[ITAL]Chandra[/ITAL] Detection of the Forward and Reverse Shocks in Cassiopeia A

Large amounts of dust (> 10 8 M ⊙ ) have recently been discovered in high redshifts quasars 1,2 and galaxies 3−5 , corresponding to a time when the Universe was less than one-tenth of its present age. The stellar winds produced by stars in the late stages of their evolution (on the asymptotic giant branch of the Hertzsprung-Russell diagram) are though to be the main source of dust in galaxies, but they cannot produce that dust on a short-enough timescale 6 (< 1 Gyr) to explain the results in the high-redshift galaxies.Supernova explosions of massive stars (type II) are also a potential source, with models predicting 0.2-4 M ⊙ of dust 7−10 . As massive stars evolve rapidly, on timescales of a few Myr, these supernovae could be responsible for the high-redshift dust. Observations 11−13 of supernova remnants in the Milky Way, however, have hitherto revealed only 10 −7 − 10 −3 M ⊙ of dust each, which is insufficient to explain the high-redshift data. Here we report the detection of ∼ 2 − 4 M ⊙ of cold dust in the youngest known Galactic remnant, Cassiopeia A. This observation implies that supernovae are at least as important as stellar winds in producing dust in our Galaxy and would have been the dominant source of dust at high redshifts.Over the past three decades, many searches for dust in supernova remnants (SNR) have been made in the mid and far-infrared (6-100µm). Remnants must be studied when they are young, before they have swept up large masses of interstellar material which makes it difficult to distinguish dust formed in the ejecta from that present in the ISM prior to the explosion. The handful of Galactic remnants which are both young and close enough (Cas A, Kepler and Tycho) have been studied with the Infrared Astronomical Satellite (IRAS) and the Infrared Space Observatory (ISO), but although dust at 100-200 K has been detected, the dust mass deduced is only 10 −7 − 10 −3 M ⊙ , many orders of magnitude lower than the solar mass quantities predicted. 11−13 The formation of dust in the recent supernova 1987A has been implied indirectly from the fading of the silicate line and increase in 10µm emission, 14 although the quantity is heavily dependant on the assumptions made 1

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“…The 850µm image is presented in Fig. 1 and shows a ring-like morphology, similar to the X-ray and radio images 18,19 .…”

supporting

confidence: 61%

“…4 indicate the position of the forward and reverse shocks as determined from Chandra X-ray data. 18 Most of the dust appears to be contained between the two, where the gas density as traced by the X-rays is greatest. We fitted a two-temperature grey body SED to the synchrotron corrected IR/submm fluxes (Fig.…”

mentioning

confidence: 99%

Type II supernovae as a significant source of interstellar dust

Dunne

Eales

Ivison

et al. 2003

Nature

252

323

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“…′ 58 ± 0. ′ 16 (Gotthelf et al 2001), which at a distance of 3.4 +0.3 −0.1 kpc (Reed et al 1995), correspond to 2.52 ± 0.2 pc and 1.58 ± 0.16 pc respectively. Since the amount of mass within the radius of the forward shock has to be ∼8M ⊙ (Vink et al 1996), we can determine the RSG terminal wind velocity by using the following relation between the mass loss rate, wind velocity and forward shock radius:…”

Section: The Adopted Stellar Evolution Modelmentioning

confidence: 97%

The hydrodynamics of the supernova remnant Cassiopeia A

Veelen

Langer

Vink

et al. 2009

A&A

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Aims. There are large differences in the proposed progenitor models for the Cas A SNR. One of these differences is the presence or absence of a Wolf-Rayet (WR) phase of the progenitor star. The mass loss history of the progenitor star strongly affects the shape of the Supernova remnant (SNR). In this paper we investigate whether the progenitor star of Cas A had a WR phase or not and how long it may have lasted.Methods. We performed two-dimensional multi-species hydrodynamical simulations of the CSM around the progenitor star for several WR life times, each followed by the interaction of the supernova ejecta with the CSM. We then looked at the influence of the length of the WR phase and compared the results of the simulations with the observations of Cas A. Results. The difference in the structure of the CSM, for models with different WR life times, has a strong impact on the resulting SNR. With an increasing WR life time the reverse shock velocity of the SNR decreases and the range of observed velocities in the shocked material increases. Furthermore, if a WR phase occurs, the remainders of the WR shell will be visible in the resulting SNR. Conclusions. Comparing our results with the observations suggests that the progenitor star of Cas A did not have a WR phase. We also find that the quasi-stationary flocculi (QSF) in Cas A are not consistent with the clumps from a WR shell that have been shocked and accelerated by the interaction with the SN ejecta. We can also conclude that for a SN explosion taking place in a CSM that is shaped by the wind during a short (≤ 15000 yr) WR phase, the clumps from the WR shell will be visible inside the SNR.

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“…The largest and strongest secondary shock in the system is the reverse shock (RS) that propagates through the ejecta. High-resolution radio and X-ray observations support the notion that particle acceleration can also occur at RS (Gotthelf et al 2001;Rho et al 2002;DeLaney et al 2002;Sasaki et al 2006;Helder & Vink 2008), but only recently has this possibility been considered in theoretical calculations (Zirakashvili & Aharonian 2010;Zirakashvili & Ptuskin 2012;Telezhinsky et al 2012a,b), which relax the restricting assumptions about the magnetic field (MF) in the RS region (e.g. Ellison et al 2005).…”

Section: Introductionmentioning

confidence: 99%

Acceleration of cosmic rays by young core-collapse supernova remnants

Telezhinsky

Dwarkadas

Pohl

2013

A&A

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Context. Supernova remnants (SNRs) are thought to be the primary candidates for the sources of Galactic cosmic rays. According to the diffusive shock acceleration theory, SNR shocks produce a power-law spectrum with an index of s = 2, perhaps nonlinearly modified to harder spectra at high energy. Observations of SNRs often indicate particle spectra that are softer than that and show features not expected from classical theory. Known drawbacks of the standard approach are the assumption that SNRs evolve in a uniform environment, and that the reverse shock does not accelerate particles. Relaxing these assumptions increases the complexity of the problem, because one needs reliable hydrodynamical data for the plasma flow as well as good estimates for the magnetic field (MF) at the reverse shock. Aims. We show that these two factors are especially important when modeling young core-collapse SNRs that evolve in a complicated circumstellar medium shaped by the winds of progenitor stars. Methods. We used high-resolution numerical simulations for the hydrodynamical evolution of the SNR. Instead of parametrizations of the MF profiles inside the SNR, we followed the advection of the frozen-in MF inside the SNR, and thus obtained the B-field value at all locations, in particular at the reverse shock. To model cosmic-ray acceleration we solved the cosmic-ray transport equation in test-particle approximation. Results. We find that the complex plasma-flow profiles of core-collapse SNRs significantly modify the particle spectra. Additionally, the reverse shock strongly affects the emission spectra and the surface brightness.

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[ITAL]Chandra[/ITAL] Detection of the Forward and Reverse Shocks in Cassiopeia A

Cited by 227 publications

References 22 publications

Type II supernovae as a significant source of interstellar dust

Type II supernovae as a significant source of interstellar dust

The hydrodynamics of the supernova remnant Cassiopeia A

Acceleration of cosmic rays by young core-collapse supernova remnants

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