Molecules in high-mass Molecules in high-mass star-forming regions –star-forming regions –

probing protostellar environmentsprobing protostellar environments

Karl M. MentenKarl M. Menten(MPIfR)(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 scalesthe less we know.

Willner et al. 1982

How does one find HMPOs?• Infrared surveys

Historically first in NIR (starting with

the AFGL survey)

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

Tex 250 K,

5 10-6 < X(H2O) < 6 10-5

ISO SWS spectra of hot water (2 bending mode)

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 HHigh-MMass PProtostellar OObjects:

Needed: A sample of pristine & isolateds HMPOs

Problem:Most known HMPO candidates (hot cores) were found (serendipi-tously) near HII regions

Cesaroni et. 1998 NH3 (4,4)

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 UCHIIRsSome 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

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 unambiguousunambiguous tracers 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. 1996So far limited sensitivity/coverage: big improvement with Jodrell Bank multi-beam array RX

Minier Talk

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.

Molinari Poster

Fich Poster

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

Torus

Disk

Collimatedoutflow

NIRQ protostar

NIRL protostar

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)

Orion-KL

SMA

VLA

Orion - I

SiO masers + 43.2 GHz continuum

Greenhill, Chandler et al. Reid & Menten45 AU

Chandler, Greenhill,

et al.

Chandler, Greenhill, et al.

Excretion Disk?

Greenhill et al.

SiO

… plus:

• large scale H2O outflow

• large-scale shocked H2

• HH objects

????

????

??

W49N H2O masers:

• Bipolar high velocity outflow

• Proper motion measurements via VLBI

Gwinn, Moran, & Reid 1992

1000 AU

Another excretion disk?

Radio continuum emission from HMPOsRecently, 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!

Orion-I

Beuther et al. 2005

600+ GHz data point

will mightte

ll!

Radio emission from High-Mass Protostars

• No obvious relationship between radio luminosityand 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 totalluminosity

• Almost certainly is the protostar itself!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

* With astonishing chemical diversity * small-scale structure

Surveys found lots of Hot Cores

2000 AU

Orion-KL

Blake et al. 1996

Hot cores around dusty HMPO(s) and UCHIIRs

Chemical Diversity: The W3(OH) Region

(Wyrowski et al. 1999)

dust free-free

(Turner & Welch 1984)

Van Dishoeck & Blake 1998, ARA&A

Hot core chemistry around protostars

revp

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

No hot molecules observable

No hot molecules observable

r(D=1) > r(n > ncrit)

r(n = ncrit) “somewhere” in the far-infrared – submillimeter range

r(D=1) < r(n > ncrit)

r(n > ncrit) = f(mgas,)

You cannot see molecular emission from within the dust photosphere!

Goicoechea & Cernichao 2004

Sgr B2

Poster

In molecules: • (almost) only absorption• only simple species (hydrides, C-chains)• from extended envelope, not from hot core

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 corehot 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 Herschel

Grating Fabry-Perot

max 300 10000 300000

I don’t t

hink so, but th

is

should be looked in

to!

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.

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

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”

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 Not even a software package that provides basic imaging capability!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 positivepositive note…

Considerable effort is put into Herschel/HIFI observing and data analysis software

Thanks for your attention

6.7 GHz

12.2 GHz

Simultaneous Flaring in both strong Class II methanol maser lines

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

Flare Behaviour

12.2 GHz4 flares folded(modulo 240 d)

6.7 GHz5 flares folded

Steep rise

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

Minier et al. (2003) VLBA

X

X

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

70m

as

=

30days

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 luminosityand 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 totalluminosity

• Almost certainly is the protostar itself!Almost certainly is the protostar itself!