240 research outputs found
Observations of V838 Mon in the CO rotational lines
We investigate the structure of a field around the position of V838 Mon as
seen in the lowest CO rotational transitions. We also measure and analyse
emission in the same lines at the position of V838 Mon.Observations have
primarily been done in the CO J = 2-1 and J = 3-2 lines using the KOSMA
telescope. A field of 3.4 squared degrees has been mapped in the on-the-fly
mode in these transitions. Longer integration spectra in the on-off mode have
been obtained to study the emission at the position of V838 Mon. Selected
positions in the field have also been observed in the CO J = 1-0 transition
using the Delingha telescope.In the observed field we have identified many
molecular clouds. They can be divided into two groups from the point of view of
their observed radial velocities. One, having V(LSR) in the range 18-32 km/s,
can be identified with the Perseus Galactic arm. The other one, having V(LSR)
between 44-57 km/s, probably belongs to the Norma-Cygnus arm. The radial
velocity of V838 Mon is within the second range but the object does not seem to
be related to any of the observed clouds. We did not find any molecular buble
of a 1 degree dimension around the position of V838 Mon claimed in van Loon et
al. An emission has been detected at the position of the object in the CO J =
2-1 and J = 3-2 transitions. The emission is very narrow (FWHM ~ 1.2 km/s) and
at V(LSR) = 53.3 km/s. Our analysis of the data suggests that the emission is
probably extended.Comment: paper accepted in A&
Mexican World Heritage information on the web: Institutional presence and visibility
This study offers a global overview of the presence and visibility of web information on UNESCO World Heritage located in Mexico, via the analysis of official websites and Web 2.0 information. Cultural heritage is a
determining factor in linking people to their history, and contributes to increasing cultural tourism and economic development. The study starts from the hypothesis that the design of these has an influence on the dissemination
and popularity of the aforementioned heritage. The relationships between the administrative organization of the country and Internet protocols are compared. A webometric study of the official Mexican websites was carried
out. An evaluation sheet was designed to allow the assessment of aspects relating to identification, presence, accessibility and content. The multilingual nature of this information and its presence on social networks
and Wikipedia was analysed. The analysis of URLs confirms that the domain .mx is used in 84% of cases. The results indicate a noticeable use of Web 2.0 dissemination of the heritage assets on YouTube (51%) and Facebook (40%),
followed by 23% on Twitter. The Web Accessibility Initiative (WAI) guidelines are not yet frequently applied. Finally, the results obtained make it possible to identify variables that can contribute to improvements in the visibility and dissemination of official web information.This paper was supported by the RD & I Project, HAR2012-38562 (Spanish Ministry of Economy and Competitiveness)
First results on Martian carbon monoxide from Herschel/HIFI observations
We report on the initial analysis of Herschel/HIFI carbon monoxide (CO)
observations of the Martian atmosphere performed between 11 and 16 April 2010.
We selected the (7-6) rotational transitions of the isotopes ^{13}CO at 771 GHz
and C^{18}O at 768 GHz in order to retrieve the mean vertical profile of
temperature and the mean volume mixing ratio of carbon monoxide. The derived
temperature profile agrees within less than 5 K with general circulation model
(GCM) predictions up to an altitude of 45 km, however, show about 12-15 K lower
values at 60 km. The CO mixing ratio was determined as 980 \pm 150 ppm, in
agreement with the 900 ppm derived from Herschel/SPIRE observations in November
2009.Comment: Accepted for publication in Astronomy and Astrophysics (special issue
on HIFI first results); minor changes to match published versio
The Antarctic Submillimeter Telescope and Remote Observatory (AST/RO)
AST/RO, a 1.7 m diameter telescope for astronomy and aeronomy studies at
wavelengths between 200 and 2000 microns, was installed at the South Pole
during the 1994-1995 Austral summer. The telescope operates continuously
through the Austral winter, and is being used primarily for spectroscopic
studies of neutral atomic carbon and carbon monoxide in the interstellar medium
of the Milky Way and the Magellanic Clouds. The South Pole environment is
unique among observatory sites for unusually low wind speeds, low absolute
humidity, and the consistent clarity of the submillimeter sky. Four heterodyne
receivers, an array receiver, three acousto-optical spectrometers, and an array
spectrometer are installed. A Fabry-Perot spectrometer using a bolometric array
and a Terahertz receiver are in development. Telescope pointing, focus, and
calibration methods as well as the unique working environment and logistical
requirements of the South Pole are described.Comment: 57 pages, 15 figures. Submitted to PAS
Discovery of water vapour in the carbon star V Cygni from observations with Herschel/HIFI
We report the discovery of water vapour toward the carbon star V Cygni. We
have used Herschel's HIFI instrument, in dual beam switch mode, to observe the
1(11) - 0(00) para-water transition at 1113.3430 GHz in the upper sideband of
the Band 4b receiver. The observed spectral line profile is nearly parabolic,
but with a slight asymmetry associated with blueshifted absorption, and the
integrated antenna temperature is 1.69 \pm 0.17 K km/s. This detection of
thermal water vapour emission, carried out as part of a small survey of water
in carbon-rich stars, is only the second such detection toward a carbon-rich
AGB star, the first having been obtained by the Submillimeter Wave Astronomy
Satellite toward IRC+10216. For an assumed ortho-to-para ratio of 3 for water,
the observed line intensity implies a water outflow rate ~ (3 - 6) E-5 Earth
masses per year and a water abundance relative to H2 of ~ (2-5) E-6. This value
is a factor of at least 1E+4 larger than the expected photospheric abundance in
a carbon-rich environment, and - as in IRC+10216 - raises the intriguing
possibility that the observed water is produced by the vapourisation of
orbiting comets or dwarf planets. However, observations of the single line
observed to date do not permit us to place strong constraints upon the spatial
distribution or origin of the observed water, but future observations of
additional transitions will allow us to determine the inner radius of the
H2O-emitting zone, and the H2O ortho-to-para ratio, and thereby to place
important constraints upon the origin of the observed water emission.Comment: Accepted for publication in A&A (HIFI special issue
Photon Dominated Regions in NGC 3603
Aims: We aim at deriving the excitation conditions of the interstellar gas as
well as the local FUV intensities in the molecular cloud surrounding NGC 3603
to get a coherent picture of how the gas is energized by the central stars.
Methods: The NANTEN2-4m submillimeter antenna is used to map the [CI] 1-0, 2-1
and CO 4-3, 7-6 lines in a 2' x 2' region around the young OB cluster NGC 3603
YC. These data are combined with C18O 2-1 data, HIRES-processed IRAS 60 and 100
micron maps of the FIR continuum, and Spitzer/IRAC maps. Results: The NANTEN2
observations show the presence of two molecular clumps located south-east and
south-west of the cluster and confirm the overall structure already found by
previous CS and C18O observations. We find a slight position offset of the peak
intensity of CO and [CI], and the atomic carbon appears to be further extended
compared to the molecular material. We used the HIRES far-infrared dust data to
derive a map of the FUV field heating the dust. We constrain the FUV field to
values of \chi = 3 - 6 \times 10^3 in units of the Draine field across the
clouds. Approximately 0.2 to 0.3 % of the total FUV energy is re-emitted in the
[CII] 158 {\mu}m cooling line observed by ISO. Applying LTE and escape
probability calculations, we derive temperatures (TMM1 = 43 K, TMM2 = 47 K),
column densities (N(MM1) = 0.9 \times 10^22 cm^-2, N(MM2) = 2.5 \times 10^22
cm^-2) and densities (n(MM1) = 3 \times 10^3 cm^-3, n(MM2) = 10^3 -10^4 cm^-3)
for the two observed molecular clumps MM1 and MM2. Conclusions: The cluster is
strongly interacting with the ambient molecular cloud, governing its structure
and physical conditions. A stability analysis shows the existence of
gravitationally collapsing gas clumps which should lead to star formation.
Embedded IR sources have already been observed in the outskirts of the
molecular cloud and seem to support our conclusions.Comment: 13 pages, 10 figures, accepted for publication by A&
The origin of the [C II] emission in the S140 PDRs - new insights from HIFI
Using Herschel's HIFI instrument we have observed [C II] along a cut through
S140 and high-J transitions of CO and HCO+ at two positions on the cut,
corresponding to the externally irradiated ionization front and the embedded
massive star forming core IRS1. The HIFI data were combined with available
ground-based observations and modeled using the KOSMA-tau model for photon
dominated regions. Here we derive the physical conditions in S140 and in
particular the origin of [C II] emission around IRS1. We identify three
distinct regions of [C II] emission from the cut, one close to the embedded
source IRS1, one associated with the ionization front and one further into the
cloud. The line emission can be understood in terms of a clumpy model of
photon-dominated regions. At the position of IRS1, we identify at least two
distinct components contributing to the [C II] emission, one of them a small,
hot component, which can possibly be identified with the irradiated outflow
walls. This is consistent with the fact that the [C II] peak at IRS1 coincides
with shocked H2 emission at the edges of the outflow cavity. We note that
previously available observations of IRS1 can be well reproduced by a
single-component KOSMA-tau model. Thus it is HIFI's unprecedented spatial and
spectral resolution, as well as its sensitivity which has allowed us to uncover
an additional hot gas component in the S140 region.Comment: accepted for publication in Astronomy and Astrophysics (HIFI special
issue
Excitation and Abundance of C3 in star forming cores:Herschel/HIFI observations of the sight-lines to W31C and W49N
We present spectrally resolved observations of triatomic carbon (C3) in
several ro-vibrational transitions between the vibrational ground state and the
low-energy nu2 bending mode at frequencies between 1654-1897 GHz along the
sight-lines to the submillimeter continuum sources W31C and W49N, using
Herschel's HIFI instrument. We detect C3 in absorption arising from the warm
envelope surrounding the hot core, as indicated by the velocity peak position
and shape of the line profile. The sensitivity does not allow to detect C3
absorption due to diffuse foreground clouds. From the column densities of the
rotational levels in the vibrational ground state probed by the absorption we
derive a rotation temperature (T_rot) of ~50--70 K, which is a good measure of
the kinetic temperature of the absorbing gas, as radiative transitions within
the vibrational ground state are forbidden. It is also in good agreement with
the dust temperatures for W31C and W49N. Applying the partition function
correction based on the derived T_rot, we get column densities N(C3)
~7-9x10^{14} cm^{-2} and abundance x(C3)~10^{-8} with respect to H2. For W31C,
using a radiative transfer model including far-infrared pumping by the dust
continuum and a temperature gradient within the source along the line of sight
we find that a model with x(C3)=10^{-8}, T_kin=30-50 K, N(C3)=1.5 10^{15}
cm^{-2} fits the observations reasonably well and provides parameters in very
good agreement with the simple excitation analysis.Comment: Accepted for publication in Astronomy and Astrophysics (HIFI first
results issue
HERSCHEL-HIFI spectroscopy of the intermediate mass protostar NGC7129 FIRS 2
HERSCHEL-HIFI observations of water from the intermediate mass protostar
NGC7129 FIRS 2 provide a powerful diagnostic of the physical conditions in this
star formation environment. Six spectral settings, covering four H216O and two
H218O lines, were observed and all but one H218O line were detected. The four
H2 16 O lines discussed here share a similar morphology: a narrower, \approx 6
km/s, component centered slightly redward of the systemic velocity of NGC7129
FIRS 2 and a much broader, \approx 25 km/s component centered blueward and
likely associated with powerful outflows. The narrower components are
consistent with emission from water arising in the envelope around the
intermediate mass protostar, and the abundance of H2O is constrained to \approx
10-7 for the outer envelope. Additionally, the presence of a narrow
self-absorption component for the lowest energy lines is likely due to
self-absorption from colder water in the outer envelope. The broader component,
where the H2O/CO relative abundance is found to be \approx 0.2, appears to be
tracing the same energetic region that produces strong CO emission at high J.Comment: 6 pages, 4 figures, accepted by A&
Hydrides in Young Stellar Objects: Radiation tracers in a protostar-disk-outflow system
Context: Hydrides of the most abundant heavier elements are fundamental
molecules in cosmic chemistry. Some of them trace gas irradiated by UV or
X-rays. Aims: We explore the abundances of major hydrides in W3 IRS5, a
prototypical region of high-mass star formation. Methods: W3 IRS5 was observed
by HIFI on the Herschel Space Observatory with deep integration (about 2500 s)
in 8 spectral regions. Results: The target lines including CH, NH, H3O+, and
the new molecules SH+, H2O+, and OH+ are detected. The H2O+ and OH+ J=1-0 lines
are found mostly in absorption, but also appear to exhibit weak emission
(P-Cyg-like). Emission requires high density, thus originates most likely near
the protostar. This is corroborated by the absence of line shifts relative to
the young stellar object (YSO). In addition, H2O+ and OH+ also contain strong
absorption components at a velocity shifted relative to W3 IRS5, which are
attributed to foreground clouds. Conclusions: The molecular column densities
derived from observations correlate well with the predictions of a model that
assumes the main emission region is in outflow walls, heated and irradiated by
protostellar UV radiation.Comment: Astronomy and Astrophysics Letters, in pres
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