The Formation Histories and Mass The Formation Histories and Mass Profiles of Some Elliptical GalaxiesProfiles of Some Elliptical Galaxies

Steve ZepfSteve Zepf

Michigan State UniversityMichigan State University

Overview – Three QuestionsOverview – Three Questions

1.1. Metal-poor globular clusters and early structure Metal-poor globular clusters and early structure formation (the biasing of the metal-poor GC formation (the biasing of the metal-poor GC population)population)

2. 2. When were the major formation epoch(s) of elliptical When were the major formation epoch(s) of elliptical galaxies? (ages of their metal-rich GCs)galaxies? (ages of their metal-rich GCs)

3.3. What are the properties of the dark matter halos around What are the properties of the dark matter halos around elliptical galaxies? (radial velocities of the globular elliptical galaxies? (radial velocities of the globular clusters)clusters)

topics left out – GC formation, dynamical evolution, topics left out – GC formation, dynamical evolution, low-mass X-ray binary GC conncetionlow-mass X-ray binary GC conncetion

Why Globular Cluster Systems?Why Globular Cluster Systems?

•• GCs have ~10GCs have ~1066 stars within a few pc stars within a few pc- remarkable densities- remarkable densities- readily observable- readily observable

•• some GCs are very old – hope of some GCs are very old – hope of constraining very early structure constraining very early structure formation.formation.

•• GCs are true simple stellar populations GCs are true simple stellar populations (to first order), so determining their (to first order), so determining their age and metallicity is much simpler age and metallicity is much simpler than for the composite populations in than for the composite populations in integrated light.integrated light.

•• GCs are observed to form in all major GCs are observed to form in all major star formation events in galaxies. star formation events in galaxies.

• • GCs are found out to very large radii GCs are found out to very large radii around galaxies – useful dynamical around galaxies – useful dynamical probes of galaxy halos.probes of galaxy halos.

one example – NGC 3256one example – NGC 3256Zepf et al 1999Zepf et al 1999

Another example – the Antennae, Whitmore et al.Another example – the Antennae, Whitmore et al.

Why Globular Cluster Systems?Why Globular Cluster Systems?

•• GCs have ~10GCs have ~1066 stars within a few pc stars within a few pc- remarkable densities- remarkable densities- readily observable- readily observable

•• some GCs are very old – hope of some GCs are very old – hope of constraining very early structure constraining very early structure formation.formation.

•• GCs are true simple stellar populations GCs are true simple stellar populations (to first order), so determining their (to first order), so determining their age and metallicity is much simpler age and metallicity is much simpler than for the composite populations in than for the composite populations in integrated light.integrated light.

•• GCs are observed to form in all major GCs are observed to form in all major star formation events in galaxies. star formation events in galaxies.

• • GCs are found out to very large radii GCs are found out to very large radii around galaxies – useful dynamical around galaxies – useful dynamical probes of galaxy halos.probes of galaxy halos.

• • DistributionDistribution because because individual GC individual GC colors/metallicities can be colors/metallicities can be determined.determined.

•• Early results from Zepf & Early results from Zepf & Ashman 93 and Ashman 93 and subsequent work suggest subsequent work suggest bimodality in optical bimodality in optical colors of GC systems of colors of GC systems of elliptical galaxies.elliptical galaxies.

•• Large samples establish Large samples establish bimodality as the norm bimodality as the norm (>60%) for ellipticals, S0s (>60%) for ellipticals, S0s consistent but less certain. consistent but less certain.

e.g. Kundu & Whitmore 01 e.g. Kundu & Whitmore 01 ~30 Ellipticals and ~30 Ellipticals and ~30 S0s~30 S0s

Bimodality in GC Systems of Elliptical GalaxiesBimodality in GC Systems of Elliptical Galaxies

• • For mostly old systems, color traces For mostly old systems, color traces metallicity, use Milky Way and metallicity, use Milky Way and models to do this (age-met models to do this (age-met degeneracy still present).degeneracy still present).

• • Can’t get the two peaks in the Can’t get the two peaks in the observed colors from a single-observed colors from a single-peaked metallicity distribution.peaked metallicity distribution.

GCs come in two metallicity GCs come in two metallicity groups .groups .

•• Metal-rich GCs - closely tied to Metal-rich GCs - closely tied to bulk of host galaxy - trace galaxy bulk of host galaxy - trace galaxy formation/assembly. formation/assembly.

•• Metal-poor GCs - Low metals, Metal-poor GCs - Low metals, extended spatial distribution, and extended spatial distribution, and old ages in Milky Way halo - old ages in Milky Way halo - constraints on early structure constraints on early structure formation? formation?

Note this division in abundance also Note this division in abundance also seen in Galaxy GC systemseen in Galaxy GC system

Color and Metallicity DistributionsColor and Metallicity Distributions

Formation Sites of Metal-Poor GCsFormation Sites of Metal-Poor GCsMetal-poor GCs include the oldest surviving fossil structures. When Metal-poor GCs include the oldest surviving fossil structures. When

and where they formed constrains early star formation in the and where they formed constrains early star formation in the universe.universe.

Formation redshift can be addressed by determining the Formation redshift can be addressed by determining the “biasing” in GC numbers vs galaxy mass (Rhode & Zepf 2004, “biasing” in GC numbers vs galaxy mass (Rhode & Zepf 2004, Rhode, Zepf, & Santos 2005). Basic idea (Santos 2003)…Rhode, Zepf, & Santos 2005). Basic idea (Santos 2003)…

• • More massive galaxies have a greater fraction of their mass More massive galaxies have a greater fraction of their mass collapsed at a given redshift than lower mass galaxies on collapsed at a given redshift than lower mass galaxies on average.average.

• • If metal-poor globular cluster formation has a preferred early If metal-poor globular cluster formation has a preferred early formation epoch, then more massive galaxies will have more formation epoch, then more massive galaxies will have more metal-poor GCs per stellar mass. The earlier the formation metal-poor GCs per stellar mass. The earlier the formation epoch, the greater the “bias” in the metal-poor GC population epoch, the greater the “bias” in the metal-poor GC population today.today.

• • Need observational determination of total number of metal-poor Need observational determination of total number of metal-poor GCs in galaxies with a range of masses GCs in galaxies with a range of masses Rhode & Zepf Rhode & Zepf 01,03,0401,03,04

Observational RequirementsObservational Requirements

•• Both wide-field and deep imaging (many extant data only Both wide-field and deep imaging (many extant data only cover ~10% of the GC system). cover ~10% of the GC system).

•• Need colors to separate blue and red GCs to isolate metal-Need colors to separate blue and red GCs to isolate metal-poor GCs for very early formation.poor GCs for very early formation.

Katherine Rhode’s PhD thesis at Yale.Katherine Rhode’s PhD thesis at Yale.

•• Utilize large-area CCDs, multiple colors, new analysis Utilize large-area CCDs, multiple colors, new analysis techniques to make both these advances for sample of 4 techniques to make both these advances for sample of 4 nearby ellipticals and 9 spirals (ellipticals in Rhode & nearby ellipticals and 9 spirals (ellipticals in Rhode & Zepf 2004, 2001, spirals in Rhode & Zepf 2003 and in Zepf 2004, 2001, spirals in Rhode & Zepf 2003 and in prep).prep).

NGC 4472 – 34’ x 34’ field. Ground-based Mosaic image and GC identification NGC 4472 – 34’ x 34’ field. Ground-based Mosaic image and GC identification Rhode & Zepf 2001, 2004; WFPC2 images in blue, ACS in redRhode & Zepf 2001, 2004; WFPC2 images in blue, ACS in red

Results: Early-type Sample(Rhode & Zepf 2004, AJ, 127, 302)

NGC 4594: 1748 GC candidates selected in BVR

NGC 4406: 1400 GC candidates

NGC 3379: 321 GC candidates

Mosaic image of NGC 4594 FOV = 38’ x 37’, FWHM ~ 1”

Results: Early-type Sample(Rhode & Zepf 2004)

Cluster Es Field E/S0s

Results: Early-type Sample(Rhode & Zepf 2004)

Color Distributions

• Two (or more) Gaussians fit better than one at >99.9% confidence

• NGC 4472, NGC 4406, and NGC 4594 have 60% blue, 40% red GCs

• NGC 3379 has 70% blue, 30% red

Disagrees with collapse+accretion and multi-phase SF models, which predict larger proportions of blue GCs in more luminous galaxies

Observational ResultsObservational Results

T T N NGCGC/10/1099MMSunSun

Determined Determined observationally for observationally for metal poor GCs in metal poor GCs in galaxies with a range galaxies with a range of galaxy masses.of galaxy masses.

Some biasing Some biasing observedobserved

Rhode, Zepf, & Santos Rhode, Zepf, & Santos 2005 ApJL 2005 ApJL

Formation RedshiftFormation Redshift

Hierarchical model with Hierarchical model with Greg BryanGreg Bryan

Most systematics tend to Most systematics tend to flatten the trend in the flatten the trend in the data. data.

most likely not most likely not extremely early extremely early formation formation zzform form < ~11< ~11

Ages of Formation Epoch(s) of Elliptical Galaxies – Ages of Formation Epoch(s) of Elliptical Galaxies – Why “Metal-Rich” GC Systems?Why “Metal-Rich” GC Systems?

•• Metal-rich GC systems trace Metal-rich GC systems trace elliptical galaxy populations elliptical galaxy populations spatially and in color.spatially and in color.

•• GC formation observed in all GC formation observed in all starbursts in local universe – starbursts in local universe – trace major formation episodes.trace major formation episodes.

•• Each individual GC is a simple Each individual GC is a simple stellar population, most basic stellar population, most basic determination of ages and determination of ages and abundances. GC systems reveal abundances. GC systems reveal distributiondistribution in age and metallicity in age and metallicity of major formation events of of major formation events of ellipticals.ellipticals.

Ages of the Formation Epoch(s)Ages of the Formation Epoch(s)How to get ages of GC populations? How to get ages of GC populations?

Optical colors good for finding metallicity peaks, but Optical colors good for finding metallicity peaks, but bad for ages because of age-metallicity degeneracy –bad for ages because of age-metallicity degeneracy –older age and higher metal content have same effect older age and higher metal content have same effect on optical colors (colors can be red because of old on optical colors (colors can be red because of old age or high metal content). Ideas…age or high metal content). Ideas…

•• luminosity function (assumes mass function)luminosity function (assumes mass function)•• Balmer absorption lines Balmer absorption lines • • optical to near-infrared colors optical to near-infrared colors efficient, effective efficient, effective

Breaking Age-Metallicity Degeneracy with Breaking Age-Metallicity Degeneracy with Near-IR to Optical PhotometryNear-IR to Optical Photometry

I-H color primarily sensitive to metallicity, g-I color more I-H color primarily sensitive to metallicity, g-I color more sensitive to age. True of any set of optical to near-infrared sensitive to age. True of any set of optical to near-infrared color vs optical color – consequence of basic stellar properties.color vs optical color – consequence of basic stellar properties.

Difference between 3 Gyr (int. age) and 13 Gyr (old age) is about Difference between 3 Gyr (int. age) and 13 Gyr (old age) is about 0.3 mag.0.3 mag.

NGC 3115, NGC 4365 in VIKNGC 3115, NGC 4365 in VIK

First try with this technique – First try with this technique – Puzia, Zepf, Kissler-Patig, Puzia, Zepf, Kissler-Patig, Hilker, & Minniti 2002 Hilker, & Minniti 2002

NGC 3115 – primarily consistent NGC 3115 – primarily consistent with typically old GCswith typically old GCs

NGC 4365 – surprise! – many GCs NGC 4365 – surprise! – many GCs with VIK colors only explained with VIK colors only explained by intermediate ages. by intermediate ages.

Important result indicating some Important result indicating some elliptical galaxies had substantial elliptical galaxies had substantial formation activity at t <~ 5 Gyr. formation activity at t <~ 5 Gyr.

ImplicationsImplications Not without controversyNot without controversy

•• Most galaxy light studies suggest older ages for integrated Most galaxy light studies suggest older ages for integrated stellar light of NGC 4365.stellar light of NGC 4365.

•• Spectroscopy of GCs in NGC 4365 confused – initial Spectroscopy of GCs in NGC 4365 confused – initial confirmation of int. age by Larsen et al. 2003, similar confirmation of int. age by Larsen et al. 2003, similar data from same instrument, different result, Brodie et al. data from same instrument, different result, Brodie et al. 2005.2005.

•• Only case of possible inconsistency between optical to Only case of possible inconsistency between optical to near-ir colors and optical spectroscopy for GC systems near-ir colors and optical spectroscopy for GC systems (agree for NGC 1316, NGC 1399, NGC 3115, NGC 4472) (agree for NGC 1316, NGC 1399, NGC 3115, NGC 4472)

Get better data!Get better data!

Three deep NIC3 pointings for NGC 4365, very high S/NThree deep NIC3 pointings for NGC 4365, very high S/N

New NICMOS dataNew NICMOS data(Kundu, Zepf, Hempel et al 2005 ApJ, 634, L41 )(Kundu, Zepf, Hempel et al 2005 ApJ, 634, L41 )

Independent, deep data – data deep enough to separate optical Independent, deep data – data deep enough to separate optical and near-ir colors.and near-ir colors.

Same result as before – substantial population of NGC 4365 GCs Same result as before – substantial population of NGC 4365 GCs with optical/near-ir colors only accounted for with int. age. with optical/near-ir colors only accounted for with int. age.

Comparison with other archival NIC3 data for NGC 1399 GCs.Comparison with other archival NIC3 data for NGC 1399 GCs.

Mostly old GCs in NGC 1399, with a few int. ages, same as seen in Mostly old GCs in NGC 1399, with a few int. ages, same as seen in previous spectroscopy.previous spectroscopy.

Simple Fraction of Int. Age GCsSimple Fraction of Int. Age GCs Simple test, adopts Simple test, adopts

two two populations, populations, one at 13 Gyr, one at 13 Gyr, gets best fitting gets best fitting age and age and fraction of 2fraction of 2ndnd population.population.

NGC 1399 result of NGC 1399 result of ~10% int. age ~10% int. age population population same as seen in same as seen in small small spectroscopy spectroscopy sample.sample.

NGC 4365 NGC 4365 substantial int. substantial int. age result age result confirmed confirmed

Is it age?Is it age?• • Test colors by getting much better, independent data. Test colors by getting much better, independent data.

Deep NICMOS H-band imaging of NGC 4365. Deep NICMOS H-band imaging of NGC 4365. Much reduced photometric uncertainties. Much reduced photometric uncertainties.

Colors confirmed, intermediate ages show up in Colors confirmed, intermediate ages show up in independent, deep dataindependent, deep data

Is it age?Is it age?• • Test colors by getting much better, independent data. Test colors by getting much better, independent data.

Deep NICMOS H-band imaging of NGC 4365. Deep NICMOS H-band imaging of NGC 4365. Much reduced photometric uncertainties. Much reduced photometric uncertainties.

Colors confirmed, intermediate ages show up in Colors confirmed, intermediate ages show up in independent, deep dataindependent, deep data

• • What about the stellar populations models?What about the stellar populations models?

M87 – deep NIC3 GO and AR dataM87 – deep NIC3 GO and AR data

Kundu, Zepf & Hempel 2006Kundu, Zepf & Hempel 2006New NIC3 data in center, archival NIC data in outer field New NIC3 data in center, archival NIC data in outer field

with new ACS data.with new ACS data. Models lines appear to be mostly correct.Models lines appear to be mostly correct.Dominant old age in agreement with optical color bimodality Dominant old age in agreement with optical color bimodality

and spectroscopic results for M87and spectroscopic results for M87

Is it age?Is it age?

• • Test colors by getting much better, independent data. Test colors by getting much better, independent data. Deep NICMOS H-band imaging of NGC 4365. Deep NICMOS H-band imaging of NGC 4365. Much reduced photometric uncertainties. Much reduced photometric uncertainties.

Colors confirmed, intermediate show up in Colors confirmed, intermediate show up in independent, deep dataindependent, deep data

• • What about the stellar populations models?What about the stellar populations models?

Other galaxies match old model prediction lines very Other galaxies match old model prediction lines very well. Can’t shift model lines.well. Can’t shift model lines.

More NICMOS Results More NICMOS Results (Kundu, Zepf, Hempel 2006 in prep)(Kundu, Zepf, Hempel 2006 in prep)

Comparison of same NIC data for NGC 4365 and M87 reveals Comparison of same NIC data for NGC 4365 and M87 reveals clear difference – only known way to account for this is clear difference – only known way to account for this is intermediate age for substantial fraction of NGC 4365 GCs.intermediate age for substantial fraction of NGC 4365 GCs.

Is it age?Is it age?• • Test colors by getting much better, independent data. Test colors by getting much better, independent data.

Deep NICMOS H-band imaging of NGC 4365. Deep NICMOS H-band imaging of NGC 4365. Much reduced photometric uncertainties. Much reduced photometric uncertainties.

Colors confirmed, intermediate show up in Colors confirmed, intermediate show up in independent, deep dataindependent, deep data

• • What about the stellar populations models?What about the stellar populations models?

Other galaxies match old model prediction lines very Other galaxies match old model prediction lines very well. Can’t shift model lines.well. Can’t shift model lines.

only extant explanation that works for only extant explanation that works for NGC 4365 optical to near-ir is intermediate NGC 4365 optical to near-ir is intermediate age.age.

• • Optical to near-ir color technique is efficient and Optical to near-ir color technique is efficient and effective.effective. What about a galaxy sample?What about a galaxy sample?

Optical to near-ir to date (Hempel, Kundu, Puzia, K-P, Geisler, Zepf)Optical to near-ir to date (Hempel, Kundu, Puzia, K-P, Geisler, Zepf)

Sample in wordsSample in wordsNGC 4472 – oldNGC 4472 – old

NGC 3115, NGC 7192, M87 – old with possible NGC 3115, NGC 7192, M87 – old with possible “frosting”“frosting”

NGC 1399 – old with definite ~10% intermediate ageNGC 1399 – old with definite ~10% intermediate age

NGC 5846 – probable substantial int. age componentNGC 5846 – probable substantial int. age component

NGC 4365 – clear intermediate age componentNGC 4365 – clear intermediate age component

Data in hand – Cen A, NGC 3379, NGC 4594Data in hand – Cen A, NGC 3379, NGC 4594

Notes: old for colors and spectra just means t > ~8-10 Gyr, z >~1Notes: old for colors and spectra just means t > ~8-10 Gyr, z >~1Tests higher metallicity GCs, not lower metallicity ones. Tests higher metallicity GCs, not lower metallicity ones. Expect higher fraction of younger ones at brighter limits.Expect higher fraction of younger ones at brighter limits.Stochastic effects from finite number of stars come into play.Stochastic effects from finite number of stars come into play.

Hempel, Kundu, Puzia, Kissler-Patig, Geisler, Zepf, et al.Hempel, Kundu, Puzia, Kissler-Patig, Geisler, Zepf, et al.

Overview of AgesOverview of Ages

•• Current data indicate a modest but significant fraction of Current data indicate a modest but significant fraction of Es have substantial intermediate-age GC population in Es have substantial intermediate-age GC population in metal-rich population (major formation even at z < 1). metal-rich population (major formation even at z < 1).

Majority have major formation events at z > 1.Majority have major formation events at z > 1.

Of this majority many have small population of Of this majority many have small population of intermediate-age GCs (e.g. NGC 1399).intermediate-age GCs (e.g. NGC 1399).

•• Overall seems consistent with hierarchical merging – Overall seems consistent with hierarchical merging – some merging today, increasing significantly to the past.some merging today, increasing significantly to the past.

•• Large optical, near-ir GCS survey enable much more Large optical, near-ir GCS survey enable much more detailed tests (NIC3, SOAR,...). Combine with targeted detailed tests (NIC3, SOAR,...). Combine with targeted optical spectroscopy.optical spectroscopy.

Kinematics of Globular Cluster SystemsKinematics of Globular Cluster Systems Address two questionsAddress two questions

11. Dark matter around elliptical galaxies – how . Dark matter around elliptical galaxies – how much, spatial distribution? Globular clusters much, spatial distribution? Globular clusters one of best probes way out into the halos.one of best probes way out into the halos.

2. 2. Angular momentum in elliptical galaxies. Why Angular momentum in elliptical galaxies. Why don’t they have any (in their inner regions don’t they have any (in their inner regions anyway). Search for angular momentum anyway). Search for angular momentum transported outwards predicted by models.transported outwards predicted by models.

The Utility of GCs for Halo KinematicsThe Utility of GCs for Halo KinematicsGlobular Clusters provide Globular Clusters provide

observable individual observable individual objects at very large objects at very large radii for which the sky radii for which the sky dominates the dominates the integrated light.integrated light.

e.g. NGC4472 giant Virgo e.g. NGC4472 giant Virgo E Photometry - KPNO E Photometry - KPNO Mosaic Camera Mosaic Camera (Rhode & Zepf 2001, (Rhode & Zepf 2001, 2004)2004)

Obviously useful as Obviously useful as dynamical probes of dynamical probes of halo mass distribution halo mass distribution

Do Lower Luminosity Ellipticals have Do Lower Luminosity Ellipticals have Expected Dark Matter Halos?Expected Dark Matter Halos?

• A few recent results suggest maybe lower luminosity A few recent results suggest maybe lower luminosity ellipticals are lacking dark matter halos or have ellipticals are lacking dark matter halos or have halos with either low concentration or modest M/L halos with either low concentration or modest M/L (e.g. Romanowsky et al).(e.g. Romanowsky et al).

• Test this with VLT multi-fiber observations of Test this with VLT multi-fiber observations of globular clusters over a very wide field around best globular clusters over a very wide field around best case Lcase L** elliptical galaxy, NGC 3379. elliptical galaxy, NGC 3379.

1. Confirm or reject previous result.1. Confirm or reject previous result.2. Extend kinematical information to larger radii.2. Extend kinematical information to larger radii.

Results for NGC 3379Results for NGC 3379

Bergond, Zepf, Romanowsky, Bergond, Zepf, Romanowsky, Rhode, & Sharples 2006, Rhode, & Sharples 2006, A&A, 448, 155A&A, 448, 155

• • Red points and error bars GC Red points and error bars GC dispersions with radius.dispersions with radius.

• • Models:Models: CDM-like halos CDM-like halos with standard with standard concentrations in blue concentrations in blue hatched region. Blue hatched region. Blue dashed lines region covered dashed lines region covered by halo occupation models. by halo occupation models. Purple line best fit from Purple line best fit from outer HI ring and outer HI ring and CDM CDM halo with most likely halo with most likely concentration. Bottom concentration. Bottom dashed line is mass traces dashed line is mass traces light.light.

GC velocity dispersions are GC velocity dispersions are in agreement with in agreement with CDM-CDM-like halos.like halos.

Angular Momentum in GalaxiesAngular Momentum in Galaxies• General idea – protogalaxies torqued up by tidal interactions with General idea – protogalaxies torqued up by tidal interactions with

other protogalaxies, haveother protogalaxies, have “spin parameter” “spin parameter” 0.05 ( 0.05 ( = J E^1/2 / = J E^1/2 / G M^1/2), G M^1/2), goes back to Hoyle, confirmed in modern cosmological goes back to Hoyle, confirmed in modern cosmological simulations, mostly independent of mass and environment.simulations, mostly independent of mass and environment.

•• Halos to galaxies – Baryons that make up the parts of the galaxies we Halos to galaxies – Baryons that make up the parts of the galaxies we see cool, collapse, and spin up.see cool, collapse, and spin up.

• Similar densities of ellipticals and spirals suggest ellipticals and Similar densities of ellipticals and spirals suggest ellipticals and spirals collapsed by roughly the same amount. But ellipticals have spirals collapsed by roughly the same amount. But ellipticals have an order of magnitude or more less angular momentum. an order of magnitude or more less angular momentum.

What happened to ellipticals?What happened to ellipticals?

• Need to transfer angular momentum. This has long been realized, as Need to transfer angular momentum. This has long been realized, as has the utility of hierarchical structure formation and merging to has the utility of hierarchical structure formation and merging to transfer ang momentum. transfer ang momentum.

• Can we find the angular momentum at large radii around ellipticals?Can we find the angular momentum at large radii around ellipticals?

Kinematics of GC SystemsKinematics of GC Systems NGC 4472 NGC 4472

• • Our new VLT Flames data for NGC 4472, up to ~350 velocities out to Our new VLT Flames data for NGC 4472, up to ~350 velocities out to ~ 75 kpc, builds on 144 GCs (Zepf et al 2000, Sharples et al 1998) to ~ 75 kpc, builds on 144 GCs (Zepf et al 2000, Sharples et al 1998) to ~ 40 kpc, and another 100 over same area from Cote et al. (2003).~ 40 kpc, and another 100 over same area from Cote et al. (2003).

Extant results (Z2000 et al)Extant results (Z2000 et al)

• • not much evidence for rotation anywhere (to ~50 kpc).not much evidence for rotation anywhere (to ~50 kpc).• • Metal-poor GC population may have modest rotation. Higher Metal-poor GC population may have modest rotation. Higher than than

more spatially concentrated metal-rich GCs. more spatially concentrated metal-rich GCs. • • No evidence for rotation in metal-rich GC population about any axis No evidence for rotation in metal-rich GC population about any axis

-- -- Upper limit on vUpper limit on v// < 0.34 (99%)< 0.34 (99%) Metal-rich GC pop not rotationally supported. Significant angular Metal-rich GC pop not rotationally supported. Significant angular

momentum transport required. Implicates mergers, But where did momentum transport required. Implicates mergers, But where did it go?it go?

•• M87 consistent with 4472, evidence for ang mom in outer regions, M87 consistent with 4472, evidence for ang mom in outer regions, M104 may have counter-rotating outer GCs.M104 may have counter-rotating outer GCs.

Kinematics of GC SystemsKinematics of GC Systems NGC 4472 NGC 4472

• • Our new VLT Flames data for NGC 4472, up to ~350 velocities out to Our new VLT Flames data for NGC 4472, up to ~350 velocities out to ~ 75 kpc, builds on 144 GCs (Zepf et al 2000, Sharples et al 1998) to ~ 75 kpc, builds on 144 GCs (Zepf et al 2000, Sharples et al 1998) to ~ 40 kpc, and another 100 over same area from Cote et al. (2003).~ 40 kpc, and another 100 over same area from Cote et al. (2003).

Extant results (Z2000 et al)Extant results (Z2000 et al)

• • not much evidence for rotation anywhere (to ~50 kpc).not much evidence for rotation anywhere (to ~50 kpc).• • Metal-poor GC population may have modest rotation. Higher Metal-poor GC population may have modest rotation. Higher than than

more spatially concentrated metal-rich GCs. more spatially concentrated metal-rich GCs. • • No evidence for rotation in metal-rich GC population about any axis No evidence for rotation in metal-rich GC population about any axis

-- -- Upper limit on vUpper limit on v// < 0.34 (99%)< 0.34 (99%) Metal-rich GC pop not rotationally supported. Significant angular Metal-rich GC pop not rotationally supported. Significant angular

momentum transport required. Implicates mergers, But where did momentum transport required. Implicates mergers, But where did it go?it go?

•• M87 consistent with 4472, evidence for ang mom in outer regions, M87 consistent with 4472, evidence for ang mom in outer regions, M104 may have counter-rotating outer GCs.M104 may have counter-rotating outer GCs.

SUMMARYSUMMARY•• Globular Cluster Systems show the episodic formation Globular Cluster Systems show the episodic formation

history of their host elliptical galaxies. history of their host elliptical galaxies.

•• Not all of these episodes are old (intermediate-age GC Not all of these episodes are old (intermediate-age GC populations in normal ellipticals). Broad agreement with populations in normal ellipticals). Broad agreement with hierarchical merging models. hierarchical merging models.

•• Optical to near-infrared colors of GC systems efficient, Optical to near-infrared colors of GC systems efficient, straightforward way to constrain ages of major formation straightforward way to constrain ages of major formation episodes.episodes.

• Metal-poor GCs are “biased” with galaxy mass, potential to Metal-poor GCs are “biased” with galaxy mass, potential to constrain their formation sites/epochs.constrain their formation sites/epochs.

• Dark matter halos ubiquitous around elliptical galaxies. Dark matter halos ubiquitous around elliptical galaxies.

• Angular momentum transport needed for elliptical galaxy Angular momentum transport needed for elliptical galaxy formation formation mergers. Out to large radii in at least one well- mergers. Out to large radii in at least one well-studied case. studied case.

NGC 4472 – new dataNGC 4472 – new data

Hempel, Zepf, Hempel, Zepf, Kundu, & Kundu, & Geisler 2006Geisler 2006

Ongoing survey, Ongoing survey, NGC 4472 NGC 4472 results show results show old ages in one old ages in one of strongest of strongest bimodal cases, bimodal cases, as expected.as expected.

Insensitivity to ModelsInsensitivity to Models

Models on previous page Bruzual-Charlot, here Anders & Fritze v. Models on previous page Bruzual-Charlot, here Anders & Fritze v. Alvensleben and Maraston. Basically same answers. Optical to near-ir Alvensleben and Maraston. Basically same answers. Optical to near-ir approach is astrophysically straightforward.approach is astrophysically straightforward.

NGC 4365 – photo and spect.NGC 4365 – photo and spect.

Kundu, Zepf et al Kundu, Zepf et al optical to optical to near-ir colors near-ir colors of objects with of objects with spectroscopy. spectroscopy.

Note optical to Note optical to near-ir data near-ir data around raround ree , , B05 at large B05 at large r .r .

Mass Profile of NGC 4472Mass Profile of NGC 4472Derived fromDerived from• • Spherical Jeans eqn and Spherical Jeans eqn and

isotropic orbitsisotropic orbits• • smoothed smoothed distribution distribution• • Observed GCS profileObserved GCS profileCompared toCompared to• • Mass profile from hot gas Mass profile from hot gas

observed in X-rays (Irwin observed in X-rays (Irwin & Sarazin 1997)& Sarazin 1997)

Hydrostatic equilibrium Hydrostatic equilibrium for gas and isotropic for gas and isotropic orbits for stars give the orbits for stars give the same answer within the same answer within the errors.errors.(M/L)(M/L)B B 12 at 34 kpc, 12 at 34 kpc, increases roughly as sqrt increases roughly as sqrt (r) to larger radii.(r) to larger radii.

Potential of near-IR photometryPotential of near-IR photometry

V-I colors have more age V-I colors have more age sensitivity than V-K sensitivity than V-K colors colors V-I, V-K can V-I, V-K can break age-metallicity break age-metallicity degeneracy.degeneracy.

Plot on the right shows Plot on the right shows the Milky Way and the Milky Way and M31 GCs and various M31 GCs and various models for 12 Gyr and models for 12 Gyr and a range of [Fe/H] a range of [Fe/H]

Younger ages will have Younger ages will have blue V-I for a given V-blue V-I for a given V-K. K.

Note good agreement of Note good agreement of models with CMD ages.models with CMD ages.

Low-Mass X-ray Binary -Low-Mass X-ray Binary -Globular Cluster Connection Globular Cluster Connection

•• A LMXB is a compact object accreting from a A LMXB is a compact object accreting from a companion low-mass star. companion low-mass star.

•• LMXBs are X-ray bright – typical L ~ 10LMXBs are X-ray bright – typical L ~ 103737 ergs/s ergs/s Extragalactic obs are more typically 10Extragalactic obs are more typically 103838

•• In Milky Way, only ~13 LMXBs in Galactic GCs. In Milky Way, only ~13 LMXBs in Galactic GCs. This is 10% of total LMXB population, even This is 10% of total LMXB population, even though less than 0.1% of the stars are in GCs. 1) though less than 0.1% of the stars are in GCs. 1) Need more numbers for stats and 2) LMXBs Need more numbers for stats and 2) LMXBs are clearly over-represented in GCs – dynamical are clearly over-represented in GCs – dynamical formation in dense environment. formation in dense environment. Great progress in extragalactic studiesGreat progress in extragalactic studies

NGC 4472 as an NGC 4472 as an exampleexample

Chandra image in Chandra image in GrayscaleGrayscaleHST-WFPC2 dark HST-WFPC2 dark outlinesoutlines

Chandra sources Chandra sources circled, black circles are circled, black circles are matches with GCs matches with GCs found with HST.found with HST.

Kundu, Maccarone, & Kundu, Maccarone, & Zepf 2002, ApJLZepf 2002, ApJL

Much of the X-ray emission from early-type galaxies is from Much of the X-ray emission from early-type galaxies is from LMXBsLMXBs Many (~50%) of the LMXBs are in globular clustersMany (~50%) of the LMXBs are in globular clusters

What observables determine LMXB presence?What observables determine LMXB presence?

Kundu, Maccarone, & Zepf 2002, Sarazin et al. 2003, MKZ03 Kundu, Maccarone, & Zepf 2002, Sarazin et al. 2003, MKZ03 KMZP03, Jordan et al. 2004, KMZ 2004… KMZP03, Jordan et al. 2004, KMZ 2004…

•• Globular cluster luminosity (mass) – probability of a LMXB Globular cluster luminosity (mass) – probability of a LMXB scales roughly linearly with GC massscales roughly linearly with GC mass

•• Globular cluster color (metallicity) – probability of a LMXB Globular cluster color (metallicity) – probability of a LMXB roughly 3x larger for red (metal-rich) GCs relative to roughly 3x larger for red (metal-rich) GCs relative to blue (metal-poor) GCsblue (metal-poor) GCs

Statistically marginal correlations with globular cluster size Statistically marginal correlations with globular cluster size and distance from galaxy center.and distance from galaxy center.

Metallicity effect unexpected, what’s the evidence?Metallicity effect unexpected, what’s the evidence?

NGC 4472 – KMZ02NGC 4472 – KMZ02

Small points -Small points - globular clustersglobular clusters

Dark Points –Dark Points – LMXB – GC LMXB – GC

matchesmatches

Shows LMXBs Shows LMXBs preferentially in preferentially in higher L,redder higher L,redder

GCs.GCs.

Metallicity effectMetallicity effect at very highat very high significance. significance.

KMZ 2002KMZ 2002

Another look and another galaxy (KMZ02, KMZP03)Another look and another galaxy (KMZ02, KMZP03)

More galaxies…. (KMZ04)More galaxies…. (KMZ04)

And another one…. (KMZ04)And another one…. (KMZ04)

Key is intermediate age Key is intermediate age globular cluster globular cluster population in NGC 4365 population in NGC 4365 (discovered using optical (discovered using optical to near-ir photometry, to near-ir photometry, will go deeper with will go deeper with NIC3).NIC3).

Known broad age range Known broad age range allows test of effect of age. allows test of effect of age. GCs open circles, red dots GCs open circles, red dots GCs with LMXbs GCs with LMXbs

Result is no significant Result is no significant age effect! age effect!

Kundu, Maccarone, Zepf, Kundu, Maccarone, Zepf, & Puzia 2003, ApJL& Puzia 2003, ApJL

What About Age? What About Age? - No Strong Age Effect in NGC 4365- No Strong Age Effect in NGC 4365

Possible Explanation – Possible Explanation – Irradiation Induced Winds Irradiation Induced Winds

(Maccarone, Kundu, & Zepf 2004) (Maccarone, Kundu, & Zepf 2004)

•• X-rays heat mass donor star. Energy can be dissipated by X-rays heat mass donor star. Energy can be dissipated by line cooling or winds.line cooling or winds.

•• Line cooling dominates for metal-rich stars, winds for Line cooling dominates for metal-rich stars, winds for metal-poor stars (Iben, Tutukov, & Federova 1997).metal-poor stars (Iben, Tutukov, & Federova 1997).

•• Lifetime then varies with metallicity - more winds means Lifetime then varies with metallicity - more winds means less mass to accrete and shorter lifetime, so fewer X-ray less mass to accrete and shorter lifetime, so fewer X-ray sources in metal poor systems.sources in metal poor systems.

•• Also consistent with observed spectral differences with Also consistent with observed spectral differences with metallicity (e.g. Maccarone, Kundu, & Zepf 2003, Irwin metallicity (e.g. Maccarone, Kundu, & Zepf 2003, Irwin & Bregman 1999). & Bregman 1999).

LMXB- Globular Cluster ReviewLMXB- Globular Cluster Review1.1. Much of the X-ray emission in early-type galaxies comes Much of the X-ray emission in early-type galaxies comes

from Low-Mass X-ray Binaries (LMXBs),from Low-Mass X-ray Binaries (LMXBs), and m and many any (~50%) of the LMXBs are in globular clusters.(~50%) of the LMXBs are in globular clusters.

2.2. Metal-rich globular clusters are 3x as likely as otherwise Metal-rich globular clusters are 3x as likely as otherwise similar metal-poor clusters to host LMXBs (Kundu, similar metal-poor clusters to host LMXBs (Kundu, Maccarone, & Zepf 2002, MKZ2004).Maccarone, & Zepf 2002, MKZ2004).

3.3. Age is not a significant parameter determining whether or Age is not a significant parameter determining whether or not a LMXB is found in a globular cluster (Kundu, not a LMXB is found in a globular cluster (Kundu, Maccarone, Zepf, & Puzia 2003).Maccarone, Zepf, & Puzia 2003).

4.4. An irradiation induced wind model can account for the An irradiation induced wind model can account for the strong metallicity dependence and lack of an age strong metallicity dependence and lack of an age dependence (Maccarone, Kundu, & Zepf 2004).dependence (Maccarone, Kundu, & Zepf 2004).

An extragalactic globular clusterAn extragalactic globular cluster

Because of dissipation and enrichment in progenitor disks Because of dissipation and enrichment in progenitor disks and during the merger itself, the metal-rich red GCs and during the merger itself, the metal-rich red GCs should be more concentrated towards the center of the should be more concentrated towards the center of the galaxy than the metal-poor blue GCs. Confirmed by galaxy than the metal-poor blue GCs. Confirmed by Geisler et al in 96, many other cases now.Geisler et al in 96, many other cases now.

Spatial Distribution of GCs by ColorSpatial Distribution of GCs by Color

M87, Kundu & Zepf 2004M87, Kundu & Zepf 2004

redred

blueblue

Dynamical InformationDynamical Information

Velocities for 144 GCs Velocities for 144 GCs around NGC 4472 around NGC 4472

(Zepf et al. 2000, Beasley et al. (Zepf et al. 2000, Beasley et al.

2000, Sharples et al 1998)2000, Sharples et al 1998)

• • From CFHT and WHT – note From CFHT and WHT – note wide-field is valuable, GCs wide-field is valuable, GCs available to very large radiiavailable to very large radii

• • These data extend to ~ 8´, factor These data extend to ~ 8´, factor of 4 larger than previous of 4 larger than previous velocity data.velocity data.

(half-light radius of galaxy light is (half-light radius of galaxy light is 1’ ~4 kpc, so 8’ ~32 kpc) 1’ ~4 kpc, so 8’ ~32 kpc)

How do Globular Clusters Form?How do Globular Clusters Form? First: First: PRESSURE – High pressure in the interstellar medium of PRESSURE – High pressure in the interstellar medium of

starbursts can account for the formation of dense star clusters starbursts can account for the formation of dense star clusters (Elmegreen & Efremov, Ashman & Zepf 2001).(Elmegreen & Efremov, Ashman & Zepf 2001).r r M M1/21/2 P P-1/4-1/4

Molecular clouds that form in the high pressure environment of Molecular clouds that form in the high pressure environment of starbursts have to be very dense in order to exist. starbursts have to be very dense in order to exist.

Second: Second: SIZES – Zepf et al. 99 found little or no correlation between SIZES – Zepf et al. 99 found little or no correlation between size (radius) and mass (size (radius) and mass (r r M M0.1±0.10.1±0.1) ) for young clusters in NGC for young clusters in NGC 3256 . But virialized clouds have 3256 . But virialized clouds have r r M M1/21/2 P P-1/4 -1/4

This is observed for molecular clouds in the galaxy, and hard to This is observed for molecular clouds in the galaxy, and hard to avoid for virialized clouds. avoid for virialized clouds. So So how do you erase the how do you erase the r r M M1/21/2 ??Not easy! Best hope seems to be a star formation efficiency that is Not easy! Best hope seems to be a star formation efficiency that is dependent on the Binding Energy of the parent cloud. In this case, dependent on the Binding Energy of the parent cloud. In this case, low mass clouds are inefficient, lose mass, and expand. Fine line to low mass clouds are inefficient, lose mass, and expand. Fine line to keep numbers of low mass GCs around. keep numbers of low mass GCs around. See AZ01 for details!See AZ01 for details!

Angular Momentum in GalaxiesAngular Momentum in Galaxies• Where is the angular momentum in elliptical Where is the angular momentum in elliptical

galaxies?galaxies?

• General idea – protogalaxies torqued up by tidal General idea – protogalaxies torqued up by tidal interactions with other protogalaxies, have ainteractions with other protogalaxies, have a dimensionless spin parameter dimensionless spin parameter 0.05 . 0.05 .

Goes back to Hoyle, confirmed in modern Goes back to Hoyle, confirmed in modern cosmological simulations, mostly independent of cosmological simulations, mostly independent of mass and environment.mass and environment.

•• Halos to galaxies – Baryons that make up the parts Halos to galaxies – Baryons that make up the parts of the galaxies we see cool, collapse, and spin up. of the galaxies we see cool, collapse, and spin up. Spin-up works to zeroth order for spirals.Spin-up works to zeroth order for spirals.

What about Balmer Lines?What about Balmer Lines?Natural first step - carried out forNatural first step - carried out for

- M87 GCs by Cohen et al- M87 GCs by Cohen et al- NGC 1399 GCs Kissler-Patig et al, Forbes et al.- NGC 1399 GCs Kissler-Patig et al, Forbes et al.- NGC 4472 GCs by Beasley et al- NGC 4472 GCs by Beasley et al

BUTBUT

Challenges with calibration for Galactic GCs - when the Challenges with calibration for Galactic GCs - when the same techniques used for extragalactic GCs are applied same techniques used for extragalactic GCs are applied to metal-rich Galactic GCs, get ages ~25% older than to metal-rich Galactic GCs, get ages ~25% older than CMD ages (e.g. 47 Tuc, Gibson et al, Vazdekis).CMD ages (e.g. 47 Tuc, Gibson et al, Vazdekis).

Also requires a long time on a 8/10-m telescope to get Also requires a long time on a 8/10-m telescope to get reasonable signal, so even when systematics are sorted reasonable signal, so even when systematics are sorted out it is a painful way to go.out it is a painful way to go.

Dynamical InformationDynamical Information

Velocities for 144 GCs around Velocities for 144 GCs around NGC 4472 NGC 4472

(Zepf et al. 2000, also (Zepf et al. 2000, also Beasley et al. 2000, Beasley et al. 2000,

Sharples et al 1998, Cote et Sharples et al 1998, Cote et al. 2003)al. 2003)

• • These data extend to ~ 8´, These data extend to ~ 8´, factor of 4 larger than factor of 4 larger than previous velocity data.previous velocity data.

(half-light radius of galaxy (half-light radius of galaxy light is 1’ ~4 kpc, so 8’ ~32 light is 1’ ~4 kpc, so 8’ ~32 kpc) kpc)

• • New FLAMES data, another New FLAMES data, another 100 GCs to ~ 15’100 GCs to ~ 15’

Which is the bimodal Milky Way?Which is the bimodal Milky Way?

• • One plot is the color One plot is the color distribution of the Galaxy distribution of the Galaxy GCS, the other is NGC GCS, the other is NGC 4406, a modestly bimodal 4406, a modestly bimodal elliptical galaxy GCS – elliptical galaxy GCS – which one is which?which one is which?

• • Milky Way GCS known Milky Way GCS known to be bimodal directly in to be bimodal directly in metallicity.metallicity.

•• Given bimodal Milky Given bimodal Milky Way metallicity Way metallicity distribution, can NGC distribution, can NGC 4406 and most other 4406 and most other ellipticals be so different?ellipticals be so different?

Plot from Katherine Rhode, data Rhode & Zepf 2004Plot from Katherine Rhode, data Rhode & Zepf 2004

Which is the bimodal Milky Way?Which is the bimodal Milky Way?

• • One plot is the color One plot is the color distribution of the Galaxy distribution of the Galaxy GCS, the other is NGC GCS, the other is NGC 4406, a modestly bimodal 4406, a modestly bimodal elliptical galaxy GCS – elliptical galaxy GCS – which one is which?which one is which?

• • Milky Way GCS known Milky Way GCS known to be bimodal directly in to be bimodal directly in metallicity.metallicity.

•• Given bimodal Milky Given bimodal Milky Way metallicity Way metallicity distribution, can NGC distribution, can NGC 4406 and most other 4406 and most other ellipticals not be similar?ellipticals not be similar?

Plot from Katherine Rhode, data Rhode & Zepf 2004Plot from Katherine Rhode, data Rhode & Zepf 2004

• • For mostly old systems, color traces For mostly old systems, color traces metallicity, use Milky Way and metallicity, use Milky Way and models to do this (age-met models to do this (age-met degeneracy still present).degeneracy still present).

• • Can’t get the two peaks in the Can’t get the two peaks in the observed colors from a single-observed colors from a single-peaked metallicity distribution.peaked metallicity distribution.

GCs come in two metallicity GCs come in two metallicity groups .groups .

•• Metal-rich GCs - closely tied to Metal-rich GCs - closely tied to bulk of host galaxy - trace galaxy bulk of host galaxy - trace galaxy formation/assembly. formation/assembly.

•• Metal-poor GCs - Low metals, Metal-poor GCs - Low metals, extended spatial distribution, and extended spatial distribution, and old ages in Milky Way halo - old ages in Milky Way halo - constraints on early structure constraints on early structure formation? formation?

Note this division in abundance also Note this division in abundance also seen in Galaxy GC systemseen in Galaxy GC system

Color and Metallicity DistributionsColor and Metallicity Distributions