%0 Generic %1 segers2016origin %A Segers, Marijke C. %A Schaye, Joop %A Bower, Richard G. %A Crain, Robert A. %A Schaller, Matthieu %A Theuns, Tom %D 2016 %K early evolutions metallicity type %T The origin of the $\alpha$-enhancement of massive galaxies %U http://arxiv.org/abs/1603.05653 %X We study the origin of the stellar $\alpha$-element-to-iron abundance ratio, $\alpha/Fe_\ast$, of present-day central galaxies, using cosmological, hydrodynamical simulations from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) project. For galaxies with stellar masses of $M_\ast > 10^10.5$ M$_ødot$, $\alpha/Fe_\ast$ increases with increasing galaxy stellar mass and age. These trends are in good agreement with observations of early-type galaxies, and are consistent with a `downsizing' galaxy formation scenario: more massive galaxies have formed the bulk of their stars earlier and more rapidly, hence from an interstellar medium (ISM) that was mostly $\alpha$-enriched by massive stars. In the absence of feedback from active galactic nuclei (AGN), however, $\alpha/Fe_\ast$ in $M_\ast > 10^10.5$ M$_ødot$ galaxies is roughly constant with stellar mass and decreases with mean stellar age, extending the trends found for lower-mass galaxies in both simulations with and without AGN. We conclude that AGN feedback can account for the $\alpha$-enhancement of massive galaxies, as it suppresses their star formation, quenching more massive galaxies at earlier times, thereby preventing the iron from longer-lived intermediate-mass stars (supernova Type Ia) from being incorporated into younger stars.

@misc{segers2016origin, abstract = {We study the origin of the stellar $\alpha$-element-to-iron abundance ratio, $[\alpha/\mathrm{Fe}]_{\ast}$, of present-day central galaxies, using cosmological, hydrodynamical simulations from the Evolution and Assembly of GaLaxies and their Environments (EAGLE) project. For galaxies with stellar masses of $M_{\ast} > 10^{10.5}$ M$_{\odot}$, $[\alpha/\mathrm{Fe}]_{\ast}$ increases with increasing galaxy stellar mass and age. These trends are in good agreement with observations of early-type galaxies, and are consistent with a `downsizing' galaxy formation scenario: more massive galaxies have formed the bulk of their stars earlier and more rapidly, hence from an interstellar medium (ISM) that was mostly $\alpha$-enriched by massive stars. In the absence of feedback from active galactic nuclei (AGN), however, $[\alpha/\mathrm{Fe}]_{\ast}$ in $M_{\ast} > 10^{10.5}$ M$_{\odot}$ galaxies is roughly constant with stellar mass and decreases with mean stellar age, extending the trends found for lower-mass galaxies in both simulations with and without AGN. We conclude that AGN feedback can account for the $\alpha$-enhancement of massive galaxies, as it suppresses their star formation, quenching more massive galaxies at earlier times, thereby preventing the iron from longer-lived intermediate-mass stars (supernova Type Ia) from being incorporated into younger stars.}, added-at = {2016-03-21T09:37:33.000+0100}, author = {Segers, Marijke C. and Schaye, Joop and Bower, Richard G. and Crain, Robert A. and Schaller, Matthieu and Theuns, Tom}, biburl = {https://www.bibsonomy.org/bibtex/2e8f128b37d113b6a36fbdc0d3d5e9957/miki}, description = {[1603.05653] The origin of the $\alpha$-enhancement of massive galaxies}, interhash = {61b6d11bdb2f0fce792621ee89d4c1ad}, intrahash = {e8f128b37d113b6a36fbdc0d3d5e9957}, keywords = {early evolutions metallicity type}, note = {cite arxiv:1603.05653Comment: 5 pages, 3 figures, submitted to MNRAS Letters}, timestamp = {2016-03-21T09:37:33.000+0100}, title = {The origin of the $\alpha$-enhancement of massive galaxies}, url = {http://arxiv.org/abs/1603.05653}, year = 2016 }