physical and chemical inhomogeneities in the Vela SNR

Transcription

1 XMM-Newton: The Next Decade 2007 Science Workshop 4 th -6 th June 2007 Madrid, España A high-resolution survey of the physical and chemical inhomogeneities in the Vela SNR Collaborators Marco Miceli, INAF Osservatorio Astronomico di Palermo Consorzio COMETA, Italy F. Bocchino, INAF Osservatorio Astronomico di Palermo, Italy F. Reale, INAF OAPa, Università di Palermo, Italy S. Orlando, INAF Osservatorio Astronomico di Palermo, Italy

2 The Vela SNR Distance: ~250 pc Age: ~11000 yr Combined analysis of 3 XMM- Newton EPIC observations of the northern rim of the shell Our aims: High-resolution study of a large area (~11 pc 2 ) of the shell Distribution of the physical and chemical properties of the shocked plasma kev (ROSAT All-Sky-Survey)

3 The data FilD Miceli et al. 2005, A&A, 442,513 RegNE FilE

4 Morphology of the X-ray emission kev kev border of the shell RegNE 4x10 18 cm Hreg FilD FilE H FilE S FilE 0 cnt/s 2.8x cnt/s 4.2x10 - Green: X-ray contour levels at 75% of the maximum in the kev band Red: X-ray contour levels at 50% of the maximum in the kev band

5 Thermal structure

6 Spatially resolved spectral analysis Spectra extracted from homogeneous regions where the median photon energy has low fluctuations (ΔMPE/MPE 3%) kev T I =1.1±0.1x10 6 K T II =2.3±0.3x10 6 K N I /N II ~7 T I =1.1±0.1x10 6 K T II =2.9±0.2x10 6 K N I /N II ~2 T II =2.6±0.1x10 6 K All spectra are described well by two thermal components (only one component in RegNE). The temperatures of the two components are almost uniform in the whole region. T I =1.1±0.1x10 6 K T II =2.6±0.1x10 6 K N I /N II ~2 T I =0.9±0.1x10 6 K T II =2.5±0.1x10 6 K N I /N II ~3 T I =1.2±0.1x10 6 K T II =2.5±0.1x10 6 K N I /N II ~8 T I =1.2±0.1x10 6 K T II =2.6±0.2x10 6 K N I /N II ~5 T I =1.2±0.1x10 6 K T II =2.9±0.2x10 6 K N I /N II ~15 0 cnt/s 4.2x10-4

7 Chemical structure

8 Chemical abundances in middle-aged SNR In middle-aged SNR the bulk of the X-ray emission is commonly associated with shocked ISM, but: Vela SNR: 6 X-ray emitting shrapnels, probably associated with ejecta (e. g. shrapnel D, with overabundant O, Ne, and Mg, Katsuda & Tsunemi 2005 ) Cygnus Loop: claims of chemical inhomogeneities at large (Miyata & Tsunemi, 1999, but see Levenson et al. 2002) and small scale (Leahy 2002), but with values always lower than (or consistent with) solar.

9 Equivalent width maps To investigate the spatial distribution of the chemical abundances we produce equivalent width images of the Ne IX and Mg XI emission lines: Ne IX Mg XI Continuum: thermal bremsstrahlung at 0.2 kev N H = 2.3x10 20 cm -2 Continuum band: kev Line bands: Ne: kev Mg: kev N.B. The continuum slope and the N H are quite uniform in the whole region Warning 1: Blending between the Ne IX K-lines and the Fe XVII L-lines Warning 2: Poor statistics for the Mg XI line

10 Equivalent width maps Ne IX EQW Mg XI EQW 0 ev ev 35

11 Spatially resolved spectral analysis - abundances Ne IX EQW =1 Ne/Fe =1.9±0.7 =1.0 (0-4) Mg XI EQW Center of the shell =1 Ne/Fe=5±1 =3.2±0.6 =1 Ne/Fe=7±2 =4±1 =0.48±0.03 Ne/Fe=2.1±0.6 =1.0( ) =0.63±0.06 Ne/Fe =5.2±1 =1.4±0.5 =0.61±0.06 Ne/Fe =2.4±0.7 =1.0±0.5 =0.61±0.03 Ne/Fe =2.2±0.6 =2.6±0.8 Chemical structure: inhomogeneities in O/O the =0.45±0.06 O, Ne, Mg, and Fe abundances. Significant overabundance of Ne/Fe and =1.6±0.4 Mg. =2.8±0.8 Chemically inhomogeneous ISM? Chemically inhomogeneous CSM? Ejecta (shrapnels?) mixed with the ISM/CSM? =0.72±0.03 Ne/Fe=5.3±0.7 =3.0±0.8 0 ev ev 35

12 New X-ray emitting ejecta within the Vela shell? The position of the shrapnels depends on their initial velocity (which is a function of their initial position in the ejecta profile) Dynamics of the SN explosion The chemical abundances of the shrapnels depends on their initial position (burning layer) during the SN explosion Nucleosynthesis processes A complete XMM-Newton survey (2 Ms) of the Vela SNR (because of its proximity) may provide new clues for the study of the nucleosynthesis processes and the explosion mechanisms in SNe

13 Conclusions Three XMM-Newton observations of the northern rim of the Vela SNR, covering a large area of the shell (~11 pc 2 ) Thermal structure: two thermal components with large variations of the emission measures. The high values of N I at South (where we observe low values of the median photon energy) may indicate the presence of dense, unresolved cloudlets. The hardening at North may be a consequence of the lack of these inhomogeneities. Chemical structure: inhomogeneities in the O, Ne, Mg, and Fe abundances. Significant overabundance of Ne and Mg. Chemically inhomogeneous ISM? Chemically inhomogeneous CSM? Ejecta (shrapnels?) mixed with the ISM/CSM? A complete survey of the Vela SNR may provide new clues for the study of the physical and chemical properties of the ejecta and of the CSM