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Chemical clocks for early-type galaxies in clusters

Chemical clocks for early-type galaxies in clusters Carretero, Vazdekis & Beckman. 2006, MNRAS, in press. Conrado Carretero Alejandro Vazdekis John E. Beckman. Framework: how were galaxies formed?. Our study:.

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Chemical clocks for early-type galaxies in clusters

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  1. Chemical clocks for early-type galaxies in clusters Carretero, Vazdekis & Beckman. 2006, MNRAS, in press Conrado Carretero Alejandro Vazdekis John E. Beckman

  2. Framework: how were galaxies formed?

  3. Our study: • Detailed stellar population (SP) analysis: offer a “fossil record” of galaxy formation and evolution processes. • Based on new stellar population models and a new methodology. • We concentrate on early-type galaxies since they represent most of the luminous mass of clusters. • SAMPLE: 27 massive (250 km/s < s < 450 km/s) elliptical galaxies distributed in 4 very rich clusters (richness class 3).

  4. Ages Information obtained from SP Abundances We use certain elements as “chemical clocks”:

  5. Ages Information obtained from SP Abundances • We use certain elements as “chemical clocks”: • Mg Produced by SNe II in ~0.01 Gyr(e.g. Faber, Worthey & González 1992) • CN By intermediate-mass stars in ~0.5 Gyr (e.g. Chiappini et al. 2003) • Fe Produced, mainly, by SNe Ia in ~1 Gyr(e.g. Hughes et al. 1992) • Others…

  6. C, CN Fe Mg SFR 1 Gyr 0.01 Gyr 0.5 Gyr TODAY time Ages Information obtained from SP Abundances We use certain elements as “chemical clocks”: SP formation timescales SHORT LONG

  7. The values of the abundance ratios of those elements, measured in a galaxy, are related with the formation timescale of its stellar population. Do they depend on the environment? Ages Information obtained from SP Abundances • We use certain elements as “chemical clocks”: • Mg Produced by SNe II in ~0.01 Gyr (e.g. Faber, Worthey & González 1992) • CN By intermediate-mass stars in ~0.5 Gyr (e.g. Chiappini et al. 2003) • Fe Produced, mainly, by SNe Ia in ~1 Gyr(e.g. Hughes et al. 1992) • Others…

  8. Age Age Age Z Z Z Ages Information obtained from SP Abundances

  9. Results

  10. Our sample Coma* Virgo* * Taken from Sánchez-Blázquez et al. (2006) Results

  11. [CN/Fe] gradient with cluster mass Results [Mg/Fe] provides an upper limit for SP formation timescales (~1 Gyr) while [CN/Fe] is most suitable to discriminate between different timescales (linked to the environment) but…

  12. Results [Mg/Fe] provides an upper limit for SP formation timescales (~1 Gyr) while [CN/Fe] is most suitable to discriminate between different timescales (linked to the environment) but… … only for those galaxies with s < 300 km/s

  13. Conclusions • [CN/Fe] and [Mg/Fe] appear to be the key “chemical clocks” for infering the star formation history timescales in ellipticals. • [Mg/Fe] provides an upper limit for those formation timescales, while [CN/Fe] discriminates more finely among them. • We estimate an upper limit of <1 Gyr for those formation timescales, independently of their environment and galaxy mass. • Star formation history timescales in ellipticals depend on the environment: shorter timescales in denser environments. These differences become smaller as the galaxy mass increases.

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