We present dust attenuation properties of spectroscopically confirmed star forming galaxies on the main sequence at a redshift of ∼4.4 - 5.8. Our analyses are based on the far infrared continuum observations of 118 galaxies at rest-frame 158 μm obtained with the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE). We study the connection between the ultraviolet (UV) spectral slope (β), stellar mass (M∗), and infrared excess (IRX = LIR/LUV). Twenty-three galaxies are individually detected in the continuum at > 3.5σ significance. We perform a stacking analysis using both detections and nondetections to study the average dust attenuation properties at z ∼ 4.4 - 5.8. The individual detections and stacks show that the IRX-β relation at z ∼ 5 is consistent with a steeper dust attenuation curve than typically found at lower redshifts (z < 4). The attenuation curve is similar to or even steeper than that of the extinction curve of the Small Magellanic Cloud. This systematic change of the IRX-β relation as a function of redshift suggests an evolution of dust attenuation properties at z > 4. Similarly, we find that our galaxies have lower IRX values, up to 1 dex on average, at a fixed mass compared to previously studied IRX-M∗ relations at z 4, albeit with significant scatter. This implies a lower obscured fraction of star formation than at lower redshifts. Our results suggest that dust properties of UV-selected star forming galaxies at z 4 are characterised by (i) a steeper attenuation curve than at z 4, and (ii) a rapidly decreasing dust obscured fraction of star formation as a function of redshift. Nevertheless, even among this UV-selected sample, massive galaxies (log M∗/M· > 10) at z ∼ 5 - 6 already exhibit an obscured fraction of star formation of ∼45%, indicating a rapid build-up of dust during the epoch of reionization.
The ALPINE-ALMA [CII] survey: Dust attenuation properties and obscured star formation at z ∼4.4-5.8 / Fudamoto Y.; Oesch P.A.; Faisst A.; Bethermin M.; Ginolfi M.; Khusanova Y.; Loiacono F.; Le Fevre O.; Capak P.; Schaerer D.; Silverman J.D.; Cassata P.; Yan L.; Amorin R.; Bardelli S.; Boquien M.; Cimatti A.; Dessauges-Zavadsky M.; Fujimoto S.; Gruppioni C.; Hathi N.P.; Ibar E.; Jones G.C.; Koekemoer A.M.; Lagache G.; Lemaux B.C.; Maiolino R.; Narayanan D.; Pozzi F.; Riechers D.A.; Rodighiero G.; Talia M.; Toft S.; Vallini L.; Vergani D.; Zamorani G.; Zucca E.. - In: ASTRONOMY & ASTROPHYSICS. - ISSN 0004-6361. - ELETTRONICO. - 643:(2020), pp. A4.0-A4.0. [10.1051/0004-6361/202038163]
The ALPINE-ALMA [CII] survey: Dust attenuation properties and obscured star formation at z ∼4.4-5.8
Ginolfi M.;
2020
Abstract
We present dust attenuation properties of spectroscopically confirmed star forming galaxies on the main sequence at a redshift of ∼4.4 - 5.8. Our analyses are based on the far infrared continuum observations of 118 galaxies at rest-frame 158 μm obtained with the Atacama Large Millimeter Array (ALMA) Large Program to INvestigate [CII] at Early times (ALPINE). We study the connection between the ultraviolet (UV) spectral slope (β), stellar mass (M∗), and infrared excess (IRX = LIR/LUV). Twenty-three galaxies are individually detected in the continuum at > 3.5σ significance. We perform a stacking analysis using both detections and nondetections to study the average dust attenuation properties at z ∼ 4.4 - 5.8. The individual detections and stacks show that the IRX-β relation at z ∼ 5 is consistent with a steeper dust attenuation curve than typically found at lower redshifts (z < 4). The attenuation curve is similar to or even steeper than that of the extinction curve of the Small Magellanic Cloud. This systematic change of the IRX-β relation as a function of redshift suggests an evolution of dust attenuation properties at z > 4. Similarly, we find that our galaxies have lower IRX values, up to 1 dex on average, at a fixed mass compared to previously studied IRX-M∗ relations at z 4, albeit with significant scatter. This implies a lower obscured fraction of star formation than at lower redshifts. Our results suggest that dust properties of UV-selected star forming galaxies at z 4 are characterised by (i) a steeper attenuation curve than at z 4, and (ii) a rapidly decreasing dust obscured fraction of star formation as a function of redshift. Nevertheless, even among this UV-selected sample, massive galaxies (log M∗/M· > 10) at z ∼ 5 - 6 already exhibit an obscured fraction of star formation of ∼45%, indicating a rapid build-up of dust during the epoch of reionization.
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