Formation of high-redshift disks and pseudo-bulges in nearby - PowerPoint PPT Presentation

Formation of high-redshift disks and pseudo-bulges in nearby galaxies Takashi Okamoto (Kobe-branch, CCS,Tsukuba Univ.） T. Okamoto 2012 MNRAS 428, 718 13 年 1 月 28 日月曜日

show disky morphology. will they be at z = 0? the galactic bulge. Stark+’08 High-redshift disks • Galaxies at z ~ 3 often • What are they and what • The size is comparable to 13 年 1 月 28 日月曜日

a disc? • formed via secular evolution of • non-negligible rotation • boxy/peanut, disky (n < 2) formed by a major merger? Athanassoula 05 • mainly supported by velocity dispersion • ellipsoid (Sérsic index n > 2) • Bulges • Two classes of bulges • Classical bulge • Pseudo-bulge 13 年 1 月 28 日月曜日

Bulge formation (standard pictures) classical bulge pseudo-bulge disk instabilities (bar, clump, etc.) merger bulge formation bulge formation newly accreted gas forms a new disk 13 年 1 月 28 日月曜日

CDM？ pseudo-bulges (Weinzirl+09, Kormendy+10) Bulges of nearby large disk galaxies • More than half of nearby large disks have • Is this fact consistent with the CDM model? • How do the pseudo-bulges form under 13 年 1 月 28 日月曜日

formation 100 h -1 Mpc comoving box (Aq-C, Aq-D) This study • Cosmological hydrodynamic simulations of galaxy • Two Milky Way-sized halos (Aquarius halos) in • What type of bulge forms? • How they form? 13 年 1 月 28 日月曜日

below redshift 4 around redshift 2 redshift 1 disc changes with redshift Aq-C face-on edge-on • no significant mergers gas • disc formation begins • there is a bar below stars • The orientation of the 13 年 1 月 28 日月曜日

below redshift 4 around redshift 2 redshift 1 disc changes with redshift Aq-C face-on edge-on • no significant mergers gas • disc formation begins • there is a bar below stars • The orientation of the 13 年 1 月 28 日月曜日

below redshift 4 around redshift 2 structure below redshift 1 Aq-D face-on edge-on • no significant mergers gas • disc formation begins • can’t see bar-like stars • clumpy star formation 13 年 1 月 28 日月曜日

below redshift 4 around redshift 2 structure below redshift 1 Aq-D face-on edge-on • no significant mergers gas • disc formation begins • can’t see bar-like stars • clumpy star formation 13 年 1 月 28 日月曜日

r < 3 kpc でバルジ成分が卓越 Surface density profiles • Fit the bulge by the Sérsic profile: pseudobulge-like • Aq-C: n = 1.2 • Aq-D: n = 1.4 13 年 1 月 28 日月曜日

contour shapes in edge- Both bulges are pseudo-bulges on boxy-bulge in Aq-C D’s bulge is a strong evidence of disky bulges Bulge shapes • A bar in Aq-C • Both bulges have disky face-on • Weak signature of edge-on • Diamond shape of Aq- 13 年 1 月 28 日月曜日

rotation in Aq-C’s bulge supported by rotation velocity dispersion but the non-circular orbit is confined in a thin oblate (small σ z ) . Kinematic properties • A signature of cylindrical • Aq-D’s bulge is mainly • Aq-C’s bulge has large 13 年 1 月 28 日月曜日

z = 0. Evolution of surface density profiles • By z = 2ー3, the bulges have formed as disks with small scale length. • From z ~ 2, the main disks with large scale length form around the disky bulges. • The bulge masses at z = 2 account for 70% (Aq-C) and 87%(Aq-D) of those at The main process of the pseudo-bulge formation is NOT the secular evolution in these simulations 13 年 1 月 28 日月曜日

• At each redshift, distributions of stars and gas within 0.1 R vir are shown in face-on and edge-on. • The progenitors are always disk-like. Evolution of the galaxies 13 年 1 月 28 日月曜日

stars with in 3 kpc at z = 0 formed by high- redshift starbursts Star formation histories of the bulges • Formation histories of • Bulge stars are mainly • Mostly in ¡situ . 13 年 1 月 28 日月曜日

are quite ‘wet’ merging mass ratio between mergers and star formation activities ( M * + M gas ) at z < 4. galaxy mass M gas SFR Merging histories of the galaxies • No clear correlation • Quiet merging histories • High-z major mergers Mergers are irrelevant to pseudo-bulge formation 13 年 1 月 28 日月曜日

star formation rate is highest. a gas disks. as high-redshift disks. Gas distribution during starbursts • Gas distribution when • Starbursts occur in • Pseudo-bulges form 13 年 1 月 28 日月曜日

redshift disks. observed high- is significantly lower than the LoS velocity probably because feedback implementation. Velocity maps of the star-forming gas at z = 3 Aq-C Aq-D LoS mean velocity • Similar to the • Velocity dispersion LoS velocity disp. 13 年 1 月 28 日月曜日

bulges bulges in late-type disks pseudo-bulges bulges Formation time-scale of the bulges Fisher+ ’ 09 • blue filled circles: pseudo- specific SFR of the bulges • cyan filled circles: pseudo- • blue open circles: inactive • red open squares: classical • Simulated bulges are bulge mass Aq-C inactive pseudo-bulges Aq-D 13 年 1 月 28 日月曜日

triggered by rapid supply of gas. • C) and 13 % (Aq-D) of bulge mass pseudobulge, it does Although secular evolution only accounts for 30 % (Aq- • high-redshift disks The progenitors of pseudo-bulges would be observed as • These pseudo-bulges form by high-redshift starbursts pseudo-bulges. • disk formation ⇒ secular evolution of disk is unimportant The formation of pseudo-bulges has completed before • sized galaxies (inactive) pseudo-bulges naturally form in Milky Way- affect the spacial and kinematic properties of the Summary 13 年 1 月 28 日月曜日

v/σ • 半径の関数として v rot /σ を plot • Aq-C は low-z ほど中心部で v rot /σが減少 • たぶん bar の影響 • Aq-D は逆に z = 1 からほとんど進化なし 13 年 1 月 28 日月曜日