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A New Method for Measuring Extragalactic Distances and Estimating the Hubble Constant

This paper introduces an innovative method for measuring extragalactic distances using dust reverberation and time delay analysis. Traditional distance estimation methods, such as Cepheid variable stars and supernovae, exhibit significant uncertainties. The proposed technique employs the sublimation radius of dust grains and accounts for time dilation effects to achieve a calibration factor with minimal correction. Results obtained indicate a Hubble constant value of H0 = 73 ± 3 km/s/Mpc, providing an alternative to conventional methods and extending the measurable distance range significantly.

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A New Method for Measuring Extragalactic Distances and Estimating the Hubble Constant

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  1. A New Method For Measuring Extragalactic Distances Authors: Yuzuru Yoshii et al. Speaker: Zheng Xuechen 2014.03.25

  2. Outline • Introduction • New Method • Data Analysis • Results and discussion

  3. Introduction

  4. Why? • Estimate expansion rate • Hubble constant H0 • Distances

  5. Methods • Empirical • Cepheid variable stars • Tulley-Fisher • Faber-Jackson • Ia supernovae • et al. • Accurate • Physical model • SZ effect • Gravitational lensing • Parameters uncertainties -> not accurate

  6. New Method

  7. Base • Sublimation radius • Dust reverberation • Time delay  

  8. Light curves example

  9. Time delay correction • 1、Time dilation effect • 2、K-band shift and T gradient •  higher z, shorter Δt •  empirically correction • Correction <1%

  10. Calibration factor g g is from equation below Q: absorption coefficient Td: ~1700K from NIR a: dust grain mean radius

  11. Extinction and K-correction • Av :Galactic extinction • Kv: K-correction • assuming power law spectrum • 

  12. DATA aNALYSIS

  13. Procedures • 1、K-band subtraction • From V-band and power low • 2、cross-correlating V, K band • Use bidirectional interpolation scheme • 49 incidents to measure time lag

  14. Results and discusssion

  15. Results • Compare with Cepheid variable stars

  16. Compare • Our results: • H0 =73 ±3 km s-1 Mpc-1 • No empirical calibration • Extends 10 times distance • Cepheid variables: • H0 =75 ±10 km s-1 Mpc-1

  17. Systematic error • Index : • : • Dust grain radius a  •  • Largest systematic error • How to reduce? • Individually measuring • Determine UV-optical spectrum • Empirical method constrain

  18. Two other reverberation methods • 1、reverberation mapping of BLR • BLR size-L relation • Continuum – broad lines time delay • Need empirical calibration • 2、UV-optical continuum time lag • Physical method • H0 =42-44 km s-1 Mpc-1 • Model difficuties

  19. Thanks!

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