“ECSNe and Super-AGB star workshop", Monash, Feb. 05, 2016 1/16

Galactic Components

M104 (HST) – unbarred spiral with ca. 30% of MW extent

Disk(s) Halo: stars, globular clusters, satellite galaxies, dark matter Central bulge (bars)

2/16

ΛCDM: hierarchical halo formation via accretion of dark matter dominated fragments.

Metal-poor halo stars were

probably donated from satellite

accretion.

Some stars in the dwarf satellites show chemical imprints from

individual SNe ( Pop III).

clues to the earliest enrichment phases.

What about the bulge?

Halo formation

AK et al. 2008; Tolstoy et al. (2009); Simon et al. (2010); AK & Rich (2014) 3/16

Bullock & Johnston (2005)

- 25% of the light in the local universe comes from bulges. - Inhomogeneous class of objects with different formation

channels: 1) Spheroidal (“classical”) bulges form rapidly via early mergers. Bulge forms before disk. 2) Pseudo-bulges / bars evolve from a buckling instability over longer timescales (>1 Gyr).

Bulges

NGC 4710 (HST); McWilliam & Zoccali (2010); Rich (2012) 4/16

•  The bulge is old and metal rich, yet very complex (e.g., McWilliam & Rich 1994; Clarkson et al. 2008; Bensby et al. 2013).

•  Dynamical formation, where bulge == bar (e.g., Shen et al. 2010;

Wegg et al. 2015) ? Prominent X-shape (McWilliam & Zoccali 2010)

•  No evidence for kinematic substructures (streams), although hyper-velocity stars exist. (e.g., Howard et al. 2008; Kunder, AK, et al. 2012; Kunder et al. 2014, 2015;

C.J. Hansen, AK, et al. subm.).

(Galactic) bulge formation

5/16 Wegg et al. (2015)  

•  Oldest stars with [Fe/H] < －3 (z > 6 - 10) are predicted on tight orbits in the innermost halo, due to inside-out nature of CDM: "In the bulge, not of the bulge" (Tumlinson 2010).

•  E.g., ARGOS bulge survey: non-rotating, metal-poor tail; attributed to the inner halo (RGC < 3.5 kpc; Ness et al. 2013)

Bulge vs. halo formation

6/16 [Fe/H]

N

4 3 2 1 00

50

100

150

200

250To date: 55 stars between -2 and -4 dex in surveys of

several 10000s stars

(Ness et al. 2013; García Pérez et al. 2013;

Howes et al. 2014, 2015; Casey & Schlaufman 2015, AK et al. 2016)

[Fe/H]

N

4 3 2 1 00

50

100

150

200

250

•  EMP candidates from narrow-band Ca K photometry (20 Å line, 200 Å continuum, at 3933 Å).

•  Teff-sensitivity from BVI imaging.

•  Calibrated against known EMP stars.

Target selection

Be

ers

& C

hri

stlie

b (

20

05

)

7/16

•  Problems: CR hits, diffraction spikes, TiO in cold M-stars.

Target selection

Be

ers

& C

hri

stlie

b (

20

05

)

•  low-res (R~2000) follow-up of ~150 stars (WFCCD grism)

high-res (R~45000) follow-up of 8 stars (MIKE @Magellan)

Wavelength [A]

Flux

3600 3800 4000 4200 4400 4600 4800100

0

100

200

300

400

500

600

700

8/16 Wavelength [A]

Flux

6135 6136 6137 6138 6139 6140 6141 6142 6143 6144 61450

500

1000

1500

•  One metal-rich (Solar) bulge star •  The majority of (23) species for the rest of the stars is com-

patible with halo abundances!

Abundance results

AK et al. 2016, A&A, in press (arXiv:1511.01490) 9/16

[Ba/Fe]

10123

[La/Fe]

10123

[Nd/Fe]

1

0

1

2

[Fe/H]

[Eu/Fe]

3 2 1 01

0

1

2

[Ba/Fe]

10123

[La/Fe]

10123

[Nd/Fe]

1

0

1

2

[Fe/H]

[Eu/Fe]

3 2 1 01

0

1

2

[Ca/

Fe]

0.4

0

0.4

0.8

[Sc/

Fe]

0.5

0

0.5

[Ti/F

e]

0.5

0

0.5

1

[Fe/H]

[V I/

Fe]

3 2 1 0

0.5

0

0.5

[Cr/Fe]

0.5

0

0.5

[Mn/Fe]

1

0.5

0

0.5

[Fe/H]

[Co/Fe]

0.5

0

0.5

[Ni/Fe]

[Fe/H]3 2 1 0

0.4

0

0.4

Metal-poor Halo (Roederer et al. 2014)

Bulge (Johnson et al. 2012, 2014)

Metal-poor "bulge" (Casey & Schlaufman 2014;

Howes et al. 2014)

r-process enhanced bulge (Johnson et al. 2013)

This work (AK et al. 2016)

•  The majority of (23) species for the rest of the "bulge" stars is compatible with halo abundances and points to standard enrichment processes !

Normal halo-(like) stars ?!

AK et al. 2016, A&A, in press (arXiv:1511.01490)

10/16

Mean abundances of all stars compared to Solar r/s pattern

(Simmerer 2004).

HD 122563, weak r-process

star (Honda 2006)

Z

log

35 40 45 50 55 60 65

2

1.5

1

0.5

0

0.5

1

1.5

Pure sSolar r+sPure r

•  one CEMP-s ( [Fe/H] = -2.5, [C/Fe] = 1.4, [Ba/Fe] = 1.3) •  one Ba-star ( [Fe/H] = -1.5, [C/Fe] = 0.4, [Ba/Fe] = 1.3)

No evidence for binarity (no velocity variations, but no representative time

coverage); abundances indicate origin of C-enhancement from

AGB transfer. First contenders of this class towards the bulge.

& sample spectrum

Some special guests

11/16

Wavelength [A]

Flux

5130 5140 5150 5160 5170 5180 5190 52000

100

200

300

400

500

600

700

800

900

1000

Bonifacio et al. (2015); C.J. Hansen et al. (2016)  

•  Ba-star: High Rb/Zr ratio (0.99), [hs/ls ] = 0.41, low La, Y

•  Low-metallicity (Z=0.0001 – 0.0003) AGB models indicate ~4 M progenitor for Ba-star, ~1.3 Mfor CEMP-s.

•  [Fe/H] of -2.5 coincident with peak of halo-CEMP MDF

Bulge CEMP-s and CH

12/16 F.R.U.I.T.Y. (Cristallo et al. 2011)  

Z

[X/F

e]

30 35 40 45 50 55 60 650

0.5

1

1.51.3 Mo2 Mo3 Mo4 Mo6 Mo

Z

[X/F

e]

30 35 40 45 50 55 60 650

0.5

1

1.51.3 Mo2 Mo3 Mo4 Mo6 Mo

Rb  

Sr  

Y  Zr  

Ba  

La  

Nd  

Eu  

Sm  

Sr  

Y  

Zr  

Ba  La  

Nd  

Zn  

[Fe/H] = -1.5   [Fe/H] = -2.5  

•  Regular (Solar) [Sc/Fe] values are in contrast to predicted depletions in Sc from Pop III nucleosynthesis.

•  Cf. observations of ultrafaint dwarf spheroidals (AK et al. 2008; Simon et al. 2010)

No Population III

13/16

Metal-free, high-explosion model of a 30 M star (Heger & Woosley 2010). Or 10 M with less dilution  

Low-Sc was suggested in bulge (Casey & Schlaufman 2015)

Localized enrichment ? Low-numbers ?

Leo IV dSph  

[Fe/H]

[Sc/Fe]

3.5 3 2.5 2 1.5 1 0.5 0 0.5

0.5

0

0.5

[Fe/H]

[Sc/Fe]

3.5 3 2.5 2 1.5 1 0.5 0 0.5

0.5

0

0.5

•  Location indicates three members on the far side of the X. •  Sample contains stars out to RGC ~ 6 kpc, |z| ~ 3 kpc.

Combined with the regular chemistry this conforms with an overlapping inner halo, in line with Tumlinson (2010).

Bulge or halo? – Location

Li & Shen (2010); McWilliam & Zoccali (2010) 14/16

Model of smooth component

Model of X-shaped bulge component

Metal rich star

•  Often, metal-poor “bulge” stars found to be on tight or eccentric orbits (Howes et al. 2014, 2015; Casey & Schlaufman 2015).

•  Usually based on various sets of proper motions (SPM4, UCAC4, OGLE), which can grossly disagree!

Bulge or halo? – Kinematics

15/16

R.A.

DEC

277.5278278.5279

35

34.8

34.6

34.4

34.2

34

33.8

33.6

33.4

SPM4 R.A.

DEC

277.5278278.5279

35

34.8

34.6

34.4

34.2

34

33.8

33.6

33.4

UCAC4

R.A.

DEC

277.5278278.5279

35

34.8

34.6

34.4

34.2

34

33.8

33.6

33.4

•  Often, metal-poor “bulge” stars found to be on tight or eccentric orbits (Howes et al. 2014, 2015; Casey & Schlaufman 2015).

•  Usually based on various sets of proper motions (SPM4, UCAC4, OGLE), which can grossly disagree!

Bulge or halo? – Kinematics

15/16

X [kpc]

Z [k

pc]

10 5 0 5 1010

5

0

5

10

X [kpc]

Y [k

pc]

10 5 0 5 1010

5

0

5

10

•  We detected “metal-poor” stars towards the “bulge”, down to -2.7 dex.

•  No evidence for Pop III enrichment (normal Sc/Fe), nor extraordinarily massive AGB.

•  First CEMP and Ba-stars in that population.

•  Kinematics are inconclusive due to uncertain proper motions.

Caution with a true, metal-poor bulge – how to distinguish from halo stars passing through ?! Yet consistent with the notion that anicent objects (z>10) are to be found in the central regions of the Milky Way.

•  Improved target selection methods desirable, e.g., using (2MASS+WISE) IR and optical colors (Schlaufman & Casey 2014).

Summary

16/16

Summary

16/16

[Fe/H]

N

4 3 2 1 00

50

100

150

200

250

[Fe/H]

N

4 3 2 1 00

50

100

150

200

250 946 bulge RR Lyrae (Kunder, AK, et al., ApJL, subm.)