1 / 58

Molecules in high-mass star-forming regions – probing protostellar environments Karl M. Menten

Molecules in high-mass star-forming regions – probing protostellar environments Karl M. Menten (MPIfR). Orion: Most low-mass stars from together with high-mass stars. We know very little about high mass star formation, and the earlier the stages and

irma
Download Presentation

Molecules in high-mass star-forming regions – probing protostellar environments Karl M. Menten

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Molecules in high-mass star-forming regions – probing protostellar environments Karl M. Menten (MPIfR)

  2. Orion: Most low-mass stars from together with high-mass stars

  3. We know very little about high mass star formation, and the earlier the stages and the smaller the spatial scales the less we know.

  4. Willner et al. 1982 • How does one find HMPOs? • Infrared surveys Historically first in NIR (starting with the AFGL survey)

  5. The Willner et al. protostars became a bonanza for spectroscopists when ISO came and even before

  6. ISO SWS spectra of hot water (2 bending mode) Boonman & van Dishoeck 2003 Tex 250 K, 5 10-6 < X(H2O) < 6 10-5 Also gas phase SO2, CO2: Keane et al. 2001, Bonnman et al. 2003

  7. What about less developed objects than the Willner et al. protostars? • Expected to be deeply embedded • NIR-quiet Such objects were indeed found: Hot Cores • hot (>150 K) • dense (>106 cm-3) • compact (< a few thousand AU)

  8. Cesaroni et. 1998 NH3 (4,4) Finding High-Mass Protostellar Objects: Problem: Most known HMPO candidates (hot cores) were found (serendipi-tously) near HII regions Needed:A sample of pristine & isolateds HMPOs

  9. Systematic surveys for HMPOs: • From the mid 1990s on high-mass protostellar objects were discovered in systematic surveys. • Major efforts: • Molinari et al. (1996, 1998, 2000, see also Brand et al. 2001) • Sridharan/Beuther et al. (2002 a – d). • Selection criteria included: • IRAS colors identifying compact HII regions • dense gas tracers, e.g. • emission in the NH3 inversion lines (Molinari) or • CS J = 2-1 transition (Sridharan/Beuther; based on the CS survey by Bronfmanet al.), and • (Sridharan/Beuther) absence of strong radio continuum emission (to exclude already developed compact HII regions).

  10. HMPO surveys find, both, “genuine” HMPOs and UCHIIRs • Some results: • Massive high velocity outflows are found in 21 out of 26 sources mapped in CO (2-1) transition@11" resolution • (Beuther et al. 2002)  disk accretion everywhere

  11. Beuther et al. 2002 HMPOs: bolometer maps: > 10000 AU size dust cores:  Massive dense envelopes

  12. Surveys for HMPOs signposted by class II methanol masers: • Class II methanol masers (in the 6.7 and 12.2 GHz lines) are unambiguoustracers of high-mass star formation • Multi-wavelength study by Minier et al. finds class 0-like YSO clusters (Lsubmm/Lbol>1%, Td=30 K) to hot molecular cores (Lsubmm/Lbol=0.1%, Td=40 – 200 K). • Unbiased Galactic plane survey for class II CH3OH masers • Szymczak et al. 2002 • Ellingsen et al. 1996 • So far limited sensitivity/coverage: big improvement with Jodrell Bank multi-beam array RX Minier Talk

  13. Present day Example: Large-scale bolometer map of Cygnus-X star forming region (MAMBO/IRAM 30m) Motte et al. Find many more HMPOs! Unbiased, large area searches • LABOCA@APEX Galactic Plane survey • (perhaps in conjunction) with Herschel surveys • SCUBA-2 Molinari Poster Fich Poster

  14. Interestingly, submillimeter dust and molecule observations showed that many of the Willner et al. near-IR-loudprotostars looked at (sub)millimeter wavelengths in, both, dust and continuum emission very similar to near-IR-quiet protostars van der Tak et al. 2000a,b Could the near-IR loudness or silence be a viewing angle effect, as in the unified model for AGN?

  15. Dusty envelope  NIRQ protostar Torus Disk Collimated outflow  NIRL protostar

  16. AFGL 2591 NIR speckle imaging resolves inner wall of circumstellar material at the dust subli-mation radius (r = 40 AU) Preibisch et al. 2003 What is the nature of the NIR emission in NIR-loud protostars? AFGL 2591 also has a compact radio source of similar size! (van der Tak & Menten 2005)

  17. Orion-KL SMA VLA 

  18. Orion - I SiO masers + 43.2 GHz continuum Greenhill, Chandler et al.Reid & Menten 45 AU

  19. Chandler, Greenhill, et al.

  20. Chandler, Greenhill, et al. Excretion Disk?

  21. SiO Greenhill et al. • … plus: • large scale H2O outflow • large-scale shocked H2 • HH objects ??????????

  22. W49N H2O masers: • Bipolar high velocity outflow • Proper motion measurements via VLBI Another excretion disk? 1000 AU Gwinn, Moran, & Reid 1992

  23. Dust Free-free Radio continuum emission from HMPOs Recently, compact, weak, steep, rising thermal spectrum (S~2) radio emission (similar to Orion-I) has been found toward a number of other high-mass protostars. beam = 50 mas! Menten & van der Tak 2004: CRL 2136 Van der Tak & Menten 2005: AFGL 2591, W33A, NGC 7538-IRS9

  24. Orion-I 600+ GHz data point will mighttell! Beuther et al. 2005

  25. Radio emission from High-Mass Protostars • No obvious relationship between radio luminosity • and total luminosity - Panagia (1973) doesn't • work! • Radio emission is “choked off” (Walmsley 1995) • for high enough (“critical”) mass accretion rates: • Radio luminosity is only a tiny fraction of total • luminosity • Almost certainly is the protostar itself!

  26. To study the immediate neighborhood of HMPOs (disks), one needs  High resolution observations • To study innermost regions (< 100 AU) • need B< 0.05” • Problem:Brightness sensitivity • TB(K) = 5 105S(mJy)/2(GHz) • With today's interferometers you reach rms noise levels of a few mJy (for lines) •  TB of dozens tens of K … and prohibitive noise levels at higher resolutions (even if you could realize them).

  27. Beating Rayleigh-Jeans with ALMA: collecting area does it!!

  28. Because of Rayleigh-Jeans, only maser lines can presently studied at “interesting” resolutions High (< 0.1”) spatial resolution spectroscopy of thermal lines has to await ALMA

  29. Surveys found lots of Hot Cores Orion-KL 2000 AU Blake et al. 1996 * With astonishing chemical diversity * small-scale structure

  30. Chemical Diversity: The W3(OH) Region (Turner & Welch 1984) dust free-free (Wyrowski et al. 1999) Hot cores around dusty HMPO(s) and UCHIIRs

  31. Hot core chemistry around protostars revp Van Dishoeck & Blake 1998, ARA&A

  32. r(D=1) > revp r(D=1) < revp No hot molecules observable r(D=1) = f[,mD] revp = f(L*) (D=1) “somewhere” in the far-infrared – submillimeter range

  33. r(D=1) > r(n > ncrit) r(D=1) < r(n > ncrit) r(n > ncrit) = f(mgas,) r(n = ncrit) “somewhere” in the far-infrared – submillimeter range

  34. You cannot see molecular emission from within the dust photosphere!

  35. Sgr B2 Goicoechea & Cernichao 2004 • In molecules: • (almost) only absorption • only simple species (hydrides, C-chains) • from extended envelope, not from hot core Poster

  36. Why does ISO not see hot core molecules in Sgr B2? http://www.ph1.uni-koeln.de/cgi-bin/cdmsinfo?file=e032504.cat

  37. Why does ISO not see hot core molecules in Sgr B2? • dust photosphere/critical density sphere effect unclear • beam dilution? • ISOHerschel • 80” (150 m) 20” (300 m) • spectral dilution? • ISO LWSHerschel • Grating Fabry-Perot • max 300 10000 300000 I don’t think so, but this should be looked into!

  38. The Big Question: Will dust photosphere or critical density barrier prohibit studies of hot, very dense regions at far-infrared wavelengths? Should be addressed now! Far-reaching consequences on the scientific program for Herschel and the case for far-infrared space interferometry, and ALMA. Not only for high-mass star-forming regions, but also, e.g., for the inner regions of ULIRGs and AGN accretion disks/tori.

  39. So you’ve found lots of HMPOs – what do you do now? • Of course: Follow up with ALMA • But how does one do this? • Problems: • structure on many scales from <0.01” • to tens of arc seconds (continuum) or • to arcseconds (hot lines) • multi-configuration imaging • Very many lines from many molecules – and one doesn’t want maps of S (or TB) but maps of Tkin, n, X and fit dynamical models

  40. IRAM 30m telescope Sgr B2-N “Large Molecule Heimat” 10 minutes per spectrum  confusion limit (Belloche, Comito, Hieret, Leurini, Menten, Schilke) 3 mm region (70 – 116 GHz) in 500 MHz chunks 2000 – 3000 lines!!!! With ALMA it will be possible to observe that whole spectral range within 10 minutes to confusion limit

  41. To do science with (3D) line surveys one needs very advanced data analysis tools: • Automatic line identification and information extraction (fluxes, velocities) • requires up-tp-date “living” molecular spectroscopy database • LTE analysis •  maps of N(X), Trot • non-LTE analysis (LVG/Monte Carlo least sqares method; see Leurini et al. 2004 for CH3OH) • mapsofn, Tkin, [X/H2] • Fit dynamical models

  42. What do we have now? • Not even a software package that provides basic imaging capability! • Dispersed (and very low manpower level) efforts to develop data modeling and smart analysis tools • Uncertain future for spectroscopy databases

  43. Even more basic… • Apart from smart data analysis tools, we need: • For observing, calibration, & imaging: • computer-aided observation preparation • * (semi)automatic setup tools for frequency selection, mosaicing, … • (largely) automatic • * calibration • * imaging + selfcalibration, • * mosaicing, multi-configuration combination, 0-spacing addition • … and we don’t even have aips++ working!

  44. To end on a positivenote… Considerable effort is put into Herschel/HIFI observing and data analysis software

  45. Thanks for your attention

  46. Simultaneous Flaring in both strong Class II methanol maser lines 6.7 GHz 12.2 GHz

  47. Maximum: 1.48 cycles/yr = 240 +/- 6 days

More Related