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Baryonic Dark Matter and Galaxy Formation

Baryonic Dark Matter and Galaxy Formation. Françoise Combes, Observatoire de Paris 29 Avril 2005. Scenario of structure formation. Primordial Fluctuations Cosmological background Filamentary Structures Cosmological simulations Baryonic Galaxies Seen with HST.

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Baryonic Dark Matter and Galaxy Formation

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  1. Baryonic Dark Matter and Galaxy Formation Françoise Combes, Observatoire de Paris 29 Avril 2005

  2. Scenario of structure formation Primordial Fluctuations Cosmological background Filamentary Structures Cosmological simulations Baryonic Galaxies Seen with HST

  3. Main problems of the L-CDM paradigm • Dark matter cusps in galaxy centers, in particular absent in dwarf Irr, dominated by dark matter  Low angular momentum of baryons, and consequent small radius of disks  High predicted number of small haloes Can the hypothesis that dark baryons are in the form of cold gas help to solve the problems?

  4. Hypothesis for dark baryons Baryons in compact objects (brown dwarfs, white dwarfs, black holes) are either not favored by micro-lensing experiments or suffer major problems (Alcock et al 2001, Lasserre et al 2000, Tisserand et al 2004) Best hypothesis is gas, Either hot gas in the intergalactic and inter-cluster medium (Nicastro et al 2005) Or cold gas in the vicinity of galaxies (Pfenniger & Combes 94)

  5. Dark gas in the solar neighborhood Dust detected in B-V (by extinction) and in emission at 3mm Emission Gamma associated To the dark gas By a factor 2 (or more) Grenier et al (2005)

  6. Hot Gas in filaments Detection of OVI in X-ray? WHIM ICM DM

  7. First gas structures After recombinaison, GMCs of 10 5-6 Mo collapse and fragment down to 10-3 Mo, H2 cooling efficient The bulk of the gas does not form stars but a fractal structure, in statistical equilibrium with TCMB Sporadic star formation  after the first stars, Re-ionisation The cold gas survives and will be assembled in more large scale structures to form galaxies A way to solve the « cooling catastrophy » Regulates the consumption of gas into stars (reservoir)

  8. Cusps in galaxy centers Dwarf Irr galaxies are dominated by dark matter, but also the gas mass is dominating the stellar mass Obey the sDM/sHI = cste relation All rotation curves can be explained, when the observed surface density of gas is multiplied by a constant factor  CDM would not be dominating in the center, as is already the case in more evolved early-type galaxies, dominated by the stars Simulated CCGS (cold collapsed gas and stars) is a function of Wb (Gardner et al 03), and of resolution of simulations (physics below the resolution)

  9. Predictions LCDM: cusp versus core Power law of density profile a ~1-1.5, observations a ~0

  10. Hoekstra et al (2001) sDM/sHI In average ~10 Cf Baryonic TF relation (McGaugh et al 00)

  11. Rotation curves of dwarfs DM radial distribution identical to that in HI gas The DM/HI ratio depends slightly on type (larger for early-types) NGC1560 HI x 6.2

  12. Angular momentum and disk formation Baryons lose their angular momentum on the CDM Usual paradigm: baryons at the start  same specific AM than DM The gas is hot and shock heated to the Virial temperature of the halo But another way to accrete mass is cold gas mass accretion Gas is channeled through filaments, moderately heated by weak shocks, and radiating quickly Accretion is not spherical, gas keeps angular momentum Rotation near the Galaxies, more easy to form disks

  13. External gas accretion Katz et al 2002: shock heating to the dark halo virial temperature, before cooling to the neutral ISM temperature? Spherical Cold mode accretion is the most efficient: weak shocks, weak heating and efficient radiation gas channeled along filaments strongly dominates at z>1

  14. Influence of Feedback 5 1015erg/g adiabatic during 30 Myr Preventing star formation Gas above the curve cannot cool Thacker & Couchman (2001) Conclusion: does not solve the problem not enough resolution?

  15. Too many small structures Today, CDM simulations predict 100 times too many small haloes around galaxies like the Milky Way

  16. Cold Gas Accretion:Bars and secular evolution Dynamical instabilities are responsible for evolution With self-regulation Bars form in a cold unstable disk Bars produce gas inflow, and Gas inflow destroys the bar +gas accretion Recent debate about this cycle -- is bar destruction efficient? -- can bars reform? Central Mass Concentration (CMC)

  17. Statistics on bar strength (OSU) Quantification of the accretion rateBlock, Bournaud, Combes, Puerari, Buta 2002 Observed Doubles the mass in 10 Gyr No accretion

  18. Merging of companion and gas accretion To have bars, cold gas is required to increase self-gravity of the disk Dwarf companions: not more than 10% of accretion (interaction between galaxies heat the disk, Toth & Ostriker 92) Massive interactions: develop the spheroids Required: a source of continuous cold gas accretion from the filaments in the near environment of galaxies  Cosmological accretion can explain bar reformation

  19. History of star formation Isolated galaxy Galaxy with accretion and mergers Accretion is compatible with doubling the mass in 10 Gyr

  20. Cold Gas Accretion:Lopsided Galaxies Peculiar galaxies without any companion Richter & Sancisi (1994) 1700 galaxies, 50% asymmetric Late-types 77% Matthews et al 98 Stellar disk also Zaritsky & Rix 97 About 20% of galaxies have A1 > 0.2 In NIR distribution (OSUB sample) 2/3 have A1 required by an external mechanism <A1> 1.5rd < r <2.5rd

  21. Frequency of m=1 perturbation Baldwin et al 80: kinematic waves have long life-time, but not sufficient to explain the A1 frequency Mergers Gas accretion Bournaud, Combes, Jog, Puerari, 2005 The parameter A1 (density) does not correlate with the tidal index Tp ~ M/m r3/D3 Most galaxies are isolated (Wilcots & Prescott 04) A1 and A2 are correlated, for each type Interactions and mergers cannot explain The m=1 of isolated galaxies, the correlation with type and with m=2 a large number of m=1 by accretion

  22. Simulations m=1 : accretion Only gas accretion (here with 4 Mo/yr) can explain the observed frequency of m=1 and the long life-time of the perturbation NGC 1637: simulation observations NIR

  23. CDM Avoidance of dynamical friction GAS If the gas flows slowly in a cold phase on galaxies, the hierarchical merging will lose less angular momentum through dynamical friction Late (instead of early) accretion Same process as feedback, but can be more efficient (Gnedin & Zhao 02) The gas, stripped, does not experience friction

  24. Disruption of small structures More cold gas in dwarf haloes Much less concentration Baryonic clumps heat DM through dynamical friction and smooth any cusp in dwarf galaxies The material is more dissipative, more resonant, and more prone to disruption and merging May change the mass function for low-mass galaxies LSB (Mayer et al 01) HSB

  25. Dark Matter in Galaxy Clusters In clusters, the hot gas dominates the visible mass Most baryons have become visible fb = Wb / Wm ~ 0.15 The radial distribution dark/visible is reversed The mass becomes more and more visible with radius (David et al 95, Ettori & Fabian 99, Sadat & Blanchard 01) The gas mass fraction varies from 10 to 25% according to clusters

  26. Radial distribution of the hot gas fraction fg in clusters The abscissa is the mean density in radius r, normalised to the critical density (Sadat & Blanchard 2001)

  27. Metallicity in clusters and galaxies MFeICM = 2.2 MFegal Metals are ejected via winds, not ram pressure, since no dependance on richness, or S, but s (Renzini 03) Same MFe/LB in clusters and galaxies Clusters have not lost iron, nor accreted pristine material a/Fe ~cste Same processing in the field (Renzini 1997, 2003)

  28. Baryonic dark matter? Cold H2 Clouds Mass ~ 10-3 Mo density ~1010 cm-3 size ~ 20 AU N(H2) ~ 1025 cm-2 tff ~ 1000 yr Adiabatic regime: much longer life-time Fractal: collisions lead to coalescence, heating, and to a statistical equilibrium (Pfenniger & Combes 94) 90% of baryons are not visible (primordial nucleosynthesis) Around galaxies, the baryonic matter dominates The stability of cold H2 gas is due to its fractal structure

  29. D=1.8 Formation by Jeans recursive fragmentation ? a hierarchical fractal ML = N ML-1 rLD = NrL-1D α = rL-1/rL= N-1/D cf Pfenniger & Combes 1994 D=2.2

  30. Projected mass log scale (15 mag) N=10, L=9 The surface filling factor depends strongly on D < 1% for D=1.7 Pfenniger & Combes 1994

  31. Turbulence? Simulation of 2D turbulence 800x800, with star formation 70 Myr Ratio 1000 between densities max and min (Vazquez-Semadeni et al 97)

  32. Simulations of self-gravitating gas Klessen et al (98) Gas clouds (____) Proto-stellar cores (------) vertical: limit with N=5105 dN/ dm ~ mγ, with γ ~ -1.5 At the end, 60% of the mass is in the cores

  33. Stabilisation by galactic shear Semelin & Combes 2000 The only way to maintain the fractal is to re-inject energy at large scale The natural process is galactic rotation The structures at small and large scales then subsist statistically The shear continuously breaks the condensations, which reform Filaments form in permanence at large scale

  34. Simulations of the galactic plane Huber & Pfenniger (01) D smaller with more dissipation Middle Dissipation

  35. Cooling flows in galaxy clusters Cooling time < Hubble time at the center of clusters  Gas Flow, 100 to 1000 Mo/yr Mystery:cold gas or stars formed are not detected? Today, the ampkitude of the flow has been reduced by 10 And the cold gas is detected Edge (2001) Salomé & Combes (2003) 23 detected galaxies in CO Results from Chandra & XMM: cooling flow self-regulated Re-heating process, feedback due to the active nucleus or black Hole: schocks, jets, acoustic waves, bubles...

  36. Perseus Ha (WIYN) and optical (HST) Ha, Conselice 01

  37. Acoustic waves in Perseus with Chandra Fabian et al 2003

  38. Abell 1795: cooling wake T(cool) 300 Myr (Fabian et al 01) 200 Mo/yr for R < 200kpc (Ettori et al 02) = oscillation dynamical time 60kpc filament Ha (Cowie et al 85) at V(amas) Cooling wake The cD galaxy at V=374km/s w/o cluster

  39. A1795: CO(2-1) integrated map Tight correspondance between CO(2-1) emission and the lines Ha +[NII] (grey scale) Radio Jets: contours 6cm van Breugel et al 1984 The AGN creates cavités in the hot gaz  cooling on the boader of cavités, where CO and Ha are observed (Salomé & Combes 2004)

  40. Polar Ring Galaxies (PRG) PRG are composed of an early-type host surrounded by a gas+stars perpendicular ring The polar ring is akin to late-type galaxies large amount of HI, young stars, blue colors Unique opportunity to check the shape of dark matter halo But how to relate DM of PRG to DM of spiral progenitors? Formation scenarios

  41. Formation of Polar Rings By accretion? Schweizer et al 83 Reshetnikov et al 97 By collision? Bekki 97, 98

  42. UGC4261 Tully-Fisher for PRGs AM2020-504 Iodice et al 2002 TF in I band

  43. TF in K band for PRGs with simulations 15%peak Ex Simulations Circles: massless triangles: massive

  44. Non-circular polar rings Both components are seen nearly edge-on (selection effect) Observed V for PR is the smallest, when DM is flattened in the host the more DM, the more PR are excentric

  45. Model of E3 halo flattened in the equatorial plane xy Massless ring Massive ring (as massive as the host)

  46. TF of the host vs Polar Ring Spiral galaxies hosts PRs

  47. Implications of TF of PRGs Most of PRGs require dark matter, aligned along the polar disk Only 2 cases, where the ring is light, can be explained with only the visible baryonic mass flattened along the host With collisionless DM, both merging and accretion scenarios produce either spherical haloes, or flattened along the host If a large fraction of the DM around galaxies is dissipative it is possible to account for the flattening along the polar disk  A large fraction must be gas

  48. H2 pure rotational lines

  49. ISO -Signal of dark matter N(H2) = 1023 cm-2 T = 80 – 90 K 5-15 X HI NGC 891 Grey matter Valentijn & Van der Werf 99

  50. H2EXplorer • 4 lines • 1000 x more sensitive ISO-SWS • L2 • Soyuz • 99 Meuro Survey integration 5s limit total area [sec] [erg s-1 cm-2 sr-1] [degrees] Milky Way 100 10-6 110 ISM SF 100 10-6 55 Nearby Galaxies 200 7 10-7 55 Deep Extra-Galactic 1000 3 10-7 5  CNES  Spitzer  Milky Way, NGC 1560

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