Keith Hawkins Columbia Univ. (Simons Fellow) 25 April 2017

Transcription

1 Red Clump Stars, Stellar Twins, and the Prospects of Chemical Cartography with Gaia Keith Hawkins Columbia Univ. (Simons Fellow) 25 April 217 Ignace Gaston Pardies, Star Map Plate 2: Cetus, Aquarius, Andromeda. etc, Paris, 1693

2 A Vision of Chemical Cartography [Mg/Fe] as a function of spatial position in Gaia-ESO Adapted from Greg Stinson and Maria Bergemann. Ingredients : chemical abundances, Distances, sky positions, ages?

3 What can cartography tell us chemical history across the galaxy chemical substructure Radial migration Hayden+215 Note: This (and many Galactic structure) work(s) made use of Red Clump Stars

4 Ingredient 1: chemical abundances credit: commons.wikimedia.org

5 The Era of Large Surveys N ~ 1, 25+ elements 212 N ~ 1,, N ~ 1,, 15+ elements 18+? elements ? N ~ 1, 15 (2*+) elements 28 N ~ 483, 8+ elements

6 Chemical Labeling Galactic components cluster in chemical space! (cartography is the next step > need distances) R. Wyse Talk, Hawkins+ 215b; see also Hogg+216, Blanco-Carisma +216, Lambert+217, Ness+217; and many others

7 Ingredient 2: Distances Red clump stars (Stanek+1998, ) stellar twins (Jofre+216, )

8 Distances: Red Clump Red clump Use Gaia parallaxes to assess: (1) How good of a standard candle is the RC? (2) Update magnitude of RC in J, H, Ks, W1, W2, W3, W4, G, NUV*

9 Red Clump Datasets G-K Parallax cut at 3% (prior v.s. data dominated posterior) N ~ 97 (3%) N ~ 18 (1%) MK -62 (Laney+212) APOKASC (Elsworth+216), APOGEE-RC (Bovy +214), Laney+212, APO1m (Feuillet+216)

10 Distances: Red Clump The Model N Mλ

11 Distances: Red Clump The Model RC N Mλ

12 Distances: Red Clump The Model RC N Contaminates Mλ

13 Distances: Red Clump The Model M, σ M RC M c =M, σ Mc cont. f out fraction of contamination RC N Contaminates Mλ

14 Distances: Red Clump The Model N M, σ M RC M c =M, σ Mc cont. f out fraction of contamination Other important parameter(s): L scale-length of exponentially decreasing RC space density prior (Bailer-Jones+ 215; Astraatmadja+216) Contaminates Mλ

15 Distances: Red Clump The Model N M, σ M RC M c =M, σ Mc cont. f out fraction of contamination Other important parameter(s): L scale-length of exponentially decreasing RC space density prior (Bailer-Jones+ 215; Astraatmadja+216) Nuisance parameters : - distance - Extinction Contaminates Mλ

16 Distances: Red Clump The Model N M, σ M RC M c =M, σ Mc cont. f out fraction of contamination Other important parameter(s): L scale-length of exponentially decreasing RC space density prior (Bailer-Jones+ 215; Astraatmadja+216) Nuisance parameters : - distance - Extinction Contaminates Use STAN statistical software to sample posterior in parameters Mλ

17 Red Clump K(JHG+)-Magnitude Mk = -62 +/- 13 ; σmk = 17+/- 2; fout ~ 17% M = abs mag M= σm = dispersion of abs mag = σm,out = dispersion of abs mag of L = scale-length outlier of exponential = M,out L (pc) = fout = contamination fraction fout = M L (pc) M,out M fout L (pc) 8 M,out 2 decreasing space density prior 21 M M fout Hawkins+ 217 in prep

18 Red Clump K(JHG+)-Magnitude Mk = -62 +/- 13 ; σmk = 17+/- 2; fout ~ 17% M = abs mag M= σm = dispersion of abs mag (1) (2) σm,out = dispersion of abs mag of L = scale-length outlier of exponential = M,out L (pc) = out M L (pc) M,out M 65 fout = M,out L (pc) fout = Consistent with literature in K s decreasing space density dispersion sets floor of ~1% prior distance uncertainty f = contamination (fair standard candle) fraction M M fout Hawkins+ 217 in prep

19 Red Clump K(JHG+)-Magnitude Agreement with literature: Good New Fair Poor Hawkins+ 217, in prep

20 M M M,out L (pc) fout M,out M,out L (pc) 75 M 9 5 M fout RC in Galex NUV New M = σm = 83 +/- 7!! = = L (pc) = fout =

21 RC in Galex NUV New Mohammed+ (with KH), 217 in prep

22 RC in Galex NUV New Takeaway: RC is a good standard candle; but the bluer the band the more population effects (e.g. [Fe/H]) should be accounted for 2. Photometric Metallicity index using NUV Mohammed+ (with KH), 217 in prep

23 Stellar Twins Interests: Use twins to map the bulge, obtain distances to stars at larger distances than Gaia can reach credit: IoA, Cambridge

24 Distances: Stellar Twins Jofre et al. 216

25 Distances: Stellar Twins Twins used to help settle Pleiades debate Mädler et al. (incl. KH) 216 Figure taken from Gaia collab. et al. 216

26 Stellar Twins in APOGEE Alternative ways to find stellar twins: χ 2 ~6 APOGEE-TGAS stars with quality spectra+aspcap params

27 Stellar Twins in APOGEE Alternative ways to find stellar twins: χ 2 < ( $/$TGAS) > ( $/$TGAS)

28 Stellar Twins in APOGEE Alternative ways to find stellar twins: χ 2

29 Stellar Twins in APOGEE Alternative ways to find stellar twins: χ 2

30 Stellar Twins in APOGEE Alternative ways to find stellar twins: χ 2

31 What are the Prospects for chemical cartography? [Mg/Fe] as a function of spatial position in Gaia-ESO Adapted from Greg Stinson and Maria Bergemann.

32 What are the Prospects for chemical cartography? [Mg/Fe] as a function of spatial position in Gaia-ESO Adapted from Greg Stinson and Maria Bergemann. Great! with RC stars, Gaia, stellar twins and a ton of large surveys for chemistry.