A multiscale study of star formation in Messier 33. Issue 1 (15th November 2018)

• Record Type: Journal Article
• Authors: Elson, E C; Kam, S Z; Chemin, L; Carignan, C; Jarrett, T H
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 483:Issue 1(2019)
• Page Start: 931
• Page End: 946
• Publication Date: 2018-11-15
• Subjects: galaxies: evolution -- galaxies: ISM -- galaxies: kinematics and dynamics; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty3091
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: For the Local Group Scd galaxy M 33 this paper presents a multiscale study of the relationship between the monochromatic star formation rate (SFR) estimator based on 12 $\mu$ m emission and the total SFR estimator based on a combination of far-ultraviolet and 24 $\mu$ m emission. We show the 12 $\mu$ m emission to be a linear estimator of total SFR on spatial scales from 782 pc down to 49 pc, over almost four magnitudes in SFR. These results therefore extend to sub-kpc length-scales the analogous results from other studies for global length-scales. We use high-resolution H i and 12 CO( J = 2 − 1) image sets from the literature to compare the star formation to the neutral gas. For the full range of length-scales we find well-defined power-law relationships between 12 $\mu$ m-derived SFR surface densities and neutral gas surface densities. For the H2 gas component almost all correlations are consistent with being linear. No evidence is found for a breakdown in the star formation law at small length-scales in M 33 reported by other authors. We show that the average star formation efficiency in M 33 is roughly 10 −9 yr −1 and that it remains constant down to giant molecular cloud length-scales. Toomre and shear-based models of the star formation threshold are shown to inaccurately account for the star formation activity in the inner disc of M 33. Finally, we clearly show that the H i saturation limit of ≈9 M$_{\odot }\, \mathrm{pc}^{-2}$ reported in the literature for other galaxies is not an intrinsic property of M 33 – it is systematically introduced as an artefact of spatially smoothing the data.