Summary of this work p We study the hydrogen line emission from SNR - PowerPoint PPT Presentation

����������������� ����������������� ���� � On On modeling of hydrogen line emission fr from supernova remnant shocks: the effect of of Lyman an line trap apping � Jiro Shimoda 1 Acknowledgements: Makito Abe 1 , Kazuyuki Omukai 1 1. Tohoku Univ. �����������������������

Summary of this work p We study the hydrogen line emission from SNR shocks including the effects of Lyman line trapping. p We find that the H a emission can be mildly absorbed by hydrogen atoms in the 2s state at the realistic SNRs. p Our calculation will explain the anomalous width of H a line with no cosmic-ray .

Balmer Line Emissions from Collisionless Shocks Winkler+14 Smith 97 Figures from Morlino+15 Supernova Remnants (SNRs) Pulsar Wind Nebulae Balmer line emissions (especially Hα) are ubiquitously seen in collisionless shocks propagating into the ISM.

Balmer Line Emissions from Collisionless Shocks Hereafter, we focus on the SNRs. (although our study is applicable to other Winkler+14 Smith 97 objects) Supernova Remnants (SNRs) Balmer line emissions (especially Hα) are ubiquitously seen in collisionless shocks propagating into the ISM.

Balmer Line Emissions from Collisionless Shocks Spectrum of Balmer line narrow Emissions broad (Ghavamian+02, for SNR SN 1006) The lines consist of “narrow” and ”broad” components.

Balmer Line Emissions from � Collisionless Shocks � ü Emission Mechanism (e.g. Chevalier+80) • The collisionless shock is upstream � downstream � � formed by the � interaction between H � charged particles and p � plasma waves rather � � than Coulomb collision. e � • The neutral particles (e.g. hydrogen atoms) are not SNR!shock! Charged particles → shock heating affected. Hydrogen atoms → no dissipation �

Balmer Line Emissions from � Collisionless Shocks � ü Emission Mechanism (e.g. Chevalier+80) upstream � downstream � p Collisional Excitation � H + p (or e) → H* + p (or e) � Emits “narrow” comp. H � p Charge Transfer H + p → p + H* p � � � Emits “broad” comp. e � SNR!shock! Charged particles → shock heating Hydrogen atoms → no dissipation �

Balmer Line Emissions from � Collisionless Shocks � ü Emission Mechanism (e.g. Chevalier+80) upstream � downstream � p Collisional Excitation � H + p (or e) → H* + p (or e) � Emits “narrow” comp. H � ü The width of “narrow” reflects the p Charge Transfer H + p → p + H* p � upstream temperature of hydrogen � � Emits “broad” comp. e � atoms. ü The width of “broad” reflects the SNR!shock! Charged particles → shock heating downstream proton temperature . Hydrogen atoms → no dissipation �

The width of narrow is “too broad” ü The width of narrow SNR Shock velocity Narrow component component is in the (km s − 1 ) FWHM (km s − 1 ) 30-50 km/s range Cygnus Loop 300 − 400 28 − 35 (equivalently, 2.5-5.6 RCW 86 SW 580 − 660 32 ± 2 eV). RCW 86 W 580 − 660 32 ± 5 RCW 86 NW 580 − 660 40 ± 2 � 1 eV ←→ 21 km/s Kepler D49 & D50 2000 − 2500 42 ± 3 0505-67.9 440 − 880 32 − 43 ü If these were the ISM 0548-70.4 700 − 950 32 − 58 equilibrium 0519-69.0 1100 − 1500 39 − 42 temperatures, then 0509-67.5 25 − 31 − all of hydrogen Tycho 1940 − 2300 44 ± 4 SN 1006 2890 ± 100 21 ± 3 atoms would be Sollerman+2003 completely ionized!

The width of narrow is “too broad” ü The width of narrow SNR Shock velocity Narrow component component is in the (km s − 1 ) FWHM (km s − 1 ) 30-50 km/s range Cygnus Loop 300 − 400 28 − 35 (equivalently, 2.5-5.6 RCW 86 SW 580 − 660 32 ± 2 eV). RCW 86 W 580 − 660 32 ± 5 RCW 86 NW 580 − 660 40 ± 2 � 1 eV ←→ 21 km/s Kepler D49 & D50 2000 − 2500 42 ± 3 ü The anomalous width of narrow 0505-67.9 440 − 880 32 − 43 ü If this were the ISM 0548-70.4 700 − 950 32 − 58 equilibrium component implies a pre-shock heating 0519-69.0 1100 − 1500 39 − 42 temperature, then all 0509-67.5 25 − 31 of the upstream hydrogen atoms at the − of hydrogen atoms Tycho 1940 − 2300 44 ± 4 vicinity of the shock (e.g. Smith+94). SN 1006 2890 ± 100 21 ± 3 would be completely Sollerman+2003 ionized!

� Possible upstream heating: (i) neutral precursor � p Charge Transfer upstream � downstream � � H + p → p + H* � ü A part of downstream H � hydrogen atoms can be back to the upstream p � region (e.g. Smith+94). � � e � ü The leaking hydrogen can deposit some energy flux to SNR!shock! the upstream fluid via Charged particles → shock heating several atomic/plasma Hydrogen atoms → no dissipation processes. �

� Possible upstream heating: (i) neutral precursor � p Ionization of fast neutrals upstream � downstream � � H + p/e → p + e + p/e � heat up H � p Charge Transfer H + p → p + H* p � � � e � Emits the anomalous narrow component with SNR!shock! the width of 30-50 km/s Charged particles → shock heating Hydrogen atoms → no dissipation �

� Possible upstream heating: (i) neutral precursor � p Ionization of fast neutrals upstream � downstream � ü Smith+94 doubted that there is enough time � H + p/e → p + e + p/e � for the heating until the fast protons swept heat up H � up by the shock again. p Charge Transfer H + p → p + H* ü The neutral precursor scenario has been p � � � studied in the literatures: e.g. Blasi+12; e � Emits the anomalous Ohira 12, 13, 14, 16; Morlino+12, 13. narrow component with SNR!shock! ü Recent hybrid simulations suggested no the width of 30-50 km/s Charged particles → shock heating significant broadening (Ohira 16). Hydrogen atoms → no dissipation �

� Possible upstream heating: (ii) cosmic-ray precursor � upstream � downstream � The CRs accelerating via DSA � mechanism can also affect � the upstream plasma (or can H � generate Alfvenic turbulence in the upstream region). p � � � e � The formation of the anomalous narrow heat up CRs component is similar to the SNR!shock! neutral precursor case. Charged particles → shock heating Hydrogen atoms → no dissipation �

� Possible upstream heating: (ii) cosmic-ray precursor � upstream � downstream � The CRs accelerating via DSA � mechanism can also affect � the upstream plasma (or can H � ü Morlino+13 provided the H a emission generate Alfvenic turbulence model based on this CR-precursor scenario. in the upstream region). p � � � ü Their model is now accepted as ”the e � The formation of the standard model” of the H a emission from anomalous narrow heat up CRs component is similar to the the SNR shocks. SNR!shock! neutral precursor case. Charged particles → shock heating Hydrogen atoms → no dissipation �

Possible upstream heating: (ii) cosmic-ray precursor The semi-analytical 10 0 model predicts the V sh = 4000 km/s anomalous narrow n 0 = 0.1 cm -3 component arising from p max = 50 TeV/c the CR precursor H α emissivity (Morlino+13). 10 -1 no CR ξ inj= 3.5; η TH = 0.0 0.2 0.5 0.8 10 -2 -100 -50 0 50 100 v x [km/s]

Possible upstream heating: (ii) cosmic-ray precursor 20 FWHM of narrow [km/s] 60 η TH = 0.8 55 50 45 40 35 30 25 20 5 10 15 20 25 30 35 40 45 50 Maximum Energy of CRs [TeV/c] p max [TeV/c] FWHM of the narrow component depends on the Maximum energy of CRs (Morlino+13).

Possible upstream heating: (ii) cosmic-ray precursor 20 FWHM of narrow [km/s] 60 η TH = 0.8 55 50 45 ü This model does not sufficiently include the 40 35 effects of Lyman line trapping. 30 25 20 5 10 15 20 25 30 35 40 45 50 Maximum Energy of CRs [TeV/c] p max [TeV/c] FWHM of the narrow component depends on the Maximum energy of CRs (Morlino+13).

Lyman line trapping Ly β→ H α H a 3p → 2s Ly b 3p → 1s H a H a is not absorbed by Ly b the hydrogen atoms in ground state. absorbed reemitted a) A part of hydrogen atoms in n=3 emit Ly b due to 3p to 1s transition . b) The emitted Ly b is is ab absorbed by the hydrogen atoms in in ground state. Eventually, Ly b is is converted to H a due c) Ev due to 3p p to 2s trans nsition. Optically thin for Ly b is “Case A” Optically thick for Ly b is “Case B”

Lyman line trapping Ly β→ H α H a 3p → 2s Ly b 3p → 1s H a H a is not absorbed by Ly b the hydrogen atoms in ground state. absorbed reemitted When the SNR shocks are in Case B, the efficient conversion of Ly b to H a yields “2s” hydrogen atoms, which absorb the H a photons.

Optical thickness of H a in the realistic SNR shocks p The number density of “2s” hydrogen atoms: n H (2s) � n H (1s) C 1s , 2s ∼ 10 − 8 -10 − 7 × n H (1s) A 2s , 1s A 2s , 1s ≈ 8 . 2 s − 1 Spontaneous transition rate: ≈ C 1s , 2s ∼ 10 − 7 -10 − 6 s − 1 Collisional excitation rate: � � � p Optical thickness of the H a photons: ∼ � n H (2s) � � � L τ ∼ σ ν n H (2s) L � 0 . 1 10 − 7 cm − 3 10 18 cm