Advanced Camera Research Articles

The properties of RR Lyrae variable stars in the isolated Local Group dwarf galaxy WLM

ABSTRACTWe present an analysis of 50 F475W (≈B filter) and F814W (≈I filter) archival images taken with the Hubble Space Telescope (HST)/Advanced Camera for Surveys of one field in the isolated Local Group dwarf galaxy Wolf–Lundmark–Melotte (WLM). From point spread function fitting photometry of these images, we construct a colour–magnitude diagram and identify and characterize 90 RR Lyrae variables (76 ab-type and 14 c-type) determining their mean magnitudes, colours, periods, and amplitudes in the HST passbands. We have also uncovered 79 Cepheid-type variables, but because of the short time window of our observations (1.85 d), we are not confident in their period determinations. The mean period of the ab-type RR Lyraes is found to be 〈Pab〉 = 0.609 ± 0.058 (ran) corresponding to a mean metallicity of 〈[Fe/H]〉 = −1.74 ± 0.02 (ran) on the Carretta et al. scale. We also present a re-analysis of the Hodge et al. colour–magnitude diagram of the WLM globular cluster and conclude that it is much more metal-poor than Hodge et al. quote. Based on a comparison of the WLM RR Lyraes with those in the other seven ‘isolated’ dwarf galaxies of the Local Group (i.e. Leo A, LGS 3, Cetus, IC 1613, Aquarius, Tucana, and Phoenix), we conclude that there was one unique epoch of early star formation common to all of these isolated dwarfs.

Simulation Model for Robotic Pick-Point Evaluation for 2-F Robotic Gripper

Robotic bin-picking performance has been gaining attention in recent years with the development of increasingly advanced camera and machine vision systems, collaborative and industrial robots, and sophisticated robotic grippers. In the random bin-picking process, the wide variety of objects in terms of shape, weight, and surface require complex solutions for the objects to be reliably picked. The challenging part of robotic bin-picking is to determine object pick-points correctly. This paper presents a simulation model based on ADAMS/MATLAB cosimulation for robotic pick-point evaluation for a 2-F robotic gripper. It consists of a mechanical model constructed in ADAMS/View, MATLAB/Simulink force controller, several support functions, and the graphical user interface developed in MATLAB/App Designer. Its functionality can serve three different applications, such as: (1) determining the optimal pick-points of the object due to object complexity, (2) selecting the most appropriate robotic gripper, and (3) improving the existing configuration of the robotic gripper (finger width, depth, shape, stroke width, etc.). Additionally, based on this analysis, new variants of robotic grippers can be proposed. The simulation model has been verified on a selected object on a sample 2-F parallel robotic gripper, showing promising results, where up to 75% of pick-points were correctly determined in the initial testing phase.

Application of smartphone-image processing and transfer learning for rice disease and nutrient deficiency detection

The earliest detection of plant disease is the primary concern of the farming community. The availability of advanced digital cameras and smartphones with improved image acquisition modes and deep learning methods like convolutional neural networks (CNN) can detect plant disease with high accuracy. This study used 2259 smartphone images of various rice (Oryza sativa) plant parts under various classes and 250 real-time validation images for classifying 12 rice diseases and nutrient deficiency symptoms. Different image segmentation techniques like foreground extraction were used to segment affected portions. Additionally, optimization of models and procedures to use them in smartphones with offline working capabilities have been described. Furthermore, a dynamic framework has been developed and demonstrated where the server trains on unseen image data to improve the classification performance and updates the model on falling below a certain threshold level. A comparison was made across different models used for image classification with many supporting metrics to select the best model for transfer learning. The top four performing models were DenseNet201, Xception, MobileNetV2, and ResNet50, with validation accuracies of 0.9803, 0.9778, 0.9756, and 0.9718, respectively. The ResNet50 model was found to best among all for cloud architectures, while MobileNetV2 appeared as the best model for the smartphone application. Finally, the android application, “Rice Disease Detector” compiled with the MobileNetV2 model was tested for multiple disease occurrences in a single capture. More research is warranted to test the application for smartphones with variable configurations.

Wind Turbine Crack Inspection Using a Quadrotor With Image Motion Blur Avoided

The camera-equipped quadrotor is a preferable choice for wind turbine blade (WTB) crack inspection applications with the benefits of high portability and low cost. Unfortunately, the high speed of the quadrotor might cause image motion blur which leads to a crack detection failure. Recent works cope with this by adopting the advanced camera systems or image deblurring techniques, which, however, usually require additional hardware or extra computational load. In this paper, the crack detection failure problem caused by image motion blur is handled by means of quadrotor motion control. First, the desired speed range that can avoid the detection failure caused by the image motion blur is experimentally obtained. Then, a speed regulation controller is developed to regulate the quadrotor flying speed within the obtained range. Experimental studies for crack inspection of a WTB using a camera-equipped quadrotor under wind condition are carried out to validate the effectiveness of the proposed strategy. Compared to the traditional approach without image motion blur avoidance, with the same inspection assignment and wind condition, the proposed method can obtain better quality images with 4.08 higher peak signal-to-noise ratio (PSNR) and 0.1 higher structural similarity index (SSIM) on average, where PSNR and SSIM are two typical image quality assessment metrics. As a result, the crack detection failure problem is avoided and a successful WTB crack inspection is achieved.

Person Re-Identification with RGB-D and RGB-IR Sensors: A Comprehensive Survey.

Learning about appearance embedding is of great importance for a variety of different computer-vision applications, which has prompted a surge in person re-identification (Re-ID) papers. The aim of these papers has been to identify an individual over a set of non-overlapping cameras. Despite recent advances in RGB-RGB Re-ID approaches with deep-learning architectures, the approach fails to consistently work well when there are low resolutions in dark conditions. The introduction of different sensors (i.e., RGB-D and infrared (IR)) enables the capture of appearances even in dark conditions. Recently, a lot of research has been dedicated to addressing the issue of finding appearance embedding in dark conditions using different advanced camera sensors. In this paper, we give a comprehensive overview of existing Re-ID approaches that utilize the additional information from different sensor-based methods to address the constraints faced by RGB camera-based person Re-ID systems. Although there are a number of survey papers that consider either the RGB-RGB or Visible-IR scenarios, there are none that consider both RGB-D and RGB-IR. In this paper, we present a detailed taxonomy of the existing approaches along with the existing RGB-D and RGB-IR person Re-ID datasets. Then, we summarize the performance of state-of-the-art methods on several representative RGB-D and RGB-IR datasets. Finally, future directions and current issues are considered for improving the different sensor-based person Re-ID systems.

Hubble Space Telescope and Hyper-Suprime-Cam Weak-lensing Study of the Equal-mass Dissociative Merger CIZA J0107.7+5408

A dissociative merger is formed by the interplay of ram pressure and gravitational forces, which can lead to a spatial displacement of the dark matter and baryonic components of the recently collided subclusters. CIZA J0107.7+5408 is a nearby (z = 0.105) dissociative merger that hosts two X-ray brightness peaks and a bimodal galaxy distribution. Analyzing MMT/Hectospec observations, we investigate the line-of-sight and spatial distribution of cluster galaxies. Utilizing deep, high-resolution Hubble Space Telescope Advanced Camera for Surveys imaging and large field-of-view Subaru Hyper-Suprime-Cam observations, we perform a weak-lensing analysis of CIZA J0107.7+5408. Our weak-lensing analysis detects a bimodal mass distribution that is spatially consistent with the cluster galaxies but significantly offset from the X-ray brightness peaks. Fitting two Navarro–Frenk–White halos to the lensing signal, we find an equal-mass merger with subcluster masses of M ⊙ and M ⊙. Moreover, the mass-to-light ratios of the subclusters, and , are found to be consistent with each other and within the range of mass-to-light ratios found for galaxy clusters.

Ceramic Bonding Interface under Shear–Compression Stress: Ultra-High-Speed Imaging Contribution

The aim of this study is to visualize and characterize by ultra-high-speed imaging (UHSI) the failure phenomena at the resin–ceramic bonding interface of lithium disilicate (LiSi2) samples bonded with gold-standard protocol (Monobond Plus [MB]) and the nontoxic one (Monobond Etch & Prime [MEP]) subjected to mechanical loading. Unprecedented frame rate, image resolution, and recording time were reached by using the most advanced UHSI camera. The finite element analysis (FEA) of the proposed mechanical test confirmed that the specific design of our samples enables a combined shear and compression stress state, prone to test the bonding interface while being close to physiological stresses. Ten LiSi2 samples were pretreated by gold standard (MB, n = 5) and self-etching primer (MEP, n = 5). Axial compression loading gradually increased until catastrophic failure was performed. As shown by the FEA, the angle between the bonding interface and load direction leads to shear–compression stresses at the resin–ceramic bonding interface. Failure was recorded by UHSI at 300,000 fps. All recorded images were analyzed to segregate events and isolate the origin of fracture. For the first time, thanks to the image recording setup, it was observed that debonding is the first event before breakage, highlighting that sample fracture occurs by interfacial rupture followed by slippage and cohesive failure of materials. Failure mode could be described as mixed. MEP and MB showed similar results and behavior.

Hubble Space Telescope Observations of Tadpole Galaxies Kiso3867, SBS0, SBS1, and UM461

Tadpole galaxies are metal-poor dwarfs with typically one dominant star-forming region, giving them a head–tail structure when inclined. A metallicity drop in the head suggests that gas accretion with even lower metallicity stimulated the star formation. Here we present multiband Hubble Space Telescope WFC3 and Advanced Camera for Surveys images of four nearby (<25 Mpc) tadpoles, SBS0, SBS1, Kiso3867, and UM461, selected for their clear metallicity drops shown in previous spectroscopic studies. The properties of the star complexes and compact clusters are measured. Each galaxy contains from three to 10 young stellar complexes with 103–105 M ⊙ of stars ∼3–10 Myr old. Between the complexes, the disk has a typical age of ∼3 Gyr. Numerous star clusters cover the galaxies, both inside and outside the complexes. The combined cluster mass function, made by normalizing the masses and counts before stacking, is a power law with a slope of −1.12 ± 0.14 on a log–log plot and the combined distribution function of cluster lifetime decays with age as t −0.65±0.24. A comparison between the summed theoretical Lyman continuum (LyC) emission from all the clusters, given their masses and ages, is comparable to or exceeds the LyC needed to excite the observed Hα in some galaxies, suggesting LyC absorption by dust or undetected gas in the halo, or perhaps galaxy escape.

Demographics of the M-star Multiple Population in the Orion Nebula Cluster

We present updated results constraining multiplicity demographics for the stellar population of the Orion Nebula Cluster (ONC, a high-mass, high-density star-forming region), across primary masses 0.08–0.7 M ⊙. Our study utilizes archival Hubble Space Telescope data obtained with the Advanced Camera for Surveys using multiple filters (GO-10246). Previous multiplicity surveys in low-mass, low-density associations like Taurus identify an excess of companions to low-mass stars roughly twice that of the Galactic field and find the mass ratio distribution consistent with the field. Previously, we found the companion frequency to low-mass stars in the ONC is consistent with the Galactic field over mass ratios = 0.6–1.0 and projected separations = 30–160 au, without placing constraints on the mass ratio distribution. In this study, we investigate the companion population of the ONC with a double point-spread function (PSF) fitting algorithm sensitive to separations larger than 10 au (0.″025) using empirical PSF models. We identified 44 companions (14 new), and with a Bayesian analysis we estimate the companion frequency to low-mass stars in the ONC = 0.13 and the index of the power-law fit to the mass ratio distribution = 2.08 over all mass ratios and projected separations of 10–200 au. We find the companion frequency in the ONC is consistent with the Galactic field population, likely from states of high transient stellar density, and a probability of 0.002 that it is consistent with that of Taurus. We also find the ONC mass ratio distribution is consistent with the field and Taurus, potentially indicative of its primordial nature, a direct outcome of the star formation process.

DESIGN AND CONTROL OF HYBRIDHELIUM ORNITHOPTER

Unmanned Aerial Vehicles (UAV) are devices that can be operated without human presence inside them. In the era of developing technologies, the need for humans to monitor their surroundings much more feasibly proposes an important need. In that way,this paper proposes to develop a hybrid helium blimp structure filled with helium gas. The structure can be operated at six degrees of freedom, which adds to its much-improved user experience and various flight methods. To record motion and see the environment around the blimp, an advanced camera is placed on the bottom of the structure, to record the motion of the surroundings. The external surface is elastic matter, which when it comes incontact with humans or other surroundings doesn’t pose a threat, due to its buoyancy property. The entire model can be transported fromone place to another, by just removing the external portionsof the blimp when traveling. The user on the ground can navigate and control the blimp, with the help of a user interface. The paper showcases the design, working, and real-life results of the structure.

Differences between the globular cluster systems of the Virgo and Fornax galaxy clusters

ABSTRACT It is well-known that Globular cluster systems are different among galaxies. Here, we test to which degree these differences remain on the scale of galaxy clusters by comparing the globular clusters (GCs) in optical surveys of the Virgo galaxy cluster (ACSVCS) and the ACS Fornax galaxy cluster (ACSFCS) in Kolmogorov–Smirnoff Tests. Both surveys were obtained with the Advanced Camera for Surveys (ACS) on board the Hubble Space Telescope, and contain thousands of GCs in dozens of galaxies each. Also, well over 100 point sources in the Chandra X-ray Observatory source catalogue were attributed to the GCs in both optical catalogues, and interpreted as low-mass X-ray binaries (LMXBs). Thus, the optical and X-ray data are as uniform as possible. Our main findings are as follows: (1) The spread in luminosities and half-light radii is larger in the ACSVCS than in the ACSFCS. (2) The ratio between the half-light radii for the F475W-passband and the F850LP-passband is on average smaller in the ACSVCS. (3) The distribution of the LMXBs with the luminosity of the GCs is different between both surveys. These findings are significant. The first finding could be a consequence of a wider spread in the distances of the GCs in the ACSVCS, but the others must have internal reasons in the GCs. Thus, the GC systems are also different on a galaxy cluster scale.

Photometric Redshift Estimates using Bayesian Neural Networks in the CSST Survey

Galaxy photometric redshift (photoz) is crucial in cosmological studies, such as weak gravitational lensing and galaxy angular clustering measurements. In this work, we try to extract photoz information and construct its probability distribution function (PDF) using the Bayesian neural networks from both galaxy flux and image data expected to be obtained by the China Space Station Telescope (CSST). The mock galaxy images are generated from the Hubble Space Telescope - Advanced Camera for Surveys (HST-ACS) and COSMOS catalogs, in which the CSST instrumental effects are carefully considered. In addition, the galaxy flux data are measured from galaxy images using aperture photometry. We construct a Bayesian multilayer perceptron (B-MLP) and Bayesian convolutional neural network (B-CNN) to predict photoz along with the PDFs from fluxes and images, respectively. We combine the B-MLP and B-CNN together, and construct a hybrid network and employ the transfer learning techniques to investigate the improvement of including both flux and image data. For galaxy samples with signal-to-noise ratio (SNR) > 10 in g or i band, we find the accuracy and outlier fraction of photoz can achieve σ NMAD = 0.022 and η = 2.35% for the B-MLP using flux data only, and σ NMAD = 0.022 and η = 1.32% for the B-CNN using image data only. The Bayesian hybrid network can achieve σ NMAD = 0.021 and η = 1.23%, and utilizing transfer learning technique can improve results to σ NMAD = 0.019 and η = 1.17%, which can provide the most confident predictions with the lowest average uncertainty.

Synthetic Color–Magnitude Diagrams for the Globular Cluster 47 Tucanae

Globular clusters contain the largest coeval populations of stars in the Milky Way, making them prime targets for stellar evolution studies. We present new theoretical isochrones for the brightest monometallic globular cluster 47 Tucanae, based on the spectroscopic measurements of the chemical composition in literature. Calculated colors are compared to existing photometric observations with Advanced Camera for Surveys on the Hubble Space Telescope. We find that the adopted abundances are consistent with the blue tail of the observed color distribution, implying a possible systematic offset between spectroscopic and photometric abundances of globular clusters. Additionally, we make color–magnitude predictions for future observations with the Near Infrared Camera on the James Webb Space Telescope in bands corresponding to the ongoing observational campaigns.

Detection of 125.5-day optical periodic modulation of the neutron star M51 ULX-8

ABSTRACT Studying Ultraluminous X-ray sources (ULXs) in the optical wavelengths provides important clues about the accretion mechanisms and the evolutionary processes of X-ray binary systems. In this study, three (C1, C2, and C3) possible optical counterparts were identified for well-known neutron star (NS) candidate M51 ULX-8 through advanced astrometry based on the Chandra and Hubble Space Telescope (HST) observations, as well as the GAIA optical source catalogue. Optical periodic modulation of 125.5 d with an amplitude of 0.14 mag was determined for C3, which has evidence to represent the optical nature of ULX-8 using one-year (2016–2017) 34 HST Advanced Camera for Surveys (ACS)/Wide Field Camera (WFC) observations. Moreover, surprisingly, the observed optical fluxes of C3 exhibit a bi-modal distribution. This could mean that there is a possible correlation between the optical and the X-ray flux variabilities of the ULX-8. The possible scenarios which are frequently mentioned in the literature proposed for the nature of optical emission and optical super-orbital period. The most probable scenario is that the optical emission could have originated from the accretion disc of the ULX-8.

A study of globular clusters in a lenticular galaxy in Hydra I from deep HST/ACS photometry

Aims. We take advantage of exquisitely deep optical imaging data from the Hubble Space Telescope’s Advanced Camera for Surveys (HST/ACS) in the F475W (gF475W) and F606W (VF606W) bands to study the properties of the globular cluster (GC) population in the intermediate-mass lenticular galaxy PGC 087327in the Hydra I galaxy cluster. Methods. We inspected the photometric (magnitudes and colour) and morphometric (compactness, elongation, etc.) properties of sources lying in an area of ∼19 × 19 kpc centred on PGC 087327 and compared them with four neighbouring fields over the same HST/ACS mosaic. This allowed us to identify a list of GC candidates and to inspect their properties using a background decontamination method. Results. Relative to four comparison fields, PGC 087327 shows a robust overdensity of GCs, NGC = 82 ± 9. At the estimated magnitude of the galaxy, this number implies a specific frequency of SN = 1.8 ± 0.7. In spite of the short wavelength interval available with the gF475W and VF606W passbands, the colour distribution shows a clear bimodality with a blue peak at ⟨gF475W − VF606W⟩ = 0.47 ± 0.05 mag and a red peak at ⟨gF475W − VF606W⟩ = 0.62 ± 0.03 mag. We also observe the typical steeper slope of the radial distribution of red GCs relative to blue ones. Thanks to the unique depth of the available data, we characterise the GC luminosity function (GCLF) well beyond the expected GCLF turnover. We find gTOMF475W = 26.54 ± 0.10 mag and VTOMF606W = 26.08 ± 0.09 mag, which after calibration yields a distance of DGCLF = 56.7 ± 4.3(statistical) ± 5.2(systematic) Mpc.

The Hubble Space Telescope Survey of M31 Satellite Galaxies. I. RR Lyrae–based Distances and Refined 3D Geometric Structure

We measure homogeneous distances to M31 and 38 associated stellar systems (−16.8 ≤ M V ≤ −6.0), using time-series observations of RR Lyrae stars taken as part of the Hubble Space Telescope Treasury Survey of M31 Satellites. From >700 orbits of new/archival Advanced Camera for Surveys imaging, we identify >4700 RR Lyrae stars and determine their periods and mean magnitudes to a typical precision of 0.01 day and 0.04 mag. Based on period–Wesenheit–metallicity relationships consistent with the Gaia eDR3 distance scale, we uniformly measure heliocentric and M31-centric distances to a typical precision of ∼20 kpc (3%) and ∼10 kpc (8%), respectively. We revise the 3D structure of the M31 galactic ecosystem and: (i) confirm a highly anisotropic spatial distribution such that ∼80% of M31's satellites reside on the near side of M31; this feature is not easily explained by observational effects; (ii) affirm the thin (rms 7–23 kpc) planar “arc” of satellites that comprises roughly half (15) of the galaxies within 300 kpc from M31; (iii) reassess the physical proximity of notable associations such as the NGC 147/185 pair and M33/AND xxii; and (iv) illustrate challenges in tip-of-the-red-giant branch distances for galaxies with M V > − 9.5, which can be biased by up to 35%. We emphasize the importance of RR Lyrae for accurate distances to faint galaxies that should be discovered by upcoming facilities (e.g., Rubin Observatory). We provide updated luminosities and sizes for our sample. Our distances will serve as the basis for future investigation of the star formation and orbital histories of the entire known M31 satellite system.

A detailed star formation history for the extremely diffuse Andromeda XIX dwarf galaxy

ABSTRACT We present deep imaging of the ultradiffuse Andromeda XIX dwarf galaxy from the Advance Camera for Surveys on the Hubble Space Telescope which resolves its stellar populations to below the oldest main-sequence turn-off. We derive a full star formation history for the galaxy using match, and find no evidence of star formation in the past 8 Gyr. We calculate a quenching time of τ90 = 9.7 ± 0.2 Gyr, suggesting And XIX ceased forming stars very early on. This early quenching, combined with its extremely large half-light radius, low-density dark matter halo and lower than expected metallicity make it a unique galaxy within the Local Group and raises questions about how it formed. The early quenching time allows us to rule out feedback from bursty star formation as a means to explain its diffuse stellar population and low-density dark matter halo. We find that the extended stellar population, low-density halo, and star formation could be explained by either tidal interactions (such as tidal shocking) or by late dry mergers, with the latter also explaining its low metallicity. Proper motions and detailed abundances would allow us to distinguish between these two scenarios.

Design of an Efficient Face Recognition system using Deep Learning Technique

Greater reliance on smart and portable electronic devices demands engineers to provide solutions with better performance and minimized demerits. Face Recognition involves the method of associating and confirming the faces. It is fit for distinguishing, following, recognizing, or checking human appearances from a picture or video caught utilizing an advanced camera. Feature extraction is the most significant stage for the achievement of the face recognition framework. The different ways of implementing this project depends on the programming language or algorithms used such as MATLAB, OpenCV, visual basics C#, Viola-Jones algorithm and many more while the core functioning remains the same. In this work, we have implemented face recognition in 3 phases, Phase1 consists of detecting faces and collecting images IDs, Phase 2 involves training the Recognizer and Separating interesting elements and the final phase includes grouping them and putting away in XML records.

The globular clusters and star formation history of the isolated, quiescent ultra-diffuse galaxy DGSAT I

ABSTRACT We investigate the isolated, quiescent ultra-diffuse galaxy (UDG) DGSAT I and its globular cluster (GC) system using two orbits of Hubble Space Telescope Advanced Camera for Surveys imaging in the F606W and F814W filters. This is the first study of GCs around a UDG in a low-density environment. DGSAT I was previously found to host an irregular blue low surface brightness clump, which we confirm as very likely belonging to the galaxy rather than being a chance projection, and represents a recent episode of star formation (∼500 Myr) that challenges some UDG formation scenarios. We select GC candidates based on colours and magnitudes, and construct a self-consistent model of the GC radial surface density profile along with the background. We find a half-number radius of RGC = 2.7 ± 0.1 kpc (more compact than the diffuse starlight) and a total of 12 ± 2 GCs. The total mass fraction in GCs is relatively high, supporting an overmassive dark matter halo as also implied by the high velocity dispersion previously measured. The GCs extend to higher luminosities than expected, and have colours that are unusually similar to their host galaxy colour, with a very narrow spread, all of which suggest an early, intense burst of cluster formation. The nature and origin of this galaxy remain puzzling, but the most likely scenario is a ‘failed galaxy’ that formed relatively few stars for its halo mass, and could be related to cluster UDGs whose size and quiescence pre-date their infall.

Calibration of UAV flight parameters for pavement pothole detection using orthogonal arrays

Visual inspection for road damages demands significant human effort. Automating these inspections would reduce costs and errors. Using photogrammetry to generate 3D models of roads has become popular thanks to advances in cameras and image processing techniques. Using UAVs, these models depend on images' capturing parameters such as height, overlap, and camera angle over the studied infrastructure. Traditionally, these flight parameters are defined on a trial-and-error basis without any systematic procedure. To fill this gap, the application of Taguchi's orthogonal arrays to calibrate the main flight parameters is proposed. To evaluate this methodology, the area and volume of pavement potholes were reconstructed from 3D models generated with UAV photographs. This article contributes with a methodology for developing 3D models and replicable for other types of infrastructure. Moreover, the results obtained allow defining a flight and image capture strategy adequate to the quality requirements of the modelling, optimising time and resources.