Oral Presentation
Colder and Dustier! Probing Dust Properties of the Brightest Submillimeter Galaxies at Cosmic Noon
Presenter: Cheng-Lin Liao (NTU/ASIAA)
Dusty star-forming galaxies, luminous in the infrared and often times called submillimeter galaxies (SMGs), are dust-rich galaxies at cosmic noon (z~1-3) with star-formation rates more than one hundred times that of the Milky Way. The far-infrared (λ>100 μm) part of the spectral energy distribution (SED) of these galaxies can be well modeled by a single temperature modified blackbody profile, where the slope in Rayleigh-Jeans tail, characterized as the dust emissivity index (β), can help reveal dust grain properties.
In this talk, I would like to share our findings about the dust properties of a sample of flux-limited (S_850μm>12.4 mJy) SMGs, which is the largest complete sample of bright SMGs with ALMA CO survey. They have a higher dust fraction (M_dust/M_*) due to the selection effect, with an average L_IR~10^13 L_sun located at high redshift (z~2-5). Our SMGs are well sampled in far-infrared SED by the Terahertz data from Herschel as well as the millimeter data from ALMA. In addition, spectroscopic redshifts have been measured by the ALMA blind CO survey in >90% of the sample, which allows us to break the degeneracy between dust temperature (T_dust) and redshift.
In this study, we investigated how the dust properties of these ALMA-selected brightest SMGs differ from the typical SMGs. Are there any significant features of this sample that make it so massive in dust? To answer the question, we fit the far-infrared and millimeter photometry with the modified blackbody model. Results show that, compared to the typical SMGs, our sample appears to have a lower T_dust at a fixed luminosity due to the high 850 μm cut of the sample selection. However, β is broadly consistent to that of the typical SMGs, with a median β=2.1±0.1, inferring no significant difference in dust grain compositions between the brightest SMGs and the typical SMGs. Furthermore, together with the measurements of the local star-forming galaxies (z<0.5), we find a weak evolution of β, suggesting that our very bright SMGs are extremely dust-rich but have similar dust grain properties compared to those of typical star-forming galaxies from local to high redshift.
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