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OUTLINE OF THE TALK
Setting the scene
RR Lyrae as distance indicators
RR Lyrae as physics laboratory
RR Lyrae as stellar tracers
Conclusions
G. BONO, Univ. Rome Tor Vergata
Pulsation & Evolution of RR Lyrae stars
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Photometry of HB stars in M3 (STERNHAUFEN [star cluster] by P. ten Bruggencate 1927) Direktor der Univ. Sternwarte in Gottingen, photographic plates by Shapley
The link between RR Lyrae & HB stars becomes clear after W. Baade and after Schwarzschild the difference between fundamental & overtones
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RR Lyrae stars as distance indicators and stellar tracers
RR Lyrae variablesInitial mass (MS): ~0.8-0.9 Msun
Mass (HB): ~0.6-0.8 Msun
Core He + Shell H burning
[Fe/H] ~ -2.5 – 0.5 (Smith 2005)
Old: >10 Gyr (GCs, halo, bulge)Main Sequence (MS)
Horizontal Branch (HB)
Stetson + (2014)
M4
Simple stellar populations
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RR Lyrae in Carina dSph
RRs
ACs
Coppola et al. (2015)
Complex Stellar Populations
ACs intermediate-age
RRs old-age
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Horizonthal Branch stars
ZAHB
90% He-exh.
Central He burning [3α + 12C(α,γ)16O] – H-shell burning [CNO]
H+He partial ionization regions convective stable regions
Convective core + semi-convection!!!
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RR Lyrae Pulsation & Evolutionary Properties
RR Lyrae Instability Strip
BHB
Easy selection either color-color plane (BHB) or variability (RRL)
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Once upon a time RR Lyrae
S. I. Bailey (1854-1931)Pickering & Bailey (1895)
Bailey 1902 An. Har. 38, 1
J. C. Kapteyn (1851-1922)
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Why stars pulsate?LO
G K
[cm
2/gr
]
LOG T
Radial Modes
K & Υ mechanisms Eddington docet!
The main culprit is Cp!
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Why stars do not pulsate?Non-linear non-local time dependent
convective models …. + …. PdV
Stellingwerf RR Lyrae pulsation models
Based on the treatment of the transport equation by Castor (1968)Based on updates of Stellingwerf’s original code followed extensive and detailed investigations of RR Lyrae properties.
(Bono & Stellingwerf 1994 ApJS, Bono et al. 1997 A&AS, ApJ, Bon o et al. 2000, 2003 MNRAS, Marconi et al. 2003 ApJ, Di Criscienzo et al.2004 ApJ, Marconi & Clementini 2005, Marconi & Degl’Innocenti 2007, Marconi et al. 2009) + Budapest group
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Non-linear convective models:U Comae field RRc variables
GB + (2000)Similar fits can also be provided for radial velocity, radius curves!!!
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RRL as distance indicators
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Mv = α + β [Fe/H]
Uncertainties on both α and β (theory & observations)Evolutionary effectsHeavy dependence on individual reddening uncertaintiesIndividual metal abundances
Bono et al. (2003), Cassisi et al. (2004), Catelan et al. (2005).
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Basic leading physical arguments
Mbol = const + 5log R + 10log Teff Stefan-Boltzmann
P = √(R/g) von Ritter relationg=surface gravityP = Q ⁄ √ρ
Warning! The Period brings in the Stellar mass ….
Period-Luminosity-Color
Mbol = α + β*log P + γ*log TeffM_X = α + β*log P + γ* CI
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Why we use PL instead of PLC relation? Observations: sensitivity to reddening uncertainties
Theory: sensitivity to color-temperature relations
Cepheid Pulsation & Evolutionary Properties Cepheid do obey to a PLC relations (consequence of a Mass-Luminosity relation)
LogL/Lo = α + β Log P + γ Log Te Mx = α + β Log P + γ CI The PL neglects the width in temperature of the IS This assumption is valid in the NIR, but not in the optical [σ (V)=0.2-0.3 mag]
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Why RR Lyrae do not obey to a PL/PLC relation?
An open issue for more than half century!!!
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RR Lyrae Distances Based on NIR PL relations
Longmore et al. (1989)
Log P [days]
mk
[mag
]
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Why NIR is better than optical?
Bono et al. (2001)
Mv(RR) = α + β [Fe/H]
Affected by evolutionary effects!
MK
MV
MK
MV
Log PLog P
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Why NIR is better than optical?
BC_I
BC_V
BC_K
Teff [K]
In the NIR the coolest are the brightest!!
Bono + & Marconi +
In the B-band the hottest are the brightest!!
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RR Lyrae stars as distance indicators and stellar tracers
RR Lyrae variablesObserved NIR PLLongmore et al. (1989)
Theoretical PLZBono et al. (2001,2003)
Theoretical PLZCatelan et al. (2004)
Catelan et al. (2004)
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PL/PLC in RR Lyrae & Cepheids
In Cepheids the PL/PLC is a direct consequence of the ML relation more massive stars are, at fixed Teff, brighter
lower gravities longer periods optical/NIR
The difference in mass for RR Lyrae stars is at most of the order of 20% the PL/PLC is the consequence of the variation in the BC
This is the reason why it shows up with R/I-band!!!
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RR Lyrae in M5J, (71), K (120) with SOFI@NTTJ, (25), K (22) with NICS@TNG
33 RRab + 24 RRc
K
J-K
LOG P [d]
LOG P [d]
K
K
μ=14.44 ± 0.02 mag
Astrometric distance μ=14.44 ± 0.05 mag!!Rees (1993, 1996)
Coppola + (2011)
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M4 a new spin on GC distance scale
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M4 a new spin on GC distance scale
Selected optical/NIR light curves
Stetson et al. (2014))
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M4 a new spin on GC distance scaleOptical/NIR PL relations
Braga et al. (2014))
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NIR K-band PL relations
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Wesenheit relationsW(BV) = V – Av/E(B-V) *(B-V) PROSReddening freeLinear over the entire period range <<Mimic a PLC relation>>Theory marginally dependent on mixing-length & on Y
CONSUncertainties in the reddening law (Cardelli like) Is the reddening law universal ?Accurate mean B,V,I or JHK magnitudes
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M4 a new spin to GC distance scaleOptical/NIR PW relations
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RR Lyrae stars as distance indicators and stellar tracersRR Lyrae variablesNIR/MIR PL relations
Dall'Ora et al. (2004), Madore et al. (2013)
XZ CygUV Oct
RR LyrSU Dra
Zero point from HST parallaxes (Benedict et al.
2011)
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New accurate M4 distances Spitzer data (Neeley et al. 2015)
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RR Lyrae stars as distance indicators and stellar tracers
M/Msun0.80 0.716 0.67 0.64 0.59 0.57 0.54
[Fe/H] -2.62 -2.14 -1.84 -1.62 -1.01 -0.70 -0.29
-enhanced mixture (BASTI, Marconi et al. 2015)
Pulsation models (calibration)
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RR Lyrae stars as distance indicators and stellar tracers
M4 DM measure
DM(PLZ-
Glob)=11.296±0.003±0.026DM(PWZ-
Glob)=11.267±0.011±0.035
Braga et al. (2014)
Agreement with literature
Without optical bands...DM(PLZ-
Glob)=11.282±0.003±0.015DM(PWZ-Glob)=11.267±0.012±0.019
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First Overtones vs Fundamentals
FO instability strip is narrower closer to a PL relation
The slope of FUs & FOs are different
The fundamentalization should be cautiously treated (Inno et al. 2013)
FOs on average fainter than FUs
Independent absolute calibration
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Optical-NIR PW relations
Distance determinations based on optical-NIR PW relations reduced scatter Mild dependence on the reddening law
The slope instead of the fine structure
The coefficients of the color terms in the PW(V, K) relation is smaller than in the PW(J, H) and in the PW(H, KS) relations (0.13 vs 1.63 & 1.92 mag).
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Reddening laws (Fritzpatrick et al. 2000)
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Reddening laws (MW + Magellanic Clouds)
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RRL as physics laboratory
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Results of non-linear convective pulsation models for RR Lyrae stars
Complete topology of the instability strip for both F & FO modes.
Bono, Caputo & Marconi 1995 ApJLBono, Caputo, Castellani, Marconi 1997 A&AS
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The pulsation relations by van Albada & Baker
On the basis of an extensive set of linear adiabatic pulsation models van Albada & Baker (1971, ApJ, 169, 311) derived the pulsation relations for RR Lyrae stars:
log P0 = -1.772 -0.68 log(M/Mo) + 0.84 log(L/Lo) + 3.48 log(6500/Te)
log(P0/P1) = 0.095 – 0.032 log (M/Mo) + 0.014 log(L/Lo) + 0.09 log(6500/Te)
Fundamental link between pulsation and evolutionary parameters
Link to theoretical Petersen’s diagram → pulsation mass estimates from double mode RR
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Bono, Caputo, Castellani, Marconi 1996 ApJL
Petersen Diagram
P1/P
o
Po
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Double mode RRL in Carina dSph
B
B
V
V
Phase Phase
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Double-Mode Pulsators
Carina dSphCoppola et al. (2015)
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Double-Mode Pulsators
Carina dSphCoppola et al. (2015)
ranking in mass & in metallicity
Solid observable!
Petersen Diagram
Soszynski + (2011,2015)
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GCs as tracers of the Halo
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Galaxy inventory:
Total mass 8x10^11Mo(Vera-Ciro + 2013)
Disk M~3x 10^10 Mo
Bulge M~1x 10^10 Mo(McMillan + 2011)
Halo M~1±0.4 x10^9 Mo(Deason + 2011)
Ngc(disk)/Ngc(halo)=20-30%
Total mass 10^7-10^8 MoA few percents
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GCs as tracers of the HaloLeaman + (2013): 61 GGCs
Absolute & relative agesTwo AMRs for [Fe/H]≥-1.8
1/3 of the sample is, at fixed age, 0.6 dex more metal-rich
Eggen, Lynden-Bell Sandage (1962)Searle & Zinn (1978) \& {Sandage}(1962)
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Their orbital properties are typical of disk/bulge GCs.
Leaman + (2013)
The bulk of the M.-R. sequence formed in the Galactic disk
A significant fraction of the M.-P. ones formed in dwarf galaxies that have been accreted by the MW.
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GCs as tracers of the Halo
Marín-Franch + (2009))
M.-P. formed in situ The younger and M.-R. have been accreted
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RR Lyrae (& BHB) as Halo tracers
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New findings
Kinman et al. (2007, 2012)Anticenter: 51BHB + 58 RRNGP a few hundred
Galactic V motion is retrogradefor RR+BHB with R_G > 10 Kpc[Carollo+ 2010; Beers+ 2012]The Outer halo is retrogradewhen compared with the solar neighborhood/inner halo
According to Angular momentum Distributions stars in the halo can be split in two groups: Main concentration (relaxed, Hattori & Yoshii 2011) + outliers
The ratio between out. & main con.increases as a function of R_GThe halo becomes more spherical with increasing R_GSimulations (McCarthy + 2012) Predict inner halo more flattened than outer halo
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Photometric surveys of the halo
QUEST Zinn + (2013)CATALINA Drake + (2013)LONEOS Miceli + (2008)ASAS Pojmanski + (2005)LINEAR Sesar + (2013)
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Oosterhoff dicothomy & Bailey diagramOoI GCs have <Pf>~0.55 days OoII GCs <Pf>~0.65 days The same applies for first overtones
The fraction of RRc is smaller in OoI (~17\%) than in OoII (~44%)
OoI GCs cover a broad range in iron & more M.-R, than OoII GCs that are typically very M.-P. ([Fe/H]~-2 dex)
GC in the MCs are typically Oosterhoff intermediate
The same applies for (some) Dwarf galaxies in the Local GroupBono + (1997)
Ab
Av
Log P
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A New Spin!
Fiorentino et al. (2014)
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A New Spin!
Fiorentino et al. (2014)
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and then …. Sculptor dSph536 RR Lyrae (82 new discoveries, 320 new pulsation analysis)
Martinez Vazquez + 2015 W(V,B-V) & W(V,B-I) Independent of metal content
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and then …. Sculptor dSph536 RR Lyrae (82 new discoveries, 320 new pulsation analysis)
Martinez Vazquez + 2015 I-band PL relation dependent on metal content
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GAIAGlobal Astrometric Interferometer for Astrophysics
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Waiting for E-ELTMICADO – AO assisted– J~K~30-31 mag
Cepheids in Coma
Ho only based on Primary distance indicators!!!
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Riess et al. 2011 -- SHOES
NGC 5584 SN Ia + Cepheids
8 (6) calibrating SN Ia
NIR phot. of external Cepheids
Homogeneous optical/NIR Phot. (WFC3)
NIR PL relations external galaxies Three independent zero-points:
NGC4258 (geometric/maser distance)
9 Gal. Ceph. Trigonometric parallaxes
92 LMC Cepheids
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Estimate of Ho with a precision of ~3%W
mν
Neff
Ho
Ho=73.8 ± 2.4 km / (s Mpc)
w = −1.08 ± 0.10
Neff = 4.2 ± 0.7
mν~0.1 ev
Freedman & Madore (2010)
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WMAP + PLANCK Ho = 67.8 ± 0.9 km / (s Mpc)
Tension or not tension?
Resolved sources 2.5σ level
Re-analysis by Efstathiou (2014) using a new maser distance to NGC4258 1.9σ See also Lensing + Megamaser + AGN
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Tips for possible discussions
Blazho effect
Formation and propagation of sonic shocks
Formation of He lines in the optical regime
Period Changes Oosterhoff dichotomy
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Conclusions
We desperately need multi-band photometry toidentify outer Halo RR Lyrae + red HB stars
RR Lyrae stars are solid distance indicators & Physics laboratories
RR Lyrae (Blue HB) are fundamental beacons to constrain the Galactic Halo & Bulge
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CreditsTo young, differently young & senior
colleagues with whom I have the pleasure to share this wonderful adventure
THANKS!
A. Pietrinferni, M. Fabrizio, V. F. Braga, I. Ferraro, G. Iannicola, L. Inno, R. Da Silva G. CoppolaOAC, M. Marconi,
M. Dall’Ora, M. MonelliIAC + G. FiorentinoOAB , M. Nonino, M. Marengo, J. Neeley + ESO + CARNEGIE