New continuum and polarization observations of the Cygnus Loop with FAST I. Data processing and verification

We report on the continuum and polarization observations of the Cygnus Loop supernova remnant (SNR) conducted by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). FAST observations provide high angular resolution and high sensitivity images of the SNR, which will help to disentangle its nature. We obtained Stokes I, Q and U maps over the frequency range of 1.03 – 1.46 GHz split into channels of 7.63 kHz. The original angular resolution is in the range of ∼ 3 ′ − ∼ 3 ′ .8 , and we combined all the data at a common resolution of 4 ′ . The temperature scale of the total intensity and the spectral index from the in-band temperature-temperature plot are consistent with previous observations, which validates the data calibration and map-making procedures. The rms sensitivity for the band-averaged total-intensity map is about 20 mK in brightness temperature, which is at the level of confusion limit. For the first time, we apply rotation measure (RM) synthesis to the Cygnus Loop to obtain the polarization intensity and RM maps. The rms sensitivity for polarization is about 5 mK, far below the total-intensity confusion limit. We also obtained RMs of eight extragalactic sources, and demonstrate that the wide-band frequency coverage helps to overcome the ambiguity of RM determinations.

Broadband Terahertz Photonic Integrated Circuit with Integrated Active Photonic Devices

Present-day photonic terahertz (100 GHz–10 THz) systems offer dynamic ranges beyond 100 dB and frequency coverage beyond 4 THz. They yet predominantly employ free-space Terahertz propagation, lacking integration depth and miniaturisation capabilities without sacrificing their extreme frequency coverage. In this work, we present a high resistivity silicon-on-insulator-based multimodal waveguide topology including active components (e.g., THz receivers) as well as passive components (couplers/splitters, bends, resonators) investigated over a frequency range of 0.5–1.6 THz. The waveguides have a single mode bandwidth between 0.5–0.75 THz; however, above 1 THz, these waveguides can be operated in the overmoded regime offering lower loss than commonly implemented hollow metal waveguides, operated in the fundamental mode. Supported by quartz and polyethylene substrates, the platform for Terahertz photonic integrated circuits (Tera-PICs) is mechanically stable and easily integrable. Additionally, we demonstrate several key components for Tera-PICs: low loss bends with radii ∼2 mm, a Vivaldi antenna-based efficient near-field coupling to active devices, a 3-dB splitter and a filter based on a whispering gallery mode resonator.

Qualitative analysis for coverage probability and energy efficiency in cognitive-femtocell networks under macrocell infrastructure

<div>The network coverage and energy efficiency issues in heterogeneous cognitive-femtocell networks over the macrocell network is studied. Cognitive functions in wireless network nodes are serviceable with the macrocell infrastructure to achieve a balance between two desirable</div><div>but incompatible features: coverage and energy efficiency. There are two basic but related aspects of cognitive radios (CRs) in the context of wireless communications: optimum CRs for energy efficiency and the act of the functioning of CRs with energy efficiency. To fully utilise the cognitive capability, a dual-tier network architecture is assumed where both the macrocell and the femtocell have a bearing</div><div>on the cognitive capability. Owing to the salient features of femtocells, they can improve the coverage and enhance the spectrum efficiency by reutilising the frequency spectrum allocated to the macrocell, although, the resulting intercell interference accompanied by the same frequency coverage cannot be underestimated. The effectiveness of the scheme is verified by extensive Matlab simulation.</div>

Qualitative analysis for coverage probability and energy efficiency in cognitive-femtocell networks under macrocell infrastructure

<div>The network coverage and energy efficiency issues in heterogeneous cognitive-femtocell networks over the macrocell network is studied. Cognitive functions in wireless network nodes are serviceable with the macrocell infrastructure to achieve a balance between two desirable</div><div>but incompatible features: coverage and energy efficiency. There are two basic but related aspects of cognitive radios (CRs) in the context of wireless communications: optimum CRs for energy efficiency and the act of the functioning of CRs with energy efficiency. To fully utilise the cognitive capability, a dual-tier network architecture is assumed where both the macrocell and the femtocell have a bearing</div><div>on the cognitive capability. Owing to the salient features of femtocells, they can improve the coverage and enhance the spectrum efficiency by reutilising the frequency spectrum allocated to the macrocell, although, the resulting intercell interference accompanied by the same frequency coverage cannot be underestimated. The effectiveness of the scheme is verified by extensive Matlab simulation.</div>

Yebes 40 m radio telescope and the broad band Nanocosmos receivers at 7 mm and 3 mm for line surveys

Context. Yebes 40 m radio telescope is the main and largest observing instrument at Yebes Observatory and is devoted to very long baseline interferometry (VLBI) and single-dish observations since 2010. It has been covering frequency bands between 2 GHz and 90 GHz in discontinuous and narrow windows in most cases in order to match the current needs of the European VLBI Network (EVN) and the Global Millimeter VLBI Array (GMVA). Aims. The Nanocosmos project, a European Union-funded synergy grant, has enabled an increase in the instantaneous frequency coverage of the Yebes 40 m radio telescope, making it possible to observe many molecular transitions with single tunings in single-dish mode. This reduces the observing time and maximises the output from the telescope. Methods. We present technical specifications of the recently installed 31.5−50 GHz (Q band) and 72−90.5 GHz (W band) receivers along with the main characteristics of the telescope at these frequency ranges. We observed IRC+10216, CRL 2688, and CRL 618, which harbour a rich molecular chemistry, to demonstrate the capabilities of the new instrumentation for spectral observations in single-dish mode. Results. Our results show the high sensitivity of the telescope in the Q band. The spectrum of IRC+10126 offers an unprecedented signal-to-noise ratio for this source in this band. On the other hand, the spectrum normalised by the continuum flux towards CRL 618 in the W band demonstrates that the 40 m radio telescope produces comparable results to those from the IRAM 30 m radio telescope, although with a lower sensitivity. The new receivers fulfil one of the main goals of Nanocosmos and open up the possibility to study the spectrum of different astrophysical media with unprecedented sensitivity.

Low-frequency integrated radio spectra of diffuse, steep-spectrum sources in galaxy clusters: palaeontology with the MWA and ASKAP

Galaxy clusters have been found to host a range of diffuse, non-thermal emission components, generally with steep, power law spectra. In this work we report on the detection and follow-up of radio halos, relics, remnant radio galaxies, and other fossil radio plasmas in Southern Sky galaxy clusters using the Murchison Widefield Array and the Australian Square Kilometre Array Pathfinder. We make use of the frequency coverage between the two radio interferometers—from 88 to $\sim\!900$ MHz—to characterise the integrated spectra of these sources within this frequency range. Highlights from the sample include the detection of a double relic system in Abell 3186, a mini-halo in RXC J0137.2–0912, a candidate halo and relic in Abell 3399, and a complex multi-episodic head-tail radio galaxy in Abell 3164. We compare this selection of sources and candidates to the literature sample, finding sources consistent with established radio power–cluster mass scaling relations. Finally, we use the low-frequency integrated spectral index, $\alpha$ ( $S_v \propto v^\alpha$ ), of the detected sample of cluster remnants and fossil sources to compare with samples of known halos, relics, remnants and fossils to investigate a possible link between their electron populations. We find the distributions of $\alpha$ to be consistent with relic and halo emission generated by seed electrons that originated in fossil or remnant sources. However, the present sample sizes are insufficient to rule out other scenarios.

Dominant Loss Mechanisms of Whispering Gallery Mode RF-MEMS Resonators with Wide Frequency Coverage

This work investigates the dominant energy dissipations of the multi-frequency whispering gallery mode (WGM) resonators to provide an insight into the loss mechanisms of the devices. An extensive theory for each loss source was established and experimentally testified. The squeezed film damping (SFD) is a major loss for all the WGMs at atmosphere, which is distinguished from traditional bulk acoustic wave (BAW) resonators where the high-order modes suffer less from the air damping. In vacuum, the SFD is negligible, and the frequency-dependent Akhiezer damping (AKE) has significant effects on different order modes. For low-order WGMs, the AKE is limited, and the anchor loss behaves as the dominant loss. For high-order modes with an extended nodal region, the anchor loss is reduced, and the AKE determines the Q values. Substantial Q enhancements over four times and an excellent f × Q product up to 6.36 × 1013 at 7 K were achieved.

High-redshift star formation in the Atacama large millimetre/submillimetre array era

The Atacama Large Millimetre/submillimetre Array (ALMA) is currently in the process of transforming our view of star-forming galaxies in the distant ( z ≳ 1 ) universe. Before ALMA, most of what we knew about dust-obscured star formation in distant galaxies was limited to the brightest submillimetre sources—the so-called submillimetre galaxies (SMGs)—and even the information on those sources was sparse, with resolved (i.e. sub-galactic) observations of the obscured star formation and gas reservoirs typically restricted to the most extreme and/or strongly lensed sources. Starting with the beginning of early science operations in 2011, the last 9 years of ALMA observations have ushered in a new era for studies of high-redshift star formation. With its long baselines, ALMA has allowed observations of distant dust-obscured star formation with angular resolutions comparable to—or even far surpassing—the best current optical telescopes. With its bandwidth and frequency coverage, it has provided an unprecedented look at the associated molecular and atomic gas in these distant galaxies through targeted follow-up and serendipitous detections/blind line scans. Finally, with its leap in sensitivity compared to previous (sub-)millimetre arrays, it has enabled the detection of these powerful dust/gas tracers much further down the luminosity function through both statistical studies of colour/mass-selected galaxy populations and dedicated deep fields. We review the main advances ALMA has helped bring about in our understanding of the dust and gas properties of high-redshift ( z ≳ 1 ) star-forming galaxies during these first 9 years of its science operations, and we highlight the interesting questions that may be answered by ALMA in the years to come.

Pure Rotational Spectrum of Benzophenone Detected by Broadband Microwave Spectrometer in the 2–8 GHz Range

The investigation on microwave spectrum of benzophenone was conducted with a recently constructed broadband chirped-pulse Fourier transform microwave spectrometer with a heating nozzle in the 2–8 GHz range. In this work, 138 b-type pure rotational transitions were assigned to bridge the measuring gap in the microwave region. The rotational constants for benzophenone were accurately determined by a combined microwave data fitting with frequency coverage between 2–14 GHz and have the following values: A = 1692.8892190(119) MHz, B = 412.6446602(43) MHz and C = 353.8745644(43) MHz.