956 research outputs found
Stellar Populations in the Outskirts of the Small Magellanic Cloud: No Outer Edge Yet
We report the detection of intermediate-age and old stars belonging to the
SMC at 6.5 kpc from the SMC center in the southern direction. We show, from the
analysis of three high quality 34\arcmin 33\arcmin CMDs, that the age
composition of the stellar population is similar at galactocentric distances of
4.7 kpc, 5.6 kpc, and 6.5 kpc. The surface
brightness profile of the SMC follows an exponential law, with no evidence of
truncation, all the way out to 6.5 kpc. These results, taken together, suggest
that the SMC `disk' population is dominating over a possible old Milky Way-like
stellar halo, and that the SMC may be significantly larger than previously
thought.Comment: Accepted for publication in ApJ Letters. High resolution figures are
available at ftp://ftp.iac.es/out/noe
The origin of the LMC stellar bar: clues from the SFH of the bar and inner disk
We discuss the origin of the LMC stellar bar by comparing the star formation
histories (SFH) obtained from deep color-magnitude diagrams (CMDs) in the bar
and in a number of fields in different directions within the inner disk. The
CMDs, reaching the oldest main sequence turnoffs in these very crowded fields,
have been obtained with VIMOS on the VLT in service mode, under very good
seeing conditions. We show that the SFHs of all fields share the same patterns,
with consistent variations of the star formation rate as a function of time in
all of them. We therefore conclude that no specific event of star formation can
be identified with the formation of the LMC bar, which instead likely formed
from a redistribution of disk material that occurred when the LMC disk became
bar unstable, and shared a common SFH with the inner disk thereafter. The
strong similarity between the SFH of the center and edge of the bar rules out
significant spatial variations of the SFH across the bar, which are predicted
by scenarios of classic bar formation through buckling mechanisms.Comment: MNRAS Letters, accepte
Spatially resolved LMC star formation history: I. Outside in evolution of the outer LMC disk
We study the evolution of three fields in the outer LMC disk Rgc=3.5-6.2 Kpc.
Their star formation history indicates a stellar populations gradient such that
younger stellar populations are more centrally concentrated. We identify two
main star forming epochs, separated by a period of lower activity between ~7
and ~4 Gyr ago. Their relative importance varies from a similar amount of stars
formed in the two epochs in the innermost field, to only 40% of the stars
formed in the more recent epoch in the outermost field. The young star forming
epoch continues to the present time in the innermost field, but lasted only
till ~0.8 and 1.3 Gyr ago at Rgc=5.5 degrees and 7.1 degrees, respectively.
This gradient is correlated with the measured HI column density and implies an
outside-in quenching of the star formation, possibly related to a variation of
the size of the HI disk. This could either result from gas depletion due to
star formation or ram-pressure stripping, or from to the compression of the gas
disk as ram-pressure from the Milky Way halo acted on the LMC interstellar
medium. The latter two situations may have occurred when the LMC first
approached the Milky Way.Comment: 15 pages, 13 figures, 4 tables. MNRAS, in pres
The Star Formation History in a SMC field: IAC-star/IAC-pop at work
We present a progress report of a project to study the quantitative star
formation history (SFH) in different parts of the Small Magellanic Cloud (SMC).
We use the information in [(B-R), R] color-magnitude diagrams (CMDs), which
reach down to the oldest main-sequence turnoffs and allow us to retrieve the
SFH in detail. We show the first results of the SFH in a SMC field located in
the Southern direction (at 1 kpc from the SMC center). This field is
particularly interesting because in spite of being located in a place in which
the HI column density is very low, it still presents a recent enhancement of
star formation.Comment: Poster presented at: Stellar Populations as Building Blocks of
Galaxies, Proceedings IAU Symposium No. 241, 200
Spatial dependence of the Star Formation History in the Central Regions of the Fornax Dwarf Spheroidal Galaxy
We present the Star Formation History (SFH) and the age-metallicity relation
(AMR) in three fields of the Fornax dwarf spheroidal galaxy. They sample a
region spanning from the centre of the galaxy to beyond one core radius, which
allows studying galactocentric gradients. In all the cases, we found stars as
old as 12 Gyr, together with intermediate-age and young stellar populations.
The last star formation events, as young as 1 Gyr old, are mainly located in
the central region, which may indicate that the gas reservoir in the outer
parts of the galaxy would have been exhausted earlier than in the centre or
removed by tidal interactions. The AMR is smoothly increasing in the three
analyzed regions and similar to each other, indicating that no significant
metallicity gradient is apparent within and around the core radius of Fornax.
No significant traces of global UV-reionization or local SNe feedback are
appreciated in the early SFH of Fornax.
Our study is based on FORS1@VLT photometry as deep as I~24.5 and the
IAC-star/IAC-pop/MinnIAC suite of codes for the determination of the SFH in
resolved stellar populations.Comment: 13 pages, 8 figures, 4 table
Manifestacions glaciaires quaternaires dans le haut bassin du Llobregat (Prépyrénées Catalanes)
La fijación externa en el tratamiento de las fracturas de extremidad distal de radio: Revisión de 83 casos
Se presenta un estudio retrospectivo de 83 casos de fractura de extremidad distal de radio tratadas con fijación externa, exclusivamente o asociada a otros métodos de tratamiento, con un seguimiento medio de 15 meses. Se han revisado las indicaciones y se han valorado los resultados mediante el protocolo de evaluación clÃnica propuesto por Gartland y Werley, modificado por Sarmiento; y la evaluación radiológica según los criterios de Linström, ampliados por Van Der Linden y Ericsson. Se obtuvieron resultados excelentes en 9 casos, buenos en 44 casos, regulares en 24 y malos en 6 casos. La complicación más frecuente hallada fue la osteopenia difusa del carpo (50%) y la causa más común de discapacidad residual, la articulación radiocubital distal. De los resultados concluimos que la fijación externa es un método correcto para el tratamiento de las fracturas de extremidad distal de radio, aunque son necesarias en algunos casos otras técnicas añadidas para conseguir una aceptable congruencia articular y minimizar la cifra de resultados inaceptables.Retrospective study on 83 cases of distal radius fractures in treatment with external fixation, exclusively or associated with other treatment methods, with an average follow-up of 45 months. Indications have been revised and results have been valued through the medical record of clinical evaluation proposed by Gartland and Werley, modified by Sarmiento, and the radiological evaluation accordinf to Linström's criterions, amplified by Van Der Linden and Ericson. Excellent results have been obtained in 9 cases, good ones in 44 cases, not bad ones in 24 cases, bad ones in 6 cases. The most frequent complication found was the carpus wide osteopeny (50%) and the most common cause of residual discapacity, the distal radioulnar joint. We conclude, from the results, that the external fixation is a correct method for the treatment of distal radius fractures, although other added techniques are necessary, in some cases, in order to achieve an acceptable articular congruity and minimize the number of unacceptable results
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