The coordinated growth of stars, haloes and largescale structure since z1

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The coordinated growth of stars, haloes and
large-scale structure since z1

• Michael Balogh
• Department of Physics and Astronomy
• University of Waterloo

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Outline

• What determines a galaxys properties?
• Stellar mass
• Cosmic time
• Environment
• Theoretical expectations
• Dark matter halo mass function and growth
  history
• Gas accretion and feedback
• Local processes (e.g. merging, stripping etc.)

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Colour distribution

• Bimodality in colour distribution used to
  simplify analysis
• Very useful, but hides many details

• Millennium GC Driver et al. (2006)

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Stellar mass

• Characteristic stellar mass 3x1010 MSun
• Star formation today occurs in low-mass galaxies

Kauffmann et al. (2003)
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Cosmic Time

• buildup of mass on the red-sequence occurs with
  the most massive galaxies first
• decrease in the quenching stellar mass with
  redshift

Cimatti et al. (2006)
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Environment

• Nearby cluster galaxies differ in their
• SFR
• Colour
• Stellar mass function
• HI gas
• Morphology

Lewis et al. (2001)

• Lots of evidence that trends are independent of
  stellar mass. Also morphology (Christlein
  Zabludoff 2005)
• All trends observed in clusters appear to extend
  to groups, field environments

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The halo model

• Formation history is tightly coupled to dark
  matter halo mass small haloes form first
• Dark matter mass function depends on environment
• Mass accretion rate depends on environment
  (Maulbetsch et al. 2006).
• Could give rise to observed trends?

www.nbody.net
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The halo model
Maulbetsch et al. (2006)

• Formation history is tightly coupled to dark
  matter halo mass small haloes form first
• Dark matter mass function depends on environment
• Mass accretion rate depends on environment
  (Maulbetsch et al. 2006).
• Could give rise to observed trends?

Halo mass
Cosmic Time
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The halo model
Maulbetsch et al. (2006)

• Formation history is tightly coupled to dark
  matter halo mass small haloes form first
• Dark matter mass function depends on environment
• Mass accretion rate depends on environment
  (Maulbetsch et al. 2006).
• Could give rise to observed trends?

Halo mass
Cosmic Time
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Gas Accretion

• Halo mass scale constant with time, 2x1011 MSun.
• Separates hot and cold accretion (e.g. White
  Frenk 1991)
• AGN feedback helps eliminate bright blue galaxies
  (Springel et al. 2005 Croton et al. 2006 Bower
  et al. 2006)

Dekel Birnboim 2006
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Environment predictions?

• Galaxy colour depends primarily on halo mass.
  Satellites are effectively quenched.

• Low stellar-mass, red galaxies are predicted to
  be in groups, above the critical mass limit
• Ignore (details of) ram pressure stripping,
  harassment etc.
• Know these occur in rich clusters

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My summary from Ringberg 2005

• When feedback parameters are tuned to reproduce
  the field luminosity function and colour
  distribution, what will we find as a function of
  environment?
• General trends will be reproduced. But will it
  be for the right reasons?
• Any differences in detail will they signify
  nurture processes? Or just that feedback
  parameters need further tuning?

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Halo mass dependence
R luminosity

• Method 1 can try to select groups and clusters
  from the observations in a way that is similar to
  N-body halo-finders.
• Late-type fraction depends most strongly on halo
  mass

Weinmann et al. 2005
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Halo mass dependence

• Faint, satellite galaxies are blue
• Models too efficient at shutting off gas supply?

Weinmann et al. 2006
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Local environment

• Method 2 Use an observationally-motivated,
  continuous measurement of environment
• Red fraction is a continuous function of local
  density and stellar mass

Baldry et al. (astro-ph/0607648 )
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Universal relation

• Red fraction appears to depend on a simple linear
  combination of stellar mass and density
• Reflects the fact that stellar mass and density
  are correlated

Baldry et al. (astro-ph/0607648 )
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Theoretical predictions

• Croton et al. (2006) models, based on the
  Millennium simulation

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Theoretical predictions

• Croton et al. (2006) models, based on the
  Millennium simulation

Data
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Theoretical predictions

• Bower et al. (2006) models, based on the
  Millennium simulation

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Theoretical predictions

• Bower et al. (2006) models, based on the
  Millennium simulation

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Theoretical predictions

• Croton et al. (2005)

Bower et al. (2006)
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Theoretical predictions

• Both models get general trends right
• Both models predict too many red galaxies in the
  densest region
• Central galaxies in Croton model are too
  frequently blue

Croton et al. (2005)
Bower et al. (2006)
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Isolated galaxies

• The 50 most isolated, nearby galaxies
• Certain to be central useful comparison to
  models.
• Continuous sequence?

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Increasing stellar mass
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Environment Redshift evolution

• Strong evolution out to z0.5
• EDiSCs (also MORPHS, CNOC, PISCES, many others)
• Production of S0 galaxies?

• Environmental effects visible at z1
• DEEP2, (also CFHTLS, VVDS)

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EDiSCs

• At 0ltzlt1, passive fraction correlates well with
  the fraction of galaxies in groups at zgt2.

• At z0, the cluster environment further
  suppresses star formation.

Poggianti et al. (2006)
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Poggianti

• the fraction of passive galaxies observed in z
  0.40.8 clusters of a given /mass is comparable
  with the fraction of its galaxies (or its mass)
  that was already in dense environments (i.e.,
  groups) at z 2.5.
• the observed fraction of passive galaxies in
  systems with gt 500 km s-1 at z 0 is
  compatible with the fraction of galaxies that
  have resided in a cluster (Msys gt 1014 M ) for at
  least 3 Gyr and therefore have had the time to
  have their star formation switched off
• According to this discussion, while the passive
  galaxy populations of the distant clusters are
  predominantly composed of primordial passive
  galaxies, the populations of lower redshift
  clusters are dominated by quenched galaxies.

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Environments at z1

• d

DEEP2 (Cooper et al. 2006)
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Environments at z1

• DEEP2 (Cooper et al. 2006)
• 0.75ltzlt1.35

SDSS
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Environments at z1
SDSS (Blanton et al. 2005)

• DEEP2 (Cooper et al. 2006)

• At z1, the luminosity of blue galaxies
  correlates with environment. i.e. brighter blue
  galaxies are in denser environment.
• These galaxies presumably evolve into the bright,
  red galaxies in dense environments today

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Environments at z1

• At least 3 red galaxies in low density
  environments at all z
• Fewer galaxies above critical mass at higher
  redshift? i.e. is this just evolving mass
  function?

DEEP2 (Cooper et al. 2006)
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Summary

• Environment in one way or another is as
  important as stellar (halo?) mass
• Hypothesis that cooling is shut off in haloes
  above a critical mass seems to work.
• Efficiency and timescale (and therefore physical
  mechanism) still uncertain
• Need to move beyond bimodality to find out how
  the transformation is occurring.