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Accepted manuscript

Exploring the spatially resolved initial mass function in SAMI star-forming galaxies

Published online by Cambridge University Press:  04 February 2025

Diego Salvador Open the ORCID record for Diego Salvador [Opens in a new window] ,
Andrew M. Hopkins Open the ORCID record for Andrew M. Hopkins [Opens in a new window] ,
Matt Owers ,
Themiya Nanayakkara Open the ORCID record for Themiya Nanayakkara [Opens in a new window]  and
Scott M. Croom
Diego Salvador*
Affiliation:
School of Mathematical and Physical Sciences, 12 Wally’s Walk, Macquarie University, NSW 2109, Australia.
Andrew M. Hopkins
Affiliation:
School of Mathematical and Physical Sciences, 12 Wally’s Walk, Macquarie University, NSW 2109, Australia.
Matt Owers
Affiliation:
School of Mathematical and Physical Sciences, 12 Wally’s Walk, Macquarie University, NSW 2109, Australia. ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia.
Themiya Nanayakkara
Affiliation:
Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, 3122, VIC, Australia.
Scott M. Croom
Affiliation:
ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Australia. Sydney Institute for Astronomy, School of Physics, University of Sydney, NSW 2006, Australia.
*
Author for correspondence: D. Salvador, Email: [email protected].
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Abstract

The initial mass function (IMF) is a construct that describes the distribution of stellar masses for a newly formed population of stars. It is a fundamental element underlying all of star and galaxy formation, and has been the subject of extensive investigation for more than 60 years. In the past few decades there has been a growing, and now substantial, body of evidence supporting the need for a variable IMF. In this light, it is crucial to investigate the IMF’s characteristics across different spatial scales and to understand the factors driving its variability. We make use of spatially resolved spectroscopy to examine the high-mass IMF slope of star-forming galaxies within the SAMI survey. By applying the Kennicutt method and stellar population synthesis models, we estimated both the spaxel-resolved (αres) and galaxy-integrated (αint) high-mass IMF slopes of these galaxies. Our findings indicate that the resolved and integrated IMF slopes exhibit a near 1:1 relationship for αint ≳ –2.7. We observe a wide range of αres distributions within galaxies. To explore the sources of this variability, we analyse the relationships between the resolved and integrated IMF slopes and both the star formation rate (SFR) and SFR surface density (ΣSFR). Our results reveal a strong correlation where flatter/steeper slopes are associated with higher/lower SFR and ΣSFR. This trend is qualitatively similar for resolved and global scales. Additionally, we identify a mass dependency in the relationship with SFR, though none was found in the relation between the resolved slope and ΣSFR. These findings suggest an scenario where the formation of high-mass stars is favoured in regions with more concentrated star formation. This may be a consequence of the reduced fragmentation of molecular clouds, which nonetheless accrete more material.

Type
Research Article
Information
Publications of the Astronomical Society of Australia , Accepted manuscript , pp. 1 - 18
Copyright
© The Author(s), 2025. Published by Cambridge University Press on behalf of Astronomical Society of Australia

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