We measure the stellar mass surface densities of early type galaxies by observing the micro-lensing of macro-lensed quasars caused by individual stars, including stellar remnants, brown dwarfs and red dwarfs too faint to produce photometric or spectroscopic signatures. Instead of observing multiple micro-lensing events in a single system, we combine single epoch X-ray snapshots of ten quadruple systems, and compare the measured relative magnifications for the images with those computed from macro-models. We use these to normalize a stellar mass fundamental plane constructed using a Salpeter IMF with a low mass cutoff of 0.1 solar masses and treat the zeropoint of the surface mass density as a free parameter. Our method measures the GRAININESS of the gravitational potential produced by individual stars, in contrast to methods that decompose a smooth total gravitational potential into two smooth components, one stellar and one dark. We find the median likelihood value for the normalization factor F by which the Salpeter stellar masses must be multiplied is 1.23, with a one sigma confidence range, dominated by small number statistics, of 0.77 < F < 2.10.
Astronomy Colloquium - Paul Schechter
Event time:
Thursday, October 23, 2014 - 2:30pm
Speaker:
Paul Schechter
Speaker Institution:
MIT
Talk Title:
"A calibration of the stellar-mass fundamental plane at <z> = 0.5 using the micro-lensing induced flux ratio anomalies of macro-lensed quasars"
Event description:
Location:
305 BASS
266 Whitney Avenue
New Haven, CT
06511
Admission:
Free