Metal abundancesin star-forming regions

The puzzle

V. Lebouteiller, D. Kunth

V. Lebouteiller – Moriond 2005

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

The Blue Compact Dwarf Galaxy IZw 18

Mixing in the ISMMixing in the ISM

1/18

V. Lebouteiller – Moriond 2005

From the IR...From the IR...

Optical, IR :emission line spectrum

Kunth & Sargent (1986) : lack of extremely metal-poor galaxies in surveys

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

2/18

V. Lebouteiller – Moriond 2005

...to the UV...to the UV

Res: ~0.07 Å Resonant lines

of : HI, OI, NI, FeII, SiII, ArI, ...

FUSE (NASA-CNES-ASC)

+ (HST/STIS, HST/GHRS, IUE, Copernicus, HUT)

Absorption line spectrum

900 Å

1200 Å3/18

V. Lebouteiller – Moriond 2005

+ clouds of the Milky Way

4/18

Probing the neutral gasProbing the neutral gas

V. Lebouteiller – Moriond 2005

Absorption Spectra analysisAbsorption Spectra analysis

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)

One single absorption line system

Deriving abundances from the column densities• ionization structure

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

5/18

V. Lebouteiller – Moriond 2005

Blue Compact DwarfsBlue Compact Dwarfs

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)

NGC1705 NGC253 IZw18 IZw36 Markarian59 SBS0335-052

[N/H] [O/H]

[Si/H] [P/H]

[Ar/H] [Fe/H]

HII region (opt. +IR em. lines)HI region (UV abs. lines)

6/18

V. Lebouteiller – Moriond 2005

Avoid possible systematic errors, study the effects of the multiple sightlines, ...

Opportunity to model the ionization stucture, etc...

Individual HII regions in spiral

galaxies

1’1’

Single HII region Stellar population

can be resolved

M33M33

7/18

V. Lebouteiller – Moriond 2005

Far-UV spectraFar-UV spectra

FUSEFUSEMDRSMDRS

FUSEFUSELWRSLWRS

HST/HST/STISSTIS

20 pc

FUSE LWRSFUSE MDRS IUE

HST/STIS

Fig. : HST/STIS image at 2000 Å ofNGC604, in M33

8/18

V. Lebouteiller – Moriond 2005

ISM analysisISM analysis

Pcygni CIII Pcygni OVI

Metals in NGC604 HI in NGC604

Wavelength (Å)

9/18

V. Lebouteiller – Moriond 2005

Radio, 21cm emission log N(HI)=21.1 UV, 10 IUE spectra Ly UV, STIS spectra towards ind. stars Ly UV, STIS global spectrum Ly UV, FUSE spectra Ly

HI in absorption (UVresonance lines)

HI in emission (21cm, radio)

HHII contentcontent

10/18

V. Lebouteiller – Moriond 2005

Radio, 21cm emission log N(HI)=21.1 UV, 10 IUE spectra Ly 21.07±0.20 UV, STIS spectra towards ind. stars Ly UV, STIS global spectrum Ly UV, FUSE spectra Ly

HHI I contentcontent

11/18

V. Lebouteiller – Moriond 2005

HHI I contentcontent

Radio, 21cm emission log N(HI)=21.1 UV, 10 IUE spectra Ly 21.07±0.20 UV, STIS spectra towards ind. stars Ly UV, STIS global spectrum Ly UV, FUSE spectra Ly

12/18

HIHIHHI I withwith STIS STIS

Mean value =20.84±0.23

Flux-weighted mean =20.77±0.27

selection effects no significant

systematic errors

Lyman

V. Lebouteiller – Moriond 2005

HHI I contentcontent

Radio, 21cm emission log N(HI)=21.1 UV, 10 IUE spectra Ly 21.07±0.20 UV, STIS spectra towards ind. stars Ly

20.84±0.23 UV, STIS global spectrum Ly 20.67±0.20 UV, FUSE spectra Ly

14/18

V. Lebouteiller – Moriond 2005

HHI I contentcontent

Radio, 21cm emission log N(HI)=21.1 UV, 10 IUE spectra Ly 21.07±0.20 UV, STIS spectra towards ind. stars Ly

20.84±0.23 UV, STIS global spectrum Ly 20.67±0.20 UV, FUSE spectra Ly 20.75±0.20

15/18

V. Lebouteiller – Moriond 2005

Ionization effectsIonization effects CLOUDY

photoionization code

Estimate column densities in the HII gas

+ dominant ionization state in the neutral gas

16/18

V. Lebouteiller – Moriond 2005

Abundances consistent with O

Global underabundance of N andthe α-elements / solar(X/H neutral < 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

17/18

Comparison with ionized gas resultsComparison with ionized gas results

V. Lebouteiller – Moriond 2005

DiscussionDiscussion

Local enrichment by a previous burst ?(timescale !)

Dilution by lower metallicity gas ?Infalling halo or extragalactic gasPhotodissociation of H2

HI in form of baryionic dark matter (dense cold clumpsof primordial material)

Confirmation on more solid grounds of the BCDs results

18/18

V. Lebouteiller – Moriond 2005