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Hubble’s Constant, the Oosterhoff Dichotomy and Hydrogen Ionization Fronts.

Hubble’s Constant, the Oosterhoff Dichotomy and Hydrogen Ionization Fronts. Shashi M. Kanbur University of Florida, September 2009. Acknowledgments. Chow Choong Ngeow, Douglas Leonard, Lucas Macri, Robert Szabo, Robert Buchler, Marcella Marconi.

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Hubble’s Constant, the Oosterhoff Dichotomy and Hydrogen Ionization Fronts.

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  1. Hubble’s Constant, the Oosterhoff Dichotomy and Hydrogen Ionization Fronts. Shashi M. Kanbur University of Florida, September 2009

  2. Acknowledgments • Chow Choong Ngeow, Douglas Leonard, Lucas Macri, Robert Szabo, Robert Buchler, Marcella Marconi. • SUNY Oswego undergrads: Dylan Wallace, Dan Crain, Greg Feiden, Richard Stevens, Robin Dienhoffer, Frank Ripple, Sean Scott, Earl Bellinger, Lillie Ghobrial, Mike Evans, Martin Berke. • Isaac Richter, Tim De Haas, Andy Missert, Matthew Turner, Alex James, Eamonn Moyer, Jillian Neeley. • NSF, AAS, HST.

  3. The Cepheid PL Relation • This relation is not linear – at least in the LMC: change of slope between short (log P < 1) and long (log P > 1) period Cepheids. • OGLE II/III data using OGLE determined reddenings and the Zaritsky reddening map. • Need detailed statistical tests for this. • It is NOT sufficient just to look at the slopes plus or minus some standard deviations.

  4. Multiphase PL/PC relations • http://www.oswego.edu/~kanbur/IRES2009/Vphase.mov • http://www.oswego.edu/~kanbur/IRES2009/Iphase.mov • http://www.oswego.edu/~kanbur/IRES2009/Cphase.mov • http://www.oswego.edu/~kanbur/IRES2009/Wphase.mov

  5. LMC tests • F test. • Schwarz Information Criterion. • Testimator plus others. • OGLE II/OGLE III plus long period Cepheids. • MACHO, Sebo et al, Perrson et al. • OGLE II reddenings plus Zaritsky reddenings. • BVIJH non-linear. • K marginally nonlinear. OGLE II Wessenheit linear, OGLE III Wessenheit marginally nonlinear. • PL/PC cancel each other out – that is the Wessenheit is linear.

  6. JHK Data • 3 years observing campaign using 1.5m NOAO telescope plus CPAPIR and OGLE LMC pointings. • 2 years of Sloan filter data again using LMC OGLE pointings. • Analyzing this data currently.

  7. M33 DIRECT data

  8. Impact on H0 • Calibrate SNIa diagram with Cepheids. • μ0 = μV – 2.45(μV – μI). • W = V – 2.45(V-I). • There is a difference when used with OGLE III with these data. • W is less sensitive to possible changes of slope in V and I. • http://www.oswego.edu/~kanbur/IRES2009/H0impact.pdf

  9. Mid-InfraRed PL relations

  10. Physics • PL/PC relation connected through the PLC relation. • PC relation affected through the interaction of the stellar photosphere and hydrogen ionization front (HIF). • Engaged: Color of star which is related to the Temperature of photosphere = temperature of HIF. • Engaged at low densities: Color of Star is related to temperature of photosphere which is less dependent on period. • Engaged at high densities: more sensitive to period. • Sudden: - either engaged or not. • ML relation affects phase/period of interaction. • Flat PC relation at maximum light for Galactic Cepheids, and for logP > 1 for LMC Cepheids.

  11. PC/AC Relations • Lmax ~ R2max T4max, Lmin ~ R2min T4min • Amplitude ~ 4log(Tmax – Tmin). • PC relation flat at maximum light – AC relation at minimum light and vice versa. • See this in LMC OGLE II/III Cepheids. • http://www.astro.umass.edu/~shashi/papers/paper1.pdf

  12. RR Lyraes • PC relation at minimum light is flat. • Higher amplitude RR Lyraes are driven to hotter/bluer temperatures/colors at maximum light. • PC relation is flat at minimum light because the HIF is further out in the mass distribution. • HIF always engaged with stellar photosphere for RR Lyraes. • But density changes as pulsation proceeds from minimum light. • http://www.astro.umass.edu/~shashi/papers/paper9.pdf

  13. The Oosterhoff Dichotomy • OoI: <P> ~ 0.65 days, Z = 0.001 • OoII: <P> ~ 0.55 days, Z = 0.0001 • Period-Amplitude (PA) relation different in the two groups. • Evolved RRab stars in OoI clusters follow a similar PA relation to that in OoII clusters • M3: OoI, M15: OoII. • V = a + blog P • V = a + c(B-V) – c(B-V) + blogP • Related to PC/AC relations as a function of phase

  14. M3/M15 analysis • M3 data from Benko et al (2007) • M15 data from Corwin et al (2008) • Fourier decomposition to smooth out observed data. • Use decomposition to estimate max/min. • BVI light curves. • Concentrate on RRab stars. • Possible evidence of a difference in PC/AC relations as a function of phase.

  15. PC/AC relations in RR Lyraes • Sloan RR Lyraes and M31 data usign HST. • Theoretical models computed by Robert Szabo. • M,L,T,X,Z. Two values of Z=0.001, Z=0.0001 • Range of M/L. Strong possibilities to constrain models and estimate reddening. • Kurucz atmosphere parametrized by effective gravity and photospheric temperature. • Comparing models with observations and understanding possible implications.

  16. Model Results

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