the radial acceleration relation of...
TRANSCRIPT
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The Radial Acceleration The Radial Acceleration
Relation of GalaxiesRelation of Galaxies
Federico Lelli Federico Lelli ESO Fellow (Garching, Germany)ESO Fellow (Garching, Germany)
In collaboration withIn collaboration withStacy McGaughStacy McGaugh (Case Western Reserve University) (Case Western Reserve University)James SchombertJames Schombert (University of Oregon) (University of Oregon)Marcel Pawlowski Marcel Pawlowski (University of California - Irvine)(University of California - Irvine)
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Database for 175 Late-Type Galaxies at z~0
(spirals and dwarf irregulars):
astroweb.case.edu/SPARC
Lelli, McGaugh, Schombert 2016, AJ
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
175 HI Rotation Curves from Literature - 30 years of radio interferometric observations
- PhD theses from the University of GroningenBegeman 1987; Broeils 1992; Verheijen 1997; de Blok 1997;
Swaters 1999; Noordermeer 2005; Lelli 2013 + other studies
WSRT
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Spitzer
Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
175 HI Rotation Curves from Literature - 30 years of radio interferometric observations
- PhD theses from the University of GroningenBegeman 1987; Broeils 1992; Verheijen 1997; de Blok 1997;
Swaters 1999; Noordermeer 2005; Lelli 2013 + other studies
Homogeneous Photometry at 3.6 μm - Optimal tracer of the stellar mass: M* = ϒ*
L
- Smaller variations of ϒ* in the NIR than optical Verheijen 2001; Bell & de Jong 2001; Martinsson+2013; Meidt+2014;
McGaugh & Schombert 2014; Schombert & McGaugh 2014;
Querejeta+2015; Röck+2015; Herrmann+2016; Norris+2016.
WSRT
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Widest possible range of disk properties
Dwarf Irrs Spirals5 dex
LSB
sH
SB
s
Mgas/Mbar
4 de
x
Basically any known galaxy type with a rotating HI disk.
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Example: High-Mass, High-Density Spiral
gas
disk
Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
total
bulge
Vflat
Spitzer 3.6 μm
∇2Φbar
(R,z) = 4πG ρbar
(R,z)
- Vertical Structure:Disks: exp(-z/hz) with hz∝hR
Bulges: spherical symmetry
- Stellar mass-to-light ratio:ϒ
* = 0.5 M⊙/L⊙ for disks
ϒ* = 0.7 M⊙/L⊙ for bulges
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Example: Low-Mass, Low-Density Dwarf
gas
disk
total
Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Vflat
Spitzer 3.6 μm
∇2Φbar
(R,z) = 4πG ρbar
(R,z)
- Vertical Structure:Disks: exp(-z/hz) with hz∝hR
Bulges: spherical symmetry
- Stellar mass-to-light ratio:ϒ
* = 0.5 M⊙/L⊙ for disks
ϒ* = 0.7 M⊙/L⊙ for bulges
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
1. Basic Data & Structural Relations: Lelli+2016a, AJ
2. Baryonic TF Relation: Lelli+2016b, ApJL
3. Central Density Relation: Lelli+2016c, ApJL
4. Radial Acceleration Relation (I): McGaugh+2016, PRL
5. Radial Acceleration Relation (II): Lelli+2017a, ApJ
6. Testing DM Halo Profiles: Katz+2017, MNRAS
7. Testing Emergent Gravity: Lelli+2017b, MNRAS
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
1. Basic Data & Structural Relations: Lelli+2016a, AJ
2. Baryonic TF Relation: Lelli+2016b, ApJL
3. Central Density Relation: Lelli+2016c, ApJL
4. Radial Acceleration Relation (I): McGaugh+2016, PRL
5. Radial Acceleration Relation (II): Lelli+2017a, ApJ
6. Testing DM Halo Profiles: Katz+2017, MNRAS
7. Testing Emergent Gravity: Lelli+2017b, MNRAS
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
For all galaxies:
ϒdisk
= 0.5 M⊙/L⊙
ϒbulge
= 0.7 M⊙/L⊙
~2700 independent points at different R
Total Acceleration: V2obs /R = -∇Φ
tot
Baryonic Force:V2
bar /R= -∇Φbar
∇2Φbar
= 4πG ρbar
McGaugh+2016, PRL
Lelli+2017, ApJ
Radial Acceleration Relation
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
For all galaxies:
ϒdisk
= 0.5 M⊙/L⊙
ϒbulge
= 0.7 M⊙/L⊙
Total Acceleration: V2obs /R = -∇Φ
tot
Baryonic Force:V2
bar /R= -∇Φbar
∇2Φbar
= 4πG ρbar
gobs=gbar
1−e−√gbar /g0
gobs=√gb ar g0
gobs=gb ar
McGaugh+2016, PRL
Lelli+2017, ApJ
Radial Acceleration Relation
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Very different galaxies but ONE relation
V2bar /R= -∇Φ
bar
∇2Φbar
= 4πG ρbar
Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
V2obs /R = -∇Φ
tot
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Building up the Radial Acceleration Relation
Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Lelli et al. (2017), ApJ
Large Diversity in Rotation Curves Regularity in Acceleration Plane
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Is There Any Intrinsic Scatter?
Uncertainties drive scatter!
err(gbar
) →
ϒ
*, 3D geometry
err(gobs
) → Dist, Inc, Vrot
σobs
2 = σerr2 + σint
2
σobs→ measured rms
σerr→ error propagation
σint→ consistent with zero!
McGaugh+2016, PRL; Lelli+2017, ApJ
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
gDM=gtot−gba r=F (gbar)From the observations:
For a spherical DM halo:
For our fiducial fitting F:
M DM (R)=R2
GF (gbar)
M DM (R)=R2
Ggbar
exp(√gbar / g0)−1
We can infer the DM profile from the baryons!
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
gDM=gtot−gba r=F (gbar)From the observations:
For a spherical DM halo:
For our fiducial fitting F:
M DM (R)=R2
GF (gbar)
M DM (R)=R2
Ggbar
exp(√gbar / g0)−1
We can infer the DM profile from the baryons!
Purely Empirical Relations (accuracy ~30%).
Only inputs are M/L and Poisson’s equation.
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Open Issues for ΛCDM models:
1. Why is the RAR scatter so small?
Is this consistent with stochastic hierarchical merging?
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Open Issues for ΛCDM models:
1. Why is the RAR scatter so small?
Is this consistent with stochastic hierarchical merging?
2. Why is the RAR outer slope ~0.5?
gobs
=√(g0gbar) → Vflat
4 = M
bar / (g
0G) → Observed BTFR.
Whatever sets the RAR should also set the BTFR.
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Open Issues for ΛCDM models:
1. Why is the RAR scatter so small?
Is this consistent with stochastic hierarchical merging?
2. Why is the RAR outer slope ~0.5?
gobs
=√(g0gbar) → Vflat
4 = M
bar / (g
0G) → Observed BTFR.
Whatever sets the RAR should also set the BTFR.
3. Why an acceleration scale? What sets its value?
Different roles of g0: baryon-to-DM transition (RAR)
& global baryon-to-DM content (BTFR)!
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Conclusions:
Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
- There is a local coupling between baryons
and DM in galaxies over ~5 dex in Mbar
.
- There is an acceleration scale ~10-10 m s-2.
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Questions?
Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Radial Acceleration Relation for ETGs
X-rays ETGs: g
obs from hot gas haloes
in hydrostatic equilibrium (Humprey+2006,2009,2012)
Rotating ETGs: g
obs from stellar kinematics +
Jeans Axisymmetric Models (Atlas3D - Cappellari+2010)
Dwarf Spheroidals: g
obs from stellar kinematics +
Jeans Spherical Models (many many references...)
Lelli+2017a, ApJ
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
MCMC Fits to Individual Galaxies
Extremely tight relation!
σobs
= 0.054 dex (~10%)
err(Vrot
) ~ 10%
Pengfei Li et al. (submitted)
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Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Desmond 2017, MNRAS
AM-based Models:Di Cintio & Lelli 2016Desmond 2017Navarro+2017
Numerical Sims: Keller & Wadsley 2016Ludlow+2017 Tenneti+2017
Basic Results:1) Similar relation but shape is model-dep.
2) Scatter is too large:
σobs
2 = σint2+σerr
2
Can’t forget errors!
A “Natural” outcome of galaxy formation?
3.5σ discrepancy!
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Residuals vs Local Galaxy Properties
Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Lelli+2017, ApJ
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Residuals vs Global Galaxy Properties
Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies
Lelli+2017, ApJ
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Alternative versions of the RAR
Federico Lelli (ESO Fellow) The Radial Acceleration Relation of Galaxies