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The Distance Scale of the Universe

The Distance Scale of the Universe. G. Clementini INAF - Osservatorio Astronomico , Bologna Acknowledgements: C. Cacciari , M. Marconi, V. Ripepi. __________________________________________________________________________________

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The Distance Scale of the Universe

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  1. The Distance Scale of the Universe G. Clementini INAF - OsservatorioAstronomico, Bologna Acknowledgements: C. Cacciari, M. Marconi, V. Ripepi __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  2. Layout of the lectures - The astronomicaldistanceladder: - basicconcepts - Directmeasure: trigonometricparallax -Indirectmeasure: DistanceIndicators - Primaryindicators - Secondaryindicators - Tertiaryindicators -PrimaryIndicators - The distanceto the LargeMagellanicCloud __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  3. The Hubble Law “ In standard big bang cosmology the universeexpands uniformly; and locally, accordingto the Hubblelaw, v = Ho xd wherevis the recessionvelocityof a galaxy at a distanced, and Hois the Hubbleconstant, the expansion rate at the currentepoch.” Freedmanet al. 2001, Ap.J. 533, 47 “The uncertainty in the distance is the major contribution to the error budget on Ho” __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  4. Distance modulus DistanceLadder ”Given the range spanned by the astronomical distances, the astronomicaldistanceladder ismadebyoverlappingtechniques and distanceindicators, startingfrom the mostclosebythatwe can calibrate directly." Brightest cluster galaxies Brightest cluster galaxies S E C O N D A R Y Colour-luminosity in ellipticals Tully-Fisher Luminosity class of spirals Luminosity class of spirals Globular clusters Globular clusters HII regions Brightest stars in galaxies Spectrosc. and photom. parallax P R I M A R Y Cepheids TRGB Main-sequence fitting Proper motion Gaia m - M = - 5 + 5 log dpc distancemodulus Parallax Distance (pc)

  5. Typicalastronomicaldistances Earth-Sun~ 8m ~ 1 A.U. Earth- Pluto ~ 660 m ~ 39.4 A.U. Sun - Alpha Centauri ~ 4.2 l.y. ~ 1.3 pc Sun - Iades ~ 150 l.y. ~ 50 pc Sun - Galactic Center ~ 25.000 l.y. ~ 8kpc Sun -LMC ~ 50 kpc Sun - Andromeda ~ 2.5x106l.y. ~ 770 kpc Sun - Locale Group ~ 3.3x 106 l.y. ~ 1Mpc Sun - M81 and Sculptorclusters ~ 6-10x 106l.y . ~ 2.5 Mpc Sun-M101 cluster ~ 15-20x 106l.y. ~ 5.4 Mpc Sun-Virgo cluster ~ 40x 106l.y. ~ 12 Mpc Sun - Coma cluster ~ 300x 106l.y. ~ 92 Mpc p I __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  6. Directmethods: trigonometricparallax 0<d<100 pc Milky Way Indirectmethods:: -Propermotions+statisticalparallax 0-500 pc open clusters40- 7000 pc -MainSequenceFitting globularclusters3000-10000 pc Spectroscopic and photometricparallax > 10000 pc Beyond the Milky Way primary500 -3×107pc Distanceindicators secondary 2×105 - 109 pc and beyond tertiary

  7. TrigonometricParallax Gaia Hipparcos __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  8. Directmethod: trigonometricparallax apparent position in June apparent position in December p = tangU.A./d ~ U.A./d nearby star p = 1" d = 1pc dpc = 1/p" Parallax p«1" pα Cen = 0.76" Earth December June 0 < d < 100 pc Sun

  9. HIPPARCOS Spaceastrometry satellite launchedby ESA in 1989 and operated until May 1993. The satellite measuredpositions, parallaxes and propermotionsof 118.218 starswithapparentmagnitudebrighterthanV~9 and 1milliarcseclevelastrometry. FinalCataloguepublished in 1997.

  10. GAIA Spaceastrometry satellite tobelaunchedby ESA in 2013. It will provide high accuracy astrometry (parallaxes, positions, proper motions) for ~ 1 billion stars in our Galaxy and other members of the Local Group down to an apparent magnitude V~20-22, and with an accuracy of 0.000001” at V=15 mag. http://www.rssd.esa.int/Gaia

  11. Gaia in a nutshell • ESA mission for launch in mid 2013, expected 5 (+1?) yr lifetime • all sky (i.e. ~ 40,000 deg2) survey complete to Vlim = 20  ~ one billion sources • high accuracy astrometry (parallaxes, positions, proper motions) • optical spectrophotometry(luminosities, astrophysical parameters) • spectroscopy (radial velocities, rotation, chemistry) to V = 16-17 • 5D (some 6D … up to 9D) phase space survey over a large fraction of the Galaxy volume • Data distribution policy: • final catalogue ~ 2019–20 • intermediate data release (TBD) • science alerts data released immediately • no proprietary data rights __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  12. Astrometric accuracy: the Hyades …and the Pleiades? •  = 7.59 ± 0.14 mas - 132 pc, MS fitting (Pinsonneault et al. 1998) •  = 7.69 mas - 130 pc, various methods (Kharchenko et al. 2005 ) •  = 7.49 ± 0.07 mas- 133 pc, from 3 HST-FGS parallaxes in inner halo (Soderblom et al. 2005) • = 8.18 ± 0.13 mas - 122 pc, new reduction Hipparcos data (Van Leeuwen 2007) • faintest MS stars have V < 15  Gaia individual parallaxes with ()/ < 0.1 %

  13. Indirectmeasure: DistanceIndicators A directmeasureofdistancethroughparallaxispossibleonlyfornearbyobjects. The distanceto more distantobjectsismeasuredusing “indirectmethods” thatrely on the useofsourcesofknownluminosity, the so called ”standard candles”. However, the ”standard candles” mustbecarefully “calibrated”. 100 Watt • PrimaryIndicators • SecondaryIndicators • TertiaryIndicators __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  14. PrimaryIndicators • VariableStars Cepheids~ 3×107pcP/L RR Lyrae< 106pcMV /[Fe/H] and PLKZ Novae106 - 107 pcL/td Eclipsingbinaries Miras~ 107pcP/L • Stars and evolutionaryphaseswithconstantluminosity RGB Tip ~ 107pc Red Clump HB stars • MS Fittingof open and globularclusters 40 < d < 7000 pc 3000 < d < 10000 pc __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  15. MainSecondaryIndicators Brighteststars in galaxies~ 8×106pc BrightestHII regions~ 2×107pc Globularclustersluminosityfunction~ 10-20×106pc Surfacebrightnessfluctuations~ 7×107pc Tully-Fischer relation ~ 15×107pc Colour-luminosity relation in ellipticals~ 108pc Supernovae~108pc MainTertiaryIndicators Luminosityclassofspiralgalaxies 3×108pc Dimensionsofgalaxies Total luminosityof the brightestgalaxies > 109pc

  16. PrimaryIndicators • Pulsatingvariablestars Cepheids~ 3×107pcP/L RR Lyrae< 106pc MV ~ const. • Stars and evolutionaryphases at constantluminosity RGB Tip ~ 107pc • MS Fittingof open and globularclusters 40 < d < 7000 pc 3000 < d < 10000 pc __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  17. PulsatingVariableStars L = 4R2Teff4 __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  18. Pulsating Variable stars __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  19. PulsatingStars adapted from Marconi 2001

  20. Red Variables MIRAs–SRs–SARVs/OSARGs–LSPs–ElipsoidalVariables Light curvesoften semi-regular and multiperiodic Mass-loss - Stellar winds - Dustemission A Smallamplituderedvariables (SARVs) B Semi Regular variables (SR) CMiras D Long SecondaryPeriodvariables (LSPs) Wood et al. 1999, Wood 2000 E Binaries

  21. Distanceindicatorsforold and intermediate agepopulations: P/L relation Miras 100 ≤ P≤ 1000 days Pop. I-II AGB fundamental-modeP/L SRsP> 50days Pop. I-II AGB P/L (m-M)LMC=18.39 PL(K) relations forO-rich (solidcircles) and C-rich (open circles) Miras in the LMC Whitelock, Feast & van Leeuven 2008

  22. Classical Cepheids Characteristics P = 1– 100(?) days Av 1.5 mag SpType: F6 – K2 Pop I Evo. Phase: BlueLoop Young stars, tracing star formingregions, spiralarms PL relation, H. Leavitt (1900s) L = Log P +  LG  100 Mpc  H0 HST Key Project and SNIa Project

  23. Classical Cepheid P/L relation Cepheids in the LMC Trig. Parall. of MW Cepheids  MCs Cepheid VIW(Ogle2)JHK P/L relations Fouque et al . 2003 Cepheid PL relation L = Log P +  B-W of MW Cepheids universal ? if yes metallicity dependent ? if yes HST Key Project 31 galaxies 700 Kpc < d < 20 Mpc (*) butsee e.g. Sahaet al. (2001), Tammanet al (2008, and referencestherein) fordifferentconclusionsabout the valueof H0. -0.2  0.2 mag/dex in V, I MCs Cepheid P/L relation at varius wavelengths Madore & Freedman 1991, 1992 H0= 72  8 km s-1Mpc -1 (*) Freedman et al. 2001

  24. Cepheid P/L relations in the MCs V0(LMC)=-2.760 logP-17.042 σ=0.159 mag (649 FU CCs) V0(SMC)=-2.760 logP-17.611 σ=0.258 mag (466 FU CCs) Udalski et al. 1999 Theoretical P/L: Mv=-2.75 logP -1.37 σ= 0.18 mag Caputo, Marconi, Musella 2000

  25. Classical Cepheids: open issues 1) Dependence of the Cepheid properties and PL relation on the chemical composition 2) Linearity of the PL over the whole observed period range __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  26. A general consensus on the “universality” of the P-L relations for Cepheids has not been reached yet ! Dependence of the Cepheid PL on chemical composition The Cepheid PL relation is often assumed to be universal: the LMC PL is used to measure the distance to extragalactic Cepheids independently of their chemical composition (see e.g. the HST Key Project). Dependence on chemical composition systematic effects on the extragalactic distance scale (and H0)!! __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  27. - Is the Cepheid P/L relation metallicity dependent? Romaniello et al. 2008 __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  28. Non-linear LMC P/L relations: the 10 days break Marconi, Musella & Fiorentino 2005 seealso: Fouqueet al. 2003 Sandage et al. 2004 Ngeow et al. 2005

  29. Ultra Long Period Cepheids Bird et al. 2009

  30. Ultra Long Period Cepheids Bird et al. 2009

  31. The Milky Way Cepheids and Gaia Only ~ 800 Galactic Cepheidsare known – most are located in the Solar neighbourhood, up to ~ 9000 are expected to be discovered by Gaia 400 Galactic Cepheids from David Dunlap DB distance and magnitude Gaia predicted accuracy for parallax 15 @ d < 0.5 kpc 65 @d< 1kpc 165 @ d < 2kpc Presently, ~ 250 Cepheids with parallax & photometry (10 with HST parallax) only ~ 100 with σπ≤ 1 mas (Hipparcos) Figure courtesy A. Brown Most (~ 3/4) Galactic Cepheids will have Gaia individual parallaxes to < 3% __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  32. TheMagellanic Cloud Cepheids and Gaia ~ 3300/2100 Cepheids are known (and observable by Gaia) in the LMC/SMC 600 Cepheids in the LMC (OGLE, Udalski et al. 1999) The bulk of the distribution for fundamental LMC pulsators lies at Period = 3 – 5 days Mv ~ -3  V ~ 15.8 – 16 individual distances to ~ 150% mean of 400 to ~ 7-8 % Cepheids with P ≥ 10 d Mv ≤ ~ - 4.2  V ~ 14.5 individual distances to ~ 80% Ultra-long period (> 100 d) Cepheids Mv ≤ ~ - 7  V ~ 12 4 in LMC, 3 in SMC (Bird et al. 2009) individual distances to ~ 45% (LMC) - 55% (SMC) direct (trigonometric) calibration of the cosmological distance scale __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  33. RR Lyrae stars Characteristics Pop II Evo. Phase: HB (He-coreburning) t > 10 Gyr Mv (RR) =[Fe/H] + PLZ in the K band MW  M31 Smith 1995

  34. Luminosity–metallicity relation of RR Lyraestars Mv(RR) =  [Fe/H] +  0.13 <  < 0.30 0.5 <  < 1.0 from : Hipparcos  = 3.46 ± 0.64 mas - Trig. Parallax RRLyr HST  = 3.77 ± 0.13 mas • Baade-Wesselink - HB (non variable stars) • Statistical Parallaxes Trig. Parallaxes MSF HB models __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  35. RR Lyraestars MW =0.20 ± 0.04 from: LMC  = 0.214 ± 0.047 M31  = 0.22 ± 0.06  = 0.22 ± 0.05 HB Models   0.23 Pulsation Models   0.23

  36. Tight PLZK relation (σ~0.05 mag) • MK=-2.101 logP+0.231[Fe/H] – 0.77 (Bono et al. 2003) • MK=-2.353 logP+0.175logZ – 0.597 (Catelan et al. 2004) Smalleramplitudes (AK~ 0.2-0.3 mag) • MK=-2.38 logP+0.08[Fe/H] – 1.07 (Sollima et al. 2008) Reticulum Reticulum = 18.52 ± 0.005(rand) ± 0.117(sys) LMC = 18.58 ± 0.03(stat.) mag ± 0.11(system.) Dall’Ora et al. 2004 Szewczyket al. 2008 RR Lyrae stars in the near-IR

  37. The RR Lyrae stars and Gaia RR LyraeMv= 0.5-0.6mag Presently, 126 RR Lyraes with < V > = 10 to 12.5 (750 - 2500 pc) σπ/π ≥ 30 % (Hipparcos) (Fernley et al. 1998) RR Lyr (<V>=7.8): only RRL star with good parallax estimate π = 3.46 ± 0.64 mas mod = 7.30 mag (new Hipparcos, van Leeuwen 2007) π= 3.77 ± 0.13 mas mod = 7.13 mag (HST, Benedict et al. 2011) ΔMv ~ 0.2 mag distance to 10% ! up to 70000 are expected to be discovered by Gaia in the MW halo and from 14000 to 40000 in the bulge. Gaia: within 1.5 kpcto σπ/π < 1% (≤ 2.5% within 3 kpc, 25-30% at 10 kpc) RR Lyraes in globular clusters with mean σπ/π < 1% __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  38. Pulsating variables with Gaia +15000-40000 in the Bulge adapted from Turon & Lurireview at the Distance Scale ESF Conference, Naples, May 2011

  39. Cepheids and RR Lyrae: open issues • RR Lyrae: • Mv=a[Fe/H]+b • Mk=αlogP+β[Fe/H]+γ • Slope, zero point, linearity of the • Mv-[Fe/H] relation • Dependence on off-ZAHB • evolution, detailed chemical • composition (Y,α-elements) • Zero point and coefficients of the • Mk(logP,[Fe/H]) relation • ⇒ error on distances > 10% • Cepheids: • PL,PLC, Wesenheit relations (optical/NIR) • Coeff. of the relations! • Dependence of the Cepheid’s • properties and PL on the • chemical composition • Linearity of the PL relation • Binarity/reddening/pulsation • mode • Discrepancy pulsational/ • evolutionary mass • ⇒ error on H0 > 4-5 % ??? for both types of variables moving to the infrared is an advantage

  40. Cepheid’s PLK in the 30Doradusfield of the LMC Ripepiet al. 2011 __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  41. RR Lyrae PLK in the Gaia SEP calibration field Ripepiet al. 2011 __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  42. Stars and evolutionaryphaseswithconstantluminosity __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  43. RGB Tip The I luminosityof the RGB Tip isconstantwithmetallicity: -2.2< [Fe/H] <-0.7 and age: 7< t < 17 Gyr The RGB Tip luminosity in the I band isabout4magbrighterthan the HB: d ~ 3 ×106 - 107pc Calibration: via a theoreticalmodelproviding the absoluteluminosityof the RGB Tip from the absolutemagnitudeof the RGB Tip of a cluster at knowndistance (e.g.ωCen) Bellazziniet al. 2001, Ap. J. 556, 635 __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  44. RGB Tip Calibration: from the absolutemagnitudeof the RGB Tip of a cluster at knowndistance (e.g.ωCen) Bellazziniet al. 2001, Ap. J. 556, 635 __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  45. MS Fittingof open clusters Ammasso Aperto M11 __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  46. MS Fitting: Open Clusters Hyades __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  47. MS Fitting: Open Clusters ΔV = 3 mag (m-M)Iades = 3.3 mag (m-M)Praesepe= 3.3 + 3 = 6.3 mag dPraesepe = 182 pc Hyades __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  48. MS Fitting: GlobularClusters Globular cluster M80 ~ 10 kpc __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  49. MS Fitting: GlobularClusters Fitting the MainSequenceof a globular cluster to a referencesequenceformedby fieldsubdwarfsof the samemetallicitywithknowndistance via trigonometric parallax. (m - M )0 = - 5 + 5 log dpc globular cluster MS subdwarfreferencesequence globular cluster distance 56 subdwarfs in the solar neighbourhood measured by Hipparcos with /  0.12 distances to 9 globular clusters with (m - M) = ± 0.12 mag Grattonet al. 1997, Ap. J. 491,749, Carretta et al. 2000,Ap. J, 533, 215 __________________________________________________________________________________ G. Clementini – GREAT School on the Science and Techniques of Gaia, Leiden, 23-27 January 2012

  50. MS Fitting: GlobularClusters Carretta et al. 2000, Ap. J. 533, 215

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