Three-dimensional dust density structure of the Orion, Cygnus X, Taurus, and Perseus star-forming regions

Magnetic fields play a major role in the general dynamics of astronomical phenomena and particularly in the process of star formation. The magnetic field strength in galactic molecular clouds is of the order of few tens of μG. On a smaller scale, OH masers exhibit fields of the order of mG and these can probably be taken as representative of the magnetic field in the dense regions surrounding protostars. The OH molecule has been shown to emit highly circular and linearly polarized radiation. That it was indeed the action of the magnetic field that would give rise to the highly polarized spectrum of OH has been shown by the VLBI observations of Zeeman pairs of the 1720 and 6035 MHz by Lo et. al. and Moran et. al. VLBI observations of W3 (OH) revealed that the OH emission was coming from numerous discrete locations and that all spots fell within the continuum contours of the compact HII region. The most detailed VLBI aperture synthesis experiment of the 1665 MHz emission from W3 (OH) was carried out by Reid et. al. who found several Zeeman pairs and a characteristic maser clump size of 30 mas. In this work, we report the results of a 5 station VLBI aperture synthesis experiment of the 1665 MHz OH emission from W3 (OH) with full polarization information. We produced VLBI synthesis maps of all Stokes parameters of 16 spectral features that showed elliptical polarization. The magnitude and direction of the magnetic field have been obtained by the detection of 7 Zeeman pairs. The three dimensional orientation of the magnetic field can be obtained, following the theoretical arguments of Goldreich et. al., from the observation of π and σ components.

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Astrometry of Galactic Star-Forming Regions ON1 and ON2N with VERA

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312007351 ◽

2012 ◽

Vol 8 (S287) ◽

pp. 391-395 ◽

Cited By ~ 1

Author(s):

Takumi Nagayama ◽

Keyword(s):

Three Dimensional ◽

Rotation Velocity ◽

Galactic Rotation ◽

The Sun ◽

Angular Rotation ◽

Star Forming ◽

Star Forming Regions ◽

Circular Rotation

AbstractWe conducted the astrometry of H2O masers in the Galactic star-forming regions ON1 and ON2N with the VLBI Exploration of Radio Astrometry (VERA). The measured distances to ON1 and ON2N are 2.47±0.11 kpc and 3.83±0.13 kpc, respectively. In the case that ON1 and ON2N are on a perfect circular rotation, we estimate the angular rotation velocity of the Galactic rotation at the Sun (the ratio of the Galactic constants) to be 28 ± 2 km s−1 kpc−1 using the measured distances and three-dimensional velocity components of ON1 and ON2N. This value is larger than the IAU recommended value of 25.9 km s−1 kpc−1, but consistent with other results recently obtained with the VLBI technique.

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Searching for intergalactic star forming regions in Stephan’s Quintet with SITELLE

Astronomy and Astrophysics ◽

10.1051/0004-6361/201935686 ◽

2019 ◽

Vol 629 ◽

pp. A102 ◽

Cited By ~ 1

Author(s):

S. Duarte Puertas ◽

J. Iglesias-Páramo ◽

J. M. Vilchez ◽

L. Drissen ◽

C. Kehrig ◽

...

Keyword(s):

Large Scale ◽

Dwarf Galaxy ◽

Three Dimensional ◽

Large Field ◽

North West ◽

Star Forming ◽

Spatially Resolved ◽

Star Forming Regions ◽

The North ◽

Spectral Ranges

Stephan’s Quintet (SQ), the prototypical compact group of galaxies in the local Universe, has been observed with the imaging Fourier transform spectrometer SITELLE, attached to the Canada-France-Hawaii-Telescope, to perform a deep search for intergalactic star-forming emission. In this paper we present the extended ionised gaseous structures detected and analyse their kinematical properties. The large field of view (11′ × 11′) and the spectral ranges of SITELLE have allowed a thorough study of the entire galaxy system, its interaction history and the main properties of the ionised gas. The observations have revealed complex three-dimensional strands in SQ seen for the first time, as well as the spatially resolved velocity field for a new SQ dwarf galaxy (M 82-like) and the detailed spectral map of NGC 7320c, confirming its AGN nature. A total of 175 SQ Hα emission regions have been found, 22 of which present line profiles with at least two kinematical components. We studied 12 zones and 28 sub-zones in the SQ system in order to define plausible physical spatial connections between its different parts in the light of the kinematical information gathered. In this respect we have found five velocity systems in SQ: (i) v = [5600−5900] km s−1 associated with the new intruder and the southern debris region; (ii) v = [5900−6100] km s−1, associated with the north starburst A and south starburst A and the strands connected to these zones; (iii) v = [6100−6600] km s−1, associated with the strands from the large-scale shock region (LSSR); (iv) v = [6600−6800] km s−1, associated with the young tidal tail, the starburst A (SQA), NGC 7319, and the NGC 7319 north lobe; and (v) v = [6800−7000] km s−1, associated with the strands seen connecting LSSR with SQA. We fail to detect ionised gas emission in the old tail, neither in the vicinity of NGC 7318A nor in NGC 7317, and the connection between NGC 7319 north lobe and SQA cannot be confirmed. Conversely, a clear gaseous bridge has been confirmed both spatially and kinematically between the LSSR zone and the NGC 7319 AGN nucleus. Finally, a larger scale, outer rim winding the NGC 7318B/A system clockwise north-west to south-east has been highlighted in continuum and in Hα. This structure may be reminiscent of a sequence of a previously proposed scenario for SQ a sequence of individual interactions.

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3D mapping of young stars in the solar neighbourhood with Gaia DR2

Astronomy and Astrophysics ◽

10.1051/0004-6361/201834150 ◽

2018 ◽

Vol 620 ◽

pp. A172 ◽

Cited By ~ 33

Author(s):

E. Zari ◽

H. Hashemi ◽

A. G. A. Brown ◽

K. Jardine ◽

P. T. de Zeeuw

Keyword(s):

Main Sequence ◽

Three Dimensional ◽

Young Stars ◽

Solar Neighbourhood ◽

Mass Star ◽

Early Type ◽

Star Forming ◽

Star Forming Regions ◽

Density Maps ◽

Early Type Stars

We study the three dimensional arrangement of young stars in the solar neighbourhood using the second release of the Gaia mission (Gaia DR2) and we provide a new, original view of the spatial configuration of the star-forming regions within 500 pc of the Sun. By smoothing the star distribution through a Gaussian filter, we construct three dimensional (3D) density maps for early-type stars (upper-main sequence, UMS) and pre-main sequence (PMS) sources. The PMS and the UMS samples are selected through a combination of photometric and astrometric criteria. A side product of the analysis is a 3D, G-band extinction map, which we use to correct our colour-magnitude diagram for extinction and reddening. Both density maps show three prominent structures, Scorpius-Centaurus, Orion, and Vela. The PMS map shows a plethora of lower-mass star-forming regions, such as Taurus, Perseus, Cepheus, Cassiopeia, and Lacerta, which are less visible in the UMS map due to the lack of large numbers of bright, early-type stars. We report the finding of a candidate new open cluster towards l, b ∼ 218.5° , − 2°, which could be related to the Orion star-forming complex. We estimate ages for the PMS sample and we study the distribution of PMS stars as a function of their age. We find that younger stars cluster in dense, compact clumps, and are surrounded by older sources, whose distribution is instead more diffuse. The youngest groups that we find are mainly located in Scorpius-Centaurus, Orion, Vela, and Taurus. Cepheus, Cassiopeia, and Lacerta are instead more evolved and less numerous. Finally, we find that the 3D density maps show no evidence for the existence of the ring-like structure which is usually referred to as the Gould Belt.

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VLBA DETERMINATION OF THE DISTANCE TO NEARBY STAR-FORMING REGIONS. III. HP TAU/G2 AND THE THREE-DIMENSIONAL STRUCTURE OF TAURUS

The Astrophysical Journal ◽

10.1088/0004-637x/698/1/242 ◽

2009 ◽

Vol 698 (1) ◽

pp. 242-249 ◽

Cited By ~ 127

Author(s):

Rosa M. Torres ◽

Laurent Loinard ◽

Amy J. Mioduszewski ◽

Luis F. Rodríguez

Keyword(s):

Three Dimensional ◽

Dimensional Structure ◽

Nearby Star ◽

Three Dimensional Structure ◽

Star Forming ◽

Star Forming Regions

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VERA observations of the Galactic star-forming regions ON1 and ON2N

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312021850 ◽

2012 ◽

Vol 8 (S289) ◽

pp. 418-421

Author(s):

Takumi Nagayama ◽

Keyword(s):

Angular Velocity ◽

Very Long Baseline Interferometry ◽

Three Dimensional ◽

Galactic Rotation ◽

Tangent Point ◽

Star Forming ◽

Star Forming Regions ◽

Long Baseline

AbstractWe carried out astrometric observations with VERA of H2O masers in ON1 and ON2N. The measured distances to ON1 and ON2N are 2.47 ± 0.11 and 3.83 ± 0.13 kpc, respectively. We found that ON1 and ON2N are located near the tangent point and the Solar circle, respectively. We derive an angular velocity of the Galactic rotation at the Sun's position (i.e. the ratio of the Galactic constants) of 28 ± 2 km s−1 kpc−1 using the measured distances and three-dimensional velocity components of the two sources. This value is consistent with recent estimates obtained using Very Long Baseline Interferometry but different from the IAU-recommended value of 25.9 km s−1 kpc−1.

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Self-Gravitational Instability of an Isothermal Gaseous Slab under High External Pressure

Symposium - International Astronomical Union ◽

10.1017/s0074180900221244 ◽

2001 ◽

Vol 205 ◽

pp. 286-287

Author(s):

Michihisa Umekawa ◽

Ryoji Matsumoto ◽

Shigeki Miyaji ◽

Tatsuo Yoshida

Keyword(s):

Star Formation ◽

Galactic Center ◽

Gravitational Instability ◽

Three Dimensional ◽

External Pressure ◽

Star Forming ◽

Star Forming Regions ◽

Field Lines ◽

Hydrodynamical Simulations ◽

The Magnetic Field

In active massive star forming regions such as Orion and the Galactic center, the self-gravitational instability of a magnetized gaseous slab plays an important role as a trigger of star formation. In such high external pressure regions, the incompressible mode of self-gravitational instability (Elmegreen & Elmegreen 1978; Lubow & Pringle 1992) becomes dominant. Based on two-dimensional hydrodynamical simulations, Umekawa et al. (1999) proposed “Star formation by merging of the Jeans stable clumps” in a pressure bounded slab. In a magnetized slab confined by external pressure, Nagai et al. (1998) showed by linear analysis that the slab fragments to filaments parallel to the magnetic field lines. Here, we show by nonlinear three-dimensional MHD simulations that the filaments further fragment to Jeans stable clumps.

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Full-polarization maps of OH main-line masers in the W51 and G351.78-0.54 star-forming regions

Symposium - International Astronomical Union ◽

10.1017/s0074180900222729 ◽

2002 ◽

Vol 206 ◽

pp. 367-370

Author(s):

Alice L. Argon ◽

Mark J. Reid ◽

Karl M. Menten

Keyword(s):

Magnetic Field ◽

Spectral Line ◽

Ground State ◽

Three Dimensional ◽

Main Line ◽

Dimensional Structure ◽

Strong Magnetic Fields ◽

Star Forming ◽

Star Forming Regions ◽

High Degree

Full-polarization spectral-line VLBA observations were made of the ground state, main-line, 2π3/2J = 3/2 OH masers in two Galactic star-forming regions: the “e1”/ “e2” region of W51 and G351.78-0.54. Two especially interesting results are presented. (1) Two of the 27 Zeeman pairs in W51 were found to be associated with unusually strong magnetic fields (≈ 20 mG), more than twice as strong as for any previously reported OH maser. (2) G351.78-0.54 was found to exhibit a high degree of linear polarization (up to 61%), which constrains the three dimensional structure of its magnetic field.

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