Progenitor Constraints from SNe Ia Observations at Late Times - - PowerPoint PPT Presentation

Progenitor Constraints from SNe Ia Observations at Late Times

Melissa L. Graham, UC Berkeley Wednesday August 5 Carnegie SNIa Progenitors Workshop Today’s topics will include...

• 1. Nebular twins SNe Ia 2011fe and 2011by.
• 2. The ~1000 day spectrum of normal SN Ia 2011fe.
• 3. Intracluster supernovae.
• 4. Discussion questions.

Twin Type Ia Supernovae

Previous works with twin Type Ia supernovae include:

Silverman et al. (2013) “SN 2000cx and SN 2013bh: extremely rare, nearly twin Type Ia supernovae”

• peculiar SNe Ia (high temperature, high velocity features, large 56Ni masses)

Fakhouri Ph.D. Thesis 2013 “Supernova Ia Spectra and Spectrophotometric Time Series: Recognizing Twins and the Consequences for Cosmological Distance Measurements”

• considers normal SNe Ia (i.e., for cosmological analyses)
• even the closest spectroscopic twins have ∆m~0.1 mag (their Fig 3.7)

Foley & Kirshner (2013) “Metallicity Differences in Type Ia Supernova Progenitors Inferred from Ultraviolet Spectra”

• progenitor metallicity affects NUV flux in normal, optically twin SNe Ia

Twin Type Ia Supernovae

Foley & Kirshner (2013) “Metallicity Differences in Type Ia Supernova Progenitors Inferred from Ultraviolet Spectra” Spectra

• optically twins
• NUV flux discrepancy

MB,peak M56Ni Z 11fe

• 19.07 ~0.53 M

~1 Z 11by

• 18.47 ~0.31 M

~4 Z

☉ ☉ ☉ ☉

Light Curves

• decline rate twins
• discrepant peak brightness

Model spectra with varying abundances from Lentz+ 2000.

Twin Type Ia Supernovae

Graham et al. (2015) “Twins for life? A comparative analysis of the Type Ia supernovae 2011fe and 2011by” Spectra

• optically twins
• NUV flux discrepancy

Identical evolution in the silicon velocity over time.

Twin Type Ia Supernovae

Absolute magnitude light curves using pre-existing distance moduli. Residual light curve shows early-time peak magnitude difference is ~-0.6 mag. Graham et al. (2015) “Twins for life? A comparative analysis of the Type Ia supernovae 2011fe and 2011by”

Twin Type Ia Supernovae

Graham et al. (2015) “Twins for life? A comparative analysis of the Type Ia supernovae 2011fe and 2011by”

Twin Type Ia Supernovae

How did their optical twinness at nebular phases affect

• ur progenitor scenario interpretation for these SNeIa?

The nucleosynthetic products appear to be in similar amounts in both SNe Ia -- there is no evidence for excessive stable Ni in 2011by. Graham et al. (2015) “Twins for life? A comparative analysis of the Type Ia supernovae 2011fe and 2011by” If their distance moduli are incorrect, they could have reached the same peak brightness, and synthesized the same amount of 56Ni. Timmes et al. (2003): Can get a small change in M(56Ni) for a large change in abundance with sub-solar metallicity for both progenitor systems (e.g. Zfe=0.03 and Zby=0.90 --> M(56Ni) ~0.05 M).

Twin Type Ia Supernovae

How did their optical twinness at nebular phases affect

• ur progenitor scenario interpretation for these SNeIa?

The nucleosynthetic products appear to be in similar amounts in both SNe Ia -- there is no evidence for excessive stable Ni in 2011by. Alternative metallicity models to Lentz: ▪Walker models (similar, higher metallicity, less NUV flux) ▪Sauer 2008 (opposite effect, higher metallicity, more NUV flux from scattering) Graham et al. (2015) “Twins for life? A comparative analysis of the Type Ia supernovae 2011fe and 2011by” All metallicity models actually predict more spectral changes than just NUV flux.

Twin Type Ia Supernovae

How did their optical twinness at nebular phases affect

• ur progenitor scenario interpretation for these SNeIa?

The nucleosynthetic products appear to be in similar amounts in both SNe Ia -- there is no evidence for excessive stable Ni in 2011by. Alternatives to metallicity that affect NUV flux: ▪radial distribution of nucleosynthetic products ▪viewing angle (even if ignition points isotropic) ▪difference in kinetic energy and/or ejecta mass ▪outer layer radial density gradient Affect optical flux or spectral features? ▪steeper light curve rise ▪high-velocity photospheric lines ▪changes silicon line velocity gradient Graham et al. (2015) “Twins for life? A comparative analysis of the Type Ia supernovae 2011fe and 2011by” *Central density* and *total mass* also affect the

56Ni in a way correlated with progenitor metallicity.

SN Ia 2011fe At ~1000 Days

Graham et al. (2015) “Constraining the Progenitor Companion of the Nearby Type Ia SN 2011fe with a Nebular Spectrum at +981 Days”

SN Ia 2011fe At ~1000 Days

SN Ia 2011fe At ~1000 Days

[Fe III] line is gone after 2 years

SN Ia 2011fe At ~1000 Days

Potentially Na I D at the location

• f now-declined [Co III]; models

suggest Na I D flux would be negligible and only potentially seen at late times.

SN Ia 2011fe At ~1000 Days

Continued redward migration of all peaks in nebular phase spectra.

SN Ia 2011fe At ~1000 Days

, & (2013)

See also e.g., Shappee et al. (2013) Pakmor et al. (2008) Podsiadlowski (2003)

SN Ia 2011fe At ~1000 Days

SN Ia 2011fe At ~1000 Days

SN Ia 2011fe At ~1000 Days

Alternative method: Blackbody continuum flux suppresses the amplitude of spectral features, so the amount of flux variance

• n the characteristic velocity

scale of SNeIa (i.e. 10000 km/s) could also indicate a BB contribution.

Intracluster Supernovae

Image credit: Dr. Alex H. Parker, NASA, and SDSS.

Intracluster Supernovae

*91bg-like mg>-12.54 mr>-12.56 mg>-11.72 mr>-12.37 mg>-12.47 mr>-13.04 mg>-11.15 mr>-11.68

Sand et al. (2011) “Intracluster Supernovae in the Multi-Epoch Nearby Cluster Survey”

Intracluster Supernovae

Host Offset in Re Number

• f SN

19 hosted 4 hostless

Also <3σ of the cluster velocity dispersion, |Δv| < 3000 km/s.

Intracluster Supernovae

But Are They Truly Hostless?

Deep stacks of our SN-free CFHT images leave up to 2%

• f the stellar mass in low-mass galaxies undetected.

If the SNIa rate per unit mass is the same in red sequence galaxies and among IC stars… ...then of our 23 cluster SNeIa, ~0.5 might be hosted by the 2% in undetected galaxies. This is an important question because:

• 1. A rate enhancement in low-mass or globular cluster

hosts has implications for the progenitor scenario.

• 2. IC stars are uniformly old, >2 Gyr, providing independent

confirmation that progenitors are truly old.

Intracluster Supernovae

2009-12-14 CFHT r’ Abell 1650 3.14 kpc 2.0" N E r=0.5" SN r=0.69" 2013-01-25 HST 606W+814W Abell 1650 3.14 kpc 2.0" N E r=0.5" SN r=0.69" 2009-06-18 CFHT r’ Abell 85 2.38 kpc 2.0" N E r=1.0" r=1.20" SN 2013-09-18 HST 606W+814W Abell 85 2.38 kpc 2.0" N E r=1.0" r=1.20" SN G 2009-05-23 CFHT r’ Abell 2495 3.0 kpc 2.0" N E SN r=1.02" 2013-10-04 HST 606W+814W Abell 2495 3.0 kpc 2.0" N E SN r=1.02" 2009-01-27 CFHT r’ Abell 399 2.36 kpc 2.0" N E r=0.93" SN 2013-12-04 HST 606W+814W Abell 399 2.36 kpc 2.0" N E r=0.93" SN

CFHT HST HST HST HST CFHT CFHT CFHT

Intracluster Supernovae

2009-12-14 CFHT r’ Abell 1650 3.14 kpc 2.0" N E r=0.5" SN r=0.69" 2013-01-25 HST 606W+814W Abell 1650 3.14 kpc 2.0" N E r=0.5" SN r=0.69" 2009-06-18 CFHT r’ Abell 85 2.38 kpc 2.0" N E r=1.0" r=1.20" SN 2013-09-18 HST 606W+814W Abell 85 2.38 kpc 2.0" N E r=1.0" r=1.20" SN G 2009-05-23 CFHT r’ Abell 2495 3.0 kpc 2.0" N E SN r=1.02" 2013-10-04 HST 606W+814W Abell 2495 3.0 kpc 2.0" N E SN r=1.02" 2009-01-27 CFHT r’ Abell 399 2.36 kpc 2.0" N E r=0.93" SN 2013-12-04 HST 606W+814W Abell 399 2.36 kpc 2.0" N E r=0.93" SN

CFHT HST HST HST HST CFHT CFHT CFHT

CFHT deep stacks leave ~2% of the total stellar mass in cluster dwarf galaxies undetected. HST deep stacks leave ~0.2% of the total stellar mass in cluster dwarf galaxies undetected. This depends on adopted slope of the galaxy luminosity function. All but bottom left have no source detected… let’s take a closer look at the bottom left HST image.

Intracluster Supernovae

MV = -8.4, MI = -9.8 Not likely to be:

• - a chance alignment with a star,

background galaxy, or cluster galaxy

• - late-time emission from the SNIa

Is consistent with:

• - a low-mass red sequence galaxy
• - a globular cluster (GC)

HST 606W+814W Abell 399 0.59 kpc 0.5" E F r=0.31" SN

If the rate per unit mass is the same in dwarfs/GC, surface density estimates find that a GC is more likely at this location due to the nearby elliptical.

Intracluster Supernovae

Implications for SNeIa regarding...

… rates in low-mass red sequence galaxies. They may be enhanced by a factor of ~5.

(~55 if 1 of our IC SNeIa are in the ~0.2% of stellar mass below HST limits.)

… rates in globular clusters. May be enhanced by a factor of ~25.

~The level in models of binary formation, and less than current constraints.

… progenitor scenarios. Some SNIa progenitors are >2 Gyr old.

Discussion Questions

“We find that the nebular spectra suggest the nucleosynthetic yields are quite similar for SNe 2011fe and 2011by, but we cannot rule out a contrivance of different 56Ni masses with line blending and ionisation temperatures to create such twin-like nebular spectra.”

Are there degeneracies that could make non-twin explosions have twin nebular spectra? Having both 11fe and 11by be significantly sub-solar is discrepant with e.g. Mazzali’s work showing density *is* important, but the full custom models are time-consuming; is there some middle ground? What is the source of the continuing redward shift of nebular lines over time?

Progenitor Constraints from SNe Ia Observations at Late Times