The Universe After Gaia Data Release 2

The Universe after Gaia Data Release 2

Eugene Vasiliev Institute of Astronomy, Cambridge

University of Z¨urich 4 October 2019 The Universe after Gaia Data Release 2

Eugene Vasiliev Institute of Astronomy, Cambridge

University of Z¨urich 4 October 2019

Alberto Giacometti, “Le Nez” Synopsis

Overview of the Gaia mission and DR2: scientiﬁc instruments, catalogue contents, measurement uncertainties, caveats and limitations.

Scientiﬁc highlights: Kinematic complexity of the disk Accretion history of the halo Search for new objects (streams, satellites) Internal kinematics of stellar structures Measurement of Milky Way gravitational potential Astrometry 101

Position on the sky α, δ Parallax $ = 1/distance Proper motion µα, µδ Line-of-sight velocity vlos Binary orbit parameters How Gaia astrometry works Overview of Gaia mission G I Scanning the entire sky every couple of weeks BP RP RVS I Astrometry for sources down to 21 mag I Broad-band photometry/low-res spectra I Line-of-sight velocity down to 15 mag (end-of-mission) ∼

[Source: ESA] Overview of Data Release 2 astrometry

I Based on 22 months of data collection 9 I Total number of sources: 1.69 10 RV × I Sources with full astrometry (parallax $, 9 proper motions µα∗, µδ): 1.33 10 × 9 I Colours (GBP , GRP ): 1.38 10 × I Line-of-sight velocities: 7.2 106 colours × 6 108 I Eﬀective temperature: 160 10 Teff ICRF3 prototype 107 vrad SSO × Variable Gaia DR1 6 Gaia-CRF2 Gaia DR2

n 6 Stellar parameters (R , L ): 77 10 i 10 b

I g × a 105 m

6 1 .

Extinction and reddening: 88 10 0 4

I 10 r e p

× 6 r 103 e Variable sources: 0.55 10 b I m 2 u 10 × N 101

100 5 10 15 20 25 Mean G [mag] [Brown+ 2018] Measurement uncertainties 10 parallax uncertainty [mas] 5 ] s a

m 2 [

Parallax: 0 05 0 1 mas ) $ . . $

& ¾

( 1

− x a l l

Proper motion: 0 1 0 2 mas/yr a 0:5 µ . . r

& a p

− n i 0:2 y Line-of-sight velocity: 0 5 km/s t V . n & i a t

r 0:1 e c n

u 0:05 d r a d n

a 0 02 t : RV measurements only for stars with S systematic error 0:01 Teﬀ [3500 6900] K and GRVS 12 (G 13) . 0:005 ∈ ÷ ≤ 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

] 10

1 G magnitude ¡ r

radial velocity uncertainty [km/s] y proper motion uncertainty [mas/yr] 5 s a m [ ) x

a 2 m ; m p

¾ 1 ( : m : 0:5 p n i e s

p 0:2 i l l e r

o 0:1 r r e f

o 0:05 s i x

a systematic error r o

j 0:02 a m ¡

i 0:01

systematic error m e 1 mas/yr = 4.7 km/s × (D/1 Kpc) S 0:005 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 [Katz+ 2018] G magnitude [Lindegren+ 2018] Gaia parallaxes and the absolute distance scale

Mean parallax of 5 × 105 quasars [Arenou+2018] 0:10 ¡63 0:08 ¡64 0:06 Compilation of parallax oﬀset measurements [Lindegren+2018b] ¡65 0:04 1.15 ¡66 ] H = s 0 a m ¡67 0:02 [ 1.10 80.5 x 95% a l l

¡68 a 0 r 99% a 1.05 76.9 p

¡69 n a ¡0:02 i d e

Declination[deg] 1.00 ¡70 73.2 M ¡0:04 Medianparallax [mas] ¡71 0.95 69.5 68% ¡0:06 95% Planck16+RCDM

¡72 rescale local distance 0.90 65.9 99% ¡0:08 ¡73 Red Giants 0.85 ¡0:10 100 95 90 85 80 75 70 65 60 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 Right Ascension [deg] parallax zeropoint (mas) Mean parallax of LMC stars [Lindegren+2018a] Cepheid distances and Planck constant [Riess+2018] The “golden” 6D sample 6 106 stars brighter than G 13 ∼ × ∼ 5 106 with parallax uncertainty $/$ 0.2 ≤ 4 106

3 106

2 106 Number of stars 106

0 0 2 4 6 8 10 Distance [kpc]

[Babusiaux+ 2018; Katz+ 2018] Kinematic complexity in the disk

I Moving groups in velocity space [Gaia Collaboration: Katz+2018] = more clearly seen in action space.⇒ I Bar pattern speed constraints [Monari+2018]

I Perturbations from spiral arms [Trick+2018] [Quillen+2018; Hunt+2018] I Tests of spiral structure theories [Sellwood+2018]

[Quillen+2018] [Monari+2018] [Sellwood+2018] Vertical perturbations and the disk seismology

Phase-space spiral [Antoja+2018] 10 perturbation from a (2 10) 10 M satellite − × crossing the disk 200 400 Myr ago (Sgr dSph?) − [Laporte+ 2018] [Darling & Widrow 2018] [Binney & Sch¨onrich2018] [Bland-Hawthorn+ 2018] [Li & Shen 2019] Radially-anisotropic population in the stellar halo 9 Evidence for a major merger with a 10 M satellite 8 10 Gyr ago & ∼ − Dispersion Anisotropy Rotation 200 1.0 80 (kinematics1<|z|<3 + metallicity) 3<|z|<5 [see also Kruijssen+20185<|z|<9 for globular clusters] 0.8 150 60

0.6 > e ` m 100 40

50 mr 20 0.2 me mq 0 0.0 0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 -3.5 -3.0 -2.5 -2.0 -1.5 -1.0 [Fe/H] [Fe/H] [Fe/H] [Belokurov+ 2018 – SDSS+Gaia DR1] [Mackereth+ 2019 – APOGEE+Gaia DR2]

[Helmi+ 2018 – APOGEE+Gaia DR2] [Fattahi+ 2018 – Gaia DR2] Radially-anisotropic population in the stellar halo 9 Evidence for a major merger with a 10 M satellite 8 10 Gyr ago & ∼ − (kinematics + metallicity) [see also Kruijssen+2018 for globular clusters]

[Mackereth+ 2019 – APOGEE+Gaia DR2]

Gaia–Enceladus

Helmi+ 2018 [Fattahi+ 2018 – Gaia DR2] Radially-anisotropic population in the stellar halo 9 Evidence for a major merger with a 10 M satellite 8 10 Gyr ago & ∼ −

Gaia–Enceladus

Helmi+ 2018 Belokurov+ 2018 Finding substructures with Gaia

90 ◦ 90 ◦ north south 15 ◦ -15 ◦ 135 45 45 135 ◦ 30 ◦ ◦ ◦ -30 ◦ ◦ 3 45 ◦ -45 ◦ 10

60 ◦ -60 ◦

75 ◦ -75 ◦

180 ◦ 90 ◦ 0 ◦ -90 ◦ 180 ◦ Sagittarius stream 102

SMC # of sources per square degree

225 ◦ 315 ◦ 315 ◦ LMC 225 ◦ 101

270 ◦ 270 ◦

Stars with $ < 0.3, 1 < GBP GRP < 1.5, µα < 3.5, µδ < 3.5 (mainly distant halo) − | | | | Finding streams with Gaia Finding streams with Gaia Finding streams with Gaia Finding streams with Gaia

GD-1 stream [Grillmair & Dionatos 2006] Finding new streams with Gaia

20 20

Phlegethon stream [Ibata+2018] 15 15

10 10 25 5 5

best fit orbital model ] ] c c p 0 p 0 k 30 k [ [ ] z y 1 30 5 5 ] r y g 10 10 e s d a [ 15 15 m b 35 [ 20 20 20 15 10 5 0 5 10 15 20 0 5 10 15 20 60 x [kpc] R [kpc]

proper motion selection 40

15 10 Padova 10Gyr, [Fe/H] = 1.4 best fit orbital model 10 Phlegethon 10

] 30 1 ]

5 1 r

y 0 r ] 12 s

0 y g a e s m [ d 5 a [ ] m b g 10 10 [

a 14 b m

6015 [ 15 0 proper motion selection G 16 20 20 60 30 0 30 ] 1 25 [deg] r y

s 30 a 18 m [ 35

40 20 45 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 3 (GBP GRP)0 [mag]

1 ] s a 0 m [

400 ] 1 200 s

m 0 k [ o i l e

h 200 v

400

60 40 20 0 20 [deg] A census of stellar streams in the Milky Way Stream name Ylgr Sylgr Fj¨orm Fimbulthul Phlegethon Styx Kwando [Ibata+2019] Murrumbidgee Chenab Indus Jhelum Nix Aliqa Uma Willka Yaku Turranburra Orinoco Wambelong GD-1

[C.Mateu, GalStream database] A census of stellar streams in the Milky Way Stream name Ylgr Sylgr Fj¨orm Fimbulthul Phlegethon Styx Kwando Nix [Ibata+2019] Murrumbidgee Chenab Indus Jhelum Nix Aliqa Uma Willka Yaku Turranburra Orinoco Wambelong GD-1

Styx [C.Mateu, GalStream database] Finding new satellite galaxies with Gaia: Antlia 2 Stellar Density CMD Proper Motions 15 8 5 16 6

17 yr) 4

/ 400

(deg) 0 18 2 (mas (mag) δ 0 δ 300 r ∆ All Stars 19 0 s) pm / 200 20 2 − -5 21 4 100 -5 0 5 0.5 0.0 0.5 1.0 1.5 − 5 0

− − HRV(km ∆α cos (δ) (deg) (g r)0(mag) pm α cos (δ) (mas/yr) 15 − 8 0 5 16 6 100 − 3 2 1 0 1.0 0.5 0.0 0.5 1.0 1.5 1.0 0.5 0.0 0.5 1.0 1.5

17 yr) 4 − − − − − − −

/ [Fe/H](dex) µα cos δ(mas/yr) µδ(mas/yr)

(deg) 0 18 2

(mas LMC δ (mag) 0 δ LMC r ∆ 17.5 17.5 19 0 − − Selected Stars pm 15.0 15.0 20 2 − − − Fornax Sgr dsph Fornax -5 Sgr dsph 12.5 12.5 21 4 − − -5 0 5 0.5 0.0 0.5 1.0 1.5 − 5 0 − − AndXIX ∆α cos (δ) (deg) (g r)0(mag) pm α cos (δ) (mas/yr) 10.0 LeoII 10.0 LeoII AndXIX Draco − − Draco − Sextans 15 40 Sextans 20.56 0.1 ± Cra 2 Ant 2 5 (mag) 7.5 Cra 2 Ant 2 (mag) 7.5 16 V − V − M M 17 30 5.0 5.0 − − 18 2.5 2.5 − − =1 19 20 (deg) 0 M/L (mag) δ MW galaxies 0

r Classical dwarfs ∆ 0.0 0.0 20 M31 galaxies LG galaxies = 100 = 1000 21 10 = 31 = 32 MW GCs 2.5 µ µ 2.5 M/L M/L 0 1 2 3 4 3 4 5 6 7 8 9 22 10 10 10 10 10 10 10 10 10 10 10 10 -5 rh(pc) M(r

A hard cutoﬀ in PM space is not always possible and is conceptually unsatisfactory. A more mathematically well-grounded alternative: gaussian mixture modelling.

f (µi ) = q (µi µcl, Σcl;i ) + (1 q) (µi µfg, Σfg;i ) N | − N | exp − 1 (µ−µ)T Σ−1 (µ−µ) (µ µ, Σ) 2 √ , N | ≡ 2π det Σ where the mean PMs µ and dispersions Σ of the cluster and foreground distributions, and the fraction of cluster members q, are all inferred by N Pstars maximizing the likelihood of the observed stellar PMs ln ln f (µi ). L ≡ i=1 Posterior membership probability for each star:

qcl(ri ) (µi µcl, Σcl;i ) pcl;i = N | qcl(ri ) (µ µ , Σcl;i ) + [1 qcl(ri )] (µ µ , Σfg;i ) N i | cl − N i | fg Internal kinematics of globular clusters

Rotation found in 10 20 clusters, ∼ − transverse velocity dispersion measured in 60 100 clusters (outer regions) ∼ −

[Bianchini+2018]

NGC 6266 (M 62) 20 0.6 N=447, D=6.4 kpc

] 0.5 15 r ] y / s / s a

0.4 m k m [ [

σ µ 10

σ ,

0.3 t , v t , µ r

v , r 0.2 µ 5 0.1

0.0 0 0 1 2 3 4 5 6 R [arcmin] [Baumgardt+2019] Internal kinematics of the Large Magellanic Cloud rotation, velocity dispersion from 106 stars at 50 kpc ∼

R [Kpc] 0 1 2 3 4 5 6 100

80 irc v c vφ ]

s 60 / m k [ σ

, 40 v σR, φ

20 σz

0 0 1 2 3 4 5 6 7 8 [credit: ESA/Gaia/DPAC] R [deg] Measuring 6d phase-space coordinates and orbits of Satellite galaxies Globular clusters eccentricity 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

400

350

300

250

200

150 Total velocity, km/s

100

0 1 10 100 Galactocentric distance, kpc

[Fritz+2018, see also Simon 2018; Pace & Li 2018; Massari & Helmi 2018] Distribution of globular clusters in action space

polar (Jφ =0)

NGC 6723 1 5 M 69 2 10 20 50 100

BH 229 NGC 6624 Rcirc [Kpc]

) ci 0 NGC 6342 rc inner Galaxy = M 80 ul J r NGC 6144 NGC 6522 a ( r outer Galaxy ESO452 ar (J ul r = rc NGC 6325 NGC 6539 0 ci ) NGC 6652 M 107

NGC 6362 Terzan 3

FSR 1735 NGC 6453 Pal 9 NGC 6139 M 12 M 19 NGC 6355 M 62 prograde NGC 6528 NGC 6569

NGC 6541 NGC 6401 Terzan 10 BH 261 M 55 NGC 6752

NGC 6352 M 70 NGC 6558 M NGC10 6397 NGC 6293 Ton 2 Terzan 4 NGC 6304 NGC 5927 NGC 6440 M 14 NGC 5053

NGC 6388 Terzan 12 NGC 6638 Pal 8 NGC 6540 NGC 6553

NGC 6287 retrograde NGC 6366 Pal 7 BH 184 NGC 6535 NGC 6316 Terzan 7 M 28 Terzan 8 NGC 5986 Pal 5 ω NGC 6760 C NGC 6642 e n NGC 6441 Arp 2 M 53 Terzan 2 ESO456 M 54 Pal 6 NGC 6749 NGC 6256 NGC 6712 NGC 5946 i NGC 6517 Terzan 5 n ) Whiting 1 - Terzan 9 p Terzan 6 0 la = n J z e Terzan 1 ( (J NGC 6380 ne NGC 5824 z = Djorg 1 la 0 NGC 6544 -p Pal 12 ) in NGC 5897 NGC 6235 NGC 4833 M 3

M 30 Pyxis

IC 4499 47 Tuc

NGC 6752E 3 M 4 NGC 6397 0 NGC 6356 Pal 11

NGC 288 M 13 Pal 1

NGC 7492 M 68 FSR 1716 NGC 5927 radial (J =0) M 71 φ M 15 BH 176 NGC 5466

NGC 6287 Pal 7 J → Pal 10 z NGC 6101 NGC 6496 NGC 4372 NGC 6284 polar NGC 3201 M 22

FSR 1758 NGC 5634 ω M 5

C M 9 e Pal 13 prograde n ESO280 M 92 NGC 6426

NGC 2298

Rup 106 Jφ NGC 362 180◦ inclination 0◦ NGC 6584 M 75

NGCM 126156 IC 1257 NGC 5286 M 2 Djorg 1 retrograde ← → NGC 4147

NGC 7006 NGC 4833 NGC 5694 NGC 6229

eccentricity M 72 NGC 6934 NGC 1851 NGC 2808 M 79 radialJ

r ← Pal 2 1 Distribution of globular clusters in action space

polar (Jφ =0)

NGC 6723 1 5 M 69 2 10 20 50 100

BH 229 NGC 6624 Rcirc [Kpc]

) ci 0 NGC 6342 rc inner Galaxy = M 80 ul J r NGC 6144 NGC 6522 a ( r outer Galaxy ESO452 ar (J ul r = rc NGC 6325 NGC 6539 0 ci ) NGC 6652 M 107

NGC 6362 Terzan 3

FSR 1735 NGC 6453 Pal 9 NGC 6139 Sagittarius M 12 M 19 NGC 6355 M 62 prograde NGC 6528 NGC 6569

NGC 6541 NGC 6401 Terzan 10 BH 261 M 55 NGC 6752 [Law&Majewski 2010, . . . ]

NGC 6352 M 70 NGC 6558 M NGC10 6397 NGC 6293 Ton 2 Terzan 4 NGC 6304 NGC 5927 NGC 6440 M 14 NGC 5053

NGC 6388 Terzan 12 NGC 6638 Pal 8 NGC 6540 NGC 6553

M 30 Pyxis

IC 4499 47 Tuc

NGC 6752E 3 M 4 NGC 6397 NGC 6356 Pal 11

NGC 288 M 13 Pal 1

NGC 7492 M 68 FSR 1716 NGC 5927 radial (J =0) M 71 φ M 15 BH 176 NGC 5466

NGC 6287 J Pal 7 Pal 10 z NGC 6101 NGC 6496 NGC 4372 NGC 6284 polar NGC 3201 M 22

FSR 1758 NGC 5634 ω M 5

C M 9 e Pal 13 prograde n ESO280 M 92 NGC 6426

NGC 2298

Rup 106 Jφ NGC 362 NGC 6584 radially M 75

NGCM 126156 IC 1257 NGC 5286 M 2 Djorg 1 retrograde NGC 4147 anisotropic

NGC 7006 NGC 4833 NGC 5694 Sequoia M 72NGC 6229 population NGC 6934 NGC 1851 NGC 2808 M 79 radial [Myeong+ 2019] [Myeong+ 2018, Jr Pal 2 Helmi+ 2018] Distribution of globular clusters in action space

Jackson Pollock, “Convergence” Kliment Redko, “Uprising” Swiss connection Swiss connection Constraining the Milky Way potential L 35 1.2 30 1.1 Previous Studies 25 Kochanek 1996

1.5 1.5 Kochanek 1996 (w/0 Leo I) 1.0 20 Wilkinson & Evans 1999 15 Sakamoto et al 2003 q 0.9 Battaglia et al 2005 10 Xue et al 2008 Gnedin et al 2010 0.8 5 Watkins et al 2010 Watkins et al 2010 (without Draco)

) ) 0 l l 1.0 1.0 o o McMillan 2011 s s 0.7 M M Deason et al 2012a 5 12 12 Deason et al 2012b 210 220 230 240 250 260 270 10 10 ( ( Kafle et al 2012 ) ) 1 R R Gibbons et al 2014 Vcirc(R ) [km s ] < < r r

( ( Gibbons et al 2014 M M EHW 2015 (with DGs) 300 Kupper et al 2015

0.5 0.5 McMillan 2017 Watkins et al 2018 (Gaia) 250 Watkins et al 2018 (Gaia + HST) ]

Posti & Helmi 2018 1 200 Sohn et al 2018 halo s Malhan & Ibata 2018 (GD 1, Gaia) m 150

Vasiliev 2018 k Vasiliev 2018 (at 80kpc) [

c disk r 0.0 0.0 i c 100 0 50 100 150 0 50 100 150 V R (kpc) R (kpc) 50 bulge

0 0 5 10 15 20 25 Globular cluster dynamics R [kpc]

[Eadie & Juric 2018; see also Watkins+2018; Posti & Helmi 2018] GD-1 stream [Malhan & Ibata 2018] Constraining the mass of the Large Magellanic Cloud

5d kinematics of the Orphan stream deﬂected by LMC ﬂyby [Erkal+2018] Summary

The Universe is even more exciting after Gaia DR2!

Credit: Amanda Smith, IoA