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Formation of Galaxies in Clusters

Formation of Galaxies in Clusters. Myung Gyoon Lee Seoul National University Astronomy Program, SEES 2004. 10.28-29 The 1st KIAS International Workshop on Cosmology and Structure Formation, Seoul. (Abell 2255 from SDSS). Prelude. Formation of Clusters & Large Scale Structures

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Formation of Galaxies in Clusters

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  1. Formation of Galaxies in Clusters Myung Gyoon Lee Seoul National University Astronomy Program, SEES 2004. 10.28-29 The 1st KIAS International Workshopon Cosmology and Structure Formation, Seoul (Abell 2255 from SDSS)

  2. Prelude • Formation of Clusters & Large Scale Structures • Can be described by only mass and gravity • A simple model of hierarchical merging in CDM cosmology • Formation of Galaxies • What is a galaxy? ->a system of mass+gas+stars embedded in DM halos, showing diverse morphological kinds. • We need to explain both mass assembly & star formation history. • Not a simple problem • A longstanding, but still intriguing & exciting problem

  3. Today • Formation of Galaxies in Clusters • Focusing on massive early-type galaxies in clusters 1. Overview of recent progress: two examples 2. Introducing our work 1) Globular Clusters in gEs of the Virgo cluster 2) Age and metallicity of Es in nearby clusters 3) Kinematics of galaxies in nearby clusters 4) Early-type galaxies in the GOODS/ACS field 3. Our plan with SDSS data 4. Summary

  4. Galaxy Clusters • Galaxy clusters are the largest gravitationally bound system, composed of 102-103 galaxies. • Catalogs: A few examples • Abell (1958), Abell et al (1989): 4073 for all sky of PSS • Bahcall et al (2003): 799 (53 Abell clusters+ new) from early SDSS data (more to come) • Bohringer et al (2004): 447 from REFLEX cluster survey • Recent Refs • Rosati etal (2002) The Evol of X-ray Clusters of Galaxies, ARAA, 40, 539 • Mulchay et al (2004) Clusters of Galaxies: Probes of Cosmoloigcal Struc and Gal Evol • Voit (2004) Tracing Cosmic Evolution of Clusters of Galaxies, Rev.Mod.Phys.

  5. Why galaxies in clusters? • Member galaxies at the same distance • Easily identified in the sky • A cluster occupies a small region in the sky. • Abundant with early type galaxies (<-> LG) • We can study environmental effects on galaxies.  Clusters are ideal to investigate the formation & evolution of galaxies and clusters.

  6. Recent Progress: Two examples • 1) Nearby galaxies at 0.08< z<0.12 • 2) A sample of clusters at 0.3<z<1.0

  7. CMREnvironments • Hogg et al (2004 ApJ,601,L29): 55,158 SDSS galaxies at 0.08<z<0.12 (see also Blanton et al 2003, ApJ, 594, 186) • (Results) • Bulge-dominated(Sersic n>2) galaxies show much redder and much narrower than disk-dominated galaxies(n<2). • More bulge galaxies in the higher density regions. • CMR almost independent of density (d(g-r)<0.02)!! • Corresponding to a change in age or metallicity <20%.  Random merger of low L galaxies->a large spread • However, need to look at wider colors !

  8. Cluster Galaxy Evolution up to z=1 • Andreon et al (2004, MN, 353, 353) (Kodama et al 1998, Stanford et al 1998) • Colors and LF of 24 clusters at 0.3<z<1 (mostly X-ray clusters) • Consistent with the presence of two populations: • 1) CMR of the brightest galaxies -> old systems formed at zf=2-5 • 2) m* in LF-> younger systems showing more recent SF at zf<1.

  9. Our Studies (2004) Primary goal: Understanding the formation & evolution of galaxies from z=0 to high z. 1) Globular Clusters in gEs of the Virgo cluster 2) Formation of Galaxies in Nearby Abell Clusters 3) Kinematics of Galaxies in Nearby Abell Clusters 4) Early-type Galaxies in the GOODS/ACS Field Our team: Hong Soo Park, Ho Seong Hwang, Tae Hyun Kim, Joon Hyeop Lee and more

  10. 1. Virgo Cluster • D=15 Mpc, z=0.0039 • The nearest cluster including the Local Group. • Irregular (dynamically young), low mass cluster . • Ideal to study in detail the stars and clusters in gEs.

  11. Virgo Map

  12. Virgo gEs M87 M47 M60 M86 NGC 4636 M84

  13. Virgo gEs • Virgo gEs

  14. GCs in M49 (gE)

  15. CMD-wide field • Observations • KPNO4m+PFCCD • 16’x16’ • Geisler,Kims,Park,Lee • Washington filters CT1 (efficient for EGCs) • Three kinds • GCs (BGC, RGC) • galactic stars • background galaxies (Lee et al 04) BGCRGC

  16. Color distribution • Variety with d[color]=const • N(BGC)/N(RGC) varies depending on gEs (Lee et al 03)

  17. GC-Host galaxies • Color, velocity dispersion, Mv, Mg2 (Lee 2003) • Strong correlations between RGC and stellar halo, • No for BGC • RGCs follow the stellar halo, but BGCs do not!!!!

  18. Models for gE formaton • How gEs formed? • Two competing models: 1) Monolithic Collapse Models (MCM): old soldiers never die. (Eggen, Lynden-Bell, Sandage 1962: MW Halo) (Partridge & Peebles 1967, Tinsley 1972, Larson 1974, Chiosi & Carraro 2002) 2) Hierarchical Merging Models (HMM) : current paradigm (Toomre 1977, Searle & Zinn 1978, Kauffmann et al 1993, Steinmetz & Navarro 2002)

  19. Formation of gEs from GCs • When & How long BGC, RGC, gE formed? • BGCs formed at 12.5G • RGCs+gE* formed at 10.5 G • How they formed? • HMM+MCM • With HMM making gE at z>2! (current models) • With rapid chemical enrichment

  20. 2. CMR of Nearby Clusters

  21. A photometric study on the formation of galaxies in nearby galaxy clusters Tae Hyun Kim , Myung Gyoon Lee Seoul National University KAS Meeting 2004 Fall

  22. Observation& Data • BOAO (June 2~5, 2003), B,V,I • 2MASS Extended Source Catalog, Ks • Objects KAS Meeting 2004 Fall

  23. Color-Magnitude Relation A1656 (Coma)

  24. Color-Magnitude Relation No significant evolutions in slope, scatter, zero points

  25. Color-Magnitude Relation Brighter galaxies have redder color. • What makes galaxies red ? • Age & Metallicity  ’Age-metallicity degeneracy’ • How to break it? With NIR band color Which is less sensitive to age. • Combining Optical & NIR color Break ‘Age-metallicity-degeneracy’

  26. CCD SSP Models • Age : major recent SFH Bruzual & Charlot(2003) Kurth(1999) Age, [Fe/H]: relativeVarious combinations of • Stellar library • Evolutionary track • IMF Vazdekis(1999) Worthey(1994)

  27. Model Comparison BC2003 Worthey1994 KAS Meeting 2004 Fall

  28. 2 Gyrs >10 Gyrs

  29. Summary • Early type galaxies in each cluster show a large spread in age and metallicity. • Luminosity weighted mean ages range in narrow region, 5~7Gyrs • Luminosity weighted mean [Fe/H] is 0.09~0.56. KAS Meeting 2004 Fall

  30. 2.1 Clusters with SDSS data Abell 168 Abell 2199 Abell 2255

  31. Photometric Data with SSP model of Bruzual & Charlot 2003 Spectroscopic Data with SSP model of Bruzual & Charlot 2003 Comparison with Phot & Spec

  32. Abell 168, Abell 119

  33. Abell 2199, Abell 2255

  34. Averages of galaxies • Compared with BOAO results.

  35. 3. Kinematics of Abell 2255

  36. Abell 2255 • Massive (vel disp=1221 km/s) • z=0.0808 (d=300 Mpc) • Two cDs (dv=2600km/s)-> merging? [Burns et al 1995] • X-ray peak off from the optical peak [SDSS DR2]

  37. Goals From the velocity data of galaxies in rich galaxy clusters, we will derive ; • Basic kinematics : Rotation, Velocity dispersion • Finding Substructure • The orbits of different types of galaxies in galaxy clusters  Understanding the formation and dynamical evolution of galaxy and galaxy clusters.

  38. Membership of Abell 2255 • Asymmetric

  39. D-S plot for A2255 • D-S Delta (differences in v and v dispersion. Dressler & Schechtman 1988)-circle sizes • Found one small substructure!

  40. X-ray vs Number density

  41. Morphological class • Criteria: image+spectra (templates: Strateva et al 2001) 268=166 Early + 47 Int + 55 Late

  42. SB Profiles & Concentration parameter

  43. Spatial distribution • Early types show strong central concentration. • A small substructure show mostly early types.

  44. V vs mag & color • Some difference of velocity spread depending on colors.

  45. V vs radius & PA • Velocity dispersion decreases with R. • Rotation is not clearly seen.

  46. Discussion • To be compared with numerical simulation

  47. B<25 4. GOODS/ACS red: early (C>3 &A<0.3), blue:late-type (C<3 &A>0.3), green: intermediate, black: no class • Concentraton : (80% light radius)/(20% light radius) • Rotational asymmetry : ½ (∑ ((pixel value) – (180o rotated pixel value)) / ∑ (pixel value))

  48. Evolution of Early types - Simple Stellar Population (SSP; star forming as delta function) - Single Burst (constant star forming for early 1Gyr) - Exponentially Decreasing (exponentially decreasing SFR with scale time 1Gyr) - Linearly Decreasing (linearly decreasing SFR with SFR=0 at 10Gyr) - Constant Star-Formation (constant SFR = 1 M⊙/yr)

  49. Red (c>3), z=0.8-1.0 Blue (c>3) Blue (c<3), z=1.0-1.2 Red (c<3)

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