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

The distance to the SNR CTB109 deduced from its environment

We conducted a study of the environment around the supernova remnant CTB109. We found that the SNR is part of a large complex of HII regions extending over an area of 400 pc along the Galactic plane at a distance of about 3 kpc at the closer edge of the Perseus spiral arm. At this distance CTB109 has a diameter of about 24 pc. We demonstrated that including spiral shocks in the distance estimation is an ultimate requirement to determine reliable distances to objects located in the Perseus arm. The most likely explanation for the high concentration of HII regions and SNRs is that the star formation in this part of the Perseus arm is triggered by the spiral shock.Comment: 6 pages, 6 figures. accepted for publication in the Astrophysical Journa

The Supernova Remnant CTB104A : Magnetic Field Structure and Interaction with the Environment

We present new, high resolution 1420 and 408 MHz continuum images and HI and 12CO (J=1-0) spectral line maps of the diffuse supernova remnant CTB104A (G93.7-0.3). Analysis of the complex continuum emission reveals no significant spectral index variations across the remnant. Three prominences around CTB104A are found to be related to the SNR, while one extension to the east is identified as an HII region associated with a background molecular shell. Small scale polarization and rotation measure (RM) structures are turbulent in nature, but we find a well-ordered RM gradient across the remnant, extending from southeast to northwest. This gradient does not agree with the direction of the global Galactic magnetic field, but does agree with a large-scale RM anomaly inferred from rotation measure data by Cleg et al. (1992). We show that the observed morphology of CTB104A is consistent with expansion in a uniform magnetic field, and this is supported by the observed RM distribution. By modeling the RM gradient with a simple compression model we have determined the magnetic field strength within the remnant as Bo ~ 2.3 micro G. We have identified signatures of the interaction of CTB104A with the surrounding neutral material, and determined its distance, from the kinematics of the HI structure encompassing the radio emission, as 1.5 kpc. We also observed clear breaks in the HI shell that correspond well to the positions of two of the prominences, indicating regions where hot gas is escaping from the interior of the SNR.Comment: 7 pages, Latex with aastex and emulateapj5, 12 figures, ApJ accepte

Distance of three Supernova Remnants from HI line observations in a complex region: G114.3+0.3, G116.5+1.1, and CTB 1 (G116.9+0.2)

We present new radio continuum and HI images towards the supernova remnants (SNRs) G114.3+0.3, G116.5+1.1, and G116.9+0.2 (CTB 1) taken from the Canadian Galactic Plane Survey (CGPS). We discuss the dynamics of their HI environment and a possible relationship of these SNRs with each other. We discovered patches of HI emission surrounding G114.3+0.3 indicating a location in the Local arm at a distance of about 700 pc in contrast to previous publications which proposed a Perseus arm location. The other two SNRs have radial velocities of -17 km/s (G116.5+1.1) and -27 km/s (CTB 1) according to related HI. However, the structure of the HI and its dynamics in velocity space suggest a possible relation between them, placing both remnants at a distance of about 1.6 kpc. CTB 1 appears to be embedded in an HI feature which is moving as a whole towards us with a velocity of about 10 km/s. Furthermore, the off-centered location of CTB 1 in a large HI bubble indicates that the so-called breakout region of the remnant is in fact due to its expansion towards the low density interior of this bubble. We believe that the progenitor star of CTB 1 was an early B or O-type star shaping its environment with a strong stellar wind in which case it exploded in a Ib or Ic event.Comment: 16 pages, 9 figures, accepted for publication in The Astrophysical Journa

A large atomic hydrogen shell in the outer Galaxy: SNR or stellar wind bubble?

We report the detection of a ring like HI structure toward l=90.0, b=2.8 with a velocity of v_LSR=-99 km/s. This velocity implies a distance of d=13 kpc, corresponding to a Galactocentric radius of R_gal=15 kpc. The l-v_LSR diagram implies an expansion velocity of v_exp ~ 15 km/s for the shell. The structure has an oblate, irregular shell-like appearance which surrounds weak infrared emission as seen in the 60 micrometer IRAS data. At a distance of 13 kpc the size of the object is about 110 x 220 pc and placed 500 pc above the Galactic plane with a mass of 1e5 solar mass. An expanding shell with such a high mass and diameter cannot be explained by a single supernova explosion or by a single stellar wind bubble. We interpret the structure as a relic of a distant stellar activity region powered by the joint action of strong stellar winds from early type stars and supernova explosions.Comment: Accepted for publication by The Astrophysical Journal, 5 Pages, 4 Figure

The Boomerang: a crushed and re-born PWN?

We present new high radio frequency observations of the Boomerang pulsar wind nebula (PWN) made with the Effelsberg 100-m radio telescope. A comparison with low frequency data from the Canadian Galactic Plane Survey (CGPS; Taylor et al. 2003) reveals a change of the nebula's emission structure with frequency caused by a radial steepening of the radio spectrum above 5 GHz. We also find evidence that the reverse shock of the initial supernova shock wave has driven away or crushed the original PWN which might explain why the current nebula around the pulsar has such a low radio luminosity.Peer reviewed: YesNRC publication: Ye