1. Balmer Dominated Remnants: Constraints on SN Progenitors
Kelly Korreck
Harvard-Smithsonian Center for Astrophysics

2. Outline Balmer dominated remnants Science from these filaments
Density, Ti/Te
Neutral Modeling of the filaments
Balmer Remnants as probes of the progenitor

3. Balmer Dominated Filaments
Cygnus Loop
Composite: X-ray & H-
SN1006 (Raymond et al. 2007)
Balmer dominated filaments outline the shock blast wave front.

4. Spectra of Balmer Dominated Filament
Smith, Raymond, & Laming (1994) ApJ

5. How you get a broad and narrow H-?
BROAD COMPONENT
2 steps:
Downstream proton charge transfers with a neutral hydrogen to make a fast neutral hydrogen and a slow proton
The fast neutral is excited by a proton or an electron
Emission is Doppler shifted by the velocity of the fast neutral
NARROW COMPONENT
Upstream neutral excited by a proton or electron
Emitted at rest wavelength

6. Atomic Physics behind it all
Chevalier and Raymond (1978) & Chevalier, Kirshner, and Raymond (1980) proposed a method for studying neutrals based on the 2 components of the H-alpha lines.

7. Observations
There are several ways neutrals play a role in the observations of SNR. For example, FWHM of Broad H- component depends on neutral fraction. This broad to narrow ratio, Ibroad/Inarrow indicates the sharing of heating between atomic species. The neutral fraction also effects other diagnostic lines such as HeI/HeII. Neutrals are also thought to be a possible candidate to create a pre-cursor to shock.
Remnant
Ibroad/I Narrow
Tycho
(Smith et al 1991)
1.08
SN1006
0.73
0.8
1.1
Neutrals don’t participate in coulomb interactions
Why we care about pickup ions what are they how do we know they are there.
Broad to narrow compents are still higher theoretically than what is observed,
Some number of neutrals <20% can come upstream to pre-heat the shock. However, the reaction rate depends on temperature of pre-shoco material
The next step is to plot ionization versus position upstream to determine where the heating can occurr and how efficient the pre-cursor is.
The broad/narrow ratio decreases with increasing velocity and with neutral fraction: more neutral lower ratios.

8. Monte Carlo model parameters
Variables
Neutral fraction (1-90%)
Magnetic orientation (0,45,90)
Shock speed ( km/sec)
Te/Tp (0.1, 0.5, 0.9)
Atomic Interactions
Charge transfer
Excitation
Ionization
Low-Hybrid Wave Heating
Current “stylish” wave heating
Heat goes preferentially to electrons, then transfers to protons via Coulomb collisions
Heating occurs if VAlfven <vgyro
Can track each interaction versus distance from the shock front
Input Calculations

9. Predicted Ibroad/Inarrow
Variations based on
Te/Tp=
Shock Speed
Magnetic Angle
Smaller variations based on neutral fraction
Using the Ib/In ratio from the previous results, we can predict the magnetic angle of the shock
For SN 1006 ratio of 0.73 and the shock speed ~2800 km/sec, the parallel shock model fits the data as expected!

10. Comparison of Model to Ibroad/Inarrow Observed in Supernova
Remnant
Code Result
Obs.
Ratio
Tycho
(Smith et al 1991)
1.08
SN1006
0.73
0.8
1.1
Past work examined equilibrium according to shock soeed

11. Precursor heating
Depends on
Shock speed
Neutral fraction
60K increase versus the MK temperatures – no effect on the pre-shock area
Precursor extends to only one mean free path behind the shock

12. Recent Neutral Model Heng and Mc Cray(ApJ 2007)
SNR 1987A reverse shock reveals inconsistencies in the broad to narrow component ration in current models. --Velocity needs to increase to account for the greater likelihood of interaction with a proton that has a relative speed not as great as 3/4 vshock

13. Neutral conclusions
Neutral interactions are not a strong precursor to the shock
The broad to narrow intensity ratio is highly dependant on velocity and temperature equilibration (or lack thereof)
Neutral fraction has a decreased effect as the shock velocity increases-could be explained by the fall off of the charge exchange cross section with increasing shock speed as seen in Heng & McCray (2007, ApJ)
Transition region of the filament is important to get the proper velocity and broad to narrow ratio.

14. Balmer Filaments as Structure Probes

15. ISM interaction/structure
Temperatures and densities
Infer the structure of the ISM
Magnetic field information from shock physics
Waves/Instabilities- RT, KH, RM ….

16. SN1006-Balmer Filament (Raymond et al. ApJ 2007)
Northwest region of the filament
From past observations:
Thermal x-ray emission
(Long et al. 2003, ApJ, 586, 1162)
Low density ISM ~0.25 cm-3
Ejecta knots are present nearby the HST observation- these knots have been observed in X-rays (Chandra)

17. Structure of the Balmer Filament
Length scale of the ripples are about 1/10 of the radius of curvature
Ripples length scales can be accounted for with general ISM turbulence (~20% density fluctuations on a parsec scale)
The amplitude of the ripples however are stronger than the expected Kolmogorov spectra.

18. Balmer Filaments and Progenitors

19. SNR Balmer filament clues to SNe
Balmer width and structure--Structure of the ISM/CSM surrounding the explosion
Temperature , density of ISM---how much energy is deposited pre-explosion

20. Can we really “see” the CMS?
When does the CSM lose the signature of the progenitor:
Take a single degenerate case - WD + MS
(following Wood-Vasey and Sokoloski, 2006)
•Assume a wind that creates a cavity with a r~1.5 x1015 cm
•This will “relax”, meaning that the wind will equilibrate to the mean ISM value in t=4 x 105 years
So if the SN explosion goes off within ~40,000 years of the end of accretion there is a chance to “see” signatures of the CSM from the remnant interaction in the form of a Balmer filament. Similar work was done for SSXS by Chiang and Rappaport (1996).

21. Cloudy simulations
Photoionization code used to simulate the turn on and off of the progenitor’s photoinoizing radiation pre-explosion
Examined Luminosity of 1038 ergs
Looked at the ionization at 100, 1 000, , years after the source has shut off
For now: a cavity structure with an initial radius of 10^16 cm, density of 10 cm^-3
Take a snapshot of the neutral fraction at a distance of ~10^17 cm as that is an approximation based on where Balmer filaments are found in SN1006

22. Answers given by cloudy
There is a rather significant amount of ionization after 100,000 years!
H+/H0~0.2= 80% neutral for 100,000 years at 10^17 cm from the central photoionizing source
Much more work to be done- Such as simple case of constant density

23. Conclusions on Balmer remnants
Great place to explore ISM/Blast wave interactions
Can get information about Te, Tp, Tion, neutral fraction
Still need more work with modeling the progenitor effect on ISM to see what types of limits can be put onto Type 1a Progenitors

24. Future Campaign issues to resolve with Balmer remnants
Transition zone characterization with deep optical observations
Progenitor signatures from Balmer filaments and other shock physics of the SNR
Why the narrow line isn’t as narrow as it could be?