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Todays galaxies experienced cosmic reionization at different times in different locations. For the first time, reionization ($50%$ ionized) redshifts, $z_R$, at the location of their progenitors are derived from new, fully-coupled radiation-hydrodynamics simulation of galaxy formation and reionization at $z > 6$, matched to N-body simulation to z = 0. Constrained initial conditions were chosen to form the well-known structures of the local universe, including the Local Group and Virgo, in a (91 Mpc)$^3$ volume large enough to model both global and local reionization. Reionization simulation CoDa I-AMR, by CPU-GPU code EMMA, used (2048)$^3$ particles and (2048)$^3$ initial cells, adaptively-refined, while N-body simulation CoDa I-DM2048, by Gadget2, used (2048)$^3$ particles, to find reionization times for all galaxies at z = 0 with masses $M(z=0)ge 10^8 M_odot$. Galaxies with $M(z=0) gtrsim 10^{11} M_odot$ reionized earlier than the universe as a whole, by up to $sim$ 500 Myrs, with significant scatter. For Milky-Way-like galaxies, $z_R$ ranged from 8 to 15. Galaxies with $M(z=0) lesssim 10^{11} M_odot$ typically reionized as late or later than globally-averaged $50%$ reionization at $langle z_Rrangle =7.8$, in neighborhoods where reionization was completed by external radiation. The spread of reionization times within galaxies was sometimes as large as the galaxy-to-galaxy scatter. The Milky Way and M31 reionized earlier than global reionization but later than typical for their mass, neither dominated by external radiation. Their most massive progenitors at $z>6$ had $z_R$ = 9.8 (MW) and 11 (M31), while their total masses had $z_R$ = 8.2 (both).
We examine the reionization history of present-day galaxies by explicitly tracing the building blocks of halos from the Cosmic Reionization On Computers project. We track dark matter particles that belong to $z=0$ halos to trace the neutral fractions
Although there are many more stellar population studies of elliptical and lenticular galaxies, studies of spiral galaxies are catching up, due to higher signal to noise data on one hand, and better analysis methods on the other. Here I start by discu
In this study, we have carried out a detailed, statistical analysis of isolated model galaxies, taking advantage of publicly available hierarchical galaxy formation models. To select isolated galaxies, we employ 2D methods widely used in the observat
We discovered a sample of 250 Ly-Alpha emitting (LAE) galaxies at z=2.1 in an ultra-deep 3727 A narrow-band MUSYC image of the Extended Chandra Deep Field-South. LAEs were selected to have rest-frame equivalent widths (EW) > 20 A and emission line fl
Using the Millennium-II Simulation dark matter sub-halo merger histories, we created mock catalogs of Lyman Alpha Emitting (LAE) galaxies at z=3.1 to study the properties of their descendants. Several models were created by selecting the sub-halos to