The O budget in lowmass protostars:

Transcription

1 The O budget in lowmass protostars: The NGC1333-IRAS4A R1 shock observed in [O I] 63 μm with SOFIA-GREAT Lars E. Kristensen Center for Star & Planet Formation, Niels Bohr Institute, University of Copenhagen A. Gusdorf, A. Karska, J.C. Mottram, R. Visser, H. Wiesemeyer, R. Güsten, R. Simon and special thanks to G. Sandell 1

2 Low-mass YSO evolution Class 0 Class I Class II Arce & Sargent (2006) Jet / wind present at all evolutionary stages 2

3 OH + H3 + O H2 OH Low T High T H2 H2O + H2O chemistry: H2 O:gr three routes H2 H Ice H3O + e H2O E H2O:gr 3

4 Shock chemistry T (K) vshock ~ few km/s Volatile Oxygen budget H2Oice H2Ogas CO O 4

5 Shock chemistry T (K) vshock ~ few km/s Volatile Oxygen budget H2Oice H2Ogas CO O km/s 4

6 Shock chemistry T (K) vshock ~ few km/s Volatile Oxygen budget H2Oice H2Ogas CO O km/s 4

7 Shock chemistry T (K) vshock ~ few km/s Volatile Oxygen budget H2Oice H2Ogas CO O km/s 4

8 Shock chemistry T (K) vshock ~ few km/s Volatile Oxygen budget H2Oice H2Ogas CO O

9 Kristensen et al. (2010, 2012), Mottram et al. (2014) 5

10 Dissecting a profile One profile: lots of H2O moving! Bulk of emission in three components Velocity resolution allows for decomposition BHR71 15 L 2.7 M Medium offset comp. Bullet Envelope emission + absorption = inverse P-Cygni Broad outflow Bullet Kristensen et al. (2012), Mottram et al. (2014) 6

11 Physical components Cavity shocks Protostellar wind A&A 538, A2 (2012) Given the high densities and low in the wind (see Sect. 3) the same tem adopted here for all particles. The la underlying single-fluid MHD wind so numerically the following differential sity ρ, species number density n(a), and streamline, as a function of altitude z a S f ρf u dρ f =, dz vz dn(a) Ra n(a) u =, dz vz Γ Λ ntot kb T u 32 kb T R dt = 3 dz 2 kb ntot vz Panoglou et al. (2012), Yvart et al. (2016) 150 Class 0 height z (AU) 100 Absorbing envelope Spot shocks Yvart et a Cavity shocks (broad) Class 0 : Ser SMM Lo 230pc 0 cylindrical radius r0 (AU) Fig. 1. Overall geometry of the slow MHD disk wind solution of (Casse & Ferreira 2000) used in this article. Solid white curves show various magnetic flow surfaces, with that anchored at 1 AU shown in dashed. The density for M acc = 10 6 M /yr and M = 0.5 M, is coded in the contour plot starting at cm 3 and increasing by factors of 2. The bottom dotted line traces the slow magnetosonic surface (at 1.7 disk scale heights) where our chemical integration starts. Kristensen et al. (2010, 2012, 2013), Mottram et al. (2014, 2017), Visser et al. (2012) 0.4 T (K) Here, vz and ( u) are the bulk ver (3D) flow divergence interpolated fro tion, ntot is the total number density o perature, kb is the Boltzmann constant change in mass and number of particl volume, and Γ and Λ are the heating a volume. The equations on n(a) apply as to the individual populations of the fi an energy of K) which are integ other variables. The equations on ρ f app tral, positive, negative) and are used m ing purposes, as the total mass density MHD solution. Cooling and heating mechanisms in Eq. (9) of Garcia et al. (2001a). In particular, the midplane field X AU radiative cooling by H2 lines exci H2, He, and electrons (Le Bourlot e radiative cooling by CO, H2 O, Velocity Gradient approximation 1993), and by OH and NH3 in the l et al. 1985); atomic cooling by fine-structure an N, O, S, Si, C+, N+, O+, S+, Si+ (Fl (Giannini et al. 2004); inelastic scattering of electrons on H 1991; Hummer 1963; Rapp & Eng energy released by collisional ion and exo/endo-thermicity of chemic

12 Evolutionary scheme Class 0 Class 0: H 2O tightly linked to outflow, infall, molecular jet, profiles are the broadest + brightest Class I: envelope opens, outflow force decreases, expansion, profiles decrease in width + intensity (Visser et al. 2012, Kristensen et al. 2012, Mottram et al. 2014) 8 Class I Spot shocks Cavity shocks (broad) Expanding envelope (regular P-Cygni) Absorbing envelope Cavity shocks (broad)

13 Quest for H2O abundance Step I: determine excitation conditions, particularly N(H2O) Step II: Choose appropriate reference frame to get N(H2) Step III: Calculate x(h 2O) = N(H2O) / N(H2) 9

14 Profile shape vs. excitation Similarity in profile shapes independent of excitation (different at outflow positions) Excitation conditions constant with v in each component N1333-I4B 4.4 L 3.0 M Eup ~ 250 K x K 50 K Observations in same beam Kristensen et al. (2010) Mottram et al. (2014) 10

15 H 2 O: subthermally excited RADEX excitation analysis Conclusion: small emitting area (10 2 AU), high temperature (~ 300 K), high column density (~10 18 cm -2 ), high density ( cm -3 ) Mottram et al. (2014) 11 n[h 2 ](cm 3 ) log(n[h 2 ]) (cm 3 ) log(n[h 2 O]) (cm 2 ) Cavity shock Spot shock Table 7 Tafalla 250 AU 1000 AU 500 AU 50 AU 100 AU I/I988 GHz Beam averaged N[H 2 O] (cm 2 )

16 Surprisingly low X(H 2 O): ~ times too little? N1333-I4A L ~ 10 L D ~ 230 pc log(h2o / CO 16-15) Mean Class 0 Class I u - u LSR (km s 1 ) Where is the oxygen? 12 I(H2O) / I(CO), t(co) N(H 2 O)=4x10 16 cm 2 n(h 2 )=10 6 cm GHz 1670 GHz N(H 2 O) / N(CO) Kristensen et al. 2012, 2017b, Santangelo et al. 2013, 2014, Tafalla et al. 2013, Neufeld et al. 2014

17 HH46 HH46 L ~ 12 L D ~ 450 pc H2O 557 GHz Δv ~ 35 km/s HIFI Flux density [Jy] [O I] x10 x10 x10 CO CO H O OH 2 x10 x3 x40 x10 x5 x Velocity [km s 1 ] λ [µm] Kristensen et al. 2012; van Kempen, Kristensen et al. (2010) 13

18 Herschel-PACS: FIR inventory Herczeg et al. (2012) 14

19 FIR line cooling budget Class 0 Class I Class II CO H 2O OI OH LX (L ) FIR cooling dominated by O-species Cooling not chemistry! Karska et al. 2013, in prep., Podio et al

20 Complex water line profiles BHR71 15 L 2.7 M Envelope emission + absorption = inverse P-Cygni Herschel-HIFI Medium offset comp. Bullet Broad outflow Bullet Kristensen et al. (2012), Mottram et al. (2014) Velocity resolution: identifying physical components 16

21 30.0 NGC1333 IRAS4 15:00.0 R :14: : :00.0 IRAS 4B IRAS 4A B2 [O I] emission lights up at shock spots - but where does [O I] emission come from? 11: :29: Nisini et al. 2015

22 Enter SOFIA- 1.0 H 2 O x GREAT! 0.8 [O I] 63 μm detected H 2 O x at R1 position 0.6 Only seen in highvelocity component! TMB (K) 0.4 H 2 O x0.4 CO x HV component also seen in CO (GREAT) and H2O (HIFI) Kristensen et al. 2017a [O I] 63 µm u (km s 1 ) 6 00

23 Excitation -> Oxygen budget I(CO) / I(H2O) S14 M14 Recipe: Assume excitation from H 2 O Apply to CO, < OH, and O Get N(CO), N(OH), N(O) Assume X(O) volatile = Calculate X(M) X(H 2 O) ~ X(CO) ~ X(OH) < X(O) ~ Kristensen et al. 2017a 19 I(O) / I(H2O) I(OH) / I(H2O) N(CO) / N(H 2 O) S14 M N(O) / N(H 2 O) 10 0 S14 M N(OH) / N(H 2 O)

24 Low X(O) at high v: what does it mean? Atomic O is ~15% of total O budget at high v, ~85% molecular and primarily CO Volatile C/O ratio ~0.7 Do the youngest sources host atomic/ionic jets? Why so much molecular material? Reformation, or molecular from the start? Implications for outflow energetics? mass loss rates and infall rates? One spectrum, one paper, many new questions! 20

25 What have we learnt? Lesson I: SOFIA-GREAT is delivering beautiful [O I] 63 μm spectra! Lesson II: Toward one shock position, [O I] traces only the high-velocity component and the bulk of O is in molecular form Lesson III: Systematic surveys are needed: do lessons from one source apply elsewhere? (Accepted C5 proposal: two new spectra not yet delivered, two more papers?) 21