Galactic archaeology with the RAdial Velocity Experiment

Transcription

1 Galactic archaeology with the RAdial Velocity Experiment Georges Kordopatis & RAVE collaboration Leibniz-Institute for Astrophysics, Potsdam Multi-Object Spectroscopy in the next decade: Big questions, large surveys and wide fields

2 RAVE: 4th public data release Intermediate resolution (R~7500) stars, spectra (DR3: stars) 9 <I< 12 mag Kordopa's+ 2013b Database: ü Radial velocities ü Spectral morphological flags ü T eff, logg, [M/H] ü Line-of-sight Distances ü Mg, Al, Si, Ti, Ni, Fe ü Photometry: DENIS, USNOB, 2MASS, APASS ü Proper motions: UCAC4, PPMX, PPMXL, Tycho-2, SPM4 Georges Kordopa,s Santa Cruz, March 2nd,

3 RAVE: 4th public data release Intermediate resolution (R~7500) stars, spectra (DR3: stars) 9 <I< 12 mag Kordopa's+ 2013b Database: Radial velocities Spectral morphological flags > 50 km/s Teff, logg, [M/H] km/s km/s Line-of-sight Distances km/s < -50 km/s Mg, Al, Si, Ti, Ni, Fe Photometry: DENIS, USNOB, 2MASS, APASS ü Proper motions: UCAC4, PPMX, PPMXL, Tycho-2, SPM4 ü ü ü ü ü ü Georges Kordopa,s Santa Cruz, March 2nd,

4 RAVE s Galactic 3D velocity errors Cumula,ve DR4 DR2 Combination of: Distance errors (<30%) +Errors in RV (95% of the stars ΔV rad < 4 km s -1 ) +Errors in proper motions (~3 mas yr -1 ) Error in velocity (km/s) 80 % of the stars with ΔV < 20 km s -1 Georges Kordopa,s Santa Cruz, March 2nd,

5 Science? DR4 has led to >20 publications: - Structure and kinematics of the Milky Way - Accretion events - Moving groups - Evolution of the discs - Mapping of the Diffuse Interstellar bands - Georges Kordopa,s Santa Cruz, March 2nd,

6 Interstellar matter Input spectrum Kos+ 2013,2014 Mapping of the Diffuse Interstellar Band EW of the DIB (Å) Closest neighbours Average spectrum Difference DIB Georges Kordopa,s Santa Cruz, March 2nd,

7 Galactic escape speed Piffl Sample selection: 90 Counter-rotating halo stars with v >200 km s -1 or v >300 km s -1 Density of stars: ƒ(escape speed): n(v) ~ (v esc v) k (Leonard & Tremaine, 1990) V esc = 533 km s -1 => M= 1.3x M (Φ(R)=-0.5* V esc2 ) V esc Georges Kordopa,s Santa Cruz, March 2nd,

8 Hyper-velocity stars Hawkins RAVE Sample Hyper- velocity stars MW: Venn+2004 Fornax: Letarte+2010 Discovery of a dynamically ejected thick disc star Georges Kordopa,s Santa Cruz, March 2nd,

9 Velocity maps Galactocentric radial velocity Kordopa's+ 2013c + Galactocentric azimuthal velocity Galactocentric vertical velocity + + Georges Kordopa,s Santa Cruz, March 2nd,

10 Velocity maps Galactocentric radial velocity Kordopa's+ 2013c + Galactocentric azimuthal velocity Mild radial gradient in V R (Siebert+ 2011) Galactocentric vertical velocity + + Compression-rarefaction pattern (Williams+ 2013) Georges Kordopa,s Santa Cruz, March 2nd,

11 Stellar dynamics Binney Cool dwarfs Hot dwarfs Giants Cool dwarfs and giants agree, except near the plane where σ-dwarfs is lower σ for hot dwarfs significantly lower (younger stars) Milky Way potential at R~8 dominated by the disc potential Georges Kordopa,s Santa Cruz, March 2nd,

12 Radial Chemical gradients in the disc: [M/H] & [X/Fe] Boeche+ 2013,2014 Constraints on Disc formation & Radial migration of stars Georges Kordopa,s Santa Cruz, March 2nd,

13 Metal-weak thick disc Metallicity (dex) Kordopa's+ 2013c + [M/H] V φ (km/s) Disc component at V φ ~ 100 km/s & [M/H] <-1.5 dex MWTD reaches [M/H]<-2 dex and represents ~5% of the canonical Thick disc Correlation between V φ and [M/H] confirmed Extra-galactic origin? Georges Kordopa,s Santa Cruz, March 2nd,

14 Signatures for a violent origin? Minchev [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex Georges Kordopa,s Santa Cruz, March 2nd,

15 Signatures for a violent origin? Minchev [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex 1 - Normal disc evolution: Stars migrate and gain random energy (kinematically hotter) Georges Kordopa,s Santa Cruz, March 2nd,

16 Signatures for a violent origin? Minchev [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex 2- Massive merger at [Mg/Fe]~0.3 dex: Stars gain a vertical velocity dispersion and cannot migrate as efficiently as before because they spend less time on the plane Georges Kordopa,s Santa Cruz, March 2nd,

17 Signatures for a violent origin? Minchev [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex 3- Older stars from small guiding radii migrate Stars with smaller guiding radii migrate to the Solar neighbourhood, having cooler kinematics than the locally born stars Georges Kordopa,s Santa Cruz, March 2nd,

18 Galactic bar & Moving groups Antoja Identification of the Hercules stream at different radii Saddle point position ƒ(pattern speed, orientation of the bar). [8, 8.2] kpc V φ [8.2, 8.4] kpc V φ V φ [8.4, 8.6] kpc V R Bar s pattern speed: 51 < Ω b < 56 km s -1 kpc -1 for 10 o < Φ b <45 o Georges Kordopa,s Santa Cruz, March 2nd,

19 Super-Solar metallicity stars Kordopa7s et al., 2015, MNRAS, 447, Stars mainly located close to the plane. + + Ø But also: Fair amount of stars between 0.4 < z < 1 kpc 19

20 Super-Solar metallicity stars 1) R separation Kordopa7s et al., 2015, MNRAS, 447, 3526 Same MDF inside and outside R 0 20

21 Super-Solar metallicity stars 1) R separation Kordopa7s et al., 2015, MNRAS, 447, 3526 Stars richer than locally born OC stars 21

22 Super-Solar metallicity stars 1) R separation Kordopa7s et al., 2015, MNRAS, 447, 3526 Stars richer than locally born OC stars 22

23 Super-Solar metallicity stars 2) Z separation Only giants Same MDF close and far from the plane for the giants 23

24 3 discs: Super-Solar metallicity stars è Eccentricity determination Kordopa7s et al., 2015, MNRAS, 447, spheroids: Solar neighbourhood: (Dehnen & Binney 98, Binney12) 24

25 Super-Solar metallicity stars è Spiral history of the MW ~Observation Kordopa7s et al., 2015, MNRAS, 447, 3526 Given ISM s metallicity gradient: [M/H]/ R ~ dex kpc-1 (Smartt & Rolleston97; Balser+11 ) Ø Stars born well inside Ro. Stars with [M/H]=0.2 dex: Rbirth < 6kpc Stars with [M/H]=0.4 dex: Rbirth ~2kpc Theory Radial migra,on: (Sellwood&Binney02 ) ① Churning: Co- rota,on resonances with spirals Ø Δe/Δt ~ 0 ② Blurring: Lindblad resonances Ø Δe/Δt 0 Georges Kordopa,s Santa Cruz, March 2nd, 2015 ② ① 25

26 Super-Solar metallicity stars è Spiral history of the MW ~Observation Radially migrated stars seen >0.8kpc Radial migra,on probability is insensi,ve to the extent of a star's excursions perpendicular to the plane Theory Binney & Tremaine08: The gravitational field of a spiral structure with radial wavenumber k varies with exp( k z ) Ø Influence of a wave on stars: < 1/k from the plane Ø The radial wavelength of spiral structure is no smaller than ~1kpc Georges Kordopa,s Santa Cruz, March 2nd,

27 Conclusions / Perspectives 4MOST / WEAVE: larger samples, higher resolutions Gaia release scenario: Spectral parameters available in 2018 Galactic chemo-dynamics with Gaia is possible from 2016! Until then: use of RAVE parameters with Gaia s proper motions/ parallaxes/flags/parameters from BP/ RP DR5: Improved parameters and abundances Georges Kordopa,s Santa Cruz, March 2nd,

28 RAVE vs Gaia Intermediate resolution (R~7 500) stars, spectra (DR3: stars) 9 <I< 12 mag Gaia: R~ Same λ coverage (CaII triplet) ~ targets with spectra Database: ü Radial velocities => ~same accuracy ü Spectral morphological flags => Coming from the CUs ü T eff, logg, [M/H] => same precision (RVS) + BP/RP ü Mg, Al, Si, Ti, Ni, Fe => Similar ü Line-of-sight Distances => Parallaxes! ü Photometry: DENIS, USNOB, 2MASS, APASS => BP/RP ü Proper motions: UCAC4, PPMXL, Tycho-2, SPM4 => high precision! Georges Kordopa,s Santa Cruz, March 2nd,

29 RAVE vs Gaia Intermediate resolution (R~7 500) stars, spectra (DR3: stars) 9 <I< 12 mag Gaia: R~ Same λ coverage (CaII triplet) ~ targets with spectra Database: ü Radial velocities ü Spectral morphological flags ü T eff, logg, [M/H] ü Mg, Al, Si, Ti, Ni, Fe ü Line-of-sight Distances ü Photometry: DENIS, USNOB, 2MASS, APASS ü Proper motions: UCAC4, PPMXL, Tycho-2, SPM4 Georges Kordopa,s Santa Cruz, March 2nd,

30 RAVE s Galactic 3D velocity errors Gaia s Cumula,ve Gaia DR4 DR2 Combination of: Distance errors (<30%) (<10%) +Errors in RV (95% of the stars ΔV rad < 4 km s -1 ) +Errors in proper motions (~3 mas yr -1 ) 50 μas yr -1 Error in velocity (km/s) 80 % of the stars with ΔV < 5 km s -1 Georges Kordopa,s Santa Cruz, March 2nd,

31 Papers DR4 (Kordopa,s et al.) Distances (Binney et al.) Radial migra,on (Kordopa,s et al.) Dynamics (Binney et al.) Gradients (Boeche et al.) Clusters (Conrad et al.) History (Minchev et al.) Metal- weak thick disc (Kordopa,s et al.) MW escape speed & mass (Piffl et al.) DIB (Kos et al.) Chromospherically ac,ve stars (Zerjal et al.) Galac,c bar (Antoja et al.). Georges Kordopa,s Santa Cruz, March 2nd,

32 THANK YOU Georges Kordopa,s Santa Cruz, March 2nd,

33 Metal- weak thick disc Kordopa's et al. 2013c Metallicity (dex) Counts Thick disc + halo Thin disc [M/H] Selection: 1< Z <2 kpc & [M/H] < -1.5 dex Thick disc not expected Georges Kordopa,s Santa Cruz, March 2nd,

34 Georges Kordopa,s Santa Cruz, March 2nd,

35 calibration issues & presence of DR3 biases Georges Kordopa,s Santa Cruz, March 2nd,

36 DR3 calibration issues & presence of biases Georges Kordopa,s Santa Cruz, March 2nd,

37 We want to minimise the effect of the degeneracies degeneracy log g T eff (K) Georges Kordopa,s Santa Cruz, March 2nd,

38 We want to minimise the effect of the degeneracies log g Goal: Reduce the parameter space where the solu,on is searched T eff (K) Georges Kordopa,s Santa Cruz, March 2nd,

39 Reduce the parameter space => 1) Photometric prior 2MASS photometric temperature priors (J- K s ) > 0.75 è T eff < 4500 K 0.4 < (J- K s ) < 0.75 è 3750 < T eff < 6000 K (J- K s ) < 0.4 è T eff > 5250 K Georges Kordopa,s Santa Cruz, March 2nd,

40 Reduce the parameter space => 2) non physical combinations Age=0.3 Gyrs [Fe/H]=- 3 dex log g degeneracy Age=14 Gyrs [Fe/H]=0.3 dex Georges Kordopa,s Santa Cruz, March 2nd,

41 Calibration of the [M/H] Pipeline - reference < [m/h] < < [m/h] < < [m/h] < Pipeline - reference Pipeline - reference Pipeline - reference < [m/h] < < [m/h] < 0.50 Pipeline - reference Calibradon reladon: Georges Kordopa,s Santa Cruz, March 2nd,

42 DR4 Validation of the calibration Georges Kordopa,s Santa Cruz, March 2nd,

43 Stellar distances Bayesian projec,on of the Teff, logg, [M/H] on isochrones Georges Kordopa,s Santa Cruz, March 2nd,

44 Metal- weak thick disc Kordopa's et al. 2013a,c Counts Counts [M/H] V φ (km/s) The halo alone cannot fit the data correctly Georges Kordopa,s Santa Cruz, March 2nd,

45 Signatures for a violent origin? Minchev et al [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex [Fe/H]= dex The stars come progressively from small radii while having similar ages Georges Kordopa,s Santa Cruz, March 2nd,

46 Galac,c escape speed Piffl et al Asympto,c behaviour of the stellar density of the high velocity stars (Leonard & Tremain 1990) Georges Kordopa,s Santa Cruz, March 2nd,