851 research outputs found
A boxy bulge in the Milky Way. Inversion of the stellar statistics equation with 2MASS data
Inverting the stellar statistics equation from 2MASS star counts, we obtain
the 3D density distribution of the Galactic bulge as well as its luminosity
function in the K-band. This results in a boxy bulge with axial ratios
1:0.5:0.4 and a major axis angle with respect to the Sun-galactic center of
.Comment: 5 pages, accepted to be published in A&
The bulge luminosity functions in the MSX infrared bands
We use an inversion technique to derive the luminosity functions of the
Galactic bulge from point source counts extracted from the Midcourse Space
Experiment's Point Source Catalog (version 1.2).Comment: 5 pages, 2 figures, to be published in A&
Azimuthal dependence of the density distribution in outer galactic discs accreting intergalactic flows
AIMS. The amplitude and scaleheight of the Galactic gas disc density are not
axisymmetric against expectations in a self-gravity axisymmetric disc. However,
this lopsidedness can be explained in terms of intergalactic accretion flows,
which produce non-axisymmetric pressure on the disc. This mechanism could be
also responsible for the formation of a warp.
METHODS. We analytically derive the relationship between the disc density and
the self-gravity and external pressure.
RESULTS. The same scenario of accretion as we proposed years ago to explain
the formation of the warp explains the azimuthal dependence of the density and
its scaleheight, with minimum/maximum in the positions of maximum amplitude of
the warp (phi=95 deg. and 275 deg.), as expected from its pressure
distribution.Comment: 4 pages, accepted to be published in A&A-letter
Modeling Star counts in the Monoceros stream and the Galactic anti-centre
There is a continued debate as to the form of the outer disc of the Milky Way
galaxy, which has important implications for its formation. Stars are known to
exist at a galacto-centric distance of at least 20 kpc. However, there is much
debate as to whether these stars can be explained as being part of the disc or
whether another extra galactic structure, the so called Monoceros ring/stream,
is required. To examine the outer disc of the Galaxy toward the anti-centre to
determine whether the star counts can be explained by the thin and thick discs
alone. Using Sloan star counts and extracting the late F and early G dwarfs it
is possible to directly determine the density of stars out to a galacto-centric
distance of about 25 kpc. These are then compared with a simple flared disc
model. A flared disc model is shown to reproduce the counts along the line of
sights examined, if the thick disc does not have a sharp cut off. The flare
starts at a Galacto-centric radius of 16 kpc and has a scale length of
4.5+/-1.5 kpc. Whilst the interpretation of the counts in terms of a
ring/stream cannot be definitely discounted, it does not appear to be
necessary, at least along the lines of sight examined towards the anti centre.Comment: 11 pages, 4 figures, accepted to be published in A&
Three-dimensional decomposition of galaxies with bulge and long bar
Some observations indicate that the Milky Way has two inner components, a
bulge and a long bar, which present a misalignment of about 20 degrees that is
against the predictions of some theoretical models that are based on numerical
simulations. In this paper, we wish to determine whether this misalignment
between the bar and the bulge can be observed in barred galaxies other than the
Milky Way. For that, each galaxy of our sample was decomposed based on its
Ks-band 2MASS image by fitting and modelling in a three-dimensional (3D) space
the following components: a disc, a bar, and a bulge. The chi-square
goodness-of-fit estimation allowed retrieving the best-fit angle values for the
bar and the bulge to detect any misalignment. From the 3D decomposition of six
barred galaxies, we have detected at least three galaxies (NGC 2217, NGC 3992,
and NGC 4593) that present a significant misalignment between the bar and the
bulge of more than 20 degrees.Comment: 8 pages, 1 figure. Accepted for publication in A&A. Corrected typo
The long Galactic bar as seen by UKIDSS Galactic Plane Survey
Over the last decade there have been a series of results supporting the
hypothesis of the existence of a long thin bar in the Milky Way with a
half-length of 4.5 kpc and a position angle of around 45 deg. This is
apparently a very different structure from the triaxial bulge of the Galaxy,
which is thicker and shorter and dominates the star counts at |l|<10 deg. In
this paper, we analyse the stellar distribution in the inner Galaxy to see if
there is clear evidence for two triaxial or bar-like structures in the Milky
Way.
By using the red-clump population as a tracer of Galactic structure, we
determine the apparent morphology of the inner Galaxy. Deeper and higher
spatial resolution NIR photometry from the UKIDSS Galactic Plane Survey allows
us to use in-plane data even at the innermost Galactic longitudes, a region
where the source confusion is a dominant effect that makes it impossible to use
other NIR databases such as 2MASS or TCS-CAIN. We show that results previously
obtained with using the red-clump giants are confirmed with the in-plane data
from UKIDSS GPS. There are two different structures coexisting in the inner
Galactic plane: one with a position angle of 23.60+-2.19 deg that can be traced
from the Galactic Centre up to l=10 deg (the Galactic bulge), and other with a
larger position angle of 42.44+-2.14 deg, that ends around l=28 deg (the long
Galactic bar).Comment: (8 pages, 14 figures, accepted for publication in A&A
Naturaleza versus Libertad
Doy mis impresiones tras leer las opiniones de Juan Arana, Javier Pérez Jara, Miguel Saralegui, Francisco José Soler Gil y Santiago Collado González sobre el tema de la Naturaleza y la libertad, así como las de los nueve filósofos del libro de Arana “Los filósofos y la libertad”: Descartes, Leibniz, Wolff, Kant, Schopenhauer, Bergson, Skinner, Popper y Dennett. También añado mi punto de vista: que Naturaleza y libertad no caben en el mismo saco.I give my impressions after reading the opinions by Juan Arana, Javier Pérez Jara, Miguel Saralegui, Francisco José Soler Gil and Santiago Collado González on the subject of Nature and Freedom, as well as the positions of the nine philosophers in Arana’s book “Los filósofos y la libertad”: Descartes, Leibniz, Wolff, Kant, Schopenhauer, Bergson, Skinner, Popper and Dennett. I also add my point of view, that Nature and Freedom are incompatibl
El espíritu de la materia. Meditaciones poético-filosóficas
Estas doce breves meditaciones poético-filosóficas son un ejercicio estilístico que trata de fusionar la sabiduría y el pensamiento con la contemplación estética. Lejos de los discursos de sectas y religiones, se habla aquí del espíritu como una metáforaThese twelve and brief poetic-philosophical meditations are one stylistic exercise that tries to fuse wisdom and thought with an aesthetic contemplation. Setting aside discourses of sects and religions, the term spirit is used here as a poetic metaphor o
Tracing the long bar with red-clump giants
Over the last decade a series of results have lent support to the hypothesis
of the existence of a long thin bar in the Milky Way with a half-length of 4.5
kpc and a position angle of around 45 deg. This is apparently a very different
structure from the triaxial bulge of the Galaxy.
In this paper, we analyse the stellar distribution in the inner 4 kpc of the
Galaxy to see if there is clear evidence for two triaxial or barlike
structures, or whether there is only one. By using the red-clump population as
a tracer of the structure of the inner Galaxy we determine the apparent
morphology of the inner Galaxy. Star counts from 2MASS are used to provide
additional support for this analysis.
We show that there are two very different large-scale triaxial structures
coexisting in the inner Galaxy: a long thin stellar bar constrained to the
Galactic plane (|b|<2 deg) with a position angle of 43.1 +- 1.8 deg, and a
distinct triaxial bulge that extends to at least |b|<7.5 deg with a position
angle of 12.6 +- 3.2 deg. The scale height of the bar source distribution is
around 100 pc, whereas for the bulge the value of this parameter is five times
larger.Comment: 16 pages, 35 figures, accepted for publication in A&
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