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Constraints on Secular Evolution from Star Clusters in Spirals and Lenticulars

Constraints on Secular Evolution from Star Clusters in Spirals and Lenticulars. Jean P. Brodie UCO/Lick Observatory University of California Santa Cruz. S tudy of A strophysics of G lobular clusters in E xtragalactic S ystems.

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Constraints on Secular Evolution from Star Clusters in Spirals and Lenticulars

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  1. Constraints on Secular Evolution from Star Clusters in Spirals and Lenticulars Jean P. Brodie UCO/Lick ObservatoryUniversity of California Santa Cruz Study of Astrophysics of Globular clustersin Extragalactic Systems P. Barmby (CfA), M. Beasley (UCSC), K. Bekki (UNSW), J. Cenarro (UCSC/U Madrid), L. Chomiuk (UCSC), D. Forbes (Swinburne), J. Huchra (CfA), S. Larsen (ESO), M. Pierce (Swinburne), R. Peterson (UCSC), R. Proctor (Swinburne), J. Howell (UCSC), L. Spitler (UCSC), J. Strader (UCSC)

  2. Overview Galaxy Formation • Background: Globular clusters and their relevance to galaxy formation • Global properties of GC systems in early and late-type galaxies • Bimodal color distributions and implications for GC/galaxy formation • Constraints on secular evolution from GC ages, metallicities, specific frequencies and correlations with host galaxy properties Lenticular Galaxies • Faint Fuzzies: discovery and characteristics • Ideas on formation • Signposts for secular evolution?

  3. What are Globular Clusters? M 13 • SSPs – single ageand metallicity • 105– 106 Msun • All galaxies MV<–15 have at least one GC • ~150 in MW~400 in M31> 10,000 in some ellipticals • SNNGC  100.4(Mv+15), 2 – 3  greater in E’s

  4. Constraining galaxy formation • Associated with galaxies of all morphological types• Constrain theories of galaxy formation and evolutionWhen and how?Differences

  5. Good tracers of star formation histories of galaxies • Massive star clusters form during all major star formation events (Schweizer 2001) • #of young clusters scales with amount of gas involved in interaction (Kissler-Patig et al 1998) • Cluster formation efficiency depends on SFR in spirals(Larsen & Richtler 2000) NGC 6946 Larsen et al 2001

  6. Bimodal Color Distributions Bimodal color distributions globular cluster sub-populations Color differences are due toage differencesand /ormetallicity differences Multiple epochs and/or mechanismsof formation [Fe/H] = -1.5 -0.5 V-I = 0.95 1.15

  7. GC/Galaxy Formation Models 1. Formation of ellipticals/GCs in mergers (Schweizer 1987, Ashman & Zepf 1992) 2.In situ/multi-phase collapse(Forbes, Brodie & Grillmair 1997) 3.Accretion/stripping(Cote’ et al. 1998) 4. Hierarchical merging(Beasley et al. 2002)2 & 4 require (temporary) truncation of GC formation at high redshift z

  8. GC Ages • Increasing evidence that bothred and blue globular clusters are very old (>10 Gyr) • Small percentage of red globular clusters may be young • Ellipticals/Lenticulars: NGC 1399 (Kissler-Patig, Brodie, Schroder et al. 1998; Forbes et al 2001) M87 (Cohen, Blakeslee & Ryzhov 1998) NGC 4472 (Puzia et al 1998; Beasley et al. 2000) NGC 1023 (Larsen & Brodie 2002) NGC 524 (Beasley et al 2003) NGC 3610 (Strader, Brodie et al 2003, 2004) NGC 4365 (Larsen, Brodie et al 2003) NGC 1052 (Pierce et al 2004) NGC 7457 (Chomiuk, Strader & Brodie 2004) + PhD theses of T. Puzia and M. Hempel • Spirals:M 31 (Barmby et al. 2000; Beasley, Brodie et al 2004) M 81 (Schroder, Brodie, Huchra et al. 2001) M 104 (Larsen, Brodie, Beasley et al 2002)

  9. Constraint # 1 • Old ages of both sub-populations Inconsistent with major merger picture Relevance to Secular Evolution? Read on!

  10. Color-Magnitude Diagrams • Average blue peak color (V–I)o=0.95 0.02 • Average red peak color (V–I)o=1.18 0.04[Fe/H]= – 1.4, –0.6 (Kissler-Patig, Brodie, Schroder et al. 1998 AJ)

  11. Milky Way Peaks at [Fe/H] ~ – 1.5 and – 0.6 (Zinn 1985) MW GCs are all old

  12. Sombrero Peaks at (V–I)0=0.96 and 1.21Larsen, Forbes & Brodie (MNRAS 2001) Follow-up spectroscopy at Keck indicates vast majorityof GCs (both red and blue) areold(~13 Gyr) Larsen, Brodie, Forbes (2002)

  13. GCs and Galaxy Assembly • Colors of bothreds and blues correlate with galaxy mass (MV and )and colorBlue relationdifficult to explain under accretion/major merger scenariosConstraints on Hierarchical Merging Paradigm from ages of GCs in dwarfs(~12 Gyr) Brodie 2001; Larsen, Brodie et al 2001; Strader, Brodie & Forbes 2004

  14. Spirals fit the trend Red GC relation has same slope as galaxy color relation  Red GCs and galaxy stars formed in the same star formation event Metal-rich GCs in spirals and ellipticals have the same origin —they formed along with the bulge stars . Brodie & Huchra 1991; Forbes, Brodie & Grillmair 1997; Forbes, Larsen & Brodie 2001; Larsen, Brodie, Huchra et al 2001

  15. Constraints # 2 • Similarities between peak colors in spirals and ellipticals Hints at universal GC formation processes • Slope of red GC color vs galaxy mass relation is same as galaxy color vs galaxy mass relation (true for spirals and ellipticals) Red GC formation is linked to formation of bulge

  16. Bulge GCs Number of metal-rich GCs scales with the bulge Forbes, Brodie & Larsen ApJL (2001)

  17. Numbers/Specific Frequency  Metal-rich GCs in spirals are associated with bulgenot disk # bulge(red/MR) GCs scales with bulge luminosity # red GCs/unit bulge light = bulge SN ~1 The totalSN for field ellipticals is 13 (Harris 1991)  The fraction of red GCs in ellipticals is about 0.5  The bulge SNfor field ellipticals is~1  Spirals and field ellipticals have a similar number of metal-rich GCs per unit (bulge) starlight

  18. Specific Frequency • SN(total) constant at ~0.55 for spirals with B/T≤0.3 (Sb and later) • Constant number of GCs formed in late-type spirals • Universal old halo population • SN (total) ~2 for “field” Es • If higher SNfor Es due to “extra” GCs formed with bulge, expect SNto scale with B/T from ~0.55±0.25 at B/T=0 to ~1.9±0.5 at B/T=1 3957 2.0 SN • 1.0 • • 0.5 M51 • • 0.8 0.2 B/T Goudfrooij et al 2003 Chandar et al 2004

  19. Exceptions  Secular Evolution? • NGC 3628: InteractingHI tidal plume + bridge connection with NGC 3627 – extra GCs formed in interaction? • NGC 7814: Best evidence?Least luminous sample galaxy (5 x less than NGC 4594). Satellite-to-main galaxy mass ratios of 10% more common for low mass galaxies(Goudfrooij et al 2003) • M 51: Does it have a bulge?Interacting with NGC 5195Too few “bulge” (MR) GCs? (uncertain estimate)16 vs 98 (bulge/disk deconvolution) or 16 vs 45 ( – BH mass)(Chandar et al 2004)

  20. Constraints #3 • Number of metal-rich GCs scales with the bulge luminosity • Specific frequency as function of B/T broadly consistent with universal halo (blue) GC population + “extra” (red) GC population formed with bulge

  21. Conclusions 1) Number of metal-rich GCs scales with the bulge luminosity 2) Chemical evidence also suggests that metal-rich GC formation closely linked tobulge formation 3) Metal-rich GCs are old 1),2) & 3) argue against secular evolution However, exceptions allow for bulge build-up by secular evolution  Galaxies of similar morphological type can have different formation histories

  22. Lenticular Galaxies Faint Fuzzies Collaborators:Andi Burkert, Soeren Larsen • HST program to study GCs in NGC 1023 (MB= –20) • Nearby (10 Mpc) S0 galaxy Faint endof GCLF Brodie & Larsen 2002Larsen & Brodie 2000

  23. NGC 1023 GCLF • Faint wing of NGC 1023 GCLF deviates significantly from Milky Way GCLF • 3rd population of clusters in addition to normal compactred and blue GC sub-populations

  24. GC Selection • Typical GC Reff =2–3 pc • 29 objects in NGC 1023 with Reff>7 pc • Almost all are red

  25. Spatial Distribution • Background cluster of galaxies ruled out • Extended objects have annular distribution corresponding to galaxy isophotes

  26. Search for other Faint Fuzzies • FFs detectable in 4 galaxies (3S0s, 1E) in HST WFPC2 archive • Found in 2: N 1023, N 3384 (both SB0s in groups) • Ruled out in 2: N 3115 (S01, isolated), N 3379 (E) ACS data……

  27. Keck Spectroscopy • NGC 1023 “master”spectrum <[Fe/H]>FF1023=–0.58±0.24 represents 133 hours of 10-m telescope time • NGC 3384 - 30 hours <[Fe/H]>FF3384=–0.64±0.34 Brodie & Larsen AJ 2002

  28. Velocities • NGC 1023 <VFF>=559±64 km/s Vgal=601 km/s • NGC 3384 <VFF>=768±79 km/s Vgal=704 km/s • FFs are ~2 bulge Reff from center disk not bulge objects

  29. Ages • FFs are mostly likely ~ 13 Gyr old and not younger than ~ 7–8 Gyr • Stable against disruption

  30. New Kind of Cluster? Globular Clusters NGC 1023 Milky Way Open clusters are smaller, younger and less massiveNo MW objects correspond in metallicity, luminosity and size

  31. Origins • FFs have no analogs in MW or elsewhere in LG • Found exclusively in lenticulars (so far) • Is the mechanism responsible for the formation of FFs linked to the mechanism for forming lenticulars?

  32. Distribution and Kinematics • Distribution of VFF not same as galaxy rotation curve • FFs located in a ring with radius ~1.5’ (4-5 kpc) and Vrot 200 km/s • Tidal radius 48 pc

  33. Extended Cluster Formation • Simulations of Geyer & Burkert (2003, 2004) form bound clusters with sizes and masses of FFs in GMCs if star formation occurs with a density threshold • Under what circumstances do these special star-forming conditions occur? 1. Galaxy-galaxy interations? e.g. Cartwheel 11 2. Resonance rings and secular evolution

  34. Faint Fuzzies Signposts for secular evolution? • NGC 1023 and NGC 3384 are barred • NGC 3115 is not • B ~3.5 kpcin NGC 1023 (Debattista et al 2002) • Bulge is red (old, MR) • Kinematically and chemically decoupled nuclear disk (stars ~ 7 Gyr)

  35. NGC 3081 Buta et al (2004) • MB=20 early-type (S0/a, Sa) barred spiral (bulgeless) • Inner ring encircles bar at ~5 kpc • ~58 blue (young) clusters in ring with MV <9 (V<23.6) Typical cluster effective radius ~11 pc ! • Will these clusters survive? • Is bar formation important in forming lenticular galaxies?

  36. Implications If FF formation is linked to bar formation in disk galaxies  Disks and bars were present in galaxies at high redshift (z >2)

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