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

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Presentation on theme: "Molecules in high-mass star-forming regions – probing protostellar environments Karl M. Menten (MPIfR)"— 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 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 T ex  250 K, < X(H 2 O) < ISO SWS spectra of hot water ( 2 bending mode) Boonman & van Dishoeck 2003 Also gas phase SO 2, CO 2 : 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 (>10 6 cm -3 ) compact (< a few thousand AU)

8 HMPO Finding High-Mass Protostellar Objects: Needed: A sample of pristine & isolateds HMPOs Problem: Most known HMPO candidates (hot cores) were found (serendipi- tously) near HII regions Cesaroni et NH 3 (4,4)

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 NH 3 inversion lines (Molinari) or CS J = 2-1 transition (Sridharan/Beuther; based on the CS survey by Bronfman et 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) resolution (Beuther et al. 2002)  disk accretion everywhere

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

12 Surveys for HMPOs signposted by class II methanol masers: unambiguous Class II methanol masers (in the 6.7 and 12.2 GHz lines) are unambiguous tracers of high- mass star formation Multi-wavelength study by Minier et al. finds class 0-like YSO clusters (L submm /L bol >1%, T d =30 K) to hot molecular cores (L submm /L bol =0.1%, T d =40 – 200 K). Unbiased Galactic plane survey for class II CH 3 OH masers Szymczak et al Ellingsen et al So far limited sensitivity/coverage: big improvement with Jodrell Bank multi-beam array RX Minier Talk

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

14 Interestingly, submillimeter dust and molecule observations showed that many of the Willner et al. near-IR-loud protostars 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 Torus Disk Collimated outflow  NIRQ protostar  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 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

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

20 Chandler, Greenhill, et al.

21 Excretion Disk?

22 Greenhill et al. SiO … plus: large scale H 2 O outflow large-scale shocked H 2 HH objects ??????????

23 W49N H 2 O masers: Bipolar high velocity outflow Proper motion measurements via VLBI Gwinn, Moran, & Reid AU Another excretion disk?

24 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. Dust Free-free Menten & van der Tak 2004: CRL 2136 Van der Tak & Menten 2005: AFGL 2591, W33A, NGC 7538-IRS9  beam = 50 mas!

25 Orion-I Beuther et al GHz data point will mighttell!

26 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!

27 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  T B (K) =  S(mJy)/ 2 (GHz) With today's interferometers you reach rms noise levels of a few mJy (for lines)   T B of dozens tens of K … and prohibitive noise levels at higher resolutions (even if you could realize them).

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

29 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

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

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

32 Van Dishoeck & Blake 1998, ARA&A Hot core chemistry around protostars r evp

33 r(  D =1) > r evp r(  D =1) < r evp r(  D =1) = f[,m D ] r evp = f(L * ) (  D =1) “somewhere” in the far-infrared – submillimeter range No hot molecules observable

34 r(  D =1) > r(n > n crit ) r(n = n crit ) “somewhere” in the far-infrared – submillimeter range r(  D =1) n crit ) r(n > n crit ) = f(m gas, )

35 You cannot see molecular emission from within the dust photosphere!

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

37 Why does ISO not see hot core molecules in Sgr B2?

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

39 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.

40 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 T B ) but maps of T kin, n, X and fit dynamical models

41 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  10 minutes per spectrum  confusion limit (Belloche, Comito, Hieret, Leurini, Menten, Schilke) IRAM 30m telescope Sgr B2-N “Large Molecule Heimat”

42 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), T rot non-LTE analysis (LVG/Monte Carlo least sqares method; see Leurini et al for CH 3 OH)  maps of n, T kin, [X/H 2 ] Fit dynamical models

43 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

44 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!

45 positive To end on a positive note… Considerable effort is put into Herschel/HIFI observing and data analysis software

46 Thanks for your attention

47

48

49 6.7 GHz 12.2 GHz Simultaneous Flaring in both strong Class II methanol maser lines

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

51 Flare Behaviour 12.2 GHz 4 flares folded (modulo 240 d) 6.7 GHz 5 flares folded Steep rise Remarkably all flares have the same temporal behaviour: Steep (~10 d) rise and slow (~100 d) decline

52 “E ” S(15 GHz) = 15 mJy Class II MMs Garay et al. 1993

53 Minier et al. (2003) VLBA

54 X X Goedhart et al. (2003) 30 days = 5200 AU = 70 mas => D = 74 kpc!! => something's wrong! 70mas = 30days

55 Surveys are useful …... aber der Teufel liegt im Detail  High resolution observations To study innermost regions (< 100 AU) need  B < 0.05” Problem: Brightness sensitivity  T B (K) =  S(mJy)/ 2 (GHz) With today's interferometers you reach rms noise levels of a few mJy (for lines)   T B of several tens of K … and prohibitive noise levels at higher resolutions (even if you could realize them).

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

57 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

58 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!


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