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Evolution of Elliptical Galaxies' Color-Magnitude Relation

Explore the color-magnitude relation of elliptical galaxies, studying scatter, spectroscopic data, and Sérsic profiles, with comparisons to truncation models. Results show long-term red sequence formation.

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Evolution of Elliptical Galaxies' Color-Magnitude Relation

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  1. The scatter and evolution of the color-magnitude relation of elliptical galaxies Christine Ruhland MPIA Students Workshop March 2007

  2. Introduction – Elliptical galaxies • Elliptical galaxies: • old stellar populations • no star formation • Tight relation in the CMD - red sequence Christine Ruhland - The color-magnitude relation

  3. Introduction - Truncation models formation redshift = 2 1.95 1.2 truncation redshifts 0.6 0.8 1.0 0.2 0.4 Christine Ruhland - The color-magnitude relation

  4. Introduction - Goals • Measurement of the scatter of the CMR (formation epoch) • 2 requirements: • Well-measured colors • Spectroscopic redshifts (good k-corrections) Christine Ruhland - The color-magnitude relation

  5. Spectroscopic redshift sample of 2138 objects three redshift bins used to make CMDs Data – GEMS and the spectroscopic redshifts 531 269 191 Christine Ruhland - The color-magnitude relation

  6. measurement of flux inside of the half light radius for the two GEMS filters v (606 nm) and z (920 nm) K-correction to get other filter bands Method Christine Ruhland - The color-magnitude relation

  7. Christine Ruhland - The color-magnitude relation

  8. Results – measurement of scatter and zeropoints in the CMD • u-g over Mg at z = 0.1 calculated with restframe grid • Additional SDSS data for z = 0.05 MIPS 24µm IR X-ray n > 2.5 AND red n < 2.5 blue Christine Ruhland - The color-magnitude relation

  9. Sérsic profile • Profile describing the surface brightness of galaxies • Sérsic index n • n ~ 1 for disks (exponetial profile) • The higher the steeper the inner part of the profile • n = 4 for bulges (deVaucouleurs profile) Christine Ruhland - The color-magnitude relation

  10. Results – measurement of scatter and zeropoints in the CMD • u-g over Mg at z = 0.1 calculated with restframe grid • Additional SDSS data for z = 0.05 • REAL error bars, i.e., we measure the scatter Christine Ruhland - The color-magnitude relation

  11. Comparison with truncation models Christine Ruhland - The color-magnitude relation

  12. Truncation models formation redshift = 2 1.95 1.2 truncation redshifts 0.6 0.8 1.0 0.2 0.4 Christine Ruhland - The color-magnitude relation

  13. More complex truncation models • Galaxies with different truncation redshifts and metallicities (distributed around solar metallicity) 583 34 24 93 Christine Ruhland - The color-magnitude relation

  14. Conclusion • Red sequence has build up over a longer period of time Christine Ruhland - The color-magnitude relation

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