Upload
hien
View
39
Download
0
Embed Size (px)
DESCRIPTION
Is the ISM in Starburst galaxies well mixed?. presented by Vianney Lebouteiller (IAP) coll. with Daniel Kunth. Team / Collaborators. Thesis of Vianney Lebouteiller Team of the Institut d’Astrophysique de Paris (IAP) - PowerPoint PPT Presentation
Citation preview
presented by Vianney Lebouteiller (IAP)
coll. with Daniel Kunth
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Team / Team / CollaboratorsCollaborators
Thesis of Vianney Lebouteiller
Team of the Institut d’Astrophysique de Paris (IAP) french team (A. Lecavelier des Etangs, J.-
M. Désert, G. Hébrard, R. Ferlet, A. Vidal-Madjar)
& LERMA - Obs. de Paris : J. Lequeux & JHU Baltimore : A. Aloisi
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
OutlinOutlinee
Problematic : self-enrichment of the HProblematic : self-enrichment of the HIIII regions ? regions ?
A new approach: study of the neutral gasA new approach: study of the neutral gas• FUSEFUSE• method and analysismethod and analysis
Results on Blue Compact DwarfsResults on Blue Compact Dwarfs
The next step: Giant HThe next step: Giant HIIII regions regions• the example of NGC 604the example of NGC 604
Results on NGC 604Results on NGC 604• neutral gas homogeneityneutral gas homogeneity• abundances ratioabundances ratio• modellingmodelling
Conclusions & PerspectivesConclusions & Perspectives
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Origin of the Origin of the problemproblem
The problem of mixing in the ISM is a genenal one
Moreover, Kunth & Sargent (1986) pointed outthe lack of extremely metal-poor galaxies inemission-line surveys hence proposed :
Self-enrichment hypothesis :Self–pollution by fresh released metals in situ
by SNe,
providing rapid cooling of the hot gas during the lifetime of the starburst.
Pristine gas in the outer regions ?
IZw18
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Small scale abundances inhomogenities suspected in a few objects:
NGC5253 (Walsh & Roy, 1989; Kobulnicky et al. 1997)
local pollution in IIZw40 (Walsh & Roy, 1993)
and Mkn 996 (Thuan et al. 1996) : N/H overabundances
attributed to WR winds. But not true in all young starburts (Kobulnicky, 1999; Oey & Schield, 2000)
Abundances are similar to those of young stars
Evidences Evidences against/foragainst/for abundances abundances discontinuitiesdiscontinuities
IZw18, SBS0035-052, SMC: 6 regions: log O/H=8.13 ±0.08 LMC: 4 regions: log O/H=8.37 ±0.25 (Russel & Dopita 1990)
α-elements in hot gas is often over solar e.g. in the LMC (Dennerl et al. 2001) Delayed mixing ?
IZw18
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Two models Two models ……
Tenorio-Tagle 1996 Recchi et al. 2002
SNe expell the gas, creating a superbubble evolving in a low density spherical halo: disperse and mix
ejecta and winds carry out metals but gas immediately cools down and enrich the ISM
no discontinuitiesno discontinuities discontinuitiesdiscontinuities
few few 101099 yrs yrs few few 101066 yrs yrsMixing timescaleMixing timescale
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
FUSFUSEE
900-1200 Å HI, OI, NI,
FeII, SiII, ArI, ...
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Studying the HStudying the HII metal metal compositioncomposition
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Abundances Abundances determinationdetermination
Profile fitting procedure Owens (M. Lemoine) returns most likely values (N, b, T, ...)
Owens derives an estimation of the errors(including uncertainties on the LSF, the continuum,...)
One homogeneous cloud
Deriving abundances from the column densities ionization structure assumed a priori
Fig: Example of fitted lines
HH
NN
OO
SiSi
P P
ArAr
FeFe
H H I I (13.60 eV)(13.60 eV)
N N I I (14.53 eV)(14.53 eV)
O O I I (13.62 eV)(13.62 eV)
SiSiII II (16.34 eV)(16.34 eV)
P P II II (19.72 eV)(19.72 eV)
Ar Ar I I (15.76 eV)(15.76 eV)
FeFeII II (16.18 eV)(16.18 eV)
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Results : Blue Compact Results : Blue Compact DwarfsDwarfs
Refs : Lebouteiller et al. (2003) for IZw36, Lecavelier et al. (2003) and Aloisi et al. ( 2003) for IZw18 Thuan et al. (in preparation) for SBS 0335-052, Thuan et al. (2002) for Markarian 59
HI region(UV abs. lines)
HII region(opt. em. lines)
log
(X/H
)lo
g (X
/H)
log
(X/H
)lo
g (X
/H)
(+NGC1705 poster n°3 A. Aloisi and NGC253 poster n°14 J. Cannon)(+NGC1705 poster n°3 A. Aloisi and NGC253 poster n°14 J. Cannon)
? ? ?? ? ?
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Observations of Observations of individual Hindividual HIIII regions in spiral regions in spiral galaxiesgalaxies
1’1’
Relatively high S/N, sightlines less complex
Avoid possible systematic errors, study the effects of the multiple sightlines, ...
Unique possibility to model, to know the ionization stucture, etc...
M33M33
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
The case of The case of NGC604NGC604
FUSEFUSEMDRSMDRS
FUSEFUSELWRSLWRS
HST/HST/STISSTIS
20 pc
3-5 Myrs (Hunter et al. 1996),4-5 (Wilson & Matthews 1995)
~200 pc HII region size
~2 ksec~7 ksec~13 ksec Exp. time
~2 Å~0.07 Å~0.07 Å Resolution
G140L
52’’x2’’4’’x20’’30’’x30’’ Mode
HST/STISHST/STIS
(H(HI, I, 2D))
FUSEFUSE
(metals)(metals)
FUSEFUSE
(metals)(metals)
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
CIII Pcygni feature
NGC 604 NGC 604 spectrumspectrum
OVI Pcygni feature
Metals from M33Metals from M33 HHII from M33from M33
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
HI column density HI column density determinationdetermination
log log NN(H(HI)I) = 21.01 = 21.01±0.05±0.05
Profiles Profiles before before convolutionconvolutionProfilesProfiles after after convolution convolutionRed: total profileRed: total profile
20.52 20.52 ±±0.190.19star O4, V=19.2
20.86 20.86 ±±0.180.18star O4 Iab, V=18.2
20.73 20.73 ±±0.150.15star O4 Ia, V=17.0
23/18
HHII withwithSTISSTIS
(fig. of Bruhweiler at al. 2001)
Lyman Lyman αα
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Mimic FUSE Mimic FUSE datadata
Do we overestimate HI column density ?
N(HN(HII)=20.96)=20.96
Construction of the global spectrum ≡ mean, weighted by the stars magnitudes
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Consistent determinations
Global underabundance in the neutral gas, even for Fe
Less enriched gas in the sightlines vs. enrichment of the HII gasX/HX/H
Results: Results: abundances X/Habundances X/H
Diffuse neutral gas(FUSE LWRS & MDRS)
Ionized gas(optical emission-lines)
log
(X
/H)
log
(X
/H)
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Results: Results: abundances X/Yabundances X/Y
N/O same as HII region N primary, no ionization correction
Ar/O little ionization correction may be needed
log
(X/Y
)lo
g (X
/Y)
X/YX/Y
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
PDRPDRHHIIII region region HHII region => region =>
Modelling of Modelling of NGC604NGC604
Coupling with HICoupling with HI
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Conclusions & Conclusions & perspectivesperspectives
Difficult interpretation for BCDs needs to be validated
Giant HII Regions
Evidence for pockets of metal deficient neutral gas in NGC604 less chemically evolved gas in the sight lines ? are dustier regions invisible in far-UV more metallic ?
Is the neutral gas associated to the HII region ? v(HI) always v(HII)
Future work on other giant HII regions in M33
Investigate hidden saturated lines (...resolution effects) See poster n°41 for more details
end of the presentationend of the presentation
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Column densitiesColumn densities
LWRS MDRS
HHII 21.00±0.03 ?
NNII 15.21±0.05 15.35±0.05
OOII 16.47±0.08 18.28±0.80
SiSiIIII 15.52±0.05 15.69±0.12
PPIIII 13.83±0.15 13.70±0.10
ArArII 13.86±0.07 14.05±0.10
FeFeIIII 14.94±0.02 14.94±0.04
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
HST/HST/STISSTIS
LWRSLWRSMDRSMDRS
NGC 604NGC 604 : MDRS and LWRS observations
test
λ (Å)
Tota
l b
road
en
ing
/3 (
px)
The derived broadenings are consistentThe derived broadenings are consistent with the size of the clusterwith the size of the cluster15’’15’’
4’’4’’
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
HI stellar contamination ?HI stellar contamination ?
Stellar vs. interstellar HI ?Stellar vs. interstellar HI ?
O stars dominate O stars dominate No significant stellar No significant stellar contamination is expected for Lycontamination is expected for Lyββ in hot in hotstars stellar population stars stellar population (Robert et al. 2003)(Robert et al. 2003)
ObservationsObservationsSynth Mod SpecSynth Mod SpecTheo modelTheo model
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
V -246 km s-1 (Melnick)
D 840 kpc (Freedman, Wilson & Madore 1991
Size~10 comp. of ~10 pc in the halo
190 pc core (Viallefond & Gross 1986)
220 pc core (Israel et al. 1981)
450 pc halo (Aller 1984)
dcenter3 kpc (Wilson &
Scoville 1992)
M(HI) 1.6 106 M (Wilson & Scoville 1992)
1.1 106 (Viallefond & Gross 1986)
1.0 106 (Deul & Van der Hulst 1986)
M(HII) 9.0 105 (Viallefond & Gross 1986)
3.3 106 (Churchwell & Goss 1999)
9.2 105 (Israel et al. 1981)
M(H2) 3.5 106 (Wilson & Scoville 1992)
NGC 604, some factsNGC 604, some facts
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Stellar contamination evidencesStellar contamination evidences
C IIIC III
N VN V Si IVSi IV C IVC IV
Synthetic model spectra (Starburst 99)Synthetic model spectra (Starburst 99)0.5 Z0.5 Z
IMF=-2.35IMF=-2.35Instantaneous burstInstantaneous burstUses a stellar library from observationsUses a stellar library from observations
Synthetic model spectra (Synthetic model spectra (Robert et al.Robert et al. 20032003))0.5 Z0.5 Z
IMF=-2.35IMF=-2.35Instantaneous burstInstantaneous burstUses a stellar library from observationsUses a stellar library from observations
Kunth/Lebouteiller - The Neutral Gas Cambridge 04
Modelling of NGC604Modelling of NGC604
Cd fit LWRS independent compare with HIIR cd:
To come : PDR modelling
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
HI NI OI SiII PII ArI FeII
HI region
HII region + PDR
NE
UT
RA
L
R
EG
ION
NE
UT
RA
L
R
EG
ION
PDRPDRHHIIII region region