Roberto Gonzalez Reyes Astronomy and Astrophysics
  Research interest -- Cosmology: Large scale structures, galaxy clusters, DM-galaxy connection, environment. Computational Astrophysics: N-body parallel code developement, initial conditions, LSS and cluster/single galaxy zoom simulations, halo and structure identification analysis and statistics, galaxy/mock catalogs.  

Galaxy Properties on Environment

We use a semi-analytic model of galaxy formation to study signatures of large-scale modulations in the star formation activity in galaxies. In order to do this we define local and global estimators of density around galaxies. The former are computed using a VT technique, and the latter by normalised distance to haloes and voids, in terms of the virial and void radii, respectively. We found interesting results, mostly due to changes in the underlying mass function of DM haloes in different subsamples, and an additional effect coming from stellar ages indicating that halo assembly also plays a role in shaping galaxy properties.

LSS Filament detection

We develope a new filament detection method to identify large scale filaments in cosmological simulations using halo positions and masses. Current project consist on identification of filaments in observational catalogs such as SDSS where we can look for galaxy features related with filamentary structure.

Constrained initial conditions

The goal is generate cosmological simulations which reproduce the galaxy distribution of the local universe. The Local universe (r<80mpc) is the most well observed region in the universe, and simulations resembling similar environment can be very useful for easier comparisons between DM and gas processes with galaxy distribution and properties. The process to generate the IC, start from the computation of the local density field based on local galaxy distribution (i.e. V8k catalog), then the potential and run gravity "backward" using linear theory or more sophisticated methods such as B-Z equation; therefore, we need to add small scale fluctuation using GIC code(Gnedin et al.).

Density field of low resolution constrained initial conditions (Left panels), and after refinement where we add small scale random fluctuations using GIC code (Right panels).

Milky Ways and Local Groups in Cosmological Simulations

Satellites in MW-like hosts: Environment dependence and close pairs. We study the satellite properties in the Bolshoi cosmological DM simulation, in particular in MW like halos in Local Group environments, and its connection with current detailed data for the Magellanic Clouds and other satellites.
Figure: MW mass probability distribution based on the properties of the MCs: Orange, galactocentric distance of the MCs; Green, total velocity of the clouds; Red, circular velocity of the clouds; Black, all constraints together.

MW and Local Group mass: Using statistics of MW-like and LG-like systems in Bolshoi simulation we can compute mass likelihoods for different set of constraints. We can use M31 proper motions from Sohn et al. 2012, and other observed LG properties to constraint the mass of the LG.

Figure: LG mass probability distribution.

Peta-scale N-body code implementation and optimization: New GroupLB loadbalancing scheme

New Load Balancing Technique for Cell-based AMR Applications: This is a long-term project, where we are intended to prepare a cosmological code, which can run simulations scalable up to thousands processors to take advantage of the new Peta-flop computer clusters. Part of my job here is the development of a new loadbalancing technique which ensure balanced and scalable split of work among processors with minimal comunication overhead.

The University of Chicago,The Kavli Institute for Cosmological Physics, 933 East 56th Street, office 223, Chicago, IL 60637
Phone: 773-969-0994