The dark
matterside of quiescent
galaxies
Why is dark matter important?
● Key ingredient in galaxy formation and evolution
● Crucial for mapping observations to simulations
Dark
matter
Galaxies
● Gas infall rate and temperature
● Merger rate
● Adiabatic contraction (inflowing gas)
The stellar-to-halo mass relation (SHMR)
The generalized SHMR. Star formation activity
Weak gravitational lensing
Weak gravitational lensing
Weak gravitational lensing
The Kilo Degree Survey (KiDS)
● ESO public imaging survey from the 4m VLT Survey Telescope (VST) ● 1,350 square degrees in u,g,r,i. Completed in 2019.
● Full overlap with VISTA Kilo degree INfrared Galaxy Survey ● Overlap with GAMA
● Highlights:
○ Cosmological constraints from cosmic shear
○ Galaxy alignments
○ Strong lensing
SDSS massive (M* > 10^11) elliptical galaxies
● Why SDSS?
○ Spectroscopy is important: spec-z, velocity dispersion, line indices
● Why massive ellipticals?
○ Easier to model, stellar masses are more robust, mostly centrals (easier to interpret weak
Questions
How does halo mass depend on:
● Stellar mass density profile
● Stellar velocity dispersion, at fixed stellar mass
Questions
How does halo mass depend on:
● Stellar mass density profile
● Stellar velocity dispersion, at fixed stellar mass
Stellar mass measurements
● r-band flux from Sersic profile fitting (Roy et al. in prep.)
● M*/L from SED fit to u,g,r,i,Z colors from matched-aperture photometry
Weak lensing measurements
● Forward modeling of population of galaxies and halos, described by a few parameters
● Bayesian hierarchical inference formalism (Sonnenfeld & Leauthaud 2018)
Stellar age proxies
Results (preliminary)
Summary
● Dark matter halo mass measurements allow us to draw connections between galaxy properties and their assembly history
● KiDS weak lensing observations of SDSS ellipticals put upper limit on the spread in halo mass between younger and older galaxies at fixed M*
