Astrometry of 6.7 GHz Methanol Maser toward W 3(OH) with Japanese VLBI Network

Matsumoto, Naoko; Honma, Mareki; Isono, Yasuko; Ujihara, Hideki; Kimura, Kouji; Matsumoto, Kazuya; Sawada-Satoh, Satoko; Doi, Akira; Fujisawa, Kenta; Ueno, Yuji

doi:10.1093/pasj/63.6.1345

Cited by 14 publications

(10 citation statements)

References 33 publications

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“…Class II methanol masers emission comes from dense molecular cores, several hundreds of AUs from the central, exciting stars (see example in Goddi et al 2011;Matsumoto et al 2011 Sato et al (2010b), the uncertainty is estimated to be ±4 km s −1 .…”

Section: Local Standard Of Rest Velocitymentioning

confidence: 99%

“…Water masers are collisionally excited and are usually associated with shocked gas in jets and outflows launched by young stellar objects (YSOs), as well as from evolved stars (Hachisuka et al 2006;Deacon et al 2007). Class II methanol masers are produced by radiative pumping in warm, dense, and dusty environments around massive YSOs (Sobolev et al 1997;Cragg et al 2001Cragg et al , 2005Goddi et al 2011;Matsumoto et al 2011).…”

Section: Introductionmentioning

confidence: 99%

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Trigonometric parallaxes of star-forming regions in the Sagittarius spiral arm

Sato

Reid

et al. 2014

A&A

144

103

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We report measurements of parallaxes and proper motions of ten high-mass star-forming regions in the Sagittarius spiral arm of the Milky Way as part of the BeSSeL Survey with the VLBA. Combining these results with eight others from the literature, we investigated the structure and kinematics of the arm between Galactocentric azimuths β ≈ −2• and 65• . We found that the spiral pitch angle is 7• .3 ± 1• .5; the arm's half-width, defined as the rms deviation from the fitted spiral, is ≈0.2 kpc; and the nearest portion of the Sagittarius arm is 1.4 ± 0.2 kpc from the Sun. Unlike for adjacent spiral arms, we found no evidence for significant peculiar motions of sources in the Sagittarius arm opposite to Galactic rotation.

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Section: Local Standard Of Rest Velocitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Trigonometric parallaxes of star-forming regions in the Sagittarius spiral arm

Sato

Reid

et al. 2014

A&A

144

103

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“…Rotational motion associated with a disk has been demonstrated by measuring the internal proper motions in a few methanol masers (Sanna et al 2010a,b;Moscadelli et al 2011), while outflow motion has been measured in other methanol sources (Rygl et al 2010;Sugiyama et al 2011;Matsumoto et al 2011;Sawada-Satoh et al 2013). Goddi et al (2011) directly detected infall motion with a velocity of 5 km s −1 in the molecular envelope of the high-mass YSO AFGL 5142 MM-1 at a radius of 300 au.…”

Section: Introductionmentioning

confidence: 99%

Rotating and infalling motion around the high-mass young stellar object Cepheus A-HW2 observed with the methanol maser at 6.7 GHz

Sugiyama

Fujisawa

Doi

et al. 2014

A&A

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Context. Proper motion observations of masers can provide information on dynamic motions on scales of a few milliarcseconds per year (mas yr −1 ) at radii of 100-1000 au scales from central young stellar objects (YSOs). Aims. The 6.7 GHz methanol masers are one of the best probes for investigations of the dynamics of high-mass YSOs, and in particular for tracing the rotating disk. We have measured the internal proper motions of the 6.7 GHz methanol masers associated with Cepheus A (Cep A) HW2 using Very Long Baseline Interferometery (VLBI) observations. Methods. We conducted three epochs of VLBI monitoring observations of the 6.7 GHz methanol masers in Cep A-HW2 with the Japanese VLBI Network (JVN) over the period [2006][2007][2008]. In 2006, we were able to use phase-referencing to measure the absolute coordinates of the maser emission with an accuracy of a few milliarcseconds. We compared the maser distribution with other molecular line observations that trace the rotating disk. Results. We measured the internal proper motions for 29 methanol maser spots, of which 19 were identified at all three epochs and the remaining ten at only two epochs. The magnitude of proper motions ranged from 0.2 to 7.4 km s −1 , with an average of 3.1 km s −1 . Although there are large uncertainties in the observed internal proper motions of the methanol maser spots in Cep A, they are well fitted by a disk that includes both rotation and infall velocity components. The derived rotation and infall velocities at the disk radius of 680 au are 0.5 ± 0.7 and 1.8 ± 0.7 km s −1 , respectively. Conclusions. Assuming that the modeled disk motion accurately represents the accretion disk around the Cep A-HW2 high-mass YSO, we estimated the mass infall rate to be 3 × 10 −4 n 8 M yr −1 (n 8 is the gas volume density in units of 10 8 cm −3 ). The combination of the estimated mass infall rate and the magnitude of the fitted infall velocity suggests that Cep A-HW2 is at an evolutionary phase of active gas accretion from the disk onto the central high-mass YSO. The infall momentum rate is estimated to be 5 × 10 −4 n 8 M yr −1 km s −1 , which is larger than the estimated stellar radiation pressure of the HW2 object, supporting the hypothesis that this object is in an active gas accretion phase.

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Section: Introductionmentioning

confidence: 96%

“…The distance to the W3(OH) region is estimated to be 1.83 ± 0.14 kpc (Imai et al 2000), 1.95 ± 0.04 kpc (Xu et al 2006), 2.04 ± 0.07 kpc (Hachisuka et al 2006), and 1.67 (+0.21/−0.17) kpc (Matsumoto et al 2011) from very long baseline interferometry parallax measurements. In this paper, we adopt the most recent value for W4 of 1.7 kpc (Matsumoto et al 2011). The main exciting stars of W4 8 are HD15570 (BD+60 • 504; O4If; Massey et al 1995) and HD15558 (BD+60 • 502; O5.5III+O7V; De Becker et al 2006), located at the projected distance of ∼13-14 pc from the cloud and illuminating BRC 5 from the east as indicated by the arrow in the Hα image of Figure 1.…”

Section: Introductionmentioning

confidence: 96%

Triggered Star Formation in a Bright-Rimmed Cloud (Brc 5) of Ic 1805

Fukuda

Miao

Sugitani

et al. 2013

ApJ

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We report recent optical, near-infrared (NIR), and millimeter observations which have revealed some new features of the bright-rimmed cloud BRC 5 associated with W4. With slitless spectroscopy, we detected 17 Hα emission stars around the cloud; 4 are near the surface of the cloud, and 1 is toward IRAS 02252+6120. NIR photometry shows that the central Hα emission star, together with one bright infrared source, has large NIR excesses and Class I spectral energy distributions. These two Class I objects are associated with the 2.9 mm continuum peaks and with a bipolar outflow, and are in between two separate, elongated C 18 O(J = 1-0) cores. The C 18 O cores and the two Class I sources are aligned along a line at position angle ∼240 • , somewhat less than perpendicular to the direction of UV radiation from the OB stars. Most of the detected Hα emission stars, all T Tauri candidates, are located within ∼3 of the cloud on the exciting star side. An estimate of the age of the stars based on a color-magnitude diagram suggests that these T Tauri candidates have ages of ∼1 Myr or less, but are more evolved objects than the central young stellar objects. This age sequence suggests sequential star formation within the BRC 5 cloud. The 13 CO(J = 1-0) emission shows three elongated structures, which indicates the asymmetric structure toward the UV incident axis. We present our exploratory simulation results by using a smoothed particle hydrodynamic code that suggests that the asymmetrical BRC 5 structure could possibly result from the evolution of a preexisting prolate molecular cloud subject to radiation-driven implosion (RDI). Our best-fit prolate cloud has an initial mass of ∼400 M , an axial ratio of ∼1.7, and a semi-major axis of ∼1.6 pc, pointing away from the ionization flux by an angle of 15 • . The simulated cloud structure not only closely matches the observed asymmetric morphological structure of BRC 5, but also reveals the possibility of the development of two major cores at the head of BRC 5. For the first time, the possibility of forming two stars by an RDI mechanism in a BRC is investigated.

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Astrometry of 6.7 GHz Methanol Maser toward W 3(OH) with Japanese VLBI Network

Cited by 14 publications

References 33 publications

Trigonometric parallaxes of star-forming regions in the Sagittarius spiral arm

Trigonometric parallaxes of star-forming regions in the Sagittarius spiral arm

Rotating and infalling motion around the high-mass young stellar object Cepheus A-HW2 observed with the methanol maser at 6.7 GHz

Triggered Star Formation in a Bright-Rimmed Cloud (Brc 5) of Ic 1805

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