CS Intensity Research Articles

NEATH − III. A molecular line survey of a simulated star-forming cloud

ABSTRACT We present synthetic line observations of a simulated molecular cloud, utilizing a self-consistent treatment of the dynamics and time-dependent chemical evolution. We investigate line emission from the three most common CO isotopologues (12CO, 13CO, C18O) and six supposed tracers of dense gas (NH3, HCN, N2H+, HCO+, CS, HNC). Our simulation produces a range of line intensities consistent with that observed in real molecular clouds. The HCN-to-CO intensity ratio is relatively invariant with column density, making HCN (and chemically similar species such as CS) a poor tracer of high-density material in the cloud. The ratio of N2H+ to HCN or CO, on the other hand, is highly selective of regions with densities above $10^{22} \, {\rm cm}^{-2}$, and the N2H+ line is a very good tracer of the dynamics of high volume density ($\gt 10^4 \, {\rm cm}^{-3}$) material. Focusing on cores formed within the simulated cloud, we find good agreement with the line intensities of an observational sample of prestellar cores, including reproducing observed CS line intensities with an undepleted elemental abundance of sulphur. However, agreement between cores formed in the simulation, and models of isolated cores which have otherwise-comparable properties, is poor. The formation from and interaction with the large-scale environment has a significant impact on the line emission properties of the cores, making isolated models unsuitable for interpreting observational data.

Exploiting bifunctional 3D-Printed geopolymers for efficient cesium removal and immobilization: An approach for hazardous waste management

3D-printed geopolymer lattices (3DGPLs) have recently been considered as promising candidates for hazardous waste management due to their low cost, porous nature, and excellent environmental stability. However, the ion adsorption capacity influenced by usage conditions such as multi-ion systems and radiation remains largely unexplored. Furthermore, effective strategies to immobilize adsorbed ions for long-term disposal are still lacking. This work tackles these questions by studying the Cs+ adsorption and immobilization properties of 3DGPLs in the presence of competing ions and gamma-ray radiation. Our results reveal the inhibitory intensity of Cs+ adsorption capacity by five common metal cations in seawater, ranked in the following order: Na+ > K+ > Ca2+ > Mg2+ > Sr2+. After exposure to different doses of gamma-ray radiation, the Cs+ adsorption capacity of 3DGPLs shows no significant change, demonstrating their outstanding radiation resistance. By encapsulating the Cs-containing 3DGPL with a homologous GP coating, the Cs+ immobilization rate reaches 98.545% after leaching in NaCl solution at 60 °C for 5 days. The already-high Cs+ immobilization rate can be further increased to 99.228% by sintering treatment due to the densification effect. This study not only provides microscopic insights into the adsorption of hazardous ions by 3DGPLs under usage conditions, but also offers a feasible approach to prevent the leakage of loaded ions through GP coating technology.

Enhanced luminescence stability of high-entropy dual-phase Cs(Pb1/5Mn1/5Ni1/5Zn1/5Cd1/5)Br3/Cs(Pb1/5Mn1/5Ni1/5Zn1/5Cd1/5)2Br5 perovskite nanocrystals coated with SiO2 and EVA

All-inorganic halide perovskite nanocrystals (NCs) have attracted much attention in many fields. However, the poor stability of NCs and the toxicity of Pb have greatly hindered their practical applications. Reducing the proportion of Pb with the concept of high-entropy and coating NCs with an outer layer have been regarded as effective strategies to solve the problems. Herein, We have successfully synthesized the all-inorganic high-entropy dual-phase Cs(Pb1/5Mn1/5Ni1/5Zn1/5Cd1/5)Br3/Cs(Pb1/5Mn1/5Ni1/5Zn1/5Cd1/5)2Br5(Cs‘B’Br3/Cs‘B’2Br5) perovskite NCs with good luminescence properties by a high-energy ball milling method; On the basis of which, Cs‘B’Br3/Cs‘B2’Br5 NCs are coated with SiO2 and EVA resin. Due to the amorphous SiO2 protection, the Cs‘B’Br3/Cs‘B2’Br5@SiO2 NCs maintained 93% of their emission intensity after 90 days compared to their uncoated counterparts. The PL intensity of Cs‘B’Br3/Cs‘B2’Br5 NCs /EVA was significantly enhanced by a factor of 4.7 for compared to the uncoated NCs. In addition, the PL emission intensity of the Cs‘B’Br3/Cs‘B2’Br5 NCs /EVA remained 93.7% after 90 days, and the emission peak intensity remained approximately 63% after 8 h of placement in an enclosed environment at 80% humidity through the dense polymer chains and the hydrophobic nature of the film. Finally, the film could expand its application prospects in the field of flexible device.

Tunable dual-emission in Sb3+, Mn2+ codoped rare-earth based Cs2NaYCl6 nanocrystals and its LEDs applications

Lead-free perovskites are a new type of luminescent material with non-toxic, stability and excellent photoelectric properties, which have great application in the field of photoelectric detection, solar cells, bio-imaging, etc. Here, we reported a new kind of uniform spherical rare-earth based double perovskite Cs 2 NaYCl 6 nanocrystals (NCs) as versatile hosts to accommodate ionic dopants for improving photoelectric properties especially the luminescent properties. In contrast to the low quantum yield of only 5.62%, the luminescent intensity of Cs 2 NaYCl 6 NCs can be impressively enhanced via doping Sb 3+ and Mn 2+ ions in the rare earth-based double perovskite lattices. For the Sb 3+ -doping, the photoluminescence quantum yield (PLQY) increases from 5.62% to 22.48%. On this basis, the luminescence colors can be tuned from blue to white and red via Mn 2+ ions doping and the maximum PLQY can be further improved to 38.66%. Finally, the Sb 3+ , Sb 3+ /Mn 2+ ions doped Cs 2 NaYCl 6 NCs based blue, red and white LEDs were explored, which indicates that these are potential materials in multicolor LEDs applications.

Single silica-coated Mn-doped CsPbCl3 perovskite quantum dots with enhanced stability and excellent optical properties

Halide perovskite quantum dots (QDs) have been considered to be a potential emitting materials for illumination and display applications. Unfortunately, the toxicity and poor stability can greatly limit their practical application. Herein, the Mn2+-doped CsPbCl3 and SiO2-coated Cs(Pb,Mn)Cl3 perovskite QDs have been developed to solve the tricky problem without affecting their optical properties. Firstly, the mono-dispersed pure CsPbCl3 perovskite QDs with cubic morphologies are prepared by using a modified hot-injection method, as a control group. Next, the low-Pb content Cs(Pb,Mn)Cl3 perovskite QDs with distinctive dual emission peaks has been successfully obtained, including the CsPbCl3 host emission and the Mn2+ emission. Based on this, a new strategy for synthesizing single Cs(Pb,Mn)Cl3@SiO2 core-shell QDs with their initial cubic morphology and optical properties has been developed, which using the Cs(Pb,Mn)Cl3 nanoparticles as a precursor and choosing the APTES as the surface ligand. Photo-stability tests indicate that the Cs(Pb,Mn)Cl3 and Cs(Pb,Mn)Cl3@SiO2 perovskite QDs are markedly more stable than the pure CsPbCl3 QDs, indicating that the crystal engineering and host packaging are all effective way to improve the stability. Meanwhile, the PL intensity of Cs(Pb,Mn)Cl3@SiO2 dispersed in a mixed solution of toluene and water can retained 63% of the initial value even after 14 h, which are much higher than Cs(Pb,Mn)Cl3 (31%). Therefore, the Cs(Pb,Mn)Cl3 after SiO2 coating is the more effective way to improve stability than that of the Mn2+ doping. This work not only provides a simple and reliable synthesis way to synthesize the single core-shell particles, which can be suitable for other perovskite systems, but also compares the two methods of the crystal engineering and the host packaging to improve the stability of perovskite QDs for practical application.

Magnetic Fields in Massive Star-forming Regions (MagMaR). II. Tomography through Dust and Molecular Line Polarization in NGC 6334I(N)

Abstract Here, we report ALMA detections of polarized emission from dust, CS(J = 5 → 4), and C33S(J = 5 → 4) toward the high-mass star-forming region NGC 6334I(N). A clear “hourglass” magnetic field morphology was inferred from the polarized dust emission, which is also directly seen from the polarized CS emission across velocity, where the polarization appears to be parallel to the field. By considering previous findings, the field retains a pinched shape that can be traced to clump length scales from the envelope scales traced by ALMA, suggesting that the field is dynamically important across multiple length scales in this region. The CS total intensity emission is found to be optically thick (τ CS = 32 ± 12) while the C33S emission appears to be optically thin ( τ C 33 S = 0.1 ± 0.01 ). This suggests that sources of anisotropy other than large velocity gradients, i.e., anisotropies in the radiation field, are required to explain the polarized emission from CS seen by ALMA. By using four variants of the Davis–Chandrasekhar–Fermi technique and the angle dispersion function methods (ADF), we obtain an average of the estimates for the magnetic field strength on the plane of the sky of B pos = 16 mG from the dust and B pos ∼ 2 mG from the CS emission, where each emission traces different molecular hydrogen number densities. This effectively enables a tomographic view of the magnetic field within a single ALMA observation.

Effect of stimulus orientation and intensity on short-interval intracortical inhibition (SICI) and facilitation (SICF): A multi-channel transcranial magnetic stimulation study.

Besides stimulus intensities and interstimulus intervals (ISI), the electric field (E-field) orientation is known to affect both short-interval intracortical inhibition (SICI) and facilitation (SICF) in paired-pulse transcranial magnetic stimulation (TMS). However, it has yet to be established how distinct orientations of the conditioning (CS) and test stimuli (TS) affect the SICI and SICF generation. With the use of a multi-channel TMS transducer that provides electronic control of the stimulus orientation and intensity, we aimed to investigate how changes in the CS and TS orientation affect the strength of SICI and SICF. We hypothesized that the CS orientation would play a major role for SICF than for SICI, whereas the CS intensity would be more critical for SICI than for SICF. In eight healthy subjects, we tested two ISIs (1.5 and 2.7 ms), two CS and TS orientations (anteromedial (AM) and posteromedial (PM)), and four CS intensities (50, 70, 90, and 110% of the resting motor threshold (RMT)). The TS intensity was fixed at 110% RMT. The intensities were adjusted to the corresponding RMT in the AM and PM orientations. SICI and SICF were observed in all tested CS and TS orientations. SICI depended on the CS intensity in a U-shaped manner in any combination of the CS and TS orientations. With 70% and 90% RMT CS intensities, stronger PM-oriented CS induced stronger inhibition than weaker AM-oriented CS. Similar SICF was observed for any CS orientation. Neither SICI nor SICF depended on the TS orientation. We demonstrated that SICI and SICF could be elicited by the CS perpendicular to the TS, which indicates that these stimuli affected either overlapping or strongly connected neuronal populations. We concluded that SICI is primarily sensitive to the CS intensity and that CS intensity adjustment resulted in similar SICF for different CS orientations.

A Thermodynamic Perspective on Steady-State Tropical Cyclones

AbstractTheories for the maximum intensity of tropical cyclones (TCs) assume steady state. However, many TCs in simulations that run for tens of days tend to decay considerably from an early steady state in the core (CS), before stabilizing at a final equilibrium steady state (ES). This decay raises the question of whether CS or ES should be used as a comparison to the maximum intensity theories. To understand the differences between CS and ES, we investigate why TCs decay and attempt to simulate a TC with steady intensity over a 100-day period. Using the axisymmetric Cloud Model 1, we find that the CS TC decay is due to a large-scale drying of the subsidence region. Such a drying is very pronounced in axisymmetric models because shallow-to-midlevel convection is not represented accurately enough to moisten air in the subsidence region. Simulations with an added moisture relaxation term in the subsidence region and dry cyclones without any moisture both remain in a steady state for over 100 days, without decaying appreciably after the spinup period. These simulations indicate that the decay in TC simulations is due to the irreversible removal of precipitation combined with the lack of a moistening mechanism in the subsidence region. Once either of these conditions is removed, the decay disappears and the CS and ES intensities become essentially equivalent.

SICI during changing brain states: Differences in methodology can lead to different conclusions

BackgroundShort-latency intracortical inhibition (SICI) is extensively used to probe GABAergic inhibitory mechanisms in M1. Task-related changes in SICI are presumed to reflect changes in the central excitability of GABAergic pathways. Usually, the level of SICI is evaluated using a single intensity of conditioning stimulus so that inhibition can be compared in different brain states. ObjectiveHere, we show that this approach may sometimes be inadequate since distinct conclusions can be drawn if a different CS intensity is used. MethodsWe measured SICI using a range of CS intensities at rest and during a warned simple reaction time task. ConclusionsOur results show that SICI changes that occurred during the task could be either larger or smaller than at rest depending on the intensity of the CS. These findings indicate that careful interpretation of results are needed when a single intensity of CS is used to measure task-related physiological changes.

Conditioned pain modulation is affected by occlusion cuff conditioning stimulus intensity, but not duration.

Various conditioned pain modulation (CPM) methodologies have been used to investigate diffuse noxious inhibitory control pain mechanisms in healthy and clinical populations. Occlusion cuff parameters have been poorly studied. We aimed to investigate whether occlusion cuff intensity and/or duration influenced CPM magnitudes. We also investigated the role of physical activity levels on CPM magnitude. Two studies were performed to investigate the role of intensity and duration of occlusion cuff conditioning stimulus on test stimulus (tibialis anterior pressure pain thresholds). In Study 1, conditioning stimulus intensity of 2/10 or 5/10 (duration <20s) was evaluated using a paired-samples t-test. In Study 2, duration of 2/10 conditioning stimulus was 3min. One-way repeated-measures ANOVA was used to investigate the effect of time (0, 1, 2 and 3min) on CPM magnitude. In Study 1, 27 healthy volunteers (mean±SD: 24.9years (±4.5); eight female) demonstrated that an occlusion cuff applied to the upper arm eliciting 5/10 local pain resulted in a significant (mean±SD: 17%±46%) increase in CPM magnitude, when compared to 2/10 intensity (-3%±38%, p=0.026), whereas in Study 2, 25 healthy volunteers (22.5years (±2.7); 13 female) demonstrated that 3min of 2/10 CS intensity did not result in a significant change in CPM (p=0.21). There was no significant relationship between physical activity levels and CPM in either study (p>0.22). This study demonstrated that an occlusion cuff of 5/10 conditioning stimulus intensity, when compared to 2/10, significantly increased CPM magnitude. Maintaining 2/10 conditioning stimulus for 3min did not increase CPM magnitude. Dysfunctional conditioned pain modulation (CPM) has been associated with poor health outcomes. Various factors can influence CPM outcomes. The role of occlusion cuff conditioning stimulus intensity and duration has not been previously investigated. Intensity (5/10), but not duration of lower intensity (2/10) conditioning stimulus, affects CPM magnitude.

Sonoluminescence Spectroscopy as a Promising New Analytical Method

The sonoluminescence intensity of Cs, Ru, K, Na, Li, Sr, In, Ga, Ca, Th, Cr, Pb, Mn, Ag, and Mg salts in aqueous solutions of various concentrations was investigated as a function of ultrasound frequency and intensity. Techniques for the determination of these elements in solutions of table salt and their own salts were developed. It was shown that the proposed analytical technique gave results at high concentrations with better metrological characteristics than atomic-absorption spectroscopy because the samples were not diluted.

Preparation and Characterization of Cement-TiO2 Composites

Titanium dioxide (TiO2) is the most widely used photocatalyst because of its high photocatalytic activity and reasonably low cost. Moreover, TiO2 has strong chemical stability in a large variety of environmental conditions. The combination of TiO2 with cementatious materials has been widely investigated, and the effects of the TiO2 contents (10-40% by weight) were studied in this research. The crystalline structures and chemical compositions were analyzed using x-ray diffraction (XRD) and energy dispersive x-ray spectroscopy (EDS), respectively. Moreover, its microstructure was investigated by scanning electron microscopy (SEM). It was found that the intensity of CS and CH decreased with an increase in the TiO2 powder content. This was because when adding more TiO2 powder to the composite system, more water was needed to add to the hydration reaction.

SERS characterization of imidazole ring terminated self-assembled monolayer formed from lipoic acid histamide on silver electrode

Structure of self-assembled monolayer (SAM) of lipoic acid histamide derivative (LAH), which contains a disulfide group, adsorbed at silver electrode was studied in situ in buffered (pH 8.0) aqueous solution by surface enhanced Raman spectroscopy (SERS) and density functional theory (DFT) calculations. Contrary to LAH in solution, the tautomer-II (N3H protonated) form of imidazole ring was found to be dominant in the adsorbed state. The low frequency AgS stretching band was clearly detected near 235cm−1 at −0.60V electrode potential. Slight downshift (∼4cm−1) without noticeable changes in intensity was observed for this mode at −0.90V potential. Theoretical modeling of interaction of lipoic acid derivative with cluster of eight Ag atoms has confirmed the origin of 235cm−1 band to ν(AgS) vibrational mode. Two SERS bands observed at 606 and 641cm−1 have been assigned to predicted by calculations CS in-phase and out-of-phase vibrational modes, respectively. The in-phase CS stretching vibration exhibited unusually large frequency downshift (60cm−1) because of involvement of 1,2-dithiolane ring sulfur atoms in covalent bonding with Ag surface. Relatively low wavenumber of amide-I band (1636cm−1) revealed strong hydrogen bonding interaction of amide group in the monolayer. Reorientation of adsorbate to more parallel configuration with respect to the electrode surface at more negative potentials was proposed based on changes in intensity of in-phase CS stretching band and appearance of soft CH stretching mode near 2836cm−1 in potential-difference spectrum indicating interaction of methylene groups with electrode surface at sufficiently negative electrode potentials.

Short-interval intracortical inhibition with incomplete spinal cord injury

Objective Short-interval intracortical inhibition (SICI) in leg and hand muscles was characterized in individuals with incomplete spinal cord injury (SCI) to understand how such inhibition limits corticospinal drive after spinal insult. Methods We compared SICI during a voluntary contraction in 16 SCI and 14 control subjects, the latter group tested over a larger range of conditioning and test stimulus (CS and TS) intensities to best match the SCI data. Results The average peak SICI in the tibialis anterior muscle was typically 3–4 times lower in the SCI subjects compared to controls. When matched for absolute TS intensity, in terms of maximum stimulator output, both U-shaped SICI recruitment curves were produced by similar CS intensities. SICI in the first dorsal interosseous muscle of the hand tended to be larger than in the ankle flexor. Conclusions Incomplete SCI reduces SICI compared to controls, but the absolute CS intensities that produce the U-shaped SICI recruitment curves are unchanged. Significance These findings suggest that although the relative excitability profile of cortical SICI networks is unchanged after SCI, the effective inhibition of corticospinal tract output by these neurons is reduced.

Energy spectra of sputtered positive ions under Cs + bombardment

The emission-energy spectra of atomic and molecular secondary ions sputtered from various metals and semiconductors (Al, Cu, In, Si, InP, and InSb) under 5.5-keV Cs + irradiation were investigated. The emitted ions were detected in a high-sensitivity double-focusing secondary-ion mass spectrometer. Specifically, the energy distributions of Cs +, Cs 2 + , MCs +, and M + ions (where M designates one of the target elements) were recorded for emission energies E ⩽ 125 eV. All ion species exhibit a peak at low energy ( E < 5 eV), but differ significantly in the respective fall-off to high emission energies. The influence of the oxygen partial pressure in the vicinity of the sputtered surface on the energy spectra was examined for Cs + ions emitted from Si. With an increase of the ratio r of the O 2 flux to the Cs + flux, the spectra shift to higher emission-energy values, with the total shift amounting to ∼0.45 eV at a value of r ∼ 3.3. Concurrently, the intensity of Cs + increases by ∼30%. The measured emission distributions of Cs + ions from different samples were compared with the predictions of the electron-tunneling model of secondary-ion formation. It is found that the experimental spectra can be reproduced quite well when employing specific sets of parameters in that theoretical concept. The possible limitations of such a comparison are discussed.

Calculations of rovibrational energies and dipole transition intensities for polyatomic molecules using MULTIMODE

We report rigorous calculations of rovibrational energies and dipole transition intensities for three molecules using a new version of the code MULTIMODE. The key features of this code which permit, for the first time, such calculations for moderately sized but otherwise general polyatomic molecules are briefly described. Calculations for the triatomic molecule BF(2) are done to validate the code. New calculations for H(2)CO and H(2)CS are reported; these make use of semiempirical potentials but ab initio dipole moment surfaces. The new dipole surface for H(2)CO is a full-dimensional fit to the dipole moment obtained with the coupled-cluster with single and double excitations and a perturbative treatment of triple excitations method with the augmented correlation consistent triple zeta basis set. Detailed comparisons are made with experimental results from a fit to relative data for H(2)CS and absolute intensities from the HITRAN database for H(2)CO.

The interaction of Purkinje cell and Inhibitory Interneuron plasticity during classical conditioning

Event Abstract Back to Event The interaction of Purkinje cell and Inhibitory Interneuron plasticity during classical conditioning Decades of experimental work using the the eye-blink conditioning paradigm points to the Cerebellar Cortex (CC) as the locus of the motor conditioning engram. It is in the cerebellar cortex where a memory trace is formed that allows both to associate Conditioning (CS) and Unconditioned Stimulus (US) and to elicit an adaptively timed Conditioned Response (CR). Single cell recordings show that the evolution of the firing rate of a Purkinje (PU) cell during the CS-US period provides a substrate for such learning (Jirenhed et al., 2007). Classical computational theories of the Cerebellum (like the Marr-Albus-Ito model) predicted that the mechanism responsible for motor learning was plasticity at the parallel fiber to PU (pf-PU) synapse. However in vitro and in vivo studies have reported multiple loci of plasticity in the CC among them plasticity at the parallel fibers to Inhibitory Interneuron (pf-II) synapse (Jörntell, & Ekerot, 2002). This site of plasticity is of particular interest because it is inversely related to the synaptic dynamics of the pf-PU synapse: whenever the pf-PU synapse undergoes LTD the pf-II undergoes LTP, and vice versa. Hence, this suggests that the engram is not restricted to the parallel fiber Purkinje cell synapse only. A particular challenge for models that exclusive rely on the plasticity at pf-PU synapses is that they have difficulty to explain results that have shown that increasing CS intensity shortens the latency of already acquired CRs (Svensson et al, 1997). We hypothesize that the inclusion of the active role of the Inhibitory Interneurons (II) in learning can account for this CS intensity effect. We have implemented a biologically constrained model aimed at reproducing the learning process of a single Purkinje cell, in such a way that it will respond to presentations of a CS with an adaptively timed pause. In previous work we demonstrated that having plasticity at the pf-PU was sufficient to achieve this goal provided the cortico-nuclear-olivary negative feedback loop was included (Verschure and Mintz, 2000; Hofstötter et al., 2002). Now, we have extended this model and also included plasticity at the pf-II synapse in order to test its computational implications. Our results confirm that potentiation of the II can account for the CS intensity effect. Our model also predicts that if these two plasticity processes coexist it should be possible to identify different components in the dynamics of the acquisition/extinction processes at the level of single Purkinje cells. Although two components have already been founded in behavioral data (Ivarsson & Svensson, 2000) a confirmation of this prediction could only be obtained by analyzing the responses of single Purkinje cells in such experiments.

Intracortical modulation of cortical‐bulbar responses for the masseter muscle

Short interval intracortical inhibition (SICI) and intracortical facilitation (ICF) were evaluated in the masseter muscles of 12 subjects and the cortical silent period (SP) in nine subjects. Motor evoked potentials (MEPs) were recorded from contralateral (cMM) and ipsilateral (iMM) masseters, activated at 10% of maximal voluntary contraction (MVC). Interstimulus intervals (ISIs) were 2 and 3 ms for SICI, 10 and 15 ms for ICF. TMS of the left masseteric cortex induced MEPs that were larger in the cMM than the iMM; stimulation of right masseteric cortex produced a similar asymmetry in response amplitude. SICI was only observed using a CS intensity of 70% AMT and was equal in both cMM and iMM. SICI was stronger at higher TS intensities, was abolished by muscle activation greater than 10% MVC, and was unaffected by coil orientation changes. Control experiments confirmed that SICI was not contaminated by any inhibitory peripheral reflexes. However, ICF could not be obtained because it was masked by bilateral reflex depression of masseter EMG caused by auditory input from the coil discharge. The SP was bilateral and symmetric; its duration ranged from 35 to 70 ms depending on TS intensity and coil orientation. We conclude that SICI is present in the cortical representation of masseter muscles. The similarity of SICI in cMM and iMM suggests either that a single pool of inhibitory interneurons controls ipsi- and contralateral corticotrigeminal projections or that inhibition is directed to bilaterally projecting corticotrigeminal fibres. Finally, the corticotrigeminal projection seems to be weakly influenced by inhibitory interneurons mediating the cortical SP.

A multi-transition molecular line study of candidate massive young stellar objects associated with methanol masers

We characterize the molecular environment of candidate massive young stellar objects (MYSOs) signposted by methanol masers. Single pixel observations of 10 transitions of HCO^+, CO and CS isotopomers were carried out, using the IRAM 30m telescope. We studied a sample of 28 targets for which the 6.7GHz maser emission positions are known with a sub-arcsecond accuracy. The systemic velocity inferred from the optically thin lines agrees within 3km/s with the central velocity of the maser emission for most of the sources. About 64% of the sources show line wings in one or more transitions of CO, HCO^+ and CS species, indicating the presence of molecular outflows. Comparison of the widths of line wings and methanol maser emission suggests that the 6.7GHz maser line traces the environment of MYSO of various kinematic regimes. Therefore conditions conducive for the methanol maser can exist in the inner parts of molecular clouds or circumstellar discs as well as in the outer parts associated with molecular outflows. Calculations of the physical conditions based on the CO and HCO^+ lines and the CS line intensity ratios refine the input parameters for maser models.

Towards constraining the environments of methanol masers

AbstractObservations of 10 transitions of HCO+, CO and CS isotopomers were taken with the IRAM 30 m telescope for a sample of 28 methanol maser sources detected in the Torun unbiased survey of the galactic plane. About 64% of the sources show line wings in one or more transitions, indicating the presence of molecular outflows. Two sources show evidence for infall motion. Comparison of the widths of line wings and methanol maser emission suggests that the 6.7 GHz maser line traces the environment of massive young stellar objects of various kinematic regimes. Calculations based on the CO and HCO+ lines and the CS line intensity ratios refine the physical parameters. Specifically, a gas density of &lt;107 cm−3 is sufficient for strong maser emission and a high methanol fractional abundance (&gt;5×10−7) is required.