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INFALL AND OUTFLOW IN HIGH-MASS STAR FORMING REGIONS

INFALL AND OUTFLOW IN HIGH-MASS STAR FORMING REGIONS. Ana L ópez Sepulcre Ciclo XXIII Supervisors: Malcolm Walmsley, Riccardo Cesaroni, Claudio Codella. OUTLINE. The European MC Network CONSTELLATION Introduction: High-mass star formation This thesis:

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INFALL AND OUTFLOW IN HIGH-MASS STAR FORMING REGIONS

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  1. INFALL AND OUTFLOW IN HIGH-MASS STAR FORMING REGIONS Ana López Sepulcre Ciclo XXIII Supervisors: Malcolm Walmsley, Riccardo Cesaroni, Claudio Codella

  2. OUTLINE The European MC Network CONSTELLATION Introduction: High-mass star formation This thesis: • Searching for molecular outflows in selected high-mass star forming regions (SFRs) • Infall (and outflow) in a sample of high-mass molecular clumps in different evolutionary stages • Infall at different spatial scales in particular massive star forming regions: determining the velocity field of infalling massive clumps Summary Future work

  3. CONSTELLATION: The origin of stellar masses European Commission FP6 Marie Curie Research Training Network involving a large number of European astronomy institutions who will be training young scientists through research into the origin of stellar masses WP1: From clouds to cores to protostars WP2: The birth and influence of massive stars WP3: The physics of the low-mass end of the IMF www.constellation-rtn.eu

  4. INTRODUCTION: HIGH-MASS STAR FORMATION

  5. High-mass Star Formation: Problems Observational problems Rare; located at high distances (~ 5 kpc) Fast evolution towards ZAMS Formation in clustered mode: confusion Theoretical problem Stars with M ≥ 8Msun reach the ZAMS while still accreting  radiation pressure should halt the accretion process Stars with M > 8Msun cannot form (?!)

  6. High-mass Star Formation: Solutions 1. Accretion through disks and/or with larger accretion rates than those for low-mass stars Well-defined disk/outflow system 2. Merging of low-mass stars Disks/outflows associated with the low-mass stars should be destroyed during merging So far, evidence seems to support accretion (e.g. G24.78+0.08, see Cesaroni et al 2007, PPV 5, p.197) But… Is this the general case???

  7. Properties of clumps Infrared Dark Clouds Size: 1-3 pc Density: 103 -104 cm-3 Temperature: 10 - 20 K Mass: 103 -104 Msun Non-Infrared Dark Clouds Size: 0.5-1 pc Density: 105 -106 cm-3 Temperature: 30 - 50 K Mass: 103 -104 Msun time Molecular clumps are the sites of star formation and may contain: - Hot Molecular Cores: smaller, hotter and denser cores with embedded very young (proto)stars - Stars already in the Main Sequence - (Compact) HII regions ionised by high-mass stars (OB) High-mass molecular clumps

  8. Study of clumps Requires multi-line observations at different angular resolutions Molecular tracers (mm-cm wavelengths): 12CO, 13CO: bipolar outflows  location and luminosity of embedded stars C18O, C17O: ambient gas  velocity field and column density distribution HCO+: outflowing and infalling motions CN: column density (hyperfine structure) SiO: molecular jets NH3 in absorption (towards Hypercompact HII regions): velocity field; radiative transfer models needed to interpretline profile

  9. THIS THESIS FIRST YEAR: STRUCTURE OF PARSEC-SCALE MASSIVE MOLECULAR CLUMPS

  10. PROJECTS Searching for molecular outflows in selected high-mass star forming regions (SFRs) Infall (and outflow) in a sample of high-mass molecular clumps in different evolutionary stages Infallat different spatial scales in particular massive star forming regions: determining the velocity field of infalling massive clumps

  11. 1. MOLECULAR OUTFLOWS IN SELECTED MASSIVE SFRs A. López-Sepulcre, C. Codella, M. Beltrán, R. Cesaroni, N. Marcelino, L. Moscadelli Aims of the project • -To search for outflows: The presence of an outflow will support the presence of accretion disks. • To determine the outflow physical parameters and characterise the embedded YSOs. • To look for radial velocity gradients suggesting the presence of rotating envelopes • To select good targets for follow-up interferometricobservations

  12. Association with: (i) H2O, OH and CH3OH masers massive + young (ii) High luminosity: Lbol = 104 - 106 Lsun massive stars (iii) compact sub-mm continuum emission embedded stars MOLECULAR OUTFLOWS IN SELECTED MASSIVE SFRs Selection criteria 11 SOURCES d = 2 - 12 kpc

  13. MOLECULAR OUTFLOWS IN SELECTED MASSIVE SFRs IRAM - 30m observations September 2006 On-The-Fly mapping with HERA (9-beam array working at 1.3 mm) 4’ x 4’ maps Pico Veleta radio telescope 13CO(2-1) Outflow tracer @ 220.4 GHz, HPBW = 11” C18O(2-1) Ambient tracer @ 219.6 GHz, HPBW = 11”

  14. BLUE WING RED WING Ambient MOLECULAR OUTFLOWS IN SELECTED MASSIVE SFRs The method Half power contour 0.5 pc C18O(2-1) map: ambient gas 13CO(2-1) and C18O(2-1) spectra

  15. MOLECULAR OUTFLOWS IN SELECTED MASSIVE SFRs Results: Molecular Outflows Outflows detected in 6 out of 11 sources  Outflow detection rate: 55 % The remaining 45% is confused (but display wide 13CO wings Fig. 1, López-Sepulcre et al. (in prep.)

  16. MOLECULAR OUTFLOWS IN SELECTED MASSIVE SFRs Results: C18O velocity maps Fig. 2, López-Sepulcre et al. (in prep.) In some cases, the C18O emission displays velocity gradients Higher angular resolution observations needed to reveal their nature (rotation?)

  17. Grey: C18O(2-1) 0.4 pc MOLECULAR OUTFLOWS IN SELECTED MASSIVE SFRs The method and results for G35.20-0.74 C18O velocity map Velocity gradient perpendicular to outflow axis (rotation?) Bipolar outflow detected

  18. MOLECULAR OUTFLOWS IN SELECTED MASSIVE SFRs Results: Derived parameters • Mclump and Mvir from C18O emission  ~ Equilibrium • Moutflow from 13CO emission (v > vamb)  M, p, E • Kinematic age of the outflow (t = size/vout) dM/dt, dp/dt, Lmec Comparison of our results with those by Beuther et al. (2002) High-mass outflows: massive YSOs (probably in the accretion phase)

  19. 2. INFALL IN A SAMPLE OF MASSIVE MOLECULAR CLUMPS A. López-Sepulcre , R. Cesaroni, M. Walmsley InfraRed Dark Clouds (IRDCs) vs non-IRDCs IRDC: G24.60+0.1 (M1, M2) Non-IRDC: G28.28-0.35 Rathborne et al. (2006): Image: 8 µm MSX Contours: 1.2 mm

  20. INFALL IN A SAMPLE OF MASSIVE MOLECULAR CLUMPS General aims of the project • To compare the star formation activity of IRDCs with that present in known high-mass star forming clumps: evolutionary trends? • To check Krumholtz & McKee’s result: • ∑ ~ 0.7 g cm-2 is the minimum surface density required for high-mass star formation (2008. Nature, 451, 1082)

  21. INFALL IN A SAMPLE OF MASSIVE MOLECULAR CLUMPS The sample Two sub-samples: 1. IRDC sub-clumps, from the 1.2-mm survey by Rathborne et al (2006) 2. Parsec-scale molecular clumps harboring massive hot cores and/or UCHII regions, i.e., known high-mass star forming regions (non-IRDCs), from the surveys by Beuther et al. (2002), Fáundez et al. (2004) and Hill et al. (2005) Selection Criteria  > -10° M > 100 Msun: massive d < 4 kpc: angular diameters in the range 1’-2’

  22. INFALL IN A SAMPLE OF MASSIVE MOLECULAR CLUMPS Sample Selection 19 sources 46 sources 15 above and 31 below the limit ∑ = 0.7 g cm-2 27 sources Possible to check Krumholz & McKee’s result

  23. INFALL IN A SAMPLE OF MASSIVE MOLECULAR CLUMPS Molecular tracers used Optically thick: HCO+(1-0) @ 89.2 GHz HCN(1-0) @ 88.6 GHz Blue asymmetric line profile: infall Broad line wings: outflow Optically thin: C18O(2-1) @ 219.6 GHz To define ambient velocity

  24. INFALL IN A SAMPLE OF MASSIVE MOLECULAR CLUMPS IRAM - 30m observations Proposal submitted in March 2008 Observations: 4-8 August 2008 On-The-Fly mapping 1’ x 1’ maps 18 IRDCs and 31non-IRDCs mapped (sample extended to 49 sources “on the spot”) Pico Veleta radio telescope (8 Aug 08)

  25. INFALL IN A SAMPLE OF MASSIVE MOLECULAR CLUMPS PRELIMINARY results G25.04-0.2M1 HCO+(1-0) and C18O(2-1) spectra towards the peak of the HCO+(1-0) emission of the IRDC G25.04-0.2M1 HCO+(1-0) outflow contour map overlaid on a Spitzer 8m image

  26. INFALL IN A SAMPLE OF MASSIVE MOLECULAR CLUMPS PRELIMINARY results G25.04-0.2M2 HCO+(1-0) and C18O(2-1) spectra towards the peak of the HCO+(1-0) emission of the IRDC G25.04-0.2M1 HCO+(1-0) outflow contour map overlaid on a Spitzer 8m image

  27. INFALL IN A SAMPLE OF MASSIVE MOLECULAR CLUMPS PRELIMINARY results Blue asymmetry (i.e infall) statistics Molecular outflow statistics Molecular outflow statistics from the HCO+(1-0) lines Data need to be analysed in more detail

  28. 3. INFALL IN PARTICULAR MASSIVE STAR FORMING REGIONS A. López-Sepulcre , R. Cesaroni, M. Walmsley A. López-Sepulcre, F. Fontani, J. Brand, R. Cesaroni, M. Walmsley, F. Wyrowski Observing plan: interferometry + single-dish (zero-spacing) Study of infall a different spatial scales Observed data still to be reduced …

  29. SUMMARY Past 1. 13CO(2-1) and C18O(2-1) single-dish survey towards 11 high-mass SFRs to search for molecular outflows: detection rate of 55%, C18O velocity gradients in some cases; massive YSOs, in the accretion phase. Paper in preparation 2. HCO+(1-0) and HCN(1-0) single-dish survey towards ~50 selected high-mass molecular clumps to search for infalling (and outflowing) motions: preliminary data analysis: star formation activity randomly distributed (age, surface density) 3. Infall towards 3 particular sources at different spatial scales Future 1. SiO survey (molecular jet search) and high-angular resolution imaging towards the sources with putative rotation + outflow 2. Data analysis; SiO survey (proposal accepted) and high-angular resolution observations towards selected targets 3. Data reduction; numerical code to fit/interpret absorption + emission line profiles

  30. INFALL IN PARTICULAR MASSIVE STAR FORMING REGIONS Signatures of infall: inverse P-Cygni profiles Infall can be detected in absorption against bright UCHII regions (inverse P-Cygni) Spectra of the CN(1-0) and (2-1) transitions seen in absorption towards G34.26+0.15, obtained with IRAM 30-m telescope Integrated CN(1-0) map of G34.26+0.15

  31. INFALL IN PARTICULAR MASSIVE STAR FORMING REGIONS V[R] derivation form single-dish + interferometry • Combination of single-dish and interferometric observations • Self-consistent numerical model •  • Velocity field

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