240 research outputs found
La accidentalidad de los motociclistas en neiva: Entre cultura y cognición
La motocicleta se ha convertido en un elemento de primera necesidad para todas aquellas personas cuyos oficios y necesidades las llevan a optar por un medio de transporte que les genera comodidad y seguridad. Sin embargo, los accidentes de tránsito en donde se hayan involucrados los motociclistas se han constituido en una problemática social cuya causa eje es la falta de capacitación y preparación de los peatones como también de sus actores frente al modo de conducir. En Colombia, sólo el 16% de los motociclistas han tomado un curso para aprender a manejar, mientras que un 84% restante de estos lo han hecho mediante la ayuda de un amigo o familiar. La poca exigencia, por parte de las escuelas de conducción, para obtener la licencia ha impedido fortalecer un cultura preventiva de accidentes, debido a que los únicos requisitos exigidos son la fotocopia de la cédula, dos fotos, el factor sanguíneo y el pago del trámite (Fondo de Prevención Vial, 2007).Este trabajo se propone contribuir a la explicación de los comportamientos irresponsables evidenciados por los motociclistas y la generación paralela de valores subyacentes. Se analizan algunas teorías cognitivas relacionadas con los aspectos emotivos y representacionales en el área de la economía y se discute la pertinencia de elaborar un marco de trabajo interdisciplinar con el fin de describir y explicar las particularidades comportamentales de los motociclistas a la hora de obedecer las normas de tránsito convencionalizadas en sociedad
Central star formation and metallicity in CALIFA interacting galaxies
We use optical integral-field spectroscopic (IFS) data from 103 nearby
galaxies at different stages of the merging event, from close pairs to merger
remnants provided by the CALIFA survey, to study the impact of the interaction
in the specific star formation and oxygen abundance on different galactic
scales. To disentangle the effect of the interaction and merger from internal
processes, we compared our results with a control sample of 80 non-interacting
galaxies. We confirm the moderate enhancement (2-3 times) of specific star
formation for interacting galaxies in central regions as reported by previous
studies; however, the specific star formation is comparable when observed in
extended regions. We find that control and interacting star-forming galaxies
have similar oxygen abundances in their central regions, when normalized to
their stellar masses. Oxygen abundances of these interacting galaxies seem to
decrease compared to the control objects at the large aperture sizes measured
in effective radius. Although the enhancement in central star formation and
lower metallicities for interacting galaxies have been attributed to tidally
induced inflows, our results suggest that other processes such as stellar
feedback can contribute to the metal enrichment in interacting galaxies.Comment: 9 pages, 9 figures. Accepted for publication in Astronomy &
Astrophysic
A new scaling relation for HII regions in spiral galaxies: unveiling the true nature of the mass-metallicity relation
We demonstrate the existence of a -local- relation between galaxy surface
mass density, gas metallicity, and star-formation rate density using
spatially-resolved optical spectroscopy of HII regions in the local Universe.
One of the projections of this distribution, -the local mass-metallicity
relation- extends over three orders of magnitude in galaxy mass density and a
factor of eight in gas metallicity. We explain the new relation as the combined
effect of the differential radial distributions of mass and metallicity in the
discs of galaxies, and a selective star-formation efficiency. We use this local
relation to reproduce -with remarkable agreement- the total mass-metallicity
relation seen in galaxies, and conclude that the latter is a scale-up
integrated effect of a local relation, supporting the inside-out growth and
downsizing scenarios of galaxy evolution.Comment: Accepted for publication in Astrophysical Journal Letters, 5 pages, 4
figure
Bar pattern speeds in CALIFA galaxies: I. Fast bars across the Hubble sequence
The bar pattern speed () is defined as the rotational
frequency of the bar, and it determines the bar dynamics. Several methods have
been proposed for measuring . The non-parametric method
proposed by Tremaine \& Weinberg (1984; TW) and based on stellar kinematics is
the most accurate. This method has been applied so far to 17 galaxies, most of
them SB0 and SBa types. We have applied the TW method to a new sample of 15
strong and bright barred galaxies, spanning a wide range of morphological types
from SB0 to SBbc. Combining our analysis with previous studies, we investigate
32 barred galaxies with their pattern speed measured by the TW method. The
resulting total sample of barred galaxies allows us to study the dependence of
on galaxy properties, such as the Hubble type. We measured
using the TW method on the stellar velocity maps provided by
the integral-field spectroscopy data from the CALIFA survey. Integral-field
data solve the problems that long-slit data present when applying the TW
method, resulting in the determination of more accurate . In
addition, we have also derived the ratio of the corotation radius to
the bar length of the galaxies. According to this parameter, bars can be
classified as fast ( \cal{R}\%\cal{R}$ and the galaxy morphological
type. Our results indicate that independent of the Hubble type, bars have been
formed and then evolve as fast rotators. This observational result will
constrain the scenarios of formation and evolution of bars proposed by
numerical simulations.Comment: 17 pages, 10 figures, accepted for publication in A&
Ionized gas kinematics of galaxies in the CALIFA survey : I. Velocity fields, kinematic parameters of the dominant component, and presence of kinematically distinct gaseous systems
J.M.A. acknowledges support from the European Research Council Starting Grant (SEDmorph; P.I. V. Wild). Date of Acceptance: 01/08/2014Context. Ionized gas kinematics provide important clues to the dynamical structure of galaxies and hold constraints to the processes driving their evolution. Aims. The motivation of this work is to provide an overall characterization of the kinematic behavior of the ionized gas of the galaxies included in the Calar Alto Legacy Integral field Area (CALIFA), offering kinematic clues to potential users of the CALIFA survey for including kinematical criteria in their selection of targets for specific studies. From the first 200 galaxies observed by CALIFA survey in its two configurations, we present the two-dimensional kinematic view of the 177 galaxies satisfaying a gas content/detection threshold. Methods. After removing the stellar contribution, we used the cross-correlation technique to obtain the radial velocity of the dominant gaseous component for each spectrum in the CALIFA data cubes for different emission lines (namely, [O ii] λλ3726,3729, [O iii] λλ4959,5007, Hα+[N ii] λλ6548,6584, and [SII]λλ6716,6730). The main kinematic parameters measured on the plane of the sky were directly derived from the radial velocities with no assumptions on the internal prevailing motions. Evidence of the presence of several gaseous components with different kinematics were detected by using [O iii] λλ4959,5007 emission line profiles. Results. At the velocity resolution of CALIFA, most objects in the sample show regular velocity fields, although the ionized-gas kinematics are rarely consistent with simple coplanar circular motions. Thirty-five percent of the objects present evidence of a displacement between the photometric and kinematic centers larger than the original spaxel radii. Only 17% of the objects in the sample exhibit kinematic lopsidedness when comparing receding and approaching sides of the velocity fields, but most of them are interacting galaxies exhibiting nuclear activity (AGN or LINER). Early-type (E+S0) galaxies in the sample present clear photometric-kinematic misaligments. There is evidence of asymmetries in the emission line profiles in 117 out of the 177 analyzed galaxies, suggesting the presence of kinematically distinct gaseous components located at different distances from the optical nucleus. The kinematic decoupling between the dominant and secondary component/s suggested by the observed asymmetries in the profiles can be characterized by a limited set of parameters. Conclusions. This work constitutes the first determination of the ionized gas kinematics of the galaxies observed in the CALIFA survey. The derived velocity fields, the reported kinematic distortions/peculiarities and the identification of the presence of several gaseous components in different regions of the objects might be used as additional criteria for selecting galaxies for specific studies.Publisher PDFPeer reviewe
Aperture effects on the oxygen abundance determinations from CALIFA data
This paper aims at providing aperture corrections for emission lines in a
sample of spiral galaxies from the Calar Alto Legacy Integral Field Area Survey
(CALIFA) database. In particular, we explore the behavior of the
log([OIII]5007/Hbeta)/([NII]6583/Halpha) (O3N2) and log[NII]6583/Halpha (N2)
flux ratios since they are closely connected to different empirical
calibrations of the oxygen abundances in star forming galaxies.
We compute median growth curves of Halpha, Halpha/Hbeta, O3N2 and N2 up to
2.5R_50 and 1.5 disk R_eff. The growth curves simulate the effect of observing
galaxies through apertures of varying radii. The median growth curve of the
Halpha/Hbeta ratio monotonically decreases from the center towards larger
radii, showing for small apertures a maximum value of ~10% larger than the
integrated one. The median growth curve of N2 shows a similar behavior,
decreasing from the center towards larger radii. No strong dependence is seen
with the inclination, morphological type and stellar mass for these growth
curves. Finally, the median growth curve of O3N2 increases monotonically with
radius. However, at small radii it shows systematically higher values for
galaxies of earlier morphological types and for high stellar mass galaxies.
Applying our aperture corrections to a sample of galaxies from the SDSS
survey at 0.02<=z<=0.3 shows that the average difference between fiber-based
and aperture corrected oxygen abundances, for different galaxy stellar mass and
redshift ranges, reaches typically to ~11%, depending on the abundance
calibration used. This average difference is found to be systematically biased,
though still within the typical uncertainties of oxygen abundances derived from
empirical calibrations. Caution must be exercised when using observations of
galaxies for small radii (e.g. below 0.5R_eff) given the high dispersion shown
around the median growth curves.Comment: Accepted for publication in Ap
Spiral-like star-forming patterns in CALIFA early-type galaxies
Based on a combined analysis of SDSS imaging and CALIFA integral field
spectroscopy data, we report on the detection of faint (24 < {\mu}
mag/arcsec < 26) star-forming spiral-arm-like features in the periphery of
three nearby early-type galaxies (ETGs). These features are of considerable
interest because they document the still ongoing inside-out growth of some
local ETGs and may add valuable observational insight into the origin and
evolution of spiral structure in triaxial stellar systems. A characteristic
property of the nebular component in the studied ETGs, classified i+, is a
two-radial-zone structure, with the inner zone that displays faint
(EW(H\alpha)1{\AA}) low-ionization nuclear emission-line region (LINER)
properties, and the outer one (3{\AA}<EW(H\alpha)<~20{\AA}) HII-region
characteristics. This spatial segregation of nebular emission in two physically
distinct concentric zones calls for an examination of aperture effects in
studies of type i+ ETGs with single-fiber spectroscopic data.Comment: Accepted to A&A, 5 pages, 1 figur
UV and FIR selected samples of galaxies in the local Universe. Dust extinction and star formation rates
We have built two samples of galaxies selected at 0.2micron (hereafter UV)
and 60micron (hereafter FIR) covering a sky area of 35.36 deg^2. The UV
selected sample contains 25 galaxies brighter than AB_0.2=17mag. All of them,
but one elliptical, are detected at 60micron with a flux density larger or
equal to 0.2Jy. The UV counts are significantly lower than the euclidean
extrapolation towards brighter fluxes of previous determinations. The FIR
selected sample contains 42 galaxies brighter than f_60=0.6Jy. Excepting four
galaxies, all of them have a UV counterpart at the limiting magnitude
AB_0.2=20.3mag. The mean extinction derived from the analysis of the FIR to UV
flux ratio is ~1mag for the UV selected sample and ~2mag for the FIR selected
one. For each sample we compare several indicators of the recent star formation
rate (SFR) based on the FIR and/or the UV emissions and we find linear
relationships with slopes close to unity, meaning that no trend with the SFR
exists when converting between each other. Various absolute calibrations for
both samples are discussed in this paper. A positive correlation between
extinction and SFR is found when both samples are considered together although
with a considerable scatter. A similar result is obtained when using the SFR
normalized to the optical surface of the galaxies.Comment: 34 pages, 17 figures. Accepted for publication in A&
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