Research Group
"Origin and Evolution of Galaxies"
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Summary of a journal-club

Date Subject Presented by
22 march 2012 Scaling relation of dwarf galaxies in the Coma cluster

We study the fundamental and the photometric plane of a sample of ~50 dwarf galaxies within the core of Coma cluster observed with DEIMOS on Keck II down to R-band luminosity of -15 Magnitudes. Deimos with sampling rate of 0.3 Angstrom per pixel and FWHM resolution of 1.6 Angstrom is suitable for observations of very faint dwarf galaxies and small velocity dispersions. It enables us to measure the velocity dispersions down to ~10 km/s for the wavelength range between 7500 to 10,000 Angstrom. Calcium triplet lines in this range allow us to obtain the velocity dispersion for the sample galaxies with high precision. We also performed a comprehensive error analysis to better estimate the uncertainties of this key observable. We also carried out a galaxy structure modeling using the ACS I-band images for a larger sample. We found larger velocity dispersions for fainter dwarfs than what expected from mass-luminosity trends of brighter Coma galaxies. In addition, fainter galaxies do not lie on the fundamental plane of brighter dwarf galaxies and their deviations from the fundamental plane increases as their luminosities, central velocity dispersions and Sersic indices decrease. We also noticed that those faint galaxies, which are outliers in the fundamental plane relation, have excess light at their central region with respect to their corresponding Sersic model. Photometric plane for the sample galaxies shows reduced scatter around the plane at the faint end, in comparison to the same in the fundamental plane.

Ehsan Kourkchi
Inst. Theoretical Physics Mathematics, Teheran

Image : D1 Deep Field from the Legacy Survey of the Canada-France-Hawaï Telescope (CFHTLS)
TERAPIX Data Processing Center (CNRS/INSU - IAP - CEA)