modeling and observations of disks around intermediate and high mass protostars mayra osorio...

Modeling and Observations of Disks around Modeling and Observations of Disks around intermediate and High Mass Protostarsintermediate and High Mass Protostars

Mayra Osorio (Instituto de Astrofísica de Andalucía-CSIC, Spain) Mayra Osorio (Instituto de Astrofísica de Andalucía-CSIC, Spain)

Colaborators:Colaborators:

G. Anglada, C. Carrasco-Gonzalez, (IAA-CSIC, Spain)G. Anglada, C. Carrasco-Gonzalez, (IAA-CSIC, Spain)

J.M. Torrelles (ICE-CSIC, Spain), P. D’Alessio (CRyA-UNAM, Mexico), J.M. Torrelles (ICE-CSIC, Spain), P. D’Alessio (CRyA-UNAM, Mexico),

Great Barriers in High Mass Star Formation, Townsville 2010

OverviewOverview

(Patel et al. 2005)730 AU

Cepheus A HW2 Disk

It has been shown that rotation is relevant in massive star formation. Several elongated structures with a velocity gradient along the major axis have been found around massive protostars (e.g., Cesaroni et al.). These structures can be classified as:

Toroids: Large structures (10,000-20,000 AU), with a mass considerably larger than that of the central star, therefore unstable.

Compact disks: Structures with sizes similar to that of the disks around intermediate- and low-mass stars (20-300 AU), a mass comparable to that of the central star.

(Beltran et al. 2005)

OutlineOutline

I will present new, high-angular resolution results that suggest the presence of compact disks around two protostars:

•IRAS18162-2048 (GGD 27), the driving source of HH80-81 (high-mass protostar).

•HD169142 (intermediate-mass protostar).

The disk structure has been modeled using physically self-consistent accretion disk models developed by D’Alessio et al (1998, 1999, 2001, 2006, 2010), which previously were successfully applied to disks around low- and intermediate-mass protostars.

• Distance = 1.7 kpc (Rodriguez et al. 1980).• Large (5.3 pc) and highly collimated (opening

angle ~1 deg) radio jet (Marti et al. 1993).

• Central source: LIRAS ~ 17,000 Lsun (Yamashita et al. 1989).

• Hot molecular gas (Qiu & Zhang 2009). No photoionized HII region. Therefore, it is in the HMC phase.

HH 80-81HH 80-81

(VLA 6cm Marti et al. 1993; beam=7”x5”)

VLA6cm





• Spitzer mid-IR observations reveal a bipolar cone-shaped cavity surrounding the narrow radio jet. The HH80-81 system is a good example of a two-component outflow emanating from a massive star (similar to other outflows observed in low mass YSOs

HH 80-81HH 80-81

(VLA 6cm Marti et al. 1993; beam=7”x5”)

Spitzer mid-IR (8 micron) Qiu et al 2008





• Spitzer mid-IR observations reveal a bipolar cone-shaped cavity surrounding the narrow radio jet. The HH80-81 system is a good example of a two-component outflow emanating from a massive star (similar to other outflows observed in low mass YSOs

• IR/cm source at ~3000 AU (2”) NE from central source (Aspin 1993, Qiu et al. 2008, Gomez et al. 1995, Carrasco-Gonzalez et al. 2010).

Since HH 80-81 is a highly collimated jet, it is expected to be associated with a circumstellar accretion disk.

HH 80-81HH 80-81VLA 3.6cm beam=0.4”x0.2” Gomez et al. 1995

Marginally resolved circumstellar dust emission has been detected around the HH80-81 central source.

VLA (7mm) beam ~ 0.4”

SMA (860 µm) + VLA (6cm)

(Gomez et al 2003)

Compact 860 micron source with a size of ~1200 AU

(beam=1”x0.7”)

SMA (860 µm)

Disk+envelope?

HH80-81HH80-81

850 AU1700 AU

Circumstellar molecular emission has been also detected around the HH80-81 central source.

SMA beam = 3.5”x2.8”

SMA (SO molecule) + VLA (3.6cm)

Velocity gradient of SO (may be affected by VLA2)

HH80-81HH80-81

SMA beam = 1.20”x1”

(Qiu & Zhang 2009) VLA2

1700 AU

VLA observations at 7mm and 1.3 cm

(A configuration)

7mm beam = 0.05” ~ 80 AU

1.3cm beam = 0.08” ~ 130 AU

The circumstellar emission is angularly resolved: quadrupolar morphology, which can be interpreted as a superposition of two overlapping elongated sources.

HH80-81 (Our Observations)HH80-81 (Our Observations)

Color Contours

Two-component decomposition

• Elongation perpendicular to jet suggesting a “true” compact disk.

• Size ~400 AU

• In order to illustrate if this interpretation is consistent with the data (7mm flux density and image), we calculated the emission of an irradiated accretion disk.

HH80-81 (Our Observations)HH80-81 (Our Observations)

Color

Contour COMPACT DISK IN HH80-81

The main heating mechanisms are:• Viscous dissipation• Stellar irradiation• Accretion shock The -prescription (Shakura & Sunyaev

1973) is adopted:

Macc=3turb turb =kTmid/g

=gas surface density turb=turbulent viscosity

=viscosity coefficient. Vertical settling of the particles in the

disk mid-plane is included assuming a standard grain-size distribution n(a)~a-p

• amin=0.005 m, amax~1 m (upper layers)

• amin=0.005 m, amax~1mm (mid-plane)

HH80-81 (Modeling)HH80-81 (Modeling)These models yield the vertical structure of the disk self-consistent with the stellar parameters (M*, R*, L*), without using power-law approximations for the temperature and surface density profiles.

D’Alessio et al 2006, 2010

• We explore inclination angles of the disk close to the edge-on position, since the molecular outflow/jet is almost in the plane of the sky.

• Macc < 3 x10-4 Msun/yr, since higher accretion rates would imply

Ltot = L* + Lacc > Lbol

• We adopted a star of 10 Msun

• Standard viscosity (=0.1)

L*Macc Lacc T(Rdisk)* Rdisk Mdisk i Toomre

(Lsun) (Msun/yr) (Lsun) (K) (AU) (Msun) (deg) Q-parameter

104 1x10-4 5x103 90 400 17 80 0.3

HH 80-81 (Modeling)HH 80-81 (Modeling)

Disk parameters

7mm data + Gaussian fit

Relatively isolated Herbig Ae star.Spectral type AV5 (Grady et al 2007).Age = 10 Myr (Meeus et al 2001).Distance = 145 pc (Sylvester et al

1996).

Characteristics of the observed SED:

• Infrared excess

• A spectral index of ~2.5 in the mm-submm range, implying a shallow dependence of dust opacity with frequency ( 0.5)

• No 3.6cm emission (3 = 0.08mJy). No cm emission in the VLA archive data at 1.3, 2, 6cm. Therefore no radio jets and the free-free contamination is negligible.

• Absence of 10 m Silicate absorption

HD 169142HD 169142

In summary, this is a rather evolved system, where the envelope is gone (Meeus et al 2001), the mass infall/outflow is halted, and the emission is dominated by the disk. The well sampled SED, whose emission is uncontaminated from either an envelope or a radio jet, makes of HD169142 an unique case to model the disk and determine robustly its physical structure.

(microns)

HD 169142 DiskHD 169142 Disk VLA 7mm Cnbbeam=1”x0.4”

(*www.astrosmo.unam.mx/~dalessio)

Previous VLA observations (Dent, Torrelles, Osorio et al. 2006):

Relatively strong (4mJy) 7mm emission.

Source unresolved (< 1”).

We modeled the SED, including our 7mm measurement, using the models of the online database (*) of irradiated accretion disks (D’Alessio et al. 2005). We got a reasonable fit with the following parameters:

145 AU

HD 169142 Disk (Observations)HD 169142 Disk (Observations)

New VLA observations at 7mm in the A configuration:

VLA 7mmConf. CnBbeam=1”x0.4”

New map using all the data (CnB+A configurations)

(map reconstructed using a circular beam)

Previous map

145 AU

VLA 7mmConf. A+CnB beam=0.2”

30 AU

HD 169142 Disk (Observations)HD 169142 Disk (Observations)

The source is angularly resolved • Elongated morphology

• Size: 60 AU x 30 AU (==> i ~ 60o)• P.A. = 120o

• Extended, warped structure at its edges

• These results make of HD 169142 one of the few intermediate-mass protostars where the circumstellar accretion disk is angularly resolved at scales < 50 AU.

30 AU

VLA 7mm (Conf A+CnB, beam=0.2”)

HD 169142 Disk (Modeling)HD 169142 Disk (Modeling)

Lstar Macc Lacc Rdisk Mdisk

i T(Rdisk)

(Lsun) (Msun/yr) (Lsun) viscosity (AU) (Msun) (deg) (K)

17 3x10-9 0.1 9x10-4 170 0.17 60 27

We will model the SED with the irradiated accretion disk models of D’Alessio et al., and using the 7 mm image as an additional constraint. In this new modeling we consider lower mass accretion rates than in Dent et. 2006. The mass accretion rate adopted in Dent et al. (10-8 Msun/yr) exceeds the mass accretion rate limit inferred from UV data (Grady et al. 2007). Furthermore, there is evidence that both infall and outflow have almost halted.

opacity SED7mm Intensity Profile

big grains

HD 169142 DiskHD 169142 Disk

However, other authors have inferred that the HD 169142 disk is more extended (R~250 AU), and that it is observed almost face-on.

• 1.-Infrared polarization images (Kuhn et al 2001)

• 2.-CO images (Raman et al 2006, Panic et al. 2008)

• 3.-HST NICMOS scattered light (Grady et al. 2007)

1

1

2, 3

1.7”(250AU)

1.7”(250AU)

1.7”(250AU)

Kuhn et al 2001

Kuhn et al 2001

Raman et al 2006, Panic et al. 2008


VLA 7mm, beam=0.2”

30 AU

A possible way to reconcile all these results and our observations is to assume that the structure observed at 7mm does not trace the full extent of the disk but only the inner region (~20 AU) where planet formation has already started.

A map with improved angular resolution (beam=0.18”x0.10”) shows a knotty substructure with a spiral pattern, that is suggestive of planet formation.


VLA 7mm (conf A+CnB), beam=0.18”x0.10”

A possible way to reconcile all these results and our observations is to assume that the structure observed at 7mm does not trace the full extent of the disk but only the inner region (~20 AU) where planet formation has already started.

A map with improved angular resolution (beam=0.18”x0.10”) shows a knotty substructure with a spiral pattern, that is suggestive of planet formation.

Position of HD169142

AB C

D

30 AU


Knot B C D

R 14AU 18AU 41AUOrbital period

36yr 53yr 186yr

Angularspeed 10o yr-1 7o yr-1 2oyr-1

PA(2006-2010)

40o 30o 8o

These large PA should be easily observable with future observations with the EVLA. We have obtained EVLA observing time to measure the PA variations to test the planet (or substellar companion) formation hypothesis.

VLA 7mm, beam=0.18”x0.10”

HD 169142For a 2 Msun star at 145pc

AB C

D

30 AU

CONCLUSIONS• We have obtained high angular resolution VLA data at 7mm that

suggest the presence of compact disks associated with the high-mass protostar that drives the HH80-81 jet, and with the intermediate mass protostar HD169142.

• We have modeled the observed emission in HD169142 and we have found evidence of possible planetary formation in the disk. This hypothesis can be easily tested with a second epoch of VLA observations.

Models for the molecular Models for the molecular and dust emission and dust emission

of high-mass protostarsof high-mass protostars

Mayra Osorio (Instituto de Astrofísica de Andalucía-CSIC, Spain) Mayra Osorio (Instituto de Astrofísica de Andalucía-CSIC, Spain)

Colaborators:Colaborators:

Susana Lizano (CRyA-UNAM, Mexico), Paola D’Alessio (CRyA-UNAM, Mexico), Susana Lizano (CRyA-UNAM, Mexico), Paola D’Alessio (CRyA-UNAM, Mexico),

Guillem Anglada (IAA-CSIC, Spain)Guillem Anglada (IAA-CSIC, Spain)

HD 169142 DiskHD 169142 Disk7mm VLA observations. The maps show combine A+B configurations

It has a well sample SED from near IR to cm wavelengths

No silicate absorption

Flat slope in the mm range

No strong emission at cm wavelengths associate to jets

All these evidences together suggest that the system is evolved, the envelope is gone and the dust and gas emission are only comming from the disk

In

The Spitzer mid-IR observations (angular resolution ~2”-4”) reveal a bipolar cone-shaped cavity surrounding the narrow radio jet. So, the HH80-81 system is a good example of a two-component outflow

emanating from a massive star. This is similar to other outflows observed in low mass YSOs.

HH 80-81HH 80-81

(Qiu et al 2008)

The 5.5 and 8 microns peaks coincide with the 7mm emission detected by Gomez et al (2003).

modeling and observations of disks around intermediate and high mass protostars mayra osorio...

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