The nature of AFGL 2591 and its associated molecular outflow Infrared and millimeter-wave observations

Lada, Charles J.; Thronson, H. A.; Smith, H. A.; Schwartz, P. R.; Glaccum, W.

doi:10.1086/162599

Cited by 45 publications

(54 citation statements)

References 8 publications

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“…At a distance of 1 kpc and temperatures of 100-300 K, the mass is 0.1-0.3 M , significantly less than the stellar mass of VLA3 (≈10-16 M , Lada et al 1984;van der Tak & Menten 2005). If the distance is 3 kpc, the gas mass is modified to 1-3 M , still less than the scaled stellar mass of >20 M .…”

Section: Estimation Of Densities and Massesmentioning

confidence: 88%

Kinematics of the inner thousand AU region around the young massive star AFGL 2591–VLA3: a massive disk candidate?

Wang

Tak

Hogerheijde

2012

A&A

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Context. Recent detections of disks around young high-mass stars support the idea of massive star formation through accretion rather than coalescence, but the detailed kinematics in the equatorial region of the disk candidates is not well known, which limits our understanding of the accretion process. Aims. This paper explores the kinematics of the gas around a young massive star with millimeter-wave interferometry to improve our understanding of the formation of massive stars though accretion. Methods. We use Plateau de Bure interferometric images to probe the environment of the nearby (∼1 kpc) and luminous (∼20 000 L ) high-mass (10-16 M ) young star AFGL 2591-VLA3 in continuum and in lines of HDO, H 18 2 O and SO 2 in the 115 and 230 GHz bands. Radiative transfer calculations are employed to investigate the kinematics of the source. Results. At ∼0.5 (500 AU) resolution, the line images clearly resolve the velocity field of the central compact source (diameter of ∼800 AU) and show linear velocity gradients in the northeast-southwest direction. Judging from the disk-outflow geometry, the observed velocity gradient results from rotation and radial expansion in the equatorial region of VLA3. Radiative transfer calculations suggest that the velocity field is consistent with sub-Keplerian rotation plus Hubble-law like expansion. The line profiles of the observed molecules suggest a layered structure, with HDO emission arising from the disk mid-plane, H 18 2 O from the warm mid-layer, and SO 2 from the upper disk. Conclusions. We propose AFGL 2591-VLA3 as a new massive disk candidate, with peculiar kinematics. The rotation of this disk is sub-Keplerian, probably due to magnetic braking, while the stellar wind may be responsible for the expansion of the disk. The expansion motion may also be an indirect evidence of disk accretion in the very inner region because of the conservation of angular momentum. The sub-Keplerian rotation discovered in our work suggests that AFGL 2591-VLA3 may be a special case linking transition of velocity field of massive disks from pure Keplerian rotation to solid-body rotation though definitely more new detections of circumstellar disks around high-mass YSOs are required to examine this hypothesis. Our results support the idea that early B-type stars could be formed with a circumstellar disk from the point of view of the disk-outflow geometry, though the accretion processes in the disk need to be further investigated.

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Section: Estimation Of Densities and Massesmentioning

confidence: 88%

Kinematics of the inner thousand AU region around the young massive star AFGL 2591–VLA3: a massive disk candidate?

Wang

Tak

Hogerheijde

2012

A&A

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“…These are coincident with an east-west bipolar outflow (e.g. Lada et al 1984;Hasegawa & Mitchell 1995), which extends across 5 or 4.8 pc at 3.33 kpc, but also contains a more collimated central small-scale component with an extent of 90 × 20 .…”

Section: Introductionmentioning

confidence: 84%

“…AFGL 2591 is a well-studied example of a luminous starforming region (2.1−2.5 × 10 5 L at 3.33 kpc, Lada et al 1984;Henning et al 1990;Rygl et al 2012). One of its most prominent features is a one sided conical reflection nebula observed in the near-IR (e.g Minchin et al 1991;Tamura & Yamashita 1992).…”

Section: Introductionmentioning

confidence: 99%

The standard model of low-mass star formation applied to massive stars: a multi-wavelength picture of AFGL 2591

Johnston

Shepherd

Robitaille

et al. 2013

A&A

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Context. While it is currently unclear from a theoretical standpoint which forces and processes dominate the formation of high-mass stars, and hence determine the mode in which they form, much of the recent observational evidence suggests that massive stars are born in a similar manner to their low-mass counterparts. Aims. This paper aims to investigate the hypothesis that the embedded luminous star AFGL 2591-VLA 3 (2.3 × 10 5 L at 3.33 kpc) is forming according to a scaled-up version of a low-mass star formation scenario. Methods. We present multi-configuration Very Large Array (VLA) 3.6 cm and 7 mm, as well as Combined Array for Research in Millimeter Astronomy C 18 O and 3 mm continuum observations to investigate the morphology and kinematics of the ionized gas, dust, and molecular gas around AFGL 2591. We also compare our results to ancillary Gemini North near-IR images, and model the near-IR to sub-mm spectral energy distribution (SED) and Two Micron All Sky Survey (2MASS) image profiles of AFGL 2591 using a Monte-Carlo dust continuum radiative transfer code. Results. The observed 3.6 cm images uncover for the first time that the central powering source AFGL 2591-VLA 3 has a compact core plus collimated jet morphology, extending 4000 AU eastward from the central source with an opening angle of <10• at this radius. However, at 7 mm VLA 3 does not show a jet morphology, but instead compact (<500 AU) emission, some of which (<0.57 mJy of 2.9 mJy) is estimated to be from dust emission. The spectral index of AFGL 2591-VLA 3 between 3.6 cm and 7 mm was found to be between 0.4 and 0.5, similar to that of an ionized wind. If the 3.6 cm emission is modelled as an ionized jet, the jet has almost enough momentum to drive the larger-scale flow. However, assuming a shock efficiency of 10%, the momentum rate of the jet is not sufficient to ionize itself via only shocks, and thus a significant portion of the emission is instead likely created in a photoionized wind. The C 18 O emission uncovers dense entrained material in the outflow(s) from these young stars. The main features of the SED and 2MASS images of AFGL 2591-VLA 3 are also reproduced by our model dust geometry of a rotationally flattened envelope with and without a disk. Conclusions. The above results are consistent with a picture of massive star formation similar to that seen for low-mass protostars. However, within its envelope, AFGL 2591-VLA 3 contains at least four other young stars, constituting a small cluster. Therefore it appears that AFGL 2591-VLA 3 may be able to source its accreting material from a shared gas reservoir while still exhibiting the phenomena expected during the formation of low-mass stars.

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“…The object emits most of its energy in the infrared, owing to re-radiation of optical/UV radiation from the central object by the surrounding gas and dust. It has a bolometric luminosity of ∼2 × 10 4 L (at 1 kpc) and exhibits powerful large (>1 ) bipolar molecular outflows (Lada et al 1984;Hasegawa & Mitchell 1995).…”

Section: Introductionmentioning

confidence: 99%

The JCMT Spectral Legacy Survey: physical structure of the molecular envelope of the high-mass protostar AFGL2591

Wiel

Tak

Spaans

et al. 2011

A&A

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Context. The understanding of the formation process of massive stars ( > ∼ 8 M ) is limited by a combination of theoretical complications and observational challenges. The high UV luminosities of massive stars give rise to chemical complexity in their natal molecular clouds and affect the dynamical properties of their circumstellar envelopes. Aims. We investigate the physical structure of the large-scale (∼10 4 -10 5 AU) molecular envelope of the high-mass protostar AFGL2591. Methods. Observational constraints are provided by spectral imaging in the 330-373 GHz regime from the JCMT Spectral Legacy Survey and its high-frequency extension. While the majority of the ∼160 spectral features from the survey cube are spatially unresolved, this paper uses the 35 that are significantly extended in the spatial directions. For these features we present integrated intensity maps and velocity maps. The observed spatial distributions of a selection of six species are compared with radiative transfer models based on (i) a static spherically symmetric structure; (ii) a dynamic spherical structure; and (iii) a static flattened structure. Results. The maps of CO and its isotopic variations exhibit elongated geometries on scales of ∼100 , and smaller scale substructure is found in maps of N 2 H + , o-H 2 CO, CS, SO 2 , C 2 H, and various CH 3 OH lines. In addition, a line-of-sight velocity gradient is apparent in maps of all molecular lines presented here, except SO, SO 2 , and H 2 CO. We find two emission peaks in warm (E up ∼ 200 K) CH 3 OH separated by 12 (12 000 AU), indicative of a secondary heating source in the envelope. The spherical models are able to explain the distribution of emission for the optically thin H 13 CO + and C 34 S, but not for the optically thick HCN, HCO + , and CS or for the optically thin C 17 O. The introduction of velocity structure mitigates the optical depth effects, but does not fully explain the observations, especially in the spectral dimension. A static flattened envelope viewed at a small inclination angle does slightly better. Conclusions. Based on radiative transfer modeling, we conclude that a geometry of the envelope other than an isotropic static sphere is needed to circumvent line optical depth effects. We propose that this could be achieved in circumstellar envelope models with an outflow cavity and/or an inhomogeneous structure on scales 10 4 AU. The picture of inhomogeneity is supported by substructure observed in at least six different species.

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The nature of AFGL 2591 and its associated molecular outflow Infrared and millimeter-wave observations

Abstract: The resul ts of infrared photometry from 2 llm-160 llm of AFGL 2591 and 12CO observations of• its associated molecular cloud and high velocity mol ecul ar outflow are presented and di scussed. Observations between 60 llm and 160 llm provide the first detailed far-infrared

Cited by 45 publications

References 8 publications

Kinematics of the inner thousand AU region around the young massive star AFGL 2591–VLA3: a massive disk candidate?

Kinematics of the inner thousand AU region around the young massive star AFGL 2591–VLA3: a massive disk candidate?

The standard model of low-mass star formation applied to massive stars: a multi-wavelength picture of AFGL 2591

The JCMT Spectral Legacy Survey: physical structure of the molecular envelope of the high-mass protostar AFGL2591

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