building the cosmic distance scale: from hipparcos to gaia · building the cosmic distance scale:...
TRANSCRIPT
Catherine TURON and Xavier LURI
The Fundamental Distance Scale: state of the art and the Gaia perspectives
3-6 May 2011
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Building the cosmic distance scale: from Hipparcos to Gaia
© ESA / ESO-H. Heyer
Naples 3 May 2011 Catherine TURON & Xavier LURI
Fundamental distance scale (1) Much progress in parallax measurements the last 15 years but … still only about 30000 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
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Naples 3 May 2011 Catherine TURON & Xavier LURI
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
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Gaia, H
ubble, high resolution spectro, stellar atm
oshere m
odelling, …
Naples 3 May 2011 Catherine TURON & Xavier LURI
See talks by Jos de Bruijne, Laurent Eyer and Eduardo Masana for more details about
the performance of Gaia
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Naples 3 May 2011 Catherine TURON & Xavier LURI
Nearby stars revisited by Hipparcos
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40 % of stars of CNS3 catalogue are further than 25 pc
(Turon 1999)
> 40 % of stars estimated to be closer than 80 pc from spectral classification (MSS) are further than 80 pc
(Binney et al 1997)
80 pc
Naples 3 May 2011 Catherine TURON & Xavier LURI
The HR diagram of nearby stars before and after Hipparcos
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Hipparcos
B-V Hipparcos → new luminosity calibrations of MK spectral types and luminosity classes, and of various photometric systems.
Mv
σπ/π < 0.10, σ(B-V) < 0.25 mag CNS3 (supposed to be < 25 pc)
Naples 3 May 2011 Catherine TURON & Xavier LURI
Standard error on trigonometric parallax vs mag
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Hipparcos
Hipparcos Catalogue (Perryman et al. 1997)
van Leeuwen & Fantino (2005)
Courtesy J. de Bruijne (ESA)
Gaia
Naples 3 May 2011 Catherine TURON & Xavier LURI
Luminosity calibrations with Hipparcos and Gaia Hipparcos Hipparcos 2 Gaia
σπ/π < 0.1 % - - 100 000 ★
σπ/π < 1 % 442 ★ 719 ★ ~ 11 x 106 ★
up to 5-10 kpc (Mv<-5) up to 1-2 kpc (Mv<5)
σπ/π < 10 % 22 396 ★ 30 579 ★ ~ 150 x 106 ★
up to 30-50 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. mainly disk all populations, even the rarest
HR diagram < 10 % -4 to 13, -0.2 to 1.7 all mag and colours
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Naples 3 May 2011 Catherine TURON & Xavier LURI
Gaia: stellar population sampling
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Thin disk Thick disk Halo Bulge
σπ/π < 10% at V=15
Naples 3 May 2011 Catherine TURON & Xavier LURI
Gaia: sampling in [Fe/H]
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• Huge and systematic sampling of stars of all metallicity
• Systematic detection of (extremely) metal poor stars
Crucial for main sequence fitting and abundance effects on luminosity calibrations!
Naples 3 May 2011 Catherine TURON & Xavier LURI
Hipparcos: the Hyades cluster
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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= 46.34 ± 0.27 pc, M= 3.33 ± 0.01
Perryman et al 1998
van Leeuwen 2009
• Internal velocity dispersion of 0.3 kms-1
• Mass segregation clearly visible
(Perryman et al. 1998)
Hipparcos 2: 150 ★ within 15 pc, D= 46.45 ± 0.50 pc, M= 3.334 ± 0.024
(van Leeuwen 2009)
Naples 3 May 2011 Catherine TURON & Xavier LURI
The Hyades observed by Hipparcos
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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 zero-age main sequence - metallicity: [Fe/H] = 0.14 ± 0.05 - helium content: Y = 0.26 ± 0.02 - age: 625 ± 50 Myr
(Perryman et al. 1998)
Naples 3 May 2011 Catherine TURON & Xavier LURI
Hyades parallaxes: before and after Hipparcos
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Hipparcos (1997) versus GCTSP (van Altena et al 1995) parallaxes
Perryman et al 1998
Hipparcos-2 versus HST parallaxes (McArthur et al 2011)
Naples 3 May 2011 Catherine TURON & Xavier LURI
Hyades from trigonometric parallaxes
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Gaia
2020
Sol
1960
Hipparcos
1990 Courtesy M. Perryman
Naples 3 May 2011 Catherine TURON & Xavier LURI
Hipparcos-2: nearby open clusters
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van Leeuwen 2009
Hyades Hyades Hyades
Coma Ber Pleiades
Praesepe Coma Ber
Pleiades UMa
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Open clusters
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Hipparcos First cluster observed in 3-D: the Hyades
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
Naples 3 May 2011 Catherine TURON & Xavier LURI
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)
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• single stars o double stars M92 sequence
for (m-M)0 =14.61mag
Pont et al. 1998
Naples 3 May 2011 Catherine TURON & Xavier LURI
Globular clusters from Hipparcos to Gaia
Hipparcos none indirect return from subdwarfs and subgiants
Gaia
• complete membership census (except in very central areas)
between 100 and 100 000 stars per globular cluster ~ 20 with σπ/π < 10 % per star ~ 40 with σπ/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)
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Pulsating variables
Impact of Hipparcos astrometry, photometry of Gaia astrometry, photometry and spectroscopy
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Naples 3 May 2011 Catherine TURON & Xavier LURI
Hipparcos and Gaia broad band photometry
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Courtesy C. Jordi, EADS-Astrium
Gaia • mean number of transits: 80 • epoch photometry to G=20 for G,
BP and RP • epoch low resolution spectra to
16-17 from BP and RP • epoch medium resolution spectra
to12-13 from RVS
Hipparcos • mean number of transits: 110 • epoch photometry to Hp=12 • Tycho epoch photometry to VT = 10.25
Hp
VT BT
G
BP RP
RVS
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Gaia photometry standard error per Field of View transit
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Courtesy J. de Bruijne (ESA)
Naples 3 May 2011 Catherine TURON & Xavier LURI
Gaia number of FOV transits over 5 years
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Galactic coordinates ≤ 40
≥ 200 An average of 45x106 sources measured every day
Ecliptic plane
Max number of transits at ± 45 deg ecliptic latitude
t0, t0 + 106 min, t0 + 6h, t0 + 6h + 106 min, repeated 10-30 days later
Naples 3 May 2011 Catherine TURON & Xavier LURI
Cepheids
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δ Ceph (Hipparcos) Cepheids in M31 (Gaia)
3.8
4.0
4.2
Hp .6
.8
1. BT-VT
Naples 3 May 2011 Catherine TURON & Xavier LURI
Pulsating stars
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A delta Scuti back in the instability strip: AI Vel
log Teff
Hipparcos
ground-based parallaxes
ZAMS
log
L
S Nor membership to NGC 6087
• Hipparcos • ground-based
Lyngå & Lindegren 1998 Høg & Petersen 1997
Naples 3 May 2011 Catherine TURON & Xavier LURI
Pulsating variables from Hipparcos to Gaia Hipparcos Gaia
Cepheids 273 (2 new) ~ 100 with σπ < 1 mas P : 2 to 36 days
Census of galactic Cepheids with G ≤ 20 ~ 9000 Cepheids (*) All periods, colours and metallicity Up to 5-8 kpc with σπ/π < 1% All galactic with σπ/π < 10%
Pop II Cepheids
~ 30 ~ 2000
in LMC none 1000-2000 Cepheids with σπ/π ~ 80-100 % Mean distance expected to 7-8 % (**)
RR Lyrae 186 (9 new) only RR Lyr with good π
All galactic RR Lyrae: 70 000 (***) All metallicity Up to 1.5 kpc with σπ/π < 1%, σπ/π < 10% In globular clusters: mean σπ/π < 1%
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Windmark et al. 2011 (*) (**) Clementini 2010 (***) Eyer & Cuypers 2000
Naples 3 May 2011 Catherine TURON & Xavier LURI
P-L of Cepheids: universal or not ?
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Gaia will bring • an extensive sampling of Cepheids in the Galaxy • very accurate distances, colours and metallicity
The existence of a universal P−L relation of classical Cepheids is an only historically justified illusion Sandage et al, 2009
Recent robust estimates of the LMC distance and current results indicate that the Cepheid PL relation is not Universal
Romaniello et al. 2008
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. 2007
• 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
Naples 3 May 2011 Catherine TURON & Xavier LURI
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.
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Naples 3 May 2011 Catherine TURON & Xavier LURI
Estimated distance to the LMC from Hipparcos
Perryman 2009
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Naples 3 May 2011 Catherine TURON & Xavier LURI
Gaia LMC and SMC mean distance
• Number of objects observed • ~ 7 500 000 for LMC • ~ 1 500 000 for SMC
• Mostly faint objects, G ~ 19-20 and thus σπ ~ 300 µas (worst case) • Cepheids better ! • Distances
• ~ 48 000 pc for LMC → π = 20.8 µas • ~ 61 000 pc for SMC → π = 16.4 µas
• Averaging all individual parallaxes
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Mean parallaxes (depth not taken into account) for LMC
for SMC 34
Naples 3 May 2011 Catherine TURON & Xavier LURI
Gaia LMC and SMC individual distances
• Assuming a depth of 3000 pc (still a large uncertainty on the depths of LMC and SMC)
d = 45 000 – 51 000 pc for LMC → π = 22.2 – 19.6 µas d = 58 000 – 64 000 pc for SMC → π = 17.2 – 15.6 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
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Colour-magnitude diagrams in the Local Group
GAIA will observe individual stars in Local Group galaxies, with unambiguous discrimination with solar neighbourhood stars.
Sculptor (79 kpc)
V=20
Fornax (138 kpc)
V=20
Courtesy V. Hill
Naples 3 May 2011 Catherine TURON & Xavier LURI
The third dimension: further and further Solar neighbourhood Hubble, Ground-based
– Distances to ~ 50 pc Precision: 0.2 - 1 - 5 mas
Solar neighbourhood Hipparcos 1997 - 2007 – Distances to ~ 500 pc Accuracy: 0.1 - 0.2 - 2 mas
All over the Galaxy Gaia (2013-2018) – Distances to~ 10 000 pc Accuracy: 10 - 20 - 300 µas
In the Galactic Bulb Jasmine (?) – Distances to~ 10 000 pc Precision: 10 µas
In the Local Group Next generation space – Distances to~ 30 000 pc astrometry (> 2018) Precision: 1 µas
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