The Radial Acceleration Relation of Galaxies

Transcription

1 The Radial Acceleration Relation of Galaxies Federico Lelli ESO Fellow (Garching, Germany) In collaboration with Stacy McGaugh (Case Western Reserve University) James Schombert (University of Oregon) Marcel Pawlowski (University of California - Irvine)

2 Database for 175 Late-Type Galaxies at z~0 (spirals and dwarf irregulars): astroweb.case.edu/sparc Lelli, McGaugh, Schombert 2016, AJ

3 175 HI Rotation Curves from Literature WSRT - 30 years of radio interferometric observations - PhD theses from the University of Groningen Begeman 1987; Broeils 1992; Verheijen 1997; de Blok 1997; Swaters 1999; Noordermeer 2005; Lelli other studies

4 175 HI Rotation Curves from Literature WSRT - 30 years of radio interferometric observations - PhD theses from the University of Groningen Begeman 1987; Broeils 1992; Verheijen 1997; de Blok 1997; Swaters 1999; Noordermeer 2005; Lelli other studies Homogeneous Photometry at 3.6 μm Spitzer - 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.

5 HSBs Widest possible range of disk properties LSBs 4 dex Basically any known galaxy type with a rotating HI disk. Dwarf Irrs 5 dex Spirals Mgas/Mbar

6 Example: High-Mass, High-Density Spiral Spitzer 3.6 μm 2Φbar(R,z) = 4πG ρbar(r,z) Vflat total disk bulge gas - 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

7 Example: Low-Mass, Low-Density Dwarf Spitzer 3.6 μm Vflat 2Φbar(R,z) = 4πG ρbar(r,z) - Vertical Structure: total gas disk 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

8 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

9 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

10 Radial Acceleration Relation ~2700 independent points at different R For all galaxies: ϒdisk = 0.5 M /L ϒbulge = 0.7 M /L McGaugh+2016, PRL Lelli+2017, ApJ Total Acceleration: V2obs /R = - Φtot Baryonic Force: V2bar /R= - Φbar 2Φbar= 4πG ρbar

11 Radial Acceleration Relation g obs =gb ar For all galaxies: ϒdisk = 0.5 M /L ϒbulge = 0.7 M /L g obs = gb ar g0 gobs = gb ar 1 e g Total Acceleration: V2obs /R = - Φtot b ar / g0 McGaugh+2016, PRL Lelli+2017, ApJ Baryonic Force: V2bar /R= - Φbar 2Φbar= 4πG ρbar

12 Very different galaxies but ONE relation V2obs /R = - Φtot V2bar /R= - Φbar 2Φbar= 4πG ρbar

13 Building up the Radial Acceleration Relation Large Diversity in Rotation Curves Regularity in Acceleration Plane Lelli et al. (2017), ApJ

14 Is There Any Intrinsic Scatter? Uncertainties drive scatter! err(gbar) ϒ*, 3D geometry err(gobs) Dist, Inc, Vrot σobs2 = σerr2 + σint2 σobs measured rms σerr error propagation σint consistent with zero! McGaugh+2016, PRL; Lelli+2017, ApJ

15 We can infer the DM profile from the baryons! From the observations: g DM =gtot gba r =F (gba r ) 2 R For a spherical DM halo: M DM (R)= F (g ba r ) G For our fiducial fitting F: gba r R2 M DM (R)= G exp( g ba r / g0 ) 1

16 We can infer the DM profile from the baryons! From the observations: g DM =gtot gba r =F (gba r ) 2 R For a spherical DM halo: M DM (R)= F (g ba r ) G For our fiducial fitting F: gba r R2 M DM (R)= G exp( g ba r / g0 ) 1 Purely Empirical Relations (accuracy ~30%). Only inputs are M/L and Poisson s equation.

17 Open Issues for ΛCDM models: 1. Why is the RAR scatter so small? Is this consistent with stochastic hierarchical merging?

18 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) Vflat4 = Mbar / (g0g) Observed BTFR. Whatever sets the RAR should also set the BTFR.

19 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) Vflat4 = Mbar / (g0g) 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)!

20 Conclusions: - There is a local coupling between baryons and DM in galaxies over ~5 dex in Mbar. - There is an acceleration scale ~10-10 ms. -2

21 Questions?

22 Radial Acceleration Relation for ETGs X-rays ETGs: gobs from hot gas haloes in hydrostatic equilibrium (Humprey+2006,2009,2012) Rotating ETGs: gobs from stellar kinematics + Jeans Axisymmetric Models (Atlas3D - Cappellari+2010) Dwarf Spheroidals: gobs from stellar kinematics + Jeans Spherical Models (many many references...) Lelli+2017a, ApJ

23 MCMC Fits to Individual Galaxies Extremely tight relation! σobs = dex (~10%) err(vrot) ~ 10% Pengfei Li et al. (submitted)

24 A Natural outcome of galaxy formation? AM-based Models: Di Cintio & Lelli 2016 Desmond 2017 Navarro+2017 Numerical Sims: Keller & Wadsley 2016 Ludlow+2017 Tenneti σ discrepancy! Basic Results: 1) Similar relation but shape is model-dep. 2) Scatter is too large: Desmond 2017, MNRAS σobs2 = σint2+σerr2 Can t forget errors!

25 Residuals vs Local Galaxy Properties Lelli+2017, ApJ

26 Residuals vs Global Galaxy Properties Lelli+2017, ApJ

27 Alternative versions of the RAR