Galaxy assembly, stellar feedback and metal enrichment: the view from the gaea model

Abstract

One major problem of current theoretical models of galaxy formation is given by their inability to reproduce the apparently 'anti-hierarchical' evolution of galaxy assembly: massive galaxies appear to be in place since z ∼ 3, while a significant increase of the number densities of low mass galaxies is measured with decreasing redshift. In this work, we perform a systematic analysis of the influence of different stellar feedback schemes, carried out in the framework of Gaea, a new semi-analytic model of galaxy formation. It includes a self-consistent treatment for the timings of gas, metal and energy recycling, and for the chemical yields. We show this to be crucial to use observational measurements of the metallicity as independent and powerful constraints for the adopted feedback schemes. The observed trends can be reproduced in the framework of either a strong ejective or preventive feedback model. In the former case, the gas ejection rate must decrease significantly with cosmic time (as suggested by parametrizations of the cosmological "FIRE" simulations). Irrespective of the feedback scheme used, our successful models always imply that up to 60-70 per cent of the baryons reside in an 'ejected' reservoir and are unavailable for cooling at high redshift. The same schemes predict physical properties of model galaxies (e.g. gas content, colour, age, and metallicity) that are in much better agreement with observational data than our fiducial model. The overall fraction of passive galaxies is found to be primarily determined by internal physical processes, with environment playing a secondary role.

The dust content of galaxies from z = 0 to z = 9

“…More accurately reproduced DTM ratios may therefore result in an even lower gas-phase metallicity. This emphasises the need for new or modified recipes that model the cycle of gas and metals in and out of galaxies (see for example Hirschmann, De Lucia & Fontanot 2016). These issues are likely also linked to other problems galaxy formation models face, such as producing too many low-mass galaxies at z > 0 and too-low specific star-formation rates and gas masses at z = 2 (Somerville & Davé 2015;Popping, Behroozi & Peeples 2015).…”

MultiDark-Galaxies: data release and first results

“…This has its origin not only in different calibration approaches (Knebe et al, in prep. ; see also Guo et al 2013;Gonzalez-Perez et al 2014;Guo et al 2016, where this has been partially addressed, too), but also in the model design and implementation of the actual physical phenomena (Hirschmann et al 2016). This certainly also applies to the three models presented here.…”

The VIMOS Public Extragalactic Redshift Survey (VIPERS)

“…However, the excess of low-mass passive galaxies might not just be a problem resulting from over-efficient hot-gas stripping when a galaxy becomes a satellite. For instance, Hirschmann et al (2016) show that this excess can be significantly reduced by modifying the stellar feedback scheme (i.e. in this case, the properties of galaxies change at the time they become satellites), and argue that the quenching timescales are not primarily determined by environmental processes.…”

“…Much effort has also been made to improve semi-analytical models of galaxy formation and evolution (see e.g. Guo et al 2011;De Lucia et al 2014;Henriques et al 2015;Hirschmann et al 2016). Although several works have studied the role of the environment in models of galaxy evolution (see e.g.…”