V. Lebouteiller, D. Kunth

1
Metal abundances in star-forming regionsThe
puzzle

• V. Lebouteiller, D. Kunth

2
Mixing in the ISM

• Fate of the metals produced in stars ?
• Dispersion mixing timescales
• Starburst regions context

The Blue Compact Dwarf Galaxy IZw 18
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From the IR...

• Optical, IR
• emission line spectrum
• Kunth Sargent (1986) lack of extremely
  metal-poor galaxies in surveys

• Selfpollution ?
• by fresh released metals in situ by SNe,
  providing rapid (few Myrs) cooling of the hot gas
  during the lifetime of the starburst

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...to the UV
Absorption line spectrum
FUSE (NASA-CNES-ASC) (HST/STIS, HST/GHRS, IUE,
Copernicus, HUT)
900 Å

• Res 0.07 Å
• Resonant lines of HI, OI, NI, FeII, SiII, ArI,
  ...

1200 Å
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Probing the neutral gas
clouds of the Milky Way
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Absorption Spectra analysis

• Profile fitting procedure Owens (M. Lemoine, IAP)
• returns most likely values
• Owens derives an estimation of the errors
• (including uncertainties on the LSF, the
  continuum,...)

N
, b, T

• One single absorption line system
• Deriving abundances from the column densities
• ionization structure

H N O Si P Ar Fe
H I (13.60 eV) N I (14.53 eV) O I
(13.62 eV) SiII (16.34 eV) P II (19.72 eV) Ar
I (15.76 eV) FeII (16.18 eV)
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Blue Compact Dwarfs
HII region (opt. IR em. lines) HI region (UV
abs. lines)
N/H
O/H

• NGC1705
• NGC253
• IZw18
• IZw36
• Markarian59
• SBS0335-052

Si/H
P/H
Ar/H
Fe/H
Refs Lebouteiller et al. (2003), Lecavelier et
al. (2003), Aloisi et al. (2003), Thuan et
al. (2005), Thuan et al. (2002), Lee et al. (2003)
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Individual HII regions in spiral galaxies
M33

• Single HII region
• Stellar population can be resolved

Avoid possible systematic errors, study the
effects of the multiple sightlines,
... Opportunity to model the ionization
stucture, etc...
1
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Far-UV spectra
Fig. HST/STIS image at 2000 Å of NGC604, in M33
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ISM analysis
Pcygni CIII
Pcygni OVI
Wavelength (Å)
Metals in NGC604 HI in NGC604
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HI content

• Radio, 21cm emission ? log N(HI)21.1
• UV, 10 IUE spectra Lya ?
• UV, STIS spectra towards ind. stars Lya ?
• UV, STIS global spectrum Lya ?
• UV, FUSE spectra Lyb ?

HI in absorption (UV resonance lines)
HI in emission (21cm, radio)
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HI content

• Radio, 21cm emission ? log N(HI)21.1
• UV, 10 IUE spectra Lya ? 21.070.20
• UV, STIS spectra towards ind. stars Lya ?
• UV, STIS global spectrum Lya ?
• UV, FUSE spectra Lyb ?

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HI content

• Radio, 21cm emission ? log N(HI)21.1
• UV, 10 IUE spectra Lya ? 21.070.20
• UV, STIS spectra towards ind. stars Lya ?
• UV, STIS global spectrum Lya ?
• UV, FUSE spectra Lyb ?

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HI
HI with STIS

• Mean value
• 20.840.23
• Flux-weighted mean
• 20.770.27
• selection effects
• ? no significant systematic errors

Lyman a
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HI content

• Radio, 21cm emission ? log N(HI)21.1
• UV, 10 IUE spectra Lya ? 21.070.20
• UV, STIS spectra towards ind. stars Lya ?
  20.840.23
• UV, STIS global spectrum Lya ? 20.670.20
• UV, FUSE spectra Lyb ?

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HI content

• Radio, 21cm emission ? log N(HI)21.1
• UV, 10 IUE spectra Lya ? 21.070.20
• UV, STIS spectra towards ind. stars Lya ?
  20.840.23
• UV, STIS global spectrum Lya ? 20.670.20
• UV, FUSE spectra Lyb ? 20.750.20

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Ionization effects

• CLOUDY photoionization code
• Estimate column densities in the HII gas

• dominant ionization state in the neutral gas

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Comparison with ionized gas results
Abundances consistent with O Global
underabundance of N and the a-elements /
solar (X/H neutral lt X/H ionized) except Fe
(depletion HII gas ?)
O, Si, Ar in solar proportions N/O, Ar/O
consistent HII/HI No depletion and ionization
corrections for N, O, Si, and Ar
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Discussion
Confirmation on more solid grounds of the BCDs
results

• Local enrichment by a previous burst ?
• (timescale !)
• Dilution by lower metallicity gas ?
• Infalling halo or extragalactic gas
• Photodissociation of H2
• HI in form of baryionic dark matter (dense cold
  clumps
• of primordial material)

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