Dusting the Universe - New Insight on Dust Formation from Ultra-luminous Infrared Galaxies at Cosmic Noon and Beyond

Chian-Chou Chen (TC)^1*

¹Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan

* Presenter:Chian-Chou Chen (TC), email:ccchen@asiaa.sinica.edu.tw

The majority of stellar masses in galaxies were assembled in dust obscured regions. Thanks to JWST and ALMA, significant amount of dust has now been found in galaxies all the way to the epoch of reionization, only a few hundred millions years after the Big Bang. Dust formation and evolution is therefore a key topic in modern galaxy formation theory, and key measurements such as dust emissivity index are critical. To put observational constraints on dust properties in galaxies, we model the spectral energy distributions of a statistical sample of 18 ultra-luminous infrared galaxies selected at submillimeter that are located at cosmic noon and beyond (z=2-5), where spectroscopic redshifts and multi-band FIR and (sub-)millimeter photometric data are available. We determine a median dust emissivity index of β = 2.1 ± 0.1 for our sample, and by combining our results with those from other DSFG samples, we find no correlation of β with redshift or infrared luminosity, indicating similar dust grain compositions across cosmic time for infrared luminous galaxies. In addition, based on the observed typical dust mass density in SMGs, we show that in order to maintain the observed β=2, dust in these galaxies must not grow via coagulation in an unlimited way; some other physical processes such as dust shattering should have an effect to strop further growth beyond μm size.

Keywords: Galaxy formation, Interstellar median, High-redshift galaxies, Infrared luminous galaxies, Dust