OH maser towards IRAS 06056+2131: polarization parameters and evolution status

ABSTRACT We present high-angular resolution observations of OH maser emission towards the high-mass star-forming region IRAS 06056+2131. The observations were carried out using the UK radio interferometer array, Multi-Element Radio Linked Interferometer Network (MERLIN) in the OH main lines at 1665 and 1667 MHz, in addition to the OH satellite line at 1720 MHz. The results of this study reveal the small upper limit to the size of emission in the 1665-MHz line with an estimated total intensity of ∼4 Jy. We did not detect any emission from the 1667 and 1720-MHz lines. The full polarization mode of MERLIN enables us to investigate the magnetic field in the OH maser region. In this transition, a Zeeman pair is identified from which a magnetic strength of ∼−1.5 mG is inferred. Our results show that IRAS 06056+2131 is highly polarized, with ∼ 96 ${{\ \rm per\ cent}}$ circular polarization and ∼6 ${{\ \rm per\ cent}}$ linear polarization. The linear polarization angle is ∼29°, implying a magnetic field which could be aligned with the outflow direction detected towards this region, but the actual magnetic field direction has an uncertainty of up to 110° due to the possible effects of Faraday rotation. The star-forming evolutionary status of the embedded protostellar object is discussed.

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Outflows, cores, and magnetic field orientations in W43-MM1 as seen by ALMA

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038024 ◽

2020 ◽

Vol 640 ◽

pp. A111

Author(s):

C. Arce-Tord ◽

F. Louvet ◽

P. C. Cortes ◽

F. Motte ◽

C. L. H. Hull ◽

...

Keyword(s):

Magnetic Field ◽

High Mass ◽

Continuum Emission ◽

High Angular Resolution ◽

Mass Star ◽

Star Forming ◽

The Core ◽

Dense Cores ◽

The Impact ◽

The Magnetic Field

Aims. It has been proposed that the magnetic field, which is pervasive in the interstellar medium, plays an important role in the process of massive star formation. To better understand the impact of the magnetic field at the pre- and protostellar stages, high-angular resolution observations of polarized dust emission toward a large sample of massive dense cores are needed. We aim to reveal any correlation between the magnetic field orientation and the orientation of the cores and outflows in a sample of protostellar dense cores in the W43-MM1 high-mass star-forming region. Methods. We used the Atacama Large Millimeter Array in Band 6 (1.3 mm) in full polarization mode to map the polarized emission from dust grains at a physical scale of ~2700 au. We used these data to measure the orientation of the magnetic field at the core scale. Then, we examined the relative orientations of the core-scale magnetic field, of the protostellar outflows, and of the major axis of the dense cores determined from a 2D Gaussian fit in the continuum emission. Results. We find that the orientation of the dense cores is not random with respect to the magnetic field. Instead, the dense cores are compatible with being oriented 20–50° with respect to the magnetic field. As for the outflows, they could be oriented 50–70° with respect to the magnetic field, or randomly oriented with respect to the magnetic field, which is similar to current results in low-mass star-forming regions. Conclusions. The observed alignment of the position angle of the cores with respect to the magnetic field lines shows that the magnetic field is well coupled with the dense material; however, the 20–50° preferential orientation contradicts the predictions of the magnetically-controlled core-collapse models. The potential correlation of the outflow directions with respect to the magnetic field suggests that, in some cases, the magnetic field is strong enough to control the angular momentum distribution from the core scale down to the inner part of the circumstellar disks where outflows are triggered.

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ALMA resolves the hourglass magnetic field in G31.41+0.31

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935701 ◽

2019 ◽

Vol 630 ◽

pp. A54 ◽

Cited By ~ 8

Author(s):

M. T. Beltrán ◽

M. Padovani ◽

J. M. Girart ◽

D. Galli ◽

R. Cesaroni ◽

...

Keyword(s):

Magnetic Field ◽

Velocity Gradient ◽

Flux Ratio ◽

High Mass ◽

Continuum Emission ◽

Mass Star ◽

Star Forming ◽

The Core ◽

Molecular Core ◽

The Magnetic Field

Context. Submillimeter Array (SMA) 870 μm polarization observations of the hot molecular core G31.41+0.31 revealed one of the clearest examples up to date of an hourglass-shaped magnetic field morphology in a high-mass star-forming region. Aims. To better establish the role that the magnetic field plays in the collapse of G31.41+0.31, we carried out Atacama Large Millimeter/ submillimeter Array (ALMA) observations of the polarized dust continuum emission at 1.3 mm with an angular resolution four times higher than that of the previous (sub)millimeter observations to achieve an unprecedented image of the magnetic field morphology. Methods. We used ALMA to perform full polarization observations at 233 GHz (Band 6). The resulting synthesized beam is 0′′.28×0′′.20 which, at the distance of the source, corresponds to a spatial resolution of ~875 au. Results. The observations resolve the structure of the magnetic field in G31.41+0.31 and allow us to study the field in detail. The polarized emission in the Main core of G31.41+0.41is successfully fit with a semi-analytical magnetostatic model of a toroid supported by magnetic fields. The best fit model suggests that the magnetic field is well represented by a poloidal field with a possible contribution of a toroidal component of ~10% of the poloidal component, oriented southeast to northwest at approximately −44° and with an inclination of approximately −45°. The magnetic field is oriented perpendicular to the northeast to southwest velocity gradient detected in this core on scales from 103 to 104 au. This supports the hypothesis that the velocity gradient is due to rotation of the core and suggests that such a rotation has little effect on the magnetic field. The strength of the magnetic field estimated in the central region of the core with the Davis–Chandrasekhar-Fermi method is ~8–13 mG and implies that the mass-to-flux ratio in this region is slightly supercritical. Conclusions. The magnetic field in G31.41+0.31 maintains an hourglass-shaped morphology down to scales of <1000 au. Despite the magnetic field being important in G31.41+0.31, it is not enough to prevent fragmentation and collapse of the core, as demonstrated by the presence of at least four sources embedded in the center of the core.

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High-Mass Star and Massive Cluster Formation in the Milky Way

Annual Review of Astronomy and Astrophysics ◽

10.1146/annurev-astro-091916-055235 ◽

2018 ◽

Vol 56 (1) ◽

pp. 41-82 ◽

Cited By ~ 89

Author(s):

Frédérique Motte ◽

Sylvain Bontemps ◽

Fabien Louvet

Keyword(s):

Star Formation ◽

Milky Way ◽

Galactic Plane ◽

Cluster Formation ◽

Theoretical Models ◽

High Mass ◽

High Angular Resolution ◽

Mass Star ◽

Star Forming ◽

Massive Cluster

This review examines the state-of-the-art knowledge of high-mass star and massive cluster formation, gained from ambitious observational surveys, which acknowledges the multiscale characteristics of these processes. After a brief overview of theoretical models and main open issues, we present observational searches for the evolutionary phases of high-mass star formation, first among high-luminosity sources and more recently among young massive protostars and the elusive high-mass prestellar cores. We then introduce the most likely evolutionary scenario for high-mass star formation, which emphasizes the link of high-mass star formation to massive cloud and cluster formation. Finally, we introduce the first attempts to search for variations of the star-formation activity and cluster formation in molecular cloud complexes in the most extreme star-forming sites and across the Milky Way. The combination of Galactic plane surveys and high–angular resolution images with submillimeter facilities such as Atacama Large Millimeter Array (ALMA) are prerequisites to make significant progress in the forthcoming decade.

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High resolution magnetic field measurements in high-mass star-forming regions using masers

10.22323/1.178.0034 ◽

2016 ◽

Author(s):

Gabriele Surcis ◽

Wouter H.T. Vlemmings ◽

Huib Jan van Langevelde ◽

Busaba Hutawarakorn Kramer

Keyword(s):

Magnetic Field ◽

High Resolution ◽

Field Measurements ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions ◽

Magnetic Field Measurements

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Polarization Properties and Magnetic Field Structures in the High-mass Star-forming Region W51 Observed with ALMA

The Astrophysical Journal ◽

10.3847/1538-4357/aaa4c1 ◽

2018 ◽

Vol 855 (1) ◽

pp. 39 ◽

Cited By ~ 20

Author(s):

Patrick M. Koch ◽

Ya-Wen Tang ◽

Paul T. P. Ho ◽

Hsi-Wei Yen ◽

Yu-Nung Su ◽

...

Keyword(s):

Magnetic Field ◽

High Mass ◽

Mass Star ◽

Star Forming

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ALMA reveals the magnetic field evolution in the high-mass star forming complex G9.62+0.19

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834100 ◽

2019 ◽

Vol 626 ◽

pp. A36 ◽

Cited By ~ 6

Author(s):

D. Dall’Olio ◽

W. H. T. Vlemmings ◽

M. V. Persson ◽

F. O. Alves ◽

H. Beuther ◽

...

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

High Mass ◽

Mass Star ◽

Evolutionary Sequence ◽

Star Forming ◽

High Magnetic Field Strength ◽

The Magnetic Field ◽

Linear Polarisation

Context. The role of magnetic fields during the formation of high-mass stars is not yet fully understood, and the processes related to the early fragmentation and collapse are as yet largely unexplored. The high-mass star forming region G9.62+0.19 is a well known source, presenting several cores at different evolutionary stages. Aims. We seek to investigate the magnetic field properties at the initial stages of massive star formation. We aim to determine the magnetic field morphology and strength in the high-mass star forming region G9.62+0.19 to investigate its relation to the evolutionary sequence of the cores. Methods. We made use of Atacama Large Millimeter Array (ALMA) observations in full polarisation mode at 1 mm wavelength (Band 7) and we analysed the polarised dust emission. We estimated the magnetic field strength via the Davis–Chandrasekhar–Fermi and structure function methods. Results. We resolve several protostellar cores embedded in a bright and dusty filamentary structure. The polarised emission is clearly detected in six regions: two in the northern field and four in the southern field. Moreover the magnetic field is orientated along the filament and appears perpendicular to the direction of the outflows. The polarisation vectors present ordered patterns and the cores showing polarised emission are less fragmented. We suggest an evolutionary sequence of the magnetic field, and the less evolved hot core exhibits a stronger magnetic field than the more evolved hot core. An average magnetic field strength of the order of 11 mG was derived, from which we obtain a low turbulent-to-magnetic energy ratio, indicating that turbulence does not significantly contribute to the stability of the clump. We report a detection of linear polarisation from thermal line emission, probably from methanol or carbon dioxide, and we tentatively compared linear polarisation vectors from our observations with previous linearly polarised OH masers observations. We also compute the spectral index, column density, and mass for some of the cores. Conclusions. The high magnetic field strength and smooth polarised emission indicate that the magnetic field could play an important role in the fragmentation and the collapse process in the star forming region G9.62+019 and that the evolution of the cores can be magnetically regulated. One core shows a very peculiar pattern in the polarisation vectors, which can indicate a compressed magnetic field. On average, the magnetic field derived by the linear polarised emission from dust, thermal lines, and masers is pointing in the same direction and has consistent strength.

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Methanol and water maser observations separate disc and outflow sources in IRAS 19410+2336

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa574 ◽

2020 ◽

Vol 493 (3) ◽

pp. 4442-4452 ◽

Cited By ~ 1

Author(s):

M S Darwish ◽

K A Edris ◽

A M S Richards ◽

S Etoka ◽

M S Saad ◽

...

Keyword(s):

Flux Density ◽

High Mass ◽

High Angular Resolution ◽

Mass Star ◽

Star Forming ◽

Peak Flux ◽

Maser Line ◽

Methanol Masers ◽

Water Masers ◽

Water Maser

ABSTRACT We investigate the kinematics of high-mass protostellar objects within the high-mass star-forming region IRAS 19410+2336. We performed high angular resolution observations of 6.7-GHz methanol and 22 GHz water masers using the Multi-Element Radio Linked Interferometer Network (MERLIN) and e-MERLIN interferometers. The 6.7-GHz methanol maser emission line was detected within the ∼16–27 km s−1 velocity range with a peak flux density ∼50 Jy. The maser spots are spread over ∼1.3 arcsec on the sky, corresponding to ∼2800 au at a distance of 2.16 kpc. These are the first astrometric measurements at 6.7 GHz in IRAS 19410+2336. The 22-GHz water maser line was imaged in 2005 and 2019 (the latter with good astrometry). Its velocities range from 13 to ∼29 km s−1. The peak flux density was found to be 18.7 and 13.487 Jy in 2005 and 2019, respectively. The distribution of the water maser components is up to 165 mas, ∼350 au at 2.16 kpc. We find that the Eastern methanol masers most probably trace outflows from the region of millimetre source mm1. The water masers to the West lie in a disc (flared or interacting with outflow/infall) around another more evolved millimetre source (13-s). The maser distribution suggests that the disc lies at an angle of 60° or more to the plane of the sky and the observed line-of-sight velocities then suggest an enclosed mass between 44 M⊙ and as little as 11 M⊙ if the disc is edge-on. The Western methanol masers may be infalling.

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Magnetic massive stars in star forming regions

Proceedings of the International Astronomical Union ◽

10.1017/s174392131900382x ◽

2018 ◽

Vol 14 (A30) ◽

pp. 132-132

Author(s):

Swetlana Hubrig ◽

Markus Schöller ◽

Silva P. Järvinen

Keyword(s):

Magnetic Field ◽

Star Formation ◽

Magnetic Fields ◽

Active Sites ◽

Massive Stars ◽

High Mass ◽

Mass Star ◽

Star Forming ◽

Star Forming Regions ◽

Gas Cloud

AbstractOne idea for the origin of magnetic fields in massive stars suggests that the magnetic field is the fossil remnant of the Galactic ISM magnetic field, amplified during the collapse of the magnetised gas cloud. A search for the presence of magnetic fields in massive stars located in active sites of star formation led to the detection of rather strong magnetic fields in a few young stars. Future spectropolarimetric observations are urgently needed to obtain insights into the mechanisms that drive the generation of kG magnetic fields during high-mass star formation.

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Magnetic Fields in Massive Star-forming Regions (MagMaR). II. Tomography through Dust and Molecular Line Polarization in NGC 6334I(N)

The Astrophysical Journal ◽

10.3847/1538-4357/ac28a1 ◽

2021 ◽

Vol 923 (2) ◽

pp. 204

Author(s):

Paulo C. Cortés ◽

Patricio Sanhueza ◽

Martin Houde ◽

Sergio Martín ◽

Charles L. H. Hull ◽

...

Keyword(s):

Magnetic Field ◽

Dust Emission ◽

High Mass ◽

Dispersion Function ◽

Mass Star ◽

Length Scales ◽

Star Forming ◽

Multiple Length Scales ◽

Polarized Emission ◽

The Magnetic Field

Abstract Here, we report ALMA detections of polarized emission from dust, CS(J = 5 → 4), and C33S(J = 5 → 4) toward the high-mass star-forming region NGC 6334I(N). A clear “hourglass” magnetic field morphology was inferred from the polarized dust emission, which is also directly seen from the polarized CS emission across velocity, where the polarization appears to be parallel to the field. By considering previous findings, the field retains a pinched shape that can be traced to clump length scales from the envelope scales traced by ALMA, suggesting that the field is dynamically important across multiple length scales in this region. The CS total intensity emission is found to be optically thick (τ CS = 32 ± 12) while the C33S emission appears to be optically thin ( τ C 33 S = 0.1 ± 0.01 ). This suggests that sources of anisotropy other than large velocity gradients, i.e., anisotropies in the radiation field, are required to explain the polarized emission from CS seen by ALMA. By using four variants of the Davis–Chandrasekhar–Fermi technique and the angle dispersion function methods (ADF), we obtain an average of the estimates for the magnetic field strength on the plane of the sky of B pos = 16 mG from the dust and B pos ∼ 2 mG from the CS emission, where each emission traces different molecular hydrogen number densities. This effectively enables a tomographic view of the magnetic field within a single ALMA observation.

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Molecular complexity in the interstellar medium

Proceedings of the International Astronomical Union ◽

10.1017/s1743921319006380 ◽

2019 ◽

Vol 15 (S350) ◽

pp. 96-99

Author(s):

Arnaud Belloche

Keyword(s):

Interstellar Medium ◽

High Mass ◽

High Angular Resolution ◽

Mass Star ◽

Star Forming ◽

Rotational Spectra ◽

Increased Sensitivity ◽

Molecular Complexity ◽

Complex Organic ◽

Made In

AbstractThe search for complex organic molecules in the interstellar medium (ISM) has revealed species of ever greater complexity. This search relies on the progress made in the laboratory to characterize their rotational spectra. Our understanding of the processes that lead to molecular complexity in the ISM builds on numerical simulations that use chemical networks fed by laboratory and theoretical studies. The advent of ALMA and NOEMA has opened a new door to explore molecular complexity in the ISM. Their high angular resolution reduces the spectral confusion of star-forming cores and their increased sensitivity allows the detection of low-abundance molecules that could not be probed before. The complexity of the recently-detected molecules manifests itself not only in terms of number of atoms but also in their molecular structure. We discuss these developments and report on ReMoCA, a new spectral line survey performed with ALMA toward the high-mass star-forming region Sgr B2(N).

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