594 research outputs found
In situ study of magmatic processes: a new experimental approach
We present an internally heated autoclave, modified in order to allow in situ studies at pressure up to 0.5 GPa and temperature up to 1000°C. It is equipped with transparent sapphire windows, allowing the observation of the whole experiment along the horizontal axis. In the experimental cell the sample is held between two thick transparent plates of sapphire or diamond, placed in the furnace cylinder. The experimental volume is about 0.01 cm3. Video records are made during the whole experiment. This tool is developed mainly to study magmatic processes, as the working pressures and temperatures are appropriate for subvolcanic magma reservoirs. However other applications are possible such as the study of subsolidus phase equilibria as we have used well known phase transitions, such as the system of AgI, to calibrate the apparatus with respect to pressure and temperature. The principle of the apparatus is detailed. Applications are presented such as studies of melt inclusions at pressure and temperature and an in situ study of magma degassing through the investigation of nucleation and growth processes of gas bubbles in a silicate melt during decompression
De reformatione status monastici.
Copia digital. Madrid : Ministerio de Cultura. Subdirección General de Coordinación Bibliotecaria, 2006sign.: a\p8\s.= 4º.L. gót. de 2 tam. (200G 76G), 38 lín.Min. p. inicialesGrab (1)Esc. tipográfico.Hoj. 1r., sign. [a]: Tractatus nouus super // reformatione status mo // nastici. // Esc. tipogr. // Hoj. 1v. Grabado.- Hoj. 2r. sign. a2: Colendissimo magistro // nostro magistro michaeli bureau sacrarum litteraru interpreti // doctissimo Iulianus quimonus... Hoj. 2v., lín. 19: Sacrarum Irarum doctori doctissimo mgro Iuliano // quimon michael bureau theologo2 mimus. S.D. // ... Hoj. 3r., sign. a3, lín.10: Codex instructionis in reformationem ordinis monasti // ci a fratre michaelebureau doctore theologo editus // Prima animaduersio Ex // pedit hac tempestate ad reformandos monastice discipline mo // res collapsos... Hoj. 8r., lín. 29 ...fructum afferat in tepore suo eo donate // qui viuit et regnat deus per infinita seculoru secula Amen. // Et sic est finis. Laus deo // Hoj. 8v., en bl
The stellar kinematics and populations of boxy bulges: cylindrical rotation and vertical gradients
Boxy and peanut-shaped bulges are seen in about half of edge-on disc
galaxies. Comparisons of the photometry and major-axis gas and stellar
kinematics of these bulges to simulations of bar formation and evolution
indicate that they are bars viewed in projection. If the properties of boxy
bulges can be entirely explained by assuming they are bars, then this may imply
that their hosts are pure disc galaxies with no classical bulge. A handful of
these bulges, including that of the Milky Way, have been observed to rotate
cylindrically, i.e. with a mean stellar velocity independent of height above
the disc. In order to assess whether such behaviour is ubiquitous in boxy
bulges, and whether a pure disc interpretation is consistent with their stellar
populations, we have analysed the stellar kinematics and populations of the
boxy or peanut-shaped bulges in a sample of five edge-on galaxies. We placed
slits along the major axis of each galaxy and at three offset but parallel
positions to build up spatial coverage. The boxy bulge of NGC3390 rotates
perfectly cylindrically within the spatial extent and uncertainties of the
data. This is consistent with the metallicity and alpha-element enhancement of
the bulge, which are the same as in the disk. This galaxy is thus a pure disc
galaxy. The boxy bulge of ESO311-G012 also rotates very close to cylindrically.
The boxy bulge of NGC1381 is neither clearly cylindrically nor
non-cylindrically rotating, but it has a negative vertical metallicity gradient
and is alpha-enhanced with respect to its disc, suggesting a composite bulge
comprised of a classical bulge and bar (and possibly a discy pseudobulge)
[abridged] Even this relatively small sample is sufficient to demonstrate that
boxy bulges display a range of rotational and population properties, indicating
that they do not form a homogeneous class of object.Comment: MNRAS accepted. 10 page
Formation of young boxy/peanut bulges in ringed barred galaxies
We investigate whether the formation mechanism of boxy and peanut-shaped
(B/PS) bulges could depend on the gas content of the galaxy. We have performed
N-body simulations with and without a gaseous component. In the second case
star formation/feedback recipes have also been implemented to create new
stellar populations. As in many previous studies, in our N-body collisionless
simulation, the B/PS is due to the classical break in the z mirror symmetry
lasting roughly 200 Myr. When a gaseous component and star formation recipes
are added to the simulation, the bulge-growing mechanism is quite different.
The young stellar population that is born in the thin gaseous disc rapidly
populates vertical resonant orbits triggered by the combined effects of the
linear horizontal and vertical ILRs. This leads to a B/PS bulge mainly made of
stellar material younger than the surrounding population. The non-linear
analysis of the orbital structure shows that the main orbit family responsible
for the B/PS is not the same in the two cases. The 2:2:1 orbits prevail in the
collisionless simulation whereas additional asymmetrical families contribute to
the B/PS if a dissipative component is present and can form new stars. We found
that 2:3:1 and 2:5:1 orbits trap a significant fraction of the mass. A flat
ringed discy stellar component also appears simultaneously with the thickening
of the young population. It is due to the star formation in a nuclear gaseous
disc located in the central kpc, inside the ILR, and accumulated there by the
torques exerted by the large-scale bar. Remarkably, it remains flat throughout
the simulation although it develops a nuclear bar, leading to a double-barred
galaxy. We predict that two populations of B/PS bulges could exist and even
coexist in the same galaxy.Comment: 10 pages, 11 Postscript figures, published in A&
- …