when ? meets IR the clouds hiding behind the dust

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when ? meets IRthe clouds hiding behind the dust
cosmic rays

• Isabelle Grenier
• Jean-Marc Casandjian
• Régis Terrier
• AIM, Service dAstrophysique, CEA Saclay

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atomic molecular gas

• Leiden-Dwingeloo 21 cm line survey at ?
  gt -30
• Dickey-Lockman 21 cm at ? lt -30

• CO survey from
• Dame et al. 01

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100 µm dust emission

• IRAS 100 µm calibrated using DIRBE Schlegel 98

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dust reddening 94 GHz emission

• IRAS 100µm DIRBE 240µ/100µ gt Ndust for uniform
  ?² B?(18.2K)
• Ndust scaled to E(B-V) from external
  galaxies Schlegel 98

• IRAS 100µm DIRBE
• DMR FIRAS
• gt Idust at 94GHz for
• ?2.70 B?(16.2K)
• ?1.67 B?(9.2K)
• Finkbeiner 99

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? rays above 100 MeV

• Compton-EGRET interstellar radiation

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the local interstellar model

• b gt 5 or 10 cosmic-ray density uniform at
  D lt 0.5-1 kpc

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interstellar fit

• warm dust ?
• cold dust ???

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fit improvements

• IC emission from the coldest dust ltlt

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fit improvement
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H2 / dark / dense HI matriochkas
movies at http//dphs10.saclay.cea.fr/Sap/Actualit
es/Breves/grenier050217/images/
l0 70
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local gas reserves

• opt. thin HI
• qHI qdark

• X gt 100 MeV 1.74 0.04
• X gt 300 MeV 1.61 0.03
• 1020 H2 cm-2 K-1 km-1 s
• line-of-sight
• average densities

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dark clouds

• low, but enough shielding
• using AV /E(B-V) 3.1
• normal metallicity

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anomalous dust

• anomalous dust emission Bennett 03, Lagache
  04
• from spinning dust?
• not local synchrotron variations

94 GHz
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cold HI or cold H2 ?

• maybe HI
• ndark nCNM
• Rdark RdenseHI
• but

• maybe H2
• enough Av
• NH/E(B-V) close to the CO one
• enough grains to form H2
• cold environment (Tdust 10 K)
• H2 absorption lines without CO
• around Cham (Gry 02)
• gt nHI2nH2 50 H cm-3
• gt 2N(H2)/NHtot 50-70
• H2 absorption lines without CO
• in cirrus clouds (Reach 94)

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any CO detection?

• beam diluted tiny clumps for WCO lt 2 K km/s

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any CO detection?

• why not? too cold? Tdust 10 K, densities to
  low?
• only tips of icebergs seen

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dark vs. H2 and HI mass

• mass ratios ind. of distance
• Mdark/MCO ? with MCO

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dark vs. H2 and HI mass

• locally
• Mdark/MCO ? with MCO

Mdark 2 105 M? MH2-CO 6 105 M? MdenseHI 7
105 M? Mdark/MCO 30-35 Mdark/MdesnHI 26-30
local ISM biased to large H2 clouds
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CO mass spectrum in the Milky Way
dN/dM ? M-1.8 0.03 Heyer 01

• in the outer galaxy
• complete down to 500 M?
• and up to D lt 10 kpc
• in the inner Galaxy center
• higher masses sampled
• Williams McKee 97 Miyasaki 00

• for 103 MCO 106M?
• more if 500 M? or flatter Mdk(McO)

? -1.6 -1.8 -1.9 -2.0
Mdk/MCO 0.6 0.9 1.1 1.4
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X ratio

• X N(H2) / W(CO) qCO/2qHI if nCR(HI)nCR(H2)
• no virial equilibrium or gas/dust assumption,
• but small bias from structured IC emission ? e-
  far-IR field

Cloud RGal (kpc) X in 1020 mol. cm-2 K-1 km-1 s
Ophiuchus 8.4 1.1 0.2 Local average at b gt 5 1.61 0.04 (gt100 MeV) 1.73 0.03 (gt300 MeV) 1.8 0.3 (I100µ Dame 01)
Taurus 8.6 1.08 0.10
Cepheus 8.7 0.92 0.14 Galactic average 1.9 0.2 (Strong 96) 1.56 0.05 (Hunter 97)
Orion 8.9 1.35 0.15
Monoceros 9.2 1.64 0.31 larger X in the outer Galaxy
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