Present-Day Descendants of z=3.1 Ly  Emitting (LAE) Galaxies in the Millennium-II Halo Merger Trees Jean P. Walker Soler – Rutgers University Eric Gawiser (Advisor) – Rutgers University Nicholas A. Bond – Goddard Space Flight Center Nelson Padilla (Advisor) – Pontificia Universidad Católica de Chile Harold Francke – Pontificia Universidad Católica de Chile Millennium Workshop 2012, December 18, 2012

Outline of the Methodology Clustering Measurement (Observation) Clustering Measurement (Observation) Create Simulation Models Measure Clustering of Models Descendants of Models Dark Matter Halo Mass and Number Density

Motivation We wish to understand how galaxy populations connect with each other from one redshift to another. By using this selection technique, we do not use any gas physics in assigning galaxies to halos. While conditional mass function can predict the evolution of halos, it cannot provide sub-halo information. Using the Millennium-II simulation we can study how DM halo mass and age selection affect the properties of their descendants.

What is a Lyman α Emitter? B V O3 Selection Technique LAEs are identified by their strong Lyman α emission (EW rest > 40 Å). A combination of broadband and narrowband filters allow the measurement of the equivalent width of the Lyman α line. Basic Properties of z ~ 3.1 LAEs Age ~ 0.22 Gyr M Stellar ~ 5 x 10 9 M  E(B-V) ~ See Acquaviva et al MUSYC z~3.1 LAE Selection (BV – NB5000) > 1 BV is found from averaging the flux from B and V bands.

Clustering Measurement (Observation) Clustering measurements at z=3.1 (Gawiser et al. 2007) and at z=2.1 (Guaita et al. 2010) Figure from Guaita et al Ga07 LAE point from Gawiser et al r 0 = 3.6 Mpc Log 10 (M med ) = 10.9 n = 1.5x10 -3 Mpc -3

Selecting Lyman α Emitting Hosting Halo Mass Selected Models Mass Limit Selected a random sub- sampling of halos with M >= 10^10.6 M . Median Selected around the median mass of 10^10.9 M . +1σ Selected around the upper 1 sigma mass of 10^11.4 M . -1σ Selected around the lower 1 sigma mass of 10^10 M .

Age Definitions Formation Age-Age where the most massive sub-halo in timestep is half the mass of the most massive sub-halo in the merger tree. Assembly Age-Age where the sum of sub-halos in a timestep is half the mass of the most massive sub-halo in the merger tree. Merger Age-Determines where two central sub-halos have a ratio less than or equal to 3 and where one of their descendants becomes a satellite of the other descendant. We report when these two descendant sub-halos merge

Selecting Lyman α Emitting Hosting Halo Age Selected Models Formation Age: Young: Selected 5% youngest halos. Median: Selected 5% around the median age. Assembly Age: Young: Selected 5% youngest halos. Median: Selected 5% around the median age. Major Merger Age: Young: Selected 5% youngest halos. Median: Selected 5% around the median age.

Clustering of LAEs in Dark Matter Halos γ = 1.8Best Fit Median and Mass limit models have the measured clustering. The other models have their expected clustering.

Clustering of LAEs in Dark Matter Halos Best FitΥ = 1.8 Clustering of the Formation Young and Assembly Young is higher compared to their median aged models. Merger models are consistent with each other and measured LAE clustering.

Descendants of Mass Selected Models +1σ Mass Limit Median -1σ Descendants of the Median and Mass Limit models have similar median halo masses at each redshift. (M median = 10^12.58 M z=0) The uncertainty of the clustering measurement produce a spread in descendant median halo masses on the order of ~ 0.8 dex. (M median = 10^12.95 M z=0 and M median = 10^11.71 M ⊙ )

Descendants of Age Selected Models Form Young Form Median Assem Young Assem Median Merger Young Merger Median Descendants of age based models are have small deviation based on age selection (M median ~ 10^12.7 M z=0) The small deviations are negligible when compared to the uncertainty of the clustering measurements of LAEs at z=3.1.

Conclusions The central descendants (~66%) at z=0 have masses of Log 10 (M/M ⊙ )= and full distribution masses of M median = 10^ M ⊙. The central descendants have dark matter masses similar to L* type galaxies at z=0. Age-based models have very similar descendant mass distributions with a central median mass of Log 10 (M/M ⊙ )=12.0 and full distribution median mass of M median = 10^12.7 M ⊙. This method allows us to study the connections between galaxies at different redshifts as long as we make an assumption of galaxy/dark matter halo occupation. For details see Walker Soler et al. 2012