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The formation history of elliptical galaxies

The formation history of elliptical galaxies. Gabriella De Lucia, Volker Springel, Simon D. M. White, Darren Croton and Guinevere kauffmann. Libin Fan 1 st July 2014. Authors. Astronomical Observatory of Trieste. 的 里雅斯特天文台 （ 意大利东北部港市）. Galaxies through the cosmic ages

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The formation history of elliptical galaxies

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  1. The formation history of elliptical galaxies Gabriella De Lucia, Volker Springel, Simon D. M. White, Darren Croton and Guinevere kauffmann Libin Fan 1st July 2014

  2. Authors Astronomical Observatory of Trieste 的里雅斯特天文台 （意大利东北部港市） • Galaxies through the cosmic ages • The ESO Distance Cluster Survey • The VIMOS Public Extragalactic Survey • EUCLID Gabriella De Lucia

  3. Max-Planck-Institute for Astrophysics In the spring of 2010, I will move to a professorship in Theoretical Astrophysics at the University of Heidelberg(海德堡市) • Galaxy formation • Numerical Cosmology • Dark matter and dark energy • Large Projects • Millennium Simulation • Aquarius Project Volker Springel Director at the Max-Planck-Institute for Astrophysics • Galactic structure • Structure, formation and evolution of galaxies • Nature and distribution of dark matter • Planck at MPA • LOFAR(Low Frequency Array) at MPA Simon D. M. White

  4. Associate Professor and QEII Research Fellow Centre for Astrophysics & Supercomputing Swinburne University of Technology(斯文本科技大学) • Galaxy formation and evolution, quasars and AGN, cooling flows and "quenching" mechanisms. The red sequence and massive galaxy assembly. Cosmology, large-scale structure and voids, environmental effects. Darren Croton Guinevere Kauffmann http://gc2014.csp.escience.cn/dct/page/65580 中国学术会议在线 http://www.meeting.edu.cn/meeting/media/mediaAction!mediaList.action?id=38715

  5. Outline • The Millennium simulation used in the study • The semi-analytic model employed for our analysis • Star formation history of model elliptical galaxies depends on the stellar mass of galaxies and environment • The dependence of ages and metallicities on galaxy mass and environment • Summarize and discuss the finding

  6. Introduction Color-magnitude relation Fundamental scale relation Fundamental plane Monolithic scenario Hierarchical formation scenario Two problems α-element enhancement, [α/Fe] ratio dissimilar evolution of early-type galaxies in different environment Simulation(ΛCDM) + semi-analytic model This article concentrates on the analysis of the star formation histories, the ages, and the metallicities of model elliptical galaxies as a function of galaxy mass and of environment.

  7. The Millennium Simulation *from 2dFGRS and WMAP

  8. The Semi-analytic Model The key difference(De Lucia, 2004a) explicitly follow dark matter haloes even after they are accreted onto larger systems Star formation Bulge formation Take place during merger(De Lucia, 2004b) Mass ratio > 0.3, we witness a major merger Hierarchical merging trees(Springel, 2005) the descendant in the next time slice of each dark matter (sub)halo is identified as the (sub)halo that contains the largest number of its most tightly bound particles Grow from disk instabilities(Croton, 2005) May be more important for fainter ellipticals

  9. Δ M < 0.4 spiral ~lenticular Δ M > 1.56 irregular ΔM = Mbulge / (Mtotal - Mbulge) > 4 * 109MΘ 1030149 > 1 * 1010M Θ 810486 ‘ejection slow’ feedback model(De Lucia, 2004b) reproduce both the observed relation between stellar mass and cold phase metallicity, and the relation between luminosity and cold gas fraction for galaxies in the local universe Morphology of galaxies(Simien & de Vaucouleurs, 1986) B-band bulge-to-disk ratio together with the observational relation Central heating by AGN and suppression of cooling flows(Croton, 2005)

  10. The star formation history of elliptical galaxies In different bins of stellar mass Average star formation Stellar mass ~1012 Cluster elliptical Stellar mass ~1011 Stellar mass ~1010 Field elliptical Stellar mass ~109 • Result 1: more massive elliptical galaxies have star formation histories that peak at higher redshift(~5) than lower mass systems

  11. Star formation history of randomly selected elliptical galaxies • Bulge formation takes place during merger-induced bursts

  12. Star formation history in bins of different parent halo mass Halo mass ~ 1015 Halo mass ~ 1014 Halo mass ~ 1013 Halo mass ~ 1012 Stellar mass > 4*109 • Result 2: The faster evolution of proto-cluster regions produces star formation histories that peak at higher redshift for galaxies in more massive haloes.

  13. The distribution of ages and metallicity As a function of stellar mass and environment Define the formation redshift as the redshift when 50%(or 80%) of the stars that make up the final elliptical galaxies at redshift zero are already formed Formation redshift Stellar mass > 1011 Stellar mass > 4 * 109 • Result 3: Stars in more massive ellipticals are on average older than stars in their less massive counterparts

  14. Define the assembly time as the redshift when 50%(or 80%) of the final stellar mass is already contained in a single object Assembly redshift • Result 4: A significant fraction of present elliptical galaxies has assembled relatively recently through purely stellar mergers

  15. The age, the metallicity and the B-V color Depend on the galaxy stellar mass

  16. The age, the metallicity and the B-V color Depend on the virial mass of the halo

  17. Properties on cluster-centric distance Haloes M200 > 8 * 1014 Stellar mass > 4 * 109 51 • Result 5: Galaxies closer to the center are on average older and more metal rich than galaxies at the outskirts of these clusters

  18. Effective number of stellar progenitor Single object 0.5 M 0.5 M M Neff = 2 0.25 M 0.25 M 0.5 M Neff = 8/3 M

  19. Median of the distribution in default model galaxy Median of the distribution in a model where bulge formation through disk instability is switched off

  20. Conclusion 1. The dependence of the star formation histories, ages, and metallicities on environment and on galaxy stellar mass Elliptical galaxies in denser environments are on average older, more metal rich, and redder than the general population of ‘field’ ellipticals A clear trend for increasing ages and metallicities, and for redder colors, with decreasing cluster-centric distance 2. The properties of model elliptical galaxies change as a function of the stellar mass Most massive elliptical galaxies have the oldest and most metal rich stellar population Massive ellipticals are predicted to be assembled later than their lower mass counterparts, and that they have a larger effective number of progenitor systems

  21. The most massive ellipticals have the most extend star formation histories

  22. Default model Model without AGN feedback and without any cooling cutoff Model without AGN feedback but with a cooling cutoff

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