Broadband Filters Research Articles

Geometric Albedos at Short Optical Wavelengths for the Hot Jupiters WASP-43b, WASP-103b, and TrES-3b

The largest and most close-in exoplanets would reflect enough starlight to enable its ground-based photometric detection under the condition of a high to moderate albedo. We present the results of an observing campaign of secondary eclipse light curves of three of the most suitable exoplanet targets, WASP-43b, WASP-103b, and TrES-3b. The observations were conducted with meter-sized telescopes in the blue optical broadband filters Johnson B and Johnson V. We do not detect a photometric dimming at the moment of the eclipse, and derive a best-fit eclipse depth by an injection-recovery test. These depth values are then used to infer low geometric albedos ranging from zero to 0.18 with an uncertainty of 0.12 or better in most cases. This work illustrates the potential of ground-based telescopes to provide wavelength-resolved reflection properties of selected exoplanets even at short optical wavelengths, which otherwise are only accessible by the Hubble Space Telescope.

WALOP-South: a four-camera one-shot imaging polarimeter for PASIPHAE survey. Paper II – polarimetric modeling and calibration

The Wide-Area Linear Optical Polarimeter (WALOP)-South instrument is an upcoming wide-field and high-accuracy optical polarimeter to be used as a survey instrument for carrying out the Polar-Areas Stellar Imaging in Polarization High Accuracy Experiment (PASIPHAE) program. Designed to operate as a one-shot four-channel and four-camera imaging polarimeter, it will have a field of view of $35\times 35$ arcminutes and will measure the Stokes parameters $I$, $q$, and $u$ in a single exposure in the SDSS-r broadband filter. The design goal for the instrument is to achieve an overall polarimetric measurement accuracy of 0.1 % over the entire field of view. We present here the complete polarimetric modeling of the instrument, characterizing the amount and sources of instrumental polarization. To accurately retrieve the real Stokes parameters of a source from the measured values, we have developed a calibration method for the instrument. Using this calibration method and simulated data, we demonstrate how to correct instrumental polarization and obtain 0.1 % accuracy in the degree of polarization, $p$. Additionally, we tested and validated the calibration method by implementing it on a table-top WALOP-like test-bed polarimeter in the laboratory.

The Connotation and Construction Path of the Principle of Good Faith from the Perspective of Civil and Commercial Law

In order to explore the connotation and construction path of the principle of good faith from the perspective of civil and commercial law, this paper combines intelligent algorithms to analyze the connotation and construction path of the principle of good faith from the perspective of civil and commercial law. Moreover, this paper presents a topology network specially used to improve the energy absorption efficiency of the isolation resistor used in the power divider and theoretically analyzes the effectiveness of the isolation topology. In addition, this paper further optimizes the topology of the two-way broadband filter power divider and builds a simulation model based on the basic content of the principle of good faith. From the research results, the simulation model proposed in this paper can play a certain role in the connotation and construction path of the principle of good faith from the perspective of civil and commercial law. On this basis, some suggestions on the connotation and construction path of the principle of good faith are put forward.

CaSSIS-based stereo products for Mars after three years in orbit

The Colour and Stereo Surface Imaging System (CaSSIS) on board the ExoMars Trace Gas Orbiter (TGO), operating in push-frame mode, provides multiband images at four different wavelengths thanks to a Filter Strip Assembly with a panchromatic filter and three broadband filters within the visible and near infrared range. The camera acquires stereo pairs fundamental for the initialization of the photogrammetric process to perform three-dimensional reconstruction of the Martian surface at the best resolution of 4.6 m per pixel for regions up to ∼400 km2 in one imaging sequence.

UV to submillimetre luminosity functions of TNG50 galaxies

ABSTRACT We apply the radiative transfer (RT) code skirt on a sample of ${\sim } 14\, 000$ low-redshift (z ≤ 0.1) galaxies extracted from the TNG50 simulation to enable an apples-to-apples comparison with observations. The RT procedure is calibrated via comparison of a subsample of TNG50 galaxies with the DustPedia observational sample: we compare several luminosity and colour scaling relations and spectral energy distributions in different specific SFR bins. We consistently derive galaxy luminosity functions for the TNG50 simulation in 14 broad-band filters from UV to submillimetre wavelengths and investigate the effects of the aperture, orientation, radiative transfer recipe, and numerical resolution. We find that, while our TNG50+RT fiducial model agrees well with the observed luminosity functions at the knee (±0.04 dex typical agreement), the TNG50 + RT luminosity functions evaluated within $5\, R_{1/2}$ are generally higher than observed at both the faint and bright ends, by 0.004 (total IR)-0.27 (UKIDSS H) dex and 0.12 (SPIRE250)-0.8 (GALEX FUV) dex, respectively. A change in the aperture does affect the bright end of the luminosity function, easily by up to 1 dex depending on the choice. However, we also find that the galaxy luminosity functions of a worse-resolution run of TNG50 (TNG50-2, with eight times worse mass resolution than TNG50, similar to TNG100) are in better quantitative agreement with observational constraints. Finally, we publicly release the photometry for the TNG50 sample in 53 broad-bands from FUV to submillimetre, in three orientations and four apertures, as well as galaxy spectral energy distributions.

Tapered photonic switching

Abstract The advent of novel nonlinear materials has stirred unprecedented interest in exploring the use of temporal inhomogeneities to achieve novel forms of wave control, amidst the greater vision of engineering metamaterials across both space and time. When the properties of an unbounded medium are abruptly switched in time, propagating waves are efficiently converted to different frequencies, and partially coupled to their back-propagating phase-conjugate partners, through a process called time-reversal. However, in realistic materials the switching time is necessarily finite, playing a central role in the resulting temporal scattering features. By identifying and leveraging the crucial role of electromagnetic momentum conservation in time-reversal processes, here we develop a general analytical formalism to quantify time-reversal due to temporal inhomogeneities of arbitrary profile. We deploy our theory to develop a formalism, dual to spatial tapering, that enables the tailoring of a desired time-reversal spectral response, demonstrating its use for the realization of broadband frequency converters and filters.

Aperture polarimetry of selected comets in 2018–2020: Observations and computer simulation

Polarimetric studies are an important source of information about the physical properties of celestial bodies. In 2018, we put into operation the new two-channel polarimeters in the Crimean Astrophysical Observatory and the Peak Terskol Observatory. With the help of these instruments, in the period from 2018 to 2020, we carried out measurements of the polarization characteristics of 19 comets. Based on these data, we obtained the phase dependences of linear polarization degree of comets in the R, V, and I broadband filters. We approximate the polarization curves by a trigonometric expression. It was found that in the region of negative polarization, the phase curves of polarization in all three filters practically coincide. We also found that there is a noticeable difference in the degree of linear polarization between short-period and long-period comets. The polarization minimum of short-period comets is almost twice as high as that of long-period comets. It is shown, that for the interpretation of observational data, multispectral observations in at least three different spectral ranges are required. Moreover, for a reliable interpretation of observations, model particles with internal porosity should be used.

Linking stellar populations to H II regions across nearby galaxies

Context. Stellar feedback is one of the fundamental factors regulating the evolution of galaxies. However, we still do not have access to strong observational constraints on the relative importance of the different feedback mechanisms (e.g. radiation, ionised gas pressure, stellar winds) in driving H II region evolution and molecular cloud disruption. To quantify and compare the different feedback mechanisms, the size of an H II region is crucial, whereas samples of well-resolved H II regions are scarce. Aims. We constrain the relative importance of the various feedback mechanisms from young massive star populations by resolving H II regions across the disk of the nearby star-forming galaxy NGC 1672. Methods. We combined measurements of ionised gas nebular lines obtained by PHANGS-MUSE, with high-resolution (PSF FWHM ∼ 0.1″; ∼10 pc) imaging from Hubble Space Telescope (HST) in both the narrow-band Hα and broad-band (NUV, U, B, V, I) filters. We identified a sample of 40 isolated, compact H II regions in the HST Hα image. We measured the sizes of these H II regions, which were previously unresolved in seeing-limited ground-based observations. In addition, we identified the ionisation source(s) for each H II region from catalogues produced as part of the PHANGS-HST survey. In doing so, we were able to link young stellar populations with the properties of their surrounding H II regions. Results. The HST observations allowed us to resolve all 40 regions, with radii between 5 and 40 pc. The H II regions investigated here are mildly dominated by thermal or wind pressure, yet their elevation above the radiation pressure is within the expected uncertainty range. We see that radiation pressure provides a substantially higher contribution to the total pressure than previously found in the literature over similar size scales. In general, we find higher pressures within more compact H II regions, which is driven by the inherent size scaling relations of each pressure term, albeit with significant scatter introduced by the variation in the stellar population properties (e.g. luminosity, mass, age, metallicity). Conclusions. For nearby galaxies, the combination of MUSE/VLT observations with stellar population and resolved Hα observations from HST provides a promising approach that could yield the statistics required to map out how the importance of different stellar feedback mechanisms evolve over the lifetime of a H II region.

Improving axial resolution of medical ultrasound images by using noise-robust broadband filter based on singular value decomposition

Improving spatial resolution is a crucial issue in medical ultrasound. One of the improving methods is the post-processing of the received ultrasound RF signal. In the present paper, we proposed a design method for a noise-robust broadband filter based on the singular value decomposition of the received RF signal. To design a noise-robust filter, we proposed a logical method to determine the optimal truncated order of singular values, which was validated by applying the filter to noise-contaminated signals. Furthermore, the proposed filter applied to the wire phantom resulted in a better axial resolution than that obtained without the filter and with our previously designed Wiener filter.

The Age of Discovery with the James Webb Space Telescope: Excavating the Spectral Signatures of the First Massive Black Holes

The James Webb Space Telescope (JWST) will open a new window into the most distant universe and unveil the early growth of supermassive black holes (BHs) in the first galaxies. In preparation for deep JWST imaging surveys, it is crucial to understand the color selection of high-redshift accreting seed BHs. We model the spectral energy distribution of super-Eddington accreting BHs with millions of solar masses in metal-poor galaxies at z ≳ 8, applying postprocess line transfer calculations to radiation hydrodynamical simulation results. Exposures of 10 ks with the NIRCam and MIRI broadband filters are sufficient to detect the radiation flux from the seed BHs with bolometric luminosities of L bol ≃ 1045 erg s−1. While the continuum colors are similar to those of typical low-z quasars, strong Hα line emission with a rest-frame equivalent width EWrest ≃ 1300 Å is so prominent that the line flux affects the broadband colors significantly. The unique colors, for instance, F356W − F560W ≳ 1 at 7 < z < 8 and F444W − F770W ≳ 1 at 9 < z < 12, provide robust criteria for photometric selection of rapidly growing seed BHs. Moreover, NIRSpec observations of low-ionization emission lines can test whether the BH is fed via a dense accretion disk at super-Eddington rates.

Simulation of dynamically tunable broadband and polarization-insensitive electromagnetically induced transparency in Dirac semimetal

The structure proposed in this paper is composed of an outer circular ring resonator (CRR) and four L-shaped resonators (LSRs) in the middle. The destructive interference between bright modes produces a broadband electromagnetically induced transparency (EIT) with a maximum transmission efficiency of 97.6% in both vertical polarization directions. The field distributions and the three-level Λ-type system clarify the physical mechanism of the coupling process between bright modes. The calculated transmission spectrum based on the two-particle model is consistent with the simulated transmission spectrum, which proves the correctness of the results. By introducing hybridization bandgap (HBG) to the structure, the bandwidth of EIT-like effect expands. This structure has a fourfold (C4) rotational symmetry; thus, it is insensitive to the polarization angle. In addition, the transparency window undergoes a redshift as the Fermi energy of Dirac semimetal decreases. Meanwhile, the group delay is also controlled. Due to the wide bandwidth, a large delay bandwidth product (DBP) is obtained. Our work provides a new method for the production of slow-light devices and broadband filters.

Follow the water: finding water, snow, and clouds on terrestrial exoplanets with photometry and machine learning

ABSTRACT All life on Earth needs water. NASA’s quest to follow the water links water to the search for life in the cosmos. Telescopes like the James Webb Space Telescope and mission concepts like HabEx, LUVOIR, and Origins are designed to characterize rocky exoplanets spectroscopically. However, spectroscopy remains time-intensive, and therefore, initial characterization is critical to prioritization of targets. Here, we study machine learning as a tool to assess water’s existence through broad-band filter reflected photometric flux on Earth-like exoplanets in three forms: seawater, water-clouds, and snow; based on 53 130 spectra of cold, Earth-like planets with six major surfaces. XGBoost, a well-known machine-learning algorithm, achieves over 90 per cent balanced accuracy in detecting the existence of snow or clouds for S/N ≳ 20, and 70 per cent for liquid seawater for S/N ≳ 30. Finally, we perform mock Bayesian analysis with Markov chain Monte Carlo with five filters identified to derive exact surface compositions to test for retrieval feasibility. The results show that the use of machine learning to identify water on the surface of exoplanets from broad-band filter photometry provides a promising initial characterization tool of water in different forms. Planned small and large telescope missions could use this to aid their prioritization of targets for time-intense follow-up observations.

Multiple Resonances Induced Terahertz Broadband Filtering in a Bilayer Metamaterial

A bilayer metamaterial to realize the broadband transmission in a terahertz (THz) filter was proposed, whose periodic unit structure consists of two rectangular apertures. The broadband consisting of three transmission peaks has a 3dB transmission range of 0.75 THz, which is 1.6 times that of the monolayer structure. Different from the traditional narrow band excitation mode, two additional transmission peaks are produced by the bilayer metamaterials. Sweeping frequency analysis has illustrated that the spacing between two layers of metamaterials has an influence on these additional transmission peaks. The bandwidth ranges can be regulated by adjusting the spacing at a proportional height. In particular, the experimental results show that the proposed filter has an excellent frequency selective performance with a bandwidth of 0.7 THz from 0.79 THz to 1.49 THz. This design of broadband filtering by introducing the bilayer metamaterial supplies a new approach with potential application in the THz broadband filter.

Minimization of power losses in passive power filters

THE PURPOSE. Broadband passive filters (BBF) are an effective measure to mitigate harmonic resonance in power systems with nonlinear harmonic producing loads. The disadvantage of simple second-order broadband filters are pure selectivity and excessive fundamental frequency losses. This is especially evident in devices designed for low-order harmonics mitigation. This paper presents new broadband filter configurations with superior performances and low fundamental frequency losses.METHODS. A general method of broadband passive filter design is considered. The filter has the form of single-loaded ladder LC-two-port. Conditions of minimal fundamental frequency loss of the filer are determined.RESULTS. This paper presents new broadband filter configurations with superior damping performances and low fundamental frequency losses. Different broadband filter configurations are compared. The results show that 3-5 order broadband ladder filters have better filtering performance and lower power loss than traditional C-type filters.CONCLUSION. The proposed broadband filters can be used for industrial power systems with powerful nonlinear loads. This will normalize the power quality and at the same time improve the energy efficiency of compensating devices.

Broadband stop filters for THz waves using H-shaped metamaterials with dual electronic-plasmonic functionality

Terahertz (THz) waves have attracted extensive attention recently owing to their spectral specificity and transmission properties. For developing THz technologies, filters are significant devices because they can manipulate waves transmission. Metamaterials (MMs) possess unique optical characteristics that are not available in natural materials, have been developed for THz filters. However, reported MMs with separated units only excite plasmonic resonances, which limits their application. Here, broadband stop filters based on H-shaped MMs (H-MMs) for THz waves were proposed. The H-MM has two continuous metallic arms that can flow the electric current, allowing it to benefit electronic applications meanwhile keeping the plasmonic characteristics. A stopband with a central frequency of 0.65 THz and a −10 dB bandwidth of 458 GHz was experimentally demonstrated. Moreover, this filter can freely tune its bandwidth and central frequency by designing its geometry, which provides it with potential in wide THz applications such as THz communications.

High-resolution synthetic UV-submm images for Milky Way-mass simulated galaxies from the ARTEMIS project

ABSTRACT We present redshift-zero synthetic dust-aware observations for the 45 Milky Way-mass simulated galaxies of the ARTEMIS project, calculated with the skirt radiative transfer code. The post-processing procedure includes components for star-forming regions, stellar sources, and diffuse dust. We produce and publicly release realistic high-resolution images for 50 commonly used broad-band filters from ultraviolet to submillimetre wavelengths and for 18 different viewing angles. We compare the simulated ARTEMIS galaxies to observed galaxies in the DustPedia data base with similar stellar mass and star formation rate, and to synthetic observations of the simulated galaxies of the Auriga project produced in previous work using a similar post-processing technique. In all cases, global galaxy properties are derived using SED fitting. We find that, similar to Auriga, the post-processed ARTEMIS galaxies generally reproduce the observed scaling relations for global fluxes and physical properties, although dust extinction at FUV/UV wavelengths is underestimated and representative dust temperatures are lower than observed. At a resolved scale, we compare multiwavelength non-parametric morphological properties of selected disc galaxies across the data sets. We find that the ARTEMIS galaxies largely reproduce the observed morphological trends as a function of wavelength, although they appear to be more clumpy and less symmetrical than observed. We note that the ARTEMIS and Auriga galaxies occupy adjacent regions in the specific star formation versus stellar mass plane, so that the synthetic observation data sets supplement each other.

Broadband edge filter based on a helical long-period fiber grating and its application to a power-interrogated torsion sensor

A broadband edge filter with linear dynamic ranges of 40 n m in wavelength and 93 % in transmission loss has been demonstrated both theoretically and experimentally, which is achieved by using a helical long-period fiber grating (HLPG) operating near the dispersion turning point (DTP) of the L P 1 , 10 mode. To take full advantage of the wide dynamic ranges, the fabricated edge filter has been successfully used as a power-interrogated torsion sensor, and the torsion responsivity presented is about 0.501 nm/(rad/m), which is higher than most conventional HLPG-based torsion sensors. The results indicate that the proposed edge filter may find applications in any other kinds of power-interrogated sensors as well.

Polarization of Rotationally Oblate Self-luminous Exoplanets with Anisotropic Atmospheres

Abstract The young self-luminous giant exoplanets are expected to be oblate in shape, owing to the high rotational speeds observed for some objects. Similar to the case of brown dwarfs, the thermal emission from these planets should be polarized by scatterings of molecules and condensate cloud particles, and the rotation-induced asymmetry of the planet’s disk would yield to net nonzero detectable polarization. Considering an anisotropic atmosphere, we present here a three-dimensional approach to estimating the disk-averaged polarization that arises due to the oblateness of the planets. We solve the multiple-scattering vector radiative transfer equations at each location on the planet’s disk and calculate the local Stokes vectors, and then calculate the disk-integrated flux and linear polarization. For a cloud-free atmosphere, the polarization signal is observable only in the visible wavelength region. However, the presence of clouds in the planetary atmospheres leads to a detectable amount of polarization in the infrared wavelength region where the planetary thermal emission peaks. Considering the different broadband filters of the SPHERE-IRDIS instrument of the Very Large Telescope, we present generic models for the polarization at different wavelength bands as a function of their rotation period. We also present polarization models for the exoplanets β Pic b and ROXs 42B b, as two representative cases that can guide future observations. Our insights into the polarization of young giant planets presented here would be useful for the upcoming polarimetric observations of the directly imaged planets.

The intracluster light on Frontier Fields clusters Abell 370 and Abell S1063

ABSTRACT We analysed the contribution of the intracluster light (ICL) to the total luminosity of two massive galaxy clusters observed by the Hubble Space Telescope within the Frontier Fields program, Abell 370 (z ∼ 0.375) and Abell S1063 (z ∼ 0.348), in order to correlate it with the dynamical stage of these systems. We applied an algorithm based on the Chebyshev–Fourier functions called CICLE, specially developed to disentangle the ICL from the light of galaxies and measure the ICL fraction. We measured the ICL fraction in three broad-band optical filters, F435W, F606W, and F814W, without assuming any prior hypothesis about the ICL physical properties or morphology. The results obtained from the ICL fraction vary between $\sim 7\!-\!25{{\ \rm per\ cent}}$, and $\sim 3\!-\!22{{\ \rm per\ cent}}$ for both A370 and AS1063, respectively, which are consistent with theoretical predictions for the total amount of ICL obtained by ICL formation and evolution simulations. We found enhanced ICL fractions in the intermediate filter F606W for both clusters and we suggest that this is due to the presence of an excess of younger/lower metallicity stars in the ICL compared to the cluster galaxies. We conclude that both Abell 370 and Abell S1063 are merging systems since they exhibit a similar feature as merging CLASH and Frontier Fields clusters sub-sample previously analysed. We compare these results to the dynamical indicators obtained through different methods and we reinforce the use of ICL as a new and independent method to determine the dynamical state of clusters of galaxies.

Third data release of the Hyper Suprime-Cam Subaru Strategic Program

AbstractThis paper presents the third data release of the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP), a wide-field multi-band imaging survey with the Subaru 8.2 m telescope. HSC-SSP has three survey layers (Wide, Deep, and UltraDeep) with different area coverages and depths, designed to address a wide array of astrophysical questions. This third release from HSC-SSP includes data from 278 nights of observing time and covers about 670 deg2 in all five broad-band filters (grizy) at the full depth (∼26 mag at 5σ depending on filter) in the Wide layer. If we include partially observed areas, the release covers 1470 deg2. The Deep and UltraDeep layers have $\sim\! 80\%$ of the originally planned integration times, and are considered done, as we have slightly changed the observing strategy in order to compensate for various time losses. There are a number of updates in the image processing pipeline. Of particular importance is the change in the sky subtraction algorithm; we subtract the sky on small scales before the detection and measurement stages, which has significantly reduced the number of false detections. Thanks to this and other updates, the overall quality of the processed data has improved since the previous release. However, there are limitations in the data (for example, the pipeline is not optimized for crowded fields), and we encourage the user to check the quality assurance plots as well as a list of known issues before exploiting the data. The data release website is 〈https://hsc-release.mtk.nao.ac.jp〉.