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1. An Updated Dust-to-Star Geometry: Dust Attenuation Does Not Depend on Inclination in 1.3 ≤z ≤2.6 Star-forming Galaxies from MOSDEF

   https://doi.org/10.3847/1538-4357/accdd1  

   Lorenz, Brian; Kriek, Mariska; Shapley, Alice E.; Reddy, Naveen A.; Sanders, Ryan L.; Barro, Guillermo; Coil, Alison L.; Mobasher, Bahram; Price, Sedona H.; Runco, Jordan N.; et al (June 2023, The Astrophysical Journal)

   Abstract We investigate dust attenuation and its dependence on viewing angle for 308 star-forming galaxies at 1.3 ≤z≤ 2.6 from the MOSFIRE Deep Evolution Field survey. We divide galaxies with a detected Hαemission line and coverage of Hβinto eight groups by stellar mass, star formation rate (SFR), and inclination (i.e., axis ratio), and we then stack their spectra. From each stack, we measure the Balmer decrement and gas-phase metallicity, and then we compute the medianA_Vand UV continuum spectral slope (β). First, we find that none of the dust properties (Balmer decrement,A_V, orβ) varies with the axis ratio. Second, both stellar and nebular attenuation increase with increasing galaxy mass, showing little residual dependence on SFR or metallicity. Third, nebular emission is more attenuated than stellar emission, and this difference grows even larger at higher galaxy masses and SFRs. Based on these results, we propose a three-component dust model in which attenuation predominantly occurs in star-forming regions and large, dusty star-forming clumps, with minimal attenuation in the diffuse ISM. In this model, nebular attenuation primarily originates in clumps, while stellar attenuation is dominated by star-forming regions. Clumps become larger and more common with increasing galaxy mass, creating the above mass trends. Finally, we argue that a fixed metal yield naturally leads to mass regulating dust attenuation. Infall of low-metallicity gas increases the SFR and lowers the metallicity, but leaves the dust column density mostly unchanged. We quantify this idea using the Kennicutt–Schmidt and fundamental metallicity relations, showing that galaxy mass is indeed the primary driver of dust attenuation. 

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2. Modeling Galaxies in the Early Universe with Supernova Dust Attenuation

   https://doi.org/10.3847/2041-8213/add15d  

   McKinney, Jed; Cooper, Olivia R; Casey, Caitlin M; Muñoz, Julian B; Akins, Hollis; Lambrides, Erini; Long, Arianna S (May 2025, The Astrophysical Journal Letters)

   Abstract Supernovae (SNe) may be the dominant channel by which dust grains accumulate in galaxies during the first Gyr of cosmic time as formation channels important for lower-redshift galaxies, e.g., asymptotic giant branch stars and grain growth, may not have had sufficient time to take over. SNe produce fewer small grains, leading to a flatter attenuation law. In this work, we fit observations of 138 spectroscopically confirmedz > 6 galaxies adopting standard spectral energy distribution (SED) modeling assumptions and compare standard attenuation law prescriptions to a flat attenuation law. Compared to SMC dust, flat attenuation close to what may be expected from dust produced in SNe yields up to 0.5 mag higherA_Vand 0.4 dex larger stellar masses. It also finds better fits to the rest-frame UV photometry with lower ${\chi }_{\mathrm{UV}}^2$, allowing the observed UV luminosities taken from the models to be fainter by 0.2 dex on average. The systematically fainter observed UV luminosities for fixed observed photometry could help resolve current tension between the ionizing photon production implied by JWST observations and the redshift evolution of the neutral hydrogen fraction. Given these systematic effects and the physical constraint of cosmic time itself, fairly flat attenuation laws that could represent the properties of dust grains produced by SNe should be a standard consideration in fitting to the SEDs ofz > 6 galaxies. 

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3. The MOSFIRE Deep Evolution Field Survey: Implications of the Lack of Evolution in the Dust Attenuation–Mass Relation to z ∼ 2*

   https://doi.org/10.3847/1538-4357/ac4742  

   Shapley, Alice E.; Sanders, Ryan L.; Salim, Samir; Reddy, Naveen A.; Kriek, Mariska; Mobasher, Bahram; Coil, Alison L.; Siana, Brian; Price, Sedona H.; Shivaei, Irene; et al (February 2022, The Astrophysical Journal)

   Abstract We investigate the relationship between dust attenuation and stellar mass (M_*) in star-forming galaxies over cosmic time. For this analysis, we compare measurements from the MOSFIRE Deep Evolution Field survey atz∼ 2.3 and the Sloan Digital Sky Survey (SDSS) atz∼ 0, augmenting the latter optical data set with both UV Galaxy Evolution Explorer (GALEX) and mid-infrared Wide-field Infrared Survey Explorer (WISE) photometry from the GALEX-SDSS-WISE Catalog. We quantify dust attenuation using both spectroscopic measurements of Hαand Hβemission lines, and photometric measurements of the rest-UV stellar continuum. The Hα/Hβratio is used to determine the magnitude of attenuation at the wavelength of Hα,A_Hα. Rest-UV colors and spectral energy distribution fitting are used to estimateA₁₆₀₀, the magnitude of attenuation at a rest wavelength of 1600 Å. As in previous work, we find a lack of significant evolution in the relation between dust attenuation andM_*over the redshift rangez∼ 0 toz∼ 2.3. Folding in the latest estimates of the evolution ofM_dust, (M_dust/M_gas), and gas surface density at fixedM_*, we find that the expectedM_dustand dust mass surface density are both significantly higher atz∼ 2.3 than atz∼ 0. These differences appear at odds with the lack of evolution in dust attenuation. To explain the striking constancy in attenuation versusM_*, it is essential to determine the relationship between metallicity and (M_dust/M_gas), the dust mass absorption coefficient and dust geometry, and the evolution of these relations and quantities fromz∼ 0 toz∼ 2.3. 

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4. Constraining bursty star formation histories with galaxy UV and H α luminosity functions and clustering

   https://doi.org/10.1088/1475-7516/2025/04/034  

   Sun, Guochao; Muñoz, Julian B; Mirocha, Jordan; Faucher-Giguère, Claude-André (April 2025, Journal of Cosmology and Astroparticle Physics)

   Abstract The observed prevalence of galaxies exhibiting bursty star formation histories (SFHs) atz≳ 6 has created new challenges and opportunities for understanding their formation pathways. The degenerate effects of the efficiency and burstiness of star formation on the observed UV luminosity function are separable by galaxy clustering. However, quantifying the timescales of burstiness requires more than just the continuum UV measurements. Here we develop a flexible semi-analytic framework for modeling both the amplitude of star formation rate (SFR) variations and their temporal correlation, from which the luminosity function and clustering can be derived for SFR indicators tracing different characteristic timescales (e.g., UV continuum and Hα luminosities). Based on this framework, we study the prospect of using galaxy summary statistics to distinguish models where SFR fluctuations are prescribed by different power spectral density (PSD) forms. Using the Fisher matrix approach, we forecast the constraints on parameters in our PSD-based model that can be extracted from mock JWST observations of the UV and Hαluminosity functions and clustering bias factors atz∼ 6. If potential confusion due to e.g., dust attenuation and stellar population effects can be properly quantified, these results imply the possibility of probing the burstiness of high-zgalaxies with one-point and two-point statistics and highlight the benefits of combining long-term and short-term SFR tracers. Our flexible framework can be readily extended to characterize the SFH of high-redshift galaxies with a wider range of observational diagnostics. 

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5. CLEAR: Paschen-β Star Formation Rates and Dust Attenuation of Low-redshift Galaxies

   https://doi.org/10.3847/1538-4357/ac5a4c  

   Cleri, Nikko J.; Trump, Jonathan R.; Backhaus, Bren E.; Momcheva, Ivelina; Papovich, Casey; Simons, Raymond; Weiner, Benjamin; Estrada-Carpenter, Vicente; Finkelstein, Steven L.; Giavalisco, Mauro; et al (April 2022, The Astrophysical Journal)

   Abstract We use Paschen- β (Pa β ; 1282 nm) observations from the Hubble Space Telescope G141 grism to study the star formation and dust-attenuation properties of a sample of 29 low-redshift ( z < 0.287) galaxies in the CANDELS Ly α Emission at Reionization survey. We first compare the nebular attenuation from Pa β /H α with the stellar attenuation inferred from the spectral energy distribution, finding that the galaxies in our sample are consistent with an average ratio of the continuum attenuation to the nebular gas of 0.44, but with a large amount of excess scatter beyond the observational uncertainties. Much of this scatter is linked to a large variation between the nebular dust attenuation as measured by (space-based) Pa β to (ground-based) H α to that from (ground-based) H α /H β . This implies there are important differences between attenuation measured from grism-based/wide-aperture Pa β fluxes and the ground-based/slit-measured Balmer decrement. We next compare star formation rates (SFRs) from Pa β to those from dust-corrected UV. We perform a survival analysis to infer a census of Pa β emission implied by both detections and nondetections. We find evidence that galaxies with lower stellar mass have more scatter in their ratio of Pa β to attenuation-corrected UV SFRs. When considering our Pa β detection limits, this observation supports the idea that lower-mass galaxies experience “burstier” star formation histories. Together, these results show that Pa β is a valuable tracer of a galaxy’s SFR, probing different timescales of star formation and potentially revealing star formation that is otherwise missed by UV and optical tracers. 

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