THE DUST ATTENUATION LAW IN DISTANT GALAXIES: EVIDENCE FOR VARIATION WITH SPECTRAL TYPE
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This Letter utilizes composite spectral energy distributions (SEDs) constructed from NEWFIRM Medium-Band Survey photometry to constrain the dust attenuation curve in 0.5 < z < 2.0 galaxies. Based on similarities between the full SED shapes (0.3–8 μm), we have divided galaxies in 32 different spectral classes and stacked their photometry. As each class contains galaxies over a range in redshift, the resulting rest-frame SEDs are well sampled in wavelength and show various spectral features including Hα and the UV dust bump at 2175 Å. We fit all composite SEDs with flexible stellar population synthesis models, while exploring attenuation curves with varying slopes and UV bump strengths. The Milky Way and Calzetti law provide poor fits at UV wavelengths for nearly all SEDs. Consistent with previous studies, we find that the best-fit attenuation law varies with spectral type. There is a strong correlation between the best-fit dust slope and UV bump strength, with steeper laws having stronger bumps. Moreover, the attenuation curve correlates with specific star formation rate (SFR), with more active galaxies having shallower dust curves and weaker bumps. There is also a weak correlation with inclination. The observed trends can be explained by differences in the dust-to-star geometry, a varying grain size distribution, or a combination of both. Our results have several implications for galaxy evolution studies. First, the assumption of a universal dust model leads to biases in derived galaxy properties. Second, the presence of a dust bump may result in underestimated values for the UV slope, used to correct SFRs of distant galaxies.
Subfields: Astronomy and Astrophysics, Instrumentation
View Paper: https://www.semanticscholar.org/paper/3427dac0abfc2eb93a547b5697b5f06487de876e
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Citations in the corpus
- Dust Attenuation Curves in the Local Universe: Demographics and New Laws for Star-forming Galaxies and High-redshift Analogs (2018, methodology): “This agrees with the trends in the right panels of Figure 4, and has been detected even at higher redshifts (Kriek & Conroy 2013; Tress et al. 2018).”
- Dusty Star Forming Galaxies at High Redshift (2014, background): “…are calculated—whether it be from restframe UV, optical, emission line, or infrared indicators, and whether or not corrections for extinction and dust attenuation are well understood or should be re-calibrated (e.g. as Kriek and Conroy, 2013, show is necessary for massive early-type galaxies).”
- CONSTRAINING THE LOW-MASS SLOPE OF THE STAR FORMATION SEQUENCE AT 0.5 < z < 2.5 (2014, background): “…bands included in the fit, their respective width, and the redshift of the object: for surveys with a large number of bands the effect of emission line contamination will be somewhat washed out; however, for surveys with fewer bands this effect can be quite significant (e.g., Kriek & Conroy 2013).”
- GOODS-HERSCHEL: STAR FORMATION, DUST ATTENUATION, AND THE FIR–RADIO CORRELATION ON THE MAIN SEQUENCE OF STAR-FORMING GALAXIES UP TO z ≃ 4 (2014, background): “On the other hand, Buat et al. (2012); Kriek & Conroy (2013) have suggested that the presence of a dust bump, the feature at 2175Å, in the spectra of high redshift galaxies, may result in underestimated values for the UV slope.”
- 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, methodology): “We tie the strength of the UV dust absorption bump to the best-fit diffuse dust attenuation index, following the results of Kriek & Conroy (2013).”
- Inferring the star formation histories of massive quiescent galaxies with bagpipes: evidence for multiple quenching mechanisms (2017, methodology): “We use the BC03 models and the Calzetti et al. (2000) attenuation curve, which has been shown recently to be a robust average of the attenuation curves observed for galaxies across a wide range of redshifts (e.g. Cullen et al. 2017a,b; McLure et al. 2017; but see Kriek & Conroy 2013).”
- THE MOSFIRE DEEP EVOLUTION FIELD (MOSDEF) SURVEY: REST-FRAME OPTICAL SPECTROSCOPY FOR ∼1500 H-SELECTED GALAXIES AT 1.37 ≤ z ≤ 3.8 ?> (2014, methodology): “Consequently, we are reliant on stellar population modeling and the UV slope β, whose use for estimating dust attenuation in particular types of galaxies has been called into question by many studies (e.g., Kong et al. 2004; Siana et al. 2009; Reddy et al. 2010; Kriek & Conroy 2013).”
- A HIGHLY CONSISTENT FRAMEWORK FOR THE EVOLUTION OF THE STAR-FORMING “MAIN SEQUENCE” FROM z ∼ 0–6 (2014, methodology): “Using a flexible parametrization of dust attenuation, Kriek & Conroy (2013) report a negative correlation between the slope of the attenuation curve and the strength of the 2175 Å bump (i.e., SED types with steeper attenuation curves have stronger bumps.).”
- THE MOSDEF SURVEY: MEASUREMENTS OF BALMER DECREMENTS AND THE DUST ATTENUATION CURVE AT REDSHIFTS z ∼ 1.4–2.6 (2015, background): “In another recent study, Kriek & Conroy (2013) examine a sample of somewhat lower-redshift (0.5 z 2.0) galaxies and find that the strength of the 2175 Å absorption correlates with the “steepness” (i.e., the wavelength dependence) of the attenuation curve.”
- THE RELATION BETWEEN STAR FORMATION RATE AND STELLAR MASS FOR GALAXIES AT 3.5 ⩽ z ⩽ 6.5 IN CANDELS (2014, background): “…starburst attenuation has been known to produce unphysically young stellar population ages for UV selected samples, with best–fit ages often at the edge of the parameter space (Fontana et al. 2004; Reddy et al. 2012; Oesch et al. 2013; Kriek & Conroy 2013; Chevallard et al. 2013; Buat et al. 2014).”