Detalles de publicación
PP 024049
Do spiral arms enhance star formation efficiency?
(1) Observatorio Astronómico Nacional (IGN),
(2) Department of Astronomy, The Ohio State University,
(3) Sterrenkundig Observatorium, Universiteit Gent,
(4) Max-Planck-Institut für Astronomie,
(5) INAF – Osservatorio Astrofisico di Arcetri,
(6) European Southern Observatory,
(7) Univ Lyon, Univ Lyon 1, ENS de Lyon, CNRS, Centre de Recherche
Astrophysique de Lyon UMR5574,
(8) Universität Heidelberg, Zentrum für Astronomie, Institut für The-
oretische Astrophysik,
(9) Universität Heidelberg, Interdisziplinäres Zentrum für Wis-
senschaftliches Rechnen,
(10) Department of Astrophysical Sciences, Princeton University,
(11) Università dell’Insubria,
(12) Department of Physics, University of Surrey,
(13) Sorbonne Université, Observatoire de Paris, Université PSL, CNRS,
LERMA,
(14) Max-Planck-Institut für extraterrestrische Physik,
(15) Cosmic Origins Of Life (COOL) Research DAO, coolresearch.io
(16) Argelander-Institut für Astronomie,
(17) Department of Physics and Astronomy, University of Wyoming,
(18) Research School of Astronomy and Astrophysics, Australian Na-
tional University,
(19) International Centre for Radio Astronomy Research, University of
Western Australia,
(20) Harvard-Smithsonian Center for Astrophysics,
(21) Department of Physics, Tamkang University,
(22) Leibniz-Institut for Astrophysik Potsdam (AIP),
(23) Institut de Radioastronomie Millimétrique (IRAM),
(24) Instituto de Astrofísica de Canarias,
(25) Departamento de Astrofísica, Universidad de La Laguna,
(26) Departamento de Astronomía, Universidad de Chile,
(27) Department of Physics, University of Alberta,
(28) Departamento de Física de la Tierra y Astrofísica, Universidad
Complutense de Madrid,
(29) School of Physics and Astronomy, University of St Andrews,
(30) Space Telescope Science Institute,
(31) Sub-department of Astrophysics, Department of Physics, University
of Oxford,
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.