Presentation is loading. Please wait.

Presentation is loading. Please wait.

M. Benedettini, A. Lorenzani, B. Nisini, M. Vasta (Italy) S. Cabrit, E. Caux, C. Ceccarelli, P. Hily-Blant, B. Lefloch, L. Pagani, S. Pacheco, M. Salez.

Similar presentations


Presentation on theme: "M. Benedettini, A. Lorenzani, B. Nisini, M. Vasta (Italy) S. Cabrit, E. Caux, C. Ceccarelli, P. Hily-Blant, B. Lefloch, L. Pagani, S. Pacheco, M. Salez."— Presentation transcript:

1 M. Benedettini, A. Lorenzani, B. Nisini, M. Vasta (Italy) S. Cabrit, E. Caux, C. Ceccarelli, P. Hily-Blant, B. Lefloch, L. Pagani, S. Pacheco, M. Salez (France) F. Gueth, K. Schuster (IRAM), J. Cernicharo (Spain) A. Boogert, G. Melnick, D. Neufeld (USA) P. Caselli, S. Viti (UK), B. Parise (Germany) C. Codella (OAA, Firenze, Italy) on behalf of the CHESS team

2 Outline 1.The CHESS Herschel KP 2.The L1157-B1 outflow shock region 3.L1157-B1: what we learned from ground 4.L1157-B1: the Herschel lesson

3 ULTIMATE GOAL: chemical surveys during the early phases of low-, intermediate-, and high-mass star formation; IMMEDIATE GOAL: to guide successive Herschel observations and provide a legacy database for the general community; METHOD: HIFI (and PACS) spectral surveys in representative SFRs; TARGETS: from low- to high-mass protostars, from pre- to post-collapse, from the source to the surroundings; OUTFLOWS: to study the effects of shocks on the cloud hosting the protostar. Shocks trigger endothermic chemical reactions, ice grain mantle sublimation or sputtering. The CHESS KP in a nutshell (PI: C. Ceccarelli, LAOG, France)

4 The L1157-mm chemical active outflow Spitzer 8 μm: grey CO: contours Bachiller et al. (2001), Looney et al. (2007), Neufeld et al. (2009) Distance: 250 pc (440 pc); Driven source: Class 0 protostar (IRAS20386+6751), L= 4-11 L  ; Most chemically rich outflow known so far; Ideal laboratory to observe the effects of shocks on the gas chemistry; Precessing molecular outflow associated with several bow shocks seen in CO and in H 2.

5 The L1157-mm chemical active outflow H 2 : grey CO: blue and red Several red- and blue-bow shocks seen in CO and in H2; The brightest blue-shifted bow-shock has been mapped with the PdB and VLA arrays revealing a rich and clumpy structure, the clumps being located at the wall of the cavity with an arch-shape (Tafalla & Bachiller 1995, Gueth et al. 1996, 1998, Benedettini et al. 2007, Codella et al. 2009); Well traced by molecules released by dust mantles such as H 2 CO, CH 3 OH, and NH 3 as well as typical tracers of high-speed shocks such as SiO. B1 B2 B0 R R0 R2

6 Several red- and blue-bow shocks seen in CO and in H2; The brightest blue-shifted bow-shock has been mapped with the PdB and VLA arrays revealing a rich and clumpy structure, the clumps being located at the wall of the cavity with an arch-shape (Tafalla & Bachiller 1995, Gueth et al. 1996, 1998, Benedettini et al. 2007, Codella et al. 2009); Well traced by molecules released by dust mantles such as H 2 CO, CH 3 OH, and NH 3 as well as typical tracers of high-speed shocks such as SiO. The L1157-mm chemical active outflow B1 B2 B0 R R0 R2 STAR B1 SiO(3-2) CH 3 OH(3k-2k)

7 The L1157-mm chemical active outflow Different gas components: Slow and cold (10-20 K) swept-up material (low-J CO lines); Hot gas (2000 K) usually traced by H 2. The link between cold and hot components (i.e. the warm component) is crucial to understand how the protostellar wind transfers energy back to the ambient medium. So far, temperatures between 60-200 K has been measured using NH 3, CH 3 CN, and SiO (Tafalla & Bachiller 1995, Nisini et al. 2007, Codella et al. 2009). However, a detailed study of the excitation conditions of the B1 structure is still missing due to the limited range of excitation covered by the cm- and mm-observations performed so far. Observations of lines with high excitation (Eu > 50-100 K) are required.

8 First results: the unbiased spectral survey of HIFI-Band 1b (555-636 GHz)

9 First results: the unbiased spectral survey of HIFI-Band 1b (555-636 GHz) A total of 27 lines are identified in Band 1b, down to an average 3-sigma level of 30 mK (Ta scale). Besides CO and H 2 O (Lefloch et al. 2010) we identify lines from NH 3, H 2 CO, CH 3 OH, CS, HCN, and HCO + (Codella et al. 2010)

10 Origin of the Molecular Emission Bright broad emission in CO and H 2 O up to v ≈ - 30 km/s (Vsys = +2.6 km/s) Two Velocity Components in CO : HVC : v < -7 km/s LVC : v > -7 km/s HVC ! LVC CO(6-5) @ CSO (12”) CO(6-5) averaged over 40” Lefloch et al. (2010)

11 The Low- and High-Velocity Components: filling factors LVC: Extended: From CO(6-5)@CSO and, SiO(2-1)@PdBI we infer ff  1/3 Gueth et al. (1998), Lefloch et al. (2010), Nisini et al. (2010) SiO HVC SiO LVC HVC: Compact: SiO(2-1)/H 2 O intensity ratio is constant for v < -7 km/s; both emissions arise from the same region : ff ≈ 0.03

12 Physical Conditions in the CO Gas Derived from LVG analysis of CO 5-4 using complementary CO 3-2, 6-5 line (CSO observations), and assuming ff= 0.03 (HVC) and 0.3 (LVC). LVC T < 100 K n(H 2 )= (1-3)x10 5 cm -3 N(CO)= 8x10 16 cm -2 Consistent with: LVC: warm, dense gas; HVC: warmer, less dense gas HVC T= > 300 K n(H 2 )= (1-3) x 10 4 cm -3 N(CO)= 5x10 16 cm -2 Lefloch et al. (2010)

13 Water Emission in L1157-B1 LVG analysis (slab geometry) of each component assuming the same physical conditions (T, n, ff) as for CO. If we assume OPR=3, T(LVC)=100 K, and T(HVC)=400 K (from CO): LVC: X(H 2 O) < 10 -6 HVC: X(H 2 O) < 10 -4 Higher H 2 O abundance in the HVC: high-T reactions favored and more efficient removal from grain mantles. In this model, the bulk of the PACS-WISH 179 µm line arises from the (unresolved) HVC Lefloch et al. (2010) Preliminary analysis in agreement with steady- state C-shock models for HVC: Vshock  15-20 km/s in pre-shock gas n(H 2 )= 5 x 10 4 cm -3 (Gusdorf et al. 2008)

14 Different tracers at different velocities Codella et al. (2010) All the spectra (but CO and H 2 O) show blue-shifted wings peaking near 0 km/s, and with a terminal velocity equal to -8,-6 km/s. Lack of HV possibly due to S/N (PdBI spectra: HV emission weaker than the peak emission by a factor 5-10). HV emission is more diluted: HIFI data at higher frequencies will be instructive.

15 A secondary peak occurs between -3.0 and -4.0 km/s (here defined medium velocity, MV) and well outlined by e.g. HCN(7-6). The MV peak is visible also in NH 3 and in some lines of CH 3 OH and H 2 CO. PdBI spectra show that the MV secondary peak is observed in a couple of lines of CH 3 OH at 3mm and only towards the western B1b clump. This finding suggests the existence of a velocity component mainly coming from the western side of B1, while the HV gas is emitted from the eastern one. Different tracers at different velocities

16 NH 3 /H 2 O vs. Velocity: It could reflect different pre-shock ice compositions in the MV gas. Alternatively, this behavior is consistent with the SPECULATION that NH 3 is released by grain mantles, whereas water is released by grain mantles and, in addition, copiously formed in the warm shocked gas by endothermic reactions, which convert all gaseous atomic oxygen into water. Codella et al. (2010)

17 Gas-grain shock model (Viti et al. 2004; Jiménez-Serra et al. 2008) - Gas grain chemical model + C-shock model + pre-existing clump at 10 5 cm -3 ; - Clear difference in the trend of the water abundance w.r.t to other species; - All species are enhanced by mantle sputtering; - During the shock period water and, to a lesser extent, ammonia are also enhanced but water is the only species that is maintained high even after the shock has passed. Viti et al. (2010) Log(age/yr) H2OH2O H 2 CO NH 3 CH 3 OH

18 Different gas components…. In agreement with the old 30-m results Two components at different temperatures or non-LTE effects and line opacity? The present observations provide a link between the gas at Tkin 60--200 K (NH 3, CH 3 CN, SiO) previously observed from ground and the warmer gas probed by the H 2 lines. Codella et al. (2010)

19 Different gas components…. In agreement with the old 30-m results Two components at different temperatures or non-LTE effects and line opacity? The present observations provide a link between the gas at Tkin 60--200 K (NH 3, CH 3 CN, SiO) previously observed from ground and the warmer gas probed by the H 2 lines. Codella et al. (2010) Flower et al. (2010)

20 Fit of H 2 mid- and NIR-data using a temperature stratification model (from 300 to 4000 K) H 2 S(1) 17  m L1157-mm dN  T -  B1 position Nisini et al. (2010) Different gas components….

21 What about other outflows? In agreement with the old 30-m results RED Trot = 14 K BLUE Trot = 13 K NGC1333-IRAS 2 (Bachiller et al. (1998)

22 Physical properties along the B1 bow shock LVG: CS(12-11), HIFI, and CS(2-1), (3--2), PdBI: we derive a kinetic temperature definitely above 300 K. Caution: we could trace different gas components, as suggested by methanol, the gas at higher excitation being traced by CS(12-11). Densities around 10 4 cm -3. LV gas denser than the MV one? Codella et al. (2010)

23 PACS-CHESS spectral survey (55-210  m) of L1157-B1 Preliminary PACS results: AT LEAST: CO lines: from J = 14-13 to 22-21 7 H 2 O lines, OI @ 63  m, OH @ 119  m  Excitation vs. position & Filling Factor OI 63  m o-H 2 O o-H 2 18 O p-H 2 O CO(14-13) o-H 2 O CO(15-14) PACS In addition: other HIFI-CHESS spectra so far observed: CO: from 6-5 to 10-9, 14-13, 16-15 + 13 CO: 8-7 H 2 O: 1 11 -0 00, 3 12 -3 03, 3 12 -2 21, 2 12 -1 01, 2 21 -2 12 HCl: 1-0 + C + @ 157 μm

24 PEERING INTO A PROTOSTELLAR SHOCK: CONCLUSIONS The molecular emission arises from 2 physically distinct regions: LVC : warm, extended, chemically rich dense gas, with internal structure revealed from specific tracers : high-velocities from the eastern side, high-densities on the western side. HVC : hot, compact, lower density gas. Less dense medium towards B1b (MV peak)? H 2 O abundance increases by 2 orders of magnitude between LVC and HVC. SiO HVC SiO LVC Codella et al. (2009, 2010) 132 K 55 K 92 K 67 K 73 K

25

26 Origin of the Molecular Emission Lefloch et al. (2010)

27 The L1157-mm chemical active outflow Bachiller et al. (2001)

28 H 2 O localized on the CO peaks of the precessing jet Correlation between H 2 O and H 2 warm gas at T ~ 300 K H 2 O follows SiO --> tracer of high density shocks with V > ~ 20 km/s H 2 17µm Neufeld et al. (2009), H 2 O 179 µm Nisini et al. (2010) CO(2-1), SiO(3-2) Bachiller et al. (2001) PACS-WISH KP map of 179 µm line in L1157 SiO(2-1) @ PdBI Gueth et al. (1998)

29 PACS map of 179 µm line in L1157 L1157 mm Spitzer IRAC Herschel PACS H 2 O 179  m 10 4 AU Strong water emission from the embedded protostar Emission peaks trace the shock interaction regions PACS observations: 9.4”/pixel, 6’x2’ raster map R(179 µm) ~ 1500 H 2 : grey CO: blue and red

30 The Low-Velocity Component Extended: From CO(6-5)@CSO and, SiO(2-1)@PdBI we infer ff  1/3 Gueth et al. (1998), Lefloch et al. (2010) SiO HVC SiO LVC

31 The High-Velocity Component SiO(2-1)/H 2 O intensity ratio is constant for v < -7 km/s  Both emissions arise from the same region : ff ≈ 0.03 (4” x 12”, PdBI)  Emission is optically thick SiO HVC SiO LVC Gueth et al. (1996, 1998), Lefloch et al. (2010)

32 Water Emission in L1157-B1 LVG analysis (slab geometry) of each component assuming the same physical conditions (T, n, ff) as for CO and taking into account the total 179 µm line flux (PACS-WISH, Nisini et al. 2010). If we assume OPR=3, T(LVC)=100 K, and T(HVC)=400 K (from CO): LVC: N(H 2 O)= (4.0-5.0) x 10 14 cm -2 X= (0.7-0.8) x 10 -6 HVC: N(H 2 O)= (2.5-3.0) x 10 16 cm -2 X= (0.6-0.8) x 10 -4  Higher H 2 O abundance in the HVC: high-T reactions favored and more efficient removal from grain mantles. In this model, the bulk of the 179 µm line arises from the (unresolved) HVC Lefloch et al. (2010)

33 Water Emission in L1157-B1 LVG analysis (slab geometry) of each component assuming the same physical conditions (T, n, ff) as for CO and taking into account the total 179 µm line flux (PACS-WISH, Nisini et al. 2010). If we assume OPR=3, T(LVC)=100 K, and T(HVC)=400 K (from CO): LVC: N(H 2 O)= (4.0-5.0) x 10 14 cm -2 X= (0.7-0.8) x 10 -6 HVC: N(H 2 O)= (2.5-3.0) x 10 16 cm -2 X= (0.6-0.8) x 10 -4  Higher H 2 O abundance in the HVC: high-T reactions favored and more efficient removal from grain mantles. In this model, the bulk of the 179 µm line arises from the (unresolved) HVC Lefloch et al. (2010) Preliminary analysis in agreement with steady-state C-shock models for HVC: Vshock  15-20 km/s in pre- shock gas n(H 2 )= 5 x 10 4 cm -3 (Gusdorf et al. 2008)

34 Gas-grain shock model (Viti et al. 2004; Jiménez-Serra et al. 2008) - Gas grain chemical model + C-shock model + pre-existing clump at 10 5 cm -3 ; - Clear difference in the trend of the water abundance w.r.t to other species; - All species are enhanced by mantle sputtering; - During the shock period water and, to a lesser extent, ammonia are also enhanced but water is the only species that is maintained high even after the shock has passed. Viti et al. (2010) N(H2) Tkin Log(age/yr) H2OH2O H 2 CO NH 3 CH 3 OH

35 Forthcoming analysis: PACS-CHESS spectral survey (55-210  m) of L1157-B1 Preliminary results: AT LEAST: CO lines: from J = 14-13 to 22- 21 7 H 2 O lines, OI @ 63  m, OH @ 119  m  Excitation vs. position  Filling factors OI 63  m o-H 2 O o-H 2 18 O p-H 2 O CO(14-13) o-H 2 O CO(15-14) PACS

36 PACS-CHESS spectral survey (55-210  m) of L1157-B1 Preliminary results: AT LEAST: CO lines: from J = 14-13 to 22- 21 7 H 2 O lines, OI @ 63  m, OH @ 119  m  Excitation vs. position  Filling factor OI 63  m o-H 2 O o-H 2 18 O p-H 2 O CO(14-13) o-H 2 O CO(15-14) PACS Other HIFI-CHESS spectra so far observed: CO: from 6-5 to 10-9, 14-13, 16-15 13 CO: 8-7 H 2 O: 1 11 -0 00, 3 12 -3 03, 3 12 -2 21, 2 12 -1 01, 2 21 -2 12 HCl: 1-0 C + @ 157 μm


Download ppt "M. Benedettini, A. Lorenzani, B. Nisini, M. Vasta (Italy) S. Cabrit, E. Caux, C. Ceccarelli, P. Hily-Blant, B. Lefloch, L. Pagani, S. Pacheco, M. Salez."

Similar presentations


Ads by Google