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Galaxy Bi-modality: Cold Flows, Clustering and Feedback

This lecture explores the observed bi-modality in galaxy properties, such as color, star formation rate, and bulge/disk ratio, and discusses the role of cold flows, clustering, and feedback processes in shaping galaxy formation and evolution. It also examines the origin of the bi-modality and its dependence on environmental factors.

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Galaxy Bi-modality: Cold Flows, Clustering and Feedback

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  1. Lecture On the Origin of Galaxy Bi-modality: Cold Flows, Clustering and Feedback • Observed bi-modality • Shock heating vs cold flows • Cold filaments in hot halos -- clustering scale • Feedback Processes • Origin of the bi-modality

  2. 1. Observed Bimodality

  3. Observed Scale • bi-modality/transition at M*~3x1010Mʘ ~L* below: disks, blue, star forming, low Z, LSB, M/L decreasing with M along a “fundamental line”, in field (small halos), … above: spheroids, red, old-pop, high Z, HSB, M/L increasing with M, “fundamental plane”, clustered (massive halos), AGNs, … Mhalo ~6x1011Mʘ • very blue galaxies → bursty star formation • big blue galaxies at z~2-3 (e.g. SCUBA) → early star formation in big objects • luminous red galaxies at z~0-1 (e.g. EROs) → early star formation, then shut off

  4. Bi-modality in color, SFR, bulge/disk 0.65<z<0.75 E/S0/Sa Disks and Irregulars M*crit~3x1010Mʘ Bell

  5. Luminosity function: Red vs Blue M*crit~3x1010Mʘ M* SDSS Baldry et al. 04

  6. Transition Scale Bulge/Disk Surface Brightness HSB spheroids LSB disks M*crit~3x1010Mʘ M*crit~3x1010Mʘ SDSS Kauffmann et al. 03

  7. Transition in Metallicity M*crit~3x1010Mʘ SDSS Tremonti et al.

  8. Bi-modality: Age vs Stellar Mass young old young old M*crit~3x1010Mʘ SDSS Kauffmann et al. 03

  9. Bi-modality in Color-Magnitude SDSS Baldry et al. 04

  10. Color-Magnitude-Morphology in SDSS

  11. Color-Magnitude bimodality & B/D depend on environment ~ halo mass environment density: low high very high disks spheroids Mhalo<6x1011 “field” Mhalo>6x1011 “cluster” SDSS: Hogg et al. 03

  12. Color - Environment

  13. Age & Color bi-modalily correlated with environment density, or halo mass Mhalo<6x1011 “field” Mhalo>6x1011 “cluster” spheroids, old disks, young Kauffmann et al. 2004

  14. Color-Magnitude Bimodality depends on B/D and Environment density: low high very high disks spheroids SDSS: Hogg et al. 03

  15. Bi-modality at high z Combo-17

  16. Mass versus Light Distribution halo mass galaxy stellar mass 40% of baryons

  17. <M/L> vs M for halos in 2dF assuming ΛCDM M/L 10 11 12 13 14 M Using conditional luminosity function: Van den Bosch, Mo, Yang 03

  18. Emission Properties vs. Stellar Mass low-mass emission galaxies are almost all star formers high-mass emission galaxies are almost all AGN Kauffmann et al. 2004

  19. Observed Characteristic Scale bi-modality / transition M*~3x1010Mʘ Mvir~6x1011Mʘ Vvir~120 km/s discs, blue star-forming, low Z, LSB M/L∝M-1, fundamental line, small halos (field) spheroids, red old-pop, high Z, HSB M/L∝M, fundamental plane, massive halos (clustered), AGNs

  20. Theory

  21. Consider a spherical cow…

  22. Standard Picture of Infall to a Disc Rees & Ostriker 77, Silk 77, White & Rees 78, … Perturbed expansion Halo virialization Gas infall, shock heating at the virial radius Radiative cooling Accretion to disc if tcool<tff Stars & feedback M<Mcool~1012-13M⊙

  23. Cooling rate T-1 Line emission Bremsstrahlung 2  2 N    1 - 1 - - ( ) [erg g s ] / molecules per g e per particle A q T N   A  2

  24. Cooling vs Free Fall Blumenthal, Faber, Primack & Rees 86 Rees & Ostriker 77, Silk 77, White & Rees 78 T 104 105 106 107 +3 +1 galaxies Brems. log gas density CDM -1 clusters tcool<tff upper bound too big H2 -3 He -5 H 10 30 100 300 1000 virial velocity

  25. 2. Shock-Heating vs Cold Flows 8

  26. Formation of a Cluster – Different Components

  27. Growth of a Massive Galaxy T °K 1012Mʘ 1011Mʘ shock-heated gas “disc” Spherical hydro simulation Birnboim & Dekel 03

  28. A Less Massive Galaxy T °K 1011Mʘ shocked cold infall “disc” Spherical hydro simulation Birnboim & Dekel 03

  29. Hydro Simulation: ~Massive M=3x1011 Kravtsov et al. z=4 M=3x1011 Tvir=1.2x106 Rvir=34 kpc virial shock

  30. Less Massive M=1.8x1010 Kravtsov et al. virial radius cold infall z=9 M=1.8x1010 Tvir=3.5x105 Rvir=7 kpc

  31. Mass Distribution of Halo Gas disk cold flows density shock- heated adiabatic infall Temperature Analysis of Eulerian hydro simulations by Birnboim, Zinger, Dekel, Kravtsov

  32. Shock Stability (Birnboim & Dekel 03): post-shock pressure vs. gravitational collapse stable: ln P     adiabatic: Birnboim & Dekel 03          4 / 3 ln   s with cooling rate q (internal energy e):    V P e     t (ln ) 5 5 d P q comp t       eff  (ln ) 3 21 d e  cool q   3 e T ( 21 4 R   2 T 4 t V s t       cool post pre comp   , ) 16 q T Z 5 3 V   1 1 Stability criterion: compress cool t  t 10   eff 7

  33. Gas through shock: heats to virial temperature compression on a dynamical timescale versus radiative cooling timescale Shock-stability analysis (Birnboim & Dekel 03): post-shock pressure vs. gravitational collapse  1 1 21 4 R compress cool t  t s t   compress  5 3 V 

  34. Compression  3 u   . u const        r

  35. Spherical Simulation vs Model γcrit=1.42  eff time

  36. A virial shock in a 3D cosmological simulation: at Mcrit – rapid expansion from the inner halo to Rvir d(Entropy)/dt Libeskind, Birnboim, Dekel 08

  37. Critical mass for shock heating: Apply tcool ~tcompress with ρ, V, R at the virial radius for ΛCDM halos Approximate cooling: 7 . 0 1  Z T   T ~ 1.6x106 K [ (Z/0.1)0.7 (fb/0.05) (ρr/v)0.1Rv (1+z)3/2]1/2 Vvir~140 km/s [ (Z/0.1)0.7(fb/0.05) (ρr/v)0.1Rv (1+z)3/2]1/4 Mhalo~7x1011 M⊙[ (Z/0.1)0.7(fb/0.05) (ρr/v)0.1Rv (1+z)-1/2]3/4 ~coincides with the bi-modality scale

  38. Shock-Heating Scale . 0  13 1 18 1 ( )  Cvir M z   11 ) 0 log ( / 7 . 1   Z Z z 6x1011Mʘ Mvir [Mʘ] 300 Vvir [km/s] 250 100 120

  39. Shock-Heating Scale Dekel & Birnboim 06 stable shock Mvir [Mʘ] 6x1011 Mʘ typical halos unstable shock

  40. Fraction of Cold Gas in Halos: Cosmological simulations (Kravtsov) cold hot Birnboim, Dekel, Neistein 2007 Zinger, Birnboim, Dekel, Kravtsov

  41. Hot Gas in Elliptical Galaxies Mathews & Brighenti 04; O’Sullivan et al. 01

  42. Cold Flows in Typical Halos 1013 shock heating 1012 Mvir [Mʘ] 2σ (4.7%) M* of Press Schechter 1011 at z>1 most halos are M<Mshock 1σ (22%) 0 1 2 3 4 5 redshift z

  43. Shock-heating Scale Birnboim & Dekel 03 T 104 105 106 107 +3 M~6x1011Mʘ cold infall into discs +1 Brems. log gas density -1 shock heating H2 CDM -3 tcool<tff -5 He H 10 30 100 300 1000 virial velocity

  44. 3. Filaments in Hot Medium At high redshift, in relatively isolated galaxies Relation to the universal clustering scale 16

  45. At High z, in Massive Halos: Cold Streams in a Hot Medium in M>Mshock Totally hot at z<1 Cold streams at z>2 shock cooling no shock

  46. Cold, dense filaments and clumps (50%) riding on dark-matter filaments and sub-halos Birnboim, Zinger, Dekel, Kravtsov

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