Feedback, Models and the effect of Environment

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Feedback, Models and the effect of Environment

• Richard Bower
• the GALFORM team
• Andrew Benson, Andreea Font, Ian McCarthy, Rowena
  Malbon, John Helly, Carlos Frenk, Carlton Baugh,
  Shaun Cole, Cedric Lacey.

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What I want to say!

• Old stuff!
• Quick overview of the new Durham models - AGN
  feedback and what it does for you.

• New stuff!
• Galaxy Ecology - modeling how galaxies interact
  with their environment
• The flip-side of galaxy formation - the thermal
  history of the IGM/ICM

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The three problems of galaxy formation

• The bright end of the luminosity function
• What sets the break in the galaxy luminosity
  function?
• The cooling flow problem
• Why dont cooling flows result in bright blue
  galaxies at the centres of clusters?
• The hierarchy problem
• Why are the brightest galaxies old and red?
• These problems are closely interconnected do AGN
  provide the solution?

4. Only 10 of the baryons form into stars!!!
Where are the other baryons? what are their
properties?
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What coolingfeedback need to do!
feedback has successfully depressed galaxy
formation in small haloes
dark matter mass function (fixed M/L)
NB exacerbated by the high value of WMAP Ob
but cooling is now too effective in high mass
haloes (there's more gas left over)
The same problem is seen in simulations Balogh
et al., 2001 Springel Hernquist 2003
Benson et al 2003
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AGN the new ingredient
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The Power of AGN

• Comparison of energies
• Total thermal energy of a 1013 Mo halo
  1061 erg
• Accretion energy of a 109 Mo black hole
• 2 x 1062 erg
• It seems unlikely that AGN are unimportant!

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The two forms of AGN feedback
Quasar mode (eg. Granato et al., 2004,
Springel et al 2005)
Radio mode feedback (eg. Croton et al 2006,
Bower et al 2006 Okamoto et al 2007)
Radio
Temperature
X-rays
Shock heating
Uplifting matterial?
Mixed plasma and ICM?
M87 Forman et al 2006 Perseus Fabian et al
2000, 2006
Springel et al 2005
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The two modes of AGN feedback

• Radiatively efficient flows
• normal Shakura-Sunyaev disk
• Geometrically thin
• Heat generated by the flow is radiated
• The disk stays cool and thin

High accretion rate
High power jet is produced by dynamo
instabilities in the frame of the spinning black
hole

• Radiatively inefficient flows
• Geometrically thick
• Heat generated by the flow is trapped and
  advected into the black hole
• The disk becomes hot and thick
• (ADAF Narayan Yi 1995 RIAF Blandford
  Begelman 1999)

Low accretion rate
Large disk scale height leads to magnetic field
being stretched into the black holes space time
(Blandford Znajek 1977, Rees et al 1983, Meier
1999, 2001)
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The AGN feedback loop
AGN fuelling
Cooling
radio mode
Hydrostatic ? tcoolgttfree-fall
Keres et al 2005 Dekel Birnboim 2003 Binney
2004
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The impact of AGN Feedback An Example
With AGN
Without AGN
bulge stars
disk stars
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Present-day Galaxies
No AGN

• Bj and K luminosity functions
• Switching radio feedback off leads to a
  population of very bright galaxies formed in
  cooling flows
• But position of the LF break is set by the
  division between rapid and hydrostatic cooling
  haloes.

Bj band
dust
No dust
No AGN
K-band
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Evolution of the Stellar Mass Function

• The evolution of the stellar mass function from
  Drory et al 2005.
• More recent tests now possible (eg Van Dokkum et
  al 2007, Bundy/Stringer 2008)

z0
AGN model
McClure et al 2006
Integrated SMD agrees with Stark et al 2006
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Evolution of colours

• Evolution of red sequence tracks passive
  evolution
• but the blue sequence also get bluer matches
  the increase in SFR density

Bower et al 2006 De Lucia et al 2006 galaxy
catalogues are public! www.mpa-garching.mpg.de
and www.icc.dur.ac.uk
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Summary (of part I)

• AGN semi-analytic galaxy formation provides a
  frame work for understanding the
  anti-hierarchical universe
• B06 is by no means the only model to use AGN
  eg., Hatton et al 2003, Granato et al 04,
  Croton et al. 06, De Lucia et al 07, Menci et
  al 07, Cattaneo 07, Summerville 08 - but be
  aware of the different flavours.
• The model seems to do reasonably well . (Im
  sure someone will contradict me!)

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Part IIImproving the model
But models that work are boring

1. A better description of environmental processes
2. (Pre-) heating the IGM

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Problems with the standard model
(one of them)

• Satellites are too red. Regardless of halo mass.
• The effect of strangulation is overestimated
• A satellite galaxy orbiting within another halo
  is assume to loose its own hot gas reservoir.
• This is far too simplistic

Weinmann et al 2006 Baldry et al 2006.
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Environmental Physics is not correctly handled
Satellite Galaxies
All Galaxies
All satellites are red!
No blue satellites!
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Environmental Physics is not correctly handled

• Old Strangulation model
• Remove gas reservoir as galaxy orbits larger halo

Larson, Tinsley Caldwell 1980
McCarthy et al an improved model for halo
stripping depends on the orbit of the satellite
and the gas content of the satellite and main
halo. (Actually, Gunn Gotts formulae
re-calibrated for halo gas using numerical
simulations)
Hot gas reservoir

• Is this realistic?
• Mass ratio of haloes
• Gas atmosphere of the main halo

SNe winds quickly exhaust disk gas
Strangulation suffocation starvation
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Controlled SPH and FLASH simulations
McCarthy et al. 2007
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Implementation in GALFORM
- Hot gas modelled with a beta- model / NFW
Satellite velocities are sampled with a 2D
distribution (Benson 2005)
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Environmental Physics is not correctly handled
New Strangulation Physics
Old Strangulation model
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Solving the problem by adjusting the environment
physics

• Dramatic improvement in the environmental
  dependence of satellite properties from reducing
  the effects of starvation.

Font et al 2008
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Problem solved?
There are many more tests of the interaction of
galaxies with their environment - more work is
needed to extract the data and model in
comparable ways (Balogh/Font/McGee/IGM/RGB et al
2008)
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A closer look at the colour distribution of
galaxies
The Field
The Clusters
Too many intermediate colours galaxies, not
enoough blue objects
Too many faint red galaxies
Font, Balogh, McGee et al, in prep.
(Distributions shifted to to agree with
red-sequence colours)
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A closer look at the luminosity function
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What about the ICM?

• The flip-side of galaxy formation

Only 10 of the baryons form into stars!!! -
what about the rest of the baryons???
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X-ray Emission from Groups and Clusters

• L-T relation well known that the self-similar
  relation fails
• AGN standard model just prevents cooling it
  doesnt affect the X-ray luminosity

B06 Model
Data from Horner et al.
Data from Osmond Ponman
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The AGN feedback loop (new version)

• A note for pundits
• This is in-situ heating
• theres no pre-heating
• its going to be expensive, but not prohibitively
  so.

AGN fuelling
Cooling
radio mode Pmin(?Ledd,?Mcool)
Hydrostatic ?
Heating
redistribute halo gas
Based on the excess energy method (Wu et al
1999), plus the hydrostatic criterion
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X-ray Emission from Groups and Clusters

• L-T relation well known that the self-similar
  relation fails
• AGN standard model just prevents cooling
• Revised model, AGN feedback redistributes halo
  gas until the cooling rate drops and AGN power is
  cut off

AGN redistributes halo gas
A huge step forward - Ive been trying to achieve
this for ten years!
Scatter driven by diverse assembly history
Voit Bryan 2001 Bower et al 2008, MN, in press
(astro-ph/0808.2994)
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The baryon content of haloes - where are all
those baryons?
Ejected gas
T (keV)
Hot X-ray emitting gas
Stars and cold gas
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Conclusions what you should remember!

• AGN regulate the formation of the brightest
  galaxies.
• The break in the LF is set by hydrostatic vs
  rapid cooling.
• The model describes the properties of field
  galaxies and their evolution well.
• Cluster galaxies form earlier than field galaxies

• But
• Galaxy ecology is a formidable test
• Improved treatment of ram-pressure stripping of
  halo gas makes a huge improvement
• Font et al 2008
• X-ray emission from groups and clusters
• Over estimated in standard model
• AGN do more than prevent cooling
• Bower et al 2008

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Thank you!
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Evolution of the Stellar Mass Function

• The evolution of the stellar mass function from
  Drory et al 2005.

z0
AGN model
McClure et al 2006
Integrated SMD agrees with Stark et al 2006