377 research outputs found
Free-free and H42alpha emission from the dusty starburst within NGC 4945 as observed by ALMA
We present observations of the 85.69 GHz continuum emission and H42alpha line
emission from the central 30 arcsec within NGC 4945. Both sources of emission
originate from nearly identical structures that can be modelled as exponential
discs with a scale length of ~2.1 arcsec (or ~40 pc). An analysis of the
spectral energy distribution based on combining these data with archival data
imply that 84% +/- 10% of the 85.69 GHz continuum emission originates from
free-free emission. The electron temperature is 5400 +/- 600 K, which is
comparable to what has been measured near the centre of the Milky Way Galaxy.
The star formation rate (SFR) based on the H42alpha and 85.69 GHz free-free
emission (and using a distance of 3.8 Mpc) is 4.35 +/- 0.25 M/yr. This is
consistent with the SFR from the total infrared flux and with previous
measurements based on recombination line emission, and it is within a factor of
~2 of SFRs derived from radio data. The Spitzer Space Telescope 24 micron data
and Wide-field Infrared Survey Explorer 22 micron data yield SFRs ~10x lower
than the ALMA measurements, most likely because the mid-infrared data are
strongly affected by dust attenuation equivalent to A_V=150. These results
indicate that SFRs based on mid-infrared emission may be highly inaccurate for
dusty, compact circumnuclear starbursts.Comment: 19 pages, 9 figures, accepted for publication in MNRA
The Herschel Space Observatory view of dust in M81
We use Herschel Space Observatory data to place observational constraints on the peak and Rayleigh-Jeans slope of dust emission observed at 70−500 μm in the nearby spiral galaxy M81. We find that the ratios of wave bands between 160 and 500 μm are primarily dependent on radius but that the ratio of 70 to 160 μm emission shows no clear dependence on surface brightness or radius. These
results along with analyses of the spectral energy distributions imply that the 160−500 μm emission traces 15−30 K dust heated by evolved stars in the bulge and disc whereas the 70 μm emission includes dust heated by the active galactic nucleus and young stars in star forming regions
ALMA observations of 99 GHz free-free and H40 line emission from star formation in the centre of NGC 253
We present Atacama Large Millimeter/submillimeter Array observations of 99.02
GHz free-free and H40 emission from the centre of the nearby starburst
galaxy NGC 253. We calculate electron temperatures of 3700-4500 K for the
photoionized gas, which agrees with previous measurements. We measure a
photoionizing photon production rate of s and
a star formation rate of M yr within the central
2010 arcsec, which fall within the broad range of measurements from
previous millimetre and radio observations but which are better constrained. We
also demonstrate that the dust opacities are ~3 dex higher than inferred from
previous near-infrared data, which illustrates the benefits of using millimetre
star formation tracers in very dusty sources.Comment: 5 pages, 3 figures, accepted for publication in MNRAS Letter
Tests of star formation metrics in the low metallicity galaxy NGC 5253 using ALMA observations of H30 line emission
We use Atacama Large Millimeter/submillimeter Array (ALMA) observations of
H30 (231.90 GHz) emission from the low metallicity dwarf galaxy NGC
5253 to measure the star formation rate (SFR) within the galaxy and to test the
reliability of SFRs derived from other commonly-used metrics. The H30
emission, which originates mainly from the central starburst, yields a
photoionizing photon production rate of (1.90.3)10 s
and an SFR of 0.0870.013 M yr based on conversions that
account for the low metallicity of the galaxy and for stellar rotation. Among
the other star formation metrics we examined, the SFR calculated from the total
infrared flux was statistically equivalent to the values from the H30
data. The SFR based on previously-published versions of the H flux that
were extinction corrected using Pa and Pa lines were lower than
but also statistically similar to the H30 value. The mid-infrared (22
m) flux density and the composite star formation tracer based on H
and mid-infrared emission give SFRs that were significantly higher because the
dust emission appears unusually hot compared to typical spiral galaxies.
Conversely, the 70 and 160 m flux densities yielded SFR lower than the
H30 value, although the SFRs from the 70 m and H30 data
were within 1-2 of each other. While further analysis on a broader
range of galaxies are needed, these results are instructive of the best and
worst methods to use when measuring SFR in low metallicity dwarf galaxies like
NGC 5253.Comment: 14 pages, 5 figures, accepted for publication in MNRA
Total Infrared Luminosity Estimation of Resolved and Unresolved Galaxies
The total infrared (TIR) luminosity from galaxies can be used to examine both
star formation and dust physics. We provide here new relations to estimate the
TIR luminosity from various Spitzer bands, in particular from the 8 micron and
24 micron bands. To do so, we use 45" subregions within a subsample of nearby
face-on spiral galaxies from the Spitzer Infrared Nearby Galaxies Survey
(SINGS) that have known oxygen abundances as well as integrated galaxy data
from the SINGS, the Local Volume Legacy Survey (LVL) and Engelbracht et al.
(2008) samples. Taking into account the oxygen abundances of the subregions,
the star formation rate intensity, and the relative emission of the polycyclic
aromatic hydrocarbons at 8 micron, the warm dust at 24 micron and the cold dust
at 70 micron and 160 micron we derive new relations to estimate the TIR
luminosity from just one or two of the Spitzer bands. We also show that the
metallicity and the star formation intensity must be taken into account when
estimating the TIR luminosity from two wave bands, especially when data
longward of 24 micron are not available.Comment: 11 pages, 10 figures, accepted for publication in Ap
LABOCA and MAMBO-2 imaging of the dust ring of the Sombrero galaxy (NGC 4594)
The Sombrero galaxy (NGC 4594) is an Sa galaxy with a symmetric dust ring. We
have used the Large APEX BOlometer CAmera (LABOCA) at 870 micron and the
MAx-Planck Millimeter BOlometer (MAMBO-2) at 1.2 mm to detect the dust ring for
the first time at submillimetre and millimetre wavelengths. We have constructed
a model of the galaxy to separate the active galactic nucleus (AGN) and dust
ring components. The ring radius at both 870 micron and 1.2 mm agrees well with
the radius determined from optical absorption and atomic gas studies. The
spectral energy distribution of the ring is well fitted by a single grey-body
with dust emissivity index beta=2 and a dust temperature T_d=18.4 K. The dust
mass of the ring is found to be 1.6\pm0.2x10^7Msun which, for a Galactic
gas-to-dust ratio, implies a gas mass that is consistent with measurements from
the literature.Comment: 4 pages including 3 figures and 2 tables. Accepted for publication in
A&A Letters. Full resolution version at
http://www.strw.leidenuniv.nl/~vlahakis/vlahakis-highres.pd
Plurilingüismo: por qué ser personas plurilingües y cuándo iniciar el aprendizaje
Treball Final de Grau en Mestre o Mestra d'Educació Primària. Codi: MP1040. Curs acadèmic: 2016/2017Entendemos como plurilingüismo aquellas variedades lingüísticas que utiliza un mismo locutor, ya sea la lengua materna y todas aquellas adquiridas posteriormente. Tenemos al alcance la opción de enriquecernos con lenguas diferentes a la nuestra y esto se considera un aspecto muy importante para el acceso a las manifestaciones culturales.
La lengua regula nuestro pensamiento y todas nuestras ideas apoyadas por bases lingüísticas. Además, como seres sociales contamos con la necesidad de relacionarnos y de comunicarnos, para hacernos hueco en el progreso continuo de la sociedad. Por esta misma razón, se deben tener en cuenta ciertos aspectos culturales, características personales de los individuos de una sociedad y a qué estratificación social pertenecen, para poder llevar a cabo una Competencia Comunicativa adecuada.
La conciencia es cada vez mayor en cuanto a la función que desempeñan los idiomas en el desarrollo, la diversidad cultural y en el fortalecimiento de la cooperación y la conservación del patrimonio cultural. Siempre se ha considerado esencial el aprendizaje de idiomas desde edades tempranas para poder exprimir esos conocimientos de cara al futuro, pero, ¿qué impacto tiene el plurilingüismo y el aprendizaje de nuevas lenguas en edades adultas? El derecho a aprender a lo largo de toda la vida es cada vez más ratificado, no obstante, la educación de adultos se encuentra muy rezagada con respecto a los demás sectores de la enseñanza.
A lo largo de este trabajo de investigación descubriremos las ventajas cognitivas que presenta el plurilingüismo en la Educación para Adultos así como la eficiencia y los beneficios a los cuales llevan
Diffuse far-infrared and ultraviolet emission in the NGC4435/4438 system: tidal stream or Galactic cirrus?
We report the discovery of diffuse far-infrared and far-ultraviolet emission
projected near the interacting pair NGC4435/4438, in the Virgo cluster. This
feature spatially coincides with a well known low surface-brightness optical
plume, usually interpreted as tidal debris. If extragalactic, this stream would
represent not only one of the clearest examples of intracluster dust, but also
a rare case of intracluster molecular hydrogen and large-scale intracluster
star formation. However, the ultraviolet, far-infrared, HI and CO emission as
well as the dynamics of this feature are extremely unusual for tidal streams
but are typical of Galactic cirrus clouds. In support to the cirrus scenario,
we show that a strong spatial correlation between far-infrared and
far-ultraviolet cirrus emission is observed across the center of the Virgo
cluster, over a scale of several degrees. This study demonstrates how dramatic
Galactic cirrus contamination can be, even at optical and ultraviolet
wavelengths and at high galactic latitudes. If ignored, the presence of diffuse
light scattered by Galactic dust clouds could significantly bias our
interpretation of low surface-brightness features and diffuse light observed
around galaxies and in clusters of galaxies.Comment: 6 pages, 4 figures. Accepted for publication in MNRAS Letter
A Multi-Wavelength Infrared Study of NGC 891
We present a multi-wavlength infrared study of the nearby, edge-on, spiral
galaxy NGC 891. We have examined 20 independent, spatially resolved IR images
of this galaxy, 14 of which are newly reduced and/or previously unpublished
images. These images span a wavelength regime from 1.2 microns in which the
emission is dominated by cool stars, through the MIR, in which emission is
dominated by PAHs, to 850 microns, in which emission is dominated by cold dust
in thermal equilibrium with the radiation field. The changing morphology of the
galaxy with wavelength illustrates the changing dominant components. We detect
extra-planar dust emission in this galaxy, consistent with previously published
results, but now show that PAH emission is also in the halo, to a vertical
distance of z >= 2.5 kpc. We compare the vertical extents of various components
and find that the PAHs (from 7.7 and 8 micron data) and warm dust (24 microns)
extend to smaller z heights than the cool dust (450 microns). For six locations
in the galaxy for which the S/N was sufficient, we present SEDs of the IR
emission, including two in the halo - the first time a halo SED in an external
galaxy has been presented. We have modeled these SEDs and find that the PAH
fraction is similar to Galactic values (within a factor of two), with the
lowest value at the galaxy's center, consistent with independent results of
other galaxies. In the halo environment, the fraction of dust exposed to a
colder radiation field, is of order unity, consistent with an environment in
which there is no star formation. The source of excitation is likely from
photons escaping from the disk.Comment: 24 pages, 17 figures, 7 tables, accepted for publication in MNRA
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