The Messenger Astronomical Science
ALMA Constrains the Stellar Initial Mass Function of Dusty Starburst Galaxies
No. 172 (June 2018), 14–17
The stellar initial mass function (IMF) is fundamental to all measurements of cosmic star formation, which involves an extrapolation from rare, massive stars (M∗ > 8 M⊙) to the full stellar mass spectrum. Classical determinations of a galaxy’s IMF are limited to ultraviolet, optical and near-infrared wavelengths, and these cannot be adopted for dust- obscured galaxies with intense, ongoing star formation, even in the local Universe. The unprecedented sensi- tivity of the Atacama Large Millimeter/submillimeter Array (ALMA) allows us to detect weak emission from 13CO and C18O isotopologues, which offer a sensitive, relatively dust-free, probe of the IMF. Globally low 13CO/C18O ratios for all our targets — dusty starburst galaxies at redshifts ~ 2–3 — alongside a detailed chemical evolution model imply that stars formed in extreme starburst environments are significantly biased towards massive stars compared to ordinary star-forming spiral galaxies. We have combined information from the coldest interstellar medium (at tens of Kelvins) with the physics of nucleosynthesis in hot stars (at tens of millions of Kelvins), to delineate the formation and evolution of galaxies. This opens up a new window to probe the stellar IMF of galaxies with ALMA and it challenges our understanding of fundamental parameters governing galaxy formation and evolution, such as star formation rates, and the timescales for gas depletion and dust formation.
Cite this article:
Z. Zhang, D. Romano, R. Ivison, P. Papadopoulos, F. Matteucci; ALMA Constrains the Stellar Initial Mass Function of Dusty Starburst Galaxies. The Messenger 172 (June 2018): 14–17. https://doi.org/10.18727/0722-6691/5075