1,480 research outputs found
Far-IR spectroscopy towards Sagittarius B2
The far-IR is a unique wavelength range for Astrophysical studies, however,
it can only be fully sampled from space platforms. The fundamental rotational
transitions of light molecules, the high-J transitions of polyatomic species,
the bending modes of non-polar molecules, several atomic fine structure lines
and many frequencies blocked by the earth atmosphere can only be observed
between 50 and 200 um (6.0 and 1.5 THz). In this contribution we present the
far-IR spectrum of Sgr B2 at a resolution of ~35 km s^{-1}, the ``Rosetta
stone'' of ISO's far-IR spectra. We also discuss the perspectives of the far-IR
Astronomy in the context of the future telescopes under development.Comment: 4 pages, 2 figures. To appear in the Proceedings of the 4th
Cologne-Bonn-Zermatt-Symposium "The Dense Interstellar Medium in Galaxies"
eds. S. Pfalzner, C. Kramer, C. Straubmeier, & A. Heithausen (Springer:
Berlin
Far-Infrared detection of H2D+ toward Sgr B2
We report on the first far-IR detection of H2D+, using the Infrared Space
Observatory, in the line of sight toward Sgr B2 in the galactic center. The
transition at 126.853 um connecting the ground level of o-H2D+, 1_1,1 with the
the 2_1,2 level at 113 K, is observed in absorption against the continuum
emission of the cold dust of the source. The line is broad, with a total
absorption covering 350 km s^-1, i.e., similar to that observed in the
fundamental transitions of H2O, OH and CH at ~179, 119 and 149 um respectively.
For the physical conditions of the different absorbing clouds the H2D+ column
density ranges from 2 to 5x10^13 cm^-2, i.e., near an order of magnitude below
the upper limits obtained from ground based submillimeter telescopes. The
derived H2D+ abundance is of a few 10^-10, which agrees with chemical models
predictions for a gas at a kinetic temperature of ~20K.Comment: Accepted in ApJ letters. Non edite
Gravitational lens system SDSS J1339+1310: microlensing factory and time delay
We spectroscopically re-observed the gravitational lens system SDSS
J1339+1310 using OSIRIS on the GTC. We also monitored the -band variability
of the two quasar images (A and B) with the LT over 143 epochs in the period
20092016. These new data in both the wavelength and time domains have
confirmed that the system is an unusual microlensing factory. The
C emission line is remarkably microlensed, since the
microlensing magnification of B relative to that for A, ,
reaches a value of 1.4 ( 0.4 mag) for its core. Moreover, the B image
shows a red wing enhancement of C flux (relative to A),
and = 2 (0.75 mag) for the C broad-line
emission. Regarding the nuclear continuum, we find a chromatic behaviour of
, which roughly varies from 5 (1.75 mag) at 7000 \AA\ to
6 (1.95 mag) at 4000 \AA. We also detect significant microlensing
variability in the band, and this includes a number of microlensing events
on timescales of 50100 d. Fortunately, the presence of an intrinsic 0.7 mag
dip in the light curves of A and B, permitted us to measure the time delay
between both quasar images. This delay is = 47
d (1 confidence interval; A is leading), in good agreement with
predictions of lens models.Comment: Accepted to A&A; 19 pages, 2 appendices, 3 long tables (Tables 1-3).
Tables 1-2 and an updated version of Table 3 are available at
http://grupos.unican.es/glendama/q1339.ht
The far-IR spectrum of Sagittarius B2 region: Extended molecular absorption, photodissociation and photoionization
We present large scale 9'x 27'(25 pc x 70 pc) far-IR observations around Sgr
B2 using the Long-wavelength spectrometer (LWS) on board the Infrared Space
Observatory (ISO). The spectra are dominated by the strong continuum emission
of dust, the widespread molecular absorption of light hydrides (OH, CH and H2O)
and the fine structure lines of [NII], [NIII], [OIII], [CII] and [OI]. The
molecular richness in the outer layers of Sgr B2 is probed by the ISO-LWS
Fabry-Perot (35 km s^-1) detections towards Sgr B2(M), where more that 70 lines
from 15 molecular and atomic species are observed at high signal to noise
ratio.Comment: 46 pages, 10 figures, 5 tables, accepted in ApJ part I. (Figs. 1, 2,
3, 9 and 10 have been bitmapped to low resolution
Gravitational collapse of the OMC-1 region
We have investigated the global dynamical state of the Integral Shaped
Filament in the Orion A cloud using new NH (1-0) large-scale, IRAM30m
observations. Our analysis of its internal gas dynamics reveals the presence of
accelerated motions towards the Orion Nebula Cluster, showing a characteristic
blue-shifted profile centred at the position of the OMC-1 South region. The
properties of these observed gas motions (profile, extension, and magnitude)
are consistent with the expected accelerations for the gravitational collapse
of the OMC-1 region and explain both the physical and kinematic structure of
this cloud.Comment: 5 pages, 2 figures; Accepted by A&
Modelling the sulphur chemistry evolution in Orion KL
We study the sulphur chemistry evolution in the Orion KL along the gas and
grain phases of the cloud. We investigate the processes that dominate the
sulphur chemistry and to determine how physical and chemical parameters, such
as the final star mass and the initial elemental abundances, influence the
evolution of the hot core and of the surrounding outflows and shocked gas (the
plateau). We independently modelled the chemistry evolution of both components
using the time-dependent gas-grain model UCL_CHEM and considering two different
phase calculations. Phase I starts with the collapsing cloud and the depletion
of atoms and molecules onto grain surfaces. Phase II starts when a central
protostar is formed and the evaporation from grains takes place. We show how
the gas density, the gas depletion efficiency, the initial sulphur abundance,
the shocked gas temperature and the different chemical paths on the grains
leading to different reservoirs of sulphur on the mantles affect
sulphur-bearing molecules at different evolutionary stages. We also compare the
predicted column densities with those inferred from observations of the species
SO, SO2, CS, OCS, H2S and H2CS. The models that reproduce the observations of
the largest number of sulphur-bearing species are those with an initial sulphur
abundance of 0.1 times the sulphur solar abundance and a density of at least
n_H=5x10^6 cm^-3 in the shocked gas region. We conclude that most of the
sulphur atoms were ionised during Phase I, consistent with an inhomogeneous and
clumpy region where the UV interstellar radiation penetrates leading to sulphur
ionisation. We also conclude that the main sulphur reservoir on the ice mantles
was H2S. In addition, we deduce that a chemical transition currently takes
place in the shocked gas, where SO and SO2 gas-phase formation reactions change
from being dominated by O2 to being dominated by OH.Comment: 14 pages, 28 figures, 6 table
- …