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Is the evidence for Dark Energy secure from supernova cosmology? PowerPoint Presentation
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Is the evidence for Dark Energy secure from supernova cosmology?

Is the evidence for Dark Energy secure from supernova cosmology?

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Is the evidence for Dark Energy secure from supernova cosmology?

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  1. Is the evidence for Dark Energy secure from supernova cosmology? Evidence for luminosity evolution of SN Ia from early-type host galaxies Young-Wook Lee Yonsei University, Seoul, Korea Yijung Kang (Yonsei), Young-Lo Kim (Lyon), Chul Chung (Yonsei) & Chang H. Ree (KASI)

  2. Dark Energy: The most serious problem in astrophysics • Most direct evidence for Dark Energy is from Type Ia supernovae…

  3. Discovery of Dark Energy from Type Ia SN Distances … fainter Hubble Residual (HR ≡ μSN – μz) HR Riess+98, Perlmutter+99 brighter Redshift

  4. Type Ia SNe “Standardizable” Candle: Peak luminosity = f(light-curve shape, color) Light-curve shape & color parameters: Dm15(B), D , s, c Assume no evolution with z Luminosity Time

  5. “Tinsley Effect”: Luminosity evolution of standard candle in observational cosmology Allan Sandage Luminosity (stellar population) evolution or Distance difference? Beatrice Tinsley 1968

  6. Hicken et al. 2009: SALT2 Childress et al. 2014 fainter brighter Mean age difference of SNIa progenitor between z = 0.0 & 0.7 ~ 4 Gyr

  7. What is the evidence that there is no evolution in SN Ia luminosity? • No correlation between SN luminosity (after standardization) and host galaxy properties (age related) at local universe (Riess+98; Schmidt+98; Perlmutter+99) N = 8 DHR = 0.006 +/- 0.07 mag. Between Early (old) & Late (young) Hosts • No Evolution But, this was based on small sample! N = 19 Schmidt et al. 1998

  8. But, more recent data from CfA show different result (Hicken+09) DHR = 0.14 +/- 0.07 mag between E/SO & Scd/Sd/Irr ! After LC & extinction corrections  Currently, there is no evidence that there is no evolution!

  9. Other well-established correlations from host galaxy studies 1. SNe Ia in less massive host galaxies are fainter by ~0.1 mag (e.g., Sullivan+2010) 2. SNe Ia in locally star-forming environments are ~0.16 magfainter than those in passive environments (Rigault+2013, 18; Kim, Lee+2018)  Most likely due to population age or metallicity..

  10. Project YONSEI: YonseiNearbySupernovaeEvolutionInvestigation (Since 2011) High S/N spectra for ~70 nearby early-type host galaxies • 34 nights with LCO 2.5m & MMT 6.5m long-slit spec. • For the first time, directly obtain population age & metallicity from absorption lines (Hb, Fe, Mgb) & population synthesis models • ETGs preferred because of age dating & low extinction • SNANA(Kessler+09) is used for the SNe LC analysis

  11. young old Kang, Kim, Lee+2016

  12. Host Galaxy Data on Metallicity vs. H-beta Grid Yonsei Model Chung, Yoon, Lee 2013 Thomas+2011

  13. Correlation between Host Mass (sv ) and Population Age: “Downsizing” (Kang, Lee+2016, 2019) Markov Chain Monte Carlo analysis  Correlation is significant at ~ 4.2 sigma level!  No apparent correlation with metallicity • Host mass – SN luminosity correlation is due to population age difference Open circles: Recent star-forming (“rejuvenated”) galaxies  excluded as ages are seriously underestimated

  14. Correlation between SN Luminosity & Population Age fainter brighter Correlation is significant at ~2.1 sigma level • SNe in younger hosts are fainter (after standardization) • Evidence for luminosity evolution! • ~0.15 mag fainter for dt = 4 Gyr (YEPS) Kang, Lee+2019, in prep.

  15. Conclusion Our result (based on age) and other correlations (based on age related parameters) all indicate that SNe Ia in younger population environments are fainter!  Evidence for luminosity evolution appears to be significant! Taken at face value, this effect can mimic a large fraction (~0.15 mag, ~63%) of the Hubble Residual used in the discovery of the dark energy!  Is the evidence for Dark Energy secure from supernova cosmology?