Sazuna/UAT_keywords huggingface dataset:
Interpretation of Radio Wave Scintillation Observed through LOFAR Radio Telescopes. Radio waves propagating through a medium containing irregularities in the spatial distribution of the electron density develop fluctuations in their intensities and phases. In the case of radio waves emitted from astronomical objects, they propagate through electron density irregularities in the interstellar medium, the interplanetary medium, and Earth's ionosphere. The LOFAR radio telescope, with stations across Europe, can measure intensity across the VHF radio band and thus intensity scintillation on the signals received from compact astronomical objects. Modeling intensity scintillation allows the estimate of various parameters of the propagation medium, for example, its drift velocity and its turbulent power spectrum. However, these estimates are based on the assumptions of ergodicity of the observed intensity fluctuations and, typically, of weak scattering. A case study of single-station LOFAR observations of the strong astronomical source Cassiopeia A in the VHF range is utilized to illustrate deviations from ergodicity, as well as the presence of both weak and strong scattering. Here it is demonstrated how these aspects can lead to misleading estimates of the propagation medium properties, for example, in the solar wind. This analysis provides a method to model errors in these estimates, which can be used in the characterization of both the interplanetary medium and Earth's ionosphere. Although the discussion is limited to the case of the interplanetary medium and Earth's ionosphere, its ideas are also applicable to the case of the interstellar medium.

Keywords: Interplanetary scintillation, Ionospheric scintillation, Radio telescopes
Updated Photon Scattering Coefficients (g_values) for Mercury's Exospheric Species. In an optically thin exosphere such as those of Mercury and the Moon, the optically stimulated emissions are directly proportional to the stimulating solar flux. An important quantity in relating measured emission to column abundance in remote-sensing observations is the g_value. The g_value is proportional to the f-value of the emission line and to the solar flux at the emission frequency. The solar flux varies inversely with the heliocentric distance from the Sun, but also with the heliocentric relative velocity of the emitting atom. The heliocentric relative velocity of the planet Mercury varies by ±10 km s-1, however, the atoms may additionally have high velocities relative to the planet owing to high-energy processes or through acceleration caused by radiation pressure. In this paper we extend g_values to heliocentric relative velocities ±50 km s-1. In addition to 12 species for which g_values have been published previously, we have computed g_values for two additional species, Mn and Al, that were discovered in Mercury's exosphere in the course of the MESSENGER mission. We have not included updated g_values for C or OH, as these were not observed by MESSENGER. In this work, we employ the TSIS-1 hybrid reference solar spectrum for most calculations, with the SOLSTICE data being used in the EUV/far-UV. We note that the method employed here could be extended for application at extrasolar planets and comets, with the solar spectrum substituted by an appropriate stellar spectrum.

Keywords: Mercury (planet), Astronomy data modeling, Ultraviolet spectroscopy, Exosphere
ALMA Lensing Cluster Survey: Hubble Space Telescope and Spitzer Photometry of 33 Lensed Fields Built with CHArGE. We present a set of multiwavelength mosaics and photometric catalogs in the Atacama Large Millimeter/submillimeter Array (ALMA) lensing cluster survey fields. The catalogs were built by the reprocessing of archival data from the Complete Hubble Archive for Galaxy Evolution compilation, taken by the Hubble Space Telescope (HST) in the Reionization Lensing Cluster Survey, Cluster Lensing And Supernova survey with Hubble, and Hubble Frontier Fields. Additionally, we have reconstructed the Spitzer Infrared Array Camera 3.6 and 4.5 μm mosaics, by utilizing all the available archival IPAC Infrared Science Archive/Spitzer Heritage Archive exposures. To alleviate the effect of blending in such a crowded region, we have modeled the Spitzer photometry by convolving the HST detection image with the Spitzer point-spread function using the novel GOLFIR software. The final catalogs contain 218,000 sources, covering a combined area of 690 arcmin2, a factor of ~2 improvement over the currently existing photometry. A large number of detected sources is a result of reprocessing of all available and sometimes deeper exposures, in conjunction with a combined optical-near-IR detection strategy. These data will serve as an important tool in aiding the search of the submillimeter galaxies in future ALMA surveys, as well as follow-ups of the HST dark and high-z sources with JWST. Coupled with the available HST photometry, the addition of the 3.6 and 4.5 μm bands will allow us to place a better constraint on the photometric redshifts and stellar masses of these objects, thus giving us an opportunity to identify high-redshift candidates for spectroscopic follow-ups and to answer the important questions regarding the Epoch of Reionization and formation of the first galaxies. The mosaics, photometric catalogs, and the best-fit physical properties are publicly available at https://github.com/dawn-cph/alcs-clusters.

Keywords: Galaxy evolution, Interstellar medium, Photometry, Submillimeter astronomy, High-redshift galaxies, Catalogs
Evidence of Photosphere Emission Origin for Gamma-Ray Burst Prompt Emission. The physical origins of gamma-ray burst (GRB) prompt emission (photosphere or synchrotron) are still subject to debate, after more than five decades. Here, we find that many of the observed characteristics of 15 long GRBs, which have the highest prompt emission efficiency ϵ  γ  (ϵ  γ  ≳ 80%), strongly support photosphere (thermal) emission origin, in the following ways: (1) the relation between E p and E iso is almost ${E}_{{\rm{p}}}\propto {({E}_{\mathrm{iso}})}^{1/4}$ and the dispersion is quite small; (2) the simple power-law shape of the X-ray afterglow light curves and the presence of significant reverse shock signals in the optical afterglow light curves; (3) the best fits using the cutoff power-law model for time-integrated spectra; and (4) the consistent efficiency from observations (with E iso/E  k ) and the predictions from the photosphere emission model (with η/Γ). We then further investigate the characteristics of the long GRBs for two distinguished samples (ϵ  γ  ≳ 50% and ϵ  γ  ≲ 50%). It is found that the different distributions for E p and E iso, and the similar observed efficiency (from the X-ray afterglow) and theoretically predicted efficiency (from the prompt emission or the optical afterglow), follow the predictions of the photosphere emission model well. Also, based on the same efficiency, we derive an excellent correlation of ${\rm{\Gamma }}\propto {E}_{\mathrm{iso}}^{1/8}{E}_{{\rm{p}}}^{1/2}/{\left({T}_{90}\right)}^{1/4}$ to estimate Γ. Finally, we show that different distributions for E p and E iso, and the consistent efficiency, exist for short GRBs. We also give a natural explanation of the extended emission (ϵ  γ  ≲ 50%) and the main pulse (ϵ  γ  ≳ 50%).

Keywords: Gamma-ray bursts
CO(J = 1-0) Mapping Survey of 64 Galaxies in the Fornax Cluster with the ALMA Morita Array. We conduct a 12C16O(J = 1-0) (hereafter CO) mapping survey of 64 galaxies in the Fornax cluster using the Atacama Large Millimeter/submillimeter Array Morita array in cycle 5. CO emission is detected from 23 out of the 64 galaxies. Our sample includes dwarf, spiral, and elliptical galaxies with stellar masses of M star ~ 106.3-11.6 M ☉. The achieved beam size and sensitivity are 15″ × 8″ and ~12 mJy beam-1 at the velocity resolution of ~10 km s-1, respectively. We study the cold gas (molecular and atomic gas) properties of 38 subsamples with M star &gt; 109 M ☉ combined with literature H I data. We find that (1) the low star formation (SF) activity in the Fornax galaxies is caused by the decrease in the cold gas mass fraction with respect to stellar mass (hereafter, gas fraction) rather than the decrease of the SF efficiency from the cold gas; (2) the atomic gas fraction is more heavily reduced than the molecular gas fraction of such galaxies with low SF activity. A comparison between the cold gas properties of the Fornax galaxies and their environmental properties suggests that the atomic gas is stripped tidally and by the ram pressure, which leads to the molecular gas depletion with an aid of the strangulation and consequently SF quenching. Preprocesses in the group environment would also play a role in reducing cold gas reservoirs in some Fornax galaxies.

Keywords: Galaxy clusters, Molecular gas, Galaxy environments
In the Trenches of the Solar-Stellar Connection. VI. Total EclipSS. The Ecliptic poles Stellar Survey (EclipSS; 2018-2019) collected Hubble Space Telescope/Cosmic Origins Spectrograph (COS) 1150-1420 Å spectra of 49 FGK dwarfs at high ecliptic latitudes. These regions are favored by the scanning programs of the Transiting Exoplanet Survey Satellite (TESS; high-precision optical light curves) and Extended Roentgen Survey with an Imaging Telescope Array (eROSITA; repeated X-ray visits over half a decade), which can provide vital ancillary support in the exploration of high-energy "stellar activity." The present study is a follow-on, focused on new Chandra/High Resolution Camera 0.1-2.4 keV X-ray pointings, COS 1340-1720 Å spectra, and TESS photometry of the 10 most active EclipSS members, but also including archival X-ray and far-ultraviolet (FUV) observations of 13 representative solar neighborhood FGK dwarfs, together with high-energy irradiances of the Sun, for context. The EclipSS dK+dM binary HD 41004 proved exceptional. The unexpectedly short TESS period (1.3 days) appears to be associated with the red dwarf secondary, possibly about to engulf a close-orbiting brown-dwarf companion. The current study describes the emission-line profiles of a high-resolution subset of the full sample, finding the non-Gaussian line shapes (sharper peaks, broader wings) and redshifts of T ~ 105 K features to be remarkably independent of activity; quantifies X-ray and FUV "variability bias" based on several multiple-epoch campaigns; builds enhanced flux-flux diagrams (e.g., X-rays versus C IV); and constructs an "XUV" proxy flux, representing the total coronal radiative loss, to test models of the convective turnover time, τ c. The associated Rossby number, Ro, is closely aligned to terrestrial and cosmic magnetic dynamo theories, and offers the prospect of a one-parameter description of stellar high-energy activity (relevant, for example, to host-star ionizing fluxes impacting exoplanets).

Keywords: Ultraviolet sources, Stellar activity, Stellar rotation, Stellar spectral lines, X-ray stars
A Catalog of Quasar Properties from Sloan Digital Sky Survey Data Release 16. We present a catalog of continuum and emission-line properties for 750,414 broad-line quasars included in the Sloan Digital Sky Survey Data Release 16 quasar catalog (DR16Q), measured from optical spectroscopy. These quasars cover broad ranges in redshift (0.1 ≲ z ≲ 6) and luminosity (44 ≲ log(L bol/erg s-1) ≲ 48), and probe lower luminosities than an earlier compilation of SDSS DR7 quasars. Derived physical quantities such as single-epoch virial black hole masses and bolometric luminosities are also included in this catalog. We present improved systemic redshifts and realistic redshift uncertainties for DR16Q quasars using the measured line peaks and correcting for velocity shifts of various lines with respect to the systemic velocity. About 1%, 1.4%, and 11% of the original DR16Q redshifts deviate from the systemic redshifts by ∣ΔV∣ &gt; 1500 km s-1, ∣ΔV∣ ∈ [1000, 1500] km s-1, and ∣ΔV∣ ∈ [500, 1000] km s-1, respectively; about 1900 DR16Q redshifts were catastrophically wrong (∣ΔV∣ &gt; 10,000 km s-1). We demonstrate the utility of this data product in quantifying the spectral diversity and correlations among physical properties of quasars with large statistical samples.

Keywords: Surveys, Quasars
A Generalized Phase Diversity Technique Using Multiple Defocused Images. Phase diversity techniques commonly employ a pair of focused-defocused images to retrieve the incident wave front and to restore the observed scene. However, the combination of more images, each one affected by a different amount of defocus, has been barely explored in solar astronomy. In this work we reformulate the "classic" two-images phase diversity approach to accommodate an arbitrary number of phase differences and we investigate its performance in synthetic magnetohydrodynamical simulations of the solar scene corrupted by noise and degraded by a certain set of aberrations. We employ different combinations of images defocused from ±0.5 λ up to ±2 λ (peak to peak) and compare both the retrieved wave front with the incident one and the restored images with the unaberrated noiseless scene. We investigate the effect of using a series of images defocused both symmetrically and asymmetrically with respect to the focused one. In these two cases the performance of the method is improved with the use of more than two images, although it benefits more from the use of symmetric defocuses. We find also that there is a qualitative best choice of the number of phase diversity images in terms of the goodness of the wave front retrieval and of the restored object. The presented method has a potential use either in instruments equipped with a refocusing mechanism or during the laboratory calibrations of the instrument provided that an optical target can be defocused manually by different amounts.

Keywords: Astronomical techniques, Astronomical instrumentation, Solar instruments
Sensitivity of the Roman Coronagraph Instrument to Exozodiacal Dust. Exozodiacal dust, warm debris from comets and asteroids in and near the habitable zone of stellar systems, reveals the physical processes that shape planetary systems. Scattered light from this dust is also a source of background flux which must be overcome by future missions to image Earthlike planets. This study quantifies the sensitivity of the Nancy Grace Roman Space Telescope Coronagraph to light scattered by exozodi, the zodiacal dust around other stars. Using a sample of 149 nearby stars, previously selected for optimum detection of habitable exoplanets by space observatories, we find the maximum number of exozodiacal disks with observable inner habitable zone boundaries is six and the number of observable outer habitable boundaries is 74. One zodi was defined as the visible-light surface brightness of 22 m V arcsec-2 around a solar-mass star, approximating the scattered light brightness in visible light at the Earth-equivalent insolation. In the speckle limited case, where the signal-to-noise ratio is limited by speckle temporal stability rather than shot noise, the median 5σ sensitivity to habitable zone exozodi is 12 zodi per resolution element. This estimate is calculated at the inner-working angle of the coronagraph, for the current best estimate performance, neglecting margins on the uncertainty in instrument performance and including a post-processing speckle suppression factor. For an log-norm distribution of exozodi levels with a median exozodi of 3× the solar zodi, we find that the Roman Coronagraph would be able to make 5σ detections of exozodiacal disks in scattered light from 13 systems with a 95% confidence interval spanning 7-20 systems. This sensitivity allows Roman Coronagraph to complement ground-based measurements of exozodiacal thermal emission and constrain dust albedos. Optimized post-processing and detection of extended sources in multiple resolution elements is expected to further improve this unprecedented sensitivity to light scattered by exozodiacal dust.

Keywords: Space telescopes, Coronagraphic imaging, Debris disks, Exozodiacal dust
Event Detection and Reconstruction Using Neural Networks in TES Devices: a Case Study for Athena/X-IFU. Transition Edge Sensors detector devices, like the core of the X-IFU instrument that will be on-board the Athena X-ray Observatory, produce current pulses as a response to the incident X-ray photons. The reconstruction of these pulses has been traditionally performed by means of a triggering algorithm based on the derivative signal overcoming a threshold (detection) followed by an optimal filtering (to retrieve the energy of each event). However, when the arrival of the photons is very close in time, the triggering algorithm is incapable of detecting all the individual pulses which are thus piled-up. In order to improve the efficiency of the detection and energy-retrieval process, we study here an alternative approach based on Machine Learning techniques to process the pulses. For this purpose, we construct and train a series of Neural Networks (NNs) not only for the detection but also for the recovering of the arrival time and the energy of simulated X-ray pulses. The data set used to train the NNs consists of simulations performed with the SIXTE/XIFUSIM software package, the Athena/X-IFU official simulator. The performance of our NN classification clearly surpasses the detection performance of the classical triggering approach for the full range of photon energy combinations, showing excellent metrics and very competitive computing efficiency. However, the precision obtained for the recovery of the energy of the photons cannot currently compete with the standard optimal filtering algorithm, despite its much better computing efficiency.

Keywords: X-ray astronomy, X-ray detectors, Telescopes, Neural networks
Research on Autofocus Recognition of the LAMOST Fiber View Camera System Under Front and Back Illumination. In the closed-loop detection system of the LAMOST, the lens of the fiber view camera system must focus the end of the optical fiber to accurately acquire the fiber position. It is difficult to evaluate the fibers image with a very small proportion of the image with the traditional autofocus algorithm, whether it is recognition of the front illuminated by the fiber ceramic ferrules, or the light-emitting spot of the fibers in the black background, that is, the recognition of the back illumination of the fibers. In this paper, we propose an autofocus determination method for the LAMOST closed-loop control under front and back illumination conditions. Under the condition of front illumination, to greatly reduce the calculation time, the system first pre-recognizes the focusing target through the Faster R-CNN and then uses an optimized contrast algorithm to evaluate the image definition of the corrected focusing target ROI. Then, the algorithm is compared with Tenengrad gradient and Laplacian gradient calculations using the Sobel operator and Laplacian operator in OpenCV. The results show that this method takes only one-ninth of the time required by the other methods to obtain the same accuracy. Under the condition of back illumination, we use the average number and average brightness of spot pixels as the evaluation basis of image sharpness. This method can complete the evaluation of image sharpness in the process of spot recognition and provide initial data for the subsequent detection for closed-loop control. The focus accuracy of the camera is of great significance for thousand-fiber metrology, which will have an important influence on the accuracy of astronomical observations. These focusing methods not only play an important role in the closed-loop control of the LAMOST but also apply to the focusing of closed-loop detection systems of other multi-target optical fiber spectral astronomical telescopes.

Keywords: Astronomical techniques, Astronomical instrumentation
PicSat's Enduring Legacy. Probing the Flight of a Small Astronomical Satellite. Observation of planetary transits and other cutting-edge scientific missions can take advantage of affordable nanosatellites to probe interesting stellar targets. PicSat, a CubeSat dedicated to observing the Beta Pictoris star system, was designed to provide high-precision star pointing, a critical requirement for planetary transit detection. PicSat's Attitude Determination and Control System, responsible for delivering high-accuracy spacecraft pointing, requires dedicated development based on dynamic simulators. This paper presents a dynamic attitude and orbit propagation simulator for CubeSats in low Earth orbit, as well as for its de-tumbling mode. Validation has been performed through PicSat's in-flight data. High-precision dynamic models have been obtained for both attitude and orbit. Such models are well suited to the different mission phases, from spacecraft design to data exploitation. It is, therefore, a crucial tool to minimize the chance of failure of both the platform and the payload, especially in satellites such as PicSat, whose pointing depends on both. PicSat left an enduring legacy: its platform data allow us to obtain flight models that will be valuable for future missions.

Keywords: Artificial satellites, Astronomical instrumentation
A New Multichannel Parallel Real-time FFT Algorithm for a Solar Radio Observation System Based on FPGA. The real-time fast Fourier transform (FFT) is the essential algorithm for signal processing in a solar radio receiver. However, field-programmable gate array (FPGA) computation resources have become the limitation of real-time processing of signals with increasing time and spectral resolutions. It is necessary to design a real-time parallel FFT algorithm with reduced resource occupation in the development of future receiving systems. In this paper, we developed a multichannel parallel FFT algorithm named the multichannel parallel real-time fast Fourier transform (MPR-FFT), which can greatly reduce FPGA resource occupation while increasing the real-time processing speed. In this algorithm, the 4L simultaneous N-point FFTs are first converted into L simultaneous 4N-point FFTs. Fusion processing is then performed to obtain the 4 ∗ L ∗ N-point spectrum. This method has been used in developing a solar radio spectrometer, which works in the frequency range of 0.5-15 GHz in the Chashan Observatory. In this spectrometer, 16 channel MPR-FFT with 8k-point data is realized in a Xilinx UltraScale KU115 FPGA. The MPR-FFT algorithm reduced the computational resources to a large extent compared to the Cooley-Tukey-based parallel FFT method; for instance, the Look-Up-Table, Look-Up-Table RAM, Flip-Flop, and Digital Signal Process slices were reduced by 37%, 50%, 17%, and 2.48%, respectively. Although the MPR-FFT consumes 14 block RAM resources more than the Cooley-Tukey-based parallel FFT, the MPR-FFT algorithm presents an overall reduction in resource usage.

Keywords: Radio spectroscopy, Solar radio telescopes, Astronomy software, Astronomical techniques, Radio receivers, Solar instruments, Radio astronomy