Presented by Vianney Lebouteiller (IAP) coll. with Daniel Kunth

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


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


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


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


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


FUSFUSEE

900-1200 Å HI, OI, NI,

FeII, SiII, ArI, ...


Studying the HStudying the HII metal metal compositioncomposition


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)


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)

? ? ?? ? ?


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


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)


CIII Pcygni feature

NGC 604 NGC 604 spectrumspectrum

OVI Pcygni feature

Metals from M33Metals from M33 HHII from M33from M33


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


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


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)


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


PDRPDRHHIIII region region HHII region => region =>

Modelling of Modelling of NGC604NGC604

Coupling with HICoupling with HI


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


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


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’’


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


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



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


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

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Presented by Vianney Lebouteiller (IAP) coll. with Daniel Kunth