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H 2 in external galaxies and baryonic dark matter

H 2 in external galaxies and baryonic dark matter. London March 2007 Françoise COMBES. Hypothesis for dark baryons. W b ~ 5%  90% of baryons are dark Baryons in compact objects (brown dwarfs, white dwarfs, black holes) are either not favored by micro-lensing experiments

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H 2 in external galaxies and baryonic dark matter

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  1. H2 in external galaxies and baryonic dark matter London March 2007 Françoise COMBES

  2. Hypothesis for dark baryons Wb ~ 5%  90% of baryons are dark 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 gasin the vicinity of galaxies and cosmic filaments (Pfenniger & Combes 94)

  3. 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)

  4. CO as a tracer of H2 Arnault et al 1988 N6946 Dwarfs and low metallicity environments LCO/M(HI) α (O/H)2.2 Confirmed by Taylor & Kobulnicky (98) But see Walter et al (2003) Leroy et al (2005)

  5. HI as a tracer of DM HI gas is the interface with the extragalactic radiation field Beyond the HI disk, truncature due to ionisation the interface is ionized Explains the correlation sDM/sHI (Bosma 1981, Freeman 1994, Carignan 1997) The observed ratio sDM/sHI ~10 for spiral galaxies, varies slightly with morphological type, decreases for dwarfs and LSB Mass profiles for dwarf Irr galaxies dominated by DM stringent test that constrain CDM (Burkert & Silk 1997) even collisional (Spergel & Steinhardt 99)

  6. Extension in UV (GALEX) XUV disks, M83 and others M83, Galex, +HI contours (red) Thilker et al 2005 Yellow line RHII, 10Mo/pc2 in HI Bluer regions outside Younger SF + scattered light

  7. M83: optical Extension of galaxies in HI Dark halo exploration HI NGC 5055 Sbc Milky Way-like spiral (109 M of HI): M83

  8. Hoekstra et al (2001) sDM/sHI In average ~10

  9. Rotation Curves of dwarfs DM has a radial distribution identical to that of HI gas The ratio DM/HI depends slightly on type (larger for early-types) NGC1560 HI x 6.2 From Combes 2000

  10. Combination with MOND NGC 1560 Tiret & Combes 2007, variation of a0 ~ 1/(gas/HI) V4 = a0 GM

  11. Baryonic dark matter in 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) Around galaxies, the baryonic matter may dominate The stability of cold H2 gas is due to its fractal structure

  12. First structures After recombinaison, GMCs of 105-6 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)

  13. WHIM Where are the baryons? • 6% in galaxies ; 3% in galaxy clusters (X-ray gas) • <18% in Lyman-alpha forest of cosmic filaments • 5-10% in the Warm-Hot WHIM 105-106K • 65% are not yet identified! The majority of baryons are not in galaxies ICM DM

  14. Ly-alpha forest W(Lya) = 0.008[N14J-23 R100 4.8/(a+3)]1/2 h70 = 18% of baryons N14 = typical Lya column density J = J-23n-a Extragalactic background radiation field R100 = assumed radius of absorber Could be lower by a factor 3, if R100 = 0.1 Broad to narrow Lya ratio is 3 times larger at low redshift Lehner et al (2006)

  15. WHIM from OVI absorptions Stocke et al (2006) FUSE The WHIM is observed at 350kpc from large galaxies At 100 kpc from dwarf galaxies Certainly due to SN and superbubbles outflow AGN feedback, or Intergalactic accretion schocks (Shull 2006) Multiphase gas HI and OVI not correlated

  16. WHIM 105-6K (OVI) 5-10% Danforth & Shull 2005 Wb(OVI) = 0.002-0.004 (0.2/f)(0.1/Z) = 5-10% f(OVI) assumed ionisation fraction 20% Z metallicity, assumed 0.1 solar Ionisation (photo) and metallicity quite uncertain NeVIII more difficult to find, but photoionisation less uncertain F(NeVIII) < 15% Wb(NeVIII) < Wb(OVI) Assuming IGM, but if only around galaxies?

  17. >106K WHIM observations?OVII, OVIII Detection of 2 filaments at z=0.011 and z=0.027 with Chandra In front of the los of Mk421 blazar, during an outburst (ToO) n = 10-6 cm-3, N ~10 15cm-2 (d ~5-100) X-ray absorption lines OVII, NVII +FUSE OVI OVII, and individual lines at 2-4 s (Nicastro et al 2005) Not confirmed by XMM summary of observations of Mk421 Williams et al (2006) May be 40% of the missing baryons, as predicted by CDM simulations (Cen et al 1999)

  18. Nicastro et al 2005 3 lines fitted at the same time z=0 z=0.011 z=0.027 v=3300km/s v=8090km/s

  19. UV Lines of H2 • Absorption lines with FUSE (Av < 1.5) • Ubiquitous H2 in our Galaxy (Shull et al 2000, Rachford et al 2001) translucent or diffuse clouds, from 1014cm-2 • Absorption in LMC/SMC reduced H2 abundances, high UV field (Tumlinson et al 2002) • High Velocity Clouds detected (Richter et al 2001) in H2 (not in CO) • 16/35 IVCs detected, while 1/19 HVC detected in H2 Wakker et al 2006

  20. Ly 4-0 FUSE Spectrum of the LMC star Sk-67-166 (Tumlinson et al 2002) NH2 = 5.5 1015cm-2

  21. Infrared Lines of H2 • Ground state, with ISO & Spitzer (28, 17, 12, 9μ) • From the ground, 2.2 μ, v=1-0 S(1) • excitation by shocks, SN, outflows, UV pumping, X • require T > 2000K, nH2 > 104cm-3 • exceptional merger N6240: 0.01% of L in the 2.2 μ line (all vib lines 0.1%?)

  22. H2 distribution in NGC891 (Valentijn, van der Werf 1999) S(0) filled; S(1) open – CO profile (full line)

  23. Large quantities of H2 revealed by ISO N(H2) = 1023 cm-2 T = 80 – 90 K 5-15 X HI NGC 891, Pure rotational H2 lines S(0) & S(1) S(0) wider: more extended Derived N(H2)/N(HI) = 20 ; Dark Matter?

  24. Spitzer H2 results • H2 line survey for 77 ULIRGs z=0.02-0.93 (Higdon S. et al 2006) • H2 mass (warm)= 107 to 109 Mo • Warm H2 is 1% of all H2 (CO) • H2 in Tidal Dwarf Galaxies :NGC5291 N/S: 460, 400 K • MH2 (warm) =1-1.5105 Mo; if colder (150 K): 106 Mo • H2 in Stephan’s quintet: large-scale shock (Appleton et al 06) • H2 in the nascent starburst N1377 (Roussel et al 2006) • H2 in Cooling flows filaments (Egami et al 2006)

  25. High Velocity Clouds (HVC) infalling onto the Galaxy Spitzer and IRAS Images +HI spectra (GBT)

  26. Infrared-HI correlation In (x,y) = Si ani NHIi (x,y) + Cn (x,y) • First detection of dust emission in the HVC • HVC Emissivity at 100 mm ~ 10 times smaller than local gas, but only a factor 2 smaller at 160mm • Colder dust Miville-Deschênes et al 2005

  27. H2 in Stephan’s quintet Appleton et al 2006 broad (870 km/s) bright H2 group-wide shock wave typical H2 excitation diagram: T01=185K at 51018T35=675K No PAH features, very low excitation ionized gas Shocks when the high-V intruder collides with gas filaments in the group

  28. Perseus Cluster Fabian et al 2003 Salome, Combes, Edge et al 06

  29. H2 in cooling flow clusters Egami et al 2006

  30. Conclusions • Dark baryons should in the form of gas • A significant part could be cold molecular gas • The best tracer: pure rotational lines: • Observations of excited warm H2 as a tracer • H2 in the outer parts of galaxies: H2* is a tracer of the bulk of • molecular gas, which is invisible; In the main disk CO is a tracer, • but it fails in the outer parts • Goals of the H2EX mission: • Distribution of the warm H2 with respect to the underlying SF • Relation between the HI and H2 in galaxies; the detailed kinematics will help to associate the various gas phases

  31. H2EXplorer • 4 lines • 1000 x more sensitive ISO-SWS • L2 • Soyuz • 100-200 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  Cosmic Vision ESA

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