H2 in external galaxies and baryonic dark matter

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H2 in external galaxies and baryonic dark matter

• London March 2007
• Françoise COMBES

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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 gas in the vicinity of galaxies and
cosmic filaments (Pfenniger Combes 94)
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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)
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CO as a tracer of H2
Arnault et al 1988
N6946
Dwarfs and low metallicity environments
LCO/M(HI) a (O/H)2.2 Confirmed
by Taylor Kobulnicky (98) But see Walter et al
(2003) Leroy et al (2005)
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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)
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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
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Extension of galaxies in HI
M83 optical
Dark halo exploration
HI
NGC 5055 Sbc
Milky Way-like spiral (109 M? of HI) M83
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Hoekstra et al (2001)
sDM/sHI
In average 10
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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
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Combination with MOND
NGC 1560 Tiret Combes 2007, variation of a0
1/(gas/HI)
V4 a0 GM
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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
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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)
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Where are the baryons?
WHIM

• ?6 in galaxies 3 in galaxy clusters (X-ray
  gas)
• ?lt18 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
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Ly-alpha forest
W(Lya) 0.008N14J-23 R100 4.8/(a3)1/2 h70
18 of baryons N14 typical Lya column
density J J-23 n-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)
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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
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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) lt
15 Wb(NeVIII) lt Wb(OVI) Assuming IGM, but if
only around galaxies?
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gt106K WHIM observations?OVII, OVIII
Detection of 2 filaments at z0.011 and z0.027
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)
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Nicastro et al 2005
3 lines fitted at the same time z0 z0.011 z0.02
7 v3300km/s v8090km/s
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UV Lines of H2

• Absorption lines with FUSE (Av lt 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

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Ly 4-0
FUSE Spectrum of the LMC star Sk-67-166
(Tumlinson et al 2002) NH2
5.5 1015cm-2
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Infrared Lines of H2

• Ground state, with ISO Spitzer (28, 17, 12, 9µ)
  
• From the ground, 2.2 µ, v1-0 S(1)
• excitation by shocks, SN, outflows, UV pumping, X
• require T gt 2000K, nH2 gt 104cm-3
• exceptional merger N6240 0.01 of L in the 2.2 µ
  line (all vib lines 0.1?)

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H2 distribution in NGC891 (Valentijn, van der
Werf 1999) S(0) filled S(1) open CO profile
(full line)
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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?
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Spitzer H2 results

• ?H2 line survey for 77 ULIRGs z0.02-0.93 (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 Stephans 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)

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High Velocity Clouds (HVC) infalling onto the
Galaxy
Spitzer and IRAS Images HI spectra (GBT)
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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 160 mm
• Colder dust

Miville-Deschênes et al 2005
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H2 in Stephans quintet
Appleton et al 2006 broad (870 km/s) bright
H2 group-wide shock wave typical H2 excitation
diagram T01185K at 51018T35675K
No PAH features, very low excitation ionized
gas Shocks when the high-V intruder collides
with gas filaments in the group
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Perseus Cluster
Fabian et al 2003
Salome, Combes, Edge et al 06
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H2 in cooling flow clusters
Egami et al 2006
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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

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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
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? CNES ? Cosmic Vision ESA