# GASP. XX. From the loose spatially-resolved to the tight global SFR-Mass relation in local spiral galaxies

## TL;DR

This study examines the spatially resolved star formation rate-mass relation in 30 local spiral galaxies, revealing significant galaxy-to-galaxy variation and the influence of galaxy size on the global relation.

## Contribution

It provides the first detailed analysis of the {\Sigma}SFR-{\Sigma}_star relation across galaxy outskirts up to >4 re, highlighting the role of local structures and galaxy size.

## Key findings

- The {\Sigma}SFR-{\Sigma}_star relation shows broad scatter and varies per galaxy.
- Bright off-center star-forming knots contribute to the scatter.
- The global SFR-M_star relation is driven by the size-mass relation.

## Abstract

Exploiting the sample of 30 local star-forming, undisturbed late-type galaxies in different environments drawn from the GAs Stripping Phenomena in galaxies with MUSE (GASP), we investigate the spatially resolved Star Formation Rate-Mass ({\Sigma}SFR-{\Sigma}_star) relation. Our analysis includes also the galaxy outskirts (up to >4 effective radii, re), a regime poorly explored by other Integral Field Spectrograph surveys. Our observational strategy allows us to detect H{\alpha} out to more than 2.7re for 75% of the sample. Considering all galaxies together, the correlation between the {\Sigma}SFR and {\Sigma}_star is quite broad, with a scatter of 0.3 dex. It gets steeper and shifts to higher {\Sigma}_star values when external spaxels are excluded and moving from less to more massive galaxies. The broadness of the overall relation suggests galaxy-by-galaxy variations. Indeed, each object is characterized by a distinct {\Sigma}SFR-{\Sigma}_star relation and in some cases the correlation is very loose. The scatter of the relation mainly arises from the existence of bright off-center star-forming knots whose {\Sigma}SFR-{\Sigma}_star relation is systematically broader than that of the diffuse component. The {\Sigma}SFR-{\Sigma}tot gas (total gas surface density) relation is as broad as the {\Sigma}SFR-{\Sigma}_star relation, indicating that the surface gas density is not a primary driver of the relation. Even though a large galaxy-by-galaxy variation exists, mean {\Sigma}SFR and {\Sigma}_star values vary of at most 0.7 dex across galaxies. We investigate the relationship between the local and global SFR-M_star relation, finding that the latter is driven by the existence of the size-mass relation.