SN Ia rates and progenitors

1. SN Ia rates and progenitors Mark Sullivan University of Southampton

2. The cosmological power of SNe Ia SNe Ia are still essential for a meaningful measurement of dark energy Supernova Legacy Survey 3-year sample Nearly 500 SNe Ia With SNe: Minus SNe: Conley et al. 2011 Sullivan et al. 2011

3. New low-z searches (PTF, PS-1) High-z searches (SNLS, SDSS, ESSENCE) Calan/Tololo survey LOSS SCP and HZSST

4. Astrophysics of SNe Ia How does the SN Ia progenitor influence the explosion? What are the progenitors of SNe Ia and what can we learn from observations? White-dwarf/white-dwarf “merger” (double degenerate; DD) Accretion from a non-degenerate companion (single degenerate; SD) Accretes from a wind (symbiotic channel)? Roche Lobe over-flow? Helium star channel?

5. Cosmological application Relative brightness Relative brightness • SNe are standardizable, not standard, candles • Brighter SNe: • Have wider, slower light curves (classic Phillips relation), • Are bluer in their optical colour, • Have a dependence on their host stellar populations.

6. How does this progenitor diversity map into the cosmology? Kelly et al., Sullivan et al., Lampeitl et al., 2010

7. PESSTO Palomar Transient Factory (PTF) Wide-angle, variable cadence sky survey Looking for supernovae, novae, CVs 2 day cadence, search in g or R SN-like transient every 20 minutes on sky PESSTO has 25% of the NTT for 4 years 2000 classifications; 150 SNe detailed studies All data public!

8. SN 2011fe Transient located by PTF on night of August 23rd (Palomar) Found in M101 – ~6Mpc Went from non-detection to 17th magnitude in 24 hours. Early time data rule out a red giant companion (at time of explosion) Nugent et al. 2011

9. Direct progenitor imaging No progenitor (companion) star detected in HST imaging 10-100 times fainter limits than previous Ia progenitor studies Other complementary studies also place severe limits on SD scenarios Li et al. 2011

10. PTF11kx • SN Ia, z=0.047, slightly over-luminous • Remarkable optical spectra; Ca H,K absorption • Prompted detailed high-resolution study that revealed two CSM “shells” Dilday et al. 2012

11. Shells of material: Ca, H, Fe, Na, etc. • Hydrogen points to a SD progenitor • Ca II switches to emission in the later spectra – ejecta running into circumstellar material (CSM) • Also time variable Fe, Ti, Na, He lines • High resolution studies indicate at least two distinct shells of CSM Dilday et al. 2012

12. PTF11kx progenitor system Model must explain: • Multiple components of CSM, • A region evacuated of CSM, leading to a delay between explosion and the emergence of broad Ca and H. A SN Ia in a symbiotic nova system mayexplain these features: accretion onto a WD through the wind from a red giant star. However the CSM mass is very high See also core-degenerate scenario (Soker et al. 2013) Prompt merger of WD and AGB star core Dilday et al. 2012

13. Broad hydrogen emission strengthens with time, until a sudden drop • Possibly indicates SN ejecta has overtaken most of the CSM Silverman et al. 2013a

14. Further “Ia-CSM” Careful search of PTF and literature SNe IIn Now ~16 known members of the class with strong CSM All located in star-forming galaxies Silverman et al. 2013b

15. “Weaker” CSM Sternberg+ (2011) SN 2006X, Patat+ (2007) RsOph, Patat+ (2011) • High-resolution spectra of some SNe Ia show time variable blue-shifted CSM (eg SN 2006X; Patatet al 2007) • Majority of SNe Ia in spirals show blue-shifted Na I D lines, outflow from system • No CSM observed in SNe Ia in elliptical galaxies

16. VLT+XShooter CSM programme • ToOprograms on VLT+XShooter • Measure Na I Dabsorption Maguire, Sullivan et al. 2013

17. Results: Host galaxy properties Younger population Na I D features more common in star forming galaxies Less CSM in elliptical galaxies Maguire, Sullivan et al. 2013

18. Results: Link to progenitors SNe Ia displaying blueshifted CSM have on average higher stretches Maguire, Sullivan et al. 2013

19. But stretch also depends on galaxy type Low SFR High SFR

20. Results: Link to progenitors SNe Ia displaying blueshifted CSM have on average higher stretches Maguire, Sullivan et al. 2013

21. Link to luminosity? • Spectral luminosity indicator - pEW of Si II 4130A line • SNe Ia displaying blue-shifted material have weaker Si II Maguire, Sullivan et al. 2013

22. Delay-time distribution • DTD – time from SN progenitor formation to explosion • Strong evidence for both young and old components • Power-law t-1 fits the data well

23. DTD and the volumetric rate Power-law is a good fit to the data Perrett, Sullivan et al. 2012

24. But problems with the normalisation…. Fraction of 3-8M stars exploding as SNe Ia: η=2-2.5% (From SNLS data) Perrett, Sullivan et al. 2012

25. DTD from SNLS galaxy data Pritchet et al. in prep

26. Power-law fit t-1.35 Pritchet et al. in prep

27. Stretch dependence of DTD Hints of something interesting with stretch… Pritchet et al. in prep

28. Two families of ‘normal’ SNe Ia?

29. Two families of ‘normal’ SNe Ia? Photometric properties

30. Two families of ‘normal’ SNe Ia? Photometric properties Spectral properties

31. Two families of ‘normal’ SNe Ia? Photometric properties Spectral properties Host properties

32. Two families of ‘normal’ SNe Ia? Photometric properties Spectral properties Host properties Delay-time Distribution

33. Two families of ‘normal’ SNe Ia? Photometric properties Spectral properties Host properties Delay-time Distribution Environment Different progenitor types?