Large-Scale Structure and Dynamics of Cassiopeia OB7

Cazzolato, François; Pineault, S.

doi:10.1086/368242

Cited by 14 publications

(9 citation statements)

References 20 publications

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“…Only two regions, Sh2‐171 and Sh2‐167, have radial velocities outside this range, of about −12 and −66 km s −1 , respectively. As mentioned by Cazzolato & Pineault (2003), Sh2‐180, Sh2‐181 and Sh2‐182 may be associated with Cas OB7. Sh2‐179 is a planetary nebula (Kerber et al 2003).…”

Section: The Big Picturementioning

confidence: 80%

Unveiling the birth and evolution of the H ii region Sh2-173

Cichowolski

Romero

Ortega

et al. 2009

Monthly Notices of the Royal Astronomical Society

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Based on a multiwavelength study, the interstellar medium around the H ii region Sh2‐173 has been analysed. The ionized region is clearly detected in the optical and the radio continuum images. The analysis of the H i data shows a region of low emissivity that has an excellent morphological correlation with the radio continuum emission. The H ii region is partially bordered by a photodissociation region, which, in turn, is encircled by a molecular structure. The H i and CO structures related to Sh2‐173 are observed in the velocity ranges from −25 to −31 km s−1 and from −27 to −39 km s−1, respectively. Taking into account the presence of non‐circular motions in the Perseus spiral arm, together with previous distance estimates for the region, we adopt a distance of 2.5 ± 0.5 kpc for Sh2‐173. Seven hot stars were identified in the field of Sh2‐173, being only one O‐type star. The amount of energetic photons emitted by this star is enough to keep the region ionized and heat the dust. Given that an expanding H ii region may trigger star formation, a search for young stellar object (YSO) candidates was made using different infrared point source catalogues. A population of 46 YSO candidates was identified, projected on to the molecular clouds. On the other hand, Sh2‐173 is located in a dense edge of a large (∼5°) H i shell, GSH 117.8+1.5‐35. The possibility of Sh2‐173 being part of a hierarchical system of three generations is suggested. In this scenario, the large H i shell, which probably originated due to the action of Cas OB5, would have triggered the formation of Sh2‐173, which, in turn, is triggering new stars in its surrounding molecular cloud. To test this hypothesis, the ages of both the H ii region and the large shell were estimated and compared. We concluded that Sh2‐173 is a young H ii region of about 0.6–1.0 Myr old. As for the large shell, we obtained a dynamical age of 5 ± 1 Myr. These age estimates, together with the relative location of the different structures, support the hypothesis that Sh2‐173 is part of a hierarchical system.

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Section: The Big Picturementioning

confidence: 80%

Unveiling the birth and evolution of the H ii region Sh2-173

Cichowolski

Romero

Ortega

et al. 2009

Monthly Notices of the Royal Astronomical Society

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“…However due to the spiral shock at the leading edge of the Perseus arm (Roberts 1972), the dynamical distance has a large error. Measurements of Cas OB7 show that the radial velocity of the gas can be displaced by about −20 km s −1 due to that shock (Cazzolato & Pineault 2003). Since Sh 183 is located at the boundary of Cas OB7, we make a similar correction and obtain a distance of about 3.6 kpc, which places Sh 183 on the far side of, or just behind the Perseus arm.…”

Section: Sh 183mentioning

confidence: 93%

A Sino-German $\mathsf{\lambda}$6 cm polarization survey of the Galactic plane

Sun

Han

Reich

et al. 2006

A&A

139

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Aims. Polarization measurements of the Galactic plane at λ6 cm probe the interstellar medium (ISM) to larger distances compared to measurements at longer wavelengths, enabling us to investigate properties of the Galactic magnetic fields and electron density. Methods. We are conducting a new λ6 cm continuum and polarization survey of the Galactic plane covering 10• ≤ l ≤ 230• and |b| ≤ 5• . Missing large-scale structures in the U and Q maps are restored based on extrapolated polarization K-band maps from the WMAP satellite. The λ6 cm data are analyzed together with maps in other bands. Results. We discuss some results for the first survey region, 7• × 10 • in size, centered at (l, b) = (125.• 5, 0 • ). Two new passive Faraday screens, G125.6−1.8 and G124.9+0.1, were detected. They cause significant rotation of background polarization angles but little depolarization. G124.9+0.1 was identified as a new faint HII region at a distance of 2.8 kpc. G125.6−1.8, with a size of about 46 pc, has neither a counterpart in enhanced Hα emission nor in total intensity. A model combining foreground and background polarization modulated by the Faraday screen was developed. Using this model, we estimated the strength of the ordered magnetic field along the line of sight to be 3.9 µG for G124.9+0.1, and exceeding 6.4 µG for G125.6−1.8. We obtained an estimate of 2.5 and 6.3 mK kpcfor the average polarized and total synchrotron emissivity towards G124.9+0.1. The synchrotron emission beyond the Perseus arm is quite weak. A spectral curvature previously reported for SNR G126.2+1.6 is ruled out by our new data, which prove a straight spectrum. Conclusions. The new λ6 cm survey will play an important role in improving the understanding of the properties of the magnetoionic ISM. The magnetic fields in HII regions can be measured. Faraday screens with very low electron densities but large rotation measures were detected indicating strong and regular magnetic fields in the ISM. Information about the local synchrotron emissivity can be obtained.Key words. surveys -polarization -radio continuum: general -methods: observational -ISM: magnetic fields -ISM: supernova remnants IntroductionThe first detection of diffuse polarized emission from the Milky Way Galaxy (Westerhout et al. 1962;Wielebinski et al. 1962) confirmed that its non-thermal radiation originates from synchrotron emission. The two major sources of polarized emission from our Galaxy are diffuse radio emission associated with the Galactic disk produced by relativistic electrons spiraling in interstellar magnetic fields, and discrete sources such as supernova remnants (SNRs) with compressed interstellar magnetic fields, where relativistic electrons are accelerated by shocks.To understand the properties of the ISM in our Galaxy a number of whole sky surveys (e.g. as reviewed by Reich 2003) have been made. Also large-scale radio surveys of the Galactic plane with higher angular resolution have been performed. The large-scale surveys clearly show the concentration of emission ...

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“…The spectra of these stars, members of the Cas OB7 association, were studied by Miroshnichenko et al (2009). The presence of the component with Vr =−61.6 km/s allows us to consider the distance to the Cas OB7 association d = 2.5 kpc from Cazzolato and Pineault (2003) as a lower limit for the distance to IRAS 23304.…”

Section: Peculiarities Of the Optical Spectrummentioning

confidence: 99%

Peculiarities of the atmosphere and envelope of a post-AGB star, the optical counterpart of IRAS 23304+6347

2015

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Based on high-spectral resolution observations performed with the echelle spectrograph NES of the 6-meter telescope, we have studied the peculiarities of the spectrum and the velocity field in the atmosphere and envelope of the optical counterpart of the infrared source IRAS 23304+6347. We have concluded about the absence of significant variations in the radial velocity Vr inferred from atmospheric absorptions and about its coincidence with the systemic velocity deduced from radio data. The envelope expansion velocity Vexp = 15.5 km/s has been determined from the positions of rotational band lines of the C 2 Swan (0; 0) band. A complex emission-absorption profile of the Swan (0; 1) 5635Å has been recorded. Analysis of the multicomponent NaI D doublet line profile has revealed interstellar components V(IS) = −61.6 and −13.2 km/s as well as a circumstellar component with V(CS) =−41.0 km/s whose position corresponds to the velocity inferred from C 2 features. The presence of the interstellar component with Vr =−61.6 km/s in the spectrum allows d = 2.5 kpc to be considered as a lower limit for the distance to the star. A splitting of the profiles for strong absorptions of ionized metals (YII, BaII, LaII, SiII) attributable to the presence of a short-wavelength component originating in the circumstellar envelope has been detected in the optical spectrum of IRAS 23304+6347 for the first time.

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Large-Scale Structure and Dynamics of Cassiopeia OB7

Cited by 14 publications

References 20 publications

Unveiling the birth and evolution of the H ii region Sh2-173

Unveiling the birth and evolution of the H ii region Sh2-173

A Sino-German $\mathsf{\lambda}$6 cm polarization survey of the Galactic plane

Peculiarities of the atmosphere and envelope of a post-AGB star, the optical counterpart of IRAS 23304+6347

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