Gaia s view of star clusters

Transcription

1 Gaia s view of star European Space Agency 15 November #GaiaMission Figure courtesy ESA/Gaia/DPAC

2 Gaia s first sky map Figure courtesy ESA/Gaia/DPAC

3 Gaia s first sky map Figure courtesy ESA/Gaia/DPAC

4 Promises q No equations q Light on acronyms q Watch a video q Quiz q Reveal secret q Lots of data (April 2018) Figure courtesy ESA/Gaia/DPAC

5 Contents q Gaia q Gaia DR1 q Globular clusters q Open clusters(+ dwarf galaxies) q The Hyades q Gaia DR2 q Conclusions Figure courtesy ESA/Gaia/DPAC

6 Contents q Gaia q Gaia DR1 q Globular clusters q Open clusters(+ dwarf galaxies) q The Hyades q Gaia DR2 q Conclusions Figure courtesy ESA/Gaia/DPAC

7 Sebastien: We study comets because they have preserved the original building blocks of the Solar system A Milky Way look-alike Gaia s main aim: unravel the structure, formation, composition, and evolution of our Galaxy Key: stars, through their motions and chemical composition, contain a fossil record of the Galaxy s past evolution Figure courtesy European Southern Observatory (NGC1232) 7

8 The need for Gaia q Archaeological studies of the Galaxy require: q Distances and motions, combined with physical properties of stars (temperature, gravity, extinction, chemical composition, mass, age,.) q For a representative, complete sample of stars (1+ billion objects 0.5% of the stars in the Milky Way) q This can only be achieved from space, by collecting: q Astrometry (3D positions and 2D velocities; Astrometric Field = AF) q Photometry (spectro-photometry; Blue and Red Photometers = BP and RP) q Spectroscopy (150 million brightest stars; Radial Velocity Spectrograph = RVS) q This precisely is Gaia! 8

9 The reach of Gaia Our Sun Figures courtesy NASA/JPL-Caltech/R. Hurt and DPAC/X. Luri

10 The reach of Gaia Figures courtesy NASA/JPL-Caltech/R. Hurt and DPAC/X. Luri

11 One billion stars in 3D will provide... in our Galaxy the spatial and velocity distributions of all stellar populations the formation history and past evolution of bulge, disk, and halo a rigorous framework for stellar structure and evolution theories a large-scale survey of double and multiple stars (~100,000,000) a large-scale survey of extra-solar planets (~7,000) a large-scale survey of solar-system bodies (~350,000) and beyond... supernovae and burst sources (~6,000) local-group galaxies, including the Magellanic Clouds (~20) resolved galaxies (~1,000,000) plus quasars and redshifts (~500,000) relativistic light bending, microlensing, gravitational waves (upper limits),... Posters Timo and Uwe 11

12 Gaia in one viewgraph X q Who: European, ESA-only mission q When: launch 19 December 2013 for a nominal 5-year mission (+ extension) q Where: L2 (1.5 million km from Earth) q What: positions, parallaxes, proper motions for 1+ billion stars (2016, 2018, 2020, 2022) X Figure courtesy ESA Figure courtesy Jane Douglas (ESA) q Data processing: 430 scientists (DPAC) q Software: 3 million lines of code (Java) q Data collected so far: 47 terabyte with 90 billion star transits (and counting...) q First data release: 14 September 2016 with 2 X million positions, parallaxes, proper motions

13 Routine operations q In five-year routine phase since 25 July 2014 q Data collected so far (cosmos.esa.int/web/gaia/mission-numbers): q 891 billion astrometric measurements (AF) q 180 billion low-resolution photometric measurements (BP/RP) q 17 billion high-resolution spectra (RVS) q Magnitude limits: q Astrometry and photometry down to G = 20.7 mag q Spectra down to G RVS = 16.2 mag q Special data: q Sky-Mapper imaging for stars brighter than G = 3 mag q Sky-Mapper imaging of Baade s Window, ω Cen, etc. q Special data not (yet) processed in the standard pipelines Posters Natalia and Johannes

14 Contents q Gaia q Gaia DR1 q Globular clusters q Open clusters(+ dwarf galaxies) q The Hyades q Gaia DR2 q Conclusions Figure courtesy ESA/Gaia/DPAC

15 Data Release 1 (DR1) 14 September 2016 q Based (only) on 14 months of input data q Astrometry q Position for ~1.1 billion sources (epoch J2015.0) q Parallax and proper motion for ~2 million Hipparcos and Tycho-2 stars (V < 11 mag; Tycho-Gaia Astrometric Solution TGAS) q Covariance matrix (standard errors and correlations) q Reference frame aligned to ICRS using ~2000 QSOs q Photometry q Mean G-band flux and error for all sources q Photometric zero-point (VEGAMAG and AB) q Transformations to other photometric systems (e.g., Sloan, Johnson-Cousins) q Light curve and classification for ~3000 selected RR-Lyraes and Cepheids q Data, documentation, and visualisation q archives.esac.esa.int/gaia (plus ESASky!)

16 Data Release 1 (DR1) 14 September 2016 x 1 billion x 3000 x 2 million d Brightness Figure (idea) courtesy Anthony Brown Time

17 Contents q Gaia q Gaia DR1 q Globular clusters q Open clusters(+ dwarf galaxies) q The Hyades q Gaia DR2 q Conclusions Figure courtesy ESA/Gaia/DPAC

18 Gaia s first sky map Figure courtesy ESA/Gaia/DPAC

19 M4 in ESASky with DR1 positions

20 Globular clusters and Gaia Watkins & Van der Marel (2017) Wait for (at least) DR2... Total number of stars in globular clusters Milky Way GC catalogue (Harris updates) Many 157 Search DR1-TGAS within 2 tidal radii Check magnitude (tip RGB and fainter) Retain if proper motion and parallax agree with HST Add radial velocity from literature Retain if on evolutionary CMD sequence Check with field-star model 20 5 Pancino et al. (2017): The astrometry will be only marginally affected by crowding, even for the most field-contaminated bulge GCs Figure courtesy ESA/Gaia/DPAC

21 q Massari et al. (2017) combined HST and Gaia DR1 positions in NGC2419 (d ~ 87.5 kpc) q Relative proper motions over year for 366 members q Made absolute using a (I mean one ) background galaxy q Derive orbit in Milky Way halo (pericentre ~ 53 kpc, apocentre ~ 98 kpc) q Possibly associated to Sgr dwarf spheroidal Really wait for DR2?

22 Contents q Gaia q Gaia DR1 q Globular clusters q Open clusters(+ dwarf galaxies) q The Hyades q Gaia DR2 q Conclusions Figure courtesy ESA/Gaia/DPAC

23 Open clusters q How / when / where / why do clusters form? q Internal structure, mass segregation, flattening, mass & luminosity function,... q How / when / where / why do clusters evaporate and populate the field? q How do galactic disks evolve? q Trace stars / streams back to original cluster / association (+ runaway stars) q Milky Way disk tracers (migration, resonances, heating, chemical evolution) q Test stellar structure and evolution models across the mass spectrum q Variability (Cepheids, RR Lyraes,...) and multiplicity (incl. planets) q... Talks Antonella, Anthony, and Danny Figure courtesy Roth Ritter

24 Open clusters before Gaia q Karchenko et al. (2013) q Some 3006 clusters* known q Knowledge heavily biased q Most are nearby q Only complete to ~1.5 kpc(?) q Size of nucleus depends on distance (detection bias) q Some 100,000 could exist... *Actually includes asterisms, remnants, associations,... Figure courtesy NASA/JPL-Caltech/R. Hurt

25 Open clusters and Gaia q End-of-mission astrometric accuracy rule of thumb at 15 th magnitude q 1% accuracy at 1 kpc q 5% accuracy at 5 kpc Type Number known < 1 kpc < 5 kpc Globular clusters Open clusters ~2630 q Detection of clusters (all sky, faint, complete, accurate, precise, unbiased) q Determination of members (astrometry + photometry + spectroscopy) q Characterisation of clusters (distances, motions, orbits, ages, metallicities) q Characterisation of cluster members (binaries, variables, abundances) Figure courtesy ESA/Gaia/DPAC

26 Gaia Collaboration et al. (2017) q Validation of TGAS using 19 clusters within ~500 pc q Some ~ members q Find members out to ~15 pc (which is selected field size) q Distances in line with literature, with one exception (see later) q Narrow main sequences, for instance Hyades (see later) q TGAS = tip of the iceberg...

27 Gaia Collaboration et al. (2017) q Validation of TGAS using 19 clusters within ~500 pc q Some ~ members q Find members out to ~15 pc (which is selected field size) q Distances in line with literature, with one exception (see later) q Narrow main sequences, for instance Hyades (see later) NGC 2516: Jeffries et al. (2001) q TGAS = tip of the iceberg...

28 Gaia reveals cluster existence q Koposov et al. (2017) systematically searched the DR1 position catalogue for position overdensities q Known dwarf galaxies show up q Note: Antoja et al. (2015) predict new ultra-faint dwarf galaxy detections! q These examples demonstrate the incredible purity and quality of the Gaia Catalogue, and highlight Gaia s superb satellite discovery capabilities even without colour information

29 Gaia reveals cluster existence q Koposov et al. (2017) discovered a new cluster ~11 from Sirius ( Gaia 1 ) q A 10σ detection, actually also seen in WISE star counts

30 Gaia reveals cluster existence q Koposov et al. (2017) discovered a new cluster ~11 from Sirius ( Gaia 1 ) q A 10σ detection, actually also seen in WISE star counts q Spectroscopic confirmation by Simpson et al. (2017)

31 Gaia reveals cluster existence q Koposov et al. (2017) discovered a new cluster ~11 from Sirius ( Gaia 1 ) q A 10σ detection, actually also seen in WISE star counts q Spectroscopic confirmation by Simpson et al. (2017) q Old (3 Gyr), thick-disk cluster (z max ~ 1.1 kpc) at ~4.5 kpc q Did it survive ~30 galacticplane passages?! q Links to extra-galactic origin discussion...

32 Open clusters beyond the Milky Way q JdB & De Marchi (2011) simulated Gaia s view of R136 in the LMC q Even a density of ~1.5 million stars deg -2 is no problem for on-board detection q Obviously, crowding causes window truncation and blending q Crowded regions therefore suboptimally covered in DR2 Figure courtesy NASA/ESA

33 Contents q Gaia q Gaia DR1 q Globular clusters q Open clusters(+ dwarf galaxies) q The Hyades q Gaia DR2 q Conclusions Figure courtesy ESA/Gaia/DPAC

34 The Hyades q Nearby (~45 pc), intermediate age (~700 Myr), not reddened, huge area on sky (60 60 ), large (peculiar) proper motion (110 mas yr -1 ), large (peculiar) radial velocity (40 km s -1 ) q Reino et al. (in prep.) use TGAS data (+ Hipparcos stars as needed to complement bright end) q Start with 2296 stars in field q Add 908 literature radial velocities (v r ) q Determine membership only based on kinematics q Find 251 candidate members (200 with v r ) q Past members demoted: 15 q New members with v r : 18 Figure courtesy Airbus DS

35 TGAS entries in 10-pc-radius 45 pc

36 TGAS entries in 10-pc-radius 45 pc

37 Principal axes of the moment-of-inertia matrix q TGAS data confirm Hipparcos findings q Cluster roughly spherical in core (r c ~ 3 pc) but flattened at larger radii (r t ~ 10 pc) q Cluster flattened along galactic plane q Naturally expected from tidal evolution over ~700 Myr Major axis Intermediate axis Minor axis

38 Stars colour coded with distance to centre Distance to cluster centre [pc] q Clear, dense core with significant spread of members out to large radii

39 Stars colour coded with member likelihood Highest-probability member lower-probability member q Clear, dense core with significant spread of members out to large radii q Some corona / halo stars are high-fidelity members

40 Projections of the three principal axes added Highest-probability member lower-probability member q Clear, dense core with significant spread of members out to large radii q Some corona / halo stars are high-fidelity members q Cluster is resolved: spread reflects internal structure + projection q Soft edge / gradual transition into field

41 Colour vs absolute-magnitude diagram q Smooth main sequence over ~10 magnitudes q Messy turn-off (rotation, binarity, Am stars, magnetic mixing,...) q Four (known) giants q Binary sequence visible q Photometric errors in B-V dominate over absolute-magnitude errors(!) Main and binary sequence from Smith (2012) Highest-probability member lower-probability member

42 Colour vs absolute-magnitude diagram q Kinematic modelling: assume stars share 3D cluster space motion but allow for dispersion σ v q Use maximum likelihood method to fit 3D space motion, σ v, and individual parallaxes, given the proper motions + errors q Iterate: reject outliers (binaries, escapers,...) q Improved parallaxes for 187 stars and σ v ~ 0.25 km s -1 Padova isochrone (675 Myr) Highest-probability member lower-probability member

43 Colour vs absolute-magnitude diagram q Substructure in main sequence around B-V ~ 0.4 q Effects of convection in atmospheres and envelope (Böhm-Vitense gap) q D Antona et al. (2002) show that isochrones are sensitive to convection treatment: mixing-length theory (MLT) versus full-spectrum turbulence (FST) q Work in progress...

44 Colour vs absolute-magnitude diagram q Substructure in main sequence around B-V ~ 0.4 q Effects of convection in atmospheres and envelope (Böhm-Vitense gap) q D Antona et al. (2002) show that isochrones are sensitive to convection treatment: mixing-length theory (MLT) versus full-spectrum turbulence (FST) q Work in progress... FST MLT

45 Moving the Hyades Myr into the future Movie courtesy JdB

46 The Pleiades cluster Images courtesy Anthony Ayiomamitis and Gaia Collaboration

47 The Pleiades cluster Images courtesy Anthony Ayiomamitis and Gaia Collaboration

48 The Pleiades cluster Images courtesy Anthony Ayiomamitis and Gaia Collaboration

49 Contents q Gaia q Gaia DR1 q Globular clusters q Open clusters(+ dwarf galaxies) q The Hyades q Gaia DR2 q Conclusions Figure courtesy ESA/Gaia/DPAC

50 Data Release 2 (Gaia DR2) April 2018 q Based on 21 months of data q Position, parallax, and proper motion for ~1 billion sources (epoch J2015.5) with full covariance matrix (standard errors & correlations) q Typical parallax standard errors: 30 µas (<15 mag), 150 µas (18 mag), 700 Gaia DR2 will not be perfect but it will be µas (20 mag); systematic errors < 100 µas q Reference frame aligned to amazing ICRS using ~3000 QSOs (ICRF-3 prototype) q Mean G, BP, and RP integrated fluxes and errors for (nearly) all sources q Light curves and classifications for ~0.4 million selected variable stars q Median radial velocities for ~5 million sources with G RVS < 12 mag q Effective temperatures and Lennart extinctions for Lindegren ~100 million sources with G < 17 mag q Radius and luminosity for ~1 million DR1 TGAS sources q Epoch astrometry for a pre-selected list of ~10,000 asteroids q Data, documentation, and visualisation q archives.esac.esa.int/gaia

51 Contents q Gaia q Gaia DR1 q Globular clusters q Open clusters(+ dwarf galaxies) q The Hyades q Gaia DR2 q Conclusions Figure courtesy ESA/Gaia/DPAC

52 Conclusion q Gaia = U3 q Unique mission aimed at q Unfolding the structure and evolution of the Milky Way through q Ultra-precise, multi-epoch observations of 1+ billion stars q Two+ million stars teaser release September 2016 q One+ billion stars bomb release April 2018 q Since I started talking, Gaia collected q 7,577,189 astrometric observations q 996,170 photometric observations q 155,411 spectroscopic observations Figure courtesy Airbus DS