G106.3+2.7: A Supernova Remnant in a Late Stage of Evolution

We report on observations of the candidate supernova remnant (SNR) G106.3+2.7 with the Dominion Radio Astrophysical Observatory's Synthesis Telescope in the continuum at both 408 and 1420 MHz and in the 21 cm line of neutral hydrogen. The general morphology of the object and its spectral index (α ≈ 0.57 ± 0.04, where Sν ∝ ν-α) confirm it as an SNR. The object consists of two distinct components, the head and the tail. The tail component is of lower surface brightness and has a marginally steeper spectral index than the head component. A deficiency of neutral hydrogen at an LSR velocity of about -105 km s-1 is most likely due to the effect of the SNR, suggesting that the SNR is expanding at a velocity of about 15 km s -1, it is at a kinematic distance of 12 kpc, and its largest angular extent is of the order of 200 pc. These parameters are shown to be consistent with a dynamical model in which the SNR is in a very late stage of its isothermal evolution, where the pressure inside the SNR is approaching the pressure of the ambient interstellar medium. We also describe the H II region Sh 141, which is about 20' north of G106.3+2.7

Multifrequency study of the ring nebula SG 13

We investigate the morphology and kinematics of the interstellar medium in the environs of the open cluster Mrk 50, which includes the Wolf-Rayet star WR 157 and a number of early B-type stars. The analysis was performed using radio continuum images at 408 and 1420 MHz, and H i 21-cm line data taken from the Canadian Galactic Plane Survey, molecular observations of the 12CO (J = 1 → 0) line at 115 GHz from the Five College Radio Astronomy Observatory and available mid- and far-infrared (FIR) observations obtained with the Midcourse Space Experiment and IRAS satellites, respectively. This study allowed the identification of the radio continuum and molecular counterpart of the ring nebula SG 13, while no neutral atomic structure was found to be associated. The nebula is also detected in the images in the mid- and FIR, showing the existence of dust well mixed with the ionized gas. We estimate the main physical parameters of the material linked to the nebula. The interstellar gas distribution in the environs of Mrk 50 is compatible with a stellar wind bubble created by the mass loss from WR 157. The distribution of young stellar object candidates in the region shows that the stellar formation activity may be present in the molecular shell that encircles the ring nebula.Facultad de Ciencias Astronómicas y Geofísica

The SNR G106.3+2.7 and its Pulsar Wind Nebula: relics of triggered star formation in a complex environment

We propose that the pulsar nebula associated with the pulsar J2229+6114 and the supernova remnant (SNR) G106.3+2.7 are the result of the same supernova explosion. The whole structure is located at the edge of an HI bubble with extended regions of molecular gas inside. The radial velocities of both the atomic hydrogen and the molecular material suggest a distance of 800 pc. At this distance the SNR is 14 pc long and 6 pc wide. Apparently the bubble was created by the stellar wind and supernova explosions of a group of stars in its center which also triggered the formation of the progenitor star of G106.3+2.7. The progenitor star exploded at or close to the current position of the pulsar, which is at one end of the SNR rather than at its center. The expanding shock wave of the supernova explosion created a comet shaped supernova remnant by running into dense material and then breaking out into the inner part of the HI bubble. A synchrotron nebula with a shell-like structure (the ``Boomerang'') of length 0.8 pc was created by the pulsar wind interacting with the dense ambient medium. The expanding shock wave created an HI shell of mass 0.4 Msun around this nebula by ionizing the atomic hydrogen in its vicinity.Comment: 10 pages, Latex, with aastex and emulateapj5, 5 figures. ApJ, accepted, scheduled for the v560 n1 p1 Oct 10, 2001 issu

VLA radio continuum and IRAS observations of the ring nebulae around WR 101 and WR 113

We report radio continuum observations at 1465 MHz obtained with the Very Large Array (VLA) in the DnC configuration toward the ring nebulae associated with the stars WR 101 and WR 113, with resolutions of ∼38″ and 30″, respectively. IRAS images of the nebulae with resolutions of about 2′ (90 M⊙, 40 cm-3) are also analyzed. A remarkable resemblance among the optical, infrared, and radio images of these ring nebulae is observed. The VLA data indicate that Anon. WR 101 is thermal in nature. An ionized mass of ≈230 ± 40 M⊙ and electron densities in the range ≈40-55 cm-3 were estimated for Anon. WR 101. The derived ionized masses and electron densities in the inner and outer shells of the nebula related to WR 113 are ≈20 ± 10 M⊙, 180-500 cm-3 and ≈90 M⊙ 40 cm-3, respectively. Based on infrared data at 60 and 100 μm, the derived masses and temperatures for the dust component in the ring nebula around WR 101 are 0.3-1 M⊙ and ≈40 K. The associated masses suggest that the ring nebula related to WR 101 and the outer arc associated with WR 113 consist of swept-up interstellar matter, while the relatively low ionized mass associated with the inner shell of the nebula around WR 113 may contain a nonnegligible contribution of expelled ejecta material. The derived electron densities for the nebula around WR 101 and the inner shell around WR 113 are comparable to electron densities for other W-R ring nebulae. Low filling factors are inferred for both nebulae. The nebulae probably originated during the current W-R phase of the stars.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

VLA radio continuum and IRAS observations of the ring nebulae around WR 101 and WR 113

We report radio continuum observations at 1465 MHz obtained with the Very Large Array (VLA) in the DnC configuration toward the ring nebulae associated with the stars WR 101 and WR 113, with resolutions of ∼38″ and 30″, respectively. IRAS images of the nebulae with resolutions of about 2′ (90 M⊙, 40 cm-3) are also analyzed. A remarkable resemblance among the optical, infrared, and radio images of these ring nebulae is observed. The VLA data indicate that Anon. WR 101 is thermal in nature. An ionized mass of ≈230 ± 40 M⊙ and electron densities in the range ≈40-55 cm-3 were estimated for Anon. WR 101. The derived ionized masses and electron densities in the inner and outer shells of the nebula related to WR 113 are ≈20 ± 10 M⊙, 180-500 cm-3 and ≈90 M⊙ 40 cm-3, respectively. Based on infrared data at 60 and 100 μm, the derived masses and temperatures for the dust component in the ring nebula around WR 101 are 0.3-1 M⊙ and ≈40 K. The associated masses suggest that the ring nebula related to WR 101 and the outer arc associated with WR 113 consist of swept-up interstellar matter, while the relatively low ionized mass associated with the inner shell of the nebula around WR 113 may contain a nonnegligible contribution of expelled ejecta material. The derived electron densities for the nebula around WR 101 and the inner shell around WR 113 are comparable to electron densities for other W-R ring nebulae. Low filling factors are inferred for both nebulae. The nebulae probably originated during the current W-R phase of the stars.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

Triggered star formation in a molecular shell created by a SNR?

We present a study of a new molecular shell, G126.1-0.8-14, using available multiwavelegth Galactic plane surveys and optical Gemini observations. A well defined shell-like structure is observed in the CO(1--0) line emission at (l,b) = (126.1, -0.8), in the velocity range --10.5 to --15.5 km/s. The HI, emission shows a region of low emissivity inside G126.1-0.8-14, while radio continuum observations reveal faint non-thermal emission possibly related to this shell. Optical spectra obtained with Gemini South show the existence of B-type stars likely to be associated with G126.1-0.8-14. An estimate of the stellar wind energy injected by these stars show that they alone can not be able to create such a structure. On the other hand, one supernova explosion would provide enough energy to generate the shell. Using the MSX, IRAS, and WISE Point Source Catalogues we have found about 30 young stellar objects candidates, whose birth could have been triggered by the expansion of G126.1-0.8-14. In this context, Sh2-187 could be a consequence of the action on its surroundings of the most massive (and thus most evolve) of the stars formed by the expanding molecular shell.Comment: 13 pages, 10 figures, accepted in MNRA

The radio and infrared counterparts of the ring nebula around HD 211564

We report the detection of the radio and infrared (IR) counterparts of the ring nebula around the WN3(h) star HD 211564 (WR 152), located to the south-west of the H II region Sh2 132. Using radio continuum data from the Canadian Galactic Plane Survey, we identified the radio counterparts of the two concentric rings, of about 9 and 16 arcmin in radius, related to the star. After applying a filling factor f = 0.05-0.12, electron densities and ionized masses are in the range 10-16 cm-3 and 450-700 M⊙ respectively. The analysis of the H I gas emission distribution allowed the identification of 5900 M⊙ of neutral atomic gas with velocities between -52 and -43 km s-1 probably linked to the nebula. The region of the nebula is almost free of molecular gas. Only four small clumps were detected, with a total molecular mass of 790 M⊙. About 310 M⊙ are related to a small IR shell-like source linked to the inner ring, which is also detected in the MSX band A.AnIRAS young stellar object candidate is detected in coincidence with the shell-like IR source. We suggest that the optical nebula and its neutral counterparts originated from the stellar winds from the Wolf-Rayet star and its massive progenitor, and are evolving in the envelope of a slowly expanding shell centred at (l,b) = (102.30, -0°.50) of about 31 pc in radius. The bubble's energy conversion efficiency is in agreement with recent numerical analysis and with observational results.Facultad de Ciencias Astronómicas y Geofísica

The radio and infrared counterparts of the ring nebula around HD 211564

We report the detection of the radio and infrared (IR) counterparts of the ring nebula around the WN3(h) star HD 211564 (WR 152), located to the south-west of the H II region Sh2 132. Using radio continuum data from the Canadian Galactic Plane Survey, we identified the radio counterparts of the two concentric rings, of about 9 and 16 arcmin in radius, related to the star. After applying a filling factor f = 0.05-0.12, electron densities and ionized masses are in the range 10-16 cm-3 and 450-700 M⊙ respectively. The analysis of the H I gas emission distribution allowed the identification of 5900 M⊙ of neutral atomic gas with velocities between -52 and -43 km s-1 probably linked to the nebula. The region of the nebula is almost free of molecular gas. Only four small clumps were detected, with a total molecular mass of 790 M⊙. About 310 M⊙ are related to a small IR shell-like source linked to the inner ring, which is also detected in the MSX band A.AnIRAS young stellar object candidate is detected in coincidence with the shell-like IR source. We suggest that the optical nebula and its neutral counterparts originated from the stellar winds from the Wolf-Rayet star and its massive progenitor, and are evolving in the envelope of a slowly expanding shell centred at (l,b) = (102.30, -0°.50) of about 31 pc in radius. The bubble's energy conversion efficiency is in agreement with recent numerical analysis and with observational results.Facultad de Ciencias Astronómicas y Geofísica

An HI interstellar bubble linked to the O-type stars BD +24°3866 and BD +25°3952

We investigate the ISM in the vicinity of the O-type stars BD +24°3866 (O8.5II(f)), BD +24°3881 (O6.5III(f)) and BD +24°3952 (O8) based on radio continuum and HI line data obtained with the Synthesis Telescope of the Dominion Radio Astrophysical Observatory (DRAO) with synthesized beams of 1′.5 and 7′ at 1420 and 408 MHz, respectively. High angular resolution IRAS data (HIRES) are also analyzed. BD +24°3866 is found to be located close to the inner border of a slowly expanding shell. The evolved HII region Sh2-88, which is excited by BD +25°3952, appears to be interacting with neutral material in the approaching part of this shell. The whole structure is ata distance of 2.4 kpc and is about 23×15 pc in radius. The total swept up mass is 1300 M⊙. The stellar winds of BD +24°3866 and BD +25°3952, are mainly responsible for shaping the HI structure. An HI expanding shell was also found to be related to the HII region G61.7+0.9. At a kinematic distance of 2.4 kpc, this feature is 10 pc in radius and has neutral and ionized masses of 200 and 135 M⊙, respectively. The present observational data do not allow us to identify a definite interstellar HI feature associated with BD +24°3881. We consider different explanations for this fact.Facultad de Ciencias Astronómicas y GeofísicasInstituto Argentino de Radioastronomí

Ionized gas, molecules and dust in Sh2-132

We analyse the various interstellar components of the H II region Sh2-132. The main stellar source is the double binary system that includes the Wolf–Rayet star WR 153ab. We use radio continuum images at 408 and 1420 MHz, and H I 21-cm line data taken from the Canadian Galactic Plane Survey, molecular observations of the 12CO(1–0) line at 115 GHz from the Five College Radio Astronomy Observatory, and available mid- and far-infrared observations obtained with the MSX and IRAS satellites, respectively. Sh2-132 is composed of two shells showing radio continuum counterparts at both frequencies. The emission is thermal in nature. The estimated rms electron density and ionized mass of the nebula are ne≃ 20 cm−3 and MH II ≃ 1500 M⊙. The distribution of the CO emission shows molecular gas bordering the ionized nebula and interacting with it. The velocities of the molecular gas is in the range −38 to −53 km s−1, similar to the velocity of the ionized gas. The emission at 8.3 μm reveals a ring-like feature of about 15 arcmin that encircles the bright optical regions. This emission is due to the polycyclic aromatic hydrocarbons and marks the location of photodissociation regions. The gas distribution in the environs of Sh2-132 can be explained in a scenario where the massive stars in the region photodissociated, ionized and swept up the dense molecular material from the parental cloud through their strong stellar winds and intense ultraviolet (UV) photon flux.Facultad de Ciencias Astronómicas y Geofísica