Victor P. Debattista Secular Evolution in Disc Galaxies

 … into bulge+disc to test for secular evolution of classical bulges and how this affects the M BH - σ e relation  … in the vertical direction to understand the thin/thick disc dichotomy in the Milky Way Deconstructing Galaxies…

Classical vs Pseudo Bulges CLASSICAL BULGES: Mergers produce elliptical galaxies. In the early universe, disks formed around dwarf ellipticals. Predict: old stars, low rotation, short SF timescales, ellipsoidal morphology, de Vaucouleurs type profiles (Sersic index ~ 4) PSEUDO BULGES: Gas funnelled to the centre by disk processes, forming new stars and central mass concentration Predict: younger stars, high rotation, long SF timescales, disky or boxy morphology, exponential type profile (Sersic index ~ 1)

Drory & Fisher 2007; Fisher & Drory 2008, 2010

Schawinski Schawinski The Evolving View of AGN Hosts A sample of 140 X-ray selected AGN showed distortions (“mergers”) were no more likely to be ongoing than in a control sample Cisternas+ 2011

Semi-analytic models suggest that AGN in discs dominate the AGN luminosity for low mass Hopkins+ 13

The growth of a disk compresses a pre-existing (classical) bulge raising its velocity dispersion No disc 5x M b 10x M b 15x M b 20x M b Zero mass disc (for scale) 20x M b

Fitting function following Wolf et al. 2010: The parameters ( ϒ,δ) account for the finite-thickness and assumption of fixed effective radius

Data: Gadotti & Kauffmann 2009 Ellipticals Bulges R eff σ8σ8 EllipticalsBulges σ8σ8 Mass

Data: Gadotti & Kauffmann 2009 Bulges Bulges uncompressed Ellipticals

Exponential Disks? Boeker Dutton 2009

D/B and Rd/Re correlate weakly with σ e. Neglecting this correlation, the M  - σ e relation of SMBHs which start out on the relation but fail to grow with this disc is given by: log M  = α – β log + β log σ e σ8σ8 R d /R eff D/B

Gültekin Doubling σ requires that M  grow by a factor of 16 Gadotti 09

Ellipticals No offset between bulges now and ellipticals Bulges Expected offset if SMBHs do not grow while discs reform is δα = -0.2 dex Gültekin sample δα = 0.08

Ellipticals Bulges Predicted initial dispersions Expected offset if SMBHs do not grow while discs reform is δα = dex Beifiori sample Also no offset between bulges now and ellipticals δα = 0.11

Barred Galaxies But Beifiori et al find no offset between barred and unbarred galaxies Graham 08 Graham+ 11

Bar driven angular momentum redistribution increases the disc mass at the centre, raising σ e and causing an offset for the SMBH Hartmann+ 14 All B+D simulations are models of the MW from Widrow+ 08

Classical bulges δα = ± 0.20 Hartmann+ 14 Pseudo bulges δα = ± 0.09 Sample of McConnell & Ma other galaxies with no reliable bulge classification

Sellwood & Binney 2002 But negligible heating associated with the migration FullNear circular ∆L L Radius RR  J R = (  p -  )  L/   E =  p  L

R form Roškar+ 08 Schoenrich & Binney 09ab Gilmore & Reid 1983

Ro š kar+13 Predictions from Schönrich & Binney 12 Plotted for stars 5-6 Gyr old Solway Thick disk Thin disk Accretion: Abadi+03; thickening: Quinn+93; gas rich mergers: Brook+05; direct gas formation: Stinson+13; Bird+13; clump heating: Bournaud+07; resonant capture: Sridhar+96

Migration can give rise to a thick disc with density, kinematic, metallicity and abundance patterns not inconsistent with the observed Loebman+ 11 Roškar+ 13 Ruchti+ 11

Decreasing metallicity and v rot with height SDSS at Thin-Thick Transition z [pc] |z| [kpc] V Y [km/s] Photometric [Fe/H] [Fe/H] Data from SDSS Ivezic+ 08; Bond+ 10

V y [km/s] [Fe/H] Age [Gyr] z [kpc] Age, velocity and metallicity all correlate with height above the mid-plane. But there is little correlation between velocity and metallicity, as found by SDSS

Stars are born on circular orbits and hence have no correlation between V and [Fe/H]. Heating brings stars into the local volume creating a correlation. Migration shuffles [Fe/H] and erases the correlation Solar nbhd Loebman+ 11 [Fe/H] R [kpc]

all youngold Geneva-Copenhagen Survey in mid- plane after selecting non- binary stars (Qualitatively similar results with Casagrande+ 11 ages) ΔV/Δ[Fe/H] = -0.5 ± 1.5 ΔV/Δ[Fe/H] = -1.9 ± 1.6 ΔV/Δ[Fe/H] = 22.1 ± 0.8 Loebman+ 11

Bovy+ 2012abc Liu & van de Ven 2012 Sales Dierickx+ 10, Wilson+ 11

 Discs growing around pre-existing bulges compress them and raise their velocity dispersion. This implies SMBHs in classical bulges must grow on average by 50-80% to remain on the M BH - σ e relation. A comparison between the M BH - σ e relations of elliptical galaxies and classical bulges finds no offset. Bar evolution also compresses the bulge, and there is evidence that barred galaxies are offset from the M BH - σ e relation.  The thick disc in the MW may have been substantially contaminated by migrated thin disc stars. A thin/thick disc dichotomy can easily arise as a result of migration. Some evidence for an unmigrated population can be recovered from the distribution of orbital eccentricities. Conclusions