Overview of Galaxy Modelling tools at the MPIA

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Overview of Galaxy Modelling tools at the MPIA

• rachel somerville

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Tools for Modelling Galaxy Formation Evolution

• Halo Occupation Distribution (HOD) models
• semi-analytic models (SAMs)
• numerical N-body simulations
• dissipationless (gravity only)
• gravity hydrodynamics

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Halo Occupation Distribution (HOD) models

• empirical parametric or non-parametric mapping
  between dark matter halo (sub-halo) distribution
  and galaxy distribution (i.e. MDM--gt L or m)
• obtained by matching observed galaxy LF (or MF)
  and clustering as function of galaxy luminosity
  (mass)
• can be done as function of galaxy type, color, etc

Frank van den Bosch, rss, Ramin Skibba, Marcello
Cacciato, Surhud More, Ben Moster
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Halo Occupation Distribution (HOD) models

• advantages
• can be used to exactly reproduce distributions of
  galaxy properties, e.g. for mock catalogs
• provides insights into which galaxies occupy
  which halos, useful for diagnosing more
  physical models
• disadvantages
• non-uniqueness
• predictive power weak
• provides only indirect insight into physical
  processes

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semi-analytic models

• use merger trees to describe the mass assembly
  history of dark matter halos (semi-analytic or
  N-body)
• simple (but physically motivated) recipes used to
  describe processes like merging, gas cooling,
  star formation, stellar feedback, AGN feedback,
  chemical evolution, stellar populations, dust, etc

rss, Fabio Fontanot, Christian Maulbetsch, Xi
Kang (Eric Bell, Ros Skelton, Ben Moster)
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semi-analytic models

• advantages
• computationally efficient and flexible
• can incorporate many physical effects in at least
  a schematic manner (e.g. dust, AGN feedback)
• good for global, self-consistent bookkeeping
• disadvantages
• treatment of physical processes is only
  approximate
• little/no information provided about spatial
  location of galaxies, or about their internal
  structure appearance

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Numerical N-body/hydro simulations

• solve equations of motion and thermo/hydrodynamics
  for dark matter, gas, and stars, using particles
  or grid cells
• Eulerian (grid based e.g. ENZO, FLASH) vs.
  Smoothed Particle Hydrodynamics (SPH)
  (Lagrangian e.g. GADGET, GASOLINE)
• initial conditions cosmological, isolated
  galaxies, galaxy mergers

Andrea Maccio, Christian Maulbetsch, Xi Kang,
Hsiang-Hsu Wang, Kelly Foyle, (Ben Moster)
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Numerical N-body/hydro simulations

• advantages
• exact, detailed treatment of physical processes
• predictions for spatial distribution and physical
  structure of DM halos, galaxies, etc.
• disadvantages
• computationally expensive, so unfeasible to
  explore large parameter space or to simulate
  large volumes at high resolution
• more difficult to incorporate additional physical
  processes (e.g. BH growth, AGN feedback)
• currently, even best simulations do poorly at
  matching fundamental galaxy observations (e.g.
  overcooling problem, angular momentum problem)

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halo-by-halo N-bodyhydro simulations

• run a large (L100 Mpc) dissipationless N-body
  simulations extract merger trees
• select halos spanning a range of final mass and
  assembly histories
• re-simulate only the co-moving volume
  corresponding to a bit more than the comoving
  virial radius of the halo of interest, at much
  higher resolution (DM only, DMhydroSFFB, etc)
• test calibrate semi-analytic recipes for
  cooling, SF stellar feedback, etc.
• experiment with different recipes for SN feedback
  and AGN feedback

Maulbetsch, rss, Fontanot, Maccio with
Naab/Burkert group
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hybrid SAM/hydro simulations

• extract high resolution merger tree from N-body
  simulation
• for main branch, simulate smooth accretion
  and cooling with numerical hydro
• predict properties of satellites with SAM (e.g.,
  mdisk, rdisk, mbulge, rbulge, fgas, etc)
• drop in the satellites and simulate the merger
  with N-bodyhydro
• goals
• spiral (MW-like) galaxies formation of stellar
  halo, streams, thick disk
• appearance and structure of mergers and merger
  remnants kinematics
• starbursts and BH growth in mergers

Moster, rss, Maccio
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Summary of Projects

• halo-by-halo N-bodyhydro simulations
  (Maulbetsch, rss, Fontanot, Maccio w/ Naab/
  Burkert group)
• hybrid SAM/hydro project (Moster, rss, Maccio)
• statistics and implications of mergers (Skelton,
  rss, Bell, Maulbetsch, Moster)
• semi-analytic models incorporating BH growth and
  AGN feedback (comparison with high-z multi-l
  surveys, high-z QSO predictions, etc) (rss,
  Fontanot, Bell, SkeltonSTAGES/GEMS teams)
• star formation and stellar feedback in disk
  galaxies (Wang, rss, van den Bosch, Walter, w/
  Klessen, Tasker, Bryan, MacLow)
• Milky Way satellites (Maccio, rss, Fontanot,
  Kang)
• modelling dust in galaxies (Fontanot, rss)

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Self-consistent model for the co-evolution of
galaxies, black holes, and AGN

• top-level halos start with a 100 Msun seed BH
• mergers trigger bursts of star formation and
  accretion onto BH efficiency and timescale
  parameterized based on hydrodynamical merger
  simulations (?, B/T, Vc, fg, z Cox et al.,
  Robertson et al.)
• BH merge when their galaxies merge mass is
  conserved
• BH accrete at Eddington until they reach
  critical mass, then enter blowout (power-law
  decline) phase and switch off
• energy released by accretion drives a wind
• radio mode AGN heating can counteract gas
  cooling in halos with a hydrostatic hot halo

rss, Hopkins, Hernquist, Cox, Robertson et al.
2008
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radio mode heating

• assume continuous Bondi-like accretion
• fixed fraction ? of released energy in kinetic
  form (jet)

10-3 LEdd
LEdd MBH0.6
Allen et al. clusters Best et al. study w/
factor 6 boost (Binney et al. 2007)
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hot vs. cold flows

• when rcoolltrff, gas is shock heated to virial
  temperature then cools in a cooling flow
• when rcoolgtrff , gas never shock heats, falls in
  cold
• halos with primarily cold vs. hot flows separated
  by a critical mass of few x 1011-1012 Msun (e.g.
  Birnboim Dekel 2003 Keres et al. 2004)
• heating by radio jets may only be effective when
  a quasi-static hot gas halo is present (i.e. in
  large mass halos Cattaneo et al. 2006)

Kravtsov et al.
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momentum-driven windsgalactic outflows
from hydrodynamic simulations of merging galaxies
(Springel, di Matteo Hernquist Hopkins et al.)
rss, Hopkins, Hernquist, Robertson, Cox et al.
2007
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stellar mass function by type
rss et al. 2007
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massive galaxies are quenched
simulation
SDSS data
active
specific star formation rate
passive
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massive galaxies are quenched

• the transition from
• active to quenched
• galaxies occurs at
• the right stellar
• mass scale
• 3 x 1010 Msun
• (Kauffmann et al.),
• but is too sharp
• over-quenching
• in large-mass halos

fraction of quenched galaxies
log stellar mass
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Hydrodynamic simulations of galaxy mergers
including black hole growth and feedback

• self-regulated BH growth, leaving remnants on
  MBH-? relation (di Matteo et al. 2004)
• AGN-driven wind removes residual cold gas at the
  end of the merger, leading to lower SFR and
  redder colors in the spheroidal remnant (Springel
  et al. 2004)
• characteristic AGN lightcurve

di Matteo, Springel Hernquist 2005
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The Black Hole Fundamental Plane

• BH mass correlates with multiple galaxy
  properties (?, Lbulge, mbulge, Mdyn, Re, ns)
• significant correlation of residuals with third
  variable, e.g. Re or mbulge
• indication of an underlying Fundamental Plane

Marconi Hunt 2004 Hopkins et al. 2007
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Origin of FP tilt for early type galaxies?

• gas-rich mergers suffer more dissipation, leading
  to more compact remnants

Hopkins et al. 2007 Robertson et al. 2006 Cox
Dekel 2006 Naab Burkert
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Origin of Black Hole Fundamental Plane?

• condition for self-regulation of accretion
  sufficient injection of momentum within a
  dynamical time near the sphere of influence of
  the BH
• deeper potential well requires a more massive BH
  to shut off accretion

Hopkins et al. 2007
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• strong prediction evolution of mBH/msph with z
  relationship with fgas and galaxy structural
  properties

Hopkins et al. 2007, astro-ph/0701351
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QSO luminosity density

• model 1 MBH(crit) always given by Haering Rix
  (no evolution)
• model 2 MBH(crit) set by BHFP (m, ?)
• model 2b ditto, but existing BHs zeroed at
  beginning of merger

rss, Hopkins et al. 2008
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who am i Head of GC Theory Group

• expertise
• - semi-analytic modeling
• - large-scale structure
• cosmology
• - N-body hydro-dynamics
• consumer
• - member of GOODS, GEMS, UDF,
• DEEP/AEGIS, STAGES
• programming c, idl
• former Archive Scientist at
• MAST (Multi-mission Archive
• at Space Telescope) and dabbler
• in the Virtual Observatory (VO)

hidden talents -- swing dancing (beginner)
cooking (pretty good) piano (rusty) nearly
useless languages (hebrew,hindi, japanese...)