baryons, dark matter or non-circular motions? Isabel Santos-Santos - - PowerPoint PPT Presentation

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baryons, dark matter or non-circular motions? Isabel Santos-Santos - - PowerPoint PPT Presentation

Sep 18, 2022 149 likes •388 views

Diversity of dwarf galaxy rotation curves: baryons, dark matter or non-circular motions? Isabel Santos-Santos Postdoctoral Research Fellow (UVic) + Julio Navarro, The Apostle Collaboration Diversity of rotation curve shapes in observed disc

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Diversity of dwarf galaxy rotation curves: baryons, dark matter or non-circular motions?

Isabel Santos-Santos

Postdoctoral Research Fellow (UVic) + Julio Navarro, The Apostle Collaboration

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Isabel Santos Santos 2

Diversity of rotation curve shapes in observed disc galaxies

Vmax ≈ 80 km/s

  • Dwarf galaxies

present a wide diversity of rotation curve shapes

  • CDM predicts a

single profile for a given velocity scale, unlike

  • bserved rotation

curves

  • Some galaxies are

consistent with CDM, others are not: either “cuspier” or “cored”

Diversity of dwarf Galaxy rotation curves problem (Oman+15)==“Cusp-core problem” (see Moore94, de Blok+08, Oh+15)

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Diversity of rotation curve shapes in observed disc galaxies

Diversity can be quantified by comparing:

Isabel Santos Santos

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Diversity of rotation curve shapes in observed disc galaxies

SPARC (Lelli+17) LITTLE THINGS (Oh+11,Iorio+17)

Velocity at 2 kpc [km/s] Maximum velocity

See Oman+15,Santos-Santos+18

Santos-Santos+19 in prep

Isabel Santos Santos

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Diversity of rotation curve shapes in observed disc galaxies

SPARC (Lelli+17) LITTLE THINGS (Oh+11,Iorio+17)

Velocity at 2 kpc [km/s] Maximum velocity

See Oman+15,Santos-Santos+18

Dwarf galaxy mass range: Vmax ~50-100 km/s

Santos-Santos+19 in prep

Isabel Santos Santos

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Diversity of rotation curve shapes in observed disc galaxies

SPARC (Lelli+17) LITTLE THINGS (Oh+11,Iorio+17)

Velocity inner radii: at 2 kpc Velocity outer radii: maximum velocity

See Oman+15,Santos-Santos+18

Dwarf galaxy mass range: Vmax ~50-100 km/s

Possible solutions to the “Rotation curve diversity problem”

a) Galaxy formation can modify DM mass profiles? b) DM is not CDM (e.g., self-interacting, SIDM)? c) Uncertainties in data modeling and gas non-circular motions?

Isabel Santos Santos

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A) Galaxy formation can modify DM profile: baryon-induced cores

  • Supernova explosions may lead to

massive gas outflows that cause variations in the gravitational potential and the consequent reduction of dark matter in the inner regions (e.g., Navarro+96, Pontzen

& Governato12)

  • This creates cores in the dark

matter that may be reversed if baryons are re-accreted (Benitez-

Llambay+18, Read+16)

  • It can lead to large rotation curve

diversity (see Santos-Santos+18 with NIHAO

simulated galaxies) Benitez-Llambay+18 Isabel Santos Santos

Log (Mgas/Mdark) Log (Mdark/Msun) Log (r/kpc) SFR Time/Gyr

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A) Galaxy formation can modify DM profile: baryon-induced cores

  • Supernova explosions may lead to

massive gas outflows that cause variations in the gravitational potential and the consequent reduction of dark matter in the inner regions (e.g., Navarro+96, Pontzen

& Governato12)

  • This creates cores in the dark

matter that may be reversed if baryons are re-accreted (Benitez-

Llambay+18, Read+16)

  • It can lead to large rotation curve

diversity (see Santos-Santos+18 with NIHAO

simulated galaxies)

Benitez-Llambay+18

Santos-Santos+18 Isabel Santos Santos

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B) Self-interacting dark matter (SIDM)

SIDM → “heat transfer” from the outside in → reduction of dark matter in the inner regions (e.g.Kamada+16) If baryons accumulate to the center, core size decreases → rotation curve diversity

(Kaplinghat+14, Ren+18)

Vcirc [km/s] ρ [Msun/kpc3] R [kpc] R [kpc]

SIDM-only SIDM with baryons Vbar Vtot

Isabel Santos Santos

Santos-Santos+19 in prep

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C) Non-circular motions?

Oman+19

Simulated galaxies “observed” (Oman+19, see also Hayashi&Navarro06,Read+16,Pineda+17)

  • Synthetic observations of the HI velocity field, using same tools as in observations
  • Rotation curves derived using 3D-BAROLO (DiTeodoro+Fraternali15) “tilted-ring” model
  • If there are non-circular motions in the gas, velocities are generally underestimated

Circular velocity curve Azimuthal gas vel. pressure support corrected Kinematic model pressure support corrected, different orientations of line-of-sight Φ

Cusp?

  • r

Core?

Isabel Santos Santos

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How do these scenarios match the diversity?

Isabel Santos Santos

Santos-Santos+19 in prep

V2kpc [km/s] Vmax [km/s]

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How do these scenarios match the diversity?

Isabel Santos Santos

Santos-Santos+19 in prep

V2kpc [km/s] Vmax [km/s] V2kpc [km/s]

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How do these scenarios match the diversity?

Isabel Santos Santos

Santos-Santos+19 in prep

V2kpc [km/s] V2kpc [km/s] Vmax [km/s] Vmax [km/s]

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How do these scenarios match the diversity?

Isabel Santos Santos

Santos-Santos+19 in prep

V2kpc [km/s] V2kpc [km/s] Vmax [km/s] Vmax [km/s]

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How do these scenarios match the diversity?

Isabel Santos Santos

Santos-Santos+19 in prep

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V2bar/V2 Baryon contribution to total velocity at 2kpc

How to tell these scenarios apart?: correlations

Isabel Santos Santos

Santos-Santos+19 in prep

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V2bar/V2 Baryon contribution to total velocity at 2kpc V2DM/V2NFW Dark matter core size at 2kpc

How to tell these scenarios apart? correlations

Isabel Santos Santos

Santos-Santos+19 in prep

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V2bar/V2 Baryon contribution to total velocity at 2kpc V2DM/V2NFW Dark matter core size at 2kpc

How to tell these scenarios apart? correlations

Isabel Santos Santos

Santos-Santos+19 in prep

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How to tell these scenarios apart? correlations

Baryon contribution to total velocity at 2kpc Dark matter core size at 2kpc

Isabel Santos Santos

Santos-Santos+19 in prep

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How to tell these scenarios apart? correlations

Baryon contribution to total velocity at 2kpc

Vdm

2 = V2 - Vbar 2 Isabel Santos Santos

Santos-Santos+19 in prep Dark matter core size at 2kpc

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Summary/future work:

A model that explains diversity has to explain correlations as well

  • Baryon-induced cores
  • can reproduce the largest cores
  • lacks the most extreme cuspy cases (i.e., galaxies with low baryonic contribution in their

inner regions)

  • SIDM+observed galaxies
  • Produce cored galaxies in general, but not as extreme as observed.
  • There is no trend between the size of the core and the importance of baryons.
  • Mock observations of CDM+baryons (no core) simulated galaxies
  • reproduce the range of diversity in core size
  • and the trend with baryonic contribution, though more statistics is needed.

Isabel Santos Santos

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Summary/future work:

A model that explains diversity has to explain correlations as well

  • Baryon-induced cores
  • can reproduce the largest cores
  • lacks the most extreme cuspy cases (i.e., galaxies with low baryonic contribution in their

inner regions)

  • SIDM+observed galaxies
  • Produce cored galaxies in general, but not as extreme as observed.
  • There is no trend between the size of the core and the importance of baryons.
  • Mock observations of CDM+baryons (no core) simulated galaxies
  • reproduce the range of diversity in core size
  • and the trend with baryonic contribution, though more statistics is needed.
  • Exploring other possibilities:

i. CDM+hydro simulations with a variety of SF density thresholds ii. CDM+hydro simulations with different feedback schemes iii. SIDM+hydro simulations, with baryonic outflows

Isabel Santos Santos

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Thank you.