red clump stars, stellar twins, and the prospects of chemical … · 2017-05-17 · red clump...
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Red Clump Stars, Stellar Twins, and the Prospects of Chemical Cartography with Gaia
Keith Hawkins Columbia Univ. (Simons Fellow)
25 April 2017 [email protected]
Ignace Gaston Pardies, Star Map Plate 2: Cetus, Aquarius,
Andromeda. etc, Paris, 1693
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A Vision of Chemical Cartography
Ingredients : chemical abundances, Distances, sky positions, ages?
Adapted from Greg Stinson and Maria Bergemann.[Mg/Fe] as a function of spatial position in Gaia-ESO
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What can cartography tell us
• chemical history across the galaxy
• chemical substructure
• Radial migration
Hayden+2015
Note: This (and many Galactic structure) work(s) made use of Red Clump Stars
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The Era of Large Surveys
N ~ 100,000N ~ 1,000,000 N ~ 10,000,00025+ elements15+ elements 18+? elements2012—
2014— 2021-2026?
N ~ 100,000
2008—N ~ 483,0008+ elements
2003-2013
15 (20*+) elements
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Chemical ‘Labeling’ Galactic components ‘cluster’ in chemical space! (cartography is the next step —> need distances)
R. Wyse Talk, Hawkins+ 2015b; see also Hogg+2016, Blanco-Carisma+2016, Lambert+2017, Ness+2017; and many others
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Ingredient 2: Distances
Red clump stars (Stanek+1998, …)
stellar twins (Jofre+2016, …)
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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*
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Red Clump Datasets
• Parallax cut at 30% (prior v.s. data dominated posterior)
• N ~ 970 (30%)
• N ~ 180 (10%)
APOKASC (Elsworth+2016), APOGEE-RC (Bovy+2014), Laney+2012, APO1m (Feuillet+2016)
G-K
MK
-1.62 (Laney+2012)
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Distances: Red Clump The Model
Mλ
N
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Distances: Red Clump The Model
RC
Mλ
N
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Distances: Red Clump The Model
RC
Mλ
N
Contaminates
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Distances: Red Clump The Model
RC
Mλ
N
Contaminates
M, σM — RC Mc=M, σMc — cont.
fout — fraction of contamination
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Distances: Red Clump The Model
RC
Mλ
N
Contaminates
M, σM — RC Mc=M, σMc — cont.
fout — fraction of contaminationOther important parameter(s):
L — scale-length of exponentially decreasing space density prior (Bailer-Jones+ 2015;
Astraatmadja+2016)
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Distances: Red Clump The Model
RC
Mλ
N
Contaminates
M, σM — RC Mc=M, σMc — cont.
fout — fraction of contaminationOther important parameter(s):
L — scale-length of exponentially decreasing space density prior (Bailer-Jones+ 2015;
Astraatmadja+2016)‘Nuisance parameters’:
- distance - Extinction
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Distances: Red Clump The Model
RC
Mλ
N
Contaminates
M, σM — RC Mc=M, σMc — cont.
fout — fraction of contaminationOther important parameter(s):
L — scale-length of exponentially decreasing space density prior (Bailer-Jones+ 2015;
Astraatmadja+2016)‘Nuisance parameters’:
- distance - Extinction
Use STAN statistical software to sample posterior in parameters
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M = �1.62+0.01�0.01
0.12
0.16
0.20
0.24
�M
�M = 0.17+0.02�0.02
0.6
0.8
1.0
1.2
�M
,out
�M,out = 0.71+0.10�0.08
208
216
224
232
240
L(p
c)
L (pc) = 222.67+4.39�4.31
�1.65
0
�1.62
5
�1.60
0
�1.57
5
M
0.08
0.16
0.24
0.32
0.40
f out
0.12
0.16
0.20
0.24
�M
0.6
0.8
1.0
1.2
�M,out20
821
622
423
224
0
L (pc)0.08
0.16
0.24
0.32
0.40
fout
fout = 0.17+0.05�0.05
Red Clump K(JHG+)-MagnitudeM = abs mag
σM = dispersion of
abs mag
L = scale-length of exponential
decreasing space density
prior fout =
contamination fraction
Mk = -1.62 +/- 0.013 ; σMK = 0.17+/- 0.02; fout ~ 17%
σM,out = dispersion of abs mag of
outlier
Hawkins+ 2017 in prep
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M = �1.62+0.01�0.01
0.12
0.16
0.20
0.24
�M
�M = 0.17+0.02�0.02
0.6
0.8
1.0
1.2
�M
,out
�M,out = 0.71+0.10�0.08
208
216
224
232
240
L(p
c)
L (pc) = 222.67+4.39�4.31
�1.65
0
�1.62
5
�1.60
0
�1.57
5
M
0.08
0.16
0.24
0.32
0.40
f out
0.12
0.16
0.20
0.24
�M
0.6
0.8
1.0
1.2
�M,out20
821
622
423
224
0
L (pc)0.08
0.16
0.24
0.32
0.40
fout
fout = 0.17+0.05�0.05
Red Clump K(JHG+)-MagnitudeM = abs mag
σM = dispersion of
abs mag
L = scale-length of exponential
decreasing space density
prior fout =
contamination fraction
Mk = -1.62 +/- 0.013 ; σMK = 0.17+/- 0.02; fout ~ 17%
σM,out = dispersion of abs mag of
outlier(1) Consistent with literature in Ks
(2) dispersion sets floor of ~10% distance uncertainty
(fair standard candle)
Hawkins+ 2017 in prep
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Red Clump K(JHG+)-Magnitude
Hawkins+ 2017, in prep
NewGood Fair
Agreement with literature:
Poor
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RC in Galex NUV M = 8.95+0.05
�0.04
0.60
0.75
0.90
1.05
�M
�M = 0.83+0.06�0.07
1.2
1.8
2.4
3.0
3.6
�M
,out
�M,out = 1.48+0.47�0.32
195
210
225
L(p
c)
L (pc) = 211.39+6.23�6.00
8.80
8.88
8.96
9.04
9.12
M
0.15
0.30
0.45
0.60
f out
0.60
0.75
0.90
1.05
�M
1.2
1.8
2.4
3.0
3.6
�M,out
195
210
225
L (pc)0.15
0.30
0.45
0.60
fout
fout = 0.10+0.19�0.07
σM = 0.83 +/- 0.07!!
New
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RC in Galex NUV
Mohammed+ (with KH), 2017 in prep
New
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RC in Galex NUV
Mohammed+ (with KH), 2017 in prep
Takeaway: 1. 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
New
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Stellar Twins
credit: IoA, Cambridge
Interests: Use twins to map the bulge, obtain distances to stars at larger distances than Gaia can reach
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Distances: Stellar Twins
Jofre et al. 2016
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Distances: Stellar Twins
Mädler et al. (incl. KH) 2016 Figure taken from Gaia collab. et al. 2016Twins used to help ‘settle’ Pleiades debate
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Stellar Twins in APOGEEAlternative ways to find stellar twins: χ2
~600 APOGEE-TGAS stars with quality spectra+ASPCAP params
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Stellar Twins in APOGEEAlternative ways to find stellar twins: χ2
5000 10000 15000 20000 25000 30000 35000 400000.05
0.10
0.15
0.20
0.25
0.30
0.35
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<(�
$/$
TG
AS)>
5000 10000 15000 20000 25000 30000 35000 40000
�2
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Stellar Twins in APOGEEAlternative ways to find stellar twins: χ2
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Stellar Twins in APOGEEAlternative ways to find stellar twins: χ2
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Stellar Twins in APOGEEAlternative ways to find stellar twins: χ2
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What are the Prospects for chemical cartography?
Adapted from Greg Stinson and Maria Bergemann.[Mg/Fe] as a function of spatial position in Gaia-ESO
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What are the Prospects for chemical cartography?
Great! with RC stars, Gaia, stellar twins and a ton of large surveys for chemistry.
Adapted from Greg Stinson and Maria Bergemann.[Mg/Fe] as a function of spatial position in Gaia-ESO