452 research outputs found
Odin observations of ammonia in the Sgr A +50 km/s Cloud and Circumnuclear Disk
Context. The Odin satellite is now into its sixteenth year of operation, much
surpassing its design life of two years. One of the sources which Odin has
observed in great detail is the Sgr A Complex in the centre of the Milky Way.
Aims. To study the presence of NH3 in the Galactic Centre and spiral arms.
Methods. Recently, Odin has made complementary observations of the 572 GHz NH3
line towards the Sgr A +50 km/s Cloud and Circumnuclear Disk (CND). Results.
Significant NH3 emission has been observed in both the +50 km/s Cloud and the
CND. Clear NH3 absorption has also been detected in many of the spiral arm
features along the line of sight from the Sun to the core of our Galaxy.
Conclusions. The very large velocity width (80 km/s) of the NH3 emission
associated with the shock region in the southwestern part of the CND may
suggest a formation/desorption scenario similar to that of gas-phase H2O in
shocks/outflows.Comment: 5 pages, 3 figures, 3 table
Organic molecules in the spectral line survey of Orion KL with the Odin Satellite from 486492 GHz and 541577 GHz
Proceedings of the International Astronomical Union, 2008, v. 4 n. S251, p. 29-30A spectral line survey of Orion KL has been performed over the frequency range of 486492 GHz and 541577 GHz using the Odin satellite. Over 1000 lines have been identified from 40 different molecular species, including several organic compounds such as methyl cyanide (CH3CN), methanol (CH3OH, 13CH3OH), and dimethyl ether (CH3OCH3). © 2008 International Astronomical Union.published_or_final_versio
Herschel and Odin observations of H2O, CO, CH, CH+, and NII in the barred spiral galaxy NGC 1365. Bar-induced activity in the outer and inner circumnuclear tori
The Odin satellite is now into its twentieth year of operation, much
surpassing its design life of two years. One of its major pursuits was the
search for and study of H2O in the Solar System and the Milky Way galaxy.
Herschel has observed the central region of NGC 1365 in two positions, and both
its SPIRE and PACS observations are available in the Herschel Science Archive.
Herschel PACS images have been produced of the 70 and 160 micron infrared
emission from the whole galaxy, and also of the cold dust distribution as
obtained from the ratio of the 160 to 70 micron images. The Herschel SPIRE
observations have been used to produce maps of the 557 GHz o-H2O, 752 GHz
p-H2O, 691 GHz CO(6-5), 1037 GHz CO(9-8), 537 GHz CH, 835 GHz CH+, and the 1461
GHz NII lines; however, these observations have no effective velocity
resolution. Odin has recently observed the 557 GHz o-H2O ground state line in
the central region with high (5 km/s) spectral resolution. The emission and
absorption of H2O at 557 GHz, with a velocity resolution of 5 km/s, has been
marginally detected in NGC 1365 with Odin. The H2O is predominantly located in
a shocked 15" (1.3 kpc) region near some central compact radio sources and
hot-spot HII regions, close to the northeast component of the molecular torus
surrounding the nucleus. An analysis of the H2O line intensities and velocities
indicates that a shock-region is located here. This is corroborated by a
statistical image deconvolution of our SEST CO(3-2) observations, yielding 5"
resolution, and a study of our VLA HI absorption observations. Additionally, an
enticing 20" HI ridge is found to extend south-southeast from the nucleus,
coinciding in position with the southern edge of an OIII outflow cone,
emanating from the nucleus. The molecular chemistry of the shocked central
region is analyzed with special emphasis on the CO, H2O and CH, CH+ results.Comment: 25 pages, 11 figure
On the accretion process in a high-mass star forming region - A multitransitional THz Herschel-HIFI study of ammonia toward G34.26+0.15
[Abridged] Our aim is to explore the gas dynamics and the accretion process
in the early phase of high-mass star formation. The inward motion of molecular
gas in the massive star forming region G34.26+0.15 is investigated by using
high-resolution profiles of seven transitions of ammonia at THz frequencies
observed with Herschel-HIFI. The shapes and intensities of these lines are
interpreted in terms of radiative transfer models of a spherical, collapsing
molecular envelope. An accelerated Lambda Iteration (ALI) method is used to
compute the models. The seven ammonia lines show mixed absorption and emission
with inverse P-Cygni-type profiles that suggest infall onto the central source.
A trend toward absorption at increasingly higher velocities for higher
excitation transitions is clearly seen in the line profiles. The lines show only very weak emission, so these absorption profiles
can be used directly to analyze the inward motion of the gas. This is the first
time a multitransitional study of spectrally resolved rotational ammonia lines
has been used for this purpose. Broad emission is, in addition, mixed with the
absorption in the ortho-NH line, possibly tracing a molecular
outflow from the star forming region. The best-fitting ALI model reproduces the
continuum fluxes and line profiles, but slightly underpredicts the emission and
absorption depth in the ground-state ortho line . The derived
ortho-to-para ratio is approximately 0.5 throughout the infalling cloud core
similar to recent findings for translucent clouds in sight lines toward W31C
and W49N. We find evidence of two gas components moving inwards toward the
central region with constant velocities: 2.7 and 5.3 kms, relative
to the source systemic velocity. The inferred mass accretion rates derived are
sufficient to overcome the expected radiation pressure from G34.26+0.15.Comment: 20 pages, 18 figures, accepted by A&A 3 October 201
Isotopic ratios of H, C, N, O, and S in comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy)
The apparition of bright comets C/2012 F6 (Lemmon) and C/2014 Q2 (Lovejoy) in
March-April 2013 and January 2015, combined with the improved observational
capabilities of submillimeter facilities, offered an opportunity to carry out
sensitive compositional and isotopic studies of the volatiles in their coma. We
observed comet Lovejoy with the IRAM 30m telescope between 13 and 26 January
2015, and with the Odin submillimeter space observatory on 29 January - 3
February 2015. We detected 22 molecules and several isotopologues. The
HO and HO production rates measured with Odin follow a
periodic pattern with a period of 0.94 days and an amplitude of ~25%. The
inferred isotope ratios in comet Lovejoy are O/O = 499 24
and D/H = 1.4 0.4 in water, S/S = 24.7
3.5 in CS, all compatible with terrestrial values. The ratio
C/C = 109 14 in HCN is marginally higher than terrestrial
and N/N = 145 12 in HCN is half the Earth ratio. Several
upper limits for D/H or 12C/13C in other molecules are reported. From our
observation of HDO in comet C/2014 Q2 (Lovejoy), we report the first D/H ratio
in an Oort Cloud comet that is not larger than the terrestrial value. On the
other hand, the observation of the same HDO line in the other Oort-cloud comet,
C/2012 F6 (Lemmon), suggests a D/H value four times higher. Given the previous
measurements of D/H in cometary water, this illustrates that a diversity in the
D/H ratio and in the chemical composition, is present even within the same
dynamical group of comets, suggesting that current dynamical groups contain
comets formed at very different places or times in the early solar system.Comment: Accepted for publication in Astronomy and Astrophysic
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Specifying evidence-based behavior change techniques to aid smoking cessation in pregnancy
Introduction: Behavioural support aids smoking cessation in pregnancy. However, it remains unclear which component behaviour change techniques (BCTs) contribute to effectiveness, or the extent to which these are applied in practice. This study aimed to examine: i) which BCTs were included in effective behavioural support interventions for pregnant smokers, and ii) the prevalence of use of these BCTs by the English Stop Smoking Services (SSSs).
Methods: From a Cochrane review of smoking cessation behavioural support in pregnancy, seven interventions were identified as effective in that they increased the odds of cessation by at least 50% and differences between intervention and control conditions were statistically significant. BCTs in each intervention were identified using an established taxonomy of BCTs. Thirteen treatment manuals from SSSs were coded for inclusion of BCTs.
Results: Thirty-seven BCTs were identified across trials of behavioural support for pregnant smokers, with an average of eight BCTs, and a range of six to 34 BCTs, per intervention. Eleven BCTs were present in at least two effective interventions [e.g. facilitate goal setting (n=6), advise on social support (n=2), action planning (n=5), provide rewards contingent on successfully stopping smoking (n=4)]. Only 15.4% of treatment manuals from SSSs contained all eleven BCTs; 53.8% contained at least six of them.
Conclusions: Whilst BCTs associated with effective interventions can be identified from systematically reviewed literature, English SSSs appear to use only a limited proportion of these in practice
Electric Field Control of Shallow Donor Impurities in Silicon
We present a tight-binding study of donor impurities in Si, demonstrating the
adequacy of this approach for this problem by comparison with effective mass
theory and experimental results. We consider the response of the system to an
applied electric field: donors near a barrier material and in the presence of
an uniform electric field may undergo two different ionization regimes
according to the distance of the impurity to the Si/barrier interface. We show
that for impurities ~ 5 nm below the barrier, adiabatic ionization is possible
within switching times of the order of one picosecond, while for impurities ~
10 nm or more below the barrier, no adiabatic ionization may be carried out by
an external uniform electric field. Our results are discussed in connection
with proposed Si:P quantum computer architectures.Comment: 18 pages, 6 figures, submitted to PR
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