TY - JOUR
T1 - Do spiral arms enhance star formation efficiency?
AU - Querejeta, Miguel
AU - Leroy, Adam K.
AU - Meidt, Sharon E.
AU - Schinnerer, Eva
AU - Belfiore, Francesco
AU - Emsellem, Eric
AU - Klessen, Ralf S.
AU - Sun, Jiayi
AU - Sormani, Mattia
AU - Bešlić, Ivana
AU - Cao, Yixian
AU - Chevance, Mélanie
AU - Colombo, Dario
AU - Dale, Daniel A.
AU - García-Burillo, Santiago
AU - Glover, Simon C.O.
AU - Grasha, Kathryn
AU - Groves, Brent
AU - Koch, Eric W.
AU - Neumann, Lukas
AU - Pan, Hsi An
AU - Pessa, Ismael
AU - Pety, Jérôme
AU - Pinna, Francesca
AU - Ramambason, Lise
AU - Razza, Alessandro
AU - Romanelli, Andrea
AU - Rosolowsky, Erik
AU - Ruiz-García, Marina
AU - Sánchez-Blázquez, Patricia
AU - Smith, Rowan
AU - Stuber, Sophia
AU - Ubeda, Leonardo
AU - Usero, Antonio
AU - Williams, Thomas G.
N1 - Publisher Copyright:
© 2024 The Authors.
PY - 2024/7
Y1 - 2024/7
N2 - Spiral arms, as those of our own Milky Way, are some of the most spectacular features in disc galaxies. 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 (Σ∗) is very modest, typically a few tens of percent. This is much smaller than the contrasts measured for molecular gas (Σmol) or star formation rate (ΣSFR) surface density, which typically reach a factor of ∼2 - 3. However, Σmol and ΣSFR contrasts show a significant correlation with the enhancement in Σ∗, 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 (Σ∗ contrast > 1.97). The molecular-to-atomic gas ratio (Σmol/Σatom) is higher in spiral arms, pointing to a transformation of atomic to molecular gas. As a consequence, the total gas contrast (Σmol + Σatom) slightly drops compared to Σmol (median 4% lower, working at ∼kpc resolution), while the SFE contrast increases when we include atomic gas (median 8% higher than for Σmol). The contrasts show important fluctuations with galactocentric radius. We confirm that our results are robust against a number of effects, such as spiral mask width, tracers, resolution, and binning. In conclusion, the boost in the SFE of molecular gas in spiral arms is generally modest or absent, except for locations with exceptionally large stellar contrasts.
AB - Spiral arms, as those of our own Milky Way, are some of the most spectacular features in disc galaxies. 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 (Σ∗) is very modest, typically a few tens of percent. This is much smaller than the contrasts measured for molecular gas (Σmol) or star formation rate (ΣSFR) surface density, which typically reach a factor of ∼2 - 3. However, Σmol and ΣSFR contrasts show a significant correlation with the enhancement in Σ∗, 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 (Σ∗ contrast > 1.97). The molecular-to-atomic gas ratio (Σmol/Σatom) is higher in spiral arms, pointing to a transformation of atomic to molecular gas. As a consequence, the total gas contrast (Σmol + Σatom) slightly drops compared to Σmol (median 4% lower, working at ∼kpc resolution), while the SFE contrast increases when we include atomic gas (median 8% higher than for Σmol). The contrasts show important fluctuations with galactocentric radius. We confirm that our results are robust against a number of effects, such as spiral mask width, tracers, resolution, and binning. In conclusion, the boost in the SFE of molecular gas in spiral arms is generally modest or absent, except for locations with exceptionally large stellar contrasts.
KW - Galaxies: spiral
KW - Galaxies: star formation
KW - Galaxies: structure
UR - http://www.scopus.com/inward/record.url?scp=85199498536&partnerID=8YFLogxK
U2 - 10.1051/0004-6361/202449733
DO - 10.1051/0004-6361/202449733
M3 - Article
AN - SCOPUS:85199498536
SN - 0004-6361
VL - 687
JO - Astronomy and Astrophysics
JF - Astronomy and Astrophysics
M1 - A293
ER -