Galaxy properties in different environments: Observations

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Galaxy properties in different environments
Observations
Michael Balogh
University of Waterloo, Canada (Look for 3 new
job postings on AAS soon)
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Outline

• Morphology
• Evolution of early and late types
• Colours
• Star formation rates, HI
• EA galaxies

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Galaxy morphology
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Morphology-Density Relation

• Morphological mix correlates best with local
  galaxy density
• Possibly additional effects in innermost regions
  (Whitmore et al. 1995 Dominguez et al. 2001)

Coma cluster
E
S0
Clusters
Spirals
Field
Dressler 1980 Also Oemler 1974 Melnick
Sargent 1977
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Morphology-density evolution
Low redshift
NS0/NE
Number of galaxies
Z0.5
Redshift
Dressler et al. 1997 Couch et al. 1994
1998 Fasano et al. 2000 Wide field HST Treu et
al. 2003
Log surface density
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S to S0 transformation?
Kenney et al. 2003 Vollmer et al. 2004

• Ram pressure stripping of the disk could
  transform a spiral into a S0 (Gunn Gott 1972
  Solanes Salvador-Solé 2001)
• Another possibility gradual decline in SFR due
  to loss of gas halo (Larson, Tinsley Caldwell
  1980 Balogh et al. 2000)
• May lead to anemic or passive spiral galaxies
  (Shiyoa et al. 2002)

Non-SF spiral galaxies from SDSS (Goto et al.
2003) First noted by Poggianti et al. (1999) in
z0.5 clusters
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S to S0 transformation?

• But bulges of S0 galaxies larger than those of
  spirals (Dressler 1980 Christlein Zabludoff
  2004)
• Requires S0 formation preferentially from spirals
  with large bulges (Larson, Tinsley Caldwell
  1980) perhaps due to extended merger history in
  dense regions (Balogh et al. 2002)

Bulge size
Dressler 1980
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Arguments against ram pressure stripping

• 1. S0 galaxies found far from the cluster core
• Galaxies well beyond Rvirial may have already
  been through cluster core (e.g. Balogh et al.
  2000 Mamon et al. 2004 Gill et al. 2004)
• 2. Morphology-density relation holds equally well
  for irregular clusters, centrally-concentrated
  clusters, and groups
• - but may be able to induce bursts strong
  enough to consume the gas (see Mayer et al.
  poster)

Gill et al. 2004
Groups (Postman Geller 1984)
Spiral fraction
Local galaxy density (3d)
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Galaxy colours

• Easier to measure than morphology (lower quality
  data)
• Easier to quantify
• Can be directly related to stellar population
  models

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Early type galaxies
Tight colour-magnitude relation (Faber 1973
Visvanathan Sandage 1977 Terlevich et al. 2001)
E S0
Bower, Lucey Ellis 1992
Kuntschner Davies 1998 (also Poggianti et al.
2001) see also Bernardi et al. 2003 for results
based on SDSS data Field early-types 2-3 Gyr
younger than clusters (Kuntschner et al. 2002)
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Early-type galaxies

• van Dokkum Franx 1996
• M/L evolution consistent with high formation
  redshift

Zform 8 Zform1

• Disappearance of faint red galaxies by z1

Kodama et al. 2004 (also Bell et al. 2003)
De Lucia et al. 2004
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Colour-magnitude relation
CMR for spiral galaxies also observed (e.g.
Chester Roberts 1964 Visvanathan 1981 Tully,
Mould Aaronson 1982) SDSS allows full
distribution to be quantified with high precision
( Baldry et al. 2003 Hogg et al. 2003 Blanton
et al. 2003)
Sloan DSS data
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• Analysis of colours in SDSS data
• Colour distribution in 0.5 mag bins can be fit
  with two Gaussians
• Mean and dispersion of each distribution depends
  strongly on luminosity
• Dispersion includes variation in dust,
  metallicity, SF history, and photometric errors
• Bimodality exists out to z1 (Bell et al. 2004)

Bright
Faint
(u-r)
Baldry et al. 2003
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(No Transcript)
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• Fraction of red galaxies depends strongly on
  density. This is the primary influence of
  environment on the colour distribution.

• Mean colours depend weakly on environment
  transitions between two populations must be rapid
  (or rare at the present day)

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Butcher-Oemler effect

• Concentrated clusters at high redshift have more
  blue galaxies than concentrated clusters at low
  redshift

Butcher Oemler (1984)
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Butcher-Oemler Effect
Margoniner et al. 2000

• Blue fraction depends strongly on luminosity and
  radius
• Great care needs to be taken to evaluate blue
  fraction at same luminosity limit, and within
  same (appropriate) radius.
• Increase in blue fraction is not just restricted
  to clusters (e.g. Lilly et al. 1996)

Blue fraction
Radius (Mpc)
Blue fraction
Blue fraction
Margoniner et al. 2001

• Andreon, Lobo Iovino 2004

Redshift
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• Kodama Bower (2000) model clusters inhibit
  star formation, but recent infall maintains a
  high blue fraction at higher redshift.

• Leads to steeper colour gradients in higher
  redshift clusters

Ellingson et al. (2001)
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Tully-Fisher relation at z1

• Milvang-Jensen et al. 2004

• Spiral galaxies at z1 (both cluster and field)
  are brighter in B than at low redshift
• Z1 cluster spirals brighter at fixed s than
  field spirals (?)
• See poster by Milvang-Jensen et al.

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Star formation and gas
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HI deficiency
Mark I and II imaging of Virgo galaxies
Davies Lewis 1973
VLA imaging of Coma spirals
Bravo-Alfaro et al. 2000
18 nearby clusters Solanes et al. 2001
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Emission lines

• Cluster galaxies of given morphological type show
  less nebular emission than field galaxies
• suggests star formation is suppressed in cluster
  galaxies

Emission line fraction
Dressler, Thompson Shectman 1985 Also Gisler
1978
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Star formation

• Fraction of emission-line galaxies depends
  strongly on environment, on all scales
• Trend holds in groups, field, cluster outskirts
  (Lewis et al. 2002 Gomez et al. 2003)
• Fraction never reaches 100, even at lowest
  densities

Cluster infall regions
Emission line fraction in SDSS and 2dFGRS
(Balogh et al. 2004)
A901/902 supercluster (Gray et al. 2004)
correlation with dark matter density
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Ha distribution
Virgo spirals

• Cluster galaxies often show peculiar distribution
  of Ha emission usually truncated, or globally
  suppressed
• In some cases, star formation is centrally
  enhanced (Moss Whittle 1993 2000)

Ha for Virgo galaxy
Ha for normal galaxy
Koopmann Kenney 2004 also Vogt et al. 2004
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Cluster galaxy evolution
Kodama et al. 2004
z0.3
z0.5
Field
Field
Complete Ha studies Even at z0.5, total SFR in
clusters lower than in surrounding field
Tresse et al. 2002
Couch et al. 2001 Balogh et al. 2002 Fujita et
al. 2003
SDSS/2dFGRS Emission-line galaxies only Ha
distribution does not depend strongly on
environment (Balogh et al. 2004)
OII luminosity functions Lotz et al.
2003 Martin et al. 2000
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Emission lines at z0.5
Dressler et al. 1997
Balogh et al. 1998
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Cluster galaxy evolution
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Cluster galaxy evolution

• Complete Ha based SFR estimates
• Evolution in total SFR per cluster not well
  constrained
• considerable scatter of unknown origin
• systematic uncertainties in mass estimates make
  scaling uncertain

Finn et al. 2003
Finn et al. 2003
Kodama et al. 2004
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Cluster galaxy evolution

• Complete Ha based SFR estimates
• Evolution in total SFR per cluster not well
  constrained
• considerable scatter of unknown origin
• systematic uncertainties in mass estimates make
  scaling uncertain

Finn et al. 2003
Kodama et al. 2004 Finn et al. in prep
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EA galaxies

• Aka ka, ak, PSG, PSB, HDS, e(a)

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Butcher-Oemler effect
SDSS Goto et al. (2003)

• Many of blue galaxies turned out to have
  post-starburst spectra (Dressler Gunn 1992
  Couch Sharples 1987)
• Also evidence for dust-obscured star formation
  from infrared (Fadda et al. 2000 Duc et al.
  2002 Coia et al. 2004)

SDSS EA galaxies
Couch Sharples 1987
Balogh et al. in prep.
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• EA galaxies in Coma may be correlated with
  X-ray emission
• Strong luminosity evolution in EA population
  (Tran et al. 2003)
• Also found in the field (e.g. Zabludoff et al.
  1996 Balogh et al. 1999). But bright, field EA
  galaxies locally may have different origin.

UKIRT imaging
emission
Poggianti et al. 2004
EA
Balogh et al. in prep.
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Consistent interpretation?

• Dense environments predominantly quench star
  formation, probably via a variety of mechanisms
• Butcher-Oemler effect
• Strength of trend in clusters still debatable
• May arise from higher rate of infall of initially
  bluer galaxies
• Galaxy interactions and mergers
• Build larger bulges in dense environments
• Consume available gas in rapid starburst
• Present in all environments, but more so at
  higher densities
• Establish red sequence in clusters at early times

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The future

• Higher redshift clusters (e.g. RCS2, CFHTLS,
  HIROCS)
• HI and Ha distributions at higher redshift
• Galaxy groups, filaments etc.
• Direct comparison with simulations. Initial look
  shows current models get broad correlations
  correct, but details more difficult to understand

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Time run out? References to your figure here
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Ha distribution

• Ha distribution shows a bimodality mean/median
  of whole distribution can be misleading

Balogh et al. 2004
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Infared luminosity functions

• Balogh et al. (2001) evidence that MF does not
  vary strongly with environment.
• Also De Propris et al. (1998) find Coma LF
  consistent with the field