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

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

3. Christine Ruhland - The color-magnitude relation 0.2 1.2 0.4 0.60.81.0 1.95 formation redshift = 2 truncation redshifts Introduction - Truncation models

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

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

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

7. Christine Ruhland - The color-magnitude relation

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

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

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

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

12. Christine Ruhland - The color-magnitude relation 0.2 1.2 0.4 0.60.81.0 1.95 formation redshift = 2 truncation redshifts Truncation models

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

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