Building the cosmic distance scale: from Hipparcos to Gaia

Transcription

1 The Fundamental Distance Scale: state of the art and the Gaia perspectives 3-6 May 2011 Building the cosmic distance scale: from Hipparcos to Gaia Catherine TURON and Xavier LURI 1 ESA / ESO-H. Heyer

2 Fundamental distance scale (1) Much progress in parallax measurements the last 15 years but still only about stars with relative parallax accuracy better than 10% all in the solar neighbourhood very few Cepheids, RR-Lyrae, super-giants, etc. Much progress in photometric & spectroscopic measurements but many different photometric and spectroscopic systems non-uniformity in colour or abundance scales different stellar atmospheric modelling various transformations colour Teff various bolometric corrections etc difficult to compare observations between themselves and with isochrones 2

3 Fundamental distance scale (2) Remaining major sources of uncertainty location of (main) sequence vs age and chemical abundances calibration of PL(-C) relations vs metallicity, age reliable determination of reddening distance to the LMC Missing accurate parallaxes for very large samples of all galactic populations direct distance determination of large samples of stellar candles unambiguous detection of binary (or +) systems reliable abundances for large samples of field stars and stellar candles test of the universality of PL(-C) relations Gaia, Hubble, high resolution spectro, stellar atmoshere modelling, 3

4 See talks by Jos de Bruijne, Laurent Eyer and Eduardo Masana for more details about the performance of Gaia 4

5 Field stars 5

6 Nearby stars revisited by Hipparcos > 40 % of stars estimated to be closer than 80 pc from spectral classification (MSS) are further than 80 pc (Binney et al 1997) 40 % of stars of CNS3 catalogue are further than 25 pc (Turon 1999) 80 pc 6

7 The HR diagram of nearby stars before and after Hipparcos Hipparcos Mv σ π /π < 0.10, σ(b-v) < 0.25 mag CNS3 (supposed to be < 25 pc) B-V Hipparcos new luminosity calibrations of MK spectral types and luminosity classes, and of various photometric systems. 7

8 From Hipparcos to Gaia 8

9 Standard error on trigonometric parallax vs mag Hipparcos Gaia Hipparcos Catalogue (Perryman et al. 1997) van Leeuwen & Fantino (2005) Courtesy J. de Bruijne (ESA) 9

10 Luminosity calibrations with Hipparcos and Gaia Hipparcos Hipparcos 2 Gaia σ π /π < 0.1 % σ π /π < 1 % σ π /π < 10 % ~ 11 x 10 6 up to 5-10 kpc (Mv<-5) up to 1-2 kpc (Mv<5) ~ 150 x 10 6 up to kpc (Mv<-5) up to 2-5 kpc (Mv<5) Error on Mv 0.3 mag at 100 pc 0.1 mag at 10 kpc Stellar pop. HR diagram < 10 % mainly disk all populations, even the rarest -4 to 13, -0.2 to 1.7 all mag and colours 10

11 Gaia: stellar population sampling Thin disk Thick disk Halo Bulge σ π /π < 10% at V=15 11

12 Gaia: sampling in [Fe/H] Crucial for main sequence fitting and abundance effects on luminosity calibrations! Huge and systematic sampling of stars of all metallicity Systematic detection of (extremely) metal poor stars 12

13 Open clusters 13

14 Hipparcos: the Hyades cluster Hipparcos: first 3D picture of an open cluster + kinematics Mean distance of the 134 stars within 10 pc of the cluster centre (tidal radius): D= ± 0.27 pc, M= 3.33 ± 0.01 Internal velocity dispersion of 0.3 kms -1 Mass segregation clearly visible (Perryman et al. 1998) Hipparcos 2: 150 within 15 pc, D= ± 0.50 pc, M= ± (van Leeuwen 2009) van Leeuwen 2009 Perryman et al

15 The Hyades observed by Hipparcos Hyades stars observed by Hipparcos: 190 Hipparcos stars: filled circles 27 additional Tycho star: open triangles Non observed: 174 Base des Amas only stars, open squares Also: - individual distances -> cluster zeroage main sequence - metallicity: [Fe/H] = 0.14 ± helium content: Y = 0.26 ± age: 625 ± 50 Myr (Perryman et al. 1998) 15

16 Hyades parallaxes: before and after Hipparcos Hipparcos (1997) versus GCTSP (van Altena et al 1995) parallaxes Perryman et al 1998 Hipparcos-2 versus HST parallaxes (McArthur et al 2011) 16

17 Sol Hyades from trigonometric parallaxes Hipparcos Gaia 1960 Courtesy M. Perryman

18 Hipparcos-2: nearby open clusters UMa Coma Ber Pleiades Coma Ber Pleiades Praesepe Hyades Hyades Hyades van Leeuwen

19 Open clusters First cluster observed in 3-D: the Hyades Hipparcos Hyades cluster with mean distance of stars within 10 pc to < 1 % 6 clusters with mean distance to < 5 % 4 clusters with mean distance to 5-10 % 8 clusters with mean distance to 10-20% Hipparcos-2 8 clusters within 250 pc with mean distance to < 3 % 11 clusters further than 250 pc with mean distance to < 10% Gaia complete membership census 3-D observation to ~ 1000 pc all mean distances to better than < 1% many new clusters to be discovered 19

20 Globular clusters 20

21 Hipparcos subdwarfs and subgiants distances and ages of globular clusters a few subdwarf candidates revealed to be evolved subgiants excellent fitting between the sequence formed by very low metallicity subdwarfs (-2.6 <[Fe/ H] < -1.8) with M92 sequence systematically larger distances and smaller ages for globular clusters: 11.5 to 13.5 Gyr (Reid 1997, Gratton et al. 1997, Pont et al. 1998, Caretta et al. 2000, Gratton et al. 2003) single stars o double stars M92 sequence for (m-m) 0 =14.61mag Pont et al

22 Globular clusters from Hipparcos to Gaia Hipparcos Gaia complete membership census (except in very central areas) none indirect return from subdwarfs and subgiants between 100 and stars per globular cluster ~ 20 with σ π /π < 10 % per star ~ 40 with σ π /π < 20 % per star for 1000 stars and < 10 kpc others clusters in the MW mean distance < 1 % (about 80 clusters) mean distance < 5 % (about 60 clusters) 22

23 Pulsating variables Impact of Hipparcos astrometry, photometry of Gaia astrometry, photometry and spectroscopy 23

24 BT V T Hp Hipparcos and Gaia broad band photometry Hipparcos mean number of transits: 110 epoch photometry to H p =12 Tycho epoch photometry to V T = Gaia mean number of transits: 80 epoch photometry to G=20 for G, BP and RP epoch low resolution spectra to from BP and RP epoch medium resolution spectra to12-13 from RVS Courtesy C. Jordi, EADS-Astrium BP RP G RVS 24

25 Gaia photometry standard error per Field of View transit Courtesy J. de Bruijne (ESA) 25

26 Gaia number of FOV transits over 5 years Max number of transits at ± 45 deg ecliptic latitude An average of 45x10 6 sources measured every day 200 Ecliptic plane 40 Galactic coordinates t 0, t min, t 0 + 6h, t 0 + 6h min, repeated days later 26

27 Cepheids δ Ceph (Hipparcos) Cepheids in M31 (Gaia) Hp B T -V T 27

28 Pulsating stars S Nor membership to NGC 6087 A delta Scuti back in the instability strip: AI Vel Hipparcos log L Hipparcos ground-based ZAMS ground-based parallaxes log T eff Lyngå & Lindegren 1998 Høg & Petersen

29 Cepheids Pop II Cepheids Pulsating variables from Hipparcos to Gaia Hipparcos 273 (2 new) ~ 100 with σ π < 1 mas P : 2 to 36 days ~ 30 ~ 2000 Gaia Census of galactic Cepheids with G 20 ~ 9000 Cepheids (*) All periods, colours and metallicity Up to 5-8 kpc with σ π /π < 1% All galactic with σ π /π < 10% in LMC none Cepheids with σ π /π ~ % Mean distance expected to 7-8 % (**) RR Lyrae 186 (9 new) only RR Lyr with good π All galactic RR Lyrae: (***) All metallicity Up to 1.5 kpc with σ π /π < 1%, σ π /π < 10% In globular clusters: mean σ π /π < 1% Windmark et al (*) (**) Clementini 2010 (***) Eyer & Cuypers

30 P-L of Cepheids: universal or not? The existence of a universal P L relation of classical Cepheids is an only historically justified illusion Sandage et al, 2009 In a reddening-free V, I relation we find that the coefficient of log P is the same within the uncertainties in our Galaxy as in the Large Magellanic Cloud (LMC), contrary to some previous suggestions. van Leeuwen et al Recent robust estimates of the LMC distance and current results indicate that the Cepheid PL relation is not Universal Romaniello et al Gaia will bring an extensive sampling of Cepheids in the Galaxy very accurate distances, colours and metallicity precise determination of slope and zero-point of the galactic PL relation + dependence on metallicity - but! extinction! (see Jos de B.) mean values in LMC and SMC but not individual measurements 30

31 and many other potential candles among the billion stars to be observed by Gaia! Red clump giants, tip the red giant branch, Mirae, type II Cepheids, etc. etc. 31

32 Magellanic Clouds and Local Group Galaxies 32

33 Estimated distance to the LMC from Hipparcos Perryman 2009 Naples 3 May 2011 Catherine TURON & Xavier LURI 33

34 Gaia LMC and SMC mean distance Number of objects observed ~ for LMC ~ for SMC Mostly faint objects, G ~ and thus σ π ~ 300 µas (worst case) Cepheids better! Distances ~ pc for LMC π = 20.8 µas ~ pc for SMC π = 16.4 µas Averaging all individual parallaxes Mean parallaxes (depth not taken into account) for LMC for SMC 34

35 Gaia LMC and SMC individual distances Assuming a depth of 3000 pc (still a large uncertainty on the depths of LMC and SMC) d = pc for LMC π = µas d = pc for SMC π = µas Error in mean parallax ~ 0.12 µas for LMC ~ 0.24 µas for SMC at the Gaia precision level 3D structure of the Magellanic Clouds observable 3D distribution of various types of (giant) stars within reach 35

36 Colour-magnitude diagrams in the Local Group Sculptor (79 kpc) Fornax (138 kpc) V=20 V=20 Courtesy V. Hill GAIA will observe individual stars in Local Group galaxies, with unambiguous discrimination with solar neighbourhood stars. 36

37 The third dimension: further and further Solar neighbourhood Hubble, Ground-based Distances to ~ 50 pc Precision: mas Solar neighbourhood Hipparcos Distances to ~ 500 pc Accuracy: mas All over the Galaxy Gaia ( ) Distances to~ pc Accuracy: µas In the Galactic Bulb Jasmine (?) Distances to~ pc Precision: 10 µas In the Local Group Next generation space Distances to~ pc astrometry (> 2018) Precision: 1 µas 37

38 Grazie per la Merci vostra de votre attention attenzione 38