Day 920

Wednesday.


1507.01599
Star formation in mergers with cosmologically motivated initial conditions
Karman, et al

Use SAMs and cosmo merger trees to provide the ICs for multi-merger numerical hydro sims, and exploit these simulations to explore the effect of galaxy interaction and merging on SF.  Compute numerical realizations of 12 merger trees from z=1.5 to 0.  Include the effects of the large hot gaseous halo around all galaxies, following recent observations and predictions of galaxy formation models.  Find that including the hot gaseous halo has a number of important effects.  Firstly, as expected, the SFR on long timescales in increased due to cooling of the hot halo and refuelling of the cold gas reservoir.  Secondly, find that interactions do not always increase the SF in the long term.  This is partially due to the orbiting galaxies transferring gravitational energy to the hot gaseous haloes and raising their temperature.  Finally, find that the relative size of the starburst, when including the hot halo, is much smaller than previous studies showed.  The simulations also show that the order and timing of interactions are important for the evolution of a galaxy.  When multiple galaxies interact at the same time, the SF enhancement is less than when galaxies interact in series.  All these effects show the importance of including hot gas and cosmologically motivated merger trees in galaxy evolution models.  


1507.1858
A new method for measuring weak lensing magnification with weighted number counts
Gillis, Taylor

Present a new local method for optically estimating the local effects of magnification from WL, using a comparison of number counts in an arbitrary region of space to the expected unmagnified number counts.  This method has equivalent statistical power to the optimally-weighted correlation function method previously employed to measure magnification, but has the potential to be used for purposes such as mass mapping, and is also significantly computationally faster.  Present a proof-of-principle test of this method on data from the CFHTLenS, showing that its calculated magnification signals agree with predictions from model fits to shear data.  Finally, investigate how magnification data can be used to supplement shear data in determining the best-fit model mass profiles for galaxy DM haloes.  Find that at greater than z~0.6, the inclusion of magnification can often significantly improve the constraints on the components of the mass profile which relate to galaxies' local environment relative to shear alone, and in high-z, low-mass bins, it can have a higher S/N than the shear signal.