sma observations of the herbig ae star ab aur nagayoshi ohashi (asiaa) main collaborators: s.-y. lin...

SMA Observations of SMA Observations of

the Herbig Ae star the Herbig Ae star AB AurAB Aur

Nagayoshi Ohashi (ASIAA)Nagayoshi Ohashi (ASIAA)

Main Collaborators: S.-Y. Lin1, J. Lim2, P. Ho3, M. Momose4, M. Fukagawa5 (1. NTHU, 2. ASIAA, 3. SAO, 4. Ibaraki Univ., 5. Uinv. Of Tokyo)

This study is a part of the master thesis of S.-Y. Lin.This study is a part of the master thesis of S.-Y. Lin.

Circumstellar Disks Circumstellar Disks around Herbig Ae starsaround Herbig Ae stars

Herbig Ae stars are:Herbig Ae stars are: PMSs with intermediate stellar masses (~2 Mo), PMSs with intermediate stellar masses (~2 Mo),

counterparts of T Tauri stars.counterparts of T Tauri stars. known to be accompanied with circumstellar disks known to be accompanied with circumstellar disks

(CDs), which are considered to be sites of planets (CDs), which are considered to be sites of planets formation.formation.

Possible progenitors of Vega-type stars with debris Possible progenitors of Vega-type stars with debris disks, some of which are believed to have already disks, some of which are believed to have already formed planets.formed planets.

High resolution observation is the key to study High resolution observation is the key to study CDs around Herbig Ae stars.CDs around Herbig Ae stars.

Good and important targets for mm- and Good and important targets for mm- and submm-interferometers.submm-interferometers.

Observations of Herbig Observations of Herbig Ae stars using mm-Ae stars using mm-

interferometersinterferometers

1.3 mm dust1.3 mm dust 1212CO 2-1 integratedCO 2-1 integrated 1212CO 2-1 mean velocityCO 2-1 mean velocity

Manning, Koerner, & Sargent 1997, NatureManning, Koerner, & Sargent 1997, Nature

MWC 480MWC 480

Interferometers can help us to understand basic characteristics of circumstellar disks.

What is AB Aur?What is AB Aur? AB Aur is a nearby, bright, single Herbig Ae star.AB Aur is a nearby, bright, single Herbig Ae star.

d ~ 144 pc, Sp = A0 Ve, Md ~ 144 pc, Sp = A0 Ve, M** ~ 2.4 Mo, age ~ 4 Myr ~ 2.4 Mo, age ~ 4 Myr Extended reflection nebulosity in optical.Extended reflection nebulosity in optical.

AB Aur is associated with abundant envelope material.AB Aur is associated with abundant envelope material. 1313CO (1-0) and 2.7 mm continuum images using the CO (1-0) and 2.7 mm continuum images using the

OVRO mm-array (Mannings & Sargent 1997).OVRO mm-array (Mannings & Sargent 1997). A CD around AB Aur was clearly demonstrated.A CD around AB Aur was clearly demonstrated. Detailed structures were not revealed because of a lowDetailed structures were not revealed because of a lowangular resolution (~5”).angular resolution (~5”).

1.6 1.6 m coronagraphic image using the Subaru m coronagraphic image using the Subaru telescope (Fukagawa et al. 2004).telescope (Fukagawa et al. 2004). Spiral arm-like structures in the CD were revealed.Spiral arm-like structures in the CD were revealed.

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Ç™Ç±ÇÃÉsÉNÉ`ÉÉÇ å©ÇÈÇΩÇflÇ…ÇÕïKóvÇ≈Ç∑ÅB

(Fukagawa et al. 2004)(Fukagawa et al. 2004)

AB Aur: AB Aur: 1.6 1.6 m Coronagraphic m Coronagraphic

ImageImage

inner arm

outer arm

branch

dark lane

The CD is detected The CD is detected in scattered light.in scattered light. P.A. = 58° ± 5°, inc. = P.A. = 58° ± 5°, inc. =

30°±5°30°±5° 4 major spiral arms 4 major spiral arms

are identified.are identified. An HST optical image An HST optical image

also shows similar also shows similar structures (Grady et al. structures (Grady et al. 1999).1999).

Weak gravitational Weak gravitational instability would be the instability would be the source of the spiral source of the spiral structures.structures.

What is the actual disk structure?What is the actual disk structure?

SMA Observations of AB SMA Observations of AB AurAur

1212CO (3-2) and 345 GHz dust continuum were CO (3-2) and 345 GHz dust continuum were simultaneously observed using the simultaneously observed using the Submillimeter Array (SMA) in 2003 and 2004.Submillimeter Array (SMA) in 2003 and 2004.

1212CO (3-2) traces warmer, denser gas, while stronger dustCO (3-2) traces warmer, denser gas, while stronger dust

emission at 345 GHz may show more details of the disk structure.emission at 345 GHz may show more details of the disk structure. Compact and extended configurations; three tracksCompact and extended configurations; three tracks Velocity resolution ~0.2 km/sVelocity resolution ~0.2 km/s Total bandwidth: 2 GHz for each side bandTotal bandwidth: 2 GHz for each side band Angular resolution (natural weight): 1.0” x 0.7” (~140 AU x 90 Angular resolution (natural weight): 1.0” x 0.7” (~140 AU x 90

AUAU

AB Aur was also independently observed using AB Aur was also independently observed using the OVRO the OVRO mm-array (Corder et al. 2004), the PdBI (Pietu et mm-array (Corder et al. 2004), the PdBI (Pietu et al.2005), and the NMA (Ohashi, Momose et al.) at al.2005), and the NMA (Ohashi, Momose et al.) at mm-wavelengths.mm-wavelengths.



SMA Results: SMA Results: 345 GHz Dust Continuum345 GHz Dust Continuum

The dust continuum disk The dust continuum disk was clearly resolved at was clearly resolved at ~1” angular resolution .~1” angular resolution .

Two peaks; one at 1” SW Two peaks; one at 1” SW and the other at 1” NE to and the other at 1” NE to the star, but no clear peak the star, but no clear peak at the stellar position.at the stellar position. Size of the ringlike Size of the ringlike

structure ~ 150 AU or less.structure ~ 150 AU or less. There seems to be some There seems to be some

extension to the NE.extension to the NE. Mass ~7.5 MMass ~7.5 MJJ (gas + dust) (gas + dust)

The structure of the dust disk seems to be very different The structure of the dust disk seems to be very different from those of CDs around other Herbig Ae/T Tauri stars.from those of CDs around other Herbig Ae/T Tauri stars.

Comparison of Dust Comparison of Dust Maps at Different Maps at Different

FrequenciesFrequencies

Dust continuum has no peak at the stellar position at all the frequencies.Dust continuum has no peak at the stellar position at all the frequencies. Two peaks (NE and SW to the stellar position) or a ringlike structure is Two peaks (NE and SW to the stellar position) or a ringlike structure is

obvious at 850 micron, while the NE peak is not very clear at lower obvious at 850 micron, while the NE peak is not very clear at lower frequencies.frequencies.



2.1"2.1" 1.6"

NMA 2mmNMA 2mm PdBI 1.4 mmPdBI 1.4 mm

0.85" 0.85" 0.59"0.59"

PdBI 2.8 mmPdBI 2.8 mm

1.4" 1.4" 1.1" 1.1"







SMA 850 SMA 850 mm



1.0" 1.0" 0.72" 0.72"

10

100

1000

1001000

AB Aur dust flux

Flux Density (mJy)

Frequency (GHz)

SMAPdBINMAOVROPdBI

F 2.7

10

100

1000

1001000

AB Aur dust flux

Flux Density (mJy)

Frequency (GHz)

NE

SW

2.8

2.3

SED of AB Aur Dust SED of AB Aur Dust EmissionEmission The SMA The SMA

measurement @ 850 measurement @ 850 m is consistent with m is consistent with others @ mm-others @ mm-wavelengths.wavelengths.

The NE part might The NE part might have a larger spectral have a larger spectral index (larger index (larger ?) than ?) than the SW part?the SW part? Characteristics of dust Characteristics of dust

particles, such as size, particles, such as size, might be different might be different between NE and SW?between NE and SW?



NE halfNE half

SW halfSW half

SMA Results: SMA Results: 1212CO (3-2)CO (3-2) An elongated disk structure, An elongated disk structure,

consistent with other consistent with other observations.observations. Overall dimension: ~530 Overall dimension: ~530 330 330

AUAU Two peaks; one at the stellar Two peaks; one at the stellar

position, and the other at the position, and the other at the most prominent spiral arm.most prominent spiral arm. A part of the 12CO 3-2 A part of the 12CO 3-2

emission seems to trace the emission seems to trace the spiral arm.spiral arm.

PdBI PdBI 1212CO 2-1 map shows only CO 2-1 map shows only one peak at the stellar position.one peak at the stellar position.

Additional extended Additional extended structures.structures.

Structures of the gaseous disk seems to be very different Structures of the gaseous disk seems to be very different from those around other Herbig Ae/T Tauri stars.from those around other Herbig Ae/T Tauri stars.



1212CO 3-2 Channel MapsCO 3-2 Channel Maps







Several channel maps trace the spiral arms seen Several channel maps trace the spiral arms seen in the Subaru image.in the Subaru image.

SMA Results: SMA Results: 1212CO velocity structureCO velocity structure

The velocity structures strongly deviate from The velocity structures strongly deviate from simple Kepler rotation.simple Kepler rotation.

SUMMARYSUMMARY The CD around AB Aur was imaged in The CD around AB Aur was imaged in 1212CO 3-2 and CO 3-2 and

345 GHz continuum using the SMA, revealing details 345 GHz continuum using the SMA, revealing details of structures of the CD.of structures of the CD.

The dust disk was clearly resolved, showing a ring-The dust disk was clearly resolved, showing a ring-like structure around the central star.like structure around the central star. The ring-like structure is most likely due to enhancement of The ring-like structure is most likely due to enhancement of

the disk surface density.the disk surface density. The NE part of the dust disk might have a larger dust The NE part of the dust disk might have a larger dust

spectral index than the SW part.spectral index than the SW part. 1212CO 3-2 emission shows geometrical and kinematical CO 3-2 emission shows geometrical and kinematical

structures, which strongly deviate from simple structures, which strongly deviate from simple Keplerian disks.Keplerian disks. It would be difficult to create such structures by only It would be difficult to create such structures by only

gravitational instability; need simulations with detailed gravitational instability; need simulations with detailed models.models.

13CO (1-0)

AB Aur: 2.7 mm AB Aur: 2.7 mm Continuum and Continuum and 1313CO (1-CO (1-

0) maps0) maps

5.5” x 3.5” beam 5.5” x 3.5” beam unresolved the dust unresolved the dust disk.disk.

The upper limit of the The upper limit of the RRdust diskdust disk ~ 250 AU. ~ 250 AU.

The gas disk was resolvedThe gas disk was resolved RRdiskdisk ~ 390 AU, P.A. ~ 79°, ~ 390 AU, P.A. ~ 79°,

inclination ~ 76°inclination ~ 76° Clear velocity gradient Clear velocity gradient

along the major axis.along the major axis. rotation consistent with rotation consistent with

Kepler motion.Kepler motion.

(Mannings & Sargent 1997)(Mannings & Sargent 1997)

2.7 mm continuum

bluered

sma observations of the herbig ae star ab aur nagayoshi ohashi (asiaa) main collaborators: s.-y. lin...

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