2.5

Gerry Gilmore

1 The IoA team

+ Edinburgh, Leicester, MSSL, RAL, Italy, Spain Gaia Science case proposed vs today

3 GAIA Accuracies and our Galaxy

10 µas = 10% distances at 10 kpc 10 µas/yr = 1 km/sec at 20 kpc Sanna etal 2017 Science in press

Gaia

The goddess who came into being after Chaos and generated the starry sky (Hesiod, Theogony 116/117 and 126/127) a contrast to the unintelligible and generator of the explorable

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 The heart of Gaia is a large Work started ~1993 camera array, 1 giga-pixel, Project approved 2000 sending us a video of the Operations start 7/2014 sky for 5-9 years. 5-9.5 years data Project end 2026+ The imaging data is being Total cost 960M€ processed in Cambridge.

Gaia data processing develops “Big Data” technologies and training Absolute astrometry One field gives only relative measures  model dependency Two fields break the degeneracy allows absolute measurements. Combining data at the limits of accuracy is not trivial!

Single field astrometry Two field astrometry8 Photometric processing at DPCI Cambridge

Flux calibration Evans etal 1701.05873

05/06/2014 9 astrometric data reduction • 1013 individual position measurements • 1010 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 • 6 processing centres

Gaia records a pixel-flux at a measured time Need spacecraft position, attitude, velocity, structure … to convert time to sky coordinate  Special, General Relativity are dominant terms

10 Gaia is a superb instrument with some real-world complexity • Scattered light – mitigated through optimising and mission extension, plus SIMBEL Heating cleans the mirrors

• Ice on mirrors: heaters

• Micro-clanks

• Basic-angle variations • Amplitude (1mas) =1/10 He atom

11

The inverse of a parallax ...

• Mean, median, mode, rms of a trigonometric distance – Consider a given true parallax p – Distance D=1/p [error distribution of 1/negative] • Recipe to avoid scientific trouble: – Always use forward modelling to measured parallaxes to fit higher-level unknown quantities – In other words: Do not use derived quantities like individual distances or absolute magnitudes to fit higher-level unknown quantities

GAIA: Key Science Objectives • 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 ⇒ Origin, Formation and Evolution of the Galaxy Stellar Astrophysics

• Comprehensive luminosity calibration, for example: – distances to 1% for 18 million stars to 2.5 kpc – distances to 10% for 150 million stars to 25 kpc – rare stellar types and rapid evolutionary phases in large numbers – parallax calibration of all distance indicators e.g. Cepheids and RR Lyrae to LMC/SMC

• Physical properties, for example: – clean Hertzsprung-Russell sequences throughout the Galaxy – solar neighbourhood mass function and luminosity function e.g. white dwarfs (~200,000) and brown dwarfs (~50,000) – initial mass and luminosity functions in star forming regions – luminosity function for pre main-sequence stars – detection and dating of the oldest (disk and halo) white dwarfs Pleiades

NGC2547

Testing stellar evolution

17 Gaia plus Gaia-ESO: combining parallax and to clean CMDs

Black: TGAS stars Blue: literature cluster members Randich etal Red: cleaned cluster members Gaia plus Gaia-ESO : combining parallax and proper motion to clean CMDs Comparing optimally-fit isochrones NGC2516: 5-sigma parallax shift, PARSEC (top) & MIST (lower) 80-120Myr age shift

www.gaia-eso.eu Astrophysical complexity becomes evident in precise data Gamma velorum cluster is an anomaly: the central massive is too massive for such a small cluster. NGC2547, 2deg away, shows Kinematic complexity gamma-vel 2nd population

Sacco etal 2016

Jeffries etal 2016

Stellar evolution challenge: Li-age & CMD age disagree Astrophysical complexity becomes evident in precise data

NGC2264 – a case study in complexity

Variable extinction, age range

Mass and age segregation

www.gaia-eso.eu GAIA: Discoveries of Extra-Solar Planets

• Large-scale detection and physical characterisation • 30,000- 70,000 giants to 150-200 pc e.g. 47 UMa: astrometric displacement 360 µas • complete census of all stellar types (P = 2-9 years) • masses, rather than lower limits (m sin i) • orbits for many (≈5000) systems • relative orbital inclinations for multiple systems

• mass down to 10 MEarth to 10 pc Gaia is providing a survey of NEO-threat asteroids with orbits interior to Earth and improved orbits for many main-belt asteroids, with many masses, radii,…

NEO/Atira Earth-crossing?

Spectrophotometry classifies asteroids Track for Triton occultation 05/10/17 Occultation of a Gaia star by the ringed asteroid Chariklo, 22/6/17 Cepheids & RRLyrae

Cepheids

RR Lyrae

05/06/2014 24 Dark energy?

Gaia image of stars in M33 Galaxies, Quasars, and the Reference Frame

• Parallax distances, orbits, and internal dynamics of nearby galaxies • Galaxy survey, including large-scale structure • ~500,000 quasars: kinematic and photometric detection • ~100,000 supernovae

• ΩM, ΩΛ from multiple quasar images (3500 to 21 mag) • Galactocentric acceleration: 0.2 nm/s2 ⇒ ∆(aberration) = 4 µas/yr • Globally accurate reference frame to ~0.4 µas/yr 1709.08975 1709.08976 Lensed quasar search Multiple Gaia detections: PG1115+080 QSO candidates from large-area surveys (SDSS + Pan-STARRS)

Resolved by Gaia into multiple components = possible lenses

Compare flux and positions HST SDSS between Gaia and SDSS Single Gaia detection: H1413+117 G = 17.22, Gsynth = 16.54 Gaia-SDSS offset = 0.53”

Missing flux + shifting centroids of quasars = possible lenses

HST SDSS Slide from Cameron Lemon 24 confirmed gravitationally lensed quasars

10 binary quasars Slide from Cameron Lemon z = 3.34 quasar with ~350 pc host galaxy Pan-STARRS gri Keck NIRC2 K-band PSFs+galaxies subtracted

G2 D

A G1

E B

C

3 Gaia detections 5 quasar images quasar host galaxy 2 lensing galaxies stretched into an arc General Relativity/Metric

• From positional displacements: – γ to 5×10-7 (cf. 10 -5 presently) ⇒ scalar-tensor theories – effect of Sun: 4 mas at 90o; Jovian limb: 17 mas; Earth: ~40 µas • From perihelion precession of minor planets: – β to 3×10-4 - 3×10-5 (×10-100 better than lunar laser ranging) -7 -8 – Solar J2 to 10 - 10 (cf. lunar libration and planetary motion) • From white dwarf cooling curves: – dG/dT to 10-12 - 10-13 per year (cf. PSR 1913+16 and solar structure) • Gravitational wave energy: 10-12 < f < 10-9 Hz • Microlensing: photometric (~1000) and astrometric (few) events • Cosmological shear and rotation (cf. VLBI) Gaia and Gravitational waves

Polarization test of gravity GAIA Observatory: Early Science

• Continuously throughout the mission: – broad-band photometry – medium-band photometry https://gaia.ac.uk – radial velocity spectroscopy => VARIABLES, INTERESTING OBJECTS, SOLAR SYSTEM SOURCES, SUPERNOVAE,… ⇒ A REAL-TIME VIDEO OF THE SKY at 0.1arcsec resolution... Gaia14aae, ASASSN-14cn

Gaia EPSL

Enrique de Miguel Campbell et al. 2015 Ma g

Loiano Observatory min Gaia spectrophotometry 350 – 1020nm

CU8: Delchambre 2017 arXiv:1709.09378 Gaia16aeg=ASASSN-15lv Very fast transits can be found – dM flares in this case

“parasitic sources” from the 2nd FOV Wevers PhD thesis 2017 Stellar microlensing: about 20 events, incl

Standard events limit dark (BH) companions

Get the GaiaAlerts smartphone App! Stellar microlensing: about 20 events, incl Gaia16aye

DR1 Planetary Nebulae: increase in dynamic range, new physics?

ionized mass–inverse size vs surface brightness surface brightness relation

Blue points = literature, red = new Gaia DR1 data

The Gaia Data Release 1 parallaxes and the distance scale of Galactic planetary nebulae LetiziaStanghelliniaBeatriceBucciarellibcMario G.LattanzibRobertoMorbidellib newast.2017.06.004 Local dark matter density: will Gaia make a difference?

McKee etal 2015

Figure 2 from The local dark matter density J I Read 2014 J. Phys. G: Nucl. Part. Phys. 41 063101 doi:10.1088/0954-3899/41/6/063101 Systematic large scale motions in the Galactic disks interior “breathing mode”, exterior “bending mode” Vr - Vphi Vr - Vz Vphi - Vz Typical parallax precision G=15 30 muas, G=18 150muas G=20 700muas Photometry limits <2mmag Radial velocity 400m/s 5

Sgr 1 window (l,b)=(0,-2). 0.6deg, 2.8million stars Gaia DR2 colours The people behind Gaia Gaia Statistics @ 05-Oct-2017 13:15 UT

during this talk Gaia measured ≈3,000,000 objects (…including 0.5M spectra, 6M photometry, 25M astrometry points) https://gaia.ac.uk get the app! http://www.cosmos.esa.int/web/gaia 46