Oral Presentation

Cold Dust and Low [OIII]/[CII] Ratios: an Evolved Star-forming Population at Redshift 7

Author(s): Hiddo Algera (Hiroshima University/NAOJ)

Presenter: Hiddo Algera (Hiroshima University)

ALMA has revolutionized our understanding of early galaxy evolution through the detection of dust and fine structure lines, such as [CII]158um or [OIII]88um, in galaxies well into the epoch of reionization. However, moving beyond single-band ALMA observations is essential for a detailed characterization of the earliest-known dusty galaxies: multi-band dust continuum measurements provide information on the shape of the infrared SED and hence the obscured star formation rate, while observations of multiple emission lines reveal the physical conditions of the ISM. In this talk, I will present recent ALMA Band 8 observations of three sources originally targeted in Band 6 as part of the REBELS ALMA Large Program, which reveal a peculiar population of distant galaxies with surprisingly cold dust temperatures and low [OIII]/[CII] line ratios. I will outline how, contrary to the z~7 population known thus far, these galaxies appear to be relatively evolved, star-forming sources characterized by massive dust reservoirs and low levels of bursty star formation. In addition, I will discuss this interesting sample in the context of possible redshift-evolution of galaxy dust temperatures, and in terms of dust production mechanisms in the early Universe.