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Galaxy formation Galaxy formation is believed to be initiated by - - PowerPoint PPT Presentation

Feb 05, 2023 232 likes •551 views

Sofia Feltzing: Talk given at Stars for all, Lund 2012 Stars as tools to unravel the history of the Milky Way Sofia Feltzing Department of Astronomy and Theoretical Physics tisdag den 7 februari 2012 Sofia Feltzing: Talk given at Stars for all,

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SLIDE 1

Stars as tools to unravel the history of the Milky Way

Sofia Feltzing Department of Astronomy and Theoretical Physics

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 2

Galaxy formation

  • Galaxy formation is believed to be initiated by

cold dark matter (CDM)

  • Simulations suggest that galaxies grow through a

sequence of infall events

  • Most accreted objects are so small nothing

happens

  • Others create mild perturbations
  • A handful of events involve an object that causes

a major convulsion

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 3

Credit: Marta Volonteri, Milky Way sized galaxy

Final galaxy/halo

Time

Resulting in a merger tree

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 4

In two ways

  • in their ages and elemental abundances
  • in their orbits (we hope)

Stars tell us about the past

  • Provide observational constraints that any

model of galaxy formation must fulfill

  • We work with the Milky Way as this is the

galaxy that can be studied in most detail

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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How stars move in the Milky Way

GC V U W NGP

Galactic centre The sun Stellar disk(s) – circular motion mainly in a plane Halo stars move

  • n eccentric orbits

– fluffy spheroid Galactic bulge – compact spheroid Dark matter halo

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 6

How stars move in the Milky Way

GC V U W NGP

Galactic centre The sun Stellar disk(s) – circular motion mainly in a plane Halo stars move

  • n eccentric orbits

– fluffy spheroid Galactic bulge – compact spheroid Dark matter halo

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 7

How stars move in the Milky Way

GC V U W NGP

Galactic centre The sun Stellar disk(s) – circular motion mainly in a plane Halo stars move

  • n eccentric orbits

– fluffy spheroid Galactic bulge – compact spheroid Dark matter halo

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 8

How stars move in the Milky Way

GC V U W NGP

Galactic centre The sun Stellar disk(s) – circular motion mainly in a plane Halo stars move

  • n eccentric orbits

– fluffy spheroid Galactic bulge – compact spheroid Dark matter halo

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 9

How stars move in the Milky Way

GC V U W NGP

Galactic centre The sun Stellar disk(s) – circular motion mainly in a plane Halo stars move

  • n eccentric orbits

– fluffy spheroid Galactic bulge – compact spheroid Dark matter halo

We can measure the thick disk and halo locally as the stars move past the sun

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 10

Solar neighbourhood

Sirius/UMa Pleiades Hercules Hyades Arcturus LSR–disk Halo [Fe/H] decrease Age increases U km s-1 V km s-1 Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 11

Antoja thesis

Disk dynamics

Bar and spiral arms in the model ➙ makes for more complex velocity-plane

U km s-1 V km s-1 Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 12

Edvardsson et al. (1993) was one of the first papers to combine abundances and kinematics in a systematic

  • way. The paper has been and is hugely influential.

Rmean is proportional to V Key result: abundance trends are tight (<0.05 dex)

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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“No” selection

Fuhrmann 2004 AN 325 3

The elemental abundance trends divide in the solar neighbourhood. Volume complete sample.

Size=Age d<25 pc δ>–15° SNII core collapse τlifetime < 106-107 years SNIa degenerate system τlifetime could be up to a

  • Hubble time

Fe – SNII+SNIa Mg – SNII δTeff Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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Bulge abundance trends

[Ti/Fe] [Cr/Fe] [Ni/Fe] Bulge dwarfs - observed when μ-lensed Thick disk in SN Thin disk in SN E93 Bensby et al. (in prep., 2011, 2010) All old Range of ages Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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Short “thick” disk

Bensby, Alves-Brito, Oey, Yong, Meléndez (2011) ApJ 735 L46

Inner disk: 4<Rsun<7 kpc Solar neighbourhood: Rsun=8 kpc Outer disk: 9<Rsun<13 kpc

δTeff ~ K giants [Ti/Fe] [Si/Fe] [Mg/Fe] Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 16

Short “thick” disk

– 0.5 dex low α

Inner disk: 4<Rsun<7 kpc Outer disk: 9<Rsun<13 kpc Solar neighbourhood: Rsun=8 kpc

δTeff ~ K giants Bensby, Alves-Brito, Oey, Yong, Meléndez (2011) ApJ 735 L46 [Ti/Fe] [Si/Fe] [Mg/Fe] Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SEGUE probes the MW further away

  • 1.0
  • 0.5

0.0 [Fe/H] 0.0 0.1 0.2 0.3 0.4 0.5 0.6 [α/Fe]

log10 N 1.0 1.5 2.0 2.5

1.20 1 . 2 1 . 2 1 . 8 1.80 2.00 2.00 2.10

Lee et al. (2011) AJ 738187

  • SDSS stellar spectroscopy part – low

resolution spectra

  • Started to divide disk by abundance

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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Starting to test model predictions

0.0 0.1 0.2 0.3 0.4 N/Ntotal

0.1 ≤ |Z| < 0.8 kpc Thin 0.8 ≤ |Z| < 2.4 kpc Thin 0.1 ≤ |Z| < 0.8 kpc Thick 0.8 ≤ |Z| < 2.4 kpc Thick

0.0 0.2 0.4 0.6 0.8 Eccentricity (e) 0.0 0.1 0.2 0.3 0.4 N/Ntotal

0.1 ≤ |Z| < 0.8 kpc Full

0.0 0.2 0.4 0.6 0.8 Eccentricity (e)

0.8 ≤ |Z| < 2.4 kpc Full

  • Gas rich merger “favoured”

Lee et al. (2011) AJ 738187 Thin disk Thick disk Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 19

No thick disk?

Bovy et al. (2011) arXiv:1111.1724 arXiv:1111.6585

  • Internal processes “favoured”

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 20

???

Nissen & Schuster (2010) A&A 511 L10 Vtot>180km s-1 [Fe/H]> –1.6 δTeff 5200 - 6300 K d<335 pc

All blue and red stars have halo kinematics + have thick disk kinematics

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 21

???

Nissen & Schuster (2010) A&A 511 L10

Halo Disk

Vtot>180km s-1 [Fe/H]> –1.6 δTeff 5200 - 6300 K d<335 pc Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 22

???

Nissen & Schuster (2010) A&A 511 L10

So far no good interpretation for what this is – dual inner halo? Thick disk meets halo? Halo Disk

Vtot>180km s-1 [Fe/H]> –1.6 δTeff 5200 - 6300 K d<335 pc Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 23
  • Parallax horizon for K5III stars

10 kpc 1 2 5 10 20% 20%

AV = 0 AV = 5 mag

1 2 5 10

Sun

Illustration by Lennart Lindegren

Bulge

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 24
  • Parallax horizon for K5III stars

10 kpc 1 2 5 10 20% 20%

AV = 0 AV = 5 mag

1 2 5 10

Bulge

But velocities missing below G=17 and detailed elemental abundances are also missing

Illustration by Lennart Lindegren

Sun

Gaia

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 25

Multiplex spectroscopy

  • Gaia follow-up is being pursued by the European

community in two ways – using existing facilities and setting up a new infrastructure of spectrographs

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 26

Gaia-ESO Survey

  • One of two ESO public spectroscopic surveys,

PIs: Gerry Gilmore and Sofia Randich

  • 300 nights over 5 years on

VLT with FLAMES

  • High-resolution spectroscopy of all major

stellar components(105 stars) and open clusters

  • Swedish members: Thomas Bensby leads the
  • bservers, Andreas Korn is leading the high-

resolution abundance analysis, >10 people in Lund and Uppsala are members, SF member of Steering Committee

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 27

Gaia-ESO Survey

  • Observations have started

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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… future spectrographs

  • 4MOST – massive multiplex for NTT or

VISTA

  • MOONS – NIR “upgrade” of FLAMES on

VLT

  • WEAVE – massive multiplex for William

Herschel Telescope

➡All are about 50-50 Gaia follow-up and

extra-galactic science

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 29

There is a need for high R

1 2 3 4 5 6 7 8 9 10 10 1 10 2 10 3 10 4 10 5 10 6 10 7 Separation (in units of obs. std error) Minimum sample size for p = 0.01

0 1 2 3 4 5 6 7 8 9 10 Separation (in units of std. error) 107 106 105 104 103 102 101

At some point large numbers does not help you!

# stars needed to get a low probability of false detection (p = 0.01)

1.

With L. Lindegren Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 30

There is a need for high R

Resolution Parameters

F-GV, KIII

Abundance accuracies >5000 Teff, log g, [Fe/H], (α-elements?) 0.2 dex ~20000 Teff, log g, [Fe/H], α- elements, 5–10 additional elements (Fe < -1?) 0.1-0.15 dex ≥40000 Teff , log g, [Fe/H], α- elements, iron-peak, r- and s-process elements <0.05dex

Based on a talk by Vanessa Hill

2.

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012

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SLIDE 31
  • Parallax horizon for K5III stars

10 kpc 1 2 5 10 20% 20%

AV = 0 AV = 5 mag

1 2 5 10 Illustration by Lennart Lindegren

  • With Gaia we will be able to do what we

do locally today on a completely new scale

  • We will be able to constrain the bar and

spiral arm potential

  • Is the Galaxy going to look nice and

smooth in abundance+kinematic space or will we be in for a “chock”?

➡connecting directly to galaxy formation

Sofia Feltzing: Talk given at Stars for all, Lund 2012

tisdag den 7 februari 2012