Types Of Masers Research Articles

ON THE POSSIBILITY OF THE AGROGLYPHS EMERGENCE UNDER THE INFLUENCE OF COSMIC FACTORS

Based on the study of the phenomenon of wheat stalks regular lodging on a large area (Voznesenovsky phenomenon), the possibility of linking this and other similar phenomena (agroglyphs) of natural origin with the action of cosmic factors is analyzed. The criteria features of the phenomena under consideration and particular structural features of the phenomenon under study are determined. It is shown that in order to explain the totality of facts, the most promising is to attract the idea of a short–term radiation effect of sufficiently high energy on the entire plant array. This point of view is quite consistent with the features of the structure and physiology of cereal crops stems. The reason for the wheat stalks lodging could be the heating of their nodes under the action of a pulse of microwave radiation. The preference for microwave radiation, but not infrared radiation, is physically justified. The supposed source of the microwave radiation pulse is the development of a meteor phenomenon generated by the intrusion into the Earth's atmosphere of a meteor body containing a significant mass of water ice. The paper shows that in this case, one can expect the appearance of a pulse of forced (maser–type) radiation at a wavelength of 1,35 cm. This radiation can reach the Earth's surface quite freely. Calculations of the energy and mass of a meteor body, which capable to generat the considered effect, are in good agreement with the data of meteor astronomy. Orderliness in the lodging of stems is explained from the standpoint of heliotropism of plant development. The general aspects of the agroglyphs appearance connection with the manifestations of meteoric activity and the prospects for the development of the study are discussed.

ALMA observations of the Extended Green Object G19.01–0.03 – ii. A massive protostar with typical chemical abundances surrounded by four low-mass pre-stellar core candidates

ABSTRACT We present a study of the physical and chemical properties of the Extended Green Object (EGO) G19.01−0.03 using sub-arcsecond angular resolution Atacama Large Millimetre/submillimetre Array (ALMA) 1.05 mm and Karl G. Jansky Very Large Array (VLA) 1.21 cm data. G19.01−0.03 MM1, the millimetre source associated with the central massive young stellar object (MYSO), appeared isolated and potentially chemically young in previous Submillimetre Array observations. In our ∼0.4 arcsec-resolution ALMA data, MM1 has four low-mass millimetre companions within 0.12 pc, all lacking maser or outflow emission, indicating they may be pre-stellar cores. With a rich ALMA spectrum full of complex organic molecules, MM1 does not appear chemically young, but has molecular abundances typical of high-mass hot cores in the literature. At the 1.05 mm continuum peak of MM1, N(CH3OH) = (2.22 ± 0.01) × 1018 cm−2 and $T_{\mathrm{ex}} = 162.7\substack{+0.3 \\ -0.5}$ K based on pixel-by-pixel Bayesian analysis of LTE synthetic methanol spectra across MM1. Intriguingly, the peak CH3OH Tex = 165.5 ± 0.6 K is offset from MM1’s millimetre continuum peak by 0.22 arcsec ∼ 880 au, and a region of elevated CH3OH Tex coincides with free–free VLA 5.01 cm continuum, adding to the tentative evidence for a possible unresolved high-mass binary in MM1. In our VLA 1.21 cm data, we report the first NH3(3,3) maser detections towards G19.01−0.03, along with candidate 25 GHz CH3OH 5(2, 3) − 5(1, 4) maser emission; both are spatially and kinematically coincident with 44 GHz Class I CH3OH masers in the MM1 outflow. We also report the ALMA detection of candidate 278.3 GHz Class I CH3OH maser emission towards this outflow, strengthening the connection of these three maser types to MYSO outflows.

Online Database of Multiwavelength Water Masers in Galactic Star-forming Regions

Abstract In this paper, we present an online multiwavelength database of water masers in star-forming regions of the Galaxy. The collected data represent ∼95% of all observations of water masers in star-forming regions published since 1989. Nineteen transitions are included, from 22 GHz to 1.88 THz. The MaserDB.net information system provides fast and open access to the collected data, including maser tabular data, spectra, and interferometric maser spot data. The database covers ∼18,700 individual observations and ∼7200 maser detections. The data on the water maser detection are available for ∼2600 sources, and interferometric data are available for ∼560 sources. Statistical analysis of the water masers’ data and comparison with other abundant maser species found in star-forming regions (OH and CH3OH of class I and II) show that water masers are the most ubiquitous maser type. Access to the water maser database is available online at https://MaserDB.net. The database can be queried using a web search form or Structured Query Language.

Revisiting the formaldehyde masers

Context. The 4.8 GHz formaldehyde (H2CO) masers are one of a number of rare types of molecular masers in the Galaxy. There still is not agreement on the mechanism responsible for the inversion of the 110−111 transition and the conditions under which an inversion can occur, and therefore how to interpret the masers. Aims. The aim of the present calculations is to explore a larger region of parameter space to improve on our previous calculations, thereby to better understand the range of physical conditions under which an inversion of the 110−111 transition occurs. We also aim to understand recently published results that H2CO masers are radiatively pumped. Methods. We solve the rate equations of the first 40 rotational levels of o-H2CO using a fourth-order Runge-Kutta method. We consider gas kinetic temperatures between 10 and 300 K, H2 densities between 104 and 106 cm−3, and a number of different dust temperatures and grey-body spectral energy density distributions. Results. We show that when using a black body radiation field the inversion of any transition will disappear as the kinetic temperature approaches the black-body radiation temperature since the system, consisting of the gas and radiation field, approaches thermodynamic equilibrium. Using a grey-body dust radiation field appropriate for Arp 220 we find that none of 110−111, 211−212, and 312−313 transitions are inverted for kinetic temperatures less than 100 K. Our calculations also show that in theory the 110−111 transition can be inverted over a large region of explored parameter space in the presence of an external far-infrared radiation field. Limiting the abundance of H2CO to less than 10−5, however, reduces the region where an inversion occurs to H2 densities ≳105 cm−3 and kinetic temperatures ≳100 K. We propose a pumping scheme for the H2CO masers which can explain why collisions play a central role in inverting the 110−111 transition, and therefore why an external radiation field alone does not lead to an inversion. Conclusions. Collisions are an essential mechanism for the inversion of the 110−111 transition. Our results suggest that 4.8 GHz H2CO megamasers are associated with hot and dense gas typical of high mass star forming regions rather than with cold material. Although limiting the H2CO abundance to less than 10−5 significantly reduces the region in parameter space where the 110−111 is inverted, it still is not clear whether this is the only reason why these masers are so rare.

Searching water megamasers by using mid-infrared spectroscopy (I): Possible mid-infrared indicators

ABSTRACT Water megamasers at 22 GHz with a gas disc configuration in galaxies provide the most precise measurements of supermassive black hole masses, as well as independent constraints on the Hubble constant in the nearby universe. The existence of other maser types, such as jet or outflow masers, represents another tracer for AGN science. However, the detection rate of water megamasers in galaxies is extremely low. Over 40 yr, only ∼ 160 galaxies are found to harbour maser emission, and ∼30 per cent of them show features in their maser emission that indicate a disc-like geometry. Therefore, increasing the detection rate of masers is a crucial task to allow expanding on maser studies. We present a comparison of mid-infrared spectroscopic data between a maser galaxy sample and a Seyfert 2 control sample. We find that maser galaxies show significant peculiarities in their mid-infrared spectra: (1) Maser galaxies tend to present stronger silicate absorption at τ9.7 $\mu\mathrm{ m}$ than the control sample, (2) PAH 11.3 $\mu$m emission in maser galaxies is much weaker than in the control sample, (3) spectral indices at 20–30 $\mu$m are steeper in maser galaxies than in the control sample and tend to be mid-infrared enhanced population. We conclude that there may be good indicators in mid-infrared and far-infrared which could differentiate maser and non-maser Seyfert 2 galaxies. Upcoming infrared facilities, such as the James Webb Space Telescope, may be able to exploit these and other useful criteria and tracers for water megamaser observations.

Water megamaser emission in hard X-ray selected AGN

Context. Water megamaser emission at 22 GHz has proven to be a powerful tool for astrophysical studies of active galactic nuclei (AGN) because it allows an accurate determination of the mass of the central black hole and of the accretion disc geometry and dynamics. However, after searches among thousands of galaxies, only about 200 of them have shown such spectroscopic features, most of them of uncertain classification. In addition, the physical and geometrical conditions under which a maser activates are still unknown. Aims. We characterize the occurrence of water maser emission in an unbiased sample of AGN by investigating the relation with the X-ray properties and the possible favourable geometry that is required to detect water maser. Methods. We searched for 22 GHz maser emission in a hard X-ray selected sample of AGN, taken from the INTEGRAL/IBIS survey above 20 keV. Only half of the 380 sources in the sample have water maser data. We also considered a volume-limited sub-sample of 87 sources, for which we obtained new observations with the Green Bank and Effelsberg telescopes (for 35 sources). We detected one new maser and increased its radio coverage to 75%. Results. The detection rate of water maser emission in the total sample is 15 ± 3%. This fraction increases to 19 ± 5% for the complete sub-sample, especially when we consider type 2 (22 ± 5% and 31 ± 10% for the total and complete samples, respectively) and Compton-thick AGN (56 ± 18% and 50 ± 35% for the total and complete samples, respectively). No correlation is found between water maser and X-ray luminosity. We note that all types of masers (disc and jet) are associated with hard X-ray selected AGN. Conclusions. These results demonstrate that the hard X–ray selection may significantly enhance the maser detection efficiency over comparably large optical or infrared surveys. A possible decline in detection fraction with increasing luminosity might suggest that an extremely luminous nuclear environment does not favour maser emission. The large fraction of CT AGN with water maser emission could be explained in terms of geometrical effects. The maser medium would then be the very edge-on portion of the obscuring medium.

The 6-GHz Multibeam Maser Survey – III. Comparison between the MMB and HOPS

We have compared the occurrence of 6.7-GHz and 12.2-GHz methanol masers with 22-GHz water masers and 6035-MHz excited-state OH masers in the 100 square degree region of the southern Galactic plane common to the Methanol Multibeam (MMB) and H2O southern Galactic Plane surveys (HOPS). We find the most populous star formation species to be 6.7-GHz methanol, followed by water, then 12.2-GHz and, finally, excited-state OH masers. We present association statistics, flux density (and luminosity where appropriate) and velocity range distributions across the largest, fully surveyed portion of the Galactic plane for four of the most common types of masers found in the vicinity of star formation regions. Comparison of the occurrence of the four maser types with far-infrared dust temperatures shows that sources exhibiting excited-state OH maser emission are warmer than sources showing any of the other three maser types. We further find that sources exhibiting both 6.7-GHz and 12.2-GHz methanol masers are warmer than sources exhibiting just 6.7-GHz methanol maser emission. These findings are consistent with previously made suggestions that both OH and 12.2-GHz methanol masers generally trace a later stage of star formation compared to other common maser types.

A WATER MASER AND NH3SURVEY OF GLIMPSE EXTENDED GREEN OBJECTS

We present the results of a Nobeyama 45-m water maser and ammonia survey of all 94 northern GLIMPSE Extended Green Objects (EGOs), a sample of massive young stellar objects (MYSOs) identified based on their extended 4.5 micron emission. We observed the ammonia (1,1), (2,2), and (3,3) inversion lines, and detect emission towards 97%, 63%, and 46% of our sample, respectively (median rms ~50 mK). The water maser detection rate is 68% (median rms ~0.11 Jy). The derived water maser and clump-scale gas properties are consistent with the identification of EGOs as young MYSOs. To explore the degree of variation among EGOs, we analyze subsamples defined based on MIR properties or maser associations. Water masers and warm dense gas, as indicated by emission in the higher-excitation ammonia transitions, are most frequently detected towards EGOs also associated with both Class I and II methanol masers. 95% (81%) of such EGOs are detected in water (ammonia(3,3)), compared to only 33% (7%) of EGOs without either methanol maser type. As populations, EGOs associated with Class I and/or II methanol masers have significantly higher ammonia linewidths, column densities, and kinetic temperatures than EGOs undetected in methanol maser surveys. However, we find no evidence for statistically significant differences in water maser properties (such as maser luminosity) among any EGO subsamples. Combining our data with the 1.1 mm continuum Bolocam Galactic Plane Survey, we find no correlation between isotropic water maser luminosity and clump number density. Water maser luminosity is weakly correlated with clump (gas) temperature and clump mass.

Internal Proper Motions of Methanol Masers at 6.7 GHz in Massive Star-Forming Region Onsala 1

We present the internal proper motions of 6.7 GHz methanol masers in a massive star-forming region, Onsala 1 (ON 1), measured using the Japanese very long baseline interferometry network (JVN) at three epochs spanning 778 days. The methanol masers were clearly distinct from water masers. The methanol masers surrounded an ultra-compact (UC) H II region, and their distribution was similar to that of hydroxyl masers. The internal motions of the methanol masers were clearly detected; they show outward motions in roughly the north–south direction with a relative velocity of $\sim\ $5 km s$^{-1}$. Their motion is similar to that of hydroxyl masers, which showed expansion at $\sim\ $5 km s$^{-1}$, and these two types of masers seem to trace the expanding UC H II region. Another possibility is that the methanol masers are associated with a molecular outflow observed by H$^{13}$CO$^{+}$ and SiO lines, because the direction and velocity of the methanol masers were similar to those of the molecular lines. Regarding the relative phases of water and methanol masers in the evolutionary stage of massive young stellar objects, we found that the former was earlier than the latter in ON 1 by comparing the sites associated with the masers. The water masers were associated with dust emission at submillimeter wavelengths, whereas the methanol masers were associated with an UC H II region at centimeter wavelengths, which appears at a later evolutionary phase than the dust core.

REVISING THE KINEMATICS OF 12 GHz CH3OH MASERS TOWARD W3(OH)

We derive accurate proper motions of the CH3OH 12 GHz masers toward the W3(OH) ultra-compact (UC) H ii region, employing seven epochs of VLBA observations spanning a time interval of about 10 yr. The achieved velocity accuracy is of the order of 0.1 km s−1, adequate to precisely measure the relative velocities of most of the 12 GHz masers in W3(OH), with amplitude varying in the range 0.3–3 km s−1. Toward W3(OH), the most intense 12 GHz masers concentrate in a small area toward the north (the northern clump) of the UC H ii region. We have compared the proper motions of the CH3OH 12 GHz masers with those (derived from literature data) of the OH 6035 MHz masers, emitting from the same region of the methanol masers. In the northern clump, the two maser emissions emerge from nearby (but likely distinct) cloudlets of masing gas with, in general, a rather smooth variation of line-of-sight and sky-projected velocities, which suggests some connection of the environments and kinematics traced by both maser types. The conical outflow model, previously proposed to account for the 12 GHz maser kinematics in the northern clump, does not reproduce the new, accurate measurements of 12 GHz maser proper motions and has to be rejected. We focus on the subset of 12 GHz masers of the northern clump belonging to the "linear structure at P.A. = 130°–140°," whose regular variation of LSR velocities with position presents evidence for some ordered motion. We show that the three-dimensional velocities of this "linear distribution" of 12 GHz masers can be well fitted considering a flat, rotating disk, seen almost edge-on.

Characteristics of infrared point sources associated with OH masers

We collect 3249 OH maser sources from the literature published up to April 2007, and compile a new catalog of OH masers. We look for the exciting sources of these masers and their infrared properties from IRAS and MSX data, and make a statistical study. MSX sources associated with stellar 1612 MHz OH masers are located mainly above the blackbody line; this is caused by the dust absorption of stellar envelopes, especially in the MSX_A band. The mid-IR sources associated with stellar OH masers are concentrated in a small region in an [A]–[D] vs. [A]–[E] diagram with a small fraction of contamination; this gives us a new criterion to search for new stellar OH masers and distinguish stellar masers from unknown types of OH masers. IR sources associated with 1612 MHz stellar OH masers show an expected result: the average flux of sources with F60 > F25 increases with increasing wavelength, while those with F60 < F25 vary little with wavelength, because the sources with F60 < F25 are much hotter than those with F60 > F25.

Star Formation from Spitzer (Lyman) to Spitzer (Space Telescope) and Beyond11Conference was held in Vienna on 2008 September 10–12, and was part of the European Astronomical Society’s JENAM 2008.

Star Formation from Spitzer (Lyman) to Spitzer (Space Telescope) and Beyond11Conference was held in Vienna on 2008 September 10–12, and was part of the European Astronomical Society’s JENAM 2008.

A laboratory experiment to investigate auroral kilometric radiation emission mechanisms

If an initially mainly rectilinear electron beam is subject to significant magnetic compression, the conservation of the magnetic moment results in the ultimate formation of a horseshoe distribution in phase space. A similar situation occurs where particles are accelerated into the auroral region of the Earth's magnetic dipole. Such a distribution has been shown to be unstable to a cyclotron resonance maser type of instability and it has been postulated that this may be the mechanism required to explain the production in these regions of auroral kilometric radiation (AKR) and also possibly radiation from other astrophysical objects such as stars with a suitable magnetic field configuration. In this paper we describe a laboratory experiment to investigate the evolution of an electron beam subject to a magnetic compression of up to a factor of 30.

CH3OH and H2O maser associations at very high angular resolution

6.7 and 12.2 GHz CHOH masers towards a selected sample of high-mass YSOs where both maser types have been detected. This work presents preliminary results obtained for a few objects of our sample, and discusses possible implications.

A Cyclotron Maser Instability with Application to Space and Laboratory Plasmas

When a beam of electrons moves into a converging magnetic field, the velocity distribution function takes on a horseshoe shape as a result of conservation of magnetic moment. A few years ago it was pointed out that such a distribution is unstable to a cyclotron maser type of instability and it was suggested that this instability might be the source of auroral kilometric radiation (Bingham, R. and Cairns, R. A., Phys. Plasmas 7, 3089 (2000).) and also of emission from certain types of star (Bingham, R., Cairns, R. A. and Kellett, B. J., Astron. Astrophys. 370, 1000 (2001).).Here we present more recent work on this topic. Since the dispersion relation which describes the instability only depends on the factor by which the magnetic field increases and on ratios of the wave plasma and cyclotron frequencies, it is possible to scale the effect to laboratory dimensions. An experiment to do this is being carried out at the University of Strathclyde and is expected to be operational during the summer of 2004. The objective is to investigate whether this mechanism might produce a useful radiation source, as well as to give a laboratory simulation of auroral kilometric radiation. The design of this experiment and its current status are described.On the theoretical side we discuss computer simulations showing the instability and its quasilinear saturation in the geometry of the experiment. We also describe a much more detailed theory of the linear instability than we have presented in previous work. Growth rates have been calculated in cylindrical geometry with various electron beam configurations and different cylindrical mode structures. These, and the simulations, support the conclusion of our earlier work that the instability has a high growth rate.

The association between masers and outflows in massive star forming regions

We report the results of a single-dish survey of molecular outflows towards a homogeneous sample of 136 ultracompact H II regions for which we had previously obtained observations in the methanol 6.7 GHz and water 22.2 GHz maser lines. The line profiles of the 13 CO J = 1-0 and 2-1 transitions have been compared to those of the corresponding lines of the C 18 O isotopomer to reveal the occurrence of line wings and hence of molecular outflows. We found 53 outflows resulting in an overall detection rate of ∼39%. The probability to have an outflow increases to about 50% in regions with maser emission, whereas it is about 25% in those without masers. If we consider just the outflow sources, the chance to find a maser is very high: 74%, without a significant difference between H 2 O and CH 3 OH. These results strongly confirm from a statistical point of view that both types of masers are closely associated with the evolutionary phase when outflows occur. The temperatures and optical depths of the molecular cloud hosting the ultracompact H II regions and the comparison between the detection rates suggest a tentative evolutionary scheme for massive star forming regions: the earliest phase is associated with maser emission and with an outflow not yet developed enough to be detected with single-dish observations; then maser emission disappears while the outflow is still present; and finally, only the ultracompact HII region without masers or outflows is present.

CH3OH and H2O masers in high-mass star-forming regions

We present a comparison of Class ii CH3OH (6.7 GHz) and H2O (22.2 GHz) masers at high spatial resolution in a sample of 29 massive star-forming regions. Absolute positions of both maser types are compared with mm dust continuum, cm continuum and mid-infrared sources. All maser features - regardless of the species - are associated with massive mm cores, but only 3 out of 18 CH3OH masers and 6 out of 22 H2O masers are associated with cm emission likely indicating the presence of a recently ignited massive star. These observations of a homogenous sample of massive, young star-forming regions confirm earlier results, obtained for each maser species separately, that both maser types are signposts of high-mass star formation in very early evolutionary stages. The data are consistent with models that explain CH3OH maser emission by radiative pumping in moderately hot cores, requiring the absence, or only weak, free-free cm continuum radiation due to recently ignited stars. Mid-infrared sources are associated with both maser types in approximately 60% of the observed fields. Thus, mid-infrared objects may power maser sites, but the detection of strong mid-infrared emission is not strictly necessary because it might be heavily extincted. A comparison of the spatial separations between the dierent observed quantities and other properties of the star-forming regions does not reveal any correlation. Our data suggest that CH3OH and H2O masers need a similar environment (dense and warm molecular gas), but that, due to the dierent excitation processes (radiative pumping for CH3OH and collisional pumping for H2O), no spatial correlations exist. Spatial associations are probably coincidences due to insucient angular resolution and projection eects. The kinematic structures we find in the dierent maser species show no recognizable pattern, and we cannot draw firm conclusions as to whether the features are produced in disks, outflows or expanding shock waves.

A New Cyclotron Maser Radiation Mechanism in Space Plasmas

In this paper, we discuss a new cyclotron maser type instability driven by a crescent or horseshaped electron distribution function. Such distribution functions are easily created by an electron beam moving into a stronger magnetic field region, where conservation of the first adiabatic invariant causes an increase in their pitch angle. This produces a broad region on the distribution function where ∂fe/∂v⊥ > 0. Planetary dipole magnetic fields are examples of where these types of distributions can be found. We examine the stability of these electron horseshoe distribution functions for right-hand extraordinary mode (R–X mode) radiation close to the electron cyclotron frequency propagating perpendicular to the magnetic field using both non-relativistic and relativistic beams.

Radiative instabilities and 1000 second fluctuations in astrophysical masers

A stability analysis for small (linear) perturbations is presented for the radiation in astrophysical masers treated in the usual, linear maser approximation. Instabilities that oscillate with a period of about L/c, where L is the length of the maser are found. They occur (1) when the maser is partly but not heavily saturated, (2) when the decay rate Gamma for the molecular states is near c/L, and (3) when the product of the brightness temperature T sub 0 of the incident radiation and the angle for the beaming is less than a critical value that depends upon the particular masing transition. A fourth parameter, the fractional inversion in the pumping multiplied by (T sub 0/frequency), determines the importance of spontaneous emission which can eliminate the instabilities. These instabilities are a likely cause for the fluctuations in the radiation from the 18 cm OH masers that have been reported to occur on time scales as short as 1000 s. The calculations are applicable to other types of astrophysical masers as well, and suggest that spontaneous emission will prevent similar instabilities in the H2O and SiO masers.

Near infrared photometry and analysis of OH maser stars of different types

We give results of near infrared observations of 17 stars of different OH maser types including their J, H and K magnitudes and fluxes. Their IRAS conterparts are identified. From a simultaneous analysis of their near infrared, far infrared and OH radio data we derive their near and far infrared luminosities L 1 and L 2, infrared gradients S 1, characteristics S 10 of the silicate 10 μ feature and the mass loss rate of the central star M ̇ . We found that, for all OH maser types, L 1, L 2, S 1 and S 10 all tend to increase with increasing mass loss rate. This shows that, for the red giants in the AGB sub-branch, there exists indeed a tightly connected evolutionary sequence from optical Mira stars to optically invisible OH/IR stars, from OH-1665/1667 masers to OH-1612 masers.