scholarly journals A population of galaxy-scale jets discovered using LOFAR

2020 ◽  
Vol 500 (4) ◽  
pp. 4921-4936
Author(s):  
B Webster ◽  
J H Croston ◽  
B Mingo ◽  
R D Baldi ◽  
B Barkus ◽  
...  
Keyword(s):  
Radio Emission ◽  
High Sensitivity ◽  
Large Field ◽  
High Angular Resolution ◽  
Radio Lobe ◽  
Central Regions ◽  
Order Of Magnitude ◽  
Current Sample ◽  
Effects Of Feedback ◽  
Host Properties

ABSTRACT The effects of feedback from high luminosity radio-loud active galactic nuclei (AGN) have been extensively discussed in the literature, but feedback from low-luminosity radio-loud AGN is less well understood. The advent of high sensitivity, high angular resolution, large field-of-view telescopes such as LOFAR is now allowing wide-area studies of such faint sources for the first time. Using the first data release of the LOFAR Two Metre Sky Survey (LoTSS) we report on our discovery of a population of 195 radio galaxies with 150-MHz luminosities between 3 × 1022 and 1.5 × 1025 WHz−1 and total radio emission no larger than 80 kpc. These objects, which we term galaxy-scale jets (GSJ), are small enough to be directly influencing the evolution of the host on galaxy scales. We report upon the typical host properties of our sample, finding that 9 per cent are hosted by spirals with the remainder being hosted by elliptical galaxies. Two of the spiral-hosted GSJ are highly unusual with low radio luminosities and FRII-like morphology. The host properties of our GSJ show that they are ordinary AGN observed at a stage in their life shortly after the radio emission has expanded beyond the central regions of the host. Based on our estimates, we find that about half of our GSJ have internal radio lobe energy within an order of magnitude of the ISM energy so that, even ignoring any possible shocks, GSJ are energetically capable of affecting the evolution of the host. The current sample of GSJ will grow in size with future releases of LoTSS and can also form the basis for further studies of feedback from low-luminosity radio sources.

scholarly journals Fast radio bursts to be detected with the Square Kilometre Array

2020 ◽  
Vol 497 (4) ◽  
pp. 4107-4116 ◽  
Author(s):  
Tetsuya Hashimoto ◽  
Tomotsugu Goto ◽  
Alvina Y L On ◽  
Ting-Yi Lu ◽  
Daryl Joe D Santos ◽  
...  
Keyword(s):  
Luminosity Function ◽  
Mass Density ◽  
Formation Rate ◽  
High Sensitivity ◽  
High Angular Resolution ◽  
Radio Bursts ◽  
Square Kilometre Array ◽  
Luminosity Functions ◽  
Radio Signals ◽  
Order Of Magnitude

ABSTRACT Fast radio bursts (FRBs) are mysterious extragalactic radio signals. Revealing their origin is one of the central foci in modern astronomy. Previous studies suggest that occurrence rates of non-repeating and repeating FRBs could be controlled by the cosmic stellar-mass density (CSMD) and cosmic star formation-rate density (CSFRD), respectively. The Square Kilometre Array (SKA) is one of the best future instruments to address this subject due to its high sensitivity and high-angular resolution. Here, we predict the number of FRBs to be detected with the SKA. In contrast to previous predictions, we estimate the detections of non-repeating and repeating FRBs separately, based on latest observational constraints on their physical properties including the spectral indices, FRB luminosity functions, and their redshift evolutions. We consider two cases of redshift evolution of FRB luminosity functions following either the CSMD or CSFRD. At $z$ ≳ 2, $z$ ≳ 6, and $z$ ≳ 10, non-repeating FRBs will be detected with the SKA at a rate of ∼104, ∼102, and ∼10 (sky−1 d−1), respectively, if their luminosity function follows the CSMD evolution. At $z$ ≳ 1, $z$ ≳ 2, and $z$ ≳ 4, sources of repeating FRBs will be detected at a rate of ∼103, ∼102, and ≲10 (sky−1 d−1), respectively, assuming that the redshift evolution of their luminosity function is scaled with the CSFRD. These numbers could change by about one order of magnitude depending on the assumptions on the CSMD and CSFRD. In all cases, abundant FRBs will be detected by the SKA, which will further constrain the luminosity functions and number density evolutions.

scholarly journals The MUSE Hubble Ultra Deep Field Survey

2017 ◽  
Vol 608 ◽  
pp. A2 ◽  
Author(s):  
H. Inami ◽  
R. Bacon ◽  
J. Brinchmann ◽  
J. Richard ◽  
T. Contini ◽  
...  
Keyword(s):  
High Sensitivity ◽  
Large Field ◽  
Success Rates ◽  
Redshift Distribution ◽  
Color Selection ◽  
Order Of Magnitude ◽  
Deep Fields ◽  
Hubble Ultra Deep Field ◽  
Blind Search ◽  
Magnitude Improvement

We have conducted a two-layered spectroscopic survey (1′ × 1′ ultra deep and 3′ × 3′ deep regions) in the Hubble Ultra Deep Field (HUDF) with the Multi Unit Spectroscopic Explorer (MUSE). The combination of a large field of view, high sensitivity, and wide wavelength coverage provides an order of magnitude improvement in spectroscopically confirmed redshifts in the HUDF; i.e., 1206 secure spectroscopic redshifts for Hubble Space Telescope (HST) continuum selected objects, which corresponds to 15% of the total (7904). The redshift distribution extends well beyond z> 3 and to HST/F775W magnitudes as faint as ≈ 30 mag (AB, 1σ). In addition, 132 secure redshifts were obtained for sources with no HST counterparts that were discovered in the MUSE data cubes by a blind search for emission-line features. In total, we present 1338 high quality redshifts, which is a factor of eight increase compared with the previously known spectroscopic redshifts in the same field. We assessed redshifts mainly with the spectral features [O ii] at z< 1.5 (473 objects) and Lyα at 2.9 <z< 6.7 (692 objects). With respect to F775W magnitude, a 50% completeness is reached at 26.5 mag for ultra deep and 25.5 mag for deep fields, and the completeness remains ≳ 20% up to 28–29 mag and ≈ 27 mag, respectively. We used the determined redshifts to test continuum color selection (dropout) diagrams of high-z galaxies. The selection condition for F336W dropouts successfully captures ≈ 80% of the targeted z ~ 2.7 galaxies. However, for higher redshift selections (F435W, F606W, and F775W dropouts), the success rates decrease to ≈ 20–40%. We empirically redefine the selection boundaries to make an attempt to improve them to ≈ 60%. The revised boundaries allow bluer colors that capture Lyα emitters with high Lyα equivalent widths falling in the broadbands used for the color-color selection. Along with this paper, we release the redshift and line flux catalog.

scholarly journals Cluster cosmology with the NIKA2 SZ Large Program

2020 ◽  
Vol 228 ◽  
pp. 00017 ◽  
Author(s):  
F. Mayet ◽  
R. Adam ◽  
P. Ade ◽  
P. André ◽  
A. Andrianasolo ◽  
...  
Keyword(s):  
Angular Resolution ◽  
High Redshift ◽  
High Sensitivity ◽  
Pressure Profile ◽  
Large Field ◽  
Limiting Factor ◽  
High Angular Resolution ◽  
Systematic Uncertainties ◽  
Large Program ◽  
Mean Pressure

The main limiting factor of cosmological analyses based on thermal Sunyaev-Zel’dovich (SZ) cluster statistics comes from the bias and systematic uncertainties that affect the estimates of the mass of galaxy clusters. High-angular resolution SZ observations at high redshift are needed to study a potential redshift or morphology dependence of both the mean pressure profile and of the mass-observable scaling relation used in SZ cosmological analyses. The NIKA2 camera is a new generation continuum instrument installed at the IRAM 30-m telescope. With a large field of view, a high angular resolution and a high-sensitivity, the NIKA2 camera has unique SZ mapping capabilities. In this paper, we present the NIKA2 SZ large program, aiming at observing a large sample of clusters at redshifts between 0.5 and 0.9, and the characterization of the first cluster oberved with NIKA2.

scholarly journals High-sensitivity radio study of the non-thermal stellar bow shock EB27

2021 ◽  
Author(s):  
Paula Benaglia ◽  
Santiago del Palacio ◽  
Christopher Hales ◽  
Marcelo E Colazo
Keyword(s):  
Radio Emission ◽  
Massive Star ◽  
High Sensitivity ◽  
Bow Shock ◽  
Relativistic Electrons ◽  
Polarimetric Observation ◽  
Very Large Array ◽  
Thermal Radio Emission ◽  
The Magnetic Field ◽  
Linear Polarisation

Abstract We present a deep radio-polarimetric observation of the stellar bow shock EB27 associated to the massive star BD+43○3654. This is the only stellar bow shock confirmed to have non-thermal radio emission. We used the Jansky Very Large Array in S band (2–4 GHz) to test whether this synchrotron emission is polarised. The unprecedented sensitivity achieved allowed us to map even the fainter regions of the bow shock, revealing that the more diffuse emission is steeper and the bow shock brighter than previously reported. No linear polarisation is detected in the bow shock above 0.5%, although we detected polarised emission from two southern sources, probably extragalactic in nature. We modeled the intensity and morphology of the radio emission to better constrain the magnetic field and injected power in relativistic electrons. Finally, we derived a set of more precise parameters for the system EB27–BD+43○3654 using Gaia Early Data Release 3, including the spatial velocity. The new trajectory, back in time, intersects the core of the Cyg OB2 association.

Research on Adaptive Current Protection of Wind Farm

2012 ◽  
Vol 260-261 ◽  
pp. 257-262
Author(s):  
Feng Ting Li ◽  
Chang Sheng Su
Keyword(s):  
Wind Farm ◽  
Short Circuit ◽  
High Sensitivity ◽  
Short Circuit Current ◽  
Phase Selection ◽  
Wind Generators ◽  
Attenuation Characteristic ◽  
Sample Data ◽  
Dc Component ◽  
Current Sample

In allusion to the problems of convention current protection when it was used to collect circuit of wind farm, the relay protection should consider the short-circuit current of wind generators; The principle of adaptive current protection was described, the fault current and attenuation characteristic of asynchronous wind generator was studied, the scheme of adaptive current protection was proposed for wind farm operation. Taking PSCAD/EMTDC as the platform, simulation and record the voltage and current sample-data of different wind farm operation which can guarantee high sensitivity phase selection, the high accuracy wind generators impedance measure method based on FFT filter DC component is presented , and using MATLAB program achieved the scheme of adaptive current protection. Simulation results demonstrate that collect circuit adaptive current protection is adaptive wind farm operation model, and enhance the operation benefit of wind farm.

scholarly journals Waveguide combiners for mixed reality headsets: a nanophotonics design perspective

Nanophotonics ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 41-74
Author(s):  
Bernard C. Kress ◽  
Ishan Chatterjee
Keyword(s):  
Visual Perception ◽  
Mixed Reality ◽  
Deep Understanding ◽  
Large Field ◽  
High Angular Resolution ◽  
List Type ◽  
Human Visual Perception ◽  
Perception System ◽  
Social Comfort ◽  
Hardware Architectures

AbstractThis paper is a review and analysis of the various implementation architectures of diffractive waveguide combiners for augmented reality (AR), mixed reality (MR) headsets, and smart glasses. Extended reality (XR) is another acronym frequently used to refer to all variants across the MR spectrum. Such devices have the potential to revolutionize how we work, communicate, travel, learn, teach, shop, and are entertained. Already, market analysts show very optimistic expectations on return on investment in MR, for both enterprise and consumer applications. Hardware architectures and technologies for AR and MR have made tremendous progress over the past five years, fueled by recent investment hype in start-ups and accelerated mergers and acquisitions by larger corporations. In order to meet such high market expectations, several challenges must be addressed: first, cementing primary use cases for each specific market segment and, second, achieving greater MR performance out of increasingly size-, weight-, cost- and power-constrained hardware. One such crucial component is the optical combiner. Combiners are often considered as critical optical elements in MR headsets, as they are the direct window to both the digital content and the real world for the user’s eyes.Two main pillars defining the MR experience are comfort and immersion. Comfort comes in various forms: –wearable comfort—reducing weight and size, pushing back the center of gravity, addressing thermal issues, and so on–visual comfort—providing accurate and natural 3-dimensional cues over a large field of view and a high angular resolution–vestibular comfort—providing stable and realistic virtual overlays that spatially agree with the user’s motion–social comfort—allowing for true eye contact, in a socially acceptable form factor.Immersion can be defined as the multisensory perceptual experience (including audio, display, gestures, haptics) that conveys to the user a sense of realism and envelopment. In order to effectively address both comfort and immersion challenges through improved hardware architectures and software developments, a deep understanding of the specific features and limitations of the human visual perception system is required. We emphasize the need for a human-centric optical design process, which would allow for the most comfortable headset design (wearable, visual, vestibular, and social comfort) without compromising the user’s sense of immersion (display, sensing, and interaction). Matching the specifics of the display architecture to the human visual perception system is key to bound the constraints of the hardware allowing for headset development and mass production at reasonable costs, while providing a delightful experience to the end user.

STEM multiplication nano-moiré method with large field of view and high sensitivity

2021 ◽  
Author(s):  
Yao Zhao ◽  
Dongliang Wu ◽  
Jiangfan Zhou ◽  
Huihui Wen ◽  
Zhanwei Liu ◽  
...  
Keyword(s):  
High Sensitivity ◽  
Field Of View ◽  
Large Field ◽  
Moire Method

scholarly journals Pulsar observations at millimetre wavelengths

2017 ◽  
Vol 13 (S337) ◽  
pp. 92-95
Author(s):  
Pablo Torne
Keyword(s):  
Radio Emission ◽  
Low Frequency ◽  
High Sensitivity ◽  
Small Sample ◽  
Galactic Centre ◽  
New Era ◽  
Radio Frequencies ◽  
Radio Band ◽  
First Time ◽  
Strong Scattering

AbstractDetecting and studying pulsars above a few GHz in the radio band is challenging due to the typical faintness of pulsar radio emission, their steep spectra, and the lack of observatories with sufficient sensitivity operating at high frequency ranges. Despite the difficulty, the observations of pulsars at high radio frequencies are valuable because they can help us to understand the radio emission process, complete a census of the Galactic pulsar population, and possibly discover the elusive population in the Galactic Centre, where low-frequency observations have problems due to the strong scattering. During the decades of the 1990s and 2000s, the availability of sensitive instrumentation allowed for the detection of a small sample of pulsars above 10 GHz, and for the first time in the millimetre band. Recently, new attempts between 3 and 1 mm (≈86 − 300 GHz) have resulted in the detections of a pulsar and a magnetar up to the highest radio frequencies to date, reaching 291 GHz (1.03 mm). The efforts continue, and the advent of new or upgraded millimetre facilities like the IRAM 30-m, NOEMA, the LMT, and ALMA, warrants a new era of high-sensitivity millimetre pulsar astronomy in the upcoming years.

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