TY - JOUR
T1 - Galaxy Disks
AU - van der Kruit, P. C.
AU - Freeman, K. C.
PY - 2011/9
Y1 - 2011/9
N2 - The disks of disk galaxies contain a substantial fraction of their
baryonic matter and angular momentum, and much of the evolutionary
activity in these galaxies, such as the formation of stars, spiral arms,
bars and rings, and the various forms of secular evolution, takes place
in their disks. The formation and evolution of galactic disks are
therefore particularly important for understanding how galaxies form and
evolve and the cause of the variety in which they appear to us. Ongoing
large surveys, made possible by new instrumentation at wavelengths from
the UV (Galaxy Evolution Explorer), via optical (Hubble Space Telescope
and large groundbased telescopes) and IR (Spitzer Space Telescope), to
the radio are providing much new information about disk galaxies over a
wide range of redshift. Although progress has been made, the dynamics
and structure of stellar disks, including their truncations, are still
not well understood. We do now have plausible estimates of disk
mass-to-light ratios, and estimates of Toomre's Q parameter show that
they are just locally stable. Disks are mostly very flat and sometimes
very thin, and they have a range in surface brightness from canonical
disks with a central surface brightness of about 21.5 B-mag
arcsec-2 down to very low surface brightnesses. It
appears that galaxy disks are not maximal, except possibly in the
largest systems. Their Hi layers display warps whenever Hi can be
detected beyond the stellar disk, with low-level star formation going on
out to large radii. Stellar disks display abundance gradients that
flatten at larger radii and sometimes even reverse. The existence of a
well-defined baryonic (stellar + Hi) Tully-Fisher relation hints at an
approximately uniform baryonic to dark matter ratio. Thick disks are
common in disk galaxies, and their existence appears unrelated to the
presence of a bulge component; they are old, but their formation is not
yet understood. Disk formation was already advanced at redshifts of
˜2, but at that epoch disks were not yet quiescent and in full
rotational equilibrium. Downsizing (the gradual reduction with time in
the mass of the most actively star-forming galaxies) is now
well-established. The formation and history of star formation in S0s are
still not fully understood.
AB - The disks of disk galaxies contain a substantial fraction of their
baryonic matter and angular momentum, and much of the evolutionary
activity in these galaxies, such as the formation of stars, spiral arms,
bars and rings, and the various forms of secular evolution, takes place
in their disks. The formation and evolution of galactic disks are
therefore particularly important for understanding how galaxies form and
evolve and the cause of the variety in which they appear to us. Ongoing
large surveys, made possible by new instrumentation at wavelengths from
the UV (Galaxy Evolution Explorer), via optical (Hubble Space Telescope
and large groundbased telescopes) and IR (Spitzer Space Telescope), to
the radio are providing much new information about disk galaxies over a
wide range of redshift. Although progress has been made, the dynamics
and structure of stellar disks, including their truncations, are still
not well understood. We do now have plausible estimates of disk
mass-to-light ratios, and estimates of Toomre's Q parameter show that
they are just locally stable. Disks are mostly very flat and sometimes
very thin, and they have a range in surface brightness from canonical
disks with a central surface brightness of about 21.5 B-mag
arcsec-2 down to very low surface brightnesses. It
appears that galaxy disks are not maximal, except possibly in the
largest systems. Their Hi layers display warps whenever Hi can be
detected beyond the stellar disk, with low-level star formation going on
out to large radii. Stellar disks display abundance gradients that
flatten at larger radii and sometimes even reverse. The existence of a
well-defined baryonic (stellar + Hi) Tully-Fisher relation hints at an
approximately uniform baryonic to dark matter ratio. Thick disks are
common in disk galaxies, and their existence appears unrelated to the
presence of a bulge component; they are old, but their formation is not
yet understood. Disk formation was already advanced at redshifts of
˜2, but at that epoch disks were not yet quiescent and in full
rotational equilibrium. Downsizing (the gradual reduction with time in
the mass of the most actively star-forming galaxies) is now
well-established. The formation and history of star formation in S0s are
still not fully understood.
KW - disks in galaxies: abundance gradients
KW - chemical evolution
KW - disk stability
KW - formation
KW - luminosity distributions
KW - mass distributions
KW - SO galaxies
KW - scaling
KW - laws
KW - thick disks
KW - surveys
KW - warps and truncations
KW - ON SPIRAL GALAXIES
KW - STAR-FORMATION HISTORY
KW - TULLY-FISHER RELATION
KW - COLD DARK-MATTER
KW - BAND SURFACE PHOTOMETRY
KW - WESTERBORK HI SURVEY
KW - DIGITAL SKY SURVEY
KW - INITIAL MASS FUNCTION
KW - SUPERMASSIVE BLACK-HOLES
KW - HIGH-VELOCITY CLOUDS
UR - http://adsabs.harvard.edu/abs/2011ARA%26A..49..301V
U2 - 10.1146/annurev-astro-083109-153241
DO - 10.1146/annurev-astro-083109-153241
M3 - Article
SN - 0066-4146
VL - 49
SP - 301
EP - 371
JO - Annual Review of Astronomy and Astrophysics
JF - Annual Review of Astronomy and Astrophysics
ER -