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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 the smaller the spatial scales the less we know. How does one find HMPOs? • Infrared surveys Historically first in NIR (starting with the AFGL survey) Willner et al. 1982 The Willner et al. protostars became a bonanza for spectroscopists when ISO came and even before ISO SWS spectra of hot water (2 bending mode) Tex 250 K, 5 10-6 < X(H2O) < 6 10-5 Boonman & van Dishoeck 2003 Also gas phase SO2, CO2: Keane et al. 2001, Bonnman et al. 2003 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) Finding High-Mass Protostellar Objects: Problem: Most known HMPO candidates (hot cores) were found (serendipitously) near HII regions Cesaroni et. 1998 NH3 (4,4) Needed: A sample of pristine & isolateds HMPOs 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 Bronfman et al.), and • (Sridharan/Beuther) absence of strong radio continuum emission (to exclude already developed compact HII regions). 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) HMPOs: bolometer maps: > 10000 AU size dust cores: Massive dense envelopes Beuther et al. 2002 Surveys for HMPOs signposted by class II methanol masers: Class II methanol masers (in the 6.7 and 12.2 GHz lines) are unambiguous tracers of highmass 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 Find many more HMPOs! Unbiased, large area searches • LABOCA@APEX 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. 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? Dusty envelope NIRQ protostar Torus Disk Collimated outflow NIRL protostar What is the nature of the NIR emission in NIR-loud protostars? AFGL 2591 NIR speckle imaging resolves inner wall of circumstellar material at the dust sublimation radius (r = 40 AU) Preibisch et al. 2003 AFGL 2591 also has a compact radio source of similar size! (van der Tak & Menten 2005) Orion-KL SMA VLA Orion - I SiO masers + 43.2 GHz continuum 45 AU Greenhill, Chandler et al. Reid & Menten Chandler, Greenhill, et al. Chandler, Greenhill, et al. … plus: • large scale H2O outflow • large-scale shocked H2 • HH objects SiO Greenhill et al. W49N H2O masers: • Bipolar high velocity outflow • Proper motion measurements via VLBI Another excretion disk? 1000 AU Gwinn, Moran, & Reid 1992 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 beam = 50 mas! Menten & van der Tak 2004: CRL 2136 Van der Tak & Menten 2005: AFGL 2591, W33A, NGC 7538-IRS9 Orion-I Beuther et al. 2005 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! 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). Beating Rayleigh-Jeans with ALMA: collecting area does it!! 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 Surveys found lots of Hot Cores * With astonishing chemical diversity * small-scale structure Orion-KL 2000 AU Blake et al. 1996 Hot cores around dusty HMPO(s) and UCHIIRs Chemical Diversity: The W3(OH) Region (Turner & Welch 1984) dust free-free (Wyrowski et al. 1999) Hot core chemistry around protostars revp Van Dishoeck & Blake 1998, ARA&A r(D=1) > revp r(D=1) < revp r(D=1) = f[,mD] revp = f(L*) (D=1) “somewhere” in the far-infrared – submillimeter range 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 You cannot see molecular emission from within the dust photosphere! Sgr B2 In molecules: • (almost) only absorption • only simple species (hydrides, C-chains) • from extended envelope, not from hot core Goicoechea & Cernichao 2004 Poster Why does ISO not see hot core molecules in Sgr B2? http://www.ph1.uni-koeln.de/cgi-bin/cdmsinfo?file=e032504.cat 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 LWS Grating max 300 Herschel Fabry-Perot 10000 300000 The Big Question: Will dust photosphere or critical density barrier prohibit studies of hot, very dense regions at farinfrared wavelengths? Should be addressed now! Far-reaching consequences on the scientific program for Herschel and the case for farinfrared 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. 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 IRAM 30m telescope Sgr B2-N “Large Molecule Heimat” 3 mm region (70 – 116 GHz) in 500 MHz chunks 2000 – 3000 lines!!!! 10 minutes per spectrum confusion limit (Belloche, Comito, Hieret, Leurini, Menten, Schilke) With ALMA it will be possible to observe that whole spectral range within 10 minutes to confusion limit 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) maps of n, Tkin, [X/H2] • Fit dynamical models 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 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! To end on a positive note… Considerable effort is put into Herschel/HIFI observing and data analysis software Thanks for your attention Simultaneous Flaring in both strong Class II methanol maser lines 6.7 GHz 12.2 GHz Maximum: 1.48 cycles/yr = 240 +/- 6 days Flare Behaviour 12.2 GHz 4 flares folded (modulo 240 d) Steep rise 6.7 GHz 5 flares folded Remarkably all flares have the same temporal behaviour: Steep (~10 d) rise and slow (~100 d) decline “E ” S(15 GHz) = 15 mJy Class II MMs Garay et al. 1993 Minier et al. (2003) VLBA X X Goedhart et al. (2003) Minier et al. (2003) VLBA 30 days = 5200 AU = 70 mas => D = 74 kpc!! => something's wrong! 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 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 several tens of K … and prohibitive noise levels at higher resolutions (even if you could realize them). Beating Rayleigh-Jeans with ALMA: collecting area does it!! 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 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!