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| Main Authors: | , , , , , |
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| Format: | Preprint |
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2024
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| Online Access: | https://arxiv.org/abs/2407.07971 |
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| _version_ | 1866910522680541184 |
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| author | Gountanis, Nicole Marcelina Weinberg, David H. Beverage, Aliza G. Sandford, Nathan R. Conroy, Charlie Kriek, Mariska |
| author_facet | Gountanis, Nicole Marcelina Weinberg, David H. Beverage, Aliza G. Sandford, Nathan R. Conroy, Charlie Kriek, Mariska |
| contents | Spectroscopic studies of elliptical galaxies show that their stellar population ages, mean metallicity, and $α$-enhancement traced by [Mg/Fe] all increase with galaxy stellar mass or velocity dispersion. We use one-zone galactic chemical evolution (GCE) models with a flexible star formation history (SFH) to model the age, [Mg/H], and [Mg/Fe] inferred from simple stellar population (SSP) fits to observed ellipticals at $z \sim 0$ and $z \sim 0.7$. We show that an SSP fit to the spectrum computed from a full GCE model gives ages and abundances close to the light-weighted, logarithmically averaged values of the composite stellar population, <age>, <[Mg/H]>, and <[Mg/Fe]>. With supernova Mg and Fe yields fixed to values motivated by Milky Way stellar populations, we find that predicted <[Mg/H]>-<age> and <[Mg/Fe]>-<age> relations are surprisingly insensitive to SFH parameters: older galaxies have higher <[Mg/Fe]>, but the detailed form of the SFH has limited impact. The star formation efficiency and outflow efficiency affect the early and late evolution of <[Mg/H]>, respectively; explaining observed trends requires higher star formation efficiency and lower outflows in more massive galaxies. With core collapse supernova yields calibrated to the plateau [Mg/Fe]$_{\rm cc} \approx0.45$ observed in many Milky Way studies, our models underpredict the observed <[Mg/Fe]> ratios of ellipticals by 0.05-0.1 dex. Increasing the core collapse yield ratio to [Mg/Fe]$_{\rm cc} = 0.55$ improves the agreement, though the models still lie below the data. We discuss potential resolutions of this discrepancy, including the possibility that many ellipticals terminate their star formation with a self-enriching, terminating burst that reduces the light-weighted age and boosts <[Mg/Fe]>. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2407_07971 |
| institution | arXiv |
| publishDate | 2024 |
| record_format | arxiv |
| spellingShingle | Modeling the Ages and Chemical Abundances of Elliptical Galaxies Gountanis, Nicole Marcelina Weinberg, David H. Beverage, Aliza G. Sandford, Nathan R. Conroy, Charlie Kriek, Mariska Astrophysics of Galaxies Spectroscopic studies of elliptical galaxies show that their stellar population ages, mean metallicity, and $α$-enhancement traced by [Mg/Fe] all increase with galaxy stellar mass or velocity dispersion. We use one-zone galactic chemical evolution (GCE) models with a flexible star formation history (SFH) to model the age, [Mg/H], and [Mg/Fe] inferred from simple stellar population (SSP) fits to observed ellipticals at $z \sim 0$ and $z \sim 0.7$. We show that an SSP fit to the spectrum computed from a full GCE model gives ages and abundances close to the light-weighted, logarithmically averaged values of the composite stellar population, <age>, <[Mg/H]>, and <[Mg/Fe]>. With supernova Mg and Fe yields fixed to values motivated by Milky Way stellar populations, we find that predicted <[Mg/H]>-<age> and <[Mg/Fe]>-<age> relations are surprisingly insensitive to SFH parameters: older galaxies have higher <[Mg/Fe]>, but the detailed form of the SFH has limited impact. The star formation efficiency and outflow efficiency affect the early and late evolution of <[Mg/H]>, respectively; explaining observed trends requires higher star formation efficiency and lower outflows in more massive galaxies. With core collapse supernova yields calibrated to the plateau [Mg/Fe]$_{\rm cc} \approx0.45$ observed in many Milky Way studies, our models underpredict the observed <[Mg/Fe]> ratios of ellipticals by 0.05-0.1 dex. Increasing the core collapse yield ratio to [Mg/Fe]$_{\rm cc} = 0.55$ improves the agreement, though the models still lie below the data. We discuss potential resolutions of this discrepancy, including the possibility that many ellipticals terminate their star formation with a self-enriching, terminating burst that reduces the light-weighted age and boosts <[Mg/Fe]>. |
| title | Modeling the Ages and Chemical Abundances of Elliptical Galaxies |
| topic | Astrophysics of Galaxies |
| url | https://arxiv.org/abs/2407.07971 |