the evolution of elliptical galaxies in rich clusters
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The Properties of The Properties of Early Type Galaxies Early Type Galaxies
in Rich Clustersin Rich ClustersRobert Berrington (U. of Wyoming)Robert Berrington (U. of Wyoming)
Charles D. Dermer (NRL)Charles D. Dermer (NRL)Michael J. Pierce (U. of Wyoming)Michael J. Pierce (U. of Wyoming)Andrew Monson (U. of Wyoming)Andrew Monson (U. of Wyoming)
Sehyun Hwang (U. of Texas)Sehyun Hwang (U. of Texas)
Physical Properties of Physical Properties of Galaxy ClustersGalaxy Clusters
Rich ClustersRich Clusters Contain thousands Contain thousands
of Galaxies.of Galaxies. Masses ~10Masses ~101515 M M..
Poor ClustersPoor Clusters Contain hundreds Contain hundreds
of Galaxies.of Galaxies. Masses ~10Masses ~101414 M M..
Ab
ell
22
18
Ab
ell
2218
MK
W 4
The Physics of Cluster The Physics of Cluster MergersMergers
Gravitational force drives collisionGravitational force drives collision Total gravitational energy availableTotal gravitational energy available
Thursday, November 20, 2008
Department of Physics and Astronomy Colloquium
The Merging Cluster The Merging Cluster ScenarioScenario
Rich clusters from by Rich clusters from by accreting poor clusters.accreting poor clusters. Shocks form in ICM at boundary.Shocks form in ICM at boundary.
if vif vss exceeds sound speed of exceeds sound speed of ICMICM
Thermal particles swept up in Thermal particles swept up in shockshock Accelerated via first-order Accelerated via first-order
Fermi Fermi Sizes: ~1 Mpc are possible.Sizes: ~1 Mpc are possible.
May also reaccelerate particles.May also reaccelerate particles. Head-tail radio galaxies Head-tail radio galaxies
nearby.nearby. Total energy available Total energy available ~10~1063-6463-64
ergsergs..
Radio Halos and Cluster Radio Halos and Cluster Radio RelicsRadio Relics
Sources of extended radio emissionSources of extended radio emission No optical counterpartNo optical counterpart Typically with sizes ~1MpcTypically with sizes ~1Mpc Occur in only the most massive and X-Occur in only the most massive and X-
ray luminous of Rich clustersray luminous of Rich clusters Radio HalosRadio Halos
Mimic X-ray morphologyMimic X-ray morphology UnpolarizedUnpolarized
Thursday, November 20, 2008
Department of Physics and Astronomy Colloquium
Radio Halos and Cluster Radio Halos and Cluster Radio RelicsRadio Relics
Cluster Radio Cluster Radio RelicsRelicsPeripheral HalosPeripheral Halos Irregularly shapedIrregularly shaped Located on the cluster Located on the cluster
peripheryperiphery Linearly polarized from Linearly polarized from
shock compressionshock compression Found in clusters with evidence of a Found in clusters with evidence of a
recent or ongoing mergerrecent or ongoing merger
Thursday, November 20, 2008
Department of Physics and Astronomy Colloquium
Radio Halos and Cluster Radio Halos and Cluster Radio RelicsRadio Relics
Radio (red) and optical (blue) image of Abell 3376 showing a collision between two clusters. The large radio clouds on the right and left of the image are shock fronts propagating through the ICM.
Radio Halos and Cluster Radio Halos and Cluster Radio RelicsRadio Relics
Radio emission from relativistic electronsRadio emission from relativistic electrons EEee ~10 ~101717 eV eV Synchrotron radiationSynchrotron radiation
Luminosity: ~10Luminosity: ~1043-4443-44 ergs s ergs s-1-1
Steep spectraSteep spectra Electrons also produce high energy photonsElectrons also produce high energy photons
May be a dominant contributor to the diffuse May be a dominant contributor to the diffuse --ray backgroundray background
Observable by next generation Observable by next generation -ray -ray observatoriesobservatories
Thursday, November 20, 2008 8
Department of Physics and Astronomy Colloquium
Temporal Particle EvolutionTemporal Particle Evolution
Fokker-Plank equationFokker-Plank equation
Coulomb diffusion term Energy loss rate Source term Catastrophic loss from p-p, p-, and diffusion out of the system
Thursday, November 20, 2008 9
Department of Physics and Astronomy Colloquium
Shock DynamicsShock Dynamics
Shocked fluid velocitiesShocked fluid velocities
Thursday, November 20, 2008 10
Department of Physics and Astronomy Colloquium
Shock DynamicsShock Dynamics
Shock speedShock speed Forward and reverse mach numbers:Forward and reverse mach numbers:
Compression ratio: Compression ratio:
= 5/3 is the ratio of specific heats = 5/3 is the ratio of specific heats for an ideal gas for an ideal gas
Thursday, November 20, 2008 11
Department of Physics and Astronomy Colloquium
Particle InjectionParticle Injection
Power law distribution with Power law distribution with exponential cutoffexponential cutoff
NormalizationNormalization
Where Where e,pe,p is an efficiency factor, and is is an efficiency factor, and is set to 5%.set to 5%.
Typical values are ETypical values are Etottot101063-6463-64 ergs ergsThursday, November 20, 2008 12
Department of Physics and Astronomy Colloquium
Particle InjectionParticle Injection Maximum particle energyMaximum particle energy
Acceleration time constraintAcceleration time constraint
Energy loss constraintEnergy loss constraint for electronsfor electrons
for protonsfor protons
Size scale limitationSize scale limitation
Thursday, November 20, 2008 13
Department of Physics and Astronomy Colloquium
Physical Physical Processes/Energy Loss Processes/Energy Loss
RatesRatesElectronsElectrons
Synchrotron:Synchrotron:
Bremsstrahlung:Bremsstrahlung:
Compton:Compton:
Coulomb:Coulomb:
ProtonsProtons Coulomb:Coulomb:
Catastrophic Loss:Catastrophic Loss:
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Particle SpectraParticle Spectra
Thursday, November 20, 2008 15
Department of Physics and Astronomy Colloquium
Nonthermal Photon SpectraNonthermal Photon Spectra
Nonthermal Particle Nonthermal Particle LuminosityLuminosity
Thursday, November 20, 2008 17
Department of Physics and Astronomy Colloquium
Shock DynamicsShock Dynamics
Forward Shock Reverse Shock
Minimum Spectral IndexMinimum Spectral Index
Modeling the Coma ClusterModeling the Coma Cluster Likely a 3 body Likely a 3 body
mergermerger NGC 4839NGC 4839
Inbound orbitInbound orbit Mass ~ 0.6x10Mass ~ 0.6x101414 M M
NGC 4889NGC 4889 Near collision time Near collision time
with with
main clustermain cluster Mass ~ 0.1x10Mass ~ 0.1x101515 M M
Probable cause of radio Probable cause of radio halohalo
NGC 4874NGC 4874 Main Cluster with Mass Main Cluster with Mass
~ 0.8x10~ 0.8x101515 M M
~0.8x1015 MM
~0.6x1014 MM
1253+275
~0.1x1015 MM
Coma C
NGC 4874
NGC 4839
NGC 4889
(Colless & Dunn 1996)
Parameters for Coma Parameters for Coma ClusterCluster
Assuming HAssuming H00=70 km s=70 km s-1-1 Mpc Mpc-1-1, ,
((ΩΩ00,Ω,ΩRR,Ω,Ω) = (0.3, 0.0, 0.7)) = (0.3, 0.0, 0.7) nn00 = 3.12 x 10 = 3.12 x 10-3-3 cm cm-3-3
ββ = 0.705 = 0.705 rrcc = 257 kpc = 257 kpc e,pe,p = 1% = 1% ttageage = 9.7 x 10 = 9.7 x 1088 yrs, t yrs, tcollcoll 1.0 x 10 1.0 x 1099 yrs yrs B = 0.22 µGB = 0.22 µG MM11 = 0.8 x 10 = 0.8 x 101515 MM and M and M22 = 0.1 x 10 = 0.1 x 101515 M M
(Mohr, Mathiesen, & Evrard 1999)
Thursday, November 20, 2008 21
Department of Physics and Astronomy Colloquium
Coma ClusterComa Cluster
Radio X-ray
Coma ClusterComa Cluster
What is the Fundamental What is the Fundamental Plane (FP) of Elliptical Plane (FP) of Elliptical
Galaxies?Galaxies? Galaxies occupy a plane in the 3-D Galaxies occupy a plane in the 3-D
space defined by (Rspace defined by (Ree,<,<μμ>>ee, , )) Can be used to calculate distancesCan be used to calculate distances Has been used to study evolution of Has been used to study evolution of
galaxiesgalaxies Virial Theorem predicts RVirial Theorem predicts Ree<I><I>ee
-1 -1 22
Observed plane shows tiltObserved plane shows tilt Can also be used to study the Can also be used to study the
dynamics of galaxiesdynamics of galaxiesThursday, November 20, 2008 24
Department of Physics and Astronomy Colloquium
Cluster Data SampleCluster Data Sample
Cluster SampleCluster Sample 33 Abell clusters 33 Abell clusters average of ~60 galaxies/cluster.average of ~60 galaxies/cluster. Cluster SelectionCluster Selection
Richness RRichness R11 Redshift z<0.05Redshift z<0.05
-35-35°° Complete and homogeneous Complete and homogeneous
sample of Northern Abell sample of Northern Abell clustersclusters
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Department of Physics and Astronomy Colloquium
Spectral DataSpectral Data
Spectral DataSpectral Data Calibration clusters (Leo, Virgo, Fornax)Calibration clusters (Leo, Virgo, Fornax)
Obtained using IFU DensepakObtained using IFU Densepak Allows variable spatial sampling to match clusters at Allows variable spatial sampling to match clusters at
greater distances using a fixed fiber apereturegreater distances using a fixed fiber apereture Abell clustersAbell clusters
Data obtained with the MOS Hydra at WIYNData obtained with the MOS Hydra at WIYN Spectral resolution 0.9 Spectral resolution 0.9 Å Å (on WIYN/Hydra)(on WIYN/Hydra) S/N ~30-100S/N ~30-100
Centered on redshifted Mgb absorption Centered on redshifted Mgb absorption featurefeature
Accurately measure logAccurately measure log1010(() ) 1.8 1.8 All velocity dispersions corrected for (1+z) All velocity dispersions corrected for (1+z)
time dilationtime dilationThursday, November 20, 2008 26
Department of Physics and Astronomy Colloquium
Example SpectraExample Spectra
Imaging DataImaging Data
Photometric DataPhotometric Data I and V-band imagingI and V-band imaging Images obtained using both WIYN and WIROImages obtained using both WIYN and WIRO Surface photometry performed assuming Surface photometry performed assuming
circular aperturescircular apertures Corrections appliedCorrections applied
(1+z)(1+z)44 surface brightness dimming surface brightness dimming k-correctedk-corrected Galactic extinctionGalactic extinction
Effective Radii (REffective Radii (Ree)--50% light radius--is )--50% light radius--is used and determined empiricallyused and determined empirically
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Department of Physics and Astronomy Colloquium
The Fundamental PlaneThe Fundamental Plane Various projections of Various projections of
the FP for the the FP for the template clusters template clusters Coma, Perseus, and Coma, Perseus, and
A2199, Fornax, Virgo, A2199, Fornax, Virgo, and Leoand Leo
Brightest ellipticals Brightest ellipticals [log[log1010(() > 2.3] found ) > 2.3] found in distinct region of FPin distinct region of FP Well known they come Well known they come
from old stellar from old stellar populationspopulations
Show complex velocity Show complex velocity fieldsfields
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Department of Physics and Astronomy Colloquium
The Velocity Dispersion The Velocity Dispersion Distribution Function (VDDF)Distribution Function (VDDF)
The The distribution yields observed VDDF distribution yields observed VDDF Cross-Correlation using IRAF package FXCORCross-Correlation using IRAF package FXCOR Corrected values for (1+z) time dilation factorCorrected values for (1+z) time dilation factor
MotivationMotivation Tracer of galaxy gravitational potential Tracer of galaxy gravitational potential Minimal dependence on luminosity evolution.Minimal dependence on luminosity evolution. Directly comparable with N-body simulations.Directly comparable with N-body simulations. Quantitative measure of hierarchical merging?Quantitative measure of hierarchical merging?
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Department of Physics and Astronomy Colloquium
The Modified Schechter The Modified Schechter FunctionFunction
Originates from Schechter Luminosity Originates from Schechter Luminosity FunctionFunction
Transformed into velocity dispersion space (Transformed into velocity dispersion space () ) via Faber-Jackson relation:via Faber-Jackson relation:
Takes the form:Takes the form:
Under the assumption galaxy halos are Under the assumption galaxy halos are isothermal, we can convert the circular isothermal, we can convert the circular velocity (vvelocity (vcc) of spirals to ) of spirals to , and compare to , and compare to Ellipticals.Ellipticals.
L
Individual ClustersIndividual Clusters
Abell 1656 (Coma)Abell 1656 (Coma) Left: VDDF with Left: VDDF with
best fit (solid curve)best fit (solid curve) Right: Error Right: Error
ellipses for best fitellipses for best fit
Abell 548Abell 548 Same as aboveSame as above
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Department of Physics and Astronomy Colloquium
Properties and PromiseProperties and Promise
Steeper low-Steeper low--end power -end power laws (laws () have larger ) have larger **.. Quantitative measure of Quantitative measure of
hierarchical merging?hierarchical merging? Directly comparable with Directly comparable with
modelsmodels Weak correlation between Weak correlation between
cluster velocity dispersion cluster velocity dispersion ((clcl) and ) and **. .
Thursday, November 20, 2008
Department of Physics and Astronomy Colloquium
Comparison with Other Comparison with Other StudiesStudies
Most Probable Velocity DispersionMost Probable Velocity Dispersion
Average Velocity DispersionAverage Velocity Dispersion
SDSS Data sample of Early-type galaxies SDSS Data sample of Early-type galaxies (Sheth (Sheth et al.et al. 2003) 2003)
Our valuesOur values
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Department of Physics and Astronomy Colloquium
General Remarks Concerning General Remarks Concerning the VDDFthe VDDF
ProsPros Minimal dependence on Luminosity evolutionMinimal dependence on Luminosity evolution Galaxy merging is continuousGalaxy merging is continuous
Should see evolution in the VDDF for clusters at Should see evolution in the VDDF for clusters at z~0.5 (versus z~1.0 for Luminosity evolution)z~0.5 (versus z~1.0 for Luminosity evolution)
ConsCons Cluster and galaxy evolution is stochasticCluster and galaxy evolution is stochastic Requires multiple moderate resolution (R ~ Requires multiple moderate resolution (R ~
6000) spectra of galaxies—difficult at high z6000) spectra of galaxies—difficult at high z Requires sampling the low-log(Requires sampling the low-log() end to ) end to
measure measure accurately accurately Affected by cluster environmentAffected by cluster environmentThursday, November 20, 2008 39
Department of Physics and Astronomy Colloquium
The Mass Function of Early The Mass Function of Early Type GalaxiesType Galaxies
Mass Mass 22 R Ree 22 R Ree distribution yields mass function distribution yields mass function
Reflects the true mass of a galaxyReflects the true mass of a galaxy Can be used to isolate environmental Can be used to isolate environmental
effects and luminosity evolution from effects and luminosity evolution from mass evolutionmass evolution Luminosity Function Luminosity Function Luminosity Luminosity
evolutionevolution VDDF VDDF Mass and environmental Mass and environmental
effectseffects Mass Function Mass Function Mass evolution Mass evolution
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Department of Physics and Astronomy Colloquium
Spectral Indices of Early Type Spectral Indices of Early Type GalaxiesGalaxies
Spectral resolution 0.9 Spectral resolution 0.9 Å Å (on (on WIYN/Hydra) with typical S/N ~30-100WIYN/Hydra) with typical S/N ~30-100 Flux calibrated using secondary standardsFlux calibrated using secondary standards
Lick Indices HLick Indices H, Fe5015, Mg, Fe5015, Mg11, Mg, Mg22, Mg, Mgbb, , Fe5270, Fe5335, & Fe5470Fe5270, Fe5335, & Fe5470 Corrected for velocity dispersionCorrected for velocity dispersion Calibrated to Lick StandardCalibrated to Lick Standard
Spectral resolution of Lick Standard is 8 Spectral resolution of Lick Standard is 8 ÅÅ Small index dependent shiftSmall index dependent shift
Corrected for (1+z) redshift factorCorrected for (1+z) redshift factor
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Department of Physics and Astronomy Colloquium
Abundance trends with Abundance trends with loglog1010(())
HH vs. log vs. log1010(()) Weak correlationWeak correlation Younger stellar population Younger stellar population
with decreasing logwith decreasing log1010(().).
Mgb vs. logMgb vs. log1010(()) Increases with logIncreases with log1010(() )
(consistent with literature)(consistent with literature) Change in slope for logChange in slope for log1010(() < ) <
2.12.1
Thursday, November 20, 2008
Department of Physics and Astronomy Colloquium
Stellar PopulationsStellar Populations HH spread indicates spread indicates
5 Gyr < age < 15 5 Gyr < age < 15 Gyr.Gyr. Weak Weak dependence dependence Average age ~9 GyrAverage age ~9 Gyr
[MgFe]’ spread [MgFe]’ spread indicates 0.0 < [Fe/H] indicates 0.0 < [Fe/H] < 0.3< 0.3
[Fe/H] increases with [Fe/H] increases with loglog1010(())
All clusters show All clusters show similar Characteristicssimilar Characteristics
SSP models from (Thomas, Maraston, & Korn, MNRAS, 351, L19)
Stellar PopulationsStellar Populations
[[/Fe] increases /Fe] increases with logwith log1010(()) elements come elements come
from Type II SNfrom Type II SN Fe produced in Type Fe produced in Type
Ia SNIa SN Reflects length of Reflects length of
star formationstar formation All clusters exhibit All clusters exhibit
similar similar characteristicscharacteristics
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Department of Physics and Astronomy Colloquium
Conclusions and the FutureConclusions and the Future Likely detection of the Coma Cluster by Likely detection of the Coma Cluster by
GLAST and marginal detection by VERITAS.GLAST and marginal detection by VERITAS. Radio halo and hard X-ray emission well fit Radio halo and hard X-ray emission well fit
by cluster merger modelby cluster merger model Investigate mass and luminosity evolution Investigate mass and luminosity evolution
and quantify environmental effectsand quantify environmental effects Use the Fundamental Plane to decipher Use the Fundamental Plane to decipher
structural properties and correlate with structural properties and correlate with population modelspopulation models
Stellar populations of elliptical galaxies have Stellar populations of elliptical galaxies have increasing [Fe/H] and [increasing [Fe/H] and [/Fe] with increasing /Fe] with increasing loglog1010(().).
Further investigate star formation history of Further investigate star formation history of fainter ellipticals.fainter ellipticals.Thursday, November 20,
2008 48Department of Physics and Astronomy
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