Breaking Barriers in Massive Star Formation with Stellar Interferometry

Willem-Jan de Wit (ESO)Rene Oudmaijer (Leeds)Melvin Hoare (Leeds)Hugh Wheelwright (Leeds)

What are the dominant structures emitting in N-band?What are the dominant structures emitting in N-band?

Spherical models:

ISO-SWS

N-band

MIDI at the VLTIMIDI at the VLTI

Mid-IR beam combiner (N-band) Combining 2 VLTI beams (UTs or ATs) Spectrally dispersed fringes (30 & 230) Baselines 10 to 200 meters (10 mas) Visibilities

Leinert et al. (2004): MIDI instrument Haguenaur et al. (2008): VLTI architecture

13 micron 8 micron

The case of W33A: jets and outflows

JCMT/HARP 12CO(3-2):

L = 105 Lo

Dkin

= 3.8 kpc Weak, compact radio emission (Rengarajan & Ho 1995) Broad single peaked HI emission (Bunn et al. 1995) Fast bipolar jet (Br (Davies et al. 2010)

K-band (UKIDSS), VLTI baselines:

Davies et al. 2010

milli-arcsecond

mill

i-a

rcse

con

d

The case of W33A: jets and outflows

JCMT/HARP 12CO(3-2):

L = 105 Lo

Dkin

= 3.8 kpc Weak, compact radio emission (Rengarajan & Ho 1995) Broad single peaked HI emission (Bunn et al. 1995) Fast bipolar jet (Br (Davies et al. 2010)

K-band (UKIDSS), VLTI baselines:

Laser-guide star assisted NIFS at Gemini North (Davies et al. 2010)

4 AU

The case of W33A: jets and outflows

JCMT/HARP 12CO(3-2):

L = 105 Lo

Dkin

= 3.8 kpc Weak, compact radio emission (Rengarajan & Ho 1995) Broad single peaked HI emission (Bunn et al. 1995) Fast bipolar jet (Br (Davies et al. 2010)

K-band (UKIDSS), VLTI baselines:

Davies et al. 2010

milli-arcsecond

mill

i-a

rcse

con

d

W33A MIDI observables

7 8 9 10 11 12 13

FLUX spectrum Visibility spectrum

(micron) (micron)

4 baselines Near perpendicular PAs Baselines stretching between 40 and 60 meters

W33A MIDI observables

7 8 9 10 11 12 13

FLUX spectrum Visibility spectrum

(micron) (micron)

4 baselines Near-perpendicular PAs Baselines stretching between 40 and 60 meters Equivalent Gaussian FWHM sizes between 95 and 115AU

No flux95AU

W33A model fit

Model

350 micron:

Near-IR:

Van der Tak et al. (2000)

Axi-symmetric dust radiative transfer code (Whitney et al. 2002) TSC Envelope, outflow cavity, and disk

Observed Model

H-band

K-band

H - K

W33A model fit (cont.)

7.5 8.5 9.5 10.5 11.5 12.5

MIDI Visibilities:

Dust model parameters:

No disk, only envelope (cavities) M

infall = 7 10-4 M

o/yr

Rsub

= 25 AU (nominal) A

v = 230

Teff

= 35000 K R

* = 8.5 R

o M

* = 25 M

o 2* = 20o (opening angle)

2200AU

Monochromatic images on the sky:

de Wit et al. 2010

W33A and disk emissionDisk limits from N-band interferometry: Dust disk : M < 0.01M

o

Accretion disk : Macc

< 10-3 Mo/yr

Davies et al. 2010

Disk signature in AFGL 2136 ?

UKIDSS K-band

L= 7e4 Lsol D= 2.0 Kpc Polarization disk (Murakawa et al. 2008) Arcmin bipolar CO outflow (Kastner et al. 1995) Compact, 70AU radio emission (Menten & Van der Tak 2004)

K-band polarization (Murakawa et al. 2008)

1 arcminute

outflow

Same procedure as W33A (2.5D axisymmetric dust radiative transfer) Fit envelope emission (SED, 24.5 mu and N-band short spacing) Necessity of compact emitting source at <8.5 micron for MIDI visibilities

Disk signature in AFGL 2136 ?

Same procedure as W33A (2.5D axisymmetric dust radiative transfer) Fit envelope emission (SED, 24.5 mu and N-band short spacing) Necessity of compact emitting source at <8.5 micron for MIDI visibilities Either accretion disk or supergiant star to fit N-band dispersed visibilities

Disk signature in AFGL 2136 ?

Monnier et al. (2009)

Same procedure as W33A (2.5D axisymmetric dust radiative transfer) Fit envelope emission (SED, 24.5 mu and N-band short spacing) Necessity of compact emitting source at <8.5 micron for MIDI visibilities Either accretion disk or supergiant star to fit N-band dispersed visibilities

Disk signature in AFGL 2136 ?

Same procedure as W33A (2.5D axisymmetric dust radiative transfer) Fit envelope emission (SED, 24.5 mu and N-band short spacing) Short spacing + SED : 120 AU dust radius Necessity of compact emitting source at <8.5 micron for MIDI visibilities Either accretion disk or supergiant star to fit N-band dispersed visibilities M

acc : 3 10-3 M

o/yr

Disk signature in AFGL 2136 ?

1.5” 8 micron

ConclusionsConclusions

N-band interferometry is able to provide important new insights in the formationof high-mass stars.

In W33A: N-band emission at 100 AU scale is dominated by warm dust in the interface between outflow cavity and envelope

Contribution by accretion disk is similar or less than TSC envelope infall rate

AFGL 2136: evidence for compact emission: supergiant star or accretion disk

Near future with VLTI

PIONIER : 4 beam combiner H & K bands, R=40Commissioning & early science November 2010 (JP Berger et al. 2010)

MATISSE: 4 beam combinerL, M, N bands (R=30, 1500)2014 (Wolff et al.)

MIDI observations of IRAS 13481

20AU

2.2 micron

8.0 micron

Image cuts 0.1% and 10% of maximum Visibilities: over-resolved component 40% flux

AFGL 2136 IRS1 (de wit et al. In prep) AFGL 2136 IRS1 (de wit et al. In prep) W33A (de Wit et al 2010)W33A (de Wit et al 2010) IRS9A (Vehoff et al. 2010)IRS9A (Vehoff et al. 2010)