The chemical inventory of HH1

Teresa Giannini, Brunella Nisini, Simone Antoniucci, Dario Lorenzetti,

Juan Alcala’, Francesca Bacciotti, Sara Bonito, Linda Podio, Beate Stelzer

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)

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.

The spectrum : NIR

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

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

Diagnostic diagrams: Te, ne Temperature indicators

Density indicators

Diagnostic diagrams: Te, ne Simultaneous determination of Te,ne

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

Diagnostic diagrams : xe

0.55 Xe 1

Physical conditions : Te, xe vs IPave

Good correlation between temperature and degree of ionization up to ~ 80 000 K

( )

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 )

¿

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

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

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.