Efficient injection from large telescopes into single-mode fibres: Enabling the era of ultra-precision astronomy

Photonic technologies offer numerous advantages for astronomical instruments such as spectrographs and interferometers owing to their small footprints and diverse range of functionalities. Operating at the diffraction-limit, it is notoriously difficult to efficiently couple such devices directly with large telescopes. We demonstrate that with careful control of both the non-ideal pupil geometry of a telescope and residual wavefront errors, efficient coupling with single-mode devices can indeed be realised. A fibre injection was built within the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) instrument. Light was coupled into a single-mode fibre operating in the near-IR (J-H bands) which was downstream of the extreme adaptive optics system and the pupil apodising optics. A coupling efficiency of 86% of the theoretical maximum limit was achieved at 1550 nm for a diffraction-limited beam in the laboratory, and was linearly correlated with Strehl ratio. The coupling efficiency was constant to within <30% in the range 1250-1600 nm. Preliminary on-sky data with a Strehl ratio of 60% in the H-band produced a coupling efficiency into a single-mode fibre of ~50%, consistent with expectations. The coupling was >40% for 84% of the time and >50% for 41% of the time. The laboratory results allow us to forecast that extreme adaptive optics levels of correction (Strehl ratio >90% in H-band) would allow coupling of >67% (of the order of coupling to multimode fibres currently). For Strehl ratios <20%, few-port photonic lanterns become a superior choice but the signal-to-noise must be considered. These results illustrate a clear path to efficient on-sky coupling into a single-mode fibre, which could be used to realise modal-noise-free radial velocity machines, very-long-baseline optical/near-IR interferometers and/or simply exploit photonic technologies in future instrument design.Comment: 15 pages, 16 figures, 1 table, published in A&

A multiple scales approach to crack front waves

Perturbation of a propagating crack with a straight edge is solved using the method of matched asymptotic expansions (MAE). This provides a simplified analysis in which the inner and outer solutions are governed by distinct mechanics. The inner solution contains the explicit perturbation and is governed by a quasi-static equation. The outer solution determines the radiation of energy away from the tip, and requires solving dynamic equations in the unperturbed configuration. The outer and inner expansions are matched via the small parameter L/l defined by the disparate length scales: the crack perturbation length L and the outer length scale l associated with the loading. The method is first illustrated for a scalar crack model and then applied to the elastodynamic mode I problem. The dispersion relation for crack front waves is found by requiring that the energy release rate is unaltered under perturbation. The wave speed is calculated as a function of the nondimensional parameter kl where k is the crack front wavenumber, and dispersive properties of the crack front wave speed are described for the first time. The example problems considered here demonstrate that the potential of using MAE for moving boundary value problems with multiple scales.Comment: 25 pages, 5 figure

Radio Galaxy Zoo: Knowledge Transfer Using Rotationally Invariant Self-Organising Maps

With the advent of large scale surveys the manual analysis and classification of individual radio source morphologies is rendered impossible as existing approaches do not scale. The analysis of complex morphological features in the spatial domain is a particularly important task. Here we discuss the challenges of transferring crowdsourced labels obtained from the Radio Galaxy Zoo project and introduce a proper transfer mechanism via quantile random forest regression. By using parallelized rotation and flipping invariant Kohonen-maps, image cubes of Radio Galaxy Zoo selected galaxies formed from the FIRST radio continuum and WISE infrared all sky surveys are first projected down to a two-dimensional embedding in an unsupervised way. This embedding can be seen as a discretised space of shapes with the coordinates reflecting morphological features as expressed by the automatically derived prototypes. We find that these prototypes have reconstructed physically meaningful processes across two channel images at radio and infrared wavelengths in an unsupervised manner. In the second step, images are compared with those prototypes to create a heat-map, which is the morphological fingerprint of each object and the basis for transferring the user generated labels. These heat-maps have reduced the feature space by a factor of 248 and are able to be used as the basis for subsequent ML methods. Using an ensemble of decision trees we achieve upwards of 85.7% and 80.7% accuracy when predicting the number of components and peaks in an image, respectively, using these heat-maps. We also question the currently used discrete classification schema and introduce a continuous scale that better reflects the uncertainty in transition between two classes, caused by sensitivity and resolution limits

SCORPIO-II: Spectral indices of weak Galactic radio sources

In the next few years the classification of radio sources observed by the large surveys will be a challenging problem, and spectral index is a powerful tool for addressing it. Here we present an algorithm to estimate the spectral index of sources from multiwavelength radio images. We have applied our algorithm to SCORPIO (Umana et al. 2015), a Galactic Plane survey centred around 2.1 GHz carried out with ATCA, and found we can measure reliable spectral indices only for sources stronger than 40 times the rms noise. Above a threshold of 1 mJy, the source density in SCORPIO is 20 percent greater than in a typical extra-galactic field, like ATLAS (Norris et al. 2006), because of the presence of Galactic sources. Among this excess population, 16 sources per square degree have a spectral index of about zero, suggesting optically thin thermal emission such as Hii regions and planetary nebulae, while 12 per square degree present a rising spectrum, suggesting optically thick thermal emission such as stars and UCHii regions.Comment: 12 pages, 11 figures, accepted by MNRA

Southern Massive Stars at High Angular Resolution: Observational Campaign and Companion Detection

Multiplicity is one of the most fundamental observable properties of massive O-type stars and offers a promising way to discriminate between massive star formation theories. Nevertheless, companions at separations between 1 and 100 mas remain mostly unknown due to intrinsic observational limitations. [...] The Southern MAssive Stars at High angular resolution survey (SMASH+) was designed to fill this gap by providing the first systematic interferometric survey of Galactic massive stars. We observed 117 O-type stars with VLTI/PIONIER and 162 O-type stars with NACO/SAM, respectively probing the separation ranges 1-45 and 30-250mas and brightness contrasts of Delta H < 4 and Delta H < 5. Taking advantage of NACO's field-of-view, we further uniformly searched for visual companions in an 8''-radius down to Delta H = 8. This paper describes the observations and data analysis, reports the discovery of almost 200 new companions in the separation range from 1mas to 8'' and presents the catalog of detections, including the first resolved measurements of over a dozen known long-period spectroscopic binaries. Excluding known runaway stars for which no companions are detected, 96 objects in our main sample (DEC < 0 deg; H<7.5) were observed both with PIONIER and NACO/SAM. The fraction of these stars with at least one resolved companion within 200mas is 0.53. Accounting for known but unresolved spectroscopic or eclipsing companions, the multiplicity fraction at separation < 8'' increases to f_m = 0.91 +/- 0.03. The fraction of luminosity class V stars that have a bound companion reaches 100% at 30mas while their average number of physically connected companions within 8'' is f_c = 2.2 +/- 0.3. This demonstrates that massive stars form nearly exclusively in multiple systems. Additionally, the nine non-thermal (NT) radio emitters observed by SMASH+ are all resolved [...]Comment: 57 pages, 20 figures, 7 tables; accepted for publication in ApJ

Radio Galaxy Zoo: The Distortion of Radio Galaxies by Galaxy Clusters

We study the impact of cluster environment on the morphology of a sample of 4304 extended radio galaxies from Radio Galaxy Zoo. A total of 87% of the sample lies within a projected 15 Mpc of an optically identified cluster. Brightest cluster galaxies (BCGs) are more likely than other cluster members to be radio sources, and are also moderately bent. The surface density as a function of separation from cluster center of non-BCG radio galaxies follows a power law with index $-1.10\pm 0.03$ out to $10~r_{500}$ ($\sim 7~$Mpc), which is steeper than the corresponding distribution for optically selected galaxies. Non-BCG radio galaxies are statistically more bent the closer they are to the cluster center. Within the inner $1.5~r_{500}$ ($\sim 1~$Mpc) of a cluster, non-BCG radio galaxies are statistically more bent in high-mass clusters than in low-mass clusters. Together, we find that non-BCG sources are statistically more bent in environments that exert greater ram pressure. We use the orientation of bent radio galaxies as an indicator of galaxy orbits and find that they are preferentially in radial orbits. Away from clusters, there is a large population of bent radio galaxies, limiting their use as cluster locators; however, they are still located within statistically overdense regions. We investigate the asymmetry in the tail length of sources that have their tails aligned along the radius vector from the cluster center, and find that the length of the inward-pointing tail is weakly suppressed for sources close to the center of the cluster.Comment: 23 pages, 17 figures, 2 tables. Supplemental data files available in The Astronomical Journal or contact autho

Interferometric Observations of the Nuclear Region of Arp220 at Submillimeter Wavelengths

We report the first submillimeter interferometric observations of an ultraluminous infrared galaxy. We observed Arp220 in the CO J=3-2 line and 342GHz continuum with the single baseline CSO-JCMT interferometer consisting of the Caltech Submillimeter Observatory (CSO) and the James Clerk Maxwell Telescope (JCMT). Models were fit to the measured visibilities to constrain the structure of the source. The morphologies of the CO J=3-2 line and 342GHz continuum emission are similar to those seen in published maps at 230 and 110GHz. We clearly detect a binary source separated by about 1 arcsec in the east-west direction in the 342GHz continuum. The CO J=3-2 visibility amplitudes, however, indicate a more complicated structure, with evidence for a compact binary at some velocities and rather more extended structure at others. Less than 30% of the total CO J=3-2 emission is detected by the interferometer, which implies the presence of significant quantities of extended gas. We also obtained single-dish CO J=2-1, CO J=3-2 and HCN J=4-3 spectra. The HCN J=4-3 spectrum, unlike the CO spectra, is dominated by a single redshifted peak. The HCN J=4-3/CO J=3-2, HCN J=4-3/HCN J=1-0 and CO J=3-2/2-1 line ratios are larger in the redshifted (eastern) source, which suggests that the two sources may have different physical conditions. This result might be explained by the presence of an intense starburst that has begun to deplete or disperse the densest gas in the western source, while the eastern source harbors undispersed high density gas.Comment: 17 pages, 9 figures, 4 Tables. accepted by Ap

Resposta de Astragalus sinicus L. (Astrágalo chinês) ao calcário e a inoculação

An experiment utilizing two varieties (Taiwan and Japan) of Astragalus sinicus, to test their potencial as a green manure crop for the winter periods between crops of paddy rice, was conduced in the rice experiment area of the Estação Experimental Theodureto de Camargo of the Instituto Agronômico de Campinas. Because of the highly specialized nature of Astragalus in regard to high calcium status and high rhizobial strain specificity, the trial was conducted with and without liming and with three variations of inoculation: 1) no inoculation, 2) peat culture inoculation and 3) inoculation with the addition of a pellet of CaCO3, using gum arabic as adhesive. Growth of Astragalus sinicus was not good on this acid soil even with added fertilizer and lime, although these treatments did increase yield. Nodulation was absent without inoculation. Nodulation by the peat culture method varied from 21 to 60 percent, with the higher figures ocurring under lime treatment. The best treatment was pelleting and liming with a high of 86 percent of the plants nodulated. In general, it would seem that Astragalus sinicus is unlikely to be of much use on very acid rice soils. The trial demonstrated very satisfactorily the benefit to be gained with specialized legumes from the simple process of lime pelleting the seed after inoculation.Astragalus sinicus foi cultivado num solo ácido de arroz, para testar seu potencial como uma cultura de esterco verde, entre culturas de arroz inundado. O crescimento dessa leguminosa altamente especializada não foi satisfatório neste solo. A inoculação pelos métodos normais induziu a nodulação, todavia, obteve-se maior nodulação com a inoculação e também um revestimento de CaCOa. Apenas a calagem não induziu a nodulação, sem inoculação, mas aumentou a nodulação sob os tratamentos de inoculação. Os rendimentos de matéria seca foram maiores com calagem e inoculação mais revestimento de CaCOa. A germinação não foi afetada peio tratamento de revestimento

The closest elastic tensor of arbitrary symmetry to an elasticity tensor of lower symmetry

The closest tensors of higher symmetry classes are derived in explicit form for a given elasticity tensor of arbitrary symmetry. The mathematical problem is to minimize the elastic length or distance between the given tensor and the closest elasticity tensor of the specified symmetry. Solutions are presented for three distance functions, with particular attention to the Riemannian and log-Euclidean distances. These yield solutions that are invariant under inversion, i.e., the same whether elastic stiffness or compliance are considered. The Frobenius distance function, which corresponds to common notions of Euclidean length, is not invariant although it is simple to apply using projection operators. A complete description of the Euclidean projection method is presented. The three metrics are considered at a level of detail far greater than heretofore, as we develop the general framework to best fit a given set of moduli onto higher elastic symmetries. The procedures for finding the closest elasticity tensor are illustrated by application to a set of 21 moduli with no underlying symmetry.Comment: 48 pages, 1 figur

Incorporação de matéria orgânica (“mulching”) e aplicação de péletes de calcário (“pelleting”) para testar estirpes de Rhizobium em experimentos de campo sob condições tropicais

Two field experiments were conducted in the State of São Paulo, Brazil, to study the effect of soil and inoculation treatments on the nodulation and yields of the four legume species Glycine javanica, Teramnus uncinatus, Medicago sativa and Phaseolus vulgaris. Four Rhizobium strains were compared on each species. Three inoculation treatments were used, nil, peat applied with 10% sucrose, and peat applied with 45% gum arabic followed by lime pelleting. All treatments were replicated on mulched and unmulched soil. Mulching consisted of incorporating sugar cane bagasse into the soil surface. The technique of using mulch to tie up soil nitrogen proved to be an effective way of demonstrating differences in nitrogen fixing effectiveness of the Rhizobium strains in the field. It was also an efficient method of weed control. The technique of lime pelleting was shown to be of great use in promoting nodulation on the specialized species Medicago sativa and Phaseolus vulgaris. However, it had no effect on Teramnus uncinatus and only a very slight effect on Glycine javanica. The many differences in response of the various legume-Rhizobium combinations to mulch and inoculation treatment emphasizes the danger of drawing broad conclusions from experiments using only one combination. The potentials of mulching and pelleting are discussed with particular reference to the symbiotic specificity of the legume species under test.Dois experimentos de campo foram conduzidos no Estado de São Paulo, Brasil, com o objetivo de se estudar o efeito do solo e da inoculação na nodulação e na produção das quatro leguminosas Glycine javanica, Teramnus uncinatus, Medicago sativa e Phaseolus vulgaris. Quatro estirpes de Rhizobium para cada leguminosa foram testadas. Os seguintes tratamentos de inoculação foram feitos: testemunha sem inoculação; inoculação normal com turfa, utilizando-se uma solução de sacarose a 10% como adesivo; e peletização, sendo o inoculante turfoso aderido com uma solução de goma arábica a 45% e revestido com calcário. Todos os tratamentos foram comparados em solos com e sem a incorporação de matéria orgânica, que consistiu de bagacilho de cana. A técnica de incorporação da matéria orgânica para imobilizar os nitratos do solo mostrou-se eficaz no sentido de permitir detectar diferenças na capacidade de fixação de nitrogênio de diferentes estirpes de Rhizobium, bem como no contrôle de ervas daninhas. A técnica de peletização com calcário mostrou-se vantajosa em promover nodulação das espécies Medicago sativa e Phaseolus vulgaris, de alta especialização simbiótica, mas sem efeito em Teramnus uncinatus, e de pouca eficácia em Glycine javanica. As várias combinações Rhizobium-leguminosa, ou mesmo uma determinada leguminosa, responderam diferentemente aos tratamentos de incorporação de matéria orgânica e de inoculação, mostrando o perigo de se tirar conclusões gerais de experimentos com apenas uma determinada combinação. As potencialidades de uso da técnica de incorporação de matéria orgânica e da peletização são discutidas com referência especial à especificidade simbiótica das leguminosas testadas