SDSS-IV MaNGA: the [α/Fe] of early-type galaxies
ABSTRACT The mean stellar alpha-to-iron abundance ratio ([α/Fe]) of a galaxy is an indicator of galactic star formation time-scale. It is important for understanding the star formation history of early-type galaxies (ETGs) as their star formation processes have basically stopped. Using the model tem...
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| Published in: | Monthly notices of the Royal Astronomical Society 2020-09, Vol.497 (3), p.3011-3025 |
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| Main Author: | |
| Format: | Article |
| Language: | eng |
| Online Access: | Get full text |
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| Summary: | ABSTRACT
The mean stellar alpha-to-iron abundance ratio ([α/Fe]) of a galaxy is an indicator of galactic star formation time-scale. It is important for understanding the star formation history of early-type galaxies (ETGs) as their star formation processes have basically stopped. Using the model templates that are made by Vazdekis et al., we apply the pPXF-based spectral fitting method to estimate the [α/Fe] of 196 high-signal-to-noise ratio ETGs from the Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey. The velocity dispersions within 1Re (σe) range from 27 to 270 km s−1. We find a flat relation between the mean [α/Fe] within the 1$R_\mathrm{ e}^{\mathrm{ maj}}$ ellipses and log(σe), even if limiting to the massive sample with log(σe/km s−1) > 1.9. However, the relation becomes positive after we exclude the Mg1 feature in our fits, which agrees with the results from the previous work with other stellar population models, albeit with relatively large scatter. It indicates that the Vazdekis models have self-inconsistency and do not actually cover the observations in Mg1. For reference, we also measure the stellar population radial gradients within 1$R_\mathrm{ e}^{\mathrm{ maj}}$ ellipses. Due to the low resolution of age estimations for old objects and the Mg1 issue, the uncertainties of these gradients cannot be neglected. |
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| ISSN: | 0035-8711 1365-2966 |