deletions | additions       diff --git a/subsection_Age_vs_lots_of__.tex b/subsection_Age_vs_lots_of__.tex  index 6d8ca2f..aed5810 100644  --- a/subsection_Age_vs_lots_of__.tex  +++ b/subsection_Age_vs_lots_of__.tex 
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\citet{Elmegreen2014}: Spiral structure develops around $1.4  \citet{Mandelker2015}: Analyzed clumps in simulated high-redshift galaxies, found clumpy galaxies to account for 40-60\% of galaxies across a wide range of redshifts; fraction had very weak dependence on redshift above z-1.. At high redshift clumps contribute to a larger fraction of the stellar mass and smaller fraction of the SFR. Long-lived clumps tend to migrate toward the disk center over ~10 disc dynamical times. Short-lived clumps are mostly on the disk edge. \citet{Behrendt2016}: Simulated a clumpy disk galaxy and compared with clumpy disks at z~2: Dynamical friction and tidal torques cause large (kpc-scale) clumps to migrate to the center, could contribute to formation of the bulge. The giant (kpc) clumps were shown in simulation to actually have significant substructure on the pc scales; ie giant clumps are actually groups of unresolved small clumps.   \citet{Kormendy2016} Super good review on evolution of clumps and bulge formation  \subsection{Morphological changes over time}  Current observations suggest that a large fraction of originally-disk galaxies can change morphology into elliptical shape. Does this transformation occur around the same time for all disks? Can disks spontaneously lose their disk structure over time, or does it have to undergo an interaction with another galaxy to transform? Is there a third option? Are there any very old disk galaxies, or do they all lose their disk structure at some point?