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Do spiral arms enhance star formation efficiency?

Authors :
Querejeta, Miguel
Leroy, Adam K.
Meidt, Sharon E.
Schinnerer, Eva
Belfiore, Francesco
Emsellem, Eric
Klessen, Ralf S.
Sun, Jiayi
Sormani, Mattia
Bešlic, Ivana
Cao, Yixian
Chevance, Mélanie
Colombo, Dario
Dale, Daniel A.
García-Burillo, Santiago
Glover, Simon C. O.
Grasha, Kathryn
Groves, Brent
Koch, Eric. W.
Neumann, Lukas
Pan, Hsi-An
Pessa, Ismael
Pety, Jérôme
Pinna, Francesca
Ramambason, Lise
Razza, Alessandro
Romanelli, Andrea
Rosolowsky, Erik
Ruiz-García, Marina
Sánchez-Blázquez, Patricia
Smith, Rowan
Stuber, Sophia
Ubeda, Leonardo
Usero, Antonio
Williams, Thomas G.
Publication Year :
2024

Abstract

Spiral arms are some of the most spectacular features in disc galaxies, and also present in our own Milky Way. It has been argued that star formation should proceed more efficiently in spiral arms as a result of gas compression. Yet, observational studies have so far yielded contradictory results. Here we examine arm/interarm surface density contrasts at ~100 pc resolution in 28 spiral galaxies from the PHANGS survey. We find that the arm/interarm contrast in stellar mass surface density (Sigma_*) is very modest, typically a few tens of percent. This is much smaller than the contrasts measured for molecular gas (Sigma_mol) or star formation rate (Sigma_SFR) surface density, which typically reach a factor of ~2-3. Yet, Sigma_mol and Sigma_SFR contrasts show a significant correlation with the enhancement in Sigma_*, suggesting that the small stellar contrast largely dictates the stronger accumulation of gas and star formation. All these contrasts increase for grand-design spirals compared to multi-armed and flocculent systems (and for galaxies with high stellar mass). The median star formation efficiency (SFE) of the molecular gas is 16% higher in spiral arms than in interarm regions, with a large scatter, and the contrast increases significantly (median SFE contrast 2.34) for regions of particularly enhanced stellar contrast (Sigma_* contrast >1.97). The molecular-to-atomic gas ratio (Sigma_mol/Sigma_atom) is higher in spiral arms, pointing to a transformation of atomic to molecular gas. In conclusion, the boost in the star formation efficiency of molecular gas in spiral arms is generally modest or absent, except for locations with exceptionally large stellar contrasts. (abridged)<br />Comment: 26 pages, 16 figures. Accepted for publication in A&A

Details

Database :
arXiv
Publication Type :
Report
Accession number :
edsarx.2405.05364
Document Type :
Working Paper