2,005 research outputs found
Cosmological pseudobulge formation
Bulges can be classified into classical and pseudobulges; the former are
considered to be end products of galactic mergers and the latter to form via
secular evolution of galactic disks. Observationally, bulges of disk galaxies
are mostly pseudobulges, including the Milky Way's. We here show, by using
self-consistent cosmological simulations of galaxy formation, that the
formation of pseudobulges of Milky Way-sized disk galaxies has mostly completed
before disk formation; thus the main channel of pseudobulge formation is not
secular evolution of disks. Our pseudobulges form by rapid gas supply at
high-redshift and their progenitors would be observed as high-redshift disks.Comment: 3 pages, 2 figures, to appear in the proceedings of `First Stars IV -
from Hayashi to the future', M. Umemura, K. Omukai (eds.
The roles of ram-pressure stripping and minor mergers in evolution of galaxies
We investigate environmental effects on evolution of bright cluster galaxies
in a Lambda-dominated cold dark matter universe using a combination of
dissipationless N-body simulations and a semi-analytic galaxy formation model.
We incorporate effects of ram-pressure stripping (RPS) and minor merger-induced
small starburst (minor burst) into our model. By considering minor burst,
observed morphology-radius relation is successfully reproduced. When we do not
consider minor burst, the RPS hardly increases the intermediate B/T population.
In addition, the RPS and minor burst are not important for colours or star
formation rates of galaxies in the cluster core if star formation time-scale is
properly chosen, because the star formation is sufficiently suppressed by
consumption of the cold gas. We also find that SF in bulge-dominated galaxies
is mainly terminated by starburst induced by major mergers in all environments.Comment: To appear in the proceedings of IAU colloq. No. 195, "Outskirts of
Galaxy Clusters: intense life in the suburbs", Torino, 12-16 March 2004, 5
pages, 2 figures, uses IAU macr
Sub-millimetre galaxies in cosmological hydrodynamic simulations: Source number counts and the spatial clustering
We use large cosmological Smoothed-Particle-Hydrodynamics simulations to
study the formation and evolution of sub-millimetre galaxies (SMGs). In our
previous work, we studied the statistical properties of ultra-violet selected
star-forming galaxies at high redshifts. We populate the same cosmological
simulations with SMGs by calculating the reprocess of stellar light by dust
grains into far-infrared to millimetre wavebands in a self-consistent manner.
We generate light-cone outputs to compare directly the statistical properties
of the simulated SMGs with available observations. Our model reproduces the
submm source number counts and the clustering amplitude. We show that bright
SMGs with flux mJy reside in halos with mass of and have stellar masses greater than .
The angular cross-correlation between the SMGs and Lyman- emitters is
significantly weaker than that between the SMGs and Lyman-break galaxies. The
cross-correlation is also weaker than the auto-correlation of the SMGs. The
redshift distribution of the SMGs shows a broad peak at , where
Bright SMGs contribute significantly to the global cosmic star formation rate
density. Our model predicts that there are hundreds of SMGs with mJy
at per 1 square degree field. Such SMGs can be detected by ALMA.Comment: 11 pages, 13 figures, submitted to MNRA
Cosmic evolution of bars in simulations of galaxy formation
We investigate the evolution of two bars formed in fully self-consistent
hydrodynamic simulations of the formation of Milky Way-mass galaxies. One
galaxy shows higher central mass concentration and has a longer and stronger
bar than the other at . The stronger bar evolves by transferring its
angular momentum mainly to the dark halo. Consequently the rotation speed of
the bar decreases with time, while the amplitude of the bar increases with
time. These features qualitatively agree with the results obtained by idealized
simulations. The pattern speed of the stronger bar largely goes up and down
within a half revolution in its early evolutionary stage. These oscillations
occur when the bar is misaligned with the mode Fourier component. These
oscillations correlate with the oscillations in the triaxilality of the dark
matter halo, but differently from the way identified by idealized simulations.
The amplitude of the weaker bar does not increase despite the fact that its
rotation slows down with time.This result contradicts what is expected from
idealized simulations and is caused by the decline of the central density
associated with the mass loss and feedback from the stellar populations. The
amplitude of the weaker bar is further weakens by the angular momentum
injection by the interactions with stellar clumps in the disk. In the both
galaxies, the bars are terminated around the 4:1 resonance.Comment: 17 pages, 18 figures, accepted for publication in PAS
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