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

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

Christine Ruhland - The color-magnitude relation formation redshift = 2 truncation redshifts Introduction - Truncation models

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

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

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

Christine Ruhland - The color-magnitude relation

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

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)

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

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

Christine Ruhland - The color-magnitude relation formation redshift = 2 truncation redshifts Truncation models

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)

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