building the cosmic distance scale: from hipparcos to gaia · building the cosmic distance scale:...

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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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, …


See talks by Jos de Bruijne, Laurent Eyer and Eduardo Masana for more details about

the performance of Gaia

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Field stars

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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


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)


From Hipparcos to Gaia

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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


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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Gaia: stellar population sampling

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Thin disk Thick disk Halo Bulge

σπ/π < 10% at V=15


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!


Open clusters

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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)


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)


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)


Hyades from trigonometric parallaxes

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Gaia

2020

Sol

1960

Hipparcos

1990 Courtesy M. Perryman


Hipparcos-2: nearby open clusters

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van Leeuwen 2009

Hyades Hyades Hyades

Coma Ber Pleiades

Praesepe Coma Ber

Pleiades UMa


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


Globular clusters

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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


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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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


Gaia photometry standard error per Field of View transit

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Courtesy J. de Bruijne (ESA)


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


Cepheids

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δ Ceph (Hipparcos) Cepheids in M31 (Gaia)

3.8

4.0

4.2

Hp .6

.8

1. BT-VT


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


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


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


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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Magellanic Clouds and Local Group Galaxies

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Estimated distance to the LMC from Hipparcos

Perryman 2009

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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


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


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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building the cosmic distance scale: from hipparcos to gaia · building the cosmic distance scale:...

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