Dust attenuation in 2 < z < 3 star-forming galaxies from deep ALMA observations of the Hubble Ultra Deep Field

作者：McLure R J; Dunlop J S; Cullen F; Bourne N; Best P N; Khochfar S; Bowler R A A; Biggs A D; Geach J E; Scott D; Michalowski M J; Rujopakarn W; van Kampen E; Kirkpatrick A; Pope A

来源：Monthly Notices of the Royal Astronomical Society, 2018, 476(3): 3991-4006.

DOI：10.1093/mnras/sty522

• galaxies: evolution
• galaxies: high-redshift
• galaxies: starburst
• galaxies: star formation
• submillimetre: galaxies

We present the results of a new study of the relationship between infrared excess (IRX equivalent to L-IR/L-UV), ultraviolet (UV) spectral slope (beta) and stellar mass at redshifts 2 < z < 3, based on a deep Atacama Large Millimeter Array (ALMA) 1.3-mm continuum mosaic of the Hubble Ultra Deep Field. Excluding the most heavily obscured sources, we use a stacking analysis to show that z similar or equal to 2.5 star-forming galaxies in the mass range 9.25 <= log(M-*/M-circle dot) <= 10.75 are fully consistent with the IRX-beta relation expected for a relatively grey attenuation curve, similar to the commonly adopted Calzetti law. Based on a large, mass-complete sample of 2 <= z <= 3 star-forming galaxies drawn from multiple surveys, we proceed to derive a new empirical relationship between beta and stellar mass, making it possible to predict UV attenuation (A(1600)) and IRX as a function of stellar mass, for any assumed attenuation law. Once again, we find that z <= 2.5 star-forming galaxies follow A(1600)-M-* and IRX-M-* relations consistent with a relatively grey attenuation law, and find no compelling evidence that star-forming galaxies at this epoch follow a reddening law as steep as the Small Magellanic Cloud (SMC) extinction curve. In fact, we use a simple simulation to demonstrate that previous determinations of the IRX-beta relation may have been biased towards low values of IRX at red values of beta, mimicking the signature expected for an SMC-like dust law. We show that this provides a plausible mechanism for reconciling apparently contradictory results in the literature and that, based on typical measurement uncertainties, stellar mass provides a cleaner prediction of UV attenuation than beta. Although the situation at lower stellar masses remains uncertain, we conclude that for 2 < z < 3 star-forming galaxies with log(M-*/M-circle dot) >= 9.75, both the IRX-beta and IRX-M-* relations are well described by a Calzetti-like attenuation law.

• 出版日期2018-5