Observational Evidence of Supershell Blowout in GS 018−04+44: The Scutum Supershell

Callaway, Matthew B.; Savage, Blair D.; Benjamin, Robert A.; Haffner, L. M.; Tufte, S. L.

doi:10.1086/308601

Cited by 27 publications

(19 citation statements)

References 47 publications

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“…More data are needed to confirm any relation. The H ii region Sh 2-50 is probably associated with the Scutum super shell at a distance of about 3.3 kpc (Callaway et al 2000), which is close to the polarization horizon at λ6 cm as discussed by Sun et al (2011).…”

Section: Polarizationmentioning

confidence: 66%

A Sino-Germanλ6 cm polarization survey of the Galactic plane

Sun

Reich

et al. 2011

A&A

119

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Aims. We study the spectral and polarization properties of supernova remnants (SNRs) using our λ6 cm survey data. Methods. We analyse data from observations taken as part of the Sino-German λ6 cm polarization survey of the Galactic plane. By using the integrated flux densities at λ6 cm together with measurements at other wavelengths from the literature, we derive the global spectra of 50 SNRs. In addition, from the observations at λ6 cm we obtain the polarization images of 24 SNRs. Results. We derive integrated flux densities at λ6 cm for 51 small SNRs with angular sizes smaller than 1 • . We are able to derive global radio spectral indices in all the cases except for Cas A. For the SNRs G15.1−1.6, G16.2−2.7, G16.4−0.5, G17.4−2.3, G17.8−2.6, G20.4+0.1, G36.6+2.6, G43.9+1.6, G53.6−2.2, G55.7+3.4, G59.8+1.2, G68.6−1.2, and G113.0+0.2, the spectra have been significantly improved. From our analysis, we argue that the object G16.8−1.1 is probably an H ii region instead of a SNR. Cas A shows a secular decrease in total intensity, and we measure a flux density of 688 ± 35 Jy at λ6 cm between 2004 and 2008. We detect polarized emission from 25 SNRs. For G16.2−2.7, G69.7+1.0, G84.2−0.8, and G85.9−0.6, the polarized emission is detected for the first time confirming that they are SNRs. Conclusions. High-frequency observations of SNRs are difficult but essential to determine their spectra and measure their polarization in particular towards the inner Galaxy, where Faraday effects are important.

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Section: Polarizationmentioning

confidence: 66%

A Sino-Germanλ6 cm polarization survey of the Galactic plane

Sun

Reich

et al. 2011

A&A

119

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“…The two O-type stars have an angular separation of 1.3 degrees, that translates to ∼50 pc. Both objects could be related to the "blowout" observed in the Scutum Supershell (Callaway et al 2000).…”

Section: Hd 175754 and Hd 175876mentioning

confidence: 93%

The origin of massive O-type field stars

Wit¹,

Testi²,

Palla³

et al. 2004

A&A

110

136

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Abstract. We present a study aimed at clarifying the birthplace for 43 massive O-type field stars. In this first paper we present the observational part: a search for stellar clusters near the target stars. We derive stellar density maps at two different resolving scales, viz. ∼0.25 pc and ∼1.0 pc from NTT and TNG imaging and the 2MASS catalogue. These scales are typical for cluster sizes. The main result is that the large majority of the O-type field population are isolated stars: only 12% (5 out of 43) of the O-type field stars is found to harbour a small-scale stellar cluster. We review the literature and aim at characterizing the stellar field of each O-type field star with the emphasis on star formation and the presence of known young stellar clusters. An analysis of the result of this paper and a discussion of the O-type field population as products of a dynamical ejection event is presented in an accompanying paper.

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“…Both sight lines lie in the general direction of the Scutum supershell (GS 018À04+44), which is centered at l ¼ 17=5, b ¼ À4 at a distance of d $ 3:5 kpc and which spans about 5 on the sky (Callaway et al 2000). HD 177989 is situated behind the Scutum supershell, while HD 175876 is in front of it (see Table 7).…”

Section: Hd 175876 Hd 177989 and The Scutum Supershellmentioning

confidence: 99%

Highly Ionized Gas in the Galactic Halo: AFUSESurvey of OviAbsorption toward 22 Halo Stars

Zsargó

Sembach

Howk

et al. 2003

ApJ

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Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of 22 Galactic halo stars are studied to determine the amount of O vi in the Galactic halo between $0.3 and $10 kpc from the Galactic midplane. Strong O vi 1031.93 absorption was detected toward 21 stars, and a reliable 3 upper limit was obtained toward HD 97991. The weaker member of the O vi doublet at 1037.62 Å could be studied toward only six stars because of stellar and interstellar blending problems. The measured logarithmic total column densities vary from 13.65 to 14.57 with hlog Ni ¼ 14:17 AE 0:28 (1 ). The observed columns are reasonably consistent with a patchy exponential O vi distribution with a midplane density of 1:7 Â 10 À8 cm À3 and scale height between 2.3 and 4 kpc. We do not see clear signs of strong high-velocity components in O vi absorption along the Galactic sight lines, which indicates the general absence of high-velocity O vi within 2-5 kpc of the Galactic midplane. This result is in marked contrast to the findings of Sembach et al., who reported high-velocity O vi absorption toward $60% of the complete halo sight lines observed by FUSE. The line centroid velocities of the O vi absorption do not reflect Galactic rotation well. The O vi velocity dispersions range from 33 to 78 km s À1 , with an average of hbi ¼ 45 AE 11 km s À1 (1 ). These values are much higher than the value of $18 km s À1 expected from thermal broadening for gas at T $ 3 Â 10 5 K, the temperature at which O vi is expected to reach its peak abundance in collisional ionization equilibrium. Turbulence, inflow, and outflow must have an effect on the shape of the O vi profiles. Kinematical comparisons of O vi with Ar i reveal that eight of 21 sight lines are closely aligned in LSR velocity (jDV LSR j 5 km s À1 ), while nine of 21 exhibit significant velocity differences (jDV LSR j ! 15 km s À1 ). This dual behavior may indicate the presence of two different types of O vi-bearing environments toward the Galactic sight lines. The correlation between the H i and O vi intermediate-velocity absorption is poor. We could identify the known H i intermediate-velocity components in the Ar i absorption but not in the O vi absorption in most cases. Comparison of O vi with other highly ionized species suggests that the high ions are produced primarily by cooling hot gas in the Galactic fountain flow and that turbulent mixing also has a significant contribution. The role of turbulent mixing varies from negligible to dominant. It is most important toward sight lines that sample supernova remnants like Loops I and IV. The average N(C iv)/N(O vi) ratios for the nearby halo (this work) and complete halo (Savage et al.) are similar ($0.6), but the dispersion is larger in the sample of nearby halo sight lines. We are able to show that the O vi enhancement toward the Galactic center region that was observed in the FUSE survey of complete halo sight lines (Savage et al.) is likely associated with processes occurring near the Galactic center by comparing the observations toward the ...

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Observational Evidence of Supershell Blowout in GS 018−04+44: The Scutum Supershell

Cited by 27 publications

References 47 publications

A Sino-Germanλ6 cm polarization survey of the Galactic plane

A Sino-Germanλ6 cm polarization survey of the Galactic plane

The origin of massive O-type field stars

Highly Ionized Gas in the Galactic Halo: AFUSESurvey of OviAbsorption toward 22 Halo Stars

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