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We have obtained the polarization data cube of the supernova remnant (SNR) VRO 42.05.01 at 1240 MHz using the Five-hundred-meter Aperture Spherical Radio Telescope (FAST). Three-dimensional Faraday synthesis is applied to the FAST data to derive the Faraday depth spectrum. The peak Faraday depth map shows a large area of enhanced foreground rotation measure (RM) of ∼60 rad m−2 extending along the remnant's "wing" section, which coincides with a large-scale H i shell at −20 km s−1. The two depolarization patches within the "wing" region with RMs of 97 rad m−2 and 55 rad m−2 coincide with two H i structures in the H i shell. Faraday screen model fitting on the Canadian Galactic Plane Survey 1420 MHz full-scale polarization data reveals a distance of (0.7–0.8) d SNR in front of the SNR with enhanced regular magnetic field there. The highly piled-up magnetic field indicates that the H i shell at −20 km s−1 could originate from an old evolved SNR. [ABSTRACT FROM AUTHOR]

Hadronic γ-ray sources associated with supernova remnants (SNRs) can serve as stopwatches for the escape of cosmic rays from SNRs, which gradually develops from highest-energy particles to lowest-energy particles with time. In this work, we analyze the 13.7 yr Fermi-LAT data to investigate the γ-ray feature in/around the SNR G298.6−0.0 region. With γ-ray spatial analyses, we detect three point-like components. Among them, Src-NE is at the eastern SNR shell, and Src-NW is adjacent to the western edge of this SNR. Src-NE and Src-NW demonstrate spectral breaks at energies around/below 1.8 GeV, suggesting an old SNR age of >10 kyr. We also look into the X-ray emission from the G298.6−0.0 region, with the Chandra-ACIS data. We detected an extended keV source having a centrally filled structure inside the radio shell. The X-ray spectra are well fitted by a model which assumes a collisional ionization equilibrium of the thermal plasma, further supporting an old SNR age. Based on our analyses of the NANTEN CO- and ATCA-Parkes H  i -line data, we determined a kinematic distance of ∼10.1 kpc from us to G298.6−0.0. This distance entails a large physical radius of the SNR of ∼15.5 pc, which is additional evidence for an old age of >10 kyr. Besides this, the CO data cube enables us to three-dimensionally locate the molecular clouds (MCs) which are potentially interacting with SNR G298.6−0.0 and could account for the hadronic γ-rays detected at Src-NE or Src-NW. Furthermore, the multiwavelength observational properties unanimously imply that the SNR–MC interaction occurs mainly in the north-eastern direction. [ABSTRACT FROM AUTHOR]

The investigation of very high energy (VHE) γ‐ray sources by any methods, including mirror Cherenkov telescopes, touches on the problem of the cosmic‐ray origin and, accordingly, the role of the Galaxy in their generation. The SHALON observations have yielded the results on Galactic supernova remnants (SNR) of different ages. Among them are: the shell‐type SNRs Tycho's SNR, Cas A, IC 443, γCygni SNR, G166.0+4.3. For each of SNRs, the observation results are presented with spectral energy distribution by SHALON in comparison with other experiment data and images by SHALON in together with data from X‐ray by Chandra and radio‐data by CGPS. The experimental data presented here have confirmed the prediction of the theory about the hadronic generation mechanism of VHE 800 GeV–100 TeV γ‐rays in Tycho's SNR, Cas A and IC 443, and also the collected experimental data help to make clear the origin of TeV γ‐ray emission in the older SNRs like γCygni SNR and G166.0+4.3. [ABSTRACT FROM AUTHOR]

We present the detections of shocked molecular hydrogen (H2) gas in near- and mid-infrared and broad CO in millimeter from the mixed-morphology supernova remnant (SNR) HB 3 (G132.7+1.3) using the Palomar Wide-field InfraRed Camera, the Spitzer GLIMPSE360 and Wide-field Infrared Survey Explorer (WISE) surveys, and the Heinrich Hertz Submillimeter Telescope. Our near-infrared narrow-band filter H2 2.12 μm images of HB 3 show that both Spitzer Infrared Array Camera and WISE 4.6 μm emission originates from shocked H2 gas. The morphology of H2 exhibits thin filamentary structures and a large scale of interaction sites between the HB 3 and nearby molecular clouds. Half of HB 3, the southern and eastern shell of the SNR, emits H2 in a shape of a butterfly or W, indicating the interaction sites between the SNR and dense molecular clouds. Interestingly, the H2 emitting region in the southeast is also co-spatial to the interacting area between HB 3 and the H ii regions of the W3 complex, where we identified star-forming activity. We further explore the interaction between HB 3 and dense molecular clouds with detections of broad CO(3-2) and CO(2-1) molecular lines from the southern and southeastern shell along the H2 emitting region. The widths of the broad lines are 8–20 km s−1; the detection of such broad lines is unambiguous, dynamic evidence of the interactions between the SNR and clouds. The CO broad lines are from two branches of the bright, southern H2 shell. We apply the Paris–Durham shock model to the CO line profiles, which infer the shock velocities of 20–40 km s−1, relatively low densities of 103–4 cm−3, and strong (>200 μG) magnetic fields. [ABSTRACT FROM AUTHOR]

In the current decade, GeV/TeV gamma-ray observations of several supernova remnants (SNRs) have implied that accelerated particles are escaping from their acceleration sites. However, when and how they escape from the SNR vicinities are yet to be understood. Recent studies have suggested that the particle escape might develop with thermal plasma ages of the SNRs. We present a systematic study on the time evolution of particle escape using thermal X-ray properties and gamma-ray spectra using 38 SNRs associated with GeV/TeV gamma-ray emissions. We conducted spectral fittings on the gamma-ray spectra using exponential cutoff power-law and broken power-law models to estimate the exponential cutoff or the break energies, both of which are indicators of particle escape. Plots of the gamma-ray cutoff/break energies over the plasma ages show similar tendencies to those predicted by analytical/numerical calculations of particle escape under conditions in which a shock is interacting with thin interstellar medium or clouds. The particle escape timescale is estimated as ∼100 kyr from the decreasing trends of the total energy of the confined protons with the plasma age. The large dispersions of the cutoff/break energies in the data may suggest an intrinsic variety of particle escape environments. This might be the cause of the complicated Galactic cosmic ray spectral shape measured on Earth. [ABSTRACT FROM AUTHOR]

Context. The environment of supernova remnants (SNRs) is a key factor in their evolution, particularly at later stages of their existence. Mixed-morphology (MM) SNRs have a peculiar centre-filled X-ray shape that remains enigmatic. It is often assumed that they evolve in very dense environments, and that the X-ray morphology is due to interactions between the SNRs and their surroundings. Aims. We aim to determine whether VRO 42.05.01 is embedded in, and interacting with, a dense molecular environment. We also aim to understand the multi-wavelength emission from the environment of this SNR, and whether the interstellar material can be responsible for the the MM nature of the source, and for its strange radio and optical shape. Methods. We used the IRAM telescope in Pico Veleta, Spain, to search for signs of interaction between the SNR and neighbouring molecular clouds. We observed a region of 26′ × 14′ towards the west of VRO 42.05.01 and a region of 8′ × 4′ towards the north of the remnant in the 12CO J = 1−0, 13CO J = 1−0, and 12CO J = 2−1 transitions with the EMIR receiver. We made maps of the properties of the observed molecular clouds (peak temperatures, central velocities, velocity dispersions), as well as maps of column density along the line of sight, and ratio of the 12CO J = 2−1 to 12CO J = 1−0 transitions. We also analyse archival optical, infrared, and radio spectroscopic data for other hints on the nature of the medium. Results. We do not find conclusive physical proof that the SNR is interacting with the few, clumpy molecular clouds that surround it in the region of our observations, although there is some suggestion of such interaction (in a region outside our map) from infrared emission. We find that there is a velocity gradient in one of the molecular clouds that is consistent with a stellar wind blown by a 12−14 M⊙ progenitor star. We reassess the literature distance to VRO 42.05.01, and propose that it has a local standard of rest velocity of − 6 km s−1, and that it is located 1.0 ± 0.4 kpc away (the earlier distance value was 4.5 ± 1.5 kpc). We find that a dust sheet intersects VRO 42.05.01 and is possibly related to its double shell-shaped morphology. [ABSTRACT FROM AUTHOR]

Context. The Galactic plane is the brightest source of γ rays in the sky. It should also be one of the brightest very-high-energy neutrino sources, if a neutrino flux comparable to the γ-ray flux is produced by the cosmic ray interactions in the interstellar medium. Aims. We explore the detectability of the neutrino flux from the entire Galactic plane or from a part of it with the IceCube neutrino detector. Methods. We calculated the normalization and the spectral index of the neutrino power-law spectrum from different regions of the Galactic plane, based on the observed spectral characteristics of the pion decay γ-ray diffuse emission observed by the Fermi/LAT telescope in the energy band above 100 GeV.We compared the neutrino flux calculated in this way with the sensitivity of IceCube for the detection of extended sources. Results. Assuming a binned extended source analysis method, we find that the only possible evidence of neutrino emission for sources located in the northern hemisphere after 20 years of exposure is from the Cygnus region. For other parts of the Galactic plane even a 20 year exposure with IceCube is not sufficient for the detection. Taking into account marginal significance of the detectable source in the Cygnus region, we find a precise position and size of the source region that optimizes the signal-to-noise ratio for neutrinos. We also calculated the low-energy threshold above which the neutrino signal can be detected with the highest signal-to-noise ratio. This calculation of precise source position, size, and energy range, based on the γ-ray data, can be used to remove the so-called trial factor in the analysis of the real neutrino data of IceCube. We notice that the diffuse neutrino emission from the inner Galactic plane in the southern hemisphere is much brighter. A neutrino detector with characteristics equivalent to IceCube, but placed at the northern hemisphere (such as KM3NeT), would detect several isolated neutrino sources in the Galactic plane with just a five-year exposure at the 5σ level. Their discovery would identify the cosmic ray sources in the Galaxy that have been active during the last 104 years. Conclusions. The detection of the diffuse neutrino emission from cosmic ray interactions in the Galactic disk is challenging, but marginally feasible with a 20 year exposure by IceCube. Dramatically shorter (2-5 yr) exposure times would be required for the Galactic plane signal detection with an IceCube-like neutrino detector in the northern hemisphere. [ABSTRACT FROM AUTHOR]

Context. A growing number of researchers present evidence that the pulsar wind nebula 3C 58 is much older than predicted by its proposed connection to the historical supernova of A.D. 1181. There is also a great diversity of arguments. The strongest of these arguments rely heavily on the assumed distance of 3.2 kpc determined with H i absorption measurements. Aims. This publication aims at determining a more accurate distance for 3C58 and at re-evaluating the arguments for an older age. Methods. I have re-visited the distance determination of 3C 58 based on new H i data from the Canadian Galactic Plane Survey and our recent improvements in the knowledge of the rotation curve of the outer Milky Way Galaxy. I also used newly determined distances to objects in the neighbourhood, which are based on direct measurements by trigonometric parallax. Results. I have derived a new more reliable distance estimate of 2 kpc for 3C 58. This makes the connection between the pulsar wind nebula and the historical event from A.D. 1181 once again much more viable. [ABSTRACT FROM AUTHOR]

The Chandra X-ray Observatory is providing remarkable new views of massive star-forming regions, revealing all stages in the life cycle of high-mass stars and their effects on their surroundings. We present a Chandra tour of several high-mass star-forming regions, highlighting physical processes that characterize the life of a cluster of high-mass stars, from deeply-embedded cores too young to have established an HII region to superbubbles so large that they shape our views of galaxies. Along the way we see that X-ray observations reveal hundreds of stellar sources powering great HII region complexes, suffused by both hard and soft diffuse X-ray structures caused by fast O-star winds thermalized in wind-wind collisions or by termination shocks against the surrounding media. Finally, we examine the effects of the deaths of high-mass stars that remained close to their birthplaces, exploding as supernovae within the superbubbles that these clusters created. We present new X-ray results on W51 IRS2E and 30 Doradus and we introduce new data on Trumpler 14 in Carina and the W3 HII region complexes W3 Main and W3(OH). [ABSTRACT FROM PUBLISHER]

The Synthesis Radio Telescope at the Dominion Radio Astrophysical Observatory is being used to make a long-term study of the relationship between sources of the slowly-varying component at 21-cm wavelength and the active regions with which they are associated. Although the arc-minute angular resolution of the radio telescope is insufficient to map individual active regions, the unique capability of this radio telescope to map the whole solar disc in a single operation makes it useful for identifying and measuring sources of the slowly-varying component, which at this wavelength are largely due to free–free thermal emission from plasma concentrations trapped in active region magnetic fields. The brightness temperatures of the emission are higher in large, complex active regions, suggesting the plasma slab producing the emission is thicker and/or denser in such regions. We find also that the relationship between the brightness temperature and the size and complexity of the host region is a function of the phase of the 10–13-year solar activity cycle. [ABSTRACT FROM AUTHOR]

Focuses on the relation between the surface brightness and the diameter for galactic supernova remnants. Intrinsic and extrinsic properties of remnants; Dependence of radio luminosity and the diameter; Details of calibrator remnants.

By combining the photometric, spectroscopic, and astrometric information of the stars in the sightline of supernova remnants (SNRs), the distances to and the extinctions of 32 Galactic SNRs are investigated. The stellar atmospheric parameters are from the Sloan Digital Sky Survey−DR14/Apache Point Observatory Galaxy Evolution Experiment and Large sky Area Multi-Object fiber Spectroscopic Telescope−DR5/LEGUE spectroscopic surveys. The multiband photometry, from optical to infrared, are collected from the Gaia, APASS, Pan-STARRS1, Two Micron All Sky Survey, and Wide-field Infrared Survey Explorer surveys. With the calibrated Gaia distances of individual stars, the distances to 15 of 32 SNRs are well determined from their produced extinction and association with molecular clouds. The upper limits of distance are derived for three SNRs. The color excess ratios of 32 SNRs are calculated, and their variation with wavebands is fitted by a simple dust model. The inferred dust grain size distribution bifurcates: while the graphite grains have comparable size to the average interstellar medium dust, the silicate grains are generally larger. Along the way, the average extinction law from optical to near-infrared of the Milky Way is derived from the 1.3-million-star sample and found to agree with the CCM89 law with . [ABSTRACT FROM AUTHOR]

Reports on a highly-ordered Faraday-rotation structure of elliptical shape, with its long axis parallel to the plane of the Milky Way galaxy. Detection of magnetic fields which could be involved in the formation of such structures; Location; Possible origin.

Recent hydrodynamical models of supernova remnants (SNRs) demonstrate that their evolution depends heavily on the inhomogeneities of the surrounding medium. As SNRs expand, their morphologies are influenced by the nonuniform and turbulent structure of their environments, as reflected in their radio continuum emission. In this paper, we measure the asymmetries of 96 SNRs in radio continuum images from three surveys of the Galactic plane and compare these results to the SNRs’ radii, which we use as a proxy for their age. We find that larger (older) SNRs are more elliptical/elongated and more mirror asymmetric than smaller (younger) SNRs, though the latter vary in their degrees of asymmetry. This result suggests that SNR shells become more asymmetric as they sweep up the interstellar medium (ISM), as predicted in hydrodynamical models of SNRs expanding in a multiphase or turbulent ISM. [ABSTRACT FROM AUTHOR]