Supernova Blast Wave Research Articles

Material mixing in pulsar wind nebulae of massive runaway stars

Abstract In this study we quantitatively examine the manner pulsar wind, supernova ejecta and defunct stellar wind materials distribute and melt together into plerions. We performed 2.5D MHD simulations of the entire evolution of their stellar surroundings and different scenarios are explored, whether the star dies as a red supergiant and Wolf-Rayet supernova progenitors, and whether it moved with velocity $20\, \rm km\, \rm s^{-1}$ or $40\, \rm km\, \rm s^{-1}$ through the ISM. Within the post-explosion, early $10\, \rm kyr$, the H-burning-products rich red supergiant wind only mixes by $\le 20~{{\%}}$, due to its dense circumstellar medium filling the progenitor’s bow shock trail, still unaffected by the supernova blastwave. Wolf-Rayet materials, enhanced in C, N, O elements, distribute circularly for the $35\, \rm M_\odot$ star moving at $20\, \rm km\, \rm s^{-1}$ and oblongly at higher velocities, mixing efficiently up to 80%. Supernova ejecta, filled with Mg, Si, Ca, Ti and Fe, remain spherical for longer times at $20\, \rm km\, \rm s^{-1}$ but form complex patterns at higher progenitor speeds due to earlier interaction with the bow shock, in which they mix more efficiently. The pulsar wind mixing is more efficient for Wolf-Rayet (25%) than red supergiant progenitors (20%). This work reveals that the past evolution of massive stars and their circumstellar environments critically shapes the internal distribution of chemical elements on plerionic supernova remnants, and, therefore, governs the origin of the various emission mechanisms at work therein. This is essential for interpreting multi-frequency observations of atomic and molecular spectral lines, such as in optical, infrared, and soft X-rays.

Pulsar-wind nebulae meeting the circumstellar media of their progenitors

A significative fraction of high-mass stars sail away through the interstellar medium of the galaxies. Once they evolved and died via a core-collapse supernova, a magnetised, rotating neutron star (a pulsar) is usually left over. The immediate surroundings of the pulsar is the pulsar wind, which forms a nebula whose morphology is shaped by the supernova ejecta and channelled into the circumstellar medium of the progenitor star in the pre-supernova time. Irregular pulsar-wind nebulae display a large variety of radio appearances, screened by their interacting supernova blast wave, or harbour asymmetric up–down emission. Here, we present a series of 2.5-dimensional (2 dimensions for the scalar quantities plus a toroidal component for the vectors) black non-relativistic magneto-hydrodynamical simulations exploring the evolution of the pulsar-wind nebulae generated by a red supergiant and a Wolf-Rayet massive supernova progenitor, moving with Mach number $M=1$ and $M=2$ into the warm phase of the Galactic plane. black In such a simplified approach, the progenitor's direction of motion, the local ambient medium magnetic field, and the progenitor and pulsar axis of rotation, are all aligned; this restricted our study to peculiar pulsar-wind nebula of high-equatorial-energy flux. We find that the reverberation of the termination shock of the pulsar-wind nebulae, when sufficiently embedded into its dead stellar surroundings and interacting with the supernova ejecta, is asymmetric and differs greatly as a function of the past circumstellar evolution of its progenitor, which reflects into their projected radio synchrotron emission. This mechanism is particularly at work in the context of remnants involving slowly moving or very massive stars. We find that the mixing of material in plerionic core-collapse supernova remnants is strongly affected by the asymmetric reverberation in their pulsar-wind nebulae.

Studying the role of supernova remnants as cosmic ray PeVatron with LHAASO observations

It is commonly believed that galactic cosmic rays are produced in supernova remnants (SNRs) and accelerated via a diffusive shock acceleration (DSA) mechanism in supernova blast waves driven by expanding SNRs. The latest theoretical advancement of the diffusive shock acceleration hypothesis in SNRs shows that cosmic rays may be accelerated up to the knee energy of the observed cosmic ray spectrum under the amplified magnetic field scenario. There is, however, no empirical evidence to support SNRs as sources of hadrons with energies larger than a few tens of TeV. Very recently, LHAASO observatory reported the very high-energy gamma ray emission between TeV to PeV energy range from two SNRs, Cassiopeia A and IC 443. Above 25 TeV energies, non-detection of gamma-ray flux by LHAASO yields a strong upper limit. In this work, we investigate the implications of the acceleration of cosmic ray protons in the SNR on energetic gamma rays produced in the hadronic interaction of cosmic rays with ambient matter. Our findings imply that when we consider the highest attainable energy of cosmic ray protons in the SNRs to be about 100 TeV, the observed gamma-ray spectra from the two SNRs can be described consistently. Therefore, we conclude that the Cassiopia A and IC 443 SNRs are unlikely to be cosmic ray PeVatrons.

Bell Instability–mediated Diffusive Shock Acceleration at Supernova Blast Wave Shock Propagating in the Interstellar Medium

Supernova blast wave shock is a very important site of cosmic-ray acceleration. However, the detailed physical process of acceleration, in particular, nonlinear interplay between cosmic-ray streaming and magnetic field amplification, has not been studied under a realistic environment. In this paper, using a unique and novel numerical method, we study cosmic-ray acceleration at supernova blast wave shock propagating in the interstellar medium with well-resolved magnetic field amplification by nonresonant hybrid instability (or Bell instability). We find that the magnetic field is mildly amplified under typical interstellar medium conditions that leads to maximum cosmic-ray energy ≃30 TeV for supernova remnants with age ≃1000 yr consistent with gamma-ray observations. The strength of the amplified magnetic field does not reach the so-called saturation level because the cosmic-ray electric current toward the shock upstream has a finite spatial extent, by which Bell instability cannot experience many e-folding times.

From total destruction to complete survival: dust processing at different evolutionary stages in the supernova remnant Cassiopeia A

ABSTRACT The expanding ejecta of supernova remnants (SNRs) are believed to form dust in dense clumps of gas. Before the dust can be expelled into the interstellar medium and contribute to the interstellar dust budget, it has to survive the reverse shock that is generated through the interaction of the preceding supernova blast wave with the surrounding medium. The conditions under which the reverse shock hits the clumps change with remnant age and define the dust survival rate. To study the dust destruction in the SNR Cassiopeia A, we conduct magnetohydrodynamical simulations of the evolution of a supernova blast wave and of the reverse shock. In a second step, we use these evolving conditions to model clumps that are disrupted by the reverse shock at different remnant ages. Finally, we compute the amount of dust that is destroyed by the impact of the reverse shock. We find that most of the dust in the SNR is hit by the reverse shock within the first 350 yr after the SN explosion. While the dust destruction in the first 200 yr is almost complete, we expect greater dust survival rates at later times and almost total survival for clumps that are first impacted at ages beyond 1000 yr. Integrated over the entire evolution of the SNR, the dust mass shows the lowest survival fraction (17 per cent) for the smallest grains (1 nm) and the highest survival fraction (28 per cent) for the largest grains (1000 nm).

Direct Formation of Massive Black Holes via Dynamical Collapse in Metal-enriched Merging Galaxies at z ∼ 10: Fully Cosmological Simulations

We present the results of the first fully cosmological hydrodynamical simulations studying the merger-driven model for massive black hole (BH) seed formation via direct collapse. Using the zoom-in technique as well as particle splitting, we achieve a final spatial resolution of 2 pc. We show that the major merger of two massive galaxies at redshift z ∼ 8 results in the formation of a nuclear supermassive disk (SMD) of only 4 pc in radius, owing to a prodigious gas inflow sustained at 100–1000 M ⊙ yr−1. The core of the merger remnant is metal-rich, well above solar abundance, and the SMD reaches a gaseous mass of 3 × 108 M ⊙ in less than a million years after the merger, despite a concurrent prominent nuclear starburst. Dynamical heating as gas falls into the deepest part of the potential well, and heating and stirring by supernova blastwaves, generate a turbulent multiphase interstellar medium, with a gas velocity dispersion exceeding 100 km s−1. As a result, only moderate fragmentation occurs in the inner 10–20 pc, despite the temperature falling below 1000 K. The SMD is Jeans-unstable as well as bar-unstable and will collapse further adiabatically, becoming warm and ionized. We show that the SMD, following inevitable contraction, will become general-relativistic-unstable and directly form a supermassive BH of mass in the range 106–108 M ⊙, essentially skipping the stage of BH seed formation. These results confirm that mergers between the most massive galaxies at z ∼ 8–10 can naturally explain the rapid emergence of bright high-redshift quasars.

A Spatially Resolved X-Ray Polarization Map of the Vela Pulsar Wind Nebula

In this paper, we present a full spatially resolved polarization map for the Vela pulsar wind nebula (PWN) observed by IXPE. By employing effective background discrimination techniques, our results show a remarkably high degree of local polarization in the outskirt region, exceeding 60% (55%) with a probability of 95% (99%), which approaches the upper limit predicted by the synchrotron emission mechanism. The high degree of polarization suggests that the turbulent magnetic energy is at most 33% of the ordered one. In addition, the X-ray polarization map exhibits a toroidal magnetic field pattern that is consistent with the field revealed by radio observations across the entire nebula. This consistency reveals that the observed X-ray and radio emissions are radiated by electrons from the same magnetic field. Different from the Crab PWN, the consistency observed in the Vela PWN may be attributed to the interaction between the reverse shock of the supernova blast wave and the PWN, which leads to a displacement between the synchrotron-cooled nebula and the fresh nebula close to the pulsar. These findings deepen our understanding of the structure and evolution of the Vela PWN and the magnetohydrodynamic interaction in PWNe.

Simulated non-thermal emission of the supernova remnant G1.9 + 0.3

ABSTRACT Supernova remnants are the nebular leftover of defunct stellar environments, resulting from the interaction between a supernova blastwave and the circumstellar medium shaped by the progenitor throughout its life. They display a large variety of non-spherical morphologies such as ears that shine non-thermally. We have modelled the structure and the non-thermal emission of the supernova remnant G1.9 + 0.3 through 3D magnetohydrodynamic numerical simulations. We propose that the peculiar ear-shaped morphology of this supernova remnant results from the interaction of its blast wave with a magnetized circumstellar medium, which was previously asymmetrically shaped by the past stellar wind emanating from the progenitor star or its stellar companion. We created synthetic non-thermal radio and X-ray maps from our simulated remnant structure, which are in qualitative agreement with observations, forming ears on the polar directions. Our synthetic map study explains the discrepancies between the measured non-thermal radio and X-ray surface brightness distributions assuming that the inverse Compton process produces the observed X-ray emission.

SALT spectroscopy of the HMXB associated with the LMC supernova remnant MCSNR J0513−6724

ABSTRACT We report the results of optical échelle spectroscopy with the Southern African Large Telescope (SALT) of the mass donor star BSDL923 in the neutron star (NS) high-mass X-ray binary XMMU J051342.6−672412 associated with the LMC supernova remnant (SNR) MCSNR J0513−6724. We found that BSDL923 is a B0.7 III star with double peaked emission lines originating in a circumbinary disc-like structure. Modelling with the stellar atmosphere code fastwind was used to derive Teff = 27 000 K, log g = 3.22, $v\sin i\approx 100\, {\rm \, km\, s^{-1}}$ and $\log (L_*/\rm \, L_\odot)=5.46$ of BSDL923, as well as to show that the surface of this star is polluted with α-elements from the supernova ejecta. We found also that the NS is orbiting BSDL923 in an eccentric orbit with the orbital period of 1.280 d and the semimajor axis of $17\pm 3 \,R_\odot$, which is less than or equal to the radius of BSDL923 of $25\pm 5 \,R_\odot$. We speculate that the NS is embedded in the atmosphere of BSDL923 either because it was kicked at birth towards this star or because of inflation of BSDL923 caused by the energy input from the supernova blast wave. Using long-slit spectroscopy with SALT, we searched for possible signs of the SNR shell in the 2D spectrum, but did not find them. This lack of detection is consistent with the young age of this SNR, implying that it is still in the adiabatic phase.

Supernova Dust Evolution Probed by Deep-sea 60Fe Time History

There is a wealth of data on live, undecayed 60Fe (t 1/2 = 2.6 Myr) in deep-sea deposits, the lunar regolith, cosmic rays, and Antarctic snow, which is interpreted as originating from the recent explosions of at least two near-Earth supernovae. We use the 60Fe profiles in deep-sea sediments to estimate the timescale of supernova debris deposition beginning ∼3 Myr ago. The available data admits a variety of different profile functions, but in all cases the best-fit 60Fe pulse durations are >1.6 Myr when all the data is combined. This timescale far exceeds the ≲0.1 Myr pulse that would be expected if 60Fe was entrained in the supernova blast wave plasma. We interpret the long signal duration as evidence that 60Fe arrives in the form of supernova dust, whose dynamics are separate from but coupled to the evolution of the blast plasma. In this framework, the >1.6 Myr is that for dust stopping due to drag forces. This scenario is consistent with the simulations in Fry et al. (2020), where the dust is magnetically trapped in supernova remnants and thereby confined around regions of the remnant dominated by supernova ejects, where magnetic fields are low. This picture fits naturally with models of cosmic-ray injection of refractory elements as sputtered supernova dust grains and implies that the recent 60Fe detections in cosmic rays complement the fragments of grains that survived to arrive on the Earth and Moon. Finally, we present possible tests for this scenario.

Cosmic-Ray Acceleration in Supernova Remnants

Supernova Remnants (SNRs) are generally believed to produce the cosmic rays in our Galaxy due to the powerful supernova blast waves generated by expanding SNRs. In contrast to the leptonic cosmic-ray component that is clearly seen by the SNR emission in a wide wavelength range, from radio to high-energy γ-ray, the hadronic cosmic-ray component can be detected only by very high energy γ-ray emission. Galactic SNRs of various ages have been intensively studied at very high energies. Among them are the shell-type SNRs: Tycho’s SNR, Cas A, IC 443, γCygni SNR, G166.0+4.3. The results of investigations of listed SNRs obtained in observations at 800 GeV–100 TeV energies by SHALON telescope are presented with spectral energy distribution and emission maps compared with experimental data from the wide energy range, from radio to high-energy gamma-rays. The TeV emission maps of supernova remnants obtained by SHALON are overlaid with ones viewed in radio- frequencies and X-rays to reveal SNR’s essential features which can lead to the effective generation of cosmic rays. The presented experimental data from high and very high energies are considered together with theoretical predictions to test the cosmic ray origin in these objects.

Relativistic Supernova Blast Waves Exhibit Properties of Gravitational Lenses and the Hubble Constant

Relativistic Supernova Blast Waves Exhibit Properties of Gravitational Lenses and the Hubble Constant

Mid-infrared imaging of Supernova 1987A

ABSTRACT At a distance of 50 kpc, Supernova 1987A is an ideal target to study how a young supernova (SN) evolves in time. Its equatorial ring, filled with material expelled from the progenitor star about 20 000 yr ago, has been engulfed with SN blast waves. Shocks heat dust grains in the ring, emitting their energy at mid-infrared (IR) wavelengths We present ground-based 10–18 μm monitoring of the ring of SN 1987A from day 6067 to 12814 at a resolution of 0.5 arcsec, together with SOFIA photometry at 10–30 μm. The IR images in the 2000’s (day 6067–7242) showed that the shocks first began brightening the east side of the ring. Later, our mid-IR images from 2017 to 2022 (day 10952–12714) show that dust emission is now fading in the east, while it has brightened on the west side of the ring. Because dust grains are heated in the shocked plasma, which can emit X-rays, the IR and X-ray brightness ratio represent shock diagnostics. Until 2007 the IR to X-ray brightness ratio remained constant over time, and during this time shocks seemed to be largely influencing the east side of the ring. However, since then, the IR to X-ray ratio has been declining, due to increased X-ray brightness. Whether the declining IR brightness is because of dust grains being destroyed or being cooled in the post-shock regions will require more detailed modelling.

Rectangular core-collapse supernova remnants: application to Puppis A

ABSTRACT Core-collapse supernova remnants are the gaseous nebulae of galactic interstellar media (ISM) formed after the explosive death of massive stars. Their morphology and emission properties depend both on the surrounding circumstellar structure shaped by the stellar wind–ISM interaction of the progenitor star and on the local conditions of the ambient medium. In the warm phase of the Galactic plane ($n\approx 1\, \rm cm^{-3}$, $T\approx 8000\, \rm K$), an organized magnetic field of strength $7\, \mu \rm G$ has profound consequences on the morphology of the wind bubble of massive stars at rest. In this paper, we show through 2.5D magnetohydrodynamical simulations, in the context of a Wolf–Rayet-evolving $35\, \rm M_{\odot }$ star, that it affects the development of its supernova remnant. When the supernova remnant reaches its middle age ($15\!-\!20\, \rm kyr$), it adopts a tubular shape that results from the interaction between the isotropic supernova ejecta and the anisotropic, magnetized, shocked stellar progenitor bubble into which the supernova blast wave expands. Our calculations for non-thermal emission, i.e. radio synchrotron and inverse-Compton radiation, reveal that such supernova remnants can, due to projection effects, appear as rectangular objects in certain cases. This mechanism for shaping a supernova remnant is similar to the bipolar and elliptical planetary nebula production by wind–wind interaction in the low-mass regime of stellar evolution. If such a rectangular core-collapse supernova remnant is created, the progenitor star must not have been a runaway star. We propose that such a mechanism is at work in the shaping of the asymmetric core-collapse supernova remnant Puppis A.

Kinematics, structure and abundances of supernova remnant 0540-69.3

Aims. Our goal is to investigate the structure, elemental abundances, physical conditions, and the immediate surroundings of supernova remnant 0540-69.3 in the Large Magellanic Cloud. Methods. Imaging in [O III] and spectroscopic studies through various slits were carried out using European Souther Observatory’s Very Large and New Technology Telescopes. Densities, temperatures, and abundances were estimated applying nebular analysis for various parts of the remnant. Results. Several new spectral lines are identified, both from ejecta embedded in the pulsar-wind nebula, and in interstellar clouds shocked by the supernova blast wave. For the filaments in the pulsar-wind nebula, all lines are redshifted by 440 ± 80 km s−1 with respect to the rest frame of the host galaxy, and a 3D representation of the [O III] emission displays a symmetry axis of ring-like structures which could indicate that the pulsar shares the same general redshift as the central supernova ejecta. We note that [O II], [S II], [Ar III], and Hβ share a common more compact structure than [O III], and possibly [Ne III]. The average [O III] temperature for the filaments in the pulsar-wind nebula is 23 500 ± 1800 K, and the electron density derived from [S II] is typically ∼ 103 cm−3. By mass, the relative elemental abundances of the shocked ejecta in the pulsar-wind nebula are O : Ne : S : Ar ≈ 1 : 0.07 : 0.10 : 0.02, consistent with explosion models of 13 − 20 M⊙ progenitors, and similar to that of SN 1987A, as is also the explosive mixing of hydrogen and helium into the center. From Hβ and He Iλ5876, the mass ratio of He/H in the center is estimated to be in excess of ∼0.8. The rapid cooling of the shocked ejecta could potentially cause variations in the relative abundances if the ejecta are not fully microscopically mixed, and this is highlighted for S/O for the period 1989–2006. Also, [O III] is seen in presumably freely coasting photoionized ejecta outside the pulsar-wind nebula at inferred velocities out to well above 2000 km s−1, and in projection, [O III] is seen out to ∼10″ from the pulsar. This was used to estimate that the pulsar age is ≈1200 years. The freely coasting [O III]-emitting ejecta have a strictly nonspherical distribution, and their mass is estimated to be ∼0.12 M⊙. A possible outer boundary of oxygen-rich ejecta is seen in [O II] λλ3726,3729 at ∼2000 − 2100 km s−1. Four filaments of a shocked interstellar medium are identified, and there is a wide range in the degree of ionization of iron, from Fe+ to Fe13+. One filament belongs to a region also observed in X-rays, and another one has a redshift of 85 ± 30 km s−1 relative to the host. From this we estimate that the electron density of the [O III]-emitting gas is ∼ 103 cm−3, and that the line of the most highly ionized ion, [Fe XIV] λ5303, comes from an evaporation zone in connection with the radiatively cooled gas emitting, for example, [O III], and not from immediately behind the blast wave. We do not find evidence for nitrogen-enriched ejecta in the southwestern part of the remnant, as was previously suggested. Emission in this region is instead from a severely reddened H II-region.

The contribution by luminous blue variable stars to the dust content of the Magellanic Clouds

Context. Previous studies have concluded that low- and intermediate-mass stars cannot account for the interstellar dust yield in the Magellanic Clouds inferred from far-infrared and sub-millimetre observations. Aims. Luminous blue variable stars (LBVs) form dust as a result of episodic, violent mass loss. To investigate their contribution as dust producers in the Magellanic Clouds, we analyse 31 confirmed and candidate LBVs from a recent census. Methods. We built a maximally complete multi-wavelength dataset of these sources from archival space telescope images and catalogues from near-infrared to millimetre wavelengths. We also present new Very Large Telescope VISIR observations of three sources in the Large Magellanic Cloud (LMC). We review the LBV classification on the basis of the infrared spectral energy distribution. To derive characteristic dust parameters, we fitted the photometry resulting from a stacking analysis, which consists of co-adding images of the same wavelength band of several targets to improve the signal-to-noise. For comparison we also stacked the images of low- and intermediate-mass evolved stars in the LMC. Results. We find four classes of sources: (1) LBVs showing mid-infrared dust emission plus near-infrared free-free emission from an ionised stellar wind (Class 1a) or only mid-infrared dust emission (Class 1b); (2) LBVs with a near-infrared excess due to free-free emission only (Class 2); (3) objects with an sgB[e] classification in the literature, displaying a distinctive hot dust component; and (4) objects with no detected stellar winds and no circumstellar matter in their SEDs. From the stacking analysis of the 18 Class 1 and 2 objects in the LMC, we derived an integrated dust mass of 0.11−0.03+0.06 M⊙. This is two orders of magnitude larger than the value inferred from stacking 1342 extreme-asymptotic giant branch stars. The dust mass of individual LBVs does not correlate with the stellar parameters, possibly suggesting that the dust production mechanism is independent of the initial stellar mass or that the stars have different evolutionary histories. The total dust yield from LBVs over the age of the LMC is ∼104 − 105 M⊙. The one order of magnitude uncertainty is mainly due to uncertainties of the LBV population, star formation history, and initial mass function. Conclusions. LBVs are potentially the second most important source of dust in normal galaxies. The role of dust destruction in LBV nebulae by a possible subsequent supernova (SN) blast wave has yet to be determined. Recent theoretical developments in the field of dust processing by SN shocks highlight the potential survival of dust grains from the pre-existing circumstellar nebula.

Effects of Turbulence in the Circumnuclear Disk

Abstract A circumnuclear disk (CND) of molecular gas occupies the central few parsecs of the Galactic Center. It is likely subject to turbulent disruptions from violent events in its surrounding environment, but the effect of such perturbations has not yet been investigated in detail. Here we perform 3D, N-body/smoothed particle hydrodynamic simulations with an adapted general turbulence driving method to investigate the CND’s structural evolution, in particular its reaction to varied scales of injected turbulence. We find that, because of shear flow in the disk, transient arcs of gas (streams) naturally arise when turbulence is driven on large scales (up to ∼4 pc), as might occur when a supernova blast wave encounters the CND. Because energetic events arise naturally and often in the central parsecs of our Galaxy, this result suggests that the transient structures that characterize the CND do not imply that the CND itself is a transient structure. We also note that features similar to the density concentrations, or clumps, detailed in the literature emerge when we account for the observed orientation of the disk and for the spatial resolution of observations. As such, clumps could be an artifact of observational limitations.

Modeling the mixed-morphology supernova remnant IC 443

Context. The morphology and the distribution of material observed in supernova remnants (SNRs) reflect the interaction of the supernova (SN) blast wave with the ambient environment, the physical processes associated with the SN explosion, and the internal structure of the progenitor star. IC 443 is a mixed-morphology (MM) SNR located in a quite complex environment: it interacts with a molecular cloud in the northwestern and southeastern areas and with an atomic cloud in the northeast. Aims. In this work, we aim to investigate the origin of the complex morphology and multi-thermal X-ray emission observed in SNR IC 443 through the study of the effect of the inhomogeneous ambient medium in shaping its observed structure and an exploration of the main parameters characterizing the remnant. Methods. We developed a 3D hydrodynamic (HD) model for IC 443, which describes the interaction of the SNR with the environment, parametrized in agreement with the results of the multi-wavelength data analysis. We performed an ample exploration of the parameter space describing the initial blast wave and the environment, including the mass of the ejecta, the energy and position of the explosion, as well as the density, structure, and geometry of the surrounding clouds. From the simulations, we synthesized the X-ray emission maps and spectra and compared them with actual X-ray data collected by XMM-Newton. Results. Our model explains the origin of the complex X-ray morphology of SNR IC 443 in a natural way, with the ability to reproduce, for the first time, most of the observed features, including the centrally-peaked X-ray morphology (characteristic of MM SNRs) when considering the origin of the explosion at the position where the pulsar wind nebula CXOU J061705.3+222127 was at the time of the explosion. In the model that best reproduces the observations, the mass of the ejecta and the energy of the explosion are ~7 M⊙ and ~1 × 1051 erg, respectively. From the exploration of the parameter space, we find that the density of the clouds is n > 300 cm−3 and that the age of SNR IC 443 is ~8000 yr. Conclusions. The observed inhomogeneous ambient medium is the main property responsible for the complex structure and the X-ray morphology of SNR IC 443, resulting in a very asymmetric distribution of the ejecta due to the off-centered location of the explosion inside the cavity formed by the clouds. It can be argued that the centrally peaked morphology (typical of MM SNRs) is a natural consequence of the interaction with the complex environment. A combination of high resolution X-ray observations and accurate 3D HD modeling is needed to confirm whether this scenario is applicable to other MM SNRs.

The Center of Expansion and Age of the Oxygen-rich Supernova Remnant 1E 0102.2-7219

Abstract We present new proper-motion measurements of optically emitting oxygen-rich knots of supernova remnant 1E 0102.2-7219 (E0102), which are used to estimate the remnant’s center of expansion and age. Four epochs of high-resolution Hubble Space Telescope images spanning 19 yr were retrieved and analyzed. We found a robust center of expansion of α = 1h04m02.ˢ48 and δ = −72°01′53.″92 (J2000) with 1σ uncertainty of 1.″77 using 45 knots from images obtained with the Advanced Camera for Surveys using the F475W filter in 2003 and 2013 having the highest signal-to-noise ratio. We also estimate an upper limit explosion age of 1738 ± 175 yr by selecting the knots with the highest proper motions and these knots are assumed to be the least decelerated. We find evidence of an asymmetry in the proper motions of the knots as a function of position angle. We conclude that these asymmetries were most likely caused by interaction between E0102's original supernova blast wave and an inhomogeneous surrounding environment, as opposed to intrinsic explosion asymmetry. The observed nonhomologous expansion suggests that the use of a free expansion model inaccurately offsets the center of expansion and leads to an overestimated explosion age. We discuss our findings as they compare to previous age and center of expansion estimates of E0102, as well as their relevance to a recently identified candidate central compact object.

LYRA I: Simulating the multi-phase ISM of a dwarf galaxy with variable energy supernovae from individual stars

Abstract We introduce the LYRA project, a new high resolution galaxy formation model built within the framework of the cosmological hydro-dynamical moving mesh code arepo. The model resolves the multi-phase interstellar medium down to 10 K. It forms individual stars sampled from the initial mass function (IMF), and tracks their lifetimes and death pathways individually. Single supernova (SN) blast waves with variable energy are followed within the hydrodynamic calculation to interact with the surrounding interstellar medium (ISM). In this paper, we present the methods and apply the model to a 1010 M⊙ isolated halo. We demonstrate that the majority of supernovae are Sedov-resolved at our fiducial gas mass resolution of 4 M⊙. We show that our SN feedback prescription self-consistently produces a hot phase within the ISM that drives significant outflows, reduces the gas density and suppresses star formation. Clustered SN play a major role in enhancing the effectiveness of feedback, because the majority of explosions occur in low density material. Accounting for variable SN energy allows the feedback to respond directly to stellar evolution. We show that the ISM is sensitive to the spatially distributed energy deposition. It strongly affects the outflow behaviour, reducing the mass loading by a factor of 2 − 3, thus allowing the galaxy to retain a higher fraction of mass and metals. LYRA makes it possible to use a comprehensive multi-physics ISM model directly in cosmological (zoom) simulations of dwarf and higher mass galaxies.