High Resolution Spectroscopy of Balmer-Dominated Shocks in the RCW 86, Kepler and SN 1006 Supernova Remnants

We report results from high resolution optical spectroscopy of three non-radiative galactic supernova remnants, RCW 86, Kepler's supernova remnant and SN 1006. We have measured the narrow component H-alpha line widths in Balmer-dominated filaments in RCW 86 and SN 1006, as well as the narrow component width in a Balmer-dominated knot in Kepler's SNR. The narrow component line widths measured in RCW 86 and Kepler's SNR show FWHM of 30-40 km/s, similar to what has been seen in other Balmer-dominated remnants. Of the remnants in our sample, SN 1006 is the fastest shock (~3000 km/s). The narrow component H-alpha and H-beta lines in this remnant have a FWHM of merely 21 km/s. Comparing the narrow component widths measured in our sample with those measured in other remnants shows that the width of the narrow component does not correlate in a simple way with the shock velocity. The implications for the pre-heating mechanism responsible for the observed line widths are discussed.Comment: Accepted by A&

[Fe XIV] and [Fe XI] reveal the forward shock in SNR 1E0102.2-7219

Aims. We study the forward shock in the oxygen-rich young supernova remnant (SNR) 1E0102.2-7219 (1E0102 in short) via optical coronal emission from [Fe XIV] and [Fe XI]: emission lines which offer an alternative method to X-rays to do so. Methods. We have used the Multi-Unit Spectroscopic Explorer (MUSE) optical integral field spectrograph at the Very Large Telescope (VLT) on Cerro Paranal to obtain deep observations of SNR 1E0102 in the Small Magellanic Cloud. Our observations cover the entire extent of the remnant with a seeing limited spatial resolution of 0.7" = 0.2 pc at the distance of 1E 0102. Results. Our MUSE observations unambiguously reveal the presence of [Fe XIV] and [Fe XI] emission in 1E0102. The emission largely arises from a thin, partial ring of filaments surrounding the fast moving O-rich ejecta in the system. The brightest [Fe XIV] and [Fe XI] emission is found along the eastern and north-western sides of 1E0102, where shocks are driven into denser ISM material, while fainter emission along the northern edge reveals the location of the forward shock in lower density gas, possibly the relic stellar wind cavity. Modeling of the eastern shocks and the photoionization precursor surrounding 1E0102, we derive a pre-shock density $n_H$ = (7.4 +-1.5) cm$^{-3}$, and a shock velocity 330 km/s < $v_s$ < 350 km/s.Comment: 4 pages, 4 figures, accepted for publications in A&A as a Letter to the Edito

The pre-shock gas of SN1006 from HST/ACS observations

We derive the pre-shock density and scale length along the line of sight for the collisionless shock from a deep HST image that resolves the H alpha filament in SN1006 and updated model calculations. The very deep ACS high-resolution image of the Balmer line filament in the northwest (NW) quadrant shows that 0.25 < n_0 < le$ 0.4 cm-3 and that the scale along the line of sight is about 2 x 10^{18} cm, while bright features within the filament correspond to ripples with radii of curvature less than 1/10 that size. The derived densities are within the broad range of earlier density estimates, and they agree well with the ionization time scale derived from the Chandra X-ray spectrum of a region just behind the optical filament. This provides a test for widely used models of the X-ray emission from SNR shocks. The scale and amplitude of the ripples are consistent with expectations for a shock propagating though interstellar gas with ~ 20% density fluctuations on parsec scales as expected from studies of interstellar turbulence. One bulge in the filament corresponds to a knot of ejecta overtaking the blast wave, however. The interaction results from the rapid deceleration of the blast wave as it encounters an interstellar cloud.Comment: 16 pages, 6 figures, to appear in Ap

A Half-Megasecond Chandra Observation of the Oxygen-Rich Supernova Remnant G292.0+1.8

We report on our initial analysis of a deep 510 ks observation of the Galactic oxygen-rich supernova remnant (SNR) G292.0+1.8 with the {\it Chandra X-ray Observatory}. Our new {\it Chandra} ACIS-I observation has a larger field of view and an order of magnitude deeper exposure than the previous {\it Chandra} observation, which allows us to cover the entire SNR and to detect new metal-rich ejecta features. We find a highly non-uniform distribution of thermodynamic conditions of the X-ray emitting hot gas that correlates well with the optical [O {\small III}] emission, suggesting the possibility that the originating supernova explosion of G292.0+1.8 was itself asymmetric. We also reveal spectacular substructures of a torus, a jet, and an extended central compact nebula all associated with the embedded pulsar J1124$-$5916.Comment: 10 pages including 1 table and 2 figures (both figures are color), accepted by ApJ Letter

Proper Motions of H-alpha filaments in the Supernova Remnant RCW 86

We present a proper motion study of the eastern shock-region of the supernova remnant RCW 86 (MSH 14-63, G315.4-2.3), based on optical observations carried out with VLT/FORS2 in 2007 and 2010. For both the northeastern and southeastern regions, we measure an average proper motion of H-alpha filaments of 0.10 +/- 0.02 arcsec/yr, corresponding to 1200 +/- 200 km/s at 2.5kpc. There is substantial variation in the derived proper motions, indicating shock velocities ranging from just below 700 km/s to above 2200 km/s. The optical proper motion is lower than the previously measured X-ray proper motion of northeastern region. The new measurements are consistent with the previously measured proton temperature of 2.3 +/- 0.3 keV, assuming no cosmic-ray acceleration. However, within the uncertainties, moderately efficient (< 27 per cent) shock acceleration is still possible. The combination of optical proper motion and proton temperature rule out the possibility that RCW 86 has a distance less than 1.5kpc. The similarity of the proper motions in the northeast and southeast is peculiar, given the different densities and X-ray emission properties of the regions. The northeastern region has lower densities and the X-ray emission is synchrotron dominated, suggesting that the shock velocities should be higher than in the southeastern, thermal X-ray dominated, region. A possible solution is that the H-alpha emitting filaments are biased toward denser regions, with lower shock velocities. Alternatively, in the northeast the shock velocity may have decreased rapidly during the past 200yr, and the X-ray synchrotron emission is an afterglow from a period when the shock velocity was higher.Comment: Accepted for publication in MNRA

MUSE Integral Field Observations of the Oxygen-rich SNR 1E 0102.2-7219

We have observed the oxygen-rich SNR 1E 0102.2-7219 with the integral field spectrograph WiFeS at Siding Spring Observatory and discovered sulfur-rich ejecta for the first time. Follow-up deep DDT observations with MUSE on the VLT (8100 s on source) have led to the additional discovery of fast- moving hydrogen as well as argon-rich and chlorine-rich material. The detection of fast-moving hydrogen knots challenges the interpretation that the progenitor of 1E 0102 was a compact core of a Wolf-Rayet star that had shed its entire envelope. In addition to the detection of hydrogen and the products of oxygen-burning, this unprecedented sharp (0.2" spaxel size at ~0.7" seeing) and deep MUSE view of an oxygen-rich SNR in the Magellanic Clouds reveals further exciting discoveries, including [Fe xiv]{\lambda}5303 and [Fe xi]{\lambda}7892 emission, which we associate with the forward shock. We present this exciting data set and discuss some of its implications for the explosion mechanism and nucleosynthesis of the associated supernova.Comment: 6 pages, 4 figures, IAU331 Symposium Proceeding

Measuring the cosmic ray acceleration efficiency of a supernova remnant

Cosmic rays are the most energetic particles arriving at earth. Although most of them are thought to be accelerated by supernova remnants, the details of the acceleration process and its efficiency are not well determined. Here we show that the pressure induced by cosmic rays exceeds the thermal pressure behind the northeast shock of the supernova remnant RCW 86, where the X-ray emission is dominated by synchrotron radiation from ultra-relativistic electrons. We determined the cosmic-ray content from the thermal Doppler broadening measured with optical spectroscopy, combined with a proper-motion study in X- rays. The measured post-shock proton temperature in combination with the shock velocity does not agree with standard shock heating, implying that >50% of the post-shock pressure is produced by cosmic rays.Comment: Published in Science express, 10 pages, 5 figures and 2 table