Galaxy chemical evolution models: The role of molecular gas formation

Mollá, Mercedes; Díaz, Ángeles I.; Ascasibar, Yago; Gibson, Brad K.

Abstract

In our classical grid of multiphase chemical evolution models, star formation in the disc occurs in two steps: first, molecular gas forms, and then stars are created by cloud-cloud collisions or interactions of massive stars with the surrounding molecular clouds. The formation of both molecular clouds and stars are treated through the use of free parameters we refer to as efficiencies. In this work, we modify the formation of molecular clouds based on several new prescriptions existing in the literature, and we compare the results obtained for a chemical evolution model of theMilkyWay Galaxy regarding the evolution of the Solar region, the radial structure of the Galactic disc and the ratio between the diffuse and molecular components, H I /H 2 . Our results show that the six prescriptions we have tested reproduce fairly consistent most of the observed trends, differing mostly in their predictions for the (poorly constrained) outskirts of the Milky Way and the evolution in time of its radial structure. Among them, the model proposed by Ascasibar et al. (in preparation), where the conversion of diffuse gas into molecular clouds depends on the local stellar and gas densities as well as on the gas metallicity, seems to provide the best overall match to the observed data.

Citation

Mollá, M., Díaz, Á. I., Ascasibar, Y., & Gibson, B. K. (2017). Galaxy chemical evolution models: The role of molecular gas formation. Monthly notices of the Royal Astronomical Society, 468(1), 305-318. https://doi.org/10.1093/mnras/stx419

• Journal Article Type: Article
• Acceptance Date: Feb 15, 2017
• Online Publication Date: Feb 17, 2017
• Publication Date: Jun 11, 2017
• Deposit Date: Feb 27, 2017
• Publicly Available Date: Feb 27, 2017
• Journal: Monthly notices of the Royal Astronomical Society
• Print ISSN: 0035-8711
• Electronic ISSN: 1365-2966
• Publisher: Oxford University Press
• Peer Reviewed: Peer Reviewed
• Volume: 468
• Issue: 1
• Pages: 305-318
• DOI: https://doi.org/10.1093/mnras/stx419
• Keywords: Galaxy : abundances, Galaxy -- molecular gas, Galaxy -- star formation
• Public URL: https://hull-repository.worktribe.com/output/448950
• Publisher URL: https://academic.oup.com/mnras/article/3002593/Galaxy
• Additional Information: Copy of article first published in: Monthly notices of the Royal Astronomical Society, 2017, v.468.