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Galaxy Formation in Today ’ s Cosmology

Galaxy Formation in Today ’ s Cosmology. Myung Gyoon Lee Astronomy Program, SEES Seoul National University (KPS meeting, Oct 23, 2004). Contents. Today ’ s cosmology Large Scale Structures (LSS) How massive galaxies formed Today ’ s unsolved mysteries. Today ’ s Cosmology.

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Galaxy Formation in Today ’ s Cosmology

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  1. Galaxy Formation in Today’s Cosmology Myung Gyoon Lee Astronomy Program, SEES Seoul National University (KPS meeting, Oct 23, 2004)

  2. Contents • Today’s cosmology • Large Scale Structures (LSS) • How massive galaxies formed • Today’s unsolved mysteries

  3. Today’s Cosmology • SN Ia (1998-) ⇒ accelerating universe • HST H0 (2001) ⇒ H0 =71km/s/Mpc • WMAP CMBR (2003-) ⇒ precise parameters • Decoupling: z=1089 (t=380000 y) • Reinonization: z~20, (t~180My) • Million galaxies survey (SDSS,2dFGRS) ⇒ LSS • z<0.03 • Today’s universe model: Dramatic changes in 5 y • Dark matter: ~90% ⇒ 23% • Dark energy: 0% ⇒ 73% • Ordinary matter: ~10% ⇒ 4% • Age of the Universe: 12-15Gyr ⇒ 13.7 Gyr • Flat universe consistent with inflation (Spergel et al 2003, Tonry e tal 2003,Tegmark et al 2004)

  4. Time • Human evolution: time • Cosmological evolution: time (MWG) & redshift (measurable)

  5. Star map-MWG • 0.5B stars, 2MASS JHK(1.2,1.6,2.2 um)

  6. Galaxy map-LSS 1.6M galaxies 2MASS, JHK (Jarrett etal)

  7. 3D LSS-2dFGRS • 2dF Galaxy Redshift Survey (UK-Australia)

  8. LSS-2dFGRS 0.25M galaxies

  9. LSS-Walls Gott et al (2003) Great Walls of galaxies (SDSS, CfA2)

  10. LSS formation models • Current paradigm:CDM-Hierarchical Merging models • Bottom up process of formation - early small fluctuations of baryons and CDM ⇒ small dark-halo galaxies ⇒ formation of stars in the center of dark-halos ⇒ large galaxies ⇒ clusters of galaxies ⇒ LSS Successful for CMBR, LSS, and clusters. However, several problems in galactic scales. (Freeman 2003, Lee 2003, Glazebrook et al 2004) Abraham & van den Bergh(2001)

  11. Realm of Galaxies (Various kinds) • Spirals • S0s • Ellipticals • Dwarf spheroidal galaxies (107- 109 Mo) • Giant Es, cDs (1012 Mo) • Irregular/peculiar galaxies • Normal  interacting /merging • Field  cluster galaxies • AGN

  12. Galaxies(z)-evolutionAbraham(2001)

  13. Giant E Galaxies • Abundant in rich clusters

  14. M49

  15. Models for gE formaton • Two competing models: 1) Monolithic Collapse Models (MCM) (Eggen, Lynden-Bell, Sandage 1962: MW Halo) (Partridge & Peebles 1967, Tinsley 1972, Larson 1974, Chiosi & Carraro 2002: gEs) 2) Hierarchical Merging Models (HMM) (Toomre 1977, Searle & Zinn 1978, Kauffmann et al 1993, Steinmetz & Navarro 2002)

  16. MCM for gE formaton • Monolithic collapse models (MCM) • Es formed as a result of large proto-galactic clouds collapsing and forming stars in a very short time (108 y) very early (at z>3). • After the violent burst of star formation leading to high metallicity very early, these galaxies evolved quiescently until today (passive evolution) • Single collapse models, Multi collapse models

  17. HMM for gE • Hierarchical merging models (HMM) • Toomre(1977) proposed that Es formed when two spirals merged. Searle & Zinn (1978) suggested that the halo of our Galaxy might have formed via accreting transient proto-galactic fragments with dwarf galaxy-mass for an extended period of time. • Later these were developed into hierarchical merging (clustering) models in the context of cold dark matter (CMD) of structure formation • Small objects formed first, then are progressively incorporated in to a larger structure, and stars form at the baryonic cores embedded in the dark matter halo. • Massive Es formed much later (~half at z<1) and longer. • Major merging (of large galaxies) and minor merging (accretion/tidal stripping of small ones)

  18. HMM(2002) Steinmetz (2002) Time sequence of structure formation in a hierarchical clustering universe ( CDM) z= 9 3.5 1 0 (size=50Mpc)

  19. HMM(2002) All old star young star gas • Steinmetz(2002) • gE formed at z=0.27!! z=4 3.5-2.7 1.8 Disk g 1.8-0.8 0.7-0.3 gE

  20. Problems of CDM models 1 • Local Group dwarfs (Moore et al 1999) • CDM models require ~500 dwarfs • Obs ~30 dwarfs • Galaxy halo centers • CDM predicts a steeply cusped power law in density distribution • Obs ~dark halos have a central core of nearly constant density

  21. Problems of CDM models 2 • Massive galaxy formation epoch from stars • Merging galaxies at z>2 in the HDFN are the most luminous & massive galaxies (Conselice 2003,2004) • IR obs showed the existence of significant number of massive galaxies at z>1 (Bertha et al 2004).

  22. More inVirgo gEs M87 M47 M60 M86 NGC 4636 M84

  23. Extragalactic Star Clusters • Formation and evolution of star clusters • Formation and evolution of galaxies M80 M49

  24. BGC & RGC • Three kinds • GCs (BGC, RGC) • galactic stars • background galaxies (Lee et al 04) BGCRGC

  25. Answers? • 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 • An unsolved mystery!

  26. GOODS/UDF (2004.5)-more The Great Observatories Origins Deep Survey -HST, Chandra, Spitzer IR SpaceTelescope, XMM-Newton+ground-based telescopes -from IR to X-ray -wider, as deep as HDFN and CDFS HST Ultra Deep Field (UDF) -ACS, NICMOS, etc -~1mag deeper than HDFN

  27. UDF-The deepest U

  28. UDF-Optical

  29. UDF-Details

  30. UDF-NIR

  31. Summary • Formation of massive galaxies is still an unsolved mystery. • CDM HMMs work well for the formation of large scale structures, but are inconsistent with some recent obs. • gEs might have formed early , not by a single process, but by several mechanisms (“star formation first, and then mass assembly” has also a problem). • Need new ideas, better data, and better models. • In particular, precise age dating of stars and clusters in nearby gEs, and redshift dating of distant Es are needed to find when they formed.

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