Characterizing the Local Relation between Star Formation Rate and Gas-phase Metallicity in MaNGA Spiral Galaxies

Sánchez-Menguiano, Laura; Sánchez Almeida, Jorge; Muñoz-Tuñón, Casiana; Sánchez, Sebastián F.; Filho, Mercedes; Hwang, Hsiang-Chih; Drory, Niv
Bibliographical reference

The Astrophysical Journal, Volume 882, Issue 1, article id. 9, 17 pp. (2019).

Advertised on:
9
2019
Number of authors
7
IAC number of authors
3
Citations
42
Refereed citations
39
Description
The role of gas accretion in galaxy evolution is still a matter of debate. The presence of inflows of metal-poor gas that trigger star formation bursts of low metallicity has been proposed as an explanation for the local anticorrelation between star formation rate (SFR) and gas-phase metallicity (Z g ) found in the literature. In the present study, we show how the anticorrelation is also present as part of a diversified range of behaviors for a sample of more than 700 nearby spiral galaxies from the SDSS-IV MaNGA survey. We have characterized the local relation between SFR and Z g after subtracting the azimuthally averaged radial profiles of both quantities. Of the analyzed galaxies, 60% display an SFR–Z g anticorrelation, with the remaining 40% showing no correlation (19%) or positive correlation (21%). Applying a random forest machine-learning algorithm, we find that the slope of the correlation is mainly determined by the average gas-phase metallicity of the galaxy. Galaxy mass, g ‑ r colors, stellar age, and mass density seem to play a less significant role. This result is supported by the performed second-order polynomial regression analysis. Thus, the local SFR–Z g slope varies with the average metallicity, with the more metal-poor galaxies presenting the lowest slopes (i.e., the strongest SFR–Z g anticorrelations), and reversing the relation for more metal-rich systems. Our results suggest that external gas accretion fuels star formation in metal-poor galaxies, whereas in metal-rich systems, the gas comes from previous star formation episodes.
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