Science Question:

How do we relate the z=0 structure to the merger history of the halos?

Do this in group environments within the cluster.

Aims:

 - Identify disk like objects in both FP and SAMs at  z=0 and z=0.43.

     - Pascal to provide Velociraptor outputs for hydro.

          - Classify disks based on fraction of stellar kinetic energy in ordered rotation.(http://arxiv.org/abs/1004.5386)

     - SAM outputs exist. 

          - Classify disks based on BoverT (B/T<0.3 for spirals and >0.5 for ellipticals)

 - Look at their merger histories in the MUSIC DM run. 

     - Identify halos which host galaxies in question.

Previous Findings:

Comparison of the fraction of spirals observed in the GAMA groups as a function of group mass with that determined

from simulation data. GAMA galaxies were classified using a sersic index vs colour index plot, where early-type and

late-type galaxies form a binomial distribution, while the simulated galaxies were classed as elliptical if they underwent

a major merjor between a = 0.4 and 0.8

Results:

1: Classify disks based on BoverT in SAM outputs

Literature values from Hopkins et al. (2009  http://adsabs.harvard.edu/abs/2009MNRAS.397..802H ): they use B/T>0.5 for bulge-dominated; the figure below for their full model (and observations) suggests B/T<0.3 to define disks. 

Plots from the simulation data:

figure 1.1 Plots generated from the Galform final snapshot, showing the average BoverT for each galaxy stellar mass bin,

corresponding to that taken from Hopkins et al. (2009) above. BoverT = 0 and 1 have been removed. 

Figure 1.2 Comparison between the Galform (left) and Galacticus BoverT values across the galaxy stellar masses.

figure 1.3 comparison of BoverT vs specific SFR between Galform (left) and Galacticus.

figure 1.4 Comparing galaxies defined as spiral (blue) or elliptical (red) depending on their BoverT value (Spiral = BoverT < 0.3, Elliptical > 0.5), 

for Galform (left) and Galacticus (right). Galaxies with BoverT = 0 were removed. Orphan galaxies (not removed here), when separately plotted,

appear to have the same features and distributions as these plots.

figure 1.5 Same plot for the observed GAMA sample, where galaxies have been classified by a

basic sersic-index-only cutoff point of 2.2. (n<2.2 = spiral, n>2.2 = elliptical)

Variations of the timescale of simulated major merger events used to define an elliptical vs the observed transformation of galaxies in GAMA:

SUMMARY:

Plotting BoverT against stellar mass gives similar results to what has been observed for the Galform data, however the Galacticus data 

appears to deviate significantly at lower stellar masses. The observed trends in both datasets remain consistent through higher

redshift values.

Defining galaxies as spirals or ellipticals using the BoverT quantity results in stellar mass v sSFR plots which vary significantly between

the two datasets. For Galacticus, the classification successfully separates the two main populations in the corresponding Mstar vs sSFR plot.

The red population in the upper right of the Galacticus plot is likely small irregular galaxies closer to spherical than disk-like undergoing star formation

Initial Full Physics results:

KrotvsMstar.pdf