Distance and kinematics of the W49N H2O maser outflow

Gwinn, C. R.; Moran, J. M.; Reid, M. J.

doi:10.1086/171493

Cited by 189 publications

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“…At a distance of $11.4 kpc (Gwinn et al 1992), W49A is one of the most active massive star-forming sites in our Galaxy (Alves & Homeier 2003). The total luminosity exceeds $10 7 L .…”

Section: Introductionmentioning

confidence: 95%

Hard X‐Rays from Ultracompact HiiRegions in W49A

Tsujimoto

Hosokawa

Feigelson

et al. 2006

ApJ

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We report the Chandra detection of hard X-ray emission from the Welch ring in W49A, an organized structure of ultracompact (UC ) H ii regions containing a dozen nascent early-type stars. Two UC H ii regions are associated with hard X-ray emission in a deep Advanced CCD Imaging Spectrometer (ACIS) image exposed for $96.7 ks. One of the two X-ray sources has no near-infrared counterpart and is extended by $5 00 , or $0.3 pc, at a distance of $11.4 kpc, which is spatially aligned with the cometary radio continuum emission associated with the UC H ii region. The X-ray spectrum of the emission, when fit with a thermal model, indicates a heavily absorbed plasma with extinction of $5 ; 10 23 cm À2 , temperature $7 keV, and X-ray luminosity in the 3.0Y8.0 keV band of $3;10 33 ergs s À1 . Both the luminosity and the size of the emission resemble the extended hard emission found in UC H ii regions in Sagittarius B2, yet they are smaller by an order of magnitude than the emission found in massive star clusters such as NGC 3603. Three possibilities are discussed for the cause of the hard extended emission in the Welch ring: an ensemble of unresolved point sources, shocked interacting winds of the young O stars, and a wind-blown bubble interacting with ambient cold matter. Subject headingg s: H ii regions -ISM: individual ( W49A) -radio continuum: ISM -stars: early-type -X-rays: ISM

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“…At a distance of $11.4 kpc (Gwinn et al 1992), W49A is one of the most active massive star-forming sites in our Galaxy (Alves & Homeier 2003). The total luminosity exceeds $10 7 L .…”

Section: Introductionmentioning

confidence: 95%

Hard X‐Rays from Ultracompact HiiRegions in W49A

Tsujimoto

Hosokawa

Feigelson

et al. 2006

ApJ

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“…Using aperture synthesis techniques, one can both map the geometry of the maser spots and trace their very fine proper motions. Adding radial velocity information derived from the Doppler shift of the maser line results in a detailed picture of the maser geometry and kinematics as a measure of the dynamics very close to the YSO (e.g., Genzel et al 1981aGenzel et al , 1981bSchneps et al 1981;Gwinn, Moran, & Reid 1992).…”

Section: Introductionmentioning

confidence: 99%

Expansion of the R4 H₂O Maser Arc near Cepheus A HW2

Gallimore

Cool

Thornley

et al. 2003

ApJ

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We present new (2000 April) MERLIN observations of the H 2 O masers located near the protostar Cepheus A HW2. The MERLIN observations detect many of the structures found in earlier (1996) Very Long Baseline Array (VLBA) observations of Torrelles and collaborators, and the changed positions of these structures are compatible with the VLBA proper motions and astrometric uncertainties. The radius of curvature of the R4 structure of maser arcs appears to have grown by a factor of 2, and the displacement of the arcs between 1996 and 2000 is compatible with expansion about a common center. In addition, the MERLIN observations detect redshifted masers not previously found; taken with the newly discovered masers, the R4 structure now resembles patchy emission from an elliptical ring. We demonstrate that a simple bow shock model cannot simultaneously account for the shape and the velocity gradient of the R4 structure. A model involving a slow, hydromagnetic shock propagating into a rotating, circumstellar disk better describes the maser spot kinematics and luminosities. In this model, the central mass is 3 M , and we demonstrate that the mass of the disk is negligible in comparison. The expansion velocity of the postshock gas, $5 km s À1 , is slow compared to the shock velocity, v S $ 13 km s À1 , suggesting that the postshock gas is magnetically supported with a characteristic field strength of $30 mG. We speculate that the expanding maser rings R4 and R5 may be generated by periodic, instability-driven winds from young stars that periodically send spherical shocks into the surrounding circumstellar material.

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“…The center of expansion (CE) of Gwinn et al (1992) for H 2 O maser spots at W49N is denoted by + in Fig. 1.…”

Section: Observations and Resultsmentioning

confidence: 99%

“…All for a region of about one arcsecond square near the center of the field. The deconvolved major axis (mjax) of the spots are between 30 to 70 mas and the ratio of mjax to minor axis (mnax) range from about 1.5:1 to 3:1.The center of expansion (CE) of Gwinn et al (1992) for H 2 O maser spots at W49N is denoted by + in Fig. 1.…”

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confidence: 99%

Scattered OH Maser sources in the direction of W49N

et al. 2008

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Abstract. OH masers spots are observed with the VLBA at 1612, 1665 and 1667 MHz. The orientation of the ellipses resulting from scattering are all nearly aligned perpendicular to the galactic plane. These ordered orientation could be due to the galactic magnetic field. Keywords. OH masers -W49N -interstellar scattering Observations and resultsUsing VLBA observations of 2005 October 6 towards W49N at the 1612 MHz, 1665 MHz and 1667 MHz OH frequencies, 215 maser spots were detected (Fig.1). LCP and RCP are observed simultaneously in 240 spectral channels with a resolution of 0.1 km/sec in a range of about 22 km/sec. The beam size is about 20 mas by 15 mas at a position angle of 84 degrees. The galactic plane is at a position angle of 30 degrees. The magnetic field at the maser emitting region obtained based on Zeeman pairs gives values from -4 to 6 mGauss. All for a region of about one arcsecond square near the center of the field. The deconvolved major axis (mjax) of the spots are between 30 to 70 mas and the ratio of mjax to minor axis (mnax) range from about 1.5:1 to 3:1.The center of expansion (CE) of Gwinn et al. (1992) for H 2 O maser spots at W49N is denoted by + in Fig. 1. The velocities of the nearest spots are slightly higher or smaller than 9 km/s, a value near the middle of the entire velocity range that we use as reference in Fig. 1a). Red shifted spots predominantly appear at the right (as also observed by Kent & Mutel (1982)) and blue shifted spots are located at the left, slightly to the north respect the red shifted spots, as occurs for H 2 O spots (Gwinn et al. 1992). However, the left hand side H 2 O spots are red shifted while the OH of the same side are blue shifted and vice versa.The principal axis (PA) takes values from about 80 to 130 degrees, i.e., even though the spots are spread more than 7×10 4 AU, their PAs are all nearly aligned. Most of the ellipses of the right group are oriented as if they would be traced from the CE but the ellipses of the left hand side group do not follow any given orientation respect the CE.The larger PA values take place at the larger mnax (Fig. 2) and a similar correlation is observed between PA and mjax. However, there is no correlation between PA and the majax/minax ratio. This suggests that it is the size of the spots and not the ratio of their axes that correlates with PA. 95available at https://www.cambridge.org/core/terms. https://doi

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Distance and kinematics of the W49N H2O maser outflow

Cited by 189 publications

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Hard X‐Rays from Ultracompact HiiRegions in W49A

Hard X‐Rays from Ultracompact HiiRegions in W49A

Expansion of the R4 H₂O Maser Arc near Cepheus A HW2

Scattered OH Maser sources in the direction of W49N

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Distance and kinematics of the W49N H2O maser outflow

Cited by 189 publications

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Hard X‐Rays from Ultracompact HiiRegions in W49A

Hard X‐Rays from Ultracompact HiiRegions in W49A

Expansion of the R4 H2O Maser Arc near Cepheus A HW2

Scattered OH Maser sources in the direction of W49N

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Expansion of the R4 H₂O Maser Arc near Cepheus A HW2