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arXiv · 2306.16441

The IR Compactness of Dusty Galaxies Set Star-formation and Dust Properties at z~0-2

Jed McKinney·Alexandra Pope·Allison Kirkpatrick·Lee Armus·Tanio Diaz-Santos·Carlos Gomez-Guijarro·Maximilien Franco·David Elbaz·Christopher C. Hayward·Hanae Inami·Gergo Popping·Mengyuan Xiao
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Abstract

Surface densities of gas, dust and stars provide a window into the physics of star-formation that, until the advent of high-resolution far-infrared/sub-millimeter observations, has been historically difficult to assess amongst dusty galaxies. To study the link between infrared (IR) surface densities and dust properties, we leverage the Atacama Large Millimetre/Submillimetre Array (ALMA) archive to measure the extent of cold dust emission in 15 $z\sim2$ IR selected galaxies selected on the basis of having available mid-IR spectroscopy from Spitzer. We use the mid-IR spectra to constrain the relative balance between dust heating from star-formation and active galactic nuclei (AGN), and to measure emission from Polycylic Aromatic Hydrocarbons (PAHs) -- small dust grains that play a key role in the photoelectric heating of gas. In general, we find that dust-obscured star-formation at high IR surface densities exhibits similar properties at low- and high-redshift, namely: local luminous IR galaxies have comparable PAH luminosity to total dust mass ratios as high-$z$ galaxies, and star-formation at $z\sim0-2$ is more efficient at high IR surface densities despite the fact that our sample of high$-z$ galaxies are closer to the main-sequence than local luminous IR galaxies. High star-formation efficiencies are coincident with a decline in the PAH/IR luminosity ratio reminiscent of the deficit observed in far-infrared fine-structure lines. Changes in the gas and dust conditions arising from high star-formation surface densities might help drive the star-formation efficiency up. This could help explain high efficiencies needed to reconcile star-formation and gas volume densities in dusty galaxies at cosmic noon.

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Jed McKinney, Alexandra Pope, Allison Kirkpatrick, Lee Armus, Tanio Diaz-Santos, Carlos Gomez-Guijarro, Maximilien Franco, David Elbaz, Christopher C. Hayward, Hanae Inami, Gergo Popping, Mengyuan Xiao. 2023-06-28. The IR Compactness of Dusty Galaxies Set Star-formation and Dust Properties at z~0-2. https://arxiv.org/abs/2306.16441

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