Supernova Remnant Science with AXIS Brian Williams & Hiroya Yamaguchi
Big Picture Questions - How do supernovae dictate the life cycle of elements in the ISM? - What are the progenitors of the various types of supernovae (Type Ia, Type Ib/c, Type II ), and how to they relate to the remnants produced? - How are particles accelerated to extraordinary energies in shock waves? Study of SNRs with AXIS will help answer all these questions
Particulars for AXIS SNR science Should focus on science that cannot be done with ATHENA (i.e., requires high spatial resolution). Some could be done with Chandra, but at extraordinary cost. Overlap with Lynx OK? Important AXIS qualities for SNRs, ranked in order of preference: 1a) effective area, particularly at 6 kev 1b) spatial resolution (ideally < 0.5, and better is always better) 2) low background 3) field of view. Nice, but not required. 10 sufficient, 15 plenty
4 areas to highlight today (not in any particular order, and by no means complete) - Mapping of supernova ejecta products - Small-scale study of shock physics - Proper motion measurements of young SNRs - SNRs (and SNe) in nearby galaxies
#1: Mapping of ejecta products Current/previous missions Chandra (XMM) Revealed detailed distribution of α-elements (plus Fe in several bright SNRs). SN explosion mechanism, SNR dynamics. Suzaku Detected weak emission from Fe-peak elements in spatially-integrated spectra. SN Ia physics, plasma diagnostics. AXIS will achieve both of them. We will prove why AXIS can work better than Athena for these studies.
Small-scale structure Tycho s SNR; R ~ 4 arcmin (Warren et al.2005) Fe L Si K Continuum Resolved ejecta knots of different elements
Problems in Chandra Low S/N ratio in the Fe band Spectrum of Fe knot (Yamaguchi et al. 2017) 6.35-6.6 kev AXIS will provide Fe images with similar quality to the Si band.
LMC velocity 90% credible 90% credible Fe ejecta in LMC/SNR SNRs Hitomi 17-cnt(!) spectrum suggests redshift of Fe. Hitomi Collaboration (E. Miller et al., submitted) v ~ 1200 km/s v = 0 km/s MCMC result Chandra data have too low statistics to constrain its spatial distribution. Si K band Fe K band
N132D (previous slide) is only 1 in radius, but many objects, especially in LMC/SMC are even smaller still (smaller -> younger) N103B, 15 in radius Chandra data; 450 ks obs ATHENA simulation LOTS of other small, young remnants in the Galaxy and LMC that need sub-arcsec resolution, but take huge Chandra investments
Weak emission in the Fe band Suzaku detected Fe-peak elements from young SNRs 3C 397 Yamaguchi+15 Tycho Yamaguchi+14b Cr Mn Fe 3C 397 Ni Cr Mn Fe Fe Kβ Ni Tycho 5 6 7 8 9 Energy (kev) 5 6 7 8 9 Energy (kev) but cannot reveal their spatial distribution. AXIS will.
Is Athena better? Better resolution is better, but emission in young SNRs is intrinsically broadened. So EA and bgd are more important. At the collisionless limit: kti = (3/16) mi Vs 2 35 Z (Vs / 3000 km s -1 ) 2 [kev] ktfe = 0.9 MeV (@Vs = 3k); 2.5 MeV (@Vs = 5k) Thermal Doppler broadening of emission: FWHM = 2 (ln 2) 1/2 hν0 (2kTi / mic 2 ) 1/2 2 (ln 2) 1/2 (3/4) Ry Z 2 (kti / Zmpc 2 ) 1/2 0.17 Z 3/2 (kti / 100 kev) 1/2 [ev] FWHMFe = 68 ev (@Vs = 3k); 113 ev (@Vs = 5k) Calorimeter resolution probably useless for Fe group...
Comparison with clusters EW (Cr, Mn) Intrinsic width Ionization state SNR 50-200 ev 50~120 ev low ionized Cluster 2-5 ev ~10 ev He-like For clusters, calorimeter resolution is crucial. For SNRs, less so counts s -1 kev -1 0.5 0.3 0.2 SXS spectra of the Perseus Cluster: Hitomi Collaboration (Nature in press) Cr XXIII Mn XXIV Fe I (AGN) 1 0.5 0.2 0.1 Ni XXVII (w) Fe XXIV+ Ni XXVII CCD spectrum (XMM-Newton) Fe XXV (He β) 5.5 6.0 energy (kev) 7.4 7.6 7.8 8.0 energy (kev)
Requirement for energy resolution Simulations for Kepler s SNR Counts s -1 kev -1 1 10 0.1 Cr Mn Fe Kα Fe Kβ Ni 5 6 7 8 9 Energy (kev) FWHM 150 ev 180 ev 200 ev 250 ev 300 ev Need 180 ev at worst. 150 ev is absolutely preferable.
#2 Shock physics and particle acceleration Shocks are ubiquitous in the universe! SNRs offer the chance to observe shock fronts on small scales (sub parsec) Remnant of SN 1006-30 in diameter, but only 1,000 yrs old - If 2.2 kpc distant, 0.5 corresponds to 1.6e16 cm, or 0.005 pc thermal nonthermal - Shocks produce both thermal and non thermal emission; not entirely clear why
Shock precursor emission? - Synchrotron emission is produced from relativistic particles accelerated to highly nonthermal energies at the blast wave - Theory predicts that some faint emission should be ahead of the shock, from particles that have diffused upstream So radial X-ray profiles from these regions should show faint tail ahead of shock front right? Figures from Winkler, Williams, et al. 2014
black = data, red = Chandra PSF Not much evidence, though we really started to run into the background, i.e., longer observations wouldn t help much. If precursor not present, shock acceleration theories could be seriously wrong!
SN 1006 is the best place to test, but lots of other places as well. Quite cost-prohibitive with Chandra, could be done in > order of mag. less time with AXIS
Other shock physics (skipped in the interest of time) Uchiyama et al. 2007 - Chandra observed rapid (~yr) variations on small scales (~arcsec) of synchrotron emission - Interpreted as evidence for extremely high B-field - In studies of energy-dependence of width of synchrotron emitting rims, Ressler et al. 2014 and Tran et al. 2015 (with BJW and R. Petre) tested models of post-shock B-field damping - Results were relatively inconclusive, mostly due to running up against Chandra s resolution and effective area limitations
#3 Proper motion studies
Sub-arcsecond resolution allows for detailed proper motion studies of shock waves propagating into ISM Winkler et al. 2014, Katsuda et al. 2013 Difference image showing expansion of SN 1006
Can do this with ejecta as well, but requires very deep Chandra observations, and could still only do for Si-ejecta, not Fe :( Williams et al. 2017
Number of SNRs with at least some X-ray proper motions measured is perhaps a dozen but this number only grows with time. Era of precision astrometry in X-rays began with Chandra, but needn t end there. With sufficient point sources for WCS alignment, cross-mission proper motion studies are absolutely doable.
#4 SNRs in nearby galaxies The large effective area of AXIS enables systematic studies of SNRs in nearby galaxies, such as M31 (778 kpc). Chandra 700 ks observation of M83 (4.61 Mpc). -29:50:00 54:00 52:00 Decl. (J2000.0) 52:00 54:00 56:00 56:00 58:00 58:00 Decl. (J2000.0) -29:50:00 48:00 48:00 46:00 46:00 Long et al. 2014 30 20 10 13:37:00 R.A. (J2000.0) 50 40 36:30 30 20 10 13:37:00 R.A. (J2000.0) 50 40 36:30
46:00 46:00 48:00 48:00 54:00 52:00 Decl. (J2000.0) -29:50:00-29:50:00 52:00 Decl. (J2000.0) 54:00 56:00 56:00 58:00 58:00 30 20 10 13:37:00 R.A. (J2000.0) 50 40 36:30 30 20 10 13:37:00 50 40 36:30 R.A. (J2000.0) - Deep Chandra survey of M83 detected 378 point sources, 87 identified as SNRs (compared with 225 optical SNRs - Count rates generally not high enough to do detailed spectroscopy - Effective area of AXIS would make this possible, could compare SNR population with star-formation history at localized locations within galaxy. Would capture lots of other science as well! - Detection of SNe also possible: a recent paper by Bochenek et al. (2017) claims first ever detection of X-rays from a Type Ia SN. This places significant constraints on the surrounding CSM/ISM
Simulations Tycho s SNR at different distance normalized counts s 1 kev 1 10 6 10 5 10 4 10 3 0.01 0.1 M31 CXO M83 (4.6 Mpc) 10 Mpc Used simx-2.4.4 Tycho @... M31 (778 kpc) 0.5 1 2 5 Energy (kev) 10
Backup
SNRs in the LMC/SMC
Powerful (but not well-known) diagnostics Κα (2p 1s) Κβ (3p 1s) Ar-like Fe 8+ Yamaguchi et al. 2014, ApJ, 780, 136 K-shell Kβ/Kα Flux Ratio 0.15 0.1 0.05 0 Neutral Ar-like Fe Kβ/Kα Flux Ratio Ne-like (no 3p e-) 0 5 10 15 20 Charge Number L-shell M-shell Ne-like Fe 16+ K-shell L-shell M-shell
Revealing immediate post-shock ejecta Forward Shock Unshocked Fe Low-ionized Fe Highly-ionized Fe Explosion Center Reverse Shock Reverse Shock Contour: Kα Color: Kβ Surface Brightness [10-6 photons cm -2 s -1 arcmin -2 ] 0 0.5 1.0 1.5 2.0 Kα 0.1 Kβ 0 1 2 Radius [arcmin] 3
Asymmetric ejecta motion? Fe K emission peaks near the SNR center redshift component dominant? XMM (Behar+2001) Rest frame Si Fe 44Ti Cas A (NuSTAR) Grefenstette+14
Still need a sensitive observatory Both CCDs Suzaku (2005-2015) Cr Mn Ni Sensitive to Fe-peak elements.