ALMA-LEGUS I: The Influence of Galaxy Morphology on Molecular Cloud Properties

• Main Authors: Finn, Molly K, Johnson, Kelsey E, Indebetouw, Remy, Costa, Allison H, Adamo, Angela, Aloisi, Alessandra, Bittle, Lauren, Calzetti, Daniela, Dale, Daniel A, Dobbs, Clare L, Meyer, Jennifer Donovan, Elmegreen, Bruce G, Elmegreen, Debra M, Fumagalli, Michele, Gallagher, J. S, Grasha, Kathryn, Grebel, Eva K, Kennicutt, Robert C, Krumholz, Mark R, Lee, Janice C, Messa, Matteo, Nair, Preethi, Sabbi, Elena, Smith, Linda J, Thilker, David A, Whitmore, Bradley C, Wofford, Aida
• Format: Journal Article
• Language: English
• Published: 02-01-2024
• Subjects: Physics - Astrophysics of Galaxies
• DOI: 10.48550/arxiv.2401.01450

We present a comparative study of the molecular gas in two galaxies from the
LEGUS sample: barred spiral NGC 1313 and flocculent spiral NGC 7793. These two
galaxies have similar masses, metallicities, and star formation rates, but NGC
1313 is forming significantly more massive star clusters than NGC 7793,
especially young massive clusters (<10 Myr, >10^4 Msol). Using ALMA CO(2-1)
observations of the two galaxies with the same sensitivities and resolutions of
13 pc, we directly compare the molecular gas in these two similar galaxies to
determine the physical conditions responsible for their large disparity in
cluster formation. By fitting size-linewidth relations for the clouds in each
galaxy, we find that NGC 1313 has a higher intercept than NGC 7793, implying
that its clouds have higher kinetic energies at a given size scale. NGC 1313
also has more clouds near virial equilibrium than NGC 7793, which may be
connected to its higher rate of massive cluster formation. However, these
virially bound clouds do not show a stronger correlation with young clusters
than that of the general cloud population. We find surprisingly small
differences between the distributions of molecular cloud populations in the two
galaxies, though the largest of those differences are that NGC 1313 has higher
surface densities and lower free-fall times.