Gaia Toma Zwitter Gaia 1 1 billion objects

Gaia Tomaž Zwitter Gaia: > 1. 1 billion objects (V ≤ 20. 9), positions accurate to between 5 and 400 μas, spatial resolution ~ 100 mas, blue and red SED at 50 - 200+ epochs over 5 -9 years, RVs for objects brighter than V~15. 5, spectroscopic parameters for the one brighter than V~12. 5.

Gaia - first data release The first data release (September 2016): (Brown et al. 2016) positions, parallaxes (error ~0. 3 mas) and proper motions (error ~1 mas/yr) for 2 million Hipparcos/Tycho-2 stars; positions (error ~10 mas) and G magnitudes (error < 0. 03 mag) for 1. 1 billion objects (V ≤ 20. 9); (V = 1. 02 G − 0. 24 for V-I ~ 0. 7) G-band light curves and characterization for ~3000 Cepheids and RR Lyrae stars around the south ecliptic pole. QSOs: (Lindegren et al. 2016, Mignard et al. 2016) 135, 000 observed (from the list of Andrei et al. 2014); positions compared to VLBI reference frame; formal standard error for 2191 quasars (with 17. 6 < V < 20. 7) compared to ICRF 2: 0. 76 mas for 50% and 3. 35 mas for 90% sources; alignement with the ICRF 2 to better than 0. 1 mas at epoch 2015. 0, nonrotation to within 0. 03 mas/yr; there are now 11, 444 objects with VLBI positions, i. e. 3. 5 -times more than in ICRF 2 (Petrov & Kovalev 2016).

Sky chart of 1, 142, 679, 969 sources Brown et al. 2016

3 problems: damped throughput (ice), basic angle variation, stray-light. They are now solved or under control.

Prusti et al. 2016 Focal plane: 3 main instruments

Positional accuracy errors after 5 yr mission Jester et al. 2005 Proft et al. 2016 Brown et al. 2016

Gaia: photometric accuracy 3 bands: white (G: 330 -1050 nm), blue (BP: 330 -680 nm), red (RP: 640 -1050 nm), ~ 72 transits in 5 yrs (min 50, max 200+). errors for a single transit

Gaia QSOs: λ coverage by BP and RP spectra Proft et al. 2016, number of photons per 5 transits

Redshifts of QSOs with V ~ 20. 2 after 5 yrs of mission Proft et al. 2016

Gaia QSOs: variability detection by sums of five transits z = 2. 03 r' = 17. 5 (Proft et al. 2016)

Offsets in Gaia vs. VLBI positions Kovalev et al. (2017) determined VLBI-jet direction for 2957 AGNs observed by Gaia. Position offsets along the jet require strong, extended parsecscale optical jets. Small (<1 mas) offsets in direction opposite to the jet can be due to extended VLBI jet structure or a “core-shift” effect due to synchrothon opacity.

Gaia timeline Launch: 19 December 2013, The 1 st data release: 14 September 2016: TGAS parallaxes & proper motions for Tycho stars, VLBI coordinate system match. The 2 nd data release: April 2018: Five-parameter astrometric solutions for all sources with acceptable formal standard errors (>109 anticipated), and positions (α, δ) for sources for which parallaxes and proper motions cannot be derived. G and integrated GBP and GRP photometric fluxes and magnitudes for all sources. Median radial velocities for sources brighter than GRVS= 12 mag (V=12. 8 for G 0 V star, V=13. 2 for K 1 III star). For stars brighter than G = 17 mag estimates of the effective temperature and, where possible, line-of-sight extinction will be provided, based on the above photometric data. Photometric data for a sample of variable stars. Epoch astrometry for a pre-selected list of >10, 000 asteroids. Mission duration: 2019, 2021, 2023? Final release with everything: 3 yrs later.

Gaia timeline In perspective (7 months from now): Parallax & proper motion accuracy of 70 μas implies 10% error at 1. 3 kpc and 3% error at 400 pc. BP/RP: only integrated magnitudes, perhaps to be so at least to 2020 or 2022+. Parameters: Teff+reddening from BP/RP, logg from G & parallax. RVS: for V < 12, maybe V < 13, only average reported and for non-variable RVs, accuracy ~1 -2 km/s. So ground based surveys valuable for: RVs, spectroscopic params, abundances. Why we need accurate RVs? Long period SB 1 s, vertically resolved atmospheres, cluster micro-dynamics, LSR.

On-going ground-based optical stellar spectroscopic surveys Goals: individual element abundances, radial velocities. Surveys: RAVE (www. rave-survey. org), LAMOST (www. lamost. org), Gaia-ESO (www. gaia-eso. eu), Galah (www. galah-survey. org), Apogee, Funnel. Web.

The 3 ground-based surveys

. . . it was:

. . . it is: (a bug in astro-py discovered)

shift applied: RVRAVE = RVGalah – 0. 17 ± 0. 03 km/s.

shift applied: RVHR 21 = RVHR 15 N + 0. 70 ± 0. 05 km/s.

RV shifts between surveys RAVE = Galah – 0. 17 ± 0. 03 km/s HR 15 N = HR 10 = Galah + 0. 16 ± 0. 06 km/s UVESU = Galah + 0. 69 ± 0. 05 km/s UVESL = HR 21 = Galah + 0. 86 ± 0. 03 km/s Note how small are the errors. Next: stellar parameters

Fe abundance of Galah and RAVE

+ median, within □ 68% of objects.