The chemical inventory of HH1 Teresa Giannini, Brunella Nisini, Simone Antoniucci, Dario Lorenzetti,...
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Transcript of The chemical inventory of HH1 Teresa Giannini, Brunella Nisini, Simone Antoniucci, Dario Lorenzetti,...
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The chemical inventory of HH1
Teresa Giannini, Brunella Nisini, Simone Antoniucci, Dario Lorenzetti,
Juan Alcala’, Francesca Bacciotti, Sara Bonito, Linda Podio, Beate Stelzer
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Observations
HST Hα• HH1 is one of the brightest HH-
objects: a well suited laboratory to study chemical composition, abundances and physical conditions
• Deep X-shooter observations from UVB to NIR (~5 h)
• 11’ arcsec slit
• R ~10000 (UVB), 19000 (VIS), 8000 (NIR)
Analysis• AV determination• Derivation of the physical conditions• Derivation of the chemical abundances• Ratios of Iron Einstein coefficients
RA (J2000.0)
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The spectrum : UVB and VIS
• More than 500 detections of atomic fine structure lines (more than 100 [FeII] lines) of atoms with Z up to 28, HI and HeI,II recombination lines, and H2 ro-vibrational lines with vup 9. Likely the deepest spectrum of an HH object sofar observed.
• Solf+ (1988) detected less than 100 lines.
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The spectrum : NIR
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Accurate AV determination • Top: Balmer and Paschen
decrements fitted with case B recombination models
• Bottom: ratios of Balmer and Paschen lines coming from the same upper level, whose theoretical ratios depend only from the local value of AV.
obs Av
Black: observations, red: theory, green: extinction corrected values.
• AV also determined from H2 and atomic lines with the same method.
AV between 0.0 mag and 0.8 mag
Giannini et al. 2014
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Physical conditions
• NLTE code to solve the statistical equilibrium equations for the fine structure levels of atoms (collisional excitation and de-excitation, spontaneous radiative decay)
Te, ne
• Models for Fe II (159 levels), FeIII (34 levels) , Ni II (17 levels), TiII (30 levels ) , CI , NI, NII, OI, OII, OIII, NeII, PII, SII, SIII, ArIII, ArIV, CaII, CrII (5 levels)
• Ionization equilibrium solved for species observed in different ionization stages (e.g. O, S, N). Considered processes: collisional ionization, radiative and dielectronic recombination, charge exchange
xe = ne/nH
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Diagnostic diagrams: Te, ne Temperature indicators
Density indicators
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Diagnostic diagrams: Te, ne Simultaneous determination of Te,ne
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Diagnostic diagrams : Te, ne
Best fit through the [FeII] lines. In red are data from levels whose atomic parameters (collisional and radiative) are uncertain.
Summarizing : 7 000 K Te 80 000 K, 103 cm-3 ne 5 105 cm-3
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Diagnostic diagrams : xe
0.55 Xe 1
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Physical conditions : Te, xe vs IPave
Good correlation between temperature and degree of ionization up to ~ 80 000 K
( )
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Chemical abundances
Abundances lower than solar
Depletion of refractory species around 50%
Z Solar Orion nebula
HH1 Sun-HH1
Orion-HH1
C 8.39 (0.05) 8.40-8.44 7.40-7.87 +0.76 +0.78
N 7.78 (0.06) 7.65-7.73 7.41-7.70 +0.23 +0.13
0 8.66 (0.05) 8.51-8.65 8.60-8.71 +0.00 -0.075
P 5.36 (0.04) - 5.04-5.37 +0.15 -
S 7.14 (0.05) 7.06-7.22 6.8-7.1 +0.19 +0.19
Cl 5.50 (0.30) 5.33-5.46 4.7-5.4 +0.45 +0.34
Ar 6.18 (0.08) 6.50-6.62 6.06-6.10 +0.10 +0.48
Ca 6.31 (0.04) - 5.6-6.2 +0.41 -
Ti 4.90 (0.06) - 4.56-5.07 +0.09 -
Fe 7.45 (0.05) 5.99-6.23 6.91-7.24 +0.38 -0.45
Ni 6.23 (0.04) - 6.04-6.30 +0.06 - Solar : Asplund+ 2005Orion: Esteban+ 2004
• Abundances computed taking into account the derived physical conditions, fractional ionization (xe) and ionization equilibrium of species.
• Abundances computed with respect to H if T < 30000 K and to HeII4-3 if T > 30000 K.
[𝐹𝑒𝐼𝐼 ]1.25𝐻 𝛽
𝑜𝑏𝑠∝𝜀1.25 (𝑇 ,𝑛)𝜀𝐻 𝛽 (𝑇 ,𝑛)
[𝐹𝑒𝐼𝐼 ][𝐹𝑒 ]
𝐻
𝐻+¿𝑋 (𝐹𝑒)𝑋 (𝐻 )
¿
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Iron Einstein coefficients
Giannini+ 2014 (GAN)
• Fe+ Einstein coefficients very difficult tobe theoretically evaluated because of the complexity of the Iron level system.• In HH1 some lines are detected with an exceptionally high SNR (>> 100) that allows to empirically derive the A-values
Ratio NS Q-SST Q-HFR DB SH GAN
1.25m/1.64m
1.04 0.79 0.90 1.04 1.13 0.88(0.04)
1.32m/1.64m
0.29 0.22 0.24 0.29 0.32 0.26(0.01)
NS:Nussbaumer & Storey 1988, Q-SST, Q-HFR: Quinet+1996, DB: Debb & Hibbert 2011, SH: Smith & Hartigan 2006
Our determinations betteragree with a large set of observations
F 1.32/ F 1.64
F 1.
25/
F 1.
64
obs Av
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The H2 emission• H2 ro-vibrational lines with vup 9 (more than 200 lines in the VIS and NIR arm)
• Rotational diagrams of lines with SNR > 5
• Lines fitted with 2 temperature components at T ~ 3000 K and T ~ 6000 K (although with deviations from LTE)
• Fluorescence is not the main excitation mechanism (model from Stenberg & Dalgarno 1989)
• C-ontinous type shocks do not predict bright high vup lines
Most probable exciting mechanism is a J-ump shock (with or without a magnetic precursor)
Log
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Conclusions• X-shooter observations have provided the deepest UVB – NIR spectrum of an HH object with the detection of hundreds of linesfrom several atomic species.
• We are able to determine very precisely the conditions of theemitting gas, which reveal a stratification in temperature, density, and fractional ionization.
• Temperatures as high as 80 000 K are revealed.
• Chemical abundances are estimated for a number of speciesderiving values lower than the solar ones and a level of depletion of the refractory species around 50 %.
• Empirical determinations of the Einstein A-ratios for important[FeII] lines are derived.