358 research outputs found
Protoplanetary gas disks in the far infrared
The physical and chemical conditions in young protoplanetary disks set the
boundary conditions for planet formation. Although the dust in disks is
relatively easily detected as a far-IR photometric ``excess'' over the expected
photospheric emission, much less is known about the gas phase. It seems clear
that an abrupt transition from massive optically thick disks (gas-rich
structures where only ~1% of the total mass is in the form of dust) to tenuous
debris disks almost devoid of gas occurs at ~10^7 years, by which time the
majority of at least the giant planets must have formed. Indeed, these planets
are largely gaseous and thus they must assemble before the gas disk dissipates.
Spectroscopic studies of the disk gas content at different evolutive stages are
thus critical. Far-IR water vapor lines and atomic fine structure lines from
abundant gas reservoirs (e.g., [OI]63um, [SI]56um, [SiII]34um) are robust
tracers of the gas in disks. Spectrometers on board Herschel will detect some
of these lines toward the closest, youngest and more massive protoplanetary
disks. However, according to models, Herschel will not reach the required
sensitivity to (1) detect the gas residual in more evolved and tenuous
transational disks that are potentially forming planets and (2) detect the gas
emission from less massive protoplanetary disks around the most numerous stars
in the Galaxy (M-type and cooler dwarfs). Both are unique goals for
SPICA/SAFARI. Besides, SAFARI will be able to detect the far-IR modes of water
ice at ~44 and ~62um, and thus allow water ice to be observed in many
protoplanetary systems and fully explore its impact on planetary formation and
evolution.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for
Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies".
Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche
Stellar Feedback in the ISM Revealed by Wide-Field Far-Infrared Spectral-Imaging
The radiative and mechanical interaction of stars with their environment
drives the evolution of the ISM and of galaxies as a whole. The far-IR emission
(lambda ~30 to 350 microns) from atoms and molecules dominates the cooling of
the warm gas in the neutral ISM, the material that ultimately forms stars.
Far-IR lines are thus the most sensitive probes of stellar feedback processes,
and allow us to quantify the deposition and cycling of energy in the ISM. While
ALMA (in the (sub)mm) and JWST (in the IR) provide astonishing sub-arcsecond
resolution images of point sources and their immediate environment, they cannot
access the main interstellar gas coolants, nor are they designed to image
entire star-forming regions (SFRs). Herschel far-IR photometric images of the
interstellar dust thermal emission revealed the ubiquitous large-scale
filamentary structure of SFRs, their mass content, and the location of
thousands of prestellar cores and protostars. These images, however, provide a
static view of the ISM: not only they dont constrain the cloud dynamics,
moreover they cannot reveal the chemical composition and energy transfer within
the cloud, thus giving little insight into the regulation process of star
formation by stellar feedback. In this white paper we emphasize the need of a
space telescope with wide-field spectral-imaging capabilities in the critical
far-IR domain.Comment: White Paper submitted to the Astro 2020 Decadal Survey on Astronomy
and Astrophysics (National Academies of Science, Engineering, and Medicine
Interstellar Hydrides
Interstellar hydrides -- that is, molecules containing a single heavy element
atom with one or more hydrogen atoms -- were among the first molecules detected
outside the solar system. They lie at the root of interstellar chemistry, being
among the first species to form in initially-atomic gas, along with molecular
hydrogen and its associated ions. Because the chemical pathways leading to the
formation of interstellar hydrides are relatively simple, the analysis of the
observed abundances is relatively straightforward and provides key information
about the environments where hydrides are found. Recent years have seen rapid
progress in our understanding of interstellar hydrides, thanks largely to
far-IR and submillimeter observations performed with the Herschel Space
Observatory. In this review, we will discuss observations of interstellar
hydrides, along with the advanced modeling approaches that have been used to
interpret them, and the unique information that has thereby been obtained.Comment: Accepted for publication in Annual Review of Astronomy and
Astrophysics 2016, Vol. 5
A new Unidentified Far Infrared Band in NGC7027
We report on the detection of a molecular band centered at ~98 um (~102
cm^-1), observed with the Infrared Space Observatory in the young Planetary
Nebula NGC7027. The band structure and intensity can not be reproduced by
atomic fine structure lines, recombination lines or by the rotational emission
of abundant molecules. We discuss the possible contribution of the low-energy
bending modes of pure carbon chains to the unidentified far-IR bands (UfIBs)
observed in C-rich evolved objects. In particular, we speculate that the band
emission could arise from the nu_9 and nu_7 bending modes of C_6 and C_5, for
which wavenumbers of 90+/-50 and 107+/-5 cm^-1 have been estimated from
photoelectron spectroscopy.Comment: 15 pages, 2 figures, accepted in ApJ part
Formation of interstellar SH from vibrationally excited H: Quantum study of S + H SH + H reactions and inelastic collisions
The rate constants for the formation, destruction, and collisional excitation
of SH are calculated from quantum mechanical approaches using two new
SH potential energy surfaces (PESs) of and electronic
symmetry. The PESs were developed to describe all adiabatic states correlating
to the SH () + H() channel. The formation of SH
through the S + H reaction is endothermic by 9860 K, and
requires at least two vibrational quanta on the H molecule to yield
significant reactivity. Quasi-classical calculations of the total formation
rate constant for H() are in very good agreement with the quantum
results above 100K. Further quasi-classical calculations are then performed for
, 4, and 5 to cover all vibrationally excited H levels significantly
populated in dense photodissociation regions (PDR). The new calculated
formation and destruction rate constants are two to six times larger than the
previous ones and have been introduced in the Meudon PDR code to simulate the
physical and illuminating conditions in the Orion bar prototypical PDR. New
astrochemical models based on the new molecular data produce four times larger
SH column densities, in agreement with those inferred from recent ALMA
observations of the Orion bar.Comment: 8 pages, 7 figure
The interstellar gas seen in the mid- and far-infrared: The promise of SPICA Space Telescope
The mid- and far-IR spectral ranges are critical windows to characterize the
physical and chemical processes that transform the interstellar gas and dust
into stars and planets. Sources in the earliest phases of star formation and in
the latest stages of stellar evolution release most of their energy at these
wavelengths. Besides, the mid- and far-IR ranges provide key spectral
diagnostics of the gas chemistry (water, light hydrides, organic species ...),
of the prevailing physical conditions (H2, atomic fine structure lines...), and
of the dust mineral and ice composition that can not be observed from
ground-based telescopes. With the launch of JAXA's SPICA telescope,
uninterrupted studies in the mid- and far-IR will be possible since ESA's
Infrared Space Observatory (1995). In particular, SAFARI will provide full
access to the 34-210um waveband through several detector arrays and flexible
observing modes (from broadband photometry to medium resolution spectroscopy
with R~3,000 at 63um), and reaching very high line sensitivities (~10^-19
Wm^-2, 5sigma-1hr) within a large FOV (~2'x2'). Compared to previous far-IR
instruments (ISO/LWS, Akari/FIS, Spitzer/MIPS and Herschel/PACS), SAFARI will
provide a superior way to obtain fully-sampled spectro-images and continuous
SEDs of very faint and extended ISM sources in a wavelength domain not
accessible to JWST or ALMA. The much increased sensitivity of SPICA will allow
us to step forward and reveal not only the chemical complexity in the local
ISM, but also in the extragalactic ISM routinely.Comment: To appear in Proc. Workshop "The Space Infrared Telescope for
Cosmology & Astrophysics: Revealing the Origins of Planets and Galaxies".
Eds. A.M. Heras, B. Swinyard, K. Isaak, and J.R. Goicoeche
The initial gas-phase sulfur abundance in the Orion Molecular Cloud from sulfur radio recombination lines
The abundances of chemical elements and their depletion factors are essential
parameters for understanding the composition of the gas and dust that are
ultimately incorporated into stars and planets. Sulfur is an abundant but
peculiar element in the sense that, despite being less volatile than other
elements (e.g., carbon), it is not a major constituent of dust grains in
diffuse interstellar clouds. Here, we determine the gas-phase carbon-to-sulfur
abundance ratio, [C]/[S], and the sulfur abundance [S] in a dense star-forming
cloud from new radio recombination lines (RRLs) detected with the Yebes 40m
telescope - at relatively high frequencies (~40 GHz ~7 mm) and angular
resolutions (down to 36'') - in the Orion Bar, a rim of the Orion Molecular
Cloud (OMC). We detect nine Cn\alpha RRLs (with n=51 to 59) as well as nine
narrow line features separated from the Cn\alpha lines by delta v=-8.4+/-0.3 km
s^-1. Based on this velocity separation, we assign these features to sulfur
RRLs, with little contribution of RRLs from the more condensable elements Mg,
Si, or Fe. Sulfur RRLs lines trace the photodissociation region (PDR) of the
OMC. In these predominantly neutral gas layers, up to A_V~4, the ions C+ and S+
lock in most of the C and S gas-phase reservoir. We determine a relative
abundance of [C]_Ori/[S]_Ori=10.4+/-0.6 and, adopting the same [C]_Ori measured
in the translucent gas toward star theta^1 Ori B, an absolute abundance of
[S]_Ori=(1.4+/-0.4)x10^-5. This value is consistent with emission models of the
observed sulfur RRLs if N(S+)~7x10^17 cm^-2 (beam-averaged). The [S]_Ori is the
''initial'' sulfur abundance in the OMC, before an undetermined fraction of the
[S]_Ori goes into molecules and ice mantles in the cloud interior. The inferred
abundance [S]_Ori matches the solar abundance, thus implying that there is
little depletion of sulfur onto rocky dust grains, with D(S)=0.0+/-0.2 dex.Comment: Accepted for publication in Astronomy & Astrophysics Letters. 9 pages
including Appendi
Vers une base de ecoethics
La ética ambiental o Ecoética, nace como respuesta a la degradación del entorno de la vida humana en nuestros tiempos, tomando como referencia los valores y principios de una ética aplicada a diferentes sectores profesionales que inciden de manera directa con su actividad en el medio. Intentamos, así, fundamentar una ética medioambiental desde los mismos presupuestos que cualquier ética aplicada, desde la propia génesis de nuestra conciencia moral individual hasta la particularidad de la pluralidad de sectores a los que debe dirigirse.Environmental or ecoethics, ethics developed in response to environmental degradation of human life in our times, with reference to the values and principles of professional ethics applied to different sectors directly affect its activity in the medium. Try, so base an environmental ethic from the same assumptions applied to any ethical, from the genesis of our individual conscience to the particularity of the plurality of sectors to be targeted.L'environnement ou ecoethics, éthique développés en réponse à la dégradation de l'environnement de la vie humaine à notre époque, en référence aux valeurs et principes de l'éthique professionnelle appliqués aux différents secteurs affecter directement son activité dans le milieu. Essayez, si fonder une éthique de l'environnement à partir des mêmes hypothèses appliquées à toute éthique, de la genèse de notre conscience individuelle à la particularité de la pluralité de secteurs à cibler
The Horsehead nebula, a template source for interstellar physics and chemistry
We present a summary of our previous investigations of the physical and
chemical structure of the Horsehead nebula, and discuss how these studies led
to advances on the understanding of the impact of FUV radiation on the
structure of dense interstellar clouds. Specific molecular tracers can be used
to isolate different environments, that are more sensitive to changes in the
FUV radiation or density than the classical tracers of molecular gas : the CO
isotopologues or the dust (sub)millimeter continuum emission. They include the
HCO or CCH radicals for the FUV illuminated interfaces, or the molecular ions
HCO, DCO and other deuterated species (DNC, DCN) for the cold
dense core. We discuss future prospects in the context of Herschel and ALMA
Description of the organizational and curricular development of different types of centres and educational stages
[Es] Esta aportación sintetiza el estudio que están desarrollando profesores del Área de Didáctica y Organización escolar de la UPV y de la UAB (2005-06). Su contenido aborda las relaciones entre los estadios de desarrollo organizativo y curricular y los resultados escolares. Los primeros datos sugieren que hay una mayor cohesión y coherencia en los centros pequeños, de titularidad pública y de un solo modelo lingüístico. Curiosamente, esta aparente identidad común se apoya más en la estructura participativa y en los sistemas de aprendizaje organizacional y no tanto en la cultura institucional y la cultura colaborativa. Estas últimas
dependen más del tamaño del centro y del modelo lingüístico que de la titularidad. Llama la atención que el liderazgo transformacional se vincula más a la titularidad pública y a los centros de secundaria, no relacionándose significativamente con el tamaño del centro, el modelo lingüístico o los años vinculados al ejercicio de cargos.[En] This contribution synthesizes the study that there are developing teachers of the Area of Didactics and school Organization of the UPV and of the UAB (2005-06). His content
approaches the relations between the stadiums of organizational development and curricular and the school results. The first information suggests that there is a major cohesion and coherence in the small centres, of public ownership and of an alone linguistic model. Curiously, this apparent common identity rests more on the participative structure and on the
systems of learning organizational and not so much on the institutional culture and the
collaborative culture. The above mentioned depend more of the size of the centre and of the linguistic model that of the ownership. The attention calls that the leadership transformational links itself more to the public ownership and to the centres of secondary, not relating significantly to the size of the centre, the linguistic model or the years linked to the exercise of charges
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