Connecting and dissecting galaxies' angular momenta and neutral gas in a hierarchical universe: cue Dark Sage. Issue 4 (1st October 2018)

• Record Type: Journal Article
• Authors: Stevens, Adam R H; Lagos, Claudia del P; Obreschkow, Danail; Sinha, Manodeep
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 481:Issue 4(2018)
• Page Start: 5543
• Page End: 5559
• Publication Date: 2018-10-01
• Subjects: galaxies: evolution -- galaxies: haloes -- galaxies: interactions -- galaxies: ISM -- galaxies: star formation; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty2650
• Languages: English
• ISSNs: 0035-8711

Abstract

Abstract: We explore the connection between the atomic gas fraction, f atm, and 'global disc stability' parameter, q, of galaxies within a fully cosmological context by examining galaxies in the Dark Sage semi-analytic model. The q parameter is determined by the ratio of disc specific angular momentum to mass, i.e. q ∝ j disc / m disc . Dark Sage is well suited to our study, as it includes the numerical evolution of one-dimensional disc structure, making both j disc and q predicted quantities. We show that Dark Sage produces a clear correlation between gas fraction and j disc at fixed disc mass, in line with recent results from observations and hydrodynamic simulations. This translates to a tight q – f atm sequence for star-forming central galaxies, which closely tracks the analytic prediction of Obreschkow et al. The scatter in this sequence is driven by the probability distribution function of mass as a function of j (PDF of j ) within discs, specifically where it peaks. We find that halo mass is primarily responsible for the peak location of the PDF of j, at least for low values of q . Two main mechanisms of equal significance are then identified for disconnecting f atm from q . Mergers in the model can trigger quasar winds, with the potential to blow out most of the gas disc, while leaving the stellar disc relatively unharmed. Ram-pressure stripping of satellite galaxies has a similar effect, where f atm can drop drastically with only a minimal effect to q . We highlight challenges associated with following these predictions up with observations.