Download here. - SUNY Oswego

Hubble’s Constant, the
Oosterhoff Dichotomy and
Hydrogen Ionization Fronts.
Shashi M. Kanbur
University of Florida,
September 2009
Acknowledgments
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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.
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.
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Statistical Tests Important
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Slope is β±σ. This means
P(slope is in [β-σ,β+σ]) = 1 – α.
A = [short period slope is wrong], P(A) = α.
B = [long period slope is wrong], P(B) = α.
P(at least one mistake) = P(AUB) = 2α-α2.
1>α>0, 2α-α2 >α.
P(simultaneous test makes a mistake) is smaller
than P(standard comparison makes a mistake).
Multiphase PL/PC relations
 http://www.oswego.edu/~kanbur/IRES200
9/Vphase.mov
 http://www.oswego.edu/~kanbur/IRES200
9/Iphase.mov
 http://www.oswego.edu/~kanbur/IRES200
9/Cphase.mov
 http://www.oswego.edu/~kanbur/IRES200
9/Wphase.mov
LMC tests
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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.
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.
M33 DIRECT data
Cosmological motivation
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KP measured H0 to an accuracy of 10%.
Riess et al (2009) have measured H0 to an accuracy of
less than 5%.
Strong prospects exist for further reducing this error rate
to remove degeneracies in CMB based parameter
estimates.
Need to get better calibrating relations (LMC or NGC
4285)
Calibrate SNIa Hubble diagram. OGLE II results in a 12% change in H0 depending on whether a
linear/nonlinear PL relation is used.
With OGLE III, a 5% change.
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/IRES200
9/H0impact.pdf
Mid-InfraRed PL relations
Physics
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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.
PC/AC Relations
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/paper
s/paper1.pdf
 Lmax ~
RR Lyraes
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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
The Oosterhoff Dichotomy
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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
M3/M15 analysis
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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.
PC/AC relations in RR Lyraes
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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.
Model Results