Gaia. Stereoscopic Census of our Galaxy. one billion pixels for one billion stars

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1 Gaia Stereoscopic Census of our Galaxy one billion pixels for one billion stars one percent of the visible Milky Way Gerry Gilmore, UK Gaia PI, on behalf of DPAC 1

Gaia: the goddess who created the universe and knowledge Gaia is transformational the first 3-D galaxy

spectrophotometry, Teff, log g, Av, [Fe/H], binarity, planets, periods for variables, Launch: 12/2013

5 years data Project end: 2023+ Total cost: 960M The heart of Gaia is a large camera array, 1

The imaging data is being processed in Cambridge. 4 billion transits processed so far 2 telescopes, 1.

2 Gaia: the goddess who created the universe and knowledge Gaia is transformational the first 3-D galaxy precision distances and motions for 1 billion stars Astrometry, photometry, spectroscopy, spectrophotometry, Teff, log g, Av, [Fe/H], binarity, planets, periods for variables, Launch: 12/2013 Work started: ~1993 Project approved: 2000 Operations start 7/ years data Project end: Total cost: 960M The heart of Gaia is a large camera array, 1 giga-pixel, sending us a video of the sky for 5-8 years. The imaging data is being processed in Cambridge. 4 billion transits processed so far 2 telescopes, 1.45 x 0.5 m primary, monolithic SiC optical bench, 0.06arcsec pixels Data flow: 50Gb/day for 5-8 years; total processed data and archives 1PByte Computational challenge : 1.5 x 10²¹ FLOP and highly sophisticated algorithms

3 GAIA: Key Science Objectives Origin, Formation and Evolution of the Galaxy Structure and kinematics of our Galaxy: shape and rotation of bulge, disk and halo internal motions of star forming regions, clusters, etc nature of spiral arms and the stellar warp space motions of all Galactic satellite systems Stellar populations: physical characteristics of all Galactic components initial mass function, binaries, chemical evolution star formation histories Tests of galaxy formation: dynamical determination of dark matter distribution reconstruction of merger and accretion history Revolutionary science from solar system to cosmology planets, cosmology, fundamental physics, NEOs,.. This broad range of topics allows a range of follow-up transients, detailed studies, rare objects, outreach,... but most of the science case requires statistics!

4 What will Gaia see as stars move? These are real Hipparcos observations 47 UMa Gaia accuracy 10 to 100 times better Trend: stellar orbit Galactic dynamics, dark matter, assembly history,... Cycloid: parallax = 1/distance Galactic structure, star formation history Loops: high frequency motion massive planetary systems 4

5 What does micro-arcsecond mean? Precision: 50pico-rad, human hair at 1000km, coin on the moon Astrometry needs more than signal to noise and image processing One must have a physical model and understanding of every contribution to the error budget at an appropriate level Einstein light bending at the Sun s edge is 1,750,000 microarcsec One mu-as is the limit to which we have tested GR For Gaia the spin rate is controlled to 15 ppm The spacecraft distance is known to a few metre (at 1.5 Million km) The spacecraft speed is known to a few mm/s On-board interferometer measures mirror locations to picometre level every few seconds a helium atom is 30picometre clocks, pixel substructure -- and very much more 400 people are busy with the data processing and analysis 5

6 Gaia 5-year parallax standard error complete to G=0, with poorer standard error Calibration floor

7 How does Gaia work?: Sky Scanning Principle Observe sky with two telescopes Precision: 50pico-rad, human hair at 1000km, 2cm on the moon...

8 Gaia is a simple 2-telescope optical bench

9 Absolute astrometry One field gives only relative measures model dependancy Two fields break the degeneracy allows absolute measurements. Combining data at the limits of accuracy is not trivial! Single field astrometry Two field astrometry 9

10 Why rectangular? two-telescope scanning mission is optimal. Since across-scan data is much less important, can save mass and use rectangular mirrors

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12 Gaia science data flow: 5,000 stars/second on average

13 The astrometric data reduction individual position measurements unknowns based on physical models all connected - must be determined simultaneously a vast modelling and parameter adjustment problem Iterative, self-calibrating, needs GR metric 5000 million star unknowns (for simple stars) 150 million attitude unknowns 50+ million calibration unknowns a few dozen global unknowns DPAC involves 400 people and 6 processing centres Eg, photometric ubercalibration: Another order of magnitude to 13 improve, but we are on the way

14 CCDs, electronics, clocks, communications, spacecraft control, functioning nominally Higher L2 dust environs will gently sand-blast JWST s mirror. Complete sky survey from 0 < G > 20 Mission extension from 5 years to 7.5 years under analysis 05/06/2014 IoA Seminar 14

15 Heating cleans the mirrors 05/06/2014 IoA Seminar 15

16 Scattered Light (RVS): mean level 30x expected adds noise to faint sources astrometry recovered by mission extension Astronomical sources Sunlight diffracted around sunshield 6 hour period = Gaia s spin period RVS is delivering 60million spectra, R=11,000, complete to V<15.3

$Sunlight diffracted around sunshield 6 hour period = Gaia s spin period RVS is delivering 60million spectra, R=11,000, complete to V<15.3$

17 Scattered Light (RVS): mean level 30x expected adds noise to faint sources astrometry recovered by mission extension Astronomical sources Sunlight diffracted around sunshield 6 hour period = Gaia s spin period RVS is delivering 60million spectra, R=11,000, complete to V<15.3

Gaia Performance (at In Orbit Commissioning Review)

int/web/gaia/science-performance Astrometric Performance

units=mmag Plus Spectro-Photometry, T_e, log g, A_v,

18 Gaia Performance (at In Orbit Commissioning Review) Astrometric Performance Complete sky survey 0 < G > 20 Photometric Performance: units=mmag Plus Spectro-Photometry, T_e, log g, A_v, light curves, variability, [Fe/H] for 1 billion sources Spectroscopic Performance: 60 million RVs

19 What s the science? Part 1 Proper motions of 20 muas/a: (V=15) 20 muas/a = 10 m/s at 100 pc, i.e. planets can be found at half a (M V =+10) million stars (Jupiter moves the sun by 15m/s) 20 muas/a = 1 km/s at 10 kpc, i.e. even the lowest-velociy stellar (M V =0) populations can be kinematically studied throughout the entire galaxy 20 muas/a = 5 km/s at 50 kpc, i.e. the internal kinematics of the (M V =-3.5) Magellanic clouds can be studied in as much detail as the solar neighbourhood can be now (5 km/s = 2.5 mas/a at 400 pc!) 20 muas/a = 100 km/s at 1 Mpc, i.e. a handful of very luminous (M V =-10) stars in M31 will show the galaxy s rotation 19

20 Parallaxes of 20 muas: (V=15) 20 muas = 1 percent at 0.5 kpc, i.e. 6-dimensional structure of the Orion complex at 2pc depth resolution 20 muas = 10 percent at 5 kpc, i.e. direct high-precision distance determination of even very small stellar groups throughout most of the Galaxy 20 muas = 100 percent at 50 kpc, i.e. a direct distance determination of the Magellanic clouds is at the edge Linear sizes of 20 muas: (V=15) 20 muas = 1 solar diameter at 0.5 kpc, i.e. normal sunspots do not disturb the measurements, but Jupiters do, structure on giants, 20 muas = 1 AU at 50 kpc, the limit of parallax measurements

21 Gaia is providing a survey of NEO-threat asteroids with orbits interior to Earth and improved orbits for many MB asteroids, with many masses, radii, Best ground > mas accuracy Orbital accuracy NEO/Aten/Apollo (Chelyabinsk!) Main belt asteroid Gaia

Planetary systems Gaia will find some transiting systems, but the real value is definition of volume-complete stellar parent samples, plus direct astrometric discovery, and mass determinations, of

22 Planetary systems Gaia will find some transiting systems, but the real value is definition of volume-complete stellar parent samples, plus direct astrometric discovery, and mass determinations, of nearby non-eclipsing jupiters. These will be ideal for follow-up direct coronographic imaging RV Jupiters are easy astrometric detections Astrometric signature Period (yr) Perryman etal 2014 arxiv:

23 Stellar evolution, young stars, rare objects, Galactic structure, SFR(t) 3 23

24 Stellar populations Gaia manages most of the sky uncrowded ~HST spatial resolution At LMC 20muas/yr=5km/s Omega Cen: 140K stars, 1min data

25 Cosmological distance scale calibration at mmag level 25

26 26

27 Gaia will repeat the Eddington 1919 light-bending test 100 years later, with 100,000 times higher precision General Relativity/Metric Gaia will measure light bending by Jupiter to test GR From positional displacements: γ to (cf presently) scalar-tensor theories effect of Sun: 4 mas at 90 o ; Jovian limb: 17 mas; Earth: ~40 µas From perihelion precession of minor planets: β to ( better than lunar laser ranging) Solar J 2 to (cf. lunar libration and planetary motion) From white dwarf cooling curves: dg/dt to per year (cf. PSR and solar structure) Gravitational wave energy: < f < 10-9 Hz Microlensing: photometric (~1000) and astrometric (few) events Cosmological shear and rotation (cf. VLBI) 27

28 Gaia is a transient explorer High-resolution transient photometry and spectro-phot Sky sampling for nominal 5-year mission Some examples from 1-month ecliptic pole high sampling 28

29 SN Gaia14aaa: correct deduction of type, age, redshift Images from Liverpool Telescope Gaia discovery photometry Gaia discovery spectrophotometry 29

30 Gaia science has started! This will support a big outreach & education programme w. Las Cumbres few 1000 local SNe

31 The Gaia Data Release (GDR) Scenario GDR1 ~7/16: positions, G-magnitudes (~all sky, single stars) proper motions for Hipparcos stars (~50 µarcsec/yr) the Hundred Thousand Proper Motions (HTPM) catalogue GDR2 ~2/17: + radial velocities for bright stars, two band photometry and full astrometry (α, δ, ϖ, μ α, μ δ ) where available for intermediate brightness stars GDR3 ~1/18: + first all sky 5 parameter astrometric results (α, δ, ϖ, μ α, μ δ ) BP/RP data, RVS radial velocities and spectra, astrophysical parameters, orbital solutions short period binaries GDR4 ~1/19: + variability, solar system objects, updates on previous releases, source classifications, astrophysical parameters, variable star solutions, epoch photometry GDR-Final: final data release (thus in 2022/23 or 2025) Full dataset for more sophisticated modelling released at end of mission 31

34 We have Gaia! We want more Gaia will provide 60 million spectra to V=15.2 Many ambitious ground-based projects plan to complement the Gaia astrometry Weave, 4most + AAT, lamost, US eg MOONS contract signed 25/09 One precursor is the Gaia-ESO Spectroscopic Survey 34

through ESO completed 25+ refereed papers published or in late draft (+archive) Big ESO DR2 due in a few months http://gaia-eso.

35 Gaia-ESO Survey 300+ VLT-night survey of Galaxy stellar pops Co-PIs Gerry Gilmore, Sofia Randich +400 Co-Is, 90+ Institutes across all ESO 19 Working Groups active wiki internal communications views/day ~110 Co-I science projects listed in wiki DR1 data release through ESO completed 25+ refereed papers published or in late draft (+archive) Big ESO DR2 due in a few months (public survey pages) (public archive)

36 Gaia-ESO core philosophy Involve all spectroscopic analysis methods Identify the dominant systematic variables, and fix them version control Analyse spectra through all interested groups In principle, this allows us to identify both systematic method errors and random errors parameter +/- random +/- systematic 36

37 Gaia-ESO Giraffe spectra even with narrow target selection, a very wide range of parameters is evident there is no single analysis aproach

38 summary Gaia is working. First science alerts are appearing now. Data will be good. Gaia-ESO is working. First science is good. The sociology in astronomy is changing, towards data free to everyone- you! Realising the Gaia potential provides huge opportunities to extend our community, as well as our knowledge Its worth the considerable effort. 38

41 Is there a thin-thick difference in alpha/fe DF? Furhmann was there first careful, single method approach Fuhrmann MNRAS (2011) Recent fuss from SDSS about (lack of) complexity in disk chemistry-kinematics Disagreed with available high-resolution studies: issue was biases, need survey

42 Clear bimodality between thick and thin disks

Gaia. Stereoscopic Census of our Galaxy. one billion pixels for one billion stars

Gaia. Stereoscopic Census of our Galaxy. one billion pixels for one billion stars Gaia Stereoscopic Census of our Galaxy http://www.cosmos.esa.int/web/gaia http://gaia.ac.uk one billion pixels for one billion stars one percent of the visible Milky Way Gerry Gilmore FRS, UK Gaia PI,