Discovery of a new faint radio SNR G108.2-0.6

Foster

et al. 2017

A&A

Context. More than 90% of the known Milky Way supernova remnants (SNRs) are within 5• of the Galactic plane. The discovery of the new high-latitude SNR G181.1+9.5 will give us the opportunity to learn more about the environment and magnetic field at the interface between disk and halo of our Galaxy. Aims. We present the discovery of SNR G181.1+9.5, a new high-latitude SNR, serendipitously discovered in an ongoing survey of the Galactic anti-centre High-Velocity Cloud complex, observed with the DRAO Synthesis Telescope in the 21 cm radio continuum and H i spectral line.Methods. We use radio continuum observations (including the linearly polarized component) at 1420 MHz (observed with the DRAO ST) and 4850 MHz (observed with the Effelsberg 100-m radio telescope) to map G181.1+9.5 and determine its nature as a SNR. High-resolution 21 cm H i line observations and H i emission and absorption spectra reveal the physical characteristics of its local interstellar environment. Finally, we estimate the basic physical parameters of G181.1+9.5 using models for highly-evolved SNRs. Results. G181.1+9.5 has a circular shell-like morphology with a radius of about 16 pc at a distance of 1.5 kpc some 250 pc above the mid-plane. The radio observations reveal highly linearly polarized emission with a non-thermal spectrum. Archival ROSAT X-ray data reveal high-energy emission from the interior of G181.1+9.5 indicative of the presence of shock-heated ejecta. The SNR is in the advanced radiative phase of SNR evolution, expanding into the HVC inter-cloud medium with a density of n HI ≈ 1 cm −3 . Basic physical attributes of G181.1+9.5 calculated with radiative SNR models show an upper-limit age of 16 000 yr, a swept-up mass of more than 300 M , and an ambient density in agreement with that estimated from H i observations. Conclusions. G181.1+9.5 shows all characteristics of a typical mature shell-type SNR, but its observed faintness is unusual and requires further study.

Section: Introductionmentioning

confidence: 99%

G181.1+9.5, a new high-latitude low-surface brightness supernova remnant

Kothes

Foster

et al. 2017

A&A

“…The Canadian Galactic Plane Survey (CGPS, Taylor et al 2003) has portrayed the outer Galactic plane with excellent sensitivity and fidelity to extended emission in radio continuum and HI. These qualities have led to the discovery of 13 supernova remnants (SNRs) over the past 12 years (Kothes et al 2001;Kothes 2003;Kothes et al 2005;Tian et al 2007;Gerbrandt et al 2013).…”

Section: Introductionmentioning

confidence: 99%

G141.2+5.0, a New Pulsar Wind Nebula Discovered in the Cygnus Arm of the Milky Way

Kothes¹,

Sun

et al. 2014

ApJ

Self Cite

We report the discovery of the new pulsar wind nebula (PWN) G141.2+5.0 in data observed with the Dominion Radio Astrophysical Observatory's Synthesis Telescope at 1420 MHz. The new PWN has a diameter of about 3.5 ′ , which translates at a distance of 4.0 kpc to a spatial extent of about 4 pc. It displays a radio spectral index of α ≈ −0.7, similar to the PWN G76.9+1.1. G141.2+5.0 is highly polarized up to 40 % with an average of 15 % in the 1420 MHz data. It is located in the centre of a small spherical HI bubble, which is expanding at a velocity of 6 km s −1 . The bubble's systemic velocity is −53 km s −1 and could be the result of the progenitor star's mass loss or the shell-type SNR created by the same supernova explosion in a highly advanced stage. The systemic velocity of the bubble shares the velocity of H I associated with the Cygnus spiral arm, which is seen across the 2nd and 3rd quadrants and an active star-forming arm immediately beyond the Perseus arm. A kinematical distance of 4±0.5 kpc is found for G141.2+5.0, similar to the optical distance of the Cygnus arm (3.8±1.1 kpc). G141.2+5.0 represents the first radio PWN discovered in 17 years and the first SNR discovered in the Cygnus spiral arm, which is in stark contrast with the Perseus arm's overwhelming population of shell-type remnants.

“…The Canadian Galactic Plane Survey (CGPS, Taylor et al, 2003) is the original such survey, and probes the ionized, neutral, and magneto-ionic ISM over unprecedented spatial dynamic range. Since 2001 this dataset has enabled the discovery of 7 new SNRs in the 1 st and 2 nd quadrants of longitude (Kothes et al, 2001;Kothes, 2003;Kothes et al, 2005;Tian et al, 2007;Kerton et al, 2007), and allowed new insights into the SNR population in our Galaxy. In this paper we add two of the faintest-known SNRs to the list of catalogued remnants in our Galaxy.…”

Section: Introductionmentioning

confidence: 99%

Two radio supernova remnants discovered in the outer Galaxy

Foster

Cooper

et al. 2013

A&A

Self Cite

Context. New and existing large-scale radio surveys of the Milky Way at centimetre wavelengths can play an important role in uncovering the hundreds of expected but missing supernova remnants in the Galaxy's interstellar medium. We report on the discovery of two supernova remnants (SNRs) designated G152.4−2.1 and G190.9−2.2, using Canadian Galactic Plane Survey data. Aims. The aims of this paper are, first, to present evidence that favours the classification of both sources as SNRs, and, second, to describe basic parameters (integrated flux density, spectrum, and polarization) as well as properties (morphology, line-of-sight velocity, distance and physical size) to facilitate and motivate future observations. Methods. Spectral and polarization parameters are derived from multiwavelength data from existing radio surveys carried out at wavelengths between 6 and 92 cm. In particular for the source G152.4−2.1 we also use new observations at 11 cm done with the Effelsberg 100 m telescope. The interstellar medium around the discovered sources is analyzed using 1-arcmin line data from neutral hydrogen (H i) and 45-arcsec 12 CO(J = 1 → 0).Results. G152.4−2.1 is a barrel shaped SNR with two opposed radio-bright polarized flanks on the north and south. The remnant, which is elongated along the Galactic plane is evolving in a more-or-less uniform medium. G190.9−2.2 is also a shell-type remnant with east and west halves elongated perpendicular to the plane, and is evolving within a low-density region bounded by dense neutral hydrogen in the north and south, and molecular ( 12 CO) clouds in the east and west. The integrated radio continuum spectral indices are −0.65 ± 0.05 and −0.66 ± 0.05 for G152.4−2.1 and G190.9−2.2 respectively. Both SNRs are approximately 1 kpc distant, with G152.4−2.1 being larger (32 × 30 pc in diameter) than G190.9−2.2 (18 × 16 pc). These two remnants are the lowest surface brightness SNRs yet catalogued at Σ 1 GHz < ∼ 5 × 10 −23 W m −2 Hz −1 sr −1 .