SN Ia rates and progenitors Mark Sullivan University of Southampton

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

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

Astrophysics of SNe Ia 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? Roche Lobe over-flow? Helium star channel? How does the SN Ia progenitor influence the explosion? What are the progenitors of SNe Ia and what can we learn from observations?

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

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

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! PESSTO

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

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

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

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 Shells of material: Ca, H, Fe, Na, etc. Dilday et al. 2012

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 PTF11kx progenitor system Dilday et al See also core-degenerate scenario (Soker et al. 2013) Prompt merger of WD and AGB star core

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

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

“Weaker” CSM High-resolution spectra of some SNe Ia show time variable blue- shifted CSM (eg SN 2006X; Patat et 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 Sternberg+ (2011) SN 2006X, Patat+ (2007) Rs Oph, Patat+ (2011)

VLT+XShooter CSM programme ToO programs on VLT+XShooter Measure Na I D absorption Maguire, Sullivan et al. 2013

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

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

But stretch also depends on galaxy type Low SFR High SFR

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

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

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

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

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

DTD from SNLS galaxy data Pritchet et al. in prep

t Power-law fit Pritchet et al. in prep

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

Two families of ‘normal’ SNe Ia?

Photometric properties

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

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

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

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