Galactic, stellar (and planetary) archaeology with Gaia: The galactic white dwarf population

Transcription

1 Galactic, stellar (and planetary) archaeology with Gaia: The galactic white dwarf population Boris Gänsicke & Roberto Raddi Richard Ashley Jay Farihi Nicola Gentile Fusillo Mark Hollands Paula Izquierdo Matthew Hoskin Alberto Rebassa Mansergas Tom Marsh Pablo Rodríguez Gil Pier-Emmanuel Tremblay Silvia Toonen

2 95% 5%

3 B2 35Myr A0 250Myr 10Gyr

4 Gaia and the Solar neighbourhood white dwarfs with G stars within 100pc

5 White Dwarf Luminosity Function Cut-off at faintest, coolest, oldest white dwarfs Cut-off in the white dwarf luminosity function due to the limited age of the Galaxy Even the oldest white dwarfs (9-11 Gyrs) are still visible in the solar neighborhood bright hot young faint cool old Measure the age of the Galaxy (e.g. Oswalt et al. 1996, Nature 382, 692)

6 Tentative evidence of enhance star formation over the past ~5Gyr 117 white dwarfs Teff, log g, masses Distances Ages Initial mass function Star formation rate / history Initial-to-final mass relation Tremblay et al. 2014, ApJ 791, 92

7 Many (most?) stars are in binaries Binary fraction Initial mass ratio distribution Initial period (& eccentricity) distribution Interactions (common envelope) using again the 20pc white dwarf sample Toonen et al. 2017, A&A 602, 16

8 Supernova Type Ia progenitors SN Ia progenitors need M 1 +M 2 1.4M So far... Zero known Silvia Toonen

9 3x20min sensitive to massive short period DDs

10 Many planetary systems will survive into the white dwarf phase

11 Photospheric metal pollution by planetary debris Jura & Young 2014, ARE&PS 42, 45 Fe Mg Ca

12 Planetary archaeology = bulk composition Raddi et al. 2015, MNRAS 450, 2083 Hollands et al. 2017, MNRAS 467, 4970

13 Flux calibration with white dwarfs - Only two free parameters (Teff, log g), no metallicity. - Fit is done to the normalised Balmer lines, Stark broadening is sensitive to both temperature and surface gravity. cool hot

14 Flux calibration with white dwarfs - Only two free parameters (Teff, log g), no metallicity. - Fit is done to the normalised Balmer lines, Stark broadening is sensitive to both temperature and surface gravity. - Balmer lines go through max. equivalent width near ~15000K, hot & cold solution, selection (now) based on χ 2 cool hot

15 Flux calibration with white dwarfs - Only two free parameters (Teff, log g), no metallicity. - Fit is done to the normalised Balmer lines, Stark broadening is sensitive to both temperature and surface gravity. - Balmer lines go through max. equivalent width near ~15000K, hot & cold solution, unambiguous selection based on Gaia parallax (April 2018) cool hot

16 Flux calibration with white dwarfs - Best fit & count rate spectrum response function

17 Flux calibration with white dwarfs - Works also at relatively low S/N

18 Flux calibrations from OpR2 & residuals in OpR2.5

19 OpR2.5: Gp=19.2 S/N=17

20 OpR2.5: Gp=19.4 S/N=7

21 OpR2.5: Input vs output (Gaia π, Gp, Rp, Bp not used as constraints!)

22 White dwarf selection April 2018 Gaia Data Release 2 - Prediction from the GUMS-10 simulation (Robin et al. 2012) - G white dwarfs all-sky, probably over-estimated by x2 Absolute magnitude giants main sequence halo/thick disc white dwarfs

23 White dwarf selection April 2018 Gaia Data Release 2 - Prediction from the GUMS-10 simulation (Robin et al. 2012) - G white dwarfs all-sky, probably over-estimated by x2 - Adding 2-year-into-mission uncertainties using PyGaia - pseudo absolute magnitude using π instead of distance giants main sequence white dwarfs 100 deg 2 l=180, b=45

24 White dwarf selection April 2018 Gaia Data Release 2 - Prediction from the GUMS-10 simulation (Robin et al. 2012) - G white dwarfs all-sky, probably over-estimated by x2 - Adding 2-year-into-mission uncertainties using PyGaia - pseudo absolute magnitude using π instead of distance giants main sequence white dwarfs reddening! 100 deg 2 l=100, b=0

25 White dwarf selection April 2018 G + 5log(π) + 5 > 2.8 x (BP-RP) + 8 && (BP-RP) < 2.3 white dwarfs

26 White dwarf selection April G white dwarfs all-sky 6-12 white dwarfs deg -2 / per WEAVE field

27 Why observe ~ with WEAVE? Gaia - First unbiased sample Accurate mass-dependent luminosity function as tracer of galactic SFR Sample thick disc & halo population (~1%) Initial-to-final mass relation in HD Huge resource for stellar, binary & planetary evolution Rare (few %) WDs provide important link to supernovae, planets, gravitational waves sources, strong magnetic fields etc. and if you don t care about any of the above, we ll flux calibrate your spectra

28 White dwarf selection now Gentile-Fusillo et al. 2015, MNRAS 448, 2260: - SDSS colours + SDSS vs USNO proper motions - Probability of being a white dwarf (Pwd) spectroscopically calibrated - Largest, most reliable white dwarf catalogue - g 19, SDSS imaging footprint, white dwarfs, 9000 with spectra DA / non-da white dwarfs, hot stars, QSO