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Abstracts By Presenter's Last Name

B

 

Bautista

Baryon Acoustic Oscillations in the Final Lyman-Alpha Forest BOSS Sample

Presenter: Julian Bautista, Utah
Additional Authors: Kyle Dawson, the BOSS lyman-alpha forest working group

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         The Baryon Oscillation Spectroscopic Survey (BOSS) was designed to measure the baryon acoustic feature in the clustering of galaxies and in the lyman-alpha forest of high redshift quasars. In this talk, I will present the final analysis of BAO in the lyman-alpha forest of quasars. I will present the technical challenges to the measurement and the final results.

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Bautista - Poster

Modeling Classification/Redshift Efficiencies For Spectroscopic Surveys

Presenter: Julian Bautista, Utah
Additional Authors:

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          Our ability to estimate a redshift from eBOSS or DESI spectra will depend on the physical properties of the object, the magnitude, the redshift, and the observing conditions. We will explore the quality of spectral fits to infer the completeness of the sample as a function of angular and redshift coordinates. From these results, we will predict the completeness of the eBOSS galaxy and quasar samples so that the anisotropic effects of redshift failures can be modelled in the clustering studies. The work is just beginning for eBOSS and will inform clustering analysis for the DESI program that will be conducted at much higher number density.

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Behroozi

Linking Halo Assembly with Galaxy Star Formation Rates

Presenter: Peter Behroozi, University of California, Berkeley
Additional Authors:

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         We summarize observational evidence for a connection between halo assembly rates and galaxy star formation rates, and discuss preliminary results from the next generation of self-consistent galaxy—halo matching models that incorporate these connections.

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Berlind

Probing the Nature of Assembly Bias

Presenter: Andreas Berlind, Vanderbilt University
Additional Authors: Andres Salcedo, Ariyeh Maller, Manodeep Sinha, Peter Behroozi, Risa Wechsler, Jonathan Florez, Victor Calderon, Duncan Campbell, Sheila Kannappan, Amanda Moffett, Kathleen Eckert, David Stark

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         I will present results from theoretical and observational efforts to understand and detect assembly bias in the halo and galaxy distributions. On the theoretical front, we have studied halo assembly bias in detail, looking at the strength of assembly bias for various halo properties and examining to what extent it can be explained by a sub-population of halos that have experienced recent mass loss. On the observational front, we have examined the properties of dwarf galaxies from the RESOLVE/ECO surveys, contrasting galaxies in different density environments. By comparing these measurements to mock catalogs, we are able to constrain the type of assembly bias that is needed to explain the observations.

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Berti

Galactic Conformity from Z=0.2-1 with PRIMUS

Presenter: Angela Berti, UC San Diego
Additional Authors: Alison Coil

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         We test for galactic conformity from z=0.2-1.0 to a projected distance of 5 Mpc using spectroscopic redshifts from the PRism MUlti-object Survey (PRIMUS). Our sample consists of ~60,000 galaxies in five separate fields covering a total of ~5.5 square degrees, which allows us to account for cosmic variance. Dividing our sample into star-forming and quiescent galaxies using a cut in specific star formation rate, we identify star-forming and quiescent “isolated primary” galaxies. We match the redshift and stellar mass distributions of these samples, to control for correlations between quiescent fraction and redshift and stellar mass. We detect a significant conformity signal (>3 sigma) of ~5% on scales of 0-1 Mpc and a 2.5-sigma signal of ~1% on scales of 1-3 Mpc. We also test for redshift and stellar mass dependence of the conformity signal within our sample.

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Brodwin

The Era of Galaxy Formation in Galaxy Clusters

Presenter: Mark Brodwin, UMKC
Additional Authors:

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         I will describe the evidence for an epoch of significant growth of cluster galaxies at z ~ 1.5. Recent observations have finally ruled out simple monolithic collapse models that, despite being unphysical (or at least unhierarchical), adequately describe cluster evolution in the optical at z < 1. Measurements of rapid evolution in rest-frame near-infrared luminosity functions, stochastic evolution in color-magnitude relations, and enhanced rates of mergers, star formation and AGN activity, all suggest the z ~ 1.5 era is a very active one in the formation and assembly of massive cluster galaxies. Guided by these multiple lines of evidence, a physical picture has emerged that predicts that galaxy mergers are a key driver of the observed evolution.

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C

 

Calderon

Probing the Stellar Content of Galaxy Groups With Value-Added Group Catalogues in the SDSS Dr7

Presenter: Victor Calderon, Vanderbilt University
Additional Authors: Andreas Berlind; Manodeep Sinha; Cameron McBride

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         We directly study the relationship between galaxy properties and their dark matter halos using galaxy group catalogues from the Sloan Digital Sky Survey (SDSS) Data Release 7 (DR7). Specifically, we use the Berlind et. al. (2006) Friends-of-Friends group finding algorithm to identify galaxy groups and clusters in three volume-limited samples. We assign group masses, Mgroup, to the galaxy groups via abundance matching based on their total luminosity, and we designate galaxies as centrals or satellites, where each central galaxy is the brightest member of its group. Additionally, we assign stellar masses, M, and star formation rates, SFRs, to the galaxies from the MPA-JHU value-added catalogue. We explore the relationships between M, SFR, and Mgroup for central and satellite galaxies, as well as for galaxy groups as a whole. We also present a set of mock group catalogues that are constructed from N-body simulations and we use them to estimate the impact of group-finding errors on our results, thus allowing us to directly place constraints on the galaxy-halo connection.

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Campbell

Abundance Matching in a Universe With Assembly Bias

Presenter: Duncan Campbell, Yale University
Additional Authors: Nikhil Padmanabhan, Frank C. van den Bosch

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         I present a tunable abundance matching model for stellar mass and specific star formation rate that naturally includes galaxy assembly bias. I give special attention to the stellar mass--halo mass relation, and the dependence of the quenched fraction of central galaxies on host halo mass. Given this and other models, clustering statistics can be used as a method to constrain empirical models with galaxy assembly bias. Traditional estimates of halo mass that use the total stellar mass content of haloes are not able to distinguish this class of models, however, projected correlation functions retain significant power in this respect.

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Coil

AGN Clustering at Z~0.7

Presenter: Alison Coil, UC San Diego
Additional Authors:

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         I will present the observed clustering of X-ray, radio, and IR-selected AGN samples in the PRIMUS redshift survey at z~0.7. I will show that the differences observed in the clustering properties of AGN identified at different wavelengths can be understood entirely in terms of the clustering of their host galaxy populations. The combination of the dependence of galaxy clustering on stellar mass and star formation rate and observational biases in AGN selection can fully reconcile and explain the differences observed in the clustering properties of AGN selected at different wavelengths. These results argue against AGN triggering being connected to dark matter halo mass.

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Coupon

The Gas Fraction Evolution Out to Z=1 in Galaxy Groups

Presenter: Jean Coupon, University of Geneva
Additional Authors: Miriam Ramos, Dominique Eckert

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         Star formation efficiency in dark matter haloes is currently depicted as a subtle balance between cold flows supplying the gas material to form new stars, and processes either preventing the gas from cooling, or ejecting it. Those processes causing star formation in-efficiency and their halo-mass dependence are under active investigation by the observers and simulation communities, because they are key to understand galaxy evolution. If the mechanisms ejecting the gas in small-mass haloes is relatively well understood (supernovae, stellar winds), the picture gets more complicated with increasing mass, when attempting to quantify, for example, the impact of active galaxies (thermal blast, self-regulated AGNs) on the gas temperature. For observers, the galaxy group halo mass regime is particularly interesting because it is where the relative contribution of AGN feedback over gravitational heating is most debated. But observing the hot gas content in this mass regime is extremely challenging given the sensitivity of current X-ray and SZ instruments, and one must necessarily rely on stacking analysis of large galaxy samples to obtain meaningful results (e.g. Planck Collaboration XI 2015, Anderson et al. 2015). In this talk, I will present results of the gas fraction evolution as a function of redshift in the galaxy group mass regime (Mh > 3×1012 M) from z=0.2 to z=1.0, measured by means of stacked quantities derived from a unique combination, over 20 deg2, of optical (CFHTLS), near-IR (MIRACLES survey, Kab < 22), lensing (CFHTLenS) and X-ray data from the XXL survey.

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Croft

Relativistic Probes of Galaxies & Their Halos

Presenter: Rupert Croft, Carnegie Mellon University
Additional Authors:

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         Relativistic effects can alter the relationship between the intrinsic and observed properties of galaxies. These include the gravitational redshift, which depends on the depth of halo potential wells, and relativistic beaming which is sensitive to the interplay between galaxy peculiar velocities and their spectra. Large surveys of galaxies have begun to make measurements of these effects possible, and they offer us a new way look at the relationships between galaxies and their surrounding dark matter. I will present results from hydrodynamic simulations showing how the processes of galaxy formation can impact relativistic effects, as well as some preliminary measurements from galaxy survey data.

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D

 

Dalal

Detecting Dark Matter Substructure Using Dusty Galaxies

Presenter: Neal Dalal, Illinois
Additional Authors:



         Dusty star forming galaxies are found in large numbers by CMB surveys like SPT and ACT. I will describe how ALMA observations of these galaxies may be used to measure the amount of dark matter substructure that exists in typical galaxy halos. I will show preliminary results from our ALMA Cycle 2 observations.

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Dawson

eBOSS: Survey Overview & Challenges

Presenter: Kyle Dawson, University of Utah
Additional Authors: Stephen Bailey, Julien Guy, Julian Bautista, Tim Hutchinson, David Kirkby, Daniel Margala, Vivek Mariappan, Isabelle Paris, Nao Suzuki

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         In this talk I will present an overview of the extended Baryon Oscillation Spectroscopic Survey (eBOSS). eBOSS is a six year spectroscopic survey of luminous red galaxies (LRG), emission line galaxies (ELG), and quasars to trace the clustering of matter on all scales. I will present the sample selection and expected cosmological constraints from this program. The bulk of the talk will focus on the challenges we are now addressing in converting these samples into a useful catalog for clustering studies.

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Decker

Massive & Distant Clusters of Wise Survey (MaDCoWS): Stellar Mass Fraction in IR-Selected Clusters at Z ~ 1

Presenter: Bandon Decker, University of Missouri -- Kansas City
Additional Authors: Mark Brodwin



         The Massive and Distant Clusters of WISE Survey (MaDCoWS) is an infrared-selected galaxy cluster survey that identifies z~1 candidate clusters over the full extragalactic sky from over densities in the Wide-field Infrared Survey Explorer (WISE) AllWISE data release. We have measured Sunyaev-Zel'dovich (SZ) masses for a subset of the sample using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) and we measure stellar masses using rest-frame H-band luminosities derived from Spitzer Space Telescope observations. We have SZ detections and masses for 14 MaDCoWS clusters and Spitzer data in hand for ten of those 14 (with the rest being observed this Cycle). We measure and compare the cluster stellar mass fractions of this infrared selected sample with an SZ selected sample of clusters from the South Pole Telescope that covers a similar range in mass and redshift.

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Desmond

Testing Halo Abundance Matching With Galaxy Dynamics

Presenter: Harry Desmond, Stanford
Additional Authors:

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         Halo Abundance Matching (AM) is a simple technique for assigning stellar masses to halos produced in dark matter-only simulations, by assuming a nearly monotonic relationship between stellar mass and halo mass or velocity. I will discuss recent work (arXiv:1506.00169) aimed at testing and constraining this framework by examining its implications for the dynamics of spiral galaxies, in particular the Tully-Fisher and mass-size relations. I will show that under suitable conditions AM-based models can account for the basic properties of these relations, but have trouble reproducing the observed scatter in galaxy sizes and the correlation between velocity and radius residuals. These problems indicate that a correlation between galaxy and halo properties important for the dynamics of spirals is absent from the model. I will speculate on the nature of this correlation, and close by discussing ongoing work aimed at extending this analysis to the elliptical galaxy regime.

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Di Matteo

Cosmological Simulations of Galaxy Formation: the High-Z Universe

Presenter: Tiziana Di Matteo, CMU
Additional Authors:



         I will discuss recent progress in cosmological hydrodynamic simulations of galaxy formation at unprecedented volumes and resolution. I will focus on the MassiveBlackII and BlueTides simulations to probe the high redshift universe. The simulated volumes provide us with tens to hundreds of thousands of galaxies simulated at hundreds of parsec resolution. They cover a wide range of properties and a direct link between the baryonic component and dark matter. We now have the statistical power to interpret observations and make predictions for surveys in the near future.

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Diemer

The Splashback Radius as a Physical Halo Boundary

Presenter: Benedikt Diemer, Harvard
Additional Authors: Surhud More, Andrey Kravtsov

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         Models of the galaxy-halo connection are generally based on a simulated distribution of dark matter halos and subhalos, as well as their growth and merger histories. However, such a description of the halo population implicitly relies on a particular (and often arbitrary) definition of the halo boundary, e.g. the “virial” radius. In this talk, I will show that, contrary to common belief, halos have a well-defined outer edge: the “splashback radius” (Rsp) is marked by particles at the apocenter of their first orbit after infall and imprints itself on the density profile as a sharp steepening. By definition, Rsp separates material that is orbiting in the halo from material that has not fallen in yet, making it a physically motivated halo boundary. I will demonstrate that Rsp depends on the mass accretion rate of a halo, and that it is significantly larger than the commonly used radius definitions. I will illustrate how this new definition changes inferences about the mass accretion history of halos, as well as whether they are called subhalos.

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Diemer - Poster

A Universal Model for Halo Concentrations

Presenter: Benedikt Diemer, Harvard
Additional Authors: Andrey Kravtsov

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         We present a numerical study of dark matter halo concentrations in LCDM and self-similar cosmologies. We show that the relation between concentration, c, and peak height, ν, exhibits the smallest deviations from universality if halo masses are defined with respect to the critical density of the universe. These deviations can be explained by the residual dependence of concentration on the local slope of the matter power spectrum, n, which affects both the normalization and shape of the c-ν relation. We represent c as a universal seven-parameter function of only ν and n which matches our ΛCDM results to ≲5% accuracy up to z=6. The predictions of our model differ significantly from all models previously proposed in the literature at high masses and redshifts.

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Dorta - Poster

The BOSS Great Wall. The Biggest Supercluster System Ever Found

Presenter: Antonio Montero Dorta, University of Utah
Additional Authors:

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         By generating a luminosity-density field, smoothed over 8 h-1 Mpc, we have discovered one of the most extended and massive system of superclusters ever found in the Universe. The system, that we call the BOSS Great Wall (BGW), consists of two walls with diameters 186 and 173 h-1 Mpc, and two other major superclusters with diameters 64 and 91 h-1 Mpc, respectively. As a whole, the BGW consists of 830 galaxies with mean redshift z=0.47 and an estimated total mass of 2x1017 h-1 Mʘ. The morphology of the superclusters in the BGW system is similar to that of the superclusters in the Sloan Great Wall region.

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Dorta - Poster 2

The Intrinsic Halo-Galaxy Connection from BOSS

Presenter: Antonio Montero Dorta, University of Utah
Additional Authors:

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         Our goal is to combine our detailed characterization of the intrinsic properties of the red sequence (RS) at z~0.55 from the BOSS survey (and the completeness in the CMASS sample), with N-body numerical simulations to investigate the intrinsic physical parameters that govern mass clustering and the halo-galaxy connection. We will start by generating a set of hyper-realistic mock catalogs using the MultiDark simulation that obey the derived intrinsic color-magnitude distribution/luminosity function (LF)/L-sigma relation, for different cosmologies and where the halo-galaxy link is conveniently parametrized. By applying our error model and the CMASS selection criteria to the resulting set of catalogs and fitting for the observed clustering properties and the observed LF, constraints on cosmological parameters and on the physically-motivated parameters of the halo-galaxy connection model can be placed.

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F

 

Feldmann

The Formation of Massive, Quiescent Galaxies at Cosmic Noon

Presenter: Robert Feldmann, University of California, Berkeley
Additional Authors:

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         About a third of the massive galaxies at z~1.5-3 are quiescent, i.e., have colors consistent with a low specific star formation rate. Although their origin is not yet fully understood, it is often attributed to galactic outflows driven by star formation or AGN feedback, or to the formation of stable virial shocks in sufficiently massive halos. I will shine new light on this question with the help of MassiveFIRE, a suite of cosmological simulations with ~10 pc resolution focusing on massive galaxies at z~2. In particular, I will show that dark matter halos with low specific accretion rates preferentially host galaxies with reduced star formation rates and red broad-band colors. The fraction of such halos in large dark matter only simulations matches approximately the observed fraction of massive quiescent galaxies. This suggests that the halo accretion rate is a key parameter determining which massive galaxies at z~1.5-3 become quiescent. Empirical models that connect galaxy and halo evolution, such as halo occupation distribution or abundance matching models, assume a tight link between galaxy properties and the masses of their parent halos. These models will benefit from adding the specific accretion rate of halos as a second model parameter.

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Feng

Mocking Halos for Reconstructing the Cosmic Initial Condition

Presenter: Yu Feng, UC Berkeley
Additional Authors: TBD

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         We implement fastPM, an approximated particle mesh N-body solver as a reusable library. fastPM scales extremely well, reducing the wall-clock time nearly linearly with the number of CPUs. We explore the approximation parameter space with fastPM to optimize the agreement of halos with a N-body simulation, and found a scheme that produces a relatively accurate halo population down to M >1012h-1Mʘ, using 8 times of the computing time of 2LPT. Given the good parallel efficiency and the low cost of the scheme, fastPM can be useful for Monte Carlo Markov Chain calculations of the cosmic initial condition. Depending on the progress, I may report some preliminary results on reconstructing of cosmic initial condition from galaxies based on this work.

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Ferrero - Poster

Evolution of Tully-Fisher Relation, Halo or Galaxy?

Presenter: Santiago Ferrero, IATE - OAC
Additional Authors: Mario G. Abadi , Julio F. Navarro

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         The Tully-Fisher (TF) relation links the stellar content of disk galaxies with their rotation velocity, being one of the most fundamental scaling relation for disk galaxies. We use the EAGLE cosmological simulation to study the stellar-mass TF relation and its redshift evolution for the population of rotationally-supported galaxies with stellar mass Mstr > 109 M. We find a good agreement with available observations up to z = 1, which indicate no evolution in the slope and a weak decrease in the TF zero-point with redshift. Simulated galaxies have flat rotation curves but the relevance of the baryons depend on their mass. For Mstr < 2 × 1010 M galaxies are dark-matter dominated at all redshifts and consistent with sub-maximal disks where baryons account for only 28% of the mass within the half-mass radius of the stars rhalf. For more massive objects, stars can have equal or larger contributions than the dark matter, specially at high redshifts, and we see a correlation between the deviations in the TF 3.3 and the disks surface brightness. The slope of the TF is quite steep, Mstr ∝ Vhalf, where Vhalf is the circular velocity measured at rhalf. This steep slope can be explained by a simple model based on the scaling of virial quantities modulated by the varying efficiency of halos to collect baryons at their centers. The same model can also explain the weak evolution of the zero-point, mainly as a result of a weakly-evolving relation between stellar mass and halo mass, which is consistent with arguments from abundance matching. We report predictions for the stellar-mass TF relation up to z ~ 2.2 that can be tested once unbiased observational data becomes available.

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Flender

The Pairwise Kinematic Sunyaev-Zeldovich Signal from Galaxy Clusters

Presenter: Samuel Flender, Argonne National Lab
Additional Authors:

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         The pairwise kinematic Sunyaev-Zel'dovich (kSZ) signal from galaxy clusters is a probe of their relative momenta, and thus a potentially valuable source of cosmological information. In this talk I will present recent simulations of the pairwise kSZ signal. These simulations are generated using the output from a cosmological N-body simulation, where the intra-cluster gas is implemented via a semi-analytic model that can be varied in post-processing. I will show that modifications to the gas profile due to star formation and feedback reduce the pairwise kSZ amplitude of clusters by ~50%, relative to the naive "gas traces mass" assumption. I will further demonstrate that offsets between the true and observer-selected centers of clusters can reduce the overall amplitude of the pairwise kSZ signal by up to 10%, while errors in the redshifts can lead to an almost complete suppression of the signal at small separations. Finally, I will present recent evidence (with a statistical significance of ~4 Sigma) for the pairwise kSZ signal using galaxy clusters from the Dark Energy Survey, together with CMB data from the South Pole Telescope. I will conclude with forecasts for the detection significances of the pairwise kSZ signal with future experiments.

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Foreman

The Effective Field Theory of Large Scale Structures

Presenter: Simon Foreman, Stanford
Additional Authors:

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         The Effective Field Theory of Large Scale Structures (EFTofLSS) is a perturbative framework that describes the clustering of matter on weakly nonlinear cosmological scales. By augmenting the standard fluid description of dark matter with an effective stress tensor that parametrizes the effects of small-scale physics on large-scale clustering, the EFTofLSS provides a systematic way to compute nonlinear corrections to observables (such as power spectra) relevant for current and future surveys, without the convergence issues that have plagued previous perturbative approaches. In this talk, I will review the motivation for, and essential features of, the EFTofLSS, and present a collection of results that demonstrate the theory's ability to match the output of N-body simulations with high precision. These results indicate that perturbative techniques might be able to access much more of the information in large-scale structure than previously believed.

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Gnedin

What Globular Clusters Teach Us About the Assembly of Their Host Galaxies

Presenter: Oleg Gnedin, Michigan
Additional Authors: Hui Li, Bill Harris

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         Simulations of the formation of massive star clusters, their evolution into globular clusters, and connection to halos of their host galaxies.

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Guo

The Galaxy-Halo Connection From the Velocity Field

Presenter: Hong Guo, Shanghai Astronomical Observatory
Additional Authors: Zheng Zheng, Idit Zehavi et al.



         I will present our recent results using both the dark matter only and hydrodynamic simulations to relate galaxies to halos. The observed galaxy redshift-space distribution can be well modeled by including the velocity bias of the galaxies relative to the dark matter for both central and satellite galaxies. We also find a similar behavior of the galaxy-halo connection in the velocity field in the hydrodynamic simulations, which will provide tighter constraints to the galaxy formation and evolution models.

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H

 

Hand

A New Halo Model Approach To Modeling Rsd From the BOSS CMASS Power Spectrum

Presenter: Nick Hand, UC Berkeley
Additional Authors: Uros Seljak, Florian Beutler, Zvonimir Vlah

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         We present a new model for the redshift-space power spectrum of galaxies based upon the combination of perturbation theory and the halo model. We use a phase-space distribution function approach to model redshift space distortions and calibrate the perturbation theory using simulations when necessary. Our method allows the model to be accurate to approximately k = 0.4 h/Mpc. We describe the model details as well as the redshift space distortion constraints obtained from the application of the model to the BOSS CMASS galaxy sample.

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Harikane

Evolution of Stellar-to-Halo Mass Ratio at Z=0-7 Identified by Clustering Analysis with the Hubble Legacy Imaging and Early Subaru/Hyper Suprime-Cam Survey Data

Presenter: Yuichi Harikane, The University of Tokyo
Additional Authors: Masami Ouchi, Yoshiaki Ono, Surhud More, Shun Saito, Yen-Ting Lin, Jean Coupon, Kazuhiro Shimasaku, Takatoshi Shibuya, Paul A. Price, Lihwai Lin, Bau-Ching Hsieh, Masafumi Ishigaki, Yutaka Komiyama, John Silverman, Tadafumi Takata, Hiroko Tamazawa, and Ju

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         We present clustering analysis results from 10,540 Lyman break galaxies (LBGs) at z~4-7 that are identified in a combination of the Hubble legacy deep imaging and the complimentary large-area Subaru/Hyper Suprime-Cam data taken very recently. We measure angular correlation functions of these LBGs at z~4, 5, 6, and 7, and fit these measurements using halo occupation distribution (HOD) models that provide the estimates of halo masses, Mh~(1-20)×1011 M. Our Mh estimates agree with those obtained by previous clustering studies in a UV-magnitude vs. Mh plane, and allow us to calculate stellar-to-halo mass ratios (SHMRs) of the LBGs. By comparison with the z~0 SHMR given by SDSS, we identify evolution of the SHMR from z~0 to z~4, and z~4 to z~7 at the >98% confidence levels. The SHMR decreases by a factor of ~3 from z~0 to 4, and increase by a factor of ~5 from z~4 to 7. We obtain the baryon conversion efficiency (BCE) of our LBGs at z~4, and find that the BCE increases with increasing dark matter halo mass. We finally compare our clustering+HOD estimates with the abundance matching results, and conclude that the Mh estimates of the clustering+HOD analyses agree with those of the simple abundance matching within a factor of 3, and that the agreement is better with those of the sophisticated abundance matching techniques that include subhalos, incompleteness, and/or star formation rate+stellar mass function evolution.

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Hatch

The Structure & Evolution of a Forming Galaxy Cluster at Z=1.6

Presenter: Nina Hatch, University of Nottingham
Additional Authors:

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         The ancestors of galaxy clusters, known as protoclusters, are powerful laboratories for tracing the emergence of large scale structure and studying the influence of dense environments on galaxy formation in the early Universe. Using cosmological simulations I will demonstrate how the collapse of these structures occurs over several scales, so that at 1 < z < 3 protoclusters consist of multiple group-sized halos residing within a collapsing matter overdensity that can extend over 50 co-moving Mpc. I will then present new optical and infrared observations of a z=1.6 protocluster over the central 10 co-moving Mpc region. Using galaxies to trace its structure, I will show that the nascent cluster is surrounded by 5 additional galaxy groups. The structure of the protocluster reveals how much mass is available for its future growth. Using the Millennium Simulation, scaled to a Planck cosmology, to predict its growth rate over the next 9 billion years, I will show that this protocluster is likely to collapse into a Virgo-like cluster by the present day. I will then discuss how the environment of the protocluster affects the properties of its member galaxies. I will show how the galaxies in the groups of the protocluster are more massive, older and have less recent star formation than field galaxies. However we find no direct evidence of environmental quenching, instead we suggest that galaxy formation and/or merging proceeds at a faster rate in the peaks of the protocluster overdensity, which alters the galaxy mass function in these regions. We will discuss the implications of these findings for the formation of the cluster galaxy population.

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Hearin

High-Precision Modeling of the Galaxy-Halo Connection: a Community-Driven Approach with Halotools

Presenter: Andrew Hearin, Yale University
Additional Authors:

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         Although the modern form of galaxy-halo modeling has been in place for over ten years, there exists no common code base for carrying out large-scale structure calculations. Considering, for example, the advances in CMB science made possible by Boltzmann-solvers such as CMBFast, CAMB and CLASS, there are clear precedents for how theorists working in a well-defined subfield can mutually benefit from such a code base. Motivated by these and other examples, I present Halotools: an open-source, object-oriented python package for building and testing models of the galaxy-halo connection. Halotools is community-driven, and already includes contributions from over a dozen scientists spread across numerous universities. Designed with high-speed performance in mind, the package generates mock observations of synthetic galaxy populations with sufficient speed to conduct expansive MCMC likelihood analyses over a diverse and highly customizable set of models. The package includes an automated test suite and extensive web-hosted documentation and tutorials (halotools.readthedocs.org). I conclude the talk by describing how Halotools can be used to analyze existing datasets to obtain robust and novel constraints on galaxy evolution models, and by outlining the Halotools program to prepare the field of cosmology for the arrival of Stage IV dark energy experiments.

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Hong - Poster

Network Cosmology: What We Can Learn from Galaxy "Facebook"?

Presenter: Sungryong Hong, Univ of Texas at Austin
Additional Authors:

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         The large-scale distribution of galaxies is generally analyzed using the two-point correlation function. However, this statistic does not capture the topology of the distribution, and it is necessary to resort to higher order correlations to break degeneracies. We demonstrate that an alternate approach using network analysis can discriminate between topologically different distributions that have similar two- point correlations. We investigate two galaxy point distributions, one produced by a cosmological simulation and the other by a Lévy walk, that have different topologies but yield the same power-law two-point correlation function. For the cosmological simulation, we adopt the redshift z = 0.58 slice from Illustris (Vogelsberger et al. 2014A) and select galaxies larger than the stellar mass cut, 108M (solar masses). The two point correlation function of these simulated galaxies follows a single power- law, ξ(r) ~ r−1.5. Then, we generate Lévy walks matching the correlation function and abundance with the simulated galaxies. We find that, while the two galaxy populations have the same abundance and two point correlation function, their spatial distributions are very different; most prominently, filamentary structures, which are present in the simulation are absent in Lévy fractals. To quantify these missing topologies, we adopt network analysis tools and measure diameter, giant component, and transitivity from networks built by a conventional friends-of-friends recipe with various linking lengths. Unlike the abundance and two point correlation function, these network quantities reveal a clear separation between the two populations; therefore, the distributions of Lévy walks and simulated galaxies are statistically and topologically different. We find that the described network quantities offer an efficient tool for discriminating topologies and for comparing observed and theoretical distributions. We also show that the galaxy distribution simulated by Illustris is not a Lévy fractal.

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Hutchinson

Redmonster: Redshifting Millions of Spectra for LSS Studies

Presenter: Timothy Hutchinson, Utah
Additional Authors: Kyle Dawson, Adam Bolton

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         Large spectroscopic programs such as BOSS, eBOSS, and DESI produce millions of spectra of the objects targeted to trace the underlying density field. As programs become more ambitious, spectroscopic classification becomes more challenging due to the faintness of spectra. In addition, studies of halo occupation, assembly bias, and galaxy evolution require spectroscopic classification beyond a simple redshift. In this talk, I will present a new algorithm for spectroscopic classification now being used in the eBOSS program. Known as Redmonster, this approach relies on physically motivated spectral templates. Relative to BOSS, these templates reduce the freedom in fitting spectra and allow immediate interpretation of galaxy properties associated with the construction of the templates. I will present the algorithm and its performance on the eBOSS sample of luminous red galaxies.

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Ishikawa

The Very Wide-Field gzK Galaxy Survey

Presenter: Shogo Ishikawa, SOKENDAI/NAOJ
Additional Authors: Nobunari Kashikawa, Takashi Hamana, Jun Toshikawa, and Masafusa Onoue



         We present the results of clustering analysis on z~2 star-forming galaxies (sgzKs). By combining our data with publicly available archives, we succeeded to collect 41112 sgzKs, which is the largest sgzK sample yet, and derived high-quality two-point angular correlation functions (ACFs) that enable us to carry out halo occupation distribution (HOD) analysis. Our HOD analysis derived accurate mean halo mass that reside in sgzKs. The luminosity dependence of the HOD mass parameters were found to be approximately same as in the local Universe; however, the masses were larger than in the local Universe over all magnitude range. This implies that galaxies at z~2 tend to be formed in more massive dark haloes than in the local Universe; known as downsizing. By tracing the evolution of dark halo masses and the number of satellite galaxies, we revealed that faint LBGs at z~4 are expected to evolve into faint sgzKs (22<K<23) and into Milky-Way-like galaxies or elliptical galaxies at z=0, whereas the brightest sgzKs(18<K<21) could evolve into the central galaxies of galaxy clusters; i.e., BCGs in the local Universe. The stellar-to-halo-mass ratio (SHMR) is also investigated and confirmed that the SHMR at z~2 is almost consistent with model prediction and does not change significantly compared to the relation at z~0

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Jensen - Poster

Spectroscopic Signatures of Quasar Diversity

Presenter: Trey Jensen, Utah
Additional Authors: Kyle Dawson, Julian Bautista, Nao Suzuki, Vivek Mariappan

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         In this talk, we present the composite spectra of high redshift quasars observed in the Baryon Oscillation Spectroscopic Survey. We reproduce a known relationship between intrinsic luminosity and emission line strength and find two new trends in quasar diversity. First, we find a clear relationship between the broadband color and the outflow velocities in the broadline region. We attribute this to the orientation of the accretion disk relative to the observer. More interestingly, we find a clear evolution with redshift that has a signature identical to that of intrinsic luminosity. We argue that this finding indicates that both the luminosity/emission line relationship and the redshift evolution are a result of variations in the accretion efficiency.

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Kamble - Poster

Redshift Evolution of the Density of Neutral Hydrogen

Presenter: Vikrant Kamble, Utah
Additional Authors: Kyle Dawson, Julian Bautista, Nao Suzuki, Trey Jensen

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         Intrinsic to studies of the clustering of matter in the lyman-alpha forest are estimates of the true quasar continuum and of the mean transmission through neutral hydrogen. By dividing the sample of high redshift quasars from BOSS and eBOSS into bins based on their physical properties, we can identify quasars with nearly identical features both redward and blueward of the lyman-alpha emission line. From these samples of quasars, we can assess the errors in spectroscopic flux calibration and make multiple independent measurements of the transmission of lyman-alpha photons. With each independent measurement, we will assess the mean transmission of the lyman-alpha forest and the systematic errors associated with our uncertain models of quasar astrophysics.

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Kang

Galaxy Spin & the Large Scale Structure: Universality Behind the Non-Universality Relation

Presenter: Xi Kang, Purple Mountain Observatory
Additional Authors:

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         It is observationally found that the correlation between galaxy spin and large scale structure depends on galaxy type/mass. For massive galaxies, their spin is perpendicular to the filament, but for low-mass galaxies their spin is parallel to the filament direction. N-body simulation also predicts such a mass dependence between halo spin and large scale structure. We found that such a dependence is due to the mass accretion at early universe. For low mass haloes, their subhaloes are accreted perpendicular to the filament, and for high-mass haloes, most subhaloes are accreted along the filament. Such a manner well explains the observed correlation. We further identify the physical origin of such a correlation, and found that the anisotropy collapse of dark matter halo is universal, which can explain the non-universalty between galaxy/halo spin with the large scale structure.

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Kravtsov

Stellar Feedback on the Galaxy Stellar Mass-Halo Mass Relation

Presenter: Andrey Kravtsov, The University of Chicago
Additional Authors:

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         I will review our current knowledge about how the key properties of galaxies, such as stellar mass and size are related to halo mass and what recent galaxy formation simulations taught about how feedback affects and shapes these relations.

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Kravtsov - Poster

Non-Universal Star Formation in Turbulent Interstellar Medium

Presenter: Andrey Kravtsov, The University of Chicago
Additional Authors: Vadim Semenov, Nickolay Gnedin



         Recent observational evidence indicates variation of efficiencies at which giant molecular clouds (GMCs) convert their gas into stars. Consistent theory of galaxy formation must explain such variation. Common numerical implementations of star formation in galaxy formation modelling, in which star formation efficiency (SFE) is assumed constant (at the level of few %) above certain density threshold, by their design are not suitable for this purpose. We present a star formation implementation designed to work on scales ~10-50 pc that is based on a subgrid modelling of turbulence and recent results from direct simulations of star formation in turbulent GMCs. We show that our model predicts distribution of r.m.s. turbulent velocities consistent with local and extragalactic observations (on average few km/s on 100 pc scale). The model also predicts a wide variation of star formation efficiency per free fall time at odds with the usual assumption in star formation modelling. At the same time, our model predicts distribution of star formation rates in broad agreement with observations of both local and resolved extragalactic GMCs.

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Le Brun

Simulating the Evolution of the Most Massive Galaxy Clusters Since Redshift 1

Presenter: Amandine Le Brun, Service d'Astrophysique CEA Saclay
Additional Authors: Romain Teyssier, Monique Arnaud, Gabriel Pratt

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         The evolution of the dark matter profiles of high-mass galaxy clusters from z~1 to the present day remains poorly constrained and is a powerful test of the LambdaCDM model. Such a test requires systematic confrontations of observations of a representative sample of the Universe's most massive clusters, preferably in several redshift bins, with tailor-made numerical simulations. To date, there exist no cosmological numerical simulations with the exceptionally large volume (required to simulate the rarest, most massive clusters) and the resolution (required to resolve their structure) necessary to undertake such a project. We will present the first results from a simulation campaign aimed at producing large cosmological simulations that are 1 Gpc/h on a side and have a medium mass and spatial resolution. They are being complemented with very-high resolution zoom simulations which are progressively including the non-gravitational physics of galaxy formation such as star formation, supernova and AGN feedback. The simulations are produced using the AMR code RAMSES.

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Mansfield

Measuring Individual Splashback Radii in Cosmological Simulations

Presenter: Phil Mansfield, University of Chicago
Additional Authors:



         The splashback radius of a dark matter halo is a feature in the outer profile generated by particles on their first orbit. This feature is of interest because it is an observable tracer of accretion rate, because it forms a physically-motivated definition for halo boundaries, and because recent observations of the splashback radius appear to be in tension with results from simulations. Up to this point, all analysis of this feature has been done on stacked, spherically averaged profiles. We present a technique for robustly identifying the splashback radius of halos in cosmological simulations and apply it in the first systematic analysis of this feature in individual halos.

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Mao

Explore the Hidden Parameters in Abundance Matching

Presenter: Yao-Yuan Mao, Stanford University
Additional Authors: Risa Wechsler, Matthew Becker, Benjamin Lehmann

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         The abundance matching technique is a simple, heuristic description of the galaxy-halo connection, yet it has been shown to yield good fits to the clustering of galaxies and other observable spatial statistics. The choice of the halo property that is matched to galaxy luminosity (or stellar mass) further provides insights into the galaxy formation physics. In this talk I will discuss how the choice of the halo property used in the abundance matching technique acts as hidden parameters that control specific behaviors, such as assembly bias, in the resulting mock catalog. Our studies show the degeneracy among these parameters, and demonstrate that these parameters can be constrained by the observable clustering signals.

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Mariappan - Poster

Physically Motivated Spectral Templates for BOSS & eBOSS Quasars

Presenter: Vivek Mariappan, Utah
Additional Authors: Kyle Dawson, Julian Bautista, Nao Suzuki, Trey Jensen



         Redmonster is a new code being developed to automatically classify spectra produced in the BOSS, eBOSS and possibly DESI spectroscopic programs. The software requires well-understood spectral templates that fully span the diverse population of each target class for clustering studies. I will present the results from the early stages of development of quasar spectral templates for Redmonster. These templates are derived from composite spectra derived from subsamples of BOSS/eBOSS data divided by physically-observed quasar properties.

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More

Detection of Splashback Radius & Assembly Bias of Clusters

Presenter: Surhud More, Kavli IPMU
Additional Authors: Hironao Miyatake, Masahiro Takada, Andrey Kravtsov, Benedikt Diemer, Rachel Mandelbaum

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         Using two uniquely constructed subsamples of redMaPPer clusters in SDSS which have the same weak lensing mass, I will present observational evidence for the splashback radius and halo assembly bias. Taken at face value, the location of the splashback radius and the strength of assembly bias seem to be different from the expectations for the standard cosmological model. I will also talk about how these subsamples can be useful to do a number of tests of gas physics and galaxy formation in clusters.

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Nagai

Physics of Galaxy Cluster Outskirts

Presenter: Daisuke Nagai, Yale University
Additional Authors:

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         Recent advances in X-ray and microwave observations have provided unprecedented insights into the structure and evolution of the hot X-ray emitting intracluster medium (ICM) from their cores to the virialization region in the outskirts of galaxy clusters. Recent Sunyaev-Zel'dovich surveys (ACT, Planck, SPT) have provided new cluster catalogs, significantly expanding coverage of the mass-redshift plane, while Chandra and XMM-Newton X-ray follow-up programs have improved our understanding of cluster physics and evolution as well as the surveys themselves. However, the current cluster-based cosmological constraints are still limited by uncertainties in cluster astrophysics. In order to exploit the statistical power of the current and upcoming X-ray and microwave cluster surveys, we must improve our understanding of the structure and evolution of the ICM. In this talk, we will discuss recent advances in theoretical modeling and numerical simulations of galaxy clusters, with highlights on (1) the evolution of ICM profiles and scaling relations, (2) physical processes operating in the outskirts of galaxy clusters, and (3) impact of mergers on the ICM structure in groups and clusters.

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Ntampaka

Constraining Cosmology with the Velocity Distribution Function in Galaxy Clusters

Presenter: Michelle Ntampaka, CMU
Additional Authors:

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         I will present a new approach for quantifying the abundance of galaxy clusters and constraining cosmological parameters using dynamical measurements. In this method, the probability distribution of velocities for each cluster in the sample are summed to create a new statistic called the velocity distribution function (VDF), dn(v)/dv. The VDF can be measured more directly and precisely than the halo mass function and it can also be robustly predicted with cosmological simulations that capture the dynamics of subhalos or galaxies. A standard halo mass function analysis of mock cluster catalog dynamical masses favors a low Ωm and high σ8 , with the fiducial model lying well outside of the forecast constraints. In contrast, VDF constraints on cosmological parameters are in agreement with the fiducial model and show only minor bias when reasonable velocity errors are added.

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Paudel

Interaction of Dwarf Galaxies in Different Scale.

Presenter: Sanjaya Paudel, KASI, South Korea
Additional Authors:



         Predicted from the hierarchical cosmology, study of merging system has become a powerful tool in understanding of galaxy growth and evolution. We have undertaken a systematic search of tidally disturbed dwarf galaxies to understand such universal process in low mass scale and report that interaction between low mass galaxies are not rare as previously thought. However, our statistical analysis of the observed tidal features on dwarf galaxies shows that a majority of them are originated from dwarf-giant interactions. We present number of detailed case studies that explore structural and stellar population properties of dwarf galaxies which are ongoing victim of tidal forces of different scale, i.e. large from giant-dwarf interaction and small from dwarf-dwarf interaction. We will discuss importance of these examples to understand the formation and evolution of low mass early-type galaxies by the tidal harassment/string or dwarf-dwarf merger.

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Pranger

Identifying Connections Between Large-Scale Structure & Galaxy Evolution - a Comparison of Dynamically Active Galaxy Cluster at Low Redshift

Presenter: Florian Pranger, National Astronomical Research Institute of Thailand
Additional Authors: Chiara Ferrario, Harald Höller, Lee Kelvin, Ignacio Trujillo

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         The effect of environment on galaxy properties has been observed since more than 30 years. However, only about 10 years ago, people have started to investigate in detail the influence of the dynamics of galaxy clusters on the hosted galaxy populations and thus have begun to establish a link between large-scale structure research and galaxy evolutionary studies. We tried to connects the named research fields by investigating the dynamical states of nearby (z<0.1) galaxy clusters and cluster/group systems and analysing the evolution of their galaxies' properties, using XMM-EPIC X-ray data, 2dF and EFOSC2 multi-object spectroscopy as well as SDSS and ESO 2.2m WFI multi band imaging. We analysed galaxy surface brightness profiles and investigated spectral quantities (H-alpha and [OII] equivalent widths, star-formation rates), morphological descriptors (e.g. Gini-coefficient, M20 index) and galaxy rest-frame colours as functions of environment (cluster vs. field) and clustercentric distance and with respect to the morphological galaxy type. In addition, we investigated the distribution of various galaxy types in colour-magnitude space and physical space. We detected imprints of ongoing cluster mergers on the galaxy populations in terms of SF-activity and galaxy morphology. We found that dynamical friction and increased ram-pressure due to merger shock-waves are potential candidates for processes causing the observed changes in galaxy properties. Our interpretations are supported by our comprehensive numerical study of 12 galaxy clusters of different dynamical state. Based on our overall findings, we suggest a new scheme of galaxy transformation in clusters that is capable of explaining the correlations between galaxy morphology and the different types of surface-brightness profiles (up-bending, down-bending and purely exponential) throughout the disk-galaxy regime, while corresponding to well-established relations such as the morphology-density relation or the colour-density relation.

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Richardson

Gas Matters! Star Formation & Feedback Processes Affect Halos & Beyond

Presenter: Mark Richardson, University of Oxford
Additional Authors: Julien Devriendt, Adrianne Slyz

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         The shapes of galaxy and cluster halos play an important role in constraining Lambda CDM cosmology. While theory and N-body models predict triaxial halos, important when doing SZ and weak lensing analysis, gas cooling leads to more spherical halos, particularly on radii comparable to the disk. I will discuss a suite of simulations varying the prescription for star formation, supernova feedback, and radiative transfer, and show how these different models affect the shape and angular momentum of the halo constituents. Further, I will discuss how, in our simulations, AGN impact the evolution of the halo mass function and the baryon fraction of surrounding cosmic structure.

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Rodríguez-Torres

BOSS DR12: Clustering of Galaxies & Dark Matter Halos

Presenter: Sergio A. Rodríguez-Torres, Instituto de Física Teórica UAM/CSIC
Additional Authors:

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         BOSS SDSS-III is the largest redshift survey for large scale structure and a powerful sample for the study of the low redshift BAO. We combine the features of the survey, such as, geometry, angular incompleteness and stellar mass incompleteness, with the BigMultiDark simulation to do a study of the distribution of galaxies in the dark matter halos. Using this large N-Body simulation and the halo abundance matching, we find a remarkably good agreement with the 2-point and 3-point statistics of the data. I will present the model used to connect the galaxy population with the dark matter halos and the more relevant results obtained.

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Ruszkowski

Global Simulations of Galactic Winds Including Cosmic Ray Streaming & Diffusion

Presenter: Mateusz Ruszkowski, University of Michigan
Additional Authors: Karen Yang, Ellen Zweibel

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         Galactic outflows play an important role in galactic evolution. Despite their importance, a detailed understanding of the physical mechanisms responsible for the driving of these winds is lacking. In an effort to gain more insight into the nature of these flows, we perform global three-dimensional magneto-hydrodynamical simulations of an isolated starbursting galaxy. We focus on the dynamical role of cosmic rays injected by supernovae, and specifically on the impact of the streaming and anisotropic diffusion of cosmic rays along the magnetic fields. We find that these microphysical effects can have a significant effect on the wind launching and mass loading factors depending on the details of the plasma physics. Cosmic rays stream away from the densest regions near the galactic disk along partially ordered magnetic fields and, in the process, accelerate more tenuous gas away from the galaxy. Even a presence of cosmic rays at the level of 10% of the total energy density in the star formation sites is likely to have a notable impact on the wind launching.

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Rys - Poster

Real & Simulated IFU Observations of Low-Mass Early-Types: Environmental Influence Probed for Cluster Galaxies

Presenter: Agnieszka Rys, European Southern Observatory
Additional Authors:

         In our contribution we combine high-quality IFU data with a new set of numerical simulations to study low-mass early type galaxies in dense environments. Our study of dwarf early-types (dEs) in the Virgo cluster and in the field has produced the first large-scale maps of kinematic and stellar population properties of dEs in those environments. The large spatial extent (2D coverage out to 1 Reff) allowed us to obtain reliable dynamical properties as well as population gradients and spatially resolved star formation histories. In our latest analysis of a new, extended sample (20 objects) we study the environmental influence vs. internal feedback mechanisms. For the former, we turn to new proxies for local environment impact, luminosity and number densities, much more meaningful than simple clustrocentric distances. For the latter, we combine our and ATLAS3D samples to study scaling relations across the largest mass range for a homogeneous sample available for early types. A quantitative discrimination between various proposed (trans)formation processes is a complex issue, requiring making a priori assumptions about the progenitors of galaxies we observe and study today. Simulations which have attempted to address the question have only dealt with a limited number of setups, with the end result only rarely resembling today’s dEs. To bridge this gap between observations and theoretical predictions, we use the expertise gained in the IFU data analysis to look "through the eye of SAURON" at our new suite of high-resolution N-body simulations of dEs in the Virgo cluster. Mimicking the observer’s perspective as closely as possible, we can also indicate the existing instrumental and viewer limitations regarding what we are/are not able to detect as observers. Our mock data can be used as a testing ground for future observations: we can provide predictions which can later be tested by observers and scaled to match their data and instrument characteristics.

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S

 

Schmittfull

Large-Scale Structure Beyond the Power Spectrum

Presenter: Marcel Schmittfull, UC Berkeley/LBNL
Additional Authors: Tobias Baldauf, Uros Seljak, Yu Feng, Florian Beutler, Blake Sherwin, Man-Yat Chu

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         As recent and future galaxy surveys map the large-scale structure of the universe with unprecedented pace and precision, it is worthwhile to consider innovative data analysis methods beyond traditional Gaussian 2-point statistics to extract more cosmological information from those datasets. Such efforts are often plagued by substantially increased complexity of the analysis. Hoping to improve this, I will present simple, nearly optimal methods to measure 3-point statistics as easily as 2-point statistics, by cross-correlating the mass density with specific quadratic fields [arXiv:1411.6595]. Inspired by these results, I will argue that BAO reconstructions already combine 2-point statistics with certain 3- and 4-point functions automatically [arXiv:1508.06972]. I will present several new Eulerian and Lagrangian BAO reconstruction algorithms and discuss their performance in simulations.

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Seljak

Galaxy Halo Connection & the Information Content of Large Scale Structure

Presenter: Uros Seljak, Berkeley
Additional Authors:



         I will review the galaxy halo connection and its role in extracting the underlying information content about the universe.

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Shan

Weak Lensing Analysis of DECaLS Survey

Presenter: Huanyuan Shan, EPFL
Additional Authors:

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         We present the current weak lensing analysis of the DECaLS DR1 Survey (~3000 square degrees). The shape of faint galaxies are measured with the Tractor/PSFex method and calibrated by comparing with a real dataset: CFHT Stripe82 survey (CS82). We will show some preliminary results on weak lensing mass maps and galaxy-galaxy lensing.

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Sinha

Accurate Modeling of Galaxy Clustering on Small Scales: Testing the Standard ΛCDM + Halo Model

Presenter: Manodeep Sinha, Swinburne University of Technology
Additional Authors: Andreas Berlind, Cameron McBride, Roman Scoccimarro, Ben Wibking, Jennifer Piscionere, QingQing Mao

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         The large-scale distribution of galaxies can be explained fairly simply by assuming i) all galaxies are hosted by halos and ii) a cosmological model. This simple framework, called the `halo-model', has been remarkably successful at reproducing the large-scale clustering of galaxies observed in various galaxy redshift surveys. However, none of these studies have truly tested the `halo-model' by carefully modeling the systematics. We present the results from a fully-numerical, accurate `halo-model' framework and show that the theory can not simultaneously reproduce the galaxy projected correlation function and the group multiplicity function in the SDSS main samples. In particular, the bright galaxy sample shows significant tension with theory. We discuss the implications of our findings, as well as how to constrain different aspects of galaxy formation by simultaneously fitting multiple statistics.

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Sonnenfeld

A Strong Lensing View of Dark Matter Halos

Presenter: Alessandro Sonnenfeld, Kavli IPMU
Additional Authors:

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         Strong gravitational lensing is a very powerful tool for measuring galaxy masses at cosmological distances and provides a unique opportunity for probing the dark matter distribution in the most massive galaxies. We analysed a sample of 80 early-type galaxy strong lenses covering the redshift range 0.1 < z < 0.8. Using a Bayesian hierarchical inference approach we constrained the average properties of the distribution of dark matter masses across the population of massive galaxies. We find an anticorrelation between galaxy size and dark matter mass: at fixed stellar mass, the most compact systems appear to have a smaller amount of dark matter, in projection, within the inner 5 kpc. This result is consistent with a scenario in which central galaxies in more massive halos experience more mergers relative to their less massive halos counterparts.

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Tejos

The Statistical Connection Between HI & Galaxies on Mpc Scales

Presenter: Nicolas Tejos, UC Santa Cruz
Additional Authors:

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         I will present observational results on the large-scale connection between the intergalactic medium (IGM) and galaxies at z<1, using one of the largest samples of neutral hydrogen (HI) absorption lines and galaxies in the same volume obtained from deep spectroscopic galaxy surveys (VLT/VIMOS, Gemini/GMOS, Keck/DEIMOS) around QSOs having high resolution UV spectroscopy (HST/COS, HST/FOS). By comparing the HI-galaxy two-point cross-correlation with both the galaxy-galaxy and the HI-HI two-point auto-correlations, as a function of different gas/galaxy properties, we can constraint the overall statistical relationship between the IGM and galaxies on Mpc scales. I will also present results from two complementary studies aimed to characterize the properties of neutral hydrogen in: (i) galaxy voids and, (ii) filaments connecting galaxy clusters.

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Tenneti

Intrinsic Alignments of Galaxies in the MassiveBlack-II Hydrodynamic (MBII) & Dark Matter-Only (DMO) Simulations

Presenter: Ananth Tenneti, Carnegie Mellon University
Additional Authors:



         The intrinsic alignment of galaxies with the large-scale density field is an important astrophysical contaminant in upcoming weak lensing surveys. I will present a comparison of the galaxy shapes and intrinsic alignments in the MassiveBlack-II cosmological hydrodynamic simulation (MBII) that includes stellar and AGN feedback in a volume of (100h-1Mpc)3 and anidentical dark matter-only (DMO) simulation. Understanding the impact of baryonic physics on galaxy shapes should prove useful for creating mock galaxy catalogues based on DMO simulations that mimic intrinsic alignments in hydrodynamic simulations. The dark matter subhalos are typically rounder in MBII, and the shapes of stellar matter in low mass galaxies are more misaligned with the shapes of dark matter of the corresponding subhalos in the DMO simulation. At z=0.06, the fractional difference in the mean misalignment angle between MBII and DMO simulations varies from ~28% - 12% in the mass range 1010.8 - 6.0 × 1014h-1M. Finally, we find that the stellar-dark matter misalignment suppresses the ellipticity-direction (ED) correlation of galaxies in comparison to that of dark matter halos. In the projected shape-density correlation (ωδ+), higher mean ellipticities of the stellar component reduce this effect, but differences of order 30-40% remain on scales >1Mpc. I will also discuss the intrinsic alignments of elliptical and disk galaxies in MassiveBlack-II and Illustris simulations. Despite significant differences in the treatments of hydrodynamics and baryonic physics in the two simulations, we find that the correlation functions scale similarly with transverse separation. In scales above ~0.1h-1Mpc, the intrinsic alignment two-point correlation functions for disk galaxies in both simulations are consistent with a null detection, unlike those for ellipticals.

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Tojeiro

Measuring Redshift-Space Distortions on Large-Scales

Presenter: Rita Tojeiro, St Andrews
Additional Authors:

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         Redshift-space distortions have grown to be one of the most powerful tools in cosmology, allowing us to directly test the theory of gravity at very large scales. Such measurements are limited by our ability to model structure growth and galaxy behaviour on intermediate-to-small scales: both are difficult from computational and theoretical perspectives. In this talk I will present an alternative approach: by selecting a population of galaxies for which the bias evolution is known or easily modelled, we can measure the rate of growth of structure from redshift-space distortions using mostly large-scales. I will show an application to BOSS DR9 data using passively evolving galaxies, and recent progress on this technique using BOSS + eBOSS data and a more flexible bias model.

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Tojeiro - Poster

Observational Proxies of Halo Formation Time

Presenter: Rita Tojeiro, St Andrews
Additional Authors: Lizzie Eardley

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         Standard models assume that halos of the same mass, on average, host the same galaxies. However, there is reason to believe `assembly bias' exists -- this term refers to the expectation that galaxy properties are correlated with other properties of their host halo, not just the mass. In particular, it is possible that halos of fixed mass, but with different formation times cluster differently and host different populations of galaxies.
Observational studies of assembly bias have shown mixed results, with some studies claiming detection and others finding no evidence of assembly bias. A significant difficulty with detecting this form of halo assembly bias observationally is the measurement of halo formation times. As dark matter halos are not directly observable we must use observable galaxy measurements to infer halo formation times. This poster focuses on a precursor to the detection of assembly bias in galaxy surveys -- How can we best estimate the formation time of a halo based on the observable properties of its galaxies, and how reliable are these estimates?

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Tyler

Evolution of the SFR-Density Relation in Clusters From 0.2 < Z < 1.5

Presenter: Krystal Tyler, University of Missouri - Kansas City
Additional Authors: Mark Brodwin, Gillen Brown, Bandon Decker, & the SPT Collaboration



         Galaxy clusters, across all redshifts, can tell us much about the evolution of galaxies. In the local universe, galaxy interactions with the hot intracluster gas can suppress or even completely quench star formation in infalling galaxies. At higher redshifts, however, this trend of lower star formation rates with higher galaxy densities is weaker and, at z > 1, possibly begins to reverse. Using the Herschel space telescope to probe galaxy star formation rates in a sample of ~100 clusters from 0.2 < z < 1.5 from the South Pole Telescope's 2500-square-degree Sunyaev-Zel'dovich survey, we find (1) star formation in galaxies increases with increasing redshift at all cluster-centric radii and (2) evidence of a reversal of the star formation-density relation at z > 1. These results, along with evidence of increasing merger and AGN activity at higher redshifts, support the idea that mergers occur frequently in younger clusters, enhancing the amount of star formation in member galaxies and aiding in the buildup of the massive, passively-evolving elliptical galaxies that dominate the membership of local clusters.

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van-Daalen

Constraining Galaxy Formation Through Clustering

Presenter: Marcel van Daalen, UC Berkeley/LBL
Additional Authors: Bruno Henriques, Raul Angulo, Simon White

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         I will introduce a method that can be used to estimate the projected two-point correlation function of galaxies in a large semi-analytic simulation to better than ~10% using only a very small subsample of the subhalo merger trees. This allows measured correlations to be used as constraints in a Monte Carlo Markov Chain exploration of the astrophysical and cosmological parameter space. An important part of our scheme is an analytic profile which captures the simulated satellite distribution extremely well out to several halo virial radii. This is essential to reproduce the correlation properties of the full simulation at intermediate separations. Our methods allow multi-epoch data on galaxy clustering and abundance to be used as joint constraints on galaxy formation.

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van den Bosch

Can We Use Small-Scale Clustering to Constrain Cosmology?

Presenter: Frank van den Bosch, Yale University
Additional Authors: Andrew Hearing, Andrew Zentner, Shany Danieli

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         Large astronomical surveys such as the SDSS, DEEP2, and COSMOS surveys have proved revolutionary in informing theories of galaxy evolution, and testing our cosmological paradigm. In the next decade or so a number of large galaxy surveys, such as DES, eBOSS, DESI, LSST, EUCLID and WFIRST will provide us an unprecedented wealth of data. In order to optimize the scientific impact of these huge investments, it is prudent that galaxy clustering in both existing and forthcoming surveys be interpreted in an unbiased and maximally informative manner. This entire program faces a severe challenge in the form of galaxy assembly bias. I discuss a few of these challenges in detail, and discuss how they impede our ability to use small-scale clustering to constrain cosmology.

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van der Burg

The Distribution of Stellar Mass in the Most Massive Haloes Since Z=1

Presenter: Remco van der Burg, CEA Saclay, France
Additional Authors: Henk Hoekstra, Adam Muzzin, Cristóbal Sifón, Michael Balogh, Sean McGee, Monique Arnaud, Gabriel Pratt, Hervé Aussel

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         Measurements on the radial distribution of galaxies in clusters show how galaxies trace the underlying dark matter distribution, and provide constraints on the physics related to their evolution in these environments. I will present measurements of the spatial distribution of stellar mass in satellite galaxies of 10 rich clusters around redshift z~1 from the GCLASS survey, and compare this to the stellar mass distribution of their descendant population at redshift z~0.15 (vdBurg+15). Since the two samples are matched in halo mass to be progenitors/descendants, we can compare their stellar mass distributions directly to learn how the stellar mass content assembles in these clusters. This suggests that the central parts (R<400 kpc) of the stellar mass distributions of satellites in local galaxy clusters are already in place at z~1, and contain sufficient excess material for further BCG growth. Evolving towards z=0, clusters appear to assemble their stellar mass primarily onto the outskirts, making them grow in an inside-out fashion. I will also present new results of an extension of this study, namely a measurement of the galaxy distribution in a representative sample of Planck-selected clusters at intermediate redshift of 0.5 < z < 0.7.

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Wechsler

Modeling the Galaxy-Halo Connection for Surveys

Presenter: Risa Wechsler, Stanford University
Additional Authors:



         I will discuss latest techniques to model the galaxy-halo connection, including flexible and color dependent abundance matching techniques, and applications to modeling the largest galaxy surveys.

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Wetzel

The Latte Project: The Milky Way on FIRE

Presenter: Andrew Wetzel, Caltech & Carnegie Observatories
Additional Authors:

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         I will present a new suite of cosmological zoom-in hydrodynamic simulations that model the full formation history of a Milky Way-like galaxy at parsec-scale resolution with the Feedback in Realistic Environments (FIRE) model for star formation, stellar evolution, and stellar feedback. These simulations self-consistently resolve the satellite dwarf galaxy population the forms around the host Milky Way-like galaxy, including the relevant baryonic physics to predict their internal structure and stellar populations. I will discuss first results from this ultra-high-resolution simulation suite, emphasizing the impact of stellar feedback and environment on low-mass subhalos and their connection to dwarf galaxies.

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Wu

Star Formation History From Cosmic Far-Infrared Background

Presenter: Hao-Yi Wu, California Institute of Technology
Additional Authors: Olivier Dore, Romain Teyssier

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         Cosmic far-infrared background originates from unresolved, high-redshift dusty star-forming galaxies and carries the information of star formation rate (SFR) across cosmic time. I will present constraints on the SFR-halo mass relation, SFR history, and dust properties, using the far-infrared background data from Planck and Herschel, as well as resolved far-infrared galaxies. I will compare these results with SFR from optical and ultraviolet observations and discuss the implications for stellar feedback processes.

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Xu

Conditional Color-Magnitude Distribution of Galaxies From Color/Luminosity Dependent Galaxy Clustering

Presenter: Haojie Xu, University of Utah
Additional Authors: Zheng Zheng, Hong Guo, Idit Zehavi, and David Weinberg

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         The color-luminosity distribution of the overall galaxy population shows ordered patterns (e.g., blue cloud, green valley, and red sequence). Linking galaxy color and luminosity with dark matter haloes can help infer the important information about galaxy formation and evolution encoded in such a distribution. We develop a global parameterization of the galaxy color-magnitude distribution as a function of halo mass, status of central and satellite galaxies, and “blue” and “red” populations of galaxies. With such a conditional color-magnitude distribution (CCMD) parameterization, we can model the abundances (space densities) and the clustering (projected two-point correlation functions) of all galaxy samples defined in fine bins of color and luminosity simultaneously. We apply the method to model galaxies in SDSS DR7, spanning nearly 2 orders of magnitude in luminosity (0.1-10L*) and almost the whole range in color, and infer the CCMD of SDSS galaxies. We present the main CCMD modeling results and discuss the implications.

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Yang

The Real Space Clustering of Galaxies

Presenter: Xiaohu Yang, Shanghai Jiao Tong University
Additional Authors: Feng Shi, et al.

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         We make use of the galaxy groups and thus constructed mass density field to correct for the redshift distortion effect of galaxies in the Sloan Digital Sky Survey Data Release 7 (SDSS DR7). Detailed clustering analyses using mock galaxy and group catalogues shows that our method can reliably correct for the redshift distortion effects. By applying the method to the SDSS DR7 observation, we constructed a {statistically} real space galaxy catalogue containing 469332 galaxies within redshift range 0.01 < z < 0.14 in the Northern Galactic Cap of SDSS DR7. We find that the famous Sloan Great Wall, the largest known structure in the Universe, is weakened in real space, indicating that filamentary structures in redshift space may be significantly enhanced due to the Kaiser effect. We measured the two point correlation functions (2PCF) in both real and redshift spaces for galaxies in different absolute magnitude bins. The differences between them clearly demonstrated the Kaiser effect which enhances the redshift space 2PCF by ~25% on large scales and FOG effect which suppresses the 2PCF by ~150% on small scales. In addition, using the two-dimensional 2PCFs of galaxies in real space we demonstrated the ability of using its isotropy requirement to constrain cosmological parameters.

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Young

Density Slope Oscillations in the Central Regions of Galaxy & Cluster-Sized Systems

Presenter: Anthony Young, University of Minnesota
Additional Authors: Liliya L. R. Williams, Jens Hjorth

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         One usually thinks of a radial density profile as having a monotonically changing logarithmic slope, such as in NFW or Einasto profiles. However, in two different classes of commonly used systems, this is often not the case. These classes exhibit non-monotonic changes in their density profile slopes which we call oscillations for short. We analyze these two unrelated classes separately. Class 1 consists of systems that have density oscillations and that are defined through their distribution function f(E), or differential energy distribution N(E), such as isothermal spheres, King profiles, or DARKexp, a theoretically derived model for relaxed collisionless systems. Systems defined through f(E) or N(E) generally have density slope oscillations. Class 1 system oscillations can be found at small, intermediate, or large radii but we focus on a limited set of Class 1 systems that have oscillations in the central regions. We show that the shape of their N(E) can roughly predict the amplitude of oscillations. Class 2 systems which are a product of dynamical evolution, consist of observed and simulated galaxies and clusters, and pure dark matter halos. Oscillations in the density profile slope seem pervasive in the central regions of Class 2 systems. We argue that in these systems, slope oscillations are an indication that a system is not fully relaxed. We show that these oscillations can be reproduced by small modifications to N(E) of DARKexp. These affect a small fraction of systems' mass and are confined to the halo central regions. The size of these modifications serves as a potential diagnostic for quantifying how far a system is from being relaxed.

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Zarrouk - Poster

Modeling QSO Infall Velocity Distribution with N-Body Simulation for eBOSS RSD Analysis

Presenter: Pauline Zarrouk, CEA-Saclay
Additional Authors: E. Burtin

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         The eBOSS multi-object spectrograph has undertaken a survey of Quasars in the redshift range 0.9<z<2.2. It will measure the growth rate of structure from the Redshift Space Distortions of the 2-point correlation function and allow for a test of general relativity modifications and dark energy scenarios. To perform this measurement, special care should be given to the RSD model. The most popular model is the Gaussian Streaming model which convolute a Gaussian probability distribution for peculiar infall velocities with the real space correlation function. In this poster, we will present the applicability of such a model for the QSO tracer using Convolution Lagrangian Perturbation Theory. Moreover, using N-Body simulations, the Halo occupancy distribution of QSO in dark matter halos can be investigated and we will examine at which scale this model is valid in the redshift range of eBOSS. Furthermore, the true peculiar infall velocity distribution displays exponential tails at odds with the Gaussian streaming model. We will present an attempt to parametrize the full infall velocity distribution from N-body simulations. Then using a specific streaming model, we will quantify the difference with the Gaussian Streaming Model.

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Zentner

The Challenge & Opportunity of Assembly Bias

Presenter: Andrew Zentner, University of Pittsburgh
Additional Authors:



         Assembly bias presents a challenge to the analysis of galaxy clustering and lensing statistics. It is possible that assembly bias can cause one to infer the wrong halo-galaxy relationship from observational data and/or an incorrect cosmological model. Further, it is not at all unreasonable that assembly bias could be present at some level in the real universe. In this talk, I will summarize the challenges posed by the effect of assembly bias on interpretations of galaxy clustering. This challenge also presents an exciting opportunity: the possibility of inferring a richer galaxy-halo relationship than can be accommodated in previous model. I will discuss strategies for mitigating assembly bias, particularly through redefining our concept of a "halo." Lastly, I will discuss models of assembly bias and their use in the interpretation of galaxy clustering and lensing statistics. These mitigation and modeling strategies are early forays into developing models that are robust to assembly bias, suitable for analyzing large data sets, and capable of providing further information about the relationships between galaxies and their dark matter halos.

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Zheng

Modeling Small- & Intermediate-Scale Redshift-Space Galaxy Clustering

Presenter: Zheng Zheng, University of Utah
Additional Authors: Hong Guo, Idit Zehavi

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         With the increasing precision of galaxy clustering measurements from ongoing and forthcoming large galaxy surveys, accurate models are required to interpret the redshift-space data and extract relevant information. I will first present a method based on high-resolution N-body simulations to accurately and efficiently model the projected and redshift-space galaxy two-point correlation functions, which enables an efficient exploration of the parameter space. I then talk about the applications of such a method to model the small-to-intermediate scale redshift-space clustering of SDSS and BOSS galaxies and discuss the implications of the inferred galaxy-halo relation and galaxy velocity bias.

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Zu

Constrain Galaxy Formation Physics from Large-Scale Structure Measurements & Weak Lensing

Presenter: Ying Zu, Carnegie Mellon University
Additional Authors:

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         Galaxy formation is one of the most intractable phenomena in astrophysics due to the enormous complexity and diversity in the assembly histories of individual galaxies. Modern galaxy surveys provide a unique avenue to understanding galaxy formation physics in a statistical context, through various large-scale structure measurements and the weak gravitational lensing of large numbers of galaxies. I will introduce a new probabilistic framework, called the "iHOD" model, which enables strong constraints on the stellar-to-halo mass relation and the underlying driver for the quenching of star formation in galaxies probed by the Sloan Digital Sky Survey. I will also highlight the advantages of the iHOD model by comparing it with traditional HOD and SHAM methods, as well as an age-matching model in which galaxy quenching depends on halo age at fixed stellar mass. Lastly I will discuss the prospect of extending the iHOD framework to constrain the curious effect of"galaxy assembly bias" using marked statistics.

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