the scatter and evolution of the color-magnitude relation of elliptical galaxies christine ruhland...

The scatter and evolution of the color-magnitude relation

of elliptical galaxies

Christine RuhlandChristine Ruhland

MPIA Students Workshop March 2007MPIA 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


0.2

1.2

0.4 0.6 0.8 1.0

1.95

formation redshift = 2

truncation redshifts

Introduction - Truncation models


• Measurement of the scatter of the CMR Measurement of the scatter of the CMR (formation epoch)(formation epoch)

• 2 requirements:2 requirements:• Well-measured colorsWell-measured colors• Spectroscopic redshifts Spectroscopic redshifts

(good k-corrections)(good k-corrections)

Introduction - Goals


Data – GEMS and the spectroscopic redshifts

• Spectroscopic Spectroscopic redshift sample of redshift sample of 2138 objects2138 objects

• three redshift bins three redshift bins used to make used to make CMDsCMDs

531

269

191


• measurement of flux inside of the half light measurement of flux inside of the half light radius for the two GEMS filters v (606 nm) and radius for the two GEMS filters v (606 nm) and z (920 nm)z (920 nm)

• K-correction to get other filter bandsK-correction to get other filter bands

Method


Results – measurement of scatter and zeropoints in the CMD

• u-g over Mu-g over Mgg at at z = 0.1 calculated z = 0.1 calculated with restframe gridwith restframe grid

• Additional SDSS Additional SDSS data for z = 0.05data for z = 0.05

n < 2.5n < 2.5

n > 2.5AND redn > 2.5

AND red

MIPS24µm IR

MIPS24µm IR

X-rayX-ray

blueblue


Sérsic profile

• Profile describing the surface brightness of Profile describing the surface brightness of galaxiesgalaxies

• 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 The higher the steeper the inner part of the

profileprofile• n = 4 for bulges (deVaucouleurs profile)n = 4 for bulges (deVaucouleurs profile)

1/ /1

)( n

erreer 1/ /1

)( n

erreer


Results – measurement of scatter and zeropoints in the CMD

• u-g over Mu-g over Mgg at z = 0.1 at z = 0.1 calculated with calculated with restframe gridrestframe grid

• Additional SDSS data Additional SDSS data for z = 0.05for z = 0.05

• REAL error bars, i.e., REAL error bars, i.e., we measure the scatterwe measure the scatter


Comparison with truncation models


0.2

1.2

0.4 0.6 0.8 1.0

1.95

formation redshift = 2

truncation redshifts

Truncation models


More complex truncation models• Galaxies with different truncation redshifts and Galaxies with different truncation redshifts and

metallicities (distributed around solar metallicity)metallicities (distributed around solar metallicity)

583

24

34

93


Conclusion

• Red sequence has build up over a longer Red sequence has build up over a longer period of timeperiod of time

the scatter and evolution of the color-magnitude relation of elliptical galaxies christine ruhland...

Documents

correctionschristine

cmds531269191christine

scatterchristine ruhland

filter bandschristine

formation redshift

different truncation

objectsthree redshift

gems filters