The Fragmenting Superbubble Associated with the H<scp>ii</scp>Region W4

West, Jennifer L.; English, Jayanne; Normandeau, M.; Landecker, T. L.

doi:10.1086/510609

Cited by 28 publications

(91 citation statements)

References 33 publications

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“…Follow-up Hα observations (Dennison et al 1997) showed that the ionized gas is detected in the periphery of the H i cavity and revealed an enclosed superbubble rather than a chimney, which is sealed at about b = 7 • . As shown by West et al (2007), the appearance of this huge structure seen from the 1.4 GHz radio continuum emission also resembles a closed bubble. We therefore refer to it as "W4 superbubble" in this work.…”

Section: Introductionmentioning

confidence: 70%

“…Based on the tight correlation between radio continuum and Hα emission and the flat radio spectrum derived between 408 MHz and 1420 MHz, West et al (2007) conclude that the radio continuum emission from the shells of the W4 superbubble is optically thin thermal emission. We confirmed this by deriving the spectral index from the present data using TT-plots (Turtle et al 1962) between 1.4 GHz and 4.8 GHz.…”

Section: Total Intensity Emission and Spectral Informationmentioning

confidence: 87%

“…This leakage was indirectly confirmed by the discovery of an even larger A&A 578, A24 (2015) high-latitude Hα loop on top of the W4 superbubble extending up to b = 30 • (Reynolds et al 2001). The distance to the W4 superbubble was taken as 2.2 kpc in the work of Normandeau et al (1996), Dennison et al (1997), Reynolds et al (2001), and Terebey et al (2003), while 2.35 kpc was used by Basu et al (1999) and West et al (2007). Through measuring the trigonometric parallax of the methanol maser, Xu et al (2006) got 1.95 kpc for the distance of the W3 OH region.…”

Section: Introductionmentioning

confidence: 95%

“…The Stockert λ21 cm total intensity northern sky survey (Reich 1982;Reich & Reich 1986) and the DRAO 26-m single-dish polarization survey (Wolleben et al 2006) provided the missing large-scale intensities and the absolute zero levels. We also added high-resolution λ21 cm data observed with the DRAO synthesis telescope by West et al (2007) and Landecker et al (2010) to the large-scale corrected EMLS maps.…”

Section: Datamentioning

confidence: 99%

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Magnetic fields of the W4 superbubble

Gao

Reich

et al. 2015

A&A

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Context. Superbubbles and supershells are the channels for transferring mass and energy from the Galactic disk to the halo. Magnetic fields are believed to play a vital role in their evolution. Aims. We study the radio continuum and polarized emission properties of the W4 superbubble to determine its magnetic field strength. Methods. New sensitive radio continuum observations were made at λ6 cm, λ11 cm, and λ21 cm. The total intensity measurements were used to derive the radio spectrum of the W4 superbubble. The linear polarization data were analysed to determine the magnetic field properties within the bubble shells. Results. The observations show a multi-shell structure of the W4 superbubble. A flat radio continuum spectrum that stems from optically thin thermal emission is derived from 1.4 GHz to 4.8 GHz. By fitting a passive Faraday screen model and considering the filling factor f ne , we obtain the thermal electron density n e = 1.0/ f ne (±5%) cm −3 and the strength of the line-of-sight component of the magnetic field B // = −5.0/ f ne (±10%) μG (i.e. pointing away from us) within the western shell of the W4 superbubble. When the known tilted geometry of the W4 superbubble is considered, the total magnetic field B tot in its western shell is greater than 12 μG. The electron density and the magnetic field are lower and weaker in the high-latitude parts of the superbubble. The rotation measure is found to be positive in the eastern shell but negative in the western shell of the W4 superbubble, which is consistent with the case where the magnetic field in the Perseus arm is lifted up from the plane towards high latitudes. Conclusions. The magnetic field strength and the electron density we derived for the W4 superbubble are important parameters for evolution models of superbubbles breaking out of the Galactic plane.

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Section: Introductionmentioning

confidence: 70%

Section: Total Intensity Emission and Spectral Informationmentioning

confidence: 87%

Section: Introductionmentioning

confidence: 95%

Section: Datamentioning

confidence: 99%

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Magnetic fields of the W4 superbubble

Gao

Reich

et al. 2015

A&A

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“…Nevertheless, there are very few measurements of magnetic fields in such objects (for another example see West et al 2007). …”

Section: Stellar-wind Bubble In the Anticentrementioning

confidence: 99%

A Survey of the polarized emission from the Galactic plane at 1420 MHz with arcminute angular resolution

Landecker¹,

Reich

Reid³

et al. 2010

A&A

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111

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Context. Observations of polarized emission are a significant source of information on the magnetic field that pervades the interstellar medium of the Galaxy. Despite the acknowledged importance of magnetic fields in interstellar processes, our knowledge of field configurations on all scales is seriously limited. Aims. This paper describes an extensive survey of polarized Galactic emission at 1.4 GHz that provides data with arcminute resolution and complete coverage of all structures from the broadest angular scales to the resolution limit, giving information on the magnetoionic medium over a wide range of interstellar environments. • 5. This is the first extensive polarization survey to present aperture-synthesis data combined with data from single antennas, and the techniques developed to achieve this combination are described. Results. The appearance of the extended polarized emission at 1.4 GHz is dominated by Faraday rotation along the propagation path, and the diffuse polarized sky bears little resemblance to the total-intensity sky. There is extensive depolarization, arising from vector averaging on long lines of sight, from H ii regions, and from diffuse ionized gas seen in Hα images. Preliminary interpretation is presented of selected polarization features on scales from parsecs (the planetary nebula Sh 2-216) to hundreds of parsecs (a superbubble GSH 166−01−17), to kiloparsecs (polarized emission in the direction of Cygnus X).

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New results from Galactic ISM surveys: The frothy ISM

McClure-Griffiths

2012

Astron Nachr

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The past 10 years have seen a resurgence in studies of the Milky Way's interstellar medium (ISM) driven by new surveys of the Galactic plane at wavelengths from 4 microns to 20 cm. These surveys, which include the H I International Galactic Plane Survey, the Spitzer GLIMPSE and MIPSGAL surveys, the recently commenced Herschel HI-GAL survey, and several surveys of CO J = 1-0, are allowing us to trace the evolution of the ISM on scales of parsecs and sub-parsecs from warm and diffuse through to cold, dusty molecular gas. Together with hydrodynamical simulations of ever-increasing sophistication our understanding of the ISM in the disk of the Milky Way has evolved from the 1970's simplistic models of cold clouds surrounded by warm gas to a complex mixture of phases intertwined and interconnected, whose cooling is driven by colliding flows. Here I focus on the "frothy" ISM, where structure and evolution is impacted by bubbles, shells and supershells. I discuss the role of these objects in cooling, the formation of molecules and even the transfer of matter out of the disk of the Galaxy.

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The Fragmenting Superbubble Associated with the HiiRegion W4

Cited by 28 publications

References 33 publications

Magnetic fields of the W4 superbubble

Magnetic fields of the W4 superbubble

A Survey of the polarized emission from the Galactic plane at 1420 MHz with arcminute angular resolution

New results from Galactic ISM surveys: The frothy ISM

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