Observations of Water Masers and Radio Continuum Emission in AFGL 2591

Trinidad, M. A.; Curiel, S.; Cantó, J.; D’Alessio, Paola; Rodrı́guez, Luis F.; Torrelles, J. M.; Gómez, José F.; Patel, Nimesh; Ho, Paul T. P.

doi:10.1086/374618

Cited by 62 publications

(130 citation statements)

References 41 publications

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“…In addition, a new, low surface brightness source was detected: VLA 5, which varies in peak flux from 3−5 σ across the extent of the source. With the addition of shorter baselines, more extended emission is recovered compared to the 3.6 cm A array images of Tofani et al (1995) and Trinidad et al (2003). Most noticeably, the emission from source VLA 3, which is coincident with the position of the central source in the near-IR images, is better-determined; a close-up of the emission from this source is shown in panel b) A43, page 10 of 23 of Fig.…”

Section: Results Of Sed and Image Modellingmentioning

confidence: 68%

“…This gradient was also found in the SMA observations of Jiménez-Serra et al (2012), which they found to be consistent with Keplerian-like rotation around a 40 M star. Finally, both OH and water masers have been observed towards VLA 3 (Trinidad et al 2003;Hutawarakorn & Cohen 2005;Sanna et al 2012). The Very Large Array (VLA) 1 22 GHz water maser observations of Trinidad et al (2003) uncovered a maser cluster, which included a ∼0.01 diameter shell-like structure on the smallest scales.…”

Section: Introductionmentioning

confidence: 96%

“…Finally, both OH and water masers have been observed towards VLA 3 (Trinidad et al 2003;Hutawarakorn & Cohen 2005;Sanna et al 2012). The Very Large Array (VLA) 1 22 GHz water maser observations of Trinidad et al (2003) uncovered a maser cluster, which included a ∼0.01 diameter shell-like structure on the smallest scales. As well as finding largely consistent results, the Very Long Baseline Array 22 GHz water maser observations of Sanna et al (2012) determined that the maser cluster is arranged in a v-shape, which coincides with the expected location of the outflow walls apparent in the near-IR reflection nebula.…”

Section: Introductionmentioning

confidence: 96%

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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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Section: Results Of Sed and Image Modellingmentioning

confidence: 68%

Section: Introductionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 96%

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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

View full text Add to dashboard Cite

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“…The yellow star marks the position of the central heating source (infrared source from Van der Tak et al 1999). VLA1 and VLA2 are radio continuum sources detected by Trinidad et al (2003). The near-IR loops from Preibisch et al (2003) are indicated in dashed yellow.…”

Section: Further Evidence Of Substructurementioning

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 high intrinsic brightness of maser emission makes it useful as a signpost of dense gas and for kinematic studies of protostellar environments (e.g., Trinidad et al 2003;Sanna et al 2012a). With VLBI techniques, the proper motions and parallaxes of H 2 O masers can be measured to micro-arcsecond accuracy, leading to accurate distance estimates for star-forming regions as distant as ∼10 kpc (Sanna et al 2012b) and a revised picture of Galactic structure .…”

Section: Introductionmentioning

confidence: 99%

Water in star-forming regions withHerschel(WISH)

Tak

Chavarría

Herpin

et al. 2013

A&A

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Context. Water is a key constituent of star-forming matter, but the origin of its line emission and absorption during high-mass star formation is not well understood. Aims. We study the velocity profiles of low-excitation H 2 O lines toward 19 high-mass star-forming regions and search for trends with luminosity, mass, and evolutionary stage. Methods. We decompose high-resolution Herschel-HIFI line spectra near 990, 1110 and 1670 GHz into three distinct physical components. Dense cores (protostellar envelopes) are usually seen as narrow absorptions in the H 2 O 1113 and 1669 GHz ground-state lines, the H 2 O 987 GHz excited-state line, and the H 18 2 O 1102 GHz ground-state line. In a few sources, the envelopes appear in emission in some or all studied lines, indicating higher temperatures or densities. Broader features due to outflows are usually seen in absorption in the H 2 O 1113 and 1669 GHz lines, in 987 GHz emission, and not seen in H 18 2 O, indicating a lower column density and a higher excitation temperature than the envelope component. A few outflows are detected in H 18 2 O, indicating higher column densities of shocked gas. In addition, the H 2 O 1113 and 1669 GHz spectra show narrow absorptions by foreground clouds along the line of sight. The lack of corresponding features in the 987 GHz and H 18 2 O lines indicates a low column density and a low excitation temperature for these clouds, although their derived H 2 O ortho/para ratios are close to 3. Results. The intensity of the ground state lines of H 2 O at 1113 and 1669 GHz does not show significant trends with source luminosity, envelope mass, or evolutionary state. In contrast, the flux in the excited-state 987 GHz line appears correlated with luminosity and the H 18 2 O line flux appears correlated with the envelope mass. Furthermore, appearance of the envelope in absorption in the 987 GHz and H 18 2 O lines seems to be a sign of an early evolutionary stage, as probed by the mid-infrared brightness and the L bol /M env ratio of the source. Conclusions. The ground state transitions of H 2 O trace the outer parts of the envelopes, so that the effects of star formation are mostly noticeable in the outflow wings. These lines are heavily affected by absorption, so that line ratios of H 2 O involving the ground states must be treated with caution, especially if multiple clouds are superposed as in the extragalactic case. The isotopic H 182 O line appears to trace the mass of the protostellar envelope, indicating that the average H 2 O abundance in high-mass protostellar envelopes does not change much with time. The excited state line at 987 GHz increases in flux with luminosity and appears to be a good tracer of the mean weighted dust temperature of the source, which may explain why it is readily seen in distant galaxies.

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Observations of Water Masers and Radio Continuum Emission in AFGL 2591

Cited by 62 publications

References 41 publications

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

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

Water in star-forming regions withHerschel(WISH)

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