the evolution of elliptical galaxies in rich clusters

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

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18

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ell

2218

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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




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




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 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


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



Shock DynamicsShock Dynamics

Shocked fluid velocitiesShocked fluid velocities




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



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


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



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



Nonthermal Photon SpectraNonthermal Photon Spectra

Nonthermal Particle Nonthermal Particle LuminosityLuminosity




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)



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


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



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


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



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



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?



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



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 **. .



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



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


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



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



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



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



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

Colloquium

the evolution of elliptical galaxies in rich clusters

Science

cluster radioradio halos

cluster peripherylocated

department of physics

headtail radio galaxies

astronomy colloquium

large radio clouds

byrich clusters

poor clusterspoor clusters