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1.
The Fermi γ-ray space telescope reported the observation of several Galactic supernova remnants recently, with the γ-ray spectra well described by hadronic pp collisions. The possible neutrino emissions from these Fermi detected supernova remnants are discussed in this work, assuming the hadronic origin of the γ-ray emission. The muon event rates induced by the neutrinos from these supernova remnants on typical km3 neutrino telescopes, such as the IceCube and the KM3NeT, are calculated. The results show that for most of these supernova remnants the neutrino signals are too weak to be detected by the on-going or up-coming neutrino experiment. Only for the TeV bright sources RX J1713.7-3946 and possibly W28 the neutrino signals can be comparable with the atmospheric background in the TeV region, if the protons can be accelerated to very high energies. The northern hemisphere based neutrino telescope might detect the neutrinos from these two sources.  相似文献   

2.
The spatial distributions of pulsars with ages of less than 106 years and more than 106 years are shown to be quite different. The spatial distributions of pulsars with ages of less than 106 years and of the remnants of supernova outbursts are essentially the same. They lie near the galactic plane in a thin zone of width 400 pc. The overwhelming majority of pulsars with ages exceeding 106 years lie outside this zone. These facts suggest a genetic relationship between pulsars and supernova remnants. The spatial distribution of pulsars with different emission periods also supports this point.  相似文献   

3.
Very high energy (VHE) γ‐ray observations have proven to be very successful in localizing Galactic acceleration sites of VHE particles. Observations of shell‐type supernova remnants have confirmed that particles are accelerated to VHE energies in supernova blast waves; the interpretation of the γ‐ray data in terms of hadronic or leptonic particle components in these objects relies nevertheless strongly on input from X‐ray observations. The largest identified Galactic VHE source class consists of pulsar wind nebulae, as detected in X‐rays. Many of the remaining VHE sources remain however unidentified until now. With X‐ray observations of these enigmatic “dark” objects one hopes to solve the following questions: What is the astrophysical nature of these sources? Are they predominantly electron or hadron accelerators? And what is their contribution to the overall cosmic ray energy budget? The paper aims to provide an overview over the identification status of the Galactic VHE source population. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

4.
Interplanetary scintillation observations of eleven supernova remnants and the pulsar J1939+2134, around which the existence of a supernova remnant remains obscure, were carried out with the largest in the world decameter radio telescope UTR-2 at 20, 25 and 30 MHz to determine if any of them contain compact radio sources with the angular size θ<5″. The sample included the young Galactic remnants and the other powerful SNRs. The interplanetary scintillations of the compact radio source in the Crab Nebula associated with the well-known pulsar J0534+2200 and the pulsar J1939+2134 were observed. Apart from the Crab Nebula, we have not detected a compact radio source in supernova remnants with the angular size θ<5″ and the flux density more than 10 Jy. The observations do not confirm the existence of the low frequency compact source in Cassiopeia A that has remained controversial.  相似文献   

5.
A sample of eight small-diameter radio sources has been selected from the Molonglo Galactic Plane Survey (MGPS) as candidates for young Galactic supernova remnants. The sources have been identified in the IRAS and Midcourse Space Experiment infrared data bases and imaged in the H107α radio recombination line (RRL) using the Australia Telescope Compact Array (ATCA). Seven of the sources display high ratios of infrared-to-radio-continuum flux density and/or detectable RRLs and are almost certainly H ii regions. One source (G282.8−1.2) is identified as a possible new young Galactic supernova remnant, based on its relatively weak infrared emission, steep radio spectrum, and possible X-ray emission. The adopted method for distinguishing thermal and non-thermal Galactic radio sources seems promising and could be fruitfully applied to more than 100 small-diameter sources listed in the MGPS.  相似文献   

6.
We present MERLIN neutral hydrogen absorption measurements against supernova remnants in the central starburst region of M82 with an angular resolution of ∼ 0.4 arcsec. We detect H  I absorption or set significant upper limits against 33 supernova remnants from which we have been able to deduce column densities. Hence, using these measurements, we are able to probe the neutral hydrogen distribution and dynamics of the interstellar medium in M82 along 33 lines of sight on linear scales of order 1 pc.   Our results show column densities ranging from <1.6 to >30 × 1021 atom cm−2 with the highest values seen towards the edge of the 250-pc 'ring'. The absorption velocities show a gradient of 7.3 ± 4 km s−1 arcsec−1, consistent with rotation parameters of this 'ring' inferred from other measurements. The absorption velocities against individual remnants show deviations of typically 30 km s−1 from simple solid body rotation, and a number show multiple velocity absorption features. Although some of these deviations may be the result of the remnants being embedded at different depths within the neutral gas, the velocities cannot be explained by a simple rotating ring.  相似文献   

7.
The 13.7-m millimeter-wave radio telescope of Purple Mountain Observatory operates at 3200-m above the sea level near Delingha, Qinghai Province, China. Equipped with a superconducting SIS receiver, the telescope is used in the millimeter-wave band ranging from 85 to 115 GHz. An upgrade procedure is reported here which includes a superconducting SIS receiver, a new phase-locked local oscillator, a dedicated multi-line backend system, and a new control system based on industrial computer with PCI bus. With the dedicated multi-line backend system, the CO and isotopic lines around 110 GHz are obtained simultaneously. In recent years, scientific activities with this telescope have been focused on studies of Galactic molecular clouds and star formation regions, including surveys of molecular lines from IRAS sources and large-scale map of molecular clouds. Other programs include studies of the circumstellar envelope of late-type stars and interaction of Galactic supernova remnants with dense molecular gas.  相似文献   

8.
We have used the European VLBI Network (EVN) at 18 cm to study five of the more compact radio sources in the starburst galaxy M82. The angular resolution of the observations is 15 mas, corresponding to 0.2 pc at the distance of M82. The observations reveal shells ranging in diameter from 40 to 90 mas (0.6 to 1.4 pc), although the strongest source (41.95+575) is only marginally resolved by these measurements (∼20×10 mas2).
We have found clear evidence for expansion in one of the shell sources (43.31+592) by re-analysing, in wide-field mode, EVN data taken in 1986. Between 1986 and 1997 this source has increased its diameter by 13.6±2 mas, corresponding to an average expansion velocity of 9850±1500 km s−1. If we assume that the remnant is in free expansion, this is consistent with a supernova event in the early 1960s. Hence this remnant is almost certainly younger than the strongest, most compact source (41.95+575) which was known to be present in the 1960s. 41.95+575 shows no clear evidence for expansion (<4000 km s−1), consistent with a greater age; this is further evidence of its anomalous status. Comparison of the EVN images with earlier MERLIN data is also consistent with expansion in at least two more of the sources. We discuss the flux density variability of the compact sources in M82 and conclude that, with the exception of 41.95+575 and two transient sources, there is little evidence for significant changes in flux density of most of the remnants since the early 1980s.  相似文献   

9.
Supernova remnants are beautiful astronomical objects that are also of high scientific interest, because they provide insights into supernova explosion mechanisms, and because they are the likely sources of Galactic cosmic rays. X-ray observations are an important means to study these objects. And in particular the advances made in X-ray imaging spectroscopy over the last two decades has greatly increased our knowledge about supernova remnants. It has made it possible to map the products of fresh nucleosynthesis, and resulted in the identification of regions near shock fronts that emit X-ray synchrotron radiation. Since X-ray synchrotron radiation requires 10–100 TeV electrons, which lose their energies rapidly, the study of X-ray synchrotron radiation has revealed those regions where active and rapid particle acceleration is taking place.  相似文献   

10.
In this paper, we present high-energy neutrino spectra from 21 Galactic supernova remnants (SNRs), derived from gamma-ray measurements in the GeV–TeV range. We find that only the strongest sources, i.e. G40.5-0.5 in the north and Vela Junior in the south could be detected as single point sources by IceCube or KM3NeT, respectively. For the first time, it is also possible to derive a diffuse signal by applying the observed correlation between gamma-ray emission and radio signal. Radio data from 234 supernova remnants listed in Green’s catalog are used to show that the total diffuse neutrino flux is approximately a factor of 2.5 higher compared to the sources that are resolved so far. We show that the signal at above 10 TeV energies can actually become comparable to the diffuse neutrino flux component from interactions in the interstellar medium. Recently, the IceCube collaboration announced the detection of a first diffuse signal of astrophysical high-energy neutrinos. Directional information cannot unambiguously reveal the nature of the sources at this point due to low statistics. A number of events come from close to the Galactic center and one of the main questions is whether at least a part of the signal can be of Galactic nature. In this paper, we show that the diffuse flux from well-resolved SNRs is at least a factor of 20 below the observed flux.  相似文献   

11.
The origin of cosmic rays is one of the key questions in high-energy astrophysics. Supernovae have been always considered as the dominant sources of cosmic rays below the energy spectrum knee. Multi-wavelength observations indeed show that supernova remnants are capable for accelerating particles into sub-PeV (1015 eV) energies. Diffusive shock acceleration is considered as one of the most efficient acceleration mechanisms of astrophysical high-energy particles, which may just operate effectively in the large-scale shocks of supernova remnants. Recently, a series of high-precision ground and space experiments have greatly promoted the study of cosmic rays and supernova remnants. New observational features challenge the classical acceleration model by diffusive shock and the application to the scenario of supernova remnants for the origin of Galactic cosmic rays, and have deepened our understanding to the cosmic high-energy phenomena. In combination with the time evolution of radiation energy spectrum of supernova remnants, a time-dependent particle acceleration model is established, which can not only explain the anomalies in cosmic-ray distributions around 200 GV, but also naturally form the cosmic-ray spectrum knee, even extend the contribution of supernova particle acceleration to cosmic ray flux up to the spectrum ankle. This model predicts that the high-energy particle transport behavior is dominated by the turbulent convection, which needs to be verified by future observations and plasma numerical simulations relevant to the particle transport.  相似文献   

12.
Three supernova remnants (SNR) have been mapped in the galaxy M33 with the Very Large Array* (VLA) at 20 cm. The angular resolution is ∼1.3 arcsec or ∼4 pc at a distance of 600 kpc and the rms noise is ∼0.04 mJy /beam. One of the radio sources shows evidence for a shell structure with a size of ∼15 pc, confirming the SNR nature of this source. The second object is extended and may well be a thick-shell SNR of size ∼12 pc. The third object is a small, presumably young SNR with a size of ∼4 pc.  相似文献   

13.
宇宙线的起源是高能天体物理的核心问题之一.一直以来,超新星爆发被认为是能谱膝区以下宇宙线的主要来源.多波段观测表明,超新星遗迹有能力加速带电粒子至亚PeV (10~(15)eV)能量.扩散激波加速被认为是最有效的天体高能粒子加速机制之一,而超新星遗迹的大尺度激波正好为这一机制提供平台.近年来,一系列较高精度的地面和空间实验极大地推动了对宇宙线以及超新星遗迹的研究.新的观测事实挑战着传统的扩散激波加速模型以及其在银河系宇宙线超新星遗迹起源学说上的应用,深化了人们对宇宙高能现象的认识.结合超新星遗迹辐射能谱的时间演化特性,构建的时间依赖的超新星遗迹粒子加速模型,不仅能够解释200 GV附近宇宙线的能谱反常,还自然地形成能谱膝区,甚至可以将超新星遗迹粒子加速对宇宙线能谱的贡献延伸至踝区.该模型预期超新星遗迹中粒子的输运行为表现为湍流扩散,这需要未来的观测以及与粒子输运相关的等离子体数值模拟工作来进一步验证.  相似文献   

14.
This is the initial paper in a series presenting the first optical detections and subsequent follow-up spectroscopy of known southern Galactic supernova remnants (SNRs) previously discovered in the radio. These new detections come from the Anglo-Australian Observatory (AAO)/United Kingdom Schmidt Telescope Hα survey of the southern Galactic plane which has opened up fresh opportunities to study Galactic remnants. Here, we present the first optical imaging and follow-up spectra of Galactic SNR G279.0+1.1 where a series of 14 small-scale fragmented groups of Hα filaments have been discovered in a     area centred on G279.0+1.1. Individually they are somewhat inconspicuous but collectively they are completely enclosed within the overall radio contours of this known SNR. Three of these filamentary groupings are particularly prominent and optical spectra have been obtained across two of them. Their morphological structure and spectral characteristics are typical of optically detected SNR filaments. A very strong [S  ii ] emission relative to Hα has been detected with  [S  ii ]/Hα > 0.7  and 1.1, confirming strong, shock-heated emission. This is sufficient to classify these filaments in the likely SNR domain and therefore indicating a direct connection with the radio remnant. Other typical SNR emission lines such as [O  ii ] at 3727 Å, Hβ, [O  iii ] at 4959 and 5007 Å, Hα and [N  ii ] at 6548 and 6584 Å were also detected, lending strong support to an SNR origin of these optical filaments. The value and insights that these optical data can provide for known remnants are discussed along with their relevance to the Galactic nitrogen abundance. A serendipitous discovery of an adjacent H  ii region is also briefly described.  相似文献   

15.
We have developed a method of searching for the connections between the isolated radio pulsars and supernova remnants, based on the analysis of their kinematic characteristics. We investigate fairly young (τ ch ≲ 106 yr) radio pulsars with known proper motions and estimated distances (dispersion measures), and supernova remnants located no more than 1–2 kpc away from them. Using a standard empirical radial velocity distribution, we have constructed 100–200 thousand trajectories for each of these pulsars, tracing back their possible motion in the Galactic gravitational field on a time-scale of a few million years. The probabilities of their close encounters with the SNRs at epochs consistent with the age of the pulsar are analyzed. When these probabilities exceed considerably their reference values, obtained by assuming a purely random encounter between the objects, we conclude that the pulsars may have originated in the SNRs under consideration. Out of eight preselected pairs of pulsar-SNR association candidates, two pairs, J 1829-1751 / G16.2-2.7 and J 1833-0827 / G24.7-0.6 may have a common origin with a high probability.  相似文献   

16.
This paper represents the updated empirical Galactic andextragalactic Σ-D relations (relations between the surface brightness Σ and the diameter D) for supernova remnants(SNRs), with checking the connection of the main Galactic radio loops (Loop I, II, III and IV) with these relations. We present results which suggest, once again, that the radio loops may have an SNR origin. The updated relations for old SNRs have been measured to have slopes, β ≈ 2 in log-log space. The best Σ-D relations for M31 and M33 galaxies were derived and these relations are shown to be flatter (β ≲2) than those for Galactic SNRs alone. A Σ-D relation with168 reliable calibrators (both Galactic and extragalactic) is derived. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

17.
Observations of the starburst galaxy, M82, have been made with a 20-station global very long-baseline interferometry (VLBI) array at λ 18 cm. Maps are presented of the brightest young supernova remnants (SNR) in M82 and the wide-field mapping techniques used in making images over a field of view of ∼1 arcmin with 3-milliarcsecond resolution are discussed. A limit has been placed on the power-law deceleration of the young supernova remnant (SNR) 43.31+592 with an index greater than 0.73±0.11 from observations with the European VLBI Network. Using the global array we have resolved compact knots of radio emission in the source which, with future global observations, will enable better constraints to be placed on the expansion parameters of this SNR.
The latest global observations have also provided high-resolution images of the most compact radio source in M82, 41.95+575. We determine an upper limit to the radial expansion rate along the major axis of 2000 km s−1. However, the new images also show structure resembling that of collimated ejection which brings into question the previous explanation of the source as being a result of the confinement of a supernova by a high-density circumstellar medium.
It is apparent that we are now able to image the brightest supernova remnants in M82 with a linear scale which allows direct comparison with galactic SNR such as Cassiopeia A.  相似文献   

18.
The dependences of various parameters for S-and C-type supernova remnants (SNRs) on their diameters are investigated. Only SNRs with D≤40 pc that expand initially within H II regions and, subsequently, in dense media are considered. The expansion velocities and thermal electron densities of these SNRs were found to decrease with increasing diameter, on average, as D ?1 and D ?0.5, respectively. H II regions hamper the detection of SNRs; this effect is particularly pronounced in regions with 270°≤1≤300° and 330°≤1≤360°. The X-ray luminosities of SNRs born in dense media increase by an order of magnitude when their diameters reach ～30 pc. After the SNR diameters reach ～40 pc, their radio and X-ray luminosities decrease sharply.  相似文献   

19.
The antiproton flux measured by PAMELA experiment might have originated from Galactic sources of cosmic rays. These antiprotons are expected to be produced in the interactions of cosmic ray protons and nuclei with cold protons. Gamma rays are also produced in similar interactions inside some of the cosmic accelerators. We consider a few nearby supernova remnants observed by Fermi LAT. Many of them are associated with molecular clouds. Gamma rays have been detected from these sources which most likely originate in decay of neutral pions produced in hadronic interactions. The observed gamma ray fluxes from these SNRs are used to find out their contributions to the observed diffuse cosmic ray antiproton flux near the earth.  相似文献   

20.
Based on a large volume of statistical data it is shown that the spatial distributions of radio pulsars in the galaxy with characteristic ages T ≤ 10 6 years and T > 106 years differ significantly. The overwhelming majority of the pulsars with T ≤ 10 6 years lie within a narrow band of width 400 pc around the galactic plane. A large portion of the pulsars with T > 106 years is concentrated outside this zone. In the case of younger pulsars, a larger fraction of them lies within the confines of the above mentioned zone. It is also shown that pulsars with T ≤ 10 6 years and the remnants of supernova explosions have essentially the same spatial distribution. These facts support the existence of a relationship between pulsars and supernova remnants, as well as the acquisition of high spatial velocities by pulsars during their birth. __________ Translated from Astrofizika, Vol. 49, No. 1, pp. 103–110 (February 2006).  相似文献   

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