20180508.pdf

An introduction of some of the GAIA DR2 science.

Transcript

1. Yuhan Yao Mission Intro 20180508@THCA The Gaia
2. Yuhan Yao Mission Intro 20180508@THCA The Gaia
3. Yuhan Yao Mission Intro 20180508@THCA The Gaia
5. An all sky survey of 1.7 billion point like sources (V<20): — Position & brightness: 1.7 billion — Color: 1.4 billion; distance & proper motion: 1.3 billion — Surface temperature: 161 million — Radius & luminosity: 77 million — Radial velocity: 7 million Scanning: each object 10-250 times (ave=80) Hipparcos: 0.7-0.9 mas (1mas = 0.001’’)
6. Astrometry the Ancient Technique Proper Motion: angular motion across the sky of nearby stars with respect to distant stars. At same Vt, the further, the smaller μ. Cumulative.
7. Proper Motion: angular motion across the sky of nearby stars with respect to distant stars. At same Vt, the further, the smaller μ. Cumulative. Parallax: the displacement in the apparent position viewed along two different lines of sight. Only along the direction of earth’s motion. Go back and forth. Astrometry the Ancient Technique
8. Proper Motion: angular motion across the sky of nearby stars with respect to distant stars. At same Vt, the further, the smaller μ. Cumulative. Parallax: the displacement in the apparent position viewed along two different lines of sight. Only along the direction of earth’s motion. Go back and forth. Astrometry the Ancient Technique 0GGF$C[GUKCP/GVJQFŎ
9. Science Instruments Two telescopes One focal plane )NQDCN#UVTQOGVTKE+PVGTHGTQOGVGTQH#UVTQRJ[UKEU
10. The Focal Plane wave front sensor basic angle monitor The sky Mappers Astrometric Field 2
11. The Focal Plane BP (blue photometer): 330-680nm RP (red photometer): 640-1050nm two low resolution spectra — color R = 20-100
12. The Focal Plane doppler shift of absorption lines in a high-resolution spectrum 845-872nm CaT R = 11500 Vr, classification, Teff, logg, [Fe/H], E…
13. • Stellar Physics: CMD ( WD Population + Variable Stars) • Kinematics of the Milky Way & the Solar Neighborhood Science
14. Composite HRD of 32 Open Cluster Young Old
15. Globular Cluster
16. Solar neighborhood HRD Gaia Hipparcos (<200pc)
17. Hipparcos Gaia blue: median fiducial green: the same fiducial -0.753 mag, corresponding to an unresolved binary system of two identical stars. Gaia age binary Solar neighborhood HRD
18. Gaia Gaia age binary RC Solar neighborhood HRD Hipparcos Red Clump Stars White Dwarfs blue: median fiducial green: the same fiducial -0.753 mag, corresponding to an unresolved binary system of two identical stars.
19. Local WD Population DA: hydrogen atmosphere WDs DB: helium atmosphere WDs
20. Local WD Population
21. Local WD Population 36% DB not due to different atmospheric composition Fit Gaia CMD with DA/DB mass distribution
22. Local WD Population DA DA DB low mass WDs require binary evolution second peak contributes ~25% WDs (0.65-0.9 Msun) predicted frequency of single WDs that form through mergers.
23. Variable Stars
24. Pulsating Stars on the CMD
25. Motions on the CMD Pulsating Stars: brightness variations dominated by changes in temperature (not radius)
26. Pulsating Stars: brightness variations dominated by changes in temperature (not radius) Eclipsing Variables: EW type — similar mass (color) — nearly vertical path Motions on the CMD
27. Pulsating Stars: brightness variations dominated by changes in temperature (not radius) Eclipsing Variables: EW type — similar mass (color) — nearly vertical path Rotationally induced Variables: cold star-spots, absorb light in blue, re-emit in red. Broad band G, horizontal. Motions on the CMD
28. Pulsating Stars: brightness variations dominated by changes in temperature (not radius) Eclipsing Variables: EW type — similar mass (color) — nearly vertical path Rotationally induced Variables: cold star-spots, absorb light in blue, re-emit in red. Broad band G, horizontal. Eruptive Stars: additional extinction during eruptive phases — redder when brighter. Motions on the CMD
29. The story just begins…
31. azimuth -30~30 deg inertial frame: clockwise
32. Radial Velocity Gradient in the MW Disk Median Galactic Vr of the giant sample as a function of galactic radius for 2 azimuth slices. The curves correspond to different Z layers. A pattern of oscillation. Confirmed galactocentric radial velocity gradients in the inner / outer disk.
33. Median velocities in the disk plane Complexity and richness of the galactic velocity fields. Streaming motions could be produced by: (i) internal mechanisms (response of the stars to the bar or spiral structure) (ii) external perturber: e.g. satellite accretion, impact of low-mass dark matter halos. of the giant sample. semi-circular geometry, with a small pitch angle. red circular arcs, large-scale variation gradient outwards
34. azimuth -30~30 deg inertial frame: clockwise co-rotation frame: anti-clock
35. Velocity distribution of the Solar Neighborhood away from galactic center towards galactic center slower than the sun faster than the sun Most stars at Sun’s location: V=-20 U=0 W=0
36. Velocity distribution of the Solar Neighborhood Velocity plane of stars in the solar neighborhood, 2D histogram of the velocity with a sbin of 1km/s. away from galactic center towards galactic center slower than the sun faster than the sun Arch-like structure; Hercules stream — 2 branches? Hyades, Pleiades…
37. Velocity plane of stars in several distant regions in a ring between 0.5 and 1 kpc from the Sun. Velocity distribution in the Solar Outskirts Galactic Center Arch-like structure; great change in galactic radius (than in azimuth); Hercules gap variations (right to left: 200 - 240 km/s); 2nd gap…
38. Future of Astrometry •Relative Astrometry (Pointed Mission) in the Sub-μas Regime •Global astrometry in sub-μas or even nano-arcsec regime •Global astrometry in the near-infrared (NIR) •Global astrometry in the optical in a new Gaia-like mission 6JCPMUHQTNKUVGPKPI