16,672 research outputs found
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 (7â6) rotational transitions of the isotopes ^(13)CO at 771 GHz and C^(18)O and 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 12â15 K lower values at 60 km. The CO mixing ratio was determined as 980 ± 150 ppm, in agreement with the 900 ppm derived from Herschel/SPIRE observations in November 2009
A tidally interacting disk in the young triple system WL 20?
We present high-resolution λ = 2.7 mm imaging of the close triple pre-main-sequence system WL 20. Compact dust emission with integrated flux density of 12.9 ± 1.3 mJy is associated with two components of the triple system, WL 20W and WL 20S. No emission above a 3 Ï level of 3.9 mJy is detected toward the third component, WL 20E, which lies 3."17 (400 AU) due east in projection from its neighbors. A possibly warped structure of ~0.1 M_â and â€3."2 extent encompasses WL 20W and WL 20S, which have a projected separation of 2."25 (~280 AU) along a north-south axis. This structure is most likely a tidally disrupted disk surrounding WL 20S. New near-infrared spectra of the individual components show a remarkable similarity between the two T Tauri stars of the system: WL 20E has a K7 spectral type (T_eff = 4040 K) with r_K = 0.2, and WL 20W has an M0 spectral type (T_eff = 3800 K) with r_K = 0.2. The spectrum of WL 20S is consistent with that of a source intrinsically similar to WL 20W, with r_K < 0.9, but seen through an A_V = 25 in addition to the A_V = 16.3 to the system as a whole. Taken together, these millimeter and infrared data help explain the peculiar nature of the infrared companion, WL 20S, as resulting from a large enhancement in its dusty, circumstellar environment in relation to its companions
Structure and chemistry of Orion S
We present interferometric observations of the SiO J = 2-1, H^(13)CO^+ J = 1-0, HC_3N J = 11-10, CH_3OH J_K = 2_0-1_0, and SO_2 J(K_pK_0) = 8_(17)-8_(08) transitions along with the λ = 3.1 mm continuum toward the young stellar object Orion S. The HC_3N and H^(13)CO^+ emission trace similar spatial and velocity distributions which are extended and follow the Orion molecular ridge. The SiO emission is more spatially confined, peaking to the west of the λ = 3.1 mm continuum source, while the CH_3OH emission peaks to the southwest. Weak SO_2 emission was detected southeast of the continuum source position. Column densities and fractional abundances are derived for each species at different positions in the region. In general, the molecular abundances near the continuum source are similar to those in the quiescent material near IRc 2, but the abundances decrease toward the continuum source position indicating localized depletions of at least a factor of three. The presence of strong SiO emission with much weaker SO_2 emission is interpreted as resulting from high-velocity shock interactions between the outflow from Orion S and the surrounding cloud. The apparent molecular depletions directly toward Orion S, and the similarity of
abundances between the Orion S region and quiescent ridge material, suggest that Orion S is at an early stage
of chemical evolution, prior to when substantial chemical differentiation occurs
Molecular line survey of Sagittarius B2(M) from 330 to 355 GHz and comparison with Sagittarius B2(N)
We have surveyed molecular line emission from Sgr B2 over the range from 330 to 355 GHz at the position designated Sgr B2(M). This position is prominent in millimeter continuum maps of the region and is associated with a compact H II region, a hot NH_3 core, and sources of H_2O and OH maser emission. We have also obtained observations contrasting the submillimeter molecular emission from Sgr B2(M) and Sgr B2(N), an additional center of activity thought to be a dense protostellar core.
The picture of the interstellar chemistry of these regions which we derive is substantially different from that
determined from previous observations at lower frequencies and with lower spatial resolution. In particular,
molecules such as SO_2 and CH_3OH dominate the submillimeter spectrum to a much greater extent than they do
the low-frequency observations. Much of this difference is due to the higher spatial resolution of the submillimeter
observations, which makes them much more sensitive to emission from compact, dense cores. The millimeter
data were most effective at sampling material in the surrounding lower density regions. The chemistry of the core
sources in Sgr B2 appears similar to that of other dense cores, such as the core of the Orion molecular cloud.
The spectral differences between Sgr B2(M) and Sgr B2(N) primarily relate to differences in excitation and
column density. For most molecular species the northern source (N) has a column density significantly higher
than that found in the middle source (M), often by a factor of about 5. The principal exceptions are the species SO
and SO_2 which seem to be substantially more abundant in the middle source. Generally excitation seems to be
higher in the northern source, suggesting a somewhat higher density core, although there are some departures
indicating that the excitation situation is more complicated. High optical depths in many of the submillimeter transitions systematically bias the interpretation of both column densities and excitation. Many of the millimeter lines may also have high optical depths, particularly those lines arising from the compact core sources
HIFI observations of water in the atmosphere of comet C/2008 Q3 (Garradd)
High-resolution far-infrared and sub-millimetre spectroscopy of water lines is an important tool to understand the physical and chemical properties of cometary atmospheres.We present observations of several rotational ortho- and para-water transitions in comet C/2008 Q3 (Garradd) performed with HIFI on Herschel. These observations have provided the first detection of the 2_(12)â1_(01) (1669 GHz) ortho and 1_(11)â0_(00) (1113 GHz) para transitions of water in a cometary spectrum. In addition, the ground-state transition 1_(10)â1_(01) at 557 GHz is detected and mapped. By detecting several water lines quasi-simultaneously and mapping their emission we can constrain the excitation parameters in the coma. Synthetic line profiles are computed using excitation models which include excitation by collisions, solar infrared radiation, and radiation trapping. We obtain the gas kinetic temperature, constrain the electron density profile, and estimate the coma expansion velocity by analyzing the map and line shapes. We derive water production rates of 1.7â2.8 Ă 10^(28) s^(â1) over the range r_h = 1.83â1.85 AU
Molecular Identification of Eimeria Species in Broiler Chickens in Trinidad, West Indies
Coccidiosis is an intestinal disease of chickens of major economic importance to broiler industries worldwide. Species of coccidia found in chickens include Eimeria acervulina, Eimeria brunetti, Eimeria maxima, Eimeria mitis, Eimeria necatrix, Eimeria praecox, and Eimeria tenella. In recent years, polymerase chain reaction (PCR) has been developed to provide accurate and rapid identification of the seven known Eimeria species of chickens. The aim of this study was to use species-specific real-time PCR (qPCR) to identify which of the seven Eimeria species are present in Trinidad poultry. Seventeen pooled fecal samples were collected from 6 broiler farms (2â5 pens per farm) across Trinidad. Feces were also collected from birds showing clinical signs of coccidiosis in two live bird markets (pluck shops). qPCR revealed the presence of five species of Eimeria (E. acervulina, E. maxima, E. mitis, E. necatrix, and E. tenella), but not E. brunetti or E. praecox. Mixed infections were detected on all broiler farms, and DNA of two highly pathogenic Eimeria species (E. tenella and E. necatrix) was detected in feces taken from clinically sick birds sampled from the two pluck shops
A Line Survey of Orion KL from 325 to 360 GHz
We present a high-sensitivity spectral line survey of the high-mass star-forming region Orion KL in the 325-360 GHz frequency band. The survey was conducted at the Caltech Submillimeter Observatory on Mauna Kea, Hawaii. The sensitivity achieved is typically 0.1-0.5 K and is limited mostly by the sideband separation method utilized. We find 717 resolvable features consisting of 1004 lines, among which 60 are unidentified. The identified lines are due to 34 species and various isotopomers. Most of the unidentified lines are weak, and many of them most likely due to isotopomers or vibrationally or torsionally excited states of known species with unknown line frequencies, but a few reach the 2-5 K level. No new species have been identified, but we were able to strengthen evidence for the identification of ethanol in Orion and found the first nitrogen sulfide line in this source. The molecule dominating the integrated line emission is SO_2, which emits twice the intensity of CO, followed by SO, which is only slightly stronger than CO. In contrast, the largest number of lines is emitted from heavy organic rotors like HCOOCH_3, CH_3CH_2CN, and CH_3OCH_3, but their contribution to the total flux is unimportant. CH_3OH is also very prominent, both in the number of lines and in integrated flux. An interesting detail of this survey is the first detection of vibrationally excited HCN in the v_2 = 2 state, 2000 K above ground. Clearly this is a glimpse into the very inner part of the Orion hot core
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