxies and High-redshift Analogs (2018, methodology): “The curve of Reddy et al. (2015) derived from z ∼ 2 galaxies using the methodology of Calzetti et al. (1994, 2000) is less steep than ours (green dashed curve).”
• RECONCILING THE STELLAR AND NEBULAR SPECTRA OF HIGH-REDSHIFT GALAXIES (2016, background): “There is a rapidly developing literature comparing dust attenuation factors estimated from nebular line ratios to those estimated from continuum reddening (e.g., Calzetti et al. 2000; Kashino et al. 2013; Price et al. 2014; Reddy et al. 2015; Shivaei et al. 2016).”
• The HDUV Survey: A Revised Assessment of the Relationship between UV Slope and Dust Attenuation for High-redshift Galaxies (2017, methodology): “In particular, Reddy et al. (2015) found that a significant fraction of z ∼ 2 galaxies with M∗ .”
• ALMA SPECTROSCOPIC SURVEY IN THE HUBBLE ULTRA DEEP FIELD: THE INFRARED EXCESS OF UV-SELECTED z = 2–10 GALAXIES AS A FUNCTION OF UV-CONTINUUM SLOPE AND STELLAR MASS (2016, background): “This is perhaps most clearly seen inspecting Figure 20 of Reddy et al. (2015) where galaxies with SFRs .10 M⊙/yr show an Hα/Hβ flux ratio of approximately ∼3, very close to the intrinsic ratio.”
• Near infrared spectroscopy and star-formation histories of 3 ≤ z ≤ 4 quiescent galaxies (2018, background): “While it is usually assumed that emission lines suffer more attenuation than the stellar continuum (e.g., Calzetti et al. 2000), recent results suggest this reddening excess becomes negligible at high redshifts (e.g., Pannella et al. 2015; Reddy et al. 2015).”
• FORMING COMPACT MASSIVE GALAXIES (2015, unknown): “The measured dispersions 16 We refer to other studies for more detailed analysis of the attenuation toward HII regions (e.g., Price et al. 2014, Reddy et al. 2015). are a complex function of the dynamics and gas distribution in the galaxies: σ2gas∼ α2V2rotsin2(i) +σ2ISM + w2(i)σ2wind, (17) with α∼…”
• (Star)bursts of FIRE: observational signatures of bursty star formation in galaxies (2015, background): “…et al. 2012) at the Keck Observatory, are making it possible to more accurately constrain this ratio by providing rest-frame-optical spectra (which are required – but not necessarily sufficient – to accurately correct for dust attenuation; Reddy et al. 2015) for thousands of high-redshift galaxies.”