The SAMI galaxy survey:stellar population radial gradients in early-type galaxies
We study the internal radial gradients of the stellar populations in a sample comprising 522 early-type galaxies (ETGs) from the SAMI (Sydney-AAO Multi-object Integral field spectrograph) Galaxy Survey. We stack the spectra of individual spaxels in radial bins, and derive basic stellar population pr...
Published in: | Monthly Notices of the Royal Astronomical Society |
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Main Authors: | , , , , , , , , , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
2019
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Subjects: | |
Online Access: | https://researchers.mq.edu.au/en/publications/c1b9025f-f3b2-4c2f-873a-499400a2e290 https://doi.org/10.1093/mnras/stz2095 https://research-management.mq.edu.au/ws/files/117798944/117699477.pdf http://purl.org/au-research/grants/arc/FT140100255 http://www.scopus.com/inward/record.url?scp=85075234754&partnerID=8YFLogxK |
Summary: | We study the internal radial gradients of the stellar populations in a sample comprising 522 early-type galaxies (ETGs) from the SAMI (Sydney-AAO Multi-object Integral field spectrograph) Galaxy Survey. We stack the spectra of individual spaxels in radial bins, and derive basic stellar population properties: total metallicity ([Z/H]), [Mg/Fe], [C/Fe] and age. The radial gradient (∇) and central value of the fits (evaluated at R e /4) are compared against a set of six observables that may act as drivers of the trends. We find that velocity dispersion (σ) - or, equivalently gravitational potential - is the dominant driver of the chemical composition gradients. Surface mass density is also correlated with the trends, especially with stellar age. The decrease of ∇[Mg/Fe] with increasing σ is contrasted by a rather shallow dependence of ∇[Z/H] with σ (although this radial gradient is overall rather steep). This result, along with a shallow age slope at the massive end, imposes a substantial constraint on the progenitors of the populations that contribute to the formation of the outer envelopes of ETGs. The SAMI sample is split, by design, between `field' and cluster galaxies. Only weak environment-related differences are found, most notably a stronger dependence of central total metallicity ([Z/H] e4 ) with σ along with a marginal trend of ∇[Z/H] to steepen in cluster galaxies, a result that is not followed by [Mg/Fe]. The results presented here serve as stringent constraints on numerical models of the formation and evolution of ETGs. |
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