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![Page 1: Galaxy properties in different environments: Observations Michael Balogh University of Waterloo, Canada (Look for 3 new job postings on AAS soon)](https://reader035.fdocuments.in/reader035/viewer/2022062322/5697bf811a28abf838c8518f/html5/thumbnails/1.jpg)
Galaxy properties in different Galaxy properties in different environments: Observationsenvironments: Observations
Michael BaloghUniversity 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• E+A galaxies
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Galaxy morphology
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E
ClustersF
ield
S0Spirals
Morphology-Density Relation
Dressler 1980Also: Oemler 1974; Melnick & Sargent 1977
Coma cluster • Morphological mix correlates best with local galaxy density
• Possibly additional effects in innermost regions (Whitmore et al. 1995; Dominguez et al. 2001)
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Morphology-density: evolution
Dressler et al. 1997; Couch et al. 1994; 1998Fasano et al. 2000Wide field HST: Treu et al. 2003
Log surface density
Nu
mb
er
of
gala
xies
RedshiftN
S0/N
E
Low redshift
Z~0.5
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• 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)
S to S0 transformation?Kenney et al. 2003Vollmer et al. 2004
Non-SF spiral galaxies from SDSS (Goto et al. 2003)First noted by Poggianti et al. (1999) in z~0.5 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)
Dressler 1980
Bulge size
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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)
Local galaxy density (3d)
Sp
iral
fract
ion
Arguments against ram pressure stripping:
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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
Bower, Lucey & Ellis 1992
Tight colour-magnitude relation (Faber 1973; Visvanathan & Sandage 1977; Terlevich et al. 2001)
ES0
Kuntschner & Davies 1998 (also Poggianti et al. 2001)see also Bernardi et al. 2003 for results based on SDSS dataField early-types ~2-3 Gyr younger than clusters (Kuntschner et al. 2002)
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Early-type galaxiesvan Dokkum & Franx 1996:M/L evolution consistent with high formation redshift
Zform= ∞
Zform=1
De Lucia et al. 2004Kodama et al. 2004(also Bell et al. 2003)
• Disappearance of faint red galaxies by z~1
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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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Baldry et al. 2003(u-r)
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 z~1 (Bell et al. 2004)
Bright
Faint
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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
Andreon, Lobo & Iovino 2004
• 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)
Margoniner et al. 2000
Margoniner et al. 2001
Redshift
Blu
e f
ract
ion
Radius (Mpc)
Blu
e f
ract
ion
Blu
e f
ract
ion
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• Kodama & Bower (2000) model: clusters inhibit star formation, but recent infall maintains a high blue fraction at higher redshift.
Ellingson et al. (2001)
• Leads to steeper colour gradients in higher redshift clusters
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Tully-Fisher relation at z~1
• Spiral galaxies at z~1 (both cluster and field) are brighter in B than at low redshift
• Z~1 cluster spirals brighter at fixed than field spirals (?)• See poster by Milvang-Jensen et al.
Milvang-Jensen et al. 2004
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Star formation and gas
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HI deficiency
Bravo-Alfaro et al. 2000
Davies & Lewis 1973
VLA imaging of Coma spirals
Mark I and II imaging of Virgo galaxies
18 nearby clusters: Solanes et al. 2001
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Emission lines
Dressler, Thompson & Shectman 1985; Also Gisler 1978
• Cluster galaxies of given morphological type show less nebular emission than field galaxies
• suggests star formation is suppressed in cluster galaxies
Em
issi
on
lin
e f
ract
ion
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Emission line fraction in SDSS and 2dFGRS (Balogh et al. 2004)
A901/902 supercluster (Gray et al. 2004) correlation with dark matter density
• 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
Star formation
Cluster infall regions
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H distribution
Koopmann & Kenney 2004also: Vogt et al. 2004
• Cluster galaxies often show peculiar distribution of H emission: usually truncated, or globally suppressed
• In some cases, star formation is centrally enhanced (Moss & Whittle 1993; 2000)
Virgo spirals
H for Virgo galaxy
H for normal galaxy
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Cluster galaxy evolution
Kodama et al. 2004
Couch et al. 2001Balogh et al. 2002Fujita et al. 2003
Tresse et al. 2002Complete H studies:Even at z=0.5, total SFR in clusters lower than in surrounding field
Field Field
z~0.3z~0.5
[OII] luminosity functions:Lotz et al. 2003Martin et al. 2000
SDSS/2dFGRS: Emission-line galaxies only: Ha distribution does not depend strongly on environment (Balogh et al. 2004)
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Emission lines at z~0.5
Dressler et al. 1997 Balogh et al. 1998
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Clusters
Field
2dF
Nakata et al., in prep
Postman, Lubin & Oke 2001van Dokkum et al. 2000
Fisher et al. 1998
Czoske et al. 2001
Cluster galaxy evolution
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Cluster galaxy evolution
• Complete H 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
Kodama et al. 2004
Finn et al. 2003Finn et al. 2003
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Cluster galaxy evolution
• Complete H 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
Kodama et al. 2004Finn et al. in prep
Finn et al. 2003
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E+A galaxies
• Aka: k+a, a+k, PSG, PSB, HDS, e(a)…
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Butcher-Oemler effect• 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: Goto et al. (2003)
Couch & Sharples 1987Balogh et al. in prep.
SDSS E+A galaxies
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Poggianti et al. 2004
• E+A galaxies in Coma may be correlated with X-ray emission• Strong luminosity evolution in E+A population (Tran et al. 2003)• Also found in the field (e.g.
Zabludoff et al. 1996; Balogh et al. 1999). But bright, field E+A galaxies locally may have different origin.
Balogh et al. in prep.
E+A
emission
UKIRT imaging
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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 H 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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H distribution• H 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