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Dark matter local density determination based on recent observations Pablo Fernndez de Salas Oskar Klein Centre for Cosmoparticle Physics, Stockholm University TAUP 2019 Toyama 11th September 2019 The presence of dark matter (DM)

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Dark matter local density determination based on recent

  • bservations

Pablo Fernández de Salas

Oskar Klein Centre for Cosmoparticle Physics, Stockholm University

TAUP 2019 – Toyama – 11th September 2019

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The presence of dark matter (DM)

  • S. Blais-Ouellette et al., Astron. J. 118 (1999) 2123

Image Credit: Russ Carroll, Robert Gendler, & Bob Franke; Dan Zowada Memorial Observatory

Galaxy clusters

(Fritz Zwicky 1933) Coma cluster

Rotation curves

(Vera Rubin)

CMB anisotropies

Planck satellite 2018

Bullet cluster

Image Credit: X-ray: NASA/CXC/CfA/ M. Markevitch et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/ D.Clowe et al. Optical: NASA/STScI; Magellan/ U.Arizona/ D.Clowe et al. Image Credit: Sloan Digital Sky Survey

Large-Scale Structures

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In order to detect dark matter...

  • Direct detection
  • spin (in)dependent
  • annual modulation
  • Production at

colliders

  • Mono-X (missing ET)
  • Resonances
  • Indirect detection

(astroparticle excesses)

  • gamma rays
  • positrons
  • neutrinos
  • ...

DM DM SM SM colliders direct indirect

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...we must know how much DM is there to be detected

  • Direct detection
  • spin (in)dependent
  • annual modulation
  • Indirect detection

(astroparticle excesses)

  • gamma rays
  • positrons
  • neutrinos
  • ...
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Common methods to estimate ρDM,⊙

  • Local methods
  • Vertical z-Jeans equation
  • Distribution function fitting
  • Global methods
  • Rotation curve
  • Distribution function fitting
  • Small volume around the Solar neighbourhood
  • Less dependence on a specific DM profile
  • Large volume beyond the Solar neighbourhood
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Common methods to estimate ρDM,⊙

Common assumptions:

  • Equilibrium (steady state)
  • Axisymmetry

From visible tracers to DM:

  • Collisionless Boltzmann equation
  • Poisson equation
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Methods to estimate ρDM,⊙

Galactic matter density

  • Rotation curve method

Model construction Observational estimate

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Methods to estimate ρDM,⊙

Galactic matter density

  • Rotation curve method
  • z-Jeans equation method

1D z-Jeans equation method

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Methods to estimate ρDM,⊙

1) Choose one or more tracer populations νi 2) Relate νi to the gravitational potential Φ 3) Connect Φ with ρDM → connect ν with ρDM

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Previous estimates of ρDM,⊙

[J.I. Read, J.Phys G41 (2014) 063101]

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Previous estimates of ρDM,⊙

[Plot from Q. Xia et al., MNRAS 458 (2016) 3839] [Smith et al., arXiv:1111.6920] LJ [Garbari et al., arXiv:1206.0015] LJ [Zhang et al., arXiv:1209.0256] LJ [Bovy & Rix, arXiv:1309.0809] DF [Bienaymé et al., arXiv:1406.6896] LJ [Piffl et al., arXiv:1406.4130] DF [McKee et al., arXiv:1509.05334] LJ [Q. Xia et al., MNRAS 458 (2016) 3839]

Xia+16

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ESA/Gaia satellite mission

  • Launch

19 December 2013

  • Operation since

25 July 2014

  • Nominal mission (5 years)

July 2019

  • Mission extended to

31 December 2022

  • DR1

(14 months) 14 September 2016

  • DR2

(22 months) 25 April 2018

  • EDR3

third quarter 2020

  • DR3

(34 months) second half 2021

  • Full Data Release

TBD

Data Release Mission timeline

Credit for the images: ESA

Gaia DR1: A.G.A. Brown et al., A&A 595 (2016) A2 Gaia DR2: A.G.A. Brown et al., A&A 616 (2018) A1

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Gaia Data Release (DR) overview

(TGAS) (3 < G < 21)

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Gaia DR2: Galactic density map

ESA/Gaia/DPAC, CC BY-SA 3.0 IGO

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Recent estimates of ρDM,⊙

Method:

  • Rotation curve
  • Distribution Function
  • Vertical Jeans eq.

(dark colors: Gaia data)

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Recent estimates of ρDM,⊙

Method:

  • Rotation curve
  • Distribution Function
  • Vertical Jeans eq.

(dark colors: Gaia data)

[Schutz et al., arXiv:1711.03103]

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Why so difgerent?

  • Differences in the data?

Differences found when same survey is used

  • Differences in the methods?

Different methods cover different regions (The Galaxy is neither in equilibrium nor axisymmetric)

  • Disequilibria effects?

Two population HRD [e.g. A. Helmi+ arXiv:1806.06038] Phase-space spirals [e.g. T. Antoja+ arXiv:1804.10196]

  • New physics?

Dark disk [e.g. J.I. Read, arXiv:0803.2714, C.W. Purcell, arXiv:0906.5348,

  • J. Fan, arXiv:1303.1521]
  • Uncertainties in baryonic data?

Underestimated cold gas? [A. Widmark, arXiv:1811.07911]

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Why so difgerent?

  • Differences in the data?

Differences found when same survey is used

  • Different populations:
  • Different age
  • Can be affected differently by disequilibria

[J. Buch et al., JCAP 04 (2019) 026]

Stellar populations: A stars F stars G stars

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Why so difgerent?

  • Differences in the methods?

Different methods cover different regions (The Galaxy is neither in equilibrium nor axisymmetric)

  • Different methods:
  • Different assumptions
  • Different volume coverage
  • Can be affected differently by disequilibria

Method:

  • Rotation curve
  • Distribution Function
  • Vertical Jeans eq.

(dark colors: Gaia data)

  • McKee, Xia, Sivertsson: larger z ~ kpc
  • Schutz, Buch, Widmark: smaller z < 200 pc
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Disequilibria efgects

[T. Antoja, Nature 561 (2018) 360]

  • Phase-space spirals

Possible source:

  • Sagittarius dwarf passage

[Laporte+, arXiv:1808.00451]

  • Buckling of the bar

[Khoperskov+, arXiv:1811.09205]

Image credits: ESA/Gaia/DPAC, CC BY-SA 3.0 IGO

  • Two populations in HR diagram

Possible source:

  • Gaia-Enceladus merger

[Helmi+, arXiv:1806.06038]

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Why so difgerent?

  • New physics?

Dark disk [e.g. J.I. Read, arXiv:0803.2714, C.W. Purcell, arXiv:0906.5348,

  • J. Fan, arXiv:1303.1521]

[J. Buch et al., arXiv:1808.05603]

  • Dark disk:
  • Cannot explain alone differences

in populations

  • Can explain differences between

local and rotation curve methods

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Why so difgerent?

  • Uncertainties in baryonic data?

Underestimated cold gas? [A. Widmark, arXiv:1811.07911]

[A. Widmark, A&A 623 (2019) A30]

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Why so difgerent?

  • Uncertainties in baryonic data?

Underestimated cold gas? [A. Widmark, arXiv:1811.07911] [P .F . de Salas et al., arXiv:1906.06133]

Data from:

[A.-C. Eilers et al., Astro. J. 871 (2019) 120]

Baryonic model B1 from: Baryonic model B2 from:

[E. Pouliasis et al., arXiv:1611.07979] [A. Misiriotis et al., A&A 459 (2006) 113]

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Stellar acceleration: Radial Velocity Method

[A. Ravi et al., arXiv:1812.07578] [H. Silverwood et al., arXiv:1812.07581]

  • Same technique as exoplanet searches
  • Doppler spectroscopy
  • Less modelling assumptions
  • Since the Sun is also accelerating, we

need to move out from R⊙

  • Local acceleration:
  • Needed sensitivity in 10 years:
  • Other Doppler shift sources are stronger

(best scenario lonely stars)

  • Disentangle DM contribution as complex

as in other methods

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Stellar acceleration: Radial Velocity Method

[Figure from A. Ravi et al., arXiv:1812.07578] [A. Ravi et al., arXiv:1812.07578] [H. Silverwood et al., arXiv:1812.07581]

  • Same technique as exoplanet searches
  • Doppler spectroscopy
  • Less modelling assumptions
  • Since the Sun is also accelerating, we

need to move out from R⊙

  • Local acceleration:
  • Needed sensitivity in 10 years:
  • Other Doppler shift sources are stronger

(best scenario lonely stars)

  • Disentangle DM contribution as complex

as in other methods

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Stellar acceleration: Radial Velocity Method

[A. Ravi et al., arXiv:1812.07578] [H. Silverwood et al., arXiv:1812.07581]

  • Same technique as exoplanet searches
  • Doppler spectroscopy
  • Less modelling assumptions
  • Since the Sun is also accelerating, we

need to move out from R⊙

  • Local acceleration:
  • Needed sensitivity in 10 years:
  • Other Doppler shift sources are stronger

(best scenario lonely stars)

  • Disentangle DM contribution as complex

as in other methods

[Figure from A. Ravi et al., arXiv:1812.07578]

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Voyage 2050 white paper

  • It can probe a very local environment (~ 150 AU) 1 AU = 4.85e-6 pc
  • It requires new propulsion methods: Breakthrough Starshot laser project
  • Many technological challenges (propulsion, tracking, power...)

[J. Bergé et al., arXiv:1909.00834]

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Conclusions

  • Present:
  • Recent precise information on hand (Gaia), but a good Galactic model missing
  • Under equilibrium, axisymmetry and typical baryonic models: ρDM,⊙ = 0.3–0.5 GeV/cm³
  • Larger measured values can be related to disequilibria in the Milky Way
  • Uncertainties dominated by limitations in the methods and disequilibria in the Galaxy
  • Future:
  • Combine different (old and new) methods and data
  • Develop a better model for the Milky Way

James Binney: “Non-stationary phenomena play key roles in the Galaxy’s evolution, but they must be

excluded from the basic model, which will inevitably be an equilibrium model. Only after its construction will it be decorated with spiral arms, warps and streams.”

[Proceedings for the IAU Symposium 330, arXiv:1706.01374]

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Gaia DR2 astrometric precision

Proper motion uncertainties: 0.06 mas/yr (for G < 15 mag) 0.2 mas/yr (for G = 17 mag) 1.2 mas/yr (for G = 20 mag)

A.G.A. Brown et al., A&A. 616 (2018) A1

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Rotation curve method

[P .F . de Salas et al., arXiv:1906.06133]

  • Survey: Gaia DR2 + 2MASS + WISE + APOGEE
  • Studied region:
  • Tracer population:
  • Baryonic models:
  • Red-giant stars

[A.-C. Eilers et al., Astro. J. 871 (2019) 120]

Miyamoto-Nagai discs (B1) Based on: Double expon. Discs (B2) Based on:

[E. Pouliasis et al., arXiv:1611.07979] [A. Misiriotis et al., A&A 459 (2006) 113]

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Rotation curve method

[P .F . de Salas et al., arXiv:1906.06133]

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Distribution Function fjtting method

Notice!

  • equilibrium approximation
  • Jeans’ theorem: The DF of an equilibrium stellar system

depends on (x,v) only through integrals of motion Ii(x,v)

  • Computationally demanding
  • Axisymmetry is not required
  • Choose a multicomponent Galactic potential Φ
  • Built a DF f(J) in terms of convenient constants of

motion (actions Ji) for different components

  • Fit parameters of Φ and f(J) to observations

[J. Binney, arXiv:1207.4910] [P .J. McMillan et al., arXiv:1303.5660] [J. Bovy et al., arXiv:1309.0809] [T. Piffl et al., arXiv:1406.4130] [J. Binney et al., arXiv:1509.06877] [D.R. Cole et al., arXiv:1610.07818] [J. L. Sanders et al., arXiv:1511.08213] [J. Binney, arXiv:1706.01374]

Selected list of recent works on the subject

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Moment method: Jeans equations

Start from the steady-state collisionless Boltzmann equation Write it in cylindrical coordinates Multiply by and integrate over all velocities (axisymmetry assumed)

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Rotation curve method

  • Circular velocity
  • R-Jeans equation

Connection with theoretical ρDM Connection with tracer’s observations

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Vertical Jeans equation method

tilt term

  • Poisson equation
  • z-Jeans equation

rotation curve term

Ignoring induces a < 10% error

[J.I. Read, J. Phys G41 (2014) 063101]

Assuming flat rotation curve at R⊙

Notice!

  • equilibrium approximation
  • axisymmetry
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1D z-Jeans equation method

[S. Sivertsson et al., MNRAS 478 (2018) 1677]

  • Survey: SDSS-SEGUE G-dwarf
  • Studied region:
  • Stellar populations:
  • α-young

α-old

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Vertical Jeans equation method

[J. Buch et al., JCAP 04 (2019) 026]

  • Survey: Gaia DR2 + 2MASS

4445 stars 37707 stars 43332 stars

  • Studied region:
  • Stellar populations:
  • A stars

G stars F stars

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Vertical Jeans equation method

[A. Widmark, A&A 623 (2019) A30]

8 samples with MG from 3.0–6.3 If excess interpreted in terms of DM, at z=0

  • Survey: Gaia DR2

~ 8 x 23 000 stars

  • Studied region:
  • Stellar populations: