bluuebunny/crossref_metadata_2025 huggingface dataset:
Single oral doses of (±) 3,4-methylenedioxymethamphetamine (‘Ecstasy’) produce lasting serotonergic deficits in non-human primates: relationship to plasma drug and metabolite concentrations
Authors: Mueller Melanie , Yuan Jie , McCann Una D. , Hatzidimitriou George , Ricaurte George A.
Published: July 2012

Repeated doses of the popular recreational drug methylenedioxymethamphetamine (MDMA, ‘Ecstasy’) are known to produce neurotoxic effects on brain serotonin (5-HT) neurons but it is widely believed that typical single oral doses of MDMA are free of neurotoxic risk. Experimental and therapeutic trials with MDMA in humans are underway. The mechanisms by which MDMA produces neurotoxic effects are not understood but drug metabolites have been implicated. The aim of the present study was to assess the neurotoxic potential of a range of clinically relevant single oral doses of MDMA in a non-human primate species that metabolizes MDMA in a manner similar to humans, the squirrel monkey. A secondary objective was to explore the relationship between plasma MDMA and metabolite concentrations and lasting serotonergic deficits. Single oral doses of MDMA produced lasting dose-related serotonergic neurochemical deficits in the brains of squirrel monkeys. Notably, even the lowest dose of MDMA tested (5.7 mg/kg, estimated to be equivalent to 1.6 mg/kg in humans) produced significant effects in some brain regions. Plasma levels of MDMA engendered by neurotoxic doses of MDMA were on the order of those found in humans. Serotonergic neurochemical markers were inversely correlated with plasma concentrations of MDMA, but not with those of its major metabolites, 3,4-dihydroxymethamphetamine and 4-hydroxy-3-methoxymethamphetamine. These results suggest that single oral doses of MDMA in the range of those used by humans pose a neurotoxic risk and implicate the parent compound (MDMA), rather than one of its metabolites, in MDMA-induced 5-HT neural injury.
Modelling of Cosmic Molecular Masers: Introduction to a Computation Cookbook
Authors: Sobolev Andrej M. , Gray Malcolm D.
Published: July 2012

Numerical modeling of molecular masers is necessary in order to understand their nature and diagnostic capabilities. Model construction requires elaboration of a basic description which allows computation, that is a definition of the parameter space and basic physical relations. Usually, this requires additional thorough studies that can consist of the following stages/parts: relevant molecular spectroscopy and collisional rate coefficients; conditions in and around the masing region (that part of space where population inversion is realized); geometry and size of the masing region (including the question of whether maser spots are discrete clumps or line-of-sight correlations in a much bigger region) and propagation of maser radiation. Output of the maser computer modeling can have the following forms: exploration of parameter space (where do inversions appear in particular maser transitions and their combinations, which parameter values describe a ‘typical’ source, and so on); modeling of individual sources (line flux ratios, spectra, images and their variability); analysis of the pumping mechanism; predictions (new maser transitions, correlations in variability of different maser transitions, and the like). Described schemes (constituents and hierarchy) of the model input and output are based mainly on the experience of the authors and make no claim to be dogmatic.
A detailed trace of the pump for 1720-MHz OH masers in SNRs
Authors: Gray M. D.
Published: July 2012

I have analysed the pumping scheme of 1720-MHz OH masers in great detail.
Maser polarization and magnetic fields
Authors: Vlemmings W. H. T.
Published: July 2012

Maser polarization observations can reveal unique information on the magnetic field strength and structure for a large number of very different astronomical objects. As the different masers for which polarization is measured, such as silicon-monoxide, water, hydroxil and methanol, probe different physical conditions, the masers can even be used to determine for example the relation between magnetic field and density. In particular, maser polarization observations have improved our understanding of the magnetic field strength in, among others, the envelopes around evolved stars, Planetary Nebulae (PNe), massive star forming regions, supernova remnants and megamaser galaxies. This review presents an overview of maser polarization observations and magnetic field determinations of the last several years and discusses some of the theoretical considerations needed for a proper maser polarization analysis.
VLBA SiO maser observations of the OH/IR star OH 44.8-2.3: magnetic field and morphology
Authors: Amiri N. , Vlemmings W. H. T. , Kemball A. J. , van Langevelde H. J.
Published: July 2012

We report on Very Long Baseline Array SiO maser observations of the OH/IR star OH 44.8 - 2.3. The observations show that the maser features form a ring located at a distance of 5.4 AU around the central star. The masers show high fractional linear polarization up to 100%. The polarization vectors are consistent with a dipole field morphology. Additionally, we report a tentative detection of circular polarization of 7% for the brightest maser feature. This indicates a magnetic field of 1.5 ± 0.3 G. The SiO masers and the 1612 MHz OH masers suggest a mildly preferred outflow direction in the circumstellar environment of this star. The observed polarization is consistent with magnetic field structures along the preferred outflow direction. This could indicate the possible role of the magnetic fields in shaping the circumstellar environment of this object.
Linear polarization of hydroxyl masers in circumstellar envelope outer regions
Authors: Wolak P. , Szymczak M. , Gérard E.
Published: July 2012

A recent polarimetric survey of OH masers in a large sample of AGB and post-AGB stars revealed widespread occurrence of polarized features. We made a statistical analysis of the polarization properties of this large data set. We discuss the alignment of polarization position angles between the extreme blue- and red-shifted parts of the 1612 MHz spectrum. The average polarization angle of OH masers from the opposite sides of the envelope agrees within 20° for 80% of the sources in the sample. For two objects monitored over ~6 years the polarization position angle at 1612 MHz is constant within measurement uncertainties: this suggests a stable and a very regular structure of the circumstellar magnetic fields. Alternatively, this could indicate a galactic origin of the field which may be amplified by the stellar wind in the outermost parts of the envelopes.
The variability of cosmic methanol masers in massive star-forming regions
Authors: Maswanganye Jabulani P. , Gaylard Michael J.
Published: July 2012

The methanol masers associated with G35.20-1.74 were monitored at 12178 MHz for four years and 6668 MHz for five years using the 26m Hartebeesthoek telescope. This source showed irregular variability and a single large flare event during the monitoring window.
Masers in star forming regions
Authors: Bartkiewicz Anna , van Langevelde Huib Jan
Published: July 2012

Maser emission plays an important role as a tool in star formation studies. It is widely used for deriving kinematics, as well as the physical conditions of different structures, hidden in the dense environment very close to the young stars, for example associated with the onset of jets and outflows. We will summarize here the recent observational and theoretical progress on this topic since the last maser symposium: the IAU Symposium 242 in Alice Springs.
A Highly-collimated Water Maser Bipolar Outflow in the Cepheus A HW3d Massive Protostellar Object
Authors: Chibueze James O. , Imai Hiroshi , Tafoya Daniel , Omodaka Toshihiro , Kameya Osamu , Hirota Tomoya , Chong Sze-Ning , Torrelles José M.
Published: July 2012

We report the results of multi-epoch very long baseline interferometry (VLBI) water (H2O) maser observations carried out with the VLBI Exploration of Radio Astrometry (VERA) toward the HW3d object within the Cepheus A star-forming region. We measured proper motions of 30 water maser features, tracing a compact bipolar outflow. This outflow is highly collimated, extending through ~400 mas (290 AU), and having a typical proper motion velocity of ~6 mas yr−1 (~21 km s−1). The dynamical timescale of the outflow was estimated to be ~100 years, showing that the outflow is tracing a very early star-formation phase. Our results provide strong support that the HW3d object harbors an internal massive protostar, as previous observations suggested. In addition, we have analyzed Very Large Array (VLA) archive 1.3 cm continuum data of the 1995 and 2006 epochs obtained towards Cepheus A. These results indicate possible different protostars around HW3d and/or strong variability in its radio continuum emission.
High-mass Star Formation in the Regions IRAS 19217+1651 and 23151+5912
Authors: Migenes V. , Rodríguez I. T. , Trinidad M. A.
Published: July 2012

We present and discuss VLA-EVLA high-sensitivity and spatial resolution observations of Water Vapor MASERs and continuum emission towards two sources that have been proposed in the literature to be high-mass star forming regions: IRAS 19217+1651 and 23151+5912. Our results indicate the presence of disks which can confirm that these regions are high-mass star forming regions.
325 GHz Water Masers in Orion Source I
Authors: Niederhofer Florian , Humphreys Elizabeth , Goddi Ciriaco , Greenhill Lincoln J.
Published: July 2012

Radio Source I in the Orion BN/KL region provides the closest example of high mass star formation. It powers a rich ensemble of SiO and H2O masers, and is one of only three star-forming regions known to display SiO maser emission. Previous monitoring of different SiO masers with the VLBA and VLA has enabled the resolution of a compact disk and a protostellar wind at radii <100 AU from Source I, which collimates into a bipolar outflow at radii of 100-1000 AU (see contribution by Greenhill et al., this volume). Source I may provide the best case of disk-mediated accretion and outflow recollimation in massive star formation. Here, we report preliminary results of sub-arcsecond resolution 325 GHz H2O maser observations made with the SMA. We find that 325 GHz H2O masers trace a more collimated portion of the Source I outflow than masers at 22 GHz, but occur at similar radii suggesting similar excitation conditions. A velocity gradient perpendicular to the outflow axis, indicating rotation, supports magneto-centrifugal driving of the flow.
Molecular outflows toward methanol masers: detection techniques and their properties.
Authors: de Villiers Helena M. , Thompson M. A. , Chrysostomou A. , van der Walt D. J.
Published: July 2012

Class II methanol masers are thought to trace the brief phase in the evolution of a massive YSO, where outflows are expected to occur. Molecular line maps of the CO isotopes of a subset of 6.7 GHz sources from the MMB catalogue were observed with the JCMT telescope. Utilising optically thick 12CO, a search was done to detect broadened line wings (initially only on the source G20.08-0.13). The physical parameters of these detected lobes were then calculated.
Masers in evolved star winds
Authors: Richards Anita M. S.
Published: July 2012

This review summarises current observations of masers around evolved stars and models for their location and behaviour, followed by some of the many highlights from the past 5 years. Some of these have been the fruition of long-term monitoring, a vital aspect of study of stars which are both periodically variable and prone to rapid outbursts or transition to a new evolutionary stage. Interferometric imaging of masers provide the highest-resolution probes of the stellar wind, but their exponential amplification and variability means that multiple observations are needed to investigate questions such as what drives the wind from the stellar surface; why does it accelerate slowly over many tens of stellar radii; what causes maser variability. VLBI parallaxes have improved our understanding of individual objects and of Galactic populations. Masers from wide range of binary and post-AGB objects are accessible to sensitive modern instruments, including energetic symbiotic systems. Masers have been detected up to THz frequencies withHerscheland ALMA's ability to resolve a wide range of maser and thermal lines will provide accurate constraints on physical conditions including during dust formation.
Maser emission during post-AGB evolution
Authors: Desmurs J.-F.
Published: July 2012

This contribution reviews recent observational results concerning astronomical masers toward post-AGB objects with a special attention to water fountain sources and the prototypical source OH 231.8+4.2. These sources represent a short transition phase in the evolution between circumstellar envelopes around asymptotic giant branch stars and planetary nebulae. The main masing species are considered and key results are summarized.
Water Fountains in Pre-Planetary Nebulae: The Case of IRAS16342–3814
Authors: Claussen Mark , Sahai Raghvendra , Morris Mark , Rogers Hannah
Published: July 2012

We present a brief review of Very Long Baseline Array (VLBA) observations of water masers in the so-called water fountain pre-planetary nebulae, and report on new VLBA and Very Large Array (VLA) data for the water masers in the prototypical water fountain source IRAS16342–3814, taken approximately monthly in 2008–2009. A new and very strong water maser is found at an LSR velocity of −3 km s−1, which is offset from the central (likely stellar) velocity. The new VLBA observations still show a similar general structure as was observed in 2002, but there are details which are difficult to explain.
Preliminary results on SiO v=3 J=1−0 maser emission from AGB stars
Authors: Desmurs J.-F. , Bujarrabal V. , Lindqvist M. , Alcolea J. , Soria-Ruiz R. , Bergman P.
Published: July 2012

We present the results of SiO maser observations at 43 GHz toward two AGB stars using the VLBA. Our preliminary results on the relative positions of the different J=1–0 SiO masers (v=1,2 and 3) indicate that the current ideas on SiO maser pumping could be wrong at some fundamental level. A deep revision of the SiO pumping models could be necessary.
1612 MHz OH maser monitoring with the Nançay Radio Telescope
Authors: Engels D. , Gérard E. , Hallet N.
Published: July 2012

20 OH/IR stars are monitored in the 1612 MHz OH maser line with the Nançay Radio Telescope. The program started in 2008 with monthly observations of the full sample and will last at least until end of 2012. The aim is the determination of the linear diameter of the circumstellar shell using the phase lag between the light curves of the varying OH maser lines. To use them for distance determinations, angular diameters are obtained by interferometric measurements while the stars pass the maximum of their OH maser flux density variations. The periods of the OH/IR stars monitored are between 425 and >2000 days.
SiO Maser Surveys of Nearby Miras and their Kinematics in the Galaxy
Authors: Deguchi Shuji
Published: July 2012

I review recent developments of SiO maser observations of miras, and discuss their kinematics in the Galaxy. They are deeply related to problems in other fields, such as the noncircular motion of Galactic spiral arms, streaming motions of stars in the solar neighborhood, and the interface between the interstellar and circumstellar medium revealed by Far-IR imaging of some miras, as well as the bar structure of the Galaxy. Recent automated surveys of variable stars in optical bands have increased the number of red variables enormously. Most of these stars were not observed in the radio before because of their blue colors. We have obtained radial velocities of these long-period variables with SiO masers. The longitude-velocity diagrams have revealed interesting deviations of stellar motions from the circular motion of the Galaxy, some of which show spatial motion similar to that of the Hercules group of stars. Important developments of SiO maser observations have been made for symbiotic stars, one of which showed a nova eruption with concurrent γ ray emission in 2010 (V407 Cyg). SiO masers have been monitored for this star after the nova eruption. I summarize the SiO maser observations of individual stars also.
Identification of Class I Methanol Masers with Objects of Near and Mid-Infrared Bands and the Third Version of the Class I Methanol Maser (MMI) Catalog
Authors: Bayandina Olga , Val'tts Irina , Larionov Grigorii
Published: July 2012

An identification has been conducted of class I methanol masers with 1) short-wave infrared objects EGO (extended green objects) - tracer bipolar outflow of matter in young stellar objects, and 2) isolated pre-protostellar gas-dust cores of the interstellar medium which are observed in absorption in the mid-infrared in the Galactic plane. It is shown that more than 50% of class I methanol masers are identified with bipolar outflows, considering the EGO as bipolar outflows (as compared with the result of 22% in the first version of the MMI catalog that contains no information about EGO). 99 from 139 class I methanol masers (71%) are identified with SDC. Thus, it seems possible that the MMI can be formed in isolated self-gravitating condensations, which are the silhouette of dark clouds - IRDC and SDC.
25 GHz methanol masers in regions of massive star formation
Authors: Britton Tui R. , Voronkov Maxim A.
Published: July 2012

The bright 25 GHz series of methanol masers is formed in highly energetic regions of massive star formation and provides a natural signpost of shocked gas surrounding newly forming stars. A systematic survey for the 25 GHz masers has only recently been carried out. We present the preliminary results from the interferometric follow up of 51 masers at 25 GHz in the southern sky.
44-GHz class I methanol maser survey towards 6.7-GHz class II methanol masers
Authors: Byun Do-Young , Kim Kee-Tae , Bae Jae-Han
Published: July 2012

The Class II 6.7-GHz methanol maser is a tracer of high mass young stellar objects. We present results of a 44-GHz class I methanol maser and 22-GHz water maser survey using the KVN (Korean VLBI Network) 21-m single dish radio telescopes towards 284 6.7-GHz maser sites. Class I methanol maser and water maser emission is detected towards 116 (41%) and 136 (48%) sources, respectively. About 50 sources have a peak flux density higher than 10 Jy at 44-GHz. They are candidates for VLBI studies using the KVN.
The VLBI mapping survey of the 6.7 GHz methanol masers with the JVN/EAVN
Authors: Fujisawa K. , Hachisuka K. , Sugiyama K. , Doi A. , Honma M. , Yonekura Y. , Hirota T. , Sawada-Satoh S. , Murata Y. , Motogi K. , Ogawa H. , Chen X. , Kim K.-T. , Shen Z.-Q.
Published: July 2012

We present VLBI maps of the 6.7 GHz methanol maser emission in 32 sources obtained using the Japanese VLBI Network (JVN) and the East-Asian VLBI Network (EAVN). All of the observed sources provide new VLBI maps, and the spatial morphologies have been classified into five categories similar to the results obtained from European VLBI Network observations (Bartkiewicz et al. 2009). The 32 methanol sources are being monitored to measure the relative proper motions of the methanol maser spots.
New OH Observations toward Northern Class I Methanol Masers
Authors: Val'tts I. E. , Litovchenko I. D. , Bayandina O. S. , Alakoz A. V. , Larionov G. M. , Mukha D. V. , Nabatov A. S. , Konovalenko A. A. , Zakharenko V. V. , Alekseev E. V. , Nikolaenko V. S. , Kulishenko V. F. , Odincov S. A.
Published: July 2012

Maser emission of OH(1720) is formed, according to modern concepts, under the influence of collisional pumping. Class I methanol masers (MMI) are also formed by a collisional mechanism of the inversion of the molecular levels. It is not excluded in this case that physical conditions in the condensations of the interstellar medium where masers are formed may be similar for MMI and OH(1720) masers, and they can associate with each other. To establish a possible association between these two kinds of masers, and obtain reliable statistical estimates, a survey of class I methanol masers at a frequency of 1720 MHz has been carried out.
22 GHz Water Maser Survey of the Xinjiang Astronomical Observatory
Authors: Zhou Jian-jun , Esimbek Jarken , Wu Gang
Published: July 2012

Water masers are good tracers of high-mass star-forming regions. Water maser VLBI observations provide a good probe for studying high-mass star formation and galactic structure. We plan to make a blind survey toward the northern Galactic plane in future years using the 25 m radio telescope of the Xinjiang Astronomical Observatory. We will select some water maser sources discovered in the survey and perform high resolution observations to study the gas kinematics close to high-mass protostars.
Masers in Starburst Galaxies
Authors: Darling Jeremy
Published: July 2012

Masers in starburst galaxies are outstanding probes of a range of phenomena related to galaxy and black hole evolution, star formation, and magnetic fields. Here I briefly discuss five related topics: (1) Galactic analog water masers in nearby galaxies; (2) multiwavelength solutions to the OH megamaser puzzle in major galaxy mergers; (3) formaldehyde anti-inversion in starburst galaxies; (4) OH spoofing in HI surveys; and (5) new discovery space in radio line surveys. New insights into the physical conditions responsible for OH megamasers, including indications of a critical molecular gas density obtained from the formaldehyde “densitometer,” will be applicable to future surveys, particularly surveys for redshifted hydrogen where OH lines arising in major galaxy mergers can “contaminate” the disk population identified by the HI 21 cm line. Blind radio spectral line surveys also offer the opportunity for unexpected discoveries of new nonthermal radio lines.
Searching for new OH megamasers out to redshifts z>1
Authors: Willett Kyle W.
Published: July 2012

We have carried out a search for 18-cm OH megamaser (OHM) emission with the Green Bank Telescope. The targeted galaxies comprise a sample of 121 ULIRGs at 0.09<z<1.5, making this is the first large, systematic search for OHMs at z>0.25. Nine new detections of OHMs are reported, all at redshifts z<0.25. For the remainder of the galaxies, observations constrain the upper limit on OH emission; this rules out OHMs of moderate brightness (LOH>103 L⊙) for 26% of the sample, and extremely bright OHM emission (LOH>104 L⊙) for 73% of the sample. Losses from RFI result in the OHM detection fraction being significantly lower than expected for galaxies with LIR>1012 L⊙. The new OHM detections are used to calculate an updated OH luminosity function, with Φ∝ LOH−0.66; this slope is in agreement with previous results. Non-detections of OHMs in the COSMOS field constrain the predicted sky density of OHMs; the results are consistent with a galaxy merger rate evolving as (1+z)m, where m≤6.
Expectations of maser studies with FAST
Authors: Zhang Jiang Shui , Li Di , Wang Jun Zhi
Published: July 2012

The Five-hundred-meter Aperture Spherical radio Telescope (FAST) is being built by the Chinese and will be the largest single dish radio telescope in the world. FAST, with much increase in sensitivity, will give astronomers good opportunities to answer many fundamental questions in astronomy. Here we give a brief introduction of FAST and its enormous potential for studying Galactic and extragalactic masers.
The origin of Keplerian megamaser disks
Authors: Wardle Mark , Yusef-Zadeh Farhad
Published: July 2012

Several examples of thin, Keplerian, sub-parsec megamaser disks have been discovered in the nuclei of active galaxies and used to precisely determine the mass of their host black holes. We show that there is an empirical linear correlation between the disk radius and black hole mass and that such disks are naturally formed as molecular clouds pass through the galactic nucleus and temporarily engulf the central supermassive black hole. For initial cloud column densities below about 1023.5 cm−2 the disk is non-self gravitating, but for higher cloud columns the disk would fragment and produce a compact stellar disk similar to that observed around Sgr A* at the galactic centre.
Methanol Maser Parallaxes and Proper Motions
Authors: Xu Y. , Reid M. J. , Moscadelli L. , Menten K. M. , Zheng X. W. , Brunthaler A. , Zhang B. , Rygl K. L. J. , Li J. J. , Sanna A.
Published: July 2012

Due to their compactness, persistence and slow motion, Class II CH3OH masers are excellent targets for parallax and proper motion measurements for massive star-forming regions in the Galactic Disk. These measurements can be used to improve our understanding of the spiral structure and dynamics of the Milky Way. At the same time, Class II CH3OH masers can also be used to study gas kinematics close to the exciting star, tracing rotation, infall and/or outflow motions.
VLBI multi-epoch water maser observations toward massive protostars
Authors: Torrelles José M. , Gómez José F. , Patel Nimesh A. , Curiel Salvador , Anglada Guillem , Estalella Robert
Published: July 2012

VLBI multi-epoch water maser observations are a powerful tool to study the gas very close to the central engine responsible for the phenomena associated with the early evolution of massive protostars. In this paper we present a summary of the main observational results obtained toward the massive star-forming regions of Cepheus A and W75N. These observations revealed unexpected phenomena in the earliest stages of evolution of massive objects (e.g., non-collimated “short-lived” pulsed ejections in different massive protostars), and provided new insights in the study of the dynamic scenario of the formation of high-mass stars (e.g., simultaneous presence of a jet and wide-angle outflow in the massive object Cep A HW2, similar to what is observed in low-mass protostars). In addition, with these observations it has been possible to identify new, previously unseen centers of high-mass star formation through outflow activity.
Astrometry of Galactic Star-Forming Regions ON1 and ON2N with VERA
Authors: Nagayama Takumi ,   VERA project members
Published: July 2012

We conducted the astrometry of H2O masers in the Galactic star-forming regions ON1 and ON2N with the VLBI Exploration of Radio Astrometry (VERA). The measured distances to ON1 and ON2N are 2.47±0.11 kpc and 3.83±0.13 kpc, respectively. In the case that ON1 and ON2N are on a perfect circular rotation, we estimate the angular rotation velocity of the Galactic rotation at the Sun (the ratio of the Galactic constants) to be 28 ± 2 km s−1 kpc−1 using the measured distances and three-dimensional velocity components of ON1 and ON2N. This value is larger than the IAU recommended value of 25.9 km s−1 kpc−1, but consistent with other results recently obtained with the VLBI technique.
VLBI maser kinematics in high-mass SFRs: G23.01–0.41
Authors: Sanna Alberto , Moscadelli Luca , Cesaroni Riccardo , Goddi Ciriaco
Published: July 2012

Very Long Baseline Interferometry studies of different maser species observed at multiple epochs allow complementary measurements of the 3-dimensional velocity field of gas close (≲ 103 AU) to massive young stellar objects. Here, we review our recent results toward the high-mass star-forming region G23.01–0.41, where all the strongest molecular maser transitions known to date cluster within 2000 AU from the center of an hot molecular core and are associated with a so called extended green object. The overall maser kinematics reveals a common outflowing motion from a central object; the details of the spatial distribution and velocity field of each maser species hint at the presence of different dynamical structures: a collimated jet, a wide-angle wind, and a flattened rotating core. We further compare the simultaneous presence of maser emission from different molecular species with a recent evolutionary sequence for masers associated with massive young stellar objects.
Astrometry of water masers in post-AGB stars
Authors: Imai Hiroshi ,   VERA collaboration
Published: July 2012

Measurements of trigonometric parallaxes and secular motions of evolved stars, especially post-AGB stars including central objects of planetary nebulae and water fountain sources as well as peculiar or unclassified stars, provide unambiguous source distance scales and information on their orbits in the Milky Way Galaxy. True source luminosities and kinematical properties should lead us to elucidate the true characteristics and evolutional tracks of these stars. Here we present the recent results of astrometry towards H2O maser sources with the VLBI Exploration of Radio Astormetry (VERA). The target sources include a planetary nebula (K3–35), a pre-PN (IRAS 19312+1950), a water fountain (IRAS 18286−0959) and a K-type star (IRAS 22480+6002). We have demonstrated that parental stars of the former three sources should be intermediate-mass stars from their luminosities and orbits in the Milky Way. It is suggested that IRAS 22480+6002 should be a K-type supergiant previously suggested rather than an RV Tau variable star.
Relative parallaxes in the massive star forming region W33
Authors: Immer K. , Reid M. J. , Menten K. M.
Published: July 2012

The massive star forming complex W33 contains several molecular clouds at different stages of star formation activity, ranging from quiescent to highly active clouds. Our trigonometric parallax observations of water masers in this complex, conducted with the VLBA at 22.2 GHz, show that all water masers have the same distance of 2.4 kpc, locating the W33 complex in the Sagittarius spiral arm.
3-Dimensional kinematics of water/SiO masers in Orion-KL
Authors: KIM Mi Kyoung , Hirota Tomoya , Hideyuki Kobayashi ,   VERA project team members
Published: July 2012

Results of multi-epoch VLBI observations toward water/SiO masers in Orion-KL are presented. We conducted high-resolution VLBI observations of water/SiO masers with VERA to probe the structure and the kinematics of the disk/outflow in Orion-KL. The VERA observations provide the positions and proper motions of masers features in Orion-KL with the highest accuracy ever observed. The results of water and SiO maser observations suggest that Source I is a massive YSO with an accretion disk and a collimated outflow.
Mass distribution of the Galaxy with VERA
Authors: Sakai Nobuyuki , Honma Mareki , Nakanishi Hiroyuki , Sakanoue Hirofumi , Kurayama Tomoharu ,   VERA project members
Published: July 2012

We aim to reveal the mass distribution of the Galaxy based on a precise rotation curve constructed using VERA observations. We have been observing Galactic H2O masers with VERA. We here report one of the results of VERA for IRAS 05168+3634. The parallax is 0.532 ± 0.053 mas which corresponds to a distance of 1.88+0.21−0.17 kpc, and the proper motions are (μαcosδ, μδ) = (0.23 ± 1.07, −3.14 ± 0.28) mas yr−1. The distance is significantly smaller than the previous distance estimate of 6 kpc based on a kinematic distance. This drastic change places the source in the Perseus arm rather than in the Outer arm. Combination of the distance and the proper motions with the systemic velocity provides a rotation velocity of 227+9−11 km s−1 at the source assuming Θ0 = 240 km s−1. The result is marginally slower than the rotation velocity at LSR with ~ 1−σ significance, but consistent with previous VLBI results for six sources in the Perseus arm. We also show the averaged disk peculiar motion over the seven sources in the Perseus arm as (Umean, Vmean) = (11 ± 3, −17 ± 3) km s−1. It suggests that the seven sources in the Perseus arm are systematically moving toward the Galactic center, and lag behind the Galactic rotation with more than 3-σ significance.
Radio Recombination Line Maser Objects: New Detections with the SMA
Authors: Jiménez-Serra Izaskun
Published: July 2012

Hydrogen radio recombination line (RRL) masers are a rare phenomenon in star forming regions. Since RRL masers were first detected in 1989 toward the emission line star MWC349A, several single-dish surveys at millimeter wavelengths have been carried out to detect other RRL maser objects. However, although RRL maser amplification is expected to appear at wavelengths <2mm, MWC349A still remains as the only RRL maser object known to date. In this contribution, I will present our recent findings of two new RRL maser objects with the Submillimeter Array (SMA) toward the massive star forming regions Cepheus A HW2 and MonR2-IRS2. Sub-millimeter observations with interferometers such as the SMA and the Atacama Large Millimeter Array (ALMA) open the possibility to detect a much larger sample of RRL maser objects, where very detailed information about the kinematics and physical structure of the innermost ionized regions can be obtained toward these objects.
OH Maser sources in W49N: probing differential anisotropic scattering with Zeeman pairs
Authors: Deshpande Avinash A. , Goss W. M. , Mendoza-Torres J. E.
Published: July 2012

Our analysis of a VLBA 12-hour synthesis observations of the OH masers in W49N has provided detailed high angular-resolution images of the maser sources, at 1612, 1665 and 1667 MHz. The images, of several dozens of spots, reveal anisotropic scatter broadening; with typical sizes of a few tens of milli-arc-seconds and axial ratios between 1.5 to 3. The image position angles oriented perpendicular to the galactic plane are interpreted in terms of elongation of electron-density irregularities parallel to the galactic plane, due to a similarly aligned local magnetic field. However, we find the apparent angular sizes on the average a factor of 2.5 less than those reported by Desai et al., indicating significantly less scattering than inferred earlier. The average position angle of the scattered broadened images is also seen to deviate significantly (by about 10 degrees) from that implied by the magnetic field in the Galactic plane. More intriguingly, for a few Zeeman pairs in our set, we find significant differences in the scatter broadened images for the two hands of polarization, even when apparent velocity separation is less than 0.1 km/s. Here we present the details of our observations and analysis, and discuss the interesting implications of our results for the intervening anisotropic magneto-ionic medium, as well as a comparison with the expectations based on earlier work.
MeerKAT and its potential for Cosmic MASER Research
Authors: Booth Roy , Goedhart Sharmila , Jonas Justin
Published: July 2012

The MeerKAT radio telescope array is the South African precursor instrument for the proposed Square Kilometer Array's mid-band frequency range. It will be the most sensitive centimetre-wavelength telescope in the southern hemisphere until the SKA is built. It will cover a broad range of astronomical science from the evolution of galaxies to tests of Einstein's theory of General Relativity, using Pulsars. The chosen frequency bands will enable sensitive southern Galactic maser surveys in the main lines of hydroxyl, 12 GHz methanol and perhaps 14.5 GHz formaldehyde lines as well as searches for redshifted water masers from red-shifts greater than about 0.5. Proposals for Large Surveys using MeerKAT were solicited in late 2009 and resulted in some 20 proposals from teams comprising 500 scientists, world-wide. The successful proposals relevant to maser research will be discussed below.
KVN Single-dish Water and Methanol Maser Line Surveys of Galactic YSOs
Authors: Kim Kee-Tae , Byun Do-Young , Bae Jae-Han , Kim Won-Ju , Kang Hyun-Woo , Oh Chung Sik , Youn So-Young
Published: July 2012

We have carried out simultaneous 22 GHz H2O and 44 GHz Class I CH3OH maser line surveys of more than 1500 intermediate- and high-mass YSOs in the Galaxy using newly-constructed KVN 21-m telescopes. As the central (proto)stars evolve, the detection rates of the two masers rapidly decrease for intermediate-mass YSOs while the rates increase for high-mass YSOs. These results suggest that the occurrence of the two masers is closely related both to the evolutionary stage of the central objects and to the circumstellar environments. CH3OH masers always have very similar velocities (<10 km s−1) to the natal dense cores, whereas H2O masers often have significantly different velocities. The isotropic luminosities of both masers are well correlated with the bolometric luminosities of the central (proto)stars.
EVLA imaging of the water masers in the massive protostellar cluster NGC6334I
Authors: Hunter Todd R. , Brogan Crystal L.
Published: July 2012

We have used the recently-upgraded Karl G. Jansky Very Large Array (VLA) in A-configuration to observe the water masers in the massive protostellar cluster NGC6334I with broad bandwidth and high spectral resolution. Four groups of maser spots are found. The two groups with the broadest velocity span (40 km/s) are towards the UCHII region and the hot core SMA1. The spatial kinematics of the SMA1 masers are consistent in sense and orientation with the large-scale CO outflow and appear to trace the base of the outflow from a protostar at the dust peak of SMA1. Additional masers at the southern end of SMA1 provide evidence for a second protostar. The highest intensity maser lies about 2″ north of SMA1. Interestingly, no water masers are seen on the equally impressive hot core SMA2. Finally, we have detected maser emission toward the enigmatic source SMA4, which shows no millimeter molecular lines despite having strong, compact submillimeter continuum and may trace another protostar.
No evidence of programmed late-life mortality in the Finnish famine cohort
Authors: Saxton K. , Falconi A. , Goldman-Mellor S. , Catalano R.
Published: July 2012

The developmental origins hypothesis suggests that morbidity and premature mortality arise, in part, from adverse exposures in utero and early in development. Evidence suggests a connection between early nutritional deficits and adult morbidity; however, the effects on mortality have been less well studied and previous studies provide conflicting results. We extracted Finnish birth cohort death rates from the Human Mortality Database. Our test asks whether men or women born during the 1867–1868 Great Finnish Famine exhibited death rates in old age different from expected, based on death rates among Finnish cohorts born 1818–1866. We found no support for the argument that exposure to the Finnish famine in utero induced excess mortality from age 60 to 89 in either men or women. Our results suggest that the Finnish famine did not induce, via epigenetic changes or any other mechanism, premature mortality in older age among exposed individuals.
Impact of sea‐ice biology on overall primary production in a biophysical model of the pan‐Arctic Ocean
Authors: Dupont Frédéric
Published: July 2012

The contribution of sea‐ice biology and impact of Arctic warming on overall primary production in a Pan‐Arctic ocean model are investigated in a 57 year (1950–2006) simulation at coarse resolution using a simple ecosystem model. The ice biology model formally represents the growth and aggregation of micro algae into an ice‐water interface, nearly undisturbed by surface mixed layer dynamics. The importance of this so‐called ‘ice‐algae’ stems from their significant contribution to the total primary production (up to 50% depending on the locations, according to observations described in Gosselin et al. (1997). Simple 1D tests reveal that, depending on their initial biomass and light availability, ice algae can affect the temporal variation of surface nutrients, while they marginally impact the total primary production, or the long term position of the nutricline. The sea‐ice primary production is found in the model to be as high as 40% of the total primary production depending on the location and 7.5% for the whole Arctic. The modeled primary production of the ocean is negatively correlated to the September ice cover whereas the production in the ice is more weakly positively correlated. Because of the negative correlation between sea ice cover and pelagic primary production, the short term response to the continuing ice decline will be an increased total production as seen in the model, while the ice algae production would decline.
Modification of a Kenai eddy along the Alaskan Stream
Authors: Ueno Hiromichi , Yasuda Ichiro , Itoh Sachihiko , Onishi Hiroji , Hiroe Yutaka , Suga Toshio , Oka Eitarou
Published: July 2012

A Kenai eddy was studied through analyses of satellite altimeter data and hydrographic data from shipboard and Argo float observations. This eddy formed in December 2006 south of the Kenai Peninsula and propagated southwestward along the Alaskan Stream. The eddy held horizontally uniform warm core water in January 2007. In late winter 2007, this core water was cooled from the top and a subsurface temperature maximum was formed around 26.5σθ. Two years later in summer 2009, warm and low‐dissolved‐oxygen (low‐DO) water characterized by a temperature maximum around 26.5σθ was observed again in the eddy core and was likely the remnant of original core water. At the same time, cold and high‐DO water intrusions occurred in the eddy core, suggesting that strong modification of core water was ongoing. After summer 2009, the core water was fully changed through interaction with another eddy.
Variability of aerosols in the tropical Atlantic Ocean relative to African Easterly Waves and their relationship with atmospheric and oceanic environments
Authors: Zuluaga Manuel D. , Webster Peter J. , Hoyos Carlos D.
Published: July 2012

It is well known that aerosols impact climate directly through modifying the radiation budget and indirectly through the modification of cloud processes. Yet, in spite of an improved understanding of the various roles that aerosols play in climate, there still exists uncertainty in their spatial and temporal distributions and their relationship to atmospheric dynamic. Here, we use the Aerosol Index from the Total Ozone Mapping Spectrometer and Aerosol Optical Depth from the Moderate Resolution Imaging Spectroradiometer, in conjunction with atmospheric and oceanic satellite observations and reanalysis data sets to investigate aerosol‐environment relationships and interactions over the tropical Atlantic Ocean. Spectral and composite analyses of surface temperature, atmospheric wind, geopotential height, outgoing longwave radiation and precipitation, together with the climatology of aerosols, provide insight on how the variables interact. Different modes of variability, especially on intraseasonal time scales, appear as strong modulators of the aerosol distribution. In particular, we investigate how two modes of variability related to westward propagating African Easterly Waves affect the horizontal and vertical structure of the environment and thus the aerosol distribution. The pattern of propagation of aerosol load shows a strong correspondence with the progression of the atmospheric and oceanic synoptic conditions that have mobilized dust over the African continent and advect it over the Atlantic Ocean. We extend previous studies related with dust variability over the Atlantic region by evaluating the performance of the long period satellite aerosol retrievals in determining modes of aerosol variability. Results of this work are described as useful in allowing a more precise understanding of the response of the energy budget, precipitation and atmospheric circulation to changes in aerosol loading.
Aerosol optical properties retrieved from Sun photometer measurements over Shanghai, China
Authors: He Qianshan , Li Chengcai , Geng Fuhai , Yang Hequn , Li Peiren , Li Tingting , Liu Dongwei , Pei Zhen
Published: July 2012

Using a CIMEL Sun photometer, we conducted continuous observations over the urban area of Shanghai (31°14′N, 121°32′E) from 18 April 2007 to 31 January 2009. The aerosol optical depth (AOD), Angstrom wavelength exponent, single scattering albedo (ω0), and aerosol particle size distribution were derived from the observational data. The monthly mean AOD reached a maximum value of 1.20 in June and a minimum value of 0.43 in January. The monthly averaged Angstrom wavelength exponent reached a minimum value of 1.15 in April and a maximum value of 1.41 in October. The frequencies of the AOD and Angstrom wavelength exponent presented lognormal distributions. The averaged ω0 at 550 nm was 0.94 throughout the observation period, indicating that the aerosols over Shanghai are composed mainly of scattering particles. The concentrations of coarse mode and accumulation mode aerosols over Shanghai were highest in spring compared with other seasons, especially for those particles with radii between 1.0 and 2.0 μm. The median radius of monthly averaged accumulation mode aerosols increased with increasing AOD, and fine particles accounted for the majority of the aerosol volume concentration. The ratios of the monthly averaged volume concentration of accumulation mode and coarse mode aerosols (Vf/Vc) were over 0.6 for all months studied and reached up to 1.94 in August. The volumes of the two modes changed with AOD, but their correlations presented different sensitivities, that is, the volume concentration of accumulation mode aerosols was more sensitive to variations in AOD than that of coarse mode aerosols. The aerosol volume concentration decreased with increasing ω0, indicating that the higher the volume concentration of aerosols, the higher the absorption in particle extinction properties. The increase in absorption was caused primarily by secondary species coated on black carbon (BC) and primary organic carbon (POC) particles.
Analysis of soil moisture memory from observations in Europe
Authors: Orth R. , Seneviratne S. I.
Published: July 2012

Soil moisture is known to show distinctive persistence characteristics compared to other quantities in the climate system. As soil moisture is governing land‐atmosphere feedbacks to a large extent, its persistence can provide potential to improve seasonal climate predictions. So far, many modeling studies have investigated the nature of soil moisture memory, with consistent, but model‐dependent results. This study investigates soil moisture memory in long‐term observational records based on data from five stations across Europe. We investigate spatial and seasonal variations in soil moisture memory and identify their main climatic drivers. Also, we test an existing framework and introduce an extension thereof to approximate soil moisture memory and evaluate the contributions of its driving processes. At the analyzed five sites, we identify the variability of initial soil moisture divided by that of the accumulated forcing over the considered time frame as a main driver of soil moisture memory that reflects the impact of the precipitation regime and of soil and vegetation characteristics. Another important driver is found to be the correlation of initial soil moisture with subsequent forcing that captures forcing memory as it propagates to the soil and also land‐atmosphere interactions. Thereby, the role of precipitation is found to be dominant for the forcing. In contrast to results from previous modeling studies, the runoff and evapotranspiration sensitivities to soil moisture are found to have only a minor influence on soil moisture persistence at the analyzed sites. For the central European sites, the seasonal cycles of soil moisture memory display a maximum in late summer and a minimum in spring. An opposite seasonal cycle is found at the analyzed site in Italy. High soil moisture memory is shown to last up to 40 days in some seasons at most sites. Extremely dry or wet states of the soil tend to increase soil moisture memory, suggesting enhanced prediction potential during extreme events at most sites considered in this study.