Fakultäten » Mathematisch-naturwissenschaftliche Fakultät » Physik-Institut » Prof. Dr. Philippe Jetzer » Tortora

Completed research project

Title / Titel Central dark matter trends in early-type galaxies from strong lensing,
dynamics and stellar populations
PDF Abstract (PDF, 14 KB)
Summary / Zusammenfassung We analyzed the correlations between central dark matter (DM) content of early-type
galaxies and their sizes and ages, using a sample of intermediate-redshift (z » 0.2) gravitational
lenses from the SLACS survey. We decomposed the deprojected galaxy masses
into DM and stellar components using combinations of strong lensing, stellar dynamics,
and stellar populations modelling. For a given stellar mass, we found that for galaxies
with larger sizes, the DM fraction increases and the mean DM density decreases, consistently
with the cuspy halos expected in cosmological formation scenarios. The DM
fraction also decreases with stellar age, which can be partially explained by the inverse
correlation between size and age. The residual trend points to systematic dependencies
on formation epoch of halo contraction or stellar initial mass functions. These results are
quite similar for the lens and local galaxies, showing no evidence of galaxy evolution over
the last » 3 Gyr other than passive stellar ageing.
We investigated scaling relations between the DM halo model parameters for a sample
of intermediate redshift early-type galaxies (ETGs) resorting on a combined analysis of
gravitational lensing and dynamics. Assuming as a reference model for the dark halo a
Navarro-Frenk-White profile and a Salpeter initial mass function (IMF) to estimate stellar
masses, we found that the column density S and the Newtonian acceleration within
the halo characteristic radius rs and effective radius Reff are not universal quantities,
but correlate with the luminosity LV , the stellar mass M? and the halo mass M200, contrarily
to what is expected from recent claims in literature. We finally discussed a tight
correlation among the DM mass MDM(Reff ) within the effective radius Reff , the stellar
mass M?(Reff ) and Reff itself. The slope of the scaling relations discussed here strongly
depends, however, on the DM halo model and the IMF adopted so that these ingredients
have to be better constrained in order to draw definitive conclusions on the DM scaling
relations for ETGs.
Publications / Publikationen Astrophys,. J., Volume 721, (2010), pp. L1

Mon. Not. R. Astron. Soc., Volume 409, (2010), pp. 1570

Project leadership and contacts /
Projektleitung und Kontakte
Dr. Crescenzo Tortora, PhD (Project Leader)
Funding source(s) /
Unterstützt durch
SNF (Personen- und Projektförderung)
Duration of Project / Projektdauer Jul 2010 to Jun 2011