Evolution of Early-Type Galaxies in Groups Robert Feldmann Fermilab - PowerPoint PPT Presentation

Evolution of Early-Type Galaxies in Groups Robert Feldmann Fermilab collaborators L. Mayer, M. Carollo, T. Kaufmann

Question When, how, and it what order morphological photometric & (structural) (color, SFR) transformations of present day early-type galaxies? • Role of mergers in these transformations? • Impact of environment and environmental processes? • What happens with the dense galaxies seen at high z? • Differences between central and satellite galaxies?

A few clues (or more questions...) Observations: • morphology - density relation • evolution of luminosity/mass functions of red/blue, early/late type galaxies • quenching separable into stellar mass driven & environmentally driven (Peng+10) • 2/3 local early types in the field have substantial gas reservoirs (e.g., Osterloo+11) - environment? • 3/4 local early types are fast rotating, somewhat disky objects (e.g., Emsellem+07) - dissipative mergers? • compact passive early types at high z, rare locally ... Theory: • high resolution numerical simulations of individual processes (binary mergers, ram-pressure stripping, tidal stripping, tidal stirring, harassment, ...) • analytical & semi-analytical models for population studies • challenge: predicting evolution of populations in ab-initio simulations

Why Groups? central satellite Rvir

Why Groups? central satellite • Typical environments: • Many galaxies in the Universe live in groups, • many groups exist (compared to clusters) • significant fraction of local baryons is in groups • Groups contain usually both spirals and early type galaxies • Are believed to be places where galaxies preferentially merge • High density environment; environmental effects: ram- pressure stripping, starvation, tidal stripping • Allow to simultaneously study very massive centrals and lower mass (but still massive) satellite galaxies Rvir

Simulation details Zoom-in simulations of 3 groups of M Vir ~ 10 13 M � in a 123 Mpc box TreeSPH GASOLINE Star formation: n>0.1 cm -3 , T < 15‘000 K, ρ gas ε ρ star = c ∗ ˙ convergent flow, ε =0.05, t dyn SN feedback: “Star” = Single Stellar Population, 4 ! 10 43 J of thermal energy/SN; SN Ia & II UV background, tracking of metal production, mass loss by stellar winds High resolution : • resolve 13 satellites with ~10 5 baryonic particles: ( ~ 1 Million CPUh) • ~200 pc/h spatial resolution, SPH particle masses ~10 6 M ⊙ /h Low resolution : • resolve central galaxies with ~10 5 baryonic particles • ~0.5 kpc/h spatial resolution, baryonic particle masses of ~8 ! 10 6 M ⊙ /h Similar physics & resolution previously used to study individual dwarf and MW galaxies

Evolution Disk cold (green), hot (red) B, R, I band (stellar light) gas surface density

Central Galaxies Feldmann et al. APJ, 709, 218 (2010)

Simulated Group Centrals at z=0 z=0 + • Massive galaxies (~few times 10 11 M � ) • Surface profile close to de Vaucouleurs (n~4) • Supported by velocity dispersion (v rot / σ cen <1) G1 • little star formation outside central region • almost no cold gas (f gas <1%) • red colors (g-r ~ 0.85) No need for AGN feedback G2 (outside central ~few 100 pc) - • biased towards higher masses & smaller sizes w.r.t. average observed mass-size relation G3

their ~2 progenitors 4 3.5 z>1.4 actively starforming z>1.4 passive 3 2.5 z<1.4 (z-K s ) AB • BzK criterion: star forming 2 galaxies A V =1.3 1.5 z=3 • SFR ~ 20-60 M � /yr z=0.5 1 A V =0.8 • stellar masses ~0.5-1x10 11 M � A V =0.3 0.5 • compact: Reff ~ 1 kpc A V =0 stars 0 − 0.5 0 1 2 3 4 5 (B-z) AB

Density evolution How do these dense high-z galaxies evolve into local not-so-dense galaxies ? z z 1.5 1 0.75 0.5 0.25 0.1 2 10 ! eff [ 10 10 M sun kpc − 3 ] 1 10 0 10 1-2 orders of mag. change − 1 10 ! c [ 10 10 M sun kpc − 3 ] 1 10 0 10 almost constant − 1 10 4 6 8 10 12 time [ Gyr ]

Density evolution How do these dense high-z galaxies evolve into local not-so-dense galaxies ? z z 1.5 1 0.75 0.5 0.25 0.1 2 11 10 10 R eff z ! eff [ 10 10 M sun kpc − 3 ] 0 2.7 ! 0.08 0.3 2.9 ! 0.1 1 10 0.5 1.9 ! 0.1 0.91 2.1 ! 0.1 10 10 z=0 1.1 1.8 ! 0.2 1.3 2.1 ! 0.2 1.5 2.4 ! 0.2 0 10 2 4 ! 0.3 � [ M sun kpc � 2 ] 1-2 orders of mag. change 9 10 − 1 10 ! c [ 10 10 M sun kpc − 3 ] 8 1 10 10 z=2 0 10 7 10 almost constant − 1 0.5 1 2 4 6 8 10 12 10 4 6 8 10 12 r [ kpc ] time [ Gyr ] envelope due to merging (not only “minor”) cf., e.g., Naab+07,+09, Bezanson+09, many more

Stellar mass accretion history 1 mergers (minor & major!) 0.8 in situ star formation <mass fraction> 0.6 0.4 0.2 accretion of stripped stars, stars formed before z=4, ... 0 0 0.5 1 1.5 2 2.5 z at z>1: mass growth by in-situ SF at z<1: mass growth by mergers

Satellites (or in short “non-central group members within Rvir”) Feldmann et al. APJ,, 736, 88 (2011)

Hubble sequence in groups? Color + Broad range in 1 2 3 4 • n_sersic 5 • color • SFR 6 7 8 9 n Sersic • gas fractions G2 • rotational support 10 11 12 13 v/ ! - Galaxies G3 somewhat too compact SFR, f(HI) k s , e l l i p t i c a l s r f o r m i n g d i s k s , p a s s i v e d i s 3 C l a s s e s : s t a

Properties at z~2? at z~2 all progenitors are: • star forming • blue • gas-rich • disky • rotation-supported • some not even born yet none of the progenitors is yet in the group (typical infall time z~0.3-1) How and why do morphology & color change with time?

Morphological transformations z 2 1.5 1 0.75 0.5 0.25 0.1 z=0 ell. 10.8 stellar mass [ dex ] 10.6 log 10 ( M star [ M sun ] ) 10.4 10.2 10 z=0 disks 9.8 9.6 4 6 8 10 12 time [ Gyr ] time [ Gyr ]

Morphological transformations z 2 1.5 1 0.75 0.5 0.25 0.1 z=0 ell. 10.8 stellar mass [ dex ] 10.6 log 10 ( M star [ M sun ] ) 10.4 10.2 10 z=0 disks 9.8 9.6 4 6 8 10 12 time [ Gyr ] time [ Gyr ] Due to merging, often before infall to the group

Morphological transformations z 2 1.5 1 0.75 0.5 0.25 0.1 z=0 ell. 10.8 stellar mass [ dex ] 10.6 log 10 ( M star [ M sun ] ) 10.4 Groups are not the places where 10.2 galaxies merge... 10 z=0 disks 9.8 9.6 4 6 8 10 12 time [ Gyr ] time [ Gyr ] Due to merging, often before infall to the group

Color transformations Overall decline in SFR 1.4 z=0 + 1.2 Environmental effects 1 0.8 B � I z=1 • Shutdown of Accretion, 0.6 • Starvation, 0.4 • Ram-pressure (minor) 0.2 z=2 0 � 0.2 9.8 10 10.2 10.4 10.6 10.8 11 Passive Disks log 10 ( M star [ M sun ] ) Star forming Disks • Earlier Infall • Longer Exposed to Group • Not yet exhausted cold gas reservoir • Declining star formation Environment • Smaller Pericenters • Large Pericenter: lower ram-pressure • Preprocessing before group infall (or tidal) stripping

The picture outside group within group z=1.1 z=0.4 z=1.0 z=0.9 • gas-rich disks merge red elliptical: • form “gas-rich” elliptical • enter high-dens environ • over ~Gyr timescale become red & dead • same, but without the merger red disk:

Density transformations What happens to dense satellites? z=2 centrals z=2 satellites z=0 satellites Kaufmann+, in prep

Density transformations What happens to dense satellites? z=2 centrals z=2 satellites z=0 satellites • dense satellites disappear (merge with central), • later infalling satellites are born later • are less dense Kaufmann+, in prep

Conclusions High mass (> 10 11 M � ) centrals: • red, low SF, early type galaxies • mass growth by star formation (at z>1) & merging (z<1) • size growth of envelope (merging, SF, migration) around dense core Lower mass (~ few 10 10 M � ) satellites: • span of Hubble types incl. blue disks, red disks & ellipticals • morphological transformation induced by merging before group infall & before photometric transformations • environmental effects (primarily starvation) lead to SF quenching, gas removal and red colors • field ellipticals predicted to retain their gas • dense satellites disappear (merge with central)