54 research outputs found
Vida en el Universo ¿Regla o excepción?
Nuestro planeta Tierra es hoy el único lugar conocido que alberga vida. La posible existencia de vida extraterrestre es una cuestión que ha fascinado a la humanidad durante siglos. Desde el punto de vista científico, obtener una respuesta requiere un enorme esfuerzo colaborativo entre múltiples campos de investigación científica que incluyen astronomía, física, química, biología, geología, e incluso filosofía de la ciencia. Lejos de ser exhaustivo, el presente dossier expone diferentes piezas del enorme rompecabezas que es la astrobiología, desde la exploración de nuestro Sistema Solar hasta el de los exoplanetas (planetas orbitando alrededor de otras estrellas). El dossier subraya el importante papel que juega la investigación europea para conseguir el nivel de conocimiento que poseemos, incluyendo un artículo entero dedicado a la misión espacial JUICE, de la ESA (European Space Agency), como ejemplo ilustrativo. El último artículo aborda áreas más imaginativas que describen la conexión que existe entre la música y la exploración del cosmos, mostrando que la astronomía y el arte van muy frecuentemente de la mano
Constraining the abundances of complex organics in the inner regions of solar-type protostars
The high abundances of Complex Organic Molecules (COMs) with respect to
methanol, the most abundant COM, detected towards low-mass protostars, tend to
be underpredicted by astrochemical models. This discrepancy might come from the
large beam of the single-dish telescopes, encompassing several components of
the studied protostar, commonly used to detect COMs. To address this issue, we
have carried out multi-line observations of methanol and several COMs towards
the two low-mass protostars NGC1333-IRAS2A and -IRAS4A with the Plateau de Bure
interferometer at an angular resolution of 2 arcsec, resulting in the first
multi-line detection of the O-bearing species glycolaldehyde and ethanol and of
the N-bearing species ethyl cyanide towards low-mass protostars other than IRAS
16293. The high number of detected transitions from COMs (more than 40 methanol
transitions for instance) allowed us to accurately derive the source size of
their emission and the COMs column densities. The COMs abundances with respect
to methanol derived towards IRAS2A and IRAS4A are slightly, but not
substantitally, lower than those derived from previous single-dish
observations. The COMs abundance ratios do not vary significantly with the
protostellar luminosity, over five orders of magnitude, implying that low-mass
hot corinos are quite chemically rich as high-mass hot cores. Astrochemical
models still underpredict the abundances of key COMs, such as methyl formate or
di-methyl ether, suggesting that our understanding of their formation remains
incomplete.Comment: 60 pages, 10 figures, 17 tables. Accepted for publication in Ap
Infalling-Rotating Motion and Associated Chemical Change in the Envelope of IRAS 16293-2422 Source A Studied with ALMA
We have analyzed rotational spectral line emission of OCS, CH3OH, HCOOCH3,
and H2CS observed toward the low-mass Class 0 protostellar source IRAS
16293-2422 Source A at a sub-arcsecond resolution (~0".6 x 0".5) with ALMA.
Significant chemical differentiation is found at a 50 AU scale. The OCS line is
found to well trace the infalling-rotating envelope in this source. On the
other hand, the CH3OH and HCOOCH3 distributions are found to be concentrated
around the inner part of the infalling-rotating envelope. With a simple
ballistic model of the infalling-rotating envelope, the radius of the
centrifugal barrier (a half of the centrifugal radius) and the protostellar
mass are evaluated from the OCS data to be from 40 to 60 AU and from 0.5 to 1.0
Msun, respectively, assuming the inclination angle of the envelope/disk
structure to be 60 degrees (90 degrees for the edge-on configuration). Although
the protostellar mass is correlated with the inclination angle, the radius of
the centrifugal barrier is not. This is the first indication of the centrifugal
barrier of the infalling-rotating envelope in a hot corino source. CH3OH and
HCOOCH3 may be liberated from ice mantles due to weak accretion shocks around
the centrifugal barrier, and/or due to protostellar heating. The H2CS emission
seems to come from the disk component inside the centrifugal barrier in
addition to the envelope component. The centrifugal barrier plays a central
role not only in the formation of a rotationally-supported disk but also in the
chemical evolution from the envelope to the protoplanetary disk
The two hot corinos of the SVS13-A protostellar binary system: counterposed siblings
We present ALMA high-angular resolution ( 50 au) observations of the
Class I binary system SVS13-A. We report images of SVS13-A in numerous
interstellar complex organic molecules: CHOH, CHOH,
CHCHO, CHOCH, and NHCHO. Two hot
corinos at different velocities are imaged in VLA4A (V= +7.7 km
s) and VLA4B (V= +8.5 km s). From a non-LTE analysis of
methanol lines we derive a gas density of 3 10 cm, and gas
temperatures of 140 K and 170 K for VLA4A and VLA4B, respectively. For the
other species the column densities are derived from a LTE analysis. Formamide,
which is the only N-bearing species detected in our observations, is more
prominent around VLA4A, while dimethyl ether, methanol and acetaldehyde are
associated with both VLA4A and VLA4B. We derive in the two hot corinos
abundance ratios of 1 for CHOH, CHOH, and
CHOCH, 2 for CHCHO, and 4 for
NHCHO. The present dataset supports a chemical segregation between
the different species inside the binary system. The emerging picture is that of
an onion-like structure of the two SVS13-A hot corinos, caused by the different
binding energies of the species, also supported by ad hoc quantum chemistry
calculations. In addition, the comparison between molecular and dust maps
suggests that the interstellar complex organic molecules emission originates
from slow shocks produced by accretion streamers impacting the VLA4A and VLA4B
disks and enriching the gas-phase component.Comment: 20 pages, 14 figure
Subarcsecond Analysis of Infalling-Rotating Envelope around the Class I Protostar IRAS 04365+2535
Sub-arcsecond images of the rotational line emission of CS and SO have been
obtained toward the Class I protostar IRAS 043652535 in TMC-1A with ALMA. A
compact component around the protostar is clearly detected in the CS and SO
emission. The velocity structure of the compact component of CS reveals
infalling-rotating motion conserving the angular momentum. It is well explained
by a ballistic model of an infalling-rotating envelope with the radius of the
centrifugal barrier (a half of the centrifugal radius) of 50 AU, although the
distribution of the infalling gas is asymmetric around the protostar. The
distribution of SO is mostly concentrated around the radius of the centrifugal
barrier of the simple model. Thus a drastic change in chemical composition of
the gas infalling onto the protostar is found to occur at a 50 AU scale
probably due to accretion shocks, demonstrating that the infalling material is
significantly processed before being delivered into the disk.Comment: 15 March 2016, ApJ, accepte
Vertical Structure of the Transition Zone from Infalling Rotating Envelope to Disk in the Class 0 Protostar, IRAS04368+2557
We have resolved for the first time the radial and vertical structure of the
almost edge-on envelope/disk system of the low-mass Class 0 protostar L1527.
For that, we have used ALMA observations with a spatial resolution of
0.250.13 and
0.370.23 at 0.8 mm and 1.2 mm,
respectively. The L1527 dust continuum emission has a deconvolved size of 78 au
21 au, and shows a flared disk-like structure. A thin
infalling-rotating envelope is seen in the CCH emission outward of about 150
au, and its thickness is increased by a factor of 2 inward of it. This radius
lies between the centrifugal radius (200 au) and the centrifugal barrier of the
infalling-rotating envelope (100 au). The gas stagnates in front of the
centrifugal barrier and moves toward vertical directions. SO emission is
concentrated around and inside the centrifugal barrier. The rotation speed of
the SO emitting gas is found to be decelerated around the centrifugal barrier.
A part of the angular momentum could be extracted by the gas which moves away
from the mid-plane around the centrifugal barrier. If this is the case, the
centrifugal barrier would be related to the launching mechanism of low velocity
outflows, such as disk winds
Streamers feeding the SVS13-A protobinary system: astrochemistry reveals accretion shocks?
We report ALMA high-angular resolution (~ 50 au) observations of the binary
system SVS13-A. More specifically, we analyse deuterated water (HDO) and sulfur
dioxide (SO2) emission. The molecular emission is associated with both the
components of the binary system, VLA4A and VLA4B. The spatial distribution is
compared to that of formamide (NH2CHO), previously analysed in the system.
Deuterated water reveals an additional emitting component spatially coincident
with the dust accretion streamer, at a distance larger than 120 au from the
protostars, and at blue-shifted velocities (> 3 km/s from the systemic
velocities). We investigate the origin of the molecular emission in the
streamer, in light of thermal sublimation temperatures calculated using updated
binding energies (BE) distributions. We propose that the observed emission is
produced by an accretion shock at the interface between the accretion streamer
and the disk of VLA4A. Thermal desorption is not completely excluded in case
the source is actively experiencing an accretion burst.Comment: Accepted for publication in Faraday Discussions 202
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