SIMBAD references

In this work, we analyse the connection between gas availability and the position of a region with respect to the spatially resolved main-sequence (MS) relation. Following the procedure presented in Enia et al. (2020), for a sample of five face-on, grand design spiral galaxies located on the MS we obtain estimates of stellar mass and star formation rate surface densities (Σ_* and Σ_SFR) within cells of 500 pc size. Thanks to H I 21cm and ¹²CO(2-1) maps of comparable resolution, within the same cells we estimate the surface densities of the atomic (Σ_H I_) and molecular (Σ_ H₂) gas and explore the correlations among all these quantities. Σ_*, Σ_SFR, and Σ_ H₂ define a 3D relation whose projections are the spatially resolved MS, the Kennicutt-Schmidt law and the molecular gas MS. We find that Σ_ H₂ steadily increases along the MS relation and is almost constant perpendicular to it. Σ_H I_ is nearly constant along the MS and increases in its upper envelope. As a result, Σ_SFR can be expressed as a function of Σ_* and Σ_H I_, following the relation log Σ_SFR = 0.97log Σ_* + 1.99log Σ_H I_ - 11.11. We show that the total gas fraction significantly increases towards the starburst regions, accompanied by a weak increase in star formation efficiency. Finally, we find that H₂/H I varies strongly with the distance from the MS, dropping dramatically in regions of intense star formation, where the UV radiation from newly formed stars dissociates the H₂ molecule, illustrating the self-regulating nature of the star formation process.