Galaxy size and angular momentum in the Illustris simulation

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1 Galaxy size and angular momentum in the Illustris simulation Shy Genel Hubble Fellow Columbia University Collaborators: Fall, Hernquist, Nelson, Rodriguez-Gomez, Sijacki, Snyder, Springel, Torrey, Vogelsberger

2 The theore(cal challenge: understanding the origin of observed galaxy types

3 Galaxy angular momentum Observed correlation between stellar specific angular momentum and galaxy stellar mass Fall & Romanowsky 2013 Parallel relations for disks and ellipticals, indicating a factor ~5 difference in angular momentum The slope is similar to that expected for ΛCDM halos

4 The angular momentum problem Hydrodynamical cosmological simulations are struggling to produce large rotating galaxies Navarro et al Torrey et al. 2012

5 Recent successful zoomed-in disks Aumer et al Agertz et al Guedes et al Eris Stinson et al MaGICC Marinacci et al. 2013

6 The Illustris Simulation Vogelsberger et al Genel et al Sijacki et al Nelson et al A (106.5 Mpc) 3 box run to z=0 ( 10 3 M M sun z=0) Baryonic resolution: M sun Resolution elements: Public data release: Gravitational spatial resolution: 1 ckpc Gravity+hydro with Arepo (TreePM + Voronoi moving mesh; Springel et al. 2010) Galaxy formation physics (cooling, star-formation, stellar evolution, galactic winds, BH growth, AGN feedback) Tuned to (approx.!) match the cosmic SFRD and z=0 M * -M h relation

7 Genel et al z 5 z=5 z=4 M* Msun M* Msun M* Msun z=0 Spheroids emerging towards higher mass and/ or lower z Stars M* Msun M* Msun M* Msun z=3 z=2 z=1 Gas Gas depleted/ ejected towards higher mass at lower z

8 Genel et al z 5 z=5 z=4 M* 109.0Msun z=3 z=2 z=1 z=0 HUDF mock observations show: M* 109.5Msun M* Msun Clumpy galaxies M* Msun Redder centers M* Msun Disks & spheroids M* Msun

9 Galaxy bimodality Vogelsberger et al Galaxies in Msun halos at z=0

10 Morphological classification Snyder et al Non-parametric morphological classification for the low redshift galaxy population compares favorably with observations

11 Morphological classification Credit: P. Torrey K. Willett G. Snyder Galaxy Zoo visual classifications on-going spiral 2 spiral arms no bulge edge-on disk, rounded bulge smooth, round smooth, cigar-shaped bar merger

12 Galaxy angular momentum Genel et al /3 2/3 2/ /3 1/3 1/3 (j [kpc*km/s Specific angular momentum of the stars correlates with galaxy mass Separate relations for late-types and early-types, each with a slope close to (2/3) 2 all flat round Overall relation is shallower, (at least in part) due to changing mix between late- and early-types with mass observations all diffuse concentrated all star-forming quiescent blue red

13 Galaxy angular momentum Genel et al /3 2/3 2/ /3 1/3 1/3 (j [kpc*km/s all flat round Specific angular momentum of the stars correlates with galaxy mass Separate relations for late-types and early-types, each with a slope close to (2/3) observations all diffuse concentrated Overall relation is shallower, (at least in part) due to changing mix between late- and early-types with mass all star-forming quiescent blue red Compare: Teklu et al Magneticum simulations

14 Galaxy angular momentum Snyder et al Non-trivial correlations between angular momentum, SFR, and concentration: Passive galaxies are bulge-dominated, and greatly vary in angular momentum Trends for star-forming galaxies can be qualitatively understood in terms of inside-out growth

15 Galaxy angular momentum Genel et al λ = λ = λ = (j [kpc*km/s (M 200c all flat round all diffuse concentrated (M 200c all star-forming quiescent blue red (M 200c Placing M halo instead of M * on the x-axis allows comparison with simple theory: Late-types are consistent with having % of the specific angular momentum as the dark matter halo Early-types retain ~15-50%

16 Galaxy angular momentum λ=0.034 (j * [kpc*km/s (M 200c Scaling with redshift approximately matches the scaling for DM halos: (1+z) -1/2, i.e. angular momentum retention is approximately redshift-independent

17 The role of feedback Genel et al Enhancement/addition of feedback always makes galaxies larger But while galactic winds boost the angular momentum, radiomode AGN feedback reduces it 4 no feedback angular momentum (j[kpc*km/s metals and mass return galactic winds AGN but no radio mode full model size (R 1/2,3D [kpc no feedback metals and mass return galactic winds AGN but no radio mode full model

18 The role of feedback Genel et al Galactic winds remove early-accreting low-j gas, generating fountain Galactic winds do not disrupt the rotation support of the disk The result: larger sizes with larger angular momentum 4 no feedback angular momentum (j[kpc*km/s metals and mass return galactic winds AGN but no radio mode full model size (R 1/2,3D [kpc no feedback metals and mass return galactic winds AGN but no radio mode full model

19 The role of feedback Genel et al AGN feedback makes galaxies, and mergers, dry, forcing sizes up AGN feedback prevents late-accreting high-j gas, reducing angular momentum The result: dispersion-dominated galaxies (see also Dubois+2013 / Devriendt talk) 4 no feedback angular momentum (j[kpc*km/s metals and mass return galactic winds AGN but no radio mode full model size (R 1/2,3D [kpc no feedback metals and mass return galactic winds AGN but no radio mode full model

20 Conclusion and outlook Does the type of dominant feedback determine the galaxy morphology? SF-driven galactic winds make large star-forming rotating disks AGN feedback makes large passive dispersion-dominated spheroids What determines the angular momentum retention factors why approximately unity? Is it really conservation, or something more complicated?

21 Additional slides

22 Galaxy angular momentum Genel et al Almost all galaxies have high specific angular momentum (j) at high early type galaxies with high angular momentum early type galaxies with low angular momentum 0 redshift 2.5 Early-type galaxies at z=0 with low angular momentum may: (j [kpc*km/s early type galaxies with low angular momentum, growth then drop early type galaxies with low angular momentum, arrested growth z rapidly lose their j 3 or stop gaining j

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