a Galaxy model and Gaia DR1 A.C. Robin Institut UTINAM, OSU THETA, - PowerPoint PPT Presentation

Preliminary comparisons between a Galaxy model and Gaia DR1 A.C. Robin Institut UTINAM, OSU THETA, Besançon Coll. C. Reylé, S. Diakité, O. Bienaymé, J. Fernandez-Trincado, R. Mor, F. Figueras, etc. 1

Outline • Introduction • Population synthesis approach • Preliminary star count comparisons : DR1 tests for completeness • RAVE+TGAS synergy: Constraints on the disc kinematics • Perspectives 2

Gaia • Revisiting our understanding of Galaxy formation and evolution • 6D space explored for hundreds of million stars, 4D for 2 billion stars Gaia challenge : Find efficient methods to analyse and interpret data in terms of Galaxy evolution & dynamics

• Estimates for the density of detected stars (GUMS10)

• artiste’s view of the MW from top • => Gaia will revolutionize this view (at least for a quarter of the Galactic plane)

Population Synthesis Modelling • Population synthesis approach: many parameters but more understanding • Statistical treatment : no individual distances and ages, but for groups of stars • Link between scenarios and observations • Increasing complexity (start simple…) • Confronted to many observables : magnitudes, colors (many bands), proper motions, radial velocities, Teff, logg, [Fe/H],[alpha/Fe], asterosismic paramaters in the future 6

New Besançon Galaxy model Czekaj et al, 2014 Robin et al, 2014 Bienaymé et al 2015 Lagarde et al 2017 Binarity included ϕ (Teff, logg) for a thin disc decreasing SFR over 10 Gyr Mor et al, 2016 3D Extinction model (Mashall et al, 2006)

Comparison to bright star counts Tycho-2: V T < 11.5 BGM Mor et al, 2016 => Good at |b|>10° But Need for a better extinction model (low distances) at |b|<10°

Comparisons with DR1 Relative differences between Gaia-DR1 and BGM (GOG18) in magnitude bins 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.8 0.8 0.8 0.8 0.8 0.8 0.8 0.8 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.6 0.4 0.4 0.4 0.4 0.4 0.4 0.4 0.4 RelDiff15 RelDiff14 RelDiff16 RelDiff17 RelDiff18 RelDiff19 RelDiff13 RelDiff12 0.2 0.2 0.2 0.2 0.2 0.2 0.2 0.2 120, 120, 120, 120, 120, 120, 120, 120, 240, 240, 240, 240, 240, 240, 240, 240, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 0 0 0 0 0 0 0 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.2 -0.4 -0.4 -0.4 -0.4 -0.4 -0.4 -0.4 -0.4 -0.6 -0.6 -0.6 -0.6 -0.6 -0.6 -0.6 -0.6 -60, -60, -60, -60, -60, -60, -60, -60, -60, -60, -60, -60, -60, -60, -60, -60, -0.8 -0.8 -0.8 -0.8 -0.8 -0.8 -0.8 -0.8 -1.0 -1.0 -1.0 -1.0 -1.0 -1.0 -1.0 -1.0 12<G<13 13<G<14 14<G<15 15<G<16 16<G<17 17<G<18 18<G<19 19<G<20

Tests for completeness Arenou et al, 2017, A&A 599, A50

Disc kinematics: RAVE + TGAS • Complementarity between RAVE & Gaia-DR1 (TGAS): radial velocities + proper motions • RAVE based on Tycho-2 : I<12 • TGAS p.m. 1st epoch from Tycho-2 • RAVE simple selection function (random subsets) • However TGAS incomplete at V T >10.5 19

RAVE selection test • BGM simulation applying Resulting Teff / logg RAVE selection function on I magnitude x10 4 1.4 1.2 1.0 Count 2000 0.8 0.6 1800 0.4 1600 0.2 1400 0.0 Count 1200 3000 3500 4000 4500 5000 5500 6000 6500 7000 7500 8000 8500 9000 TeffS 1000 800 x10 4 600 1.0 0.9 400 0.8 200 0.7 0 Count 0.6 9.0 9.5 10.0 10.5 11.0 11.5 12.0 0.5 0.4 0.3 0.2 0.1 0.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 loggS

Galactic dynamics Bienaymé et al 2015 • To obtain self-consistent distribution functions : Determine third integral of motion. • Approximate potential of the BGM with a Stäckel potential=> Fitting orbits to obtain the Stäckel parameters => 3rd integral • Compute potential, vertical and radial forces self- consistently • Describe the asymmetric drift as a function of Rgal, Zgal

Bienaymé et al 2015 Meridional projection of 3 orbits 350 Caldwell+ (1981) Model 1 Sofue2015 Model 2 300 V 250 V (km/s) Envelop of the orbits (analytical) 200 150 0 5 10 15 20 0 20 R (kpc) R (kpc) Surfaces of section Good Stäckel approximation (<1%) for a wide Galactic range (3<Rgal<12 kpc, -6<Zgal<6 kpc)

Kinematical model Kinematics of each star computed (in heliocentric reference frame) from • Galactic rotation curve (from potential) • Asymmetric drift (from potential) • Solar motion (3 free parameters) • Age - velocity dispersion relation (3-4 free parameters) • Radial velocity gradients (2 free parameters) • Vertex deviation (2 free parameters)

Asymmetric drift Older stars rotated slower than young stars and gas Mihalas (1968) density gradient velocity disp. gradient Generally assumed to be the same out of the plane, but not the case in reality (Binney et al, 2010,2012), Bienaymé et al 2015)

In this self-consistent dynamical model Dependency of the asymmetric drift with R and z Old thick disc 160 140 120 100 100 Vlag km/s 90 80 80 60 70 40 60 Vlag km/s 20 50 0 40 0 1 2 3 4 5 6 Zgal (kpc) 30 Young thick disc 20 10 0 2 4 6 8 10 12 Rgal (kpc) Thin discs

Kinematical constraints at the Solar neighborhood • Simulating the RAVE survey selection function, radial velocities • Gaia TGAS : accurate proper motions for the RAVE stars • Separate stars by metallicity (4 bins) and by temperature (cool/hot) • |b|>25° to avoid extinction problems (and complex selection function) • Fit kinematic model for the thin and thick discs (ABC-MCMC) Robin , Bienaymé , Reylé , Fernandez - Trincado , 2017, 2017 arXiv 170406274 R Solar motion Solving for Thin disc velocity dispersion as a fct of age Thick disc velocity ellipsoid Kinematical gradients 26

Age-velocity dispersion relation in the local thin disc 50 Gomez et al 1997 2009 Holmberg Sharma+2014 Bovy+2012 40 Fit (1) Fit (2) Fit (3) Sigma W (km/s) 30 20 10 0 0 2 4 6 8 10 Age (Gyr)

x10 -2 9 8 7 Normalised count 6 Hot: solid 5 cool: dashed 4 3 2 Data 1 Model 0 -150 -100 -50 0 50 100 150 HRV V los 0.22 0.20 0.20 0.18 0.18 0.16 0.16 Normalised count Normalised count 0.14 0.14 0.12 0.12 0.10 0.10 0.08 0.08 0.06 0.06 0.04 0.04 0.02 0.02 0.00 0.00 -50 -40 -30 -20 -10 0 10 20 30 40 50 -50 -40 -30 -20 -10 0 10 20 30 40 50 pmra pmdec pm dec pm ra

-1.2<[Fe/H]<-0.8 -0.8<[Fe/H]<-0.4 -0.4<[Fe/H]<0 0<[Fe/H]<0.4 Cool stars 18 120 450 180 -45<l<135 -70<b<-40 16 400 160 100 14 350 140 12 80 300 120 10 250 100 60 8 200 80 6 40 150 60 4 100 40 20 2 50 20 0 0 0 0 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 HRV HRV HRV HRV 18 80 300 120 225<l<315 -70<b<-40 16 70 250 100 14 60 12 200 80 50 35 180 900 700 10 40 150 60 -45<l<135 -70<b<-40 160 800 8 30 600 30 140 700 6 100 40 25 500 20 120 600 4 50 20 20 400 10 100 500 2 80 400 0 0 15 0 0 300 60 300 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 10 200 40 200 HRV HRV HRV HRV 5 100 20 100 0 0 0 0 4 25 90 45 135<l<225 -70<b<-40 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 80 40 3.5 20 HRV 70 HRV 35 HRV HRV 3 60 30 2.5 15 25 140 700 500 50 25 2 225<l<315 -70<b<-40 450 40 20 120 600 10 1.5 20 400 30 15 100 500 350 1 20 10 5 15 300 80 400 0.5 10 5 250 0 0 0 60 0 300 10 200 -150-100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 150 40 200 5 100 HRV HRV HRV HRV 20 100 50 0 0 0 0 7 45 180 100 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 90 40 160 6 80 35 HRV 140 HRV HRV HRV b<-70 5 70 30 120 60 4 14 60 300 180 25 100 135<l<225 -70<b<-40 50 160 20 80 3 12 50 40 250 140 15 60 30 2 10 40 200 120 10 40 20 1 8 100 5 20 10 30 150 80 0 0 6 0 0 20 100 60 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 4 40 HRV HRV HRV HRV 10 50 2 20 0 0 0 0 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 HRV HRV HRV HRV 20 140 600 400 350 120 500 hot stars > 5200K b<-70 15 300 100 400 250 80 10 300 200 60 150 200 40 5 100 100 20 50 0 0 0 0 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 -150 -100 -50 0 50 100 150 200 29 HRV HRV HRV HRV