Subtraction Of Light Research Articles

Combining neural networks with galaxy light subtraction for discovering strong lenses in the Hyper Suprime-Cam Subaru Strategic Program

Abstract Galaxy-scale strong gravitational lenses are valuable objects for a variety of astrophysical and cosmological applications. Strong lensing galaxies are rare, so efficient search methods, such as convolutional neural networks (CNNs), are often used on large imaging datasets. In this work, we apply a new technique to improve the performance of supervised neural networks by subtracting the central (lensing) galaxy light from both the training and test datasets. We use multiband imaging data from the Hyper Suprime-Cam Subaru Strategic Program as our training and test datasets. By subtracting the lensing galaxy light, we increase the contrast of the lensed source compared to the original imaging data. We also apply the light subtraction to non-lenses in order to compare them to the light-subtracted lenses. Residual features resulting from poor light subtraction can adversely affect the performance of networks trained on the subtracted images alone. We find that combining the light-subtracted images with the original $gri$-band images for training and classification can overcome this and improve the overall classification accuracy. We find the area under the receiver operating characteristic curve can be improved to 0.841 using the combination of the fiducial images and light-subtracted images, compared to 0.808 for the fiducial imaging dataset alone. This may be a promising technique for improving future lens searches using CNNs.

Mass Reconstruction of Galaxy-scale Strong Gravitational Lenses Using a Broken Power-law Model

With mock strong gravitational lensing images, we investigate the performance of the broken power-law (BPL) model proposed by Du et al. () on the mass reconstruction of galaxy-scale lenses. An end-to-end test is carried out, including the creation of mock strong lensing images, the subtraction of lens light, and the reconstruction of lensed images, where the lenses are selected from the galaxies in the Illustris-1 simulation. We notice that, regardless of the adopted mass models (the BPL model or its special cases), the Einstein radius can be robustly determined from imaging data alone, and the median bias is typically less than 1%. Away from the Einstein radius, the lens mass distribution tends to be harder to measure, especially at radii where there are no lensed images detected. We find that, with rigid priors, the BPL model can clearly outperform the single power-law models by achieving <5% median bias on the radial convergence profile within the Einstein radius. As for the source light reconstructions, they are found to be sensitive to both lens light contamination and lens mass models, where the BPL model with rigid priors still performs best when there is no lens light contamination. We show that, by correcting for the projection effect, the BPL model can estimate the aperture and luminosity weighted line-of-sight velocity dispersions to an accuracy of ∼6% scatter. These results highlight the great potential of the BPL model in strong lensing related studies.

A UNIONS view of the brightest central galaxies of candidate fossil groups

Context. The formation process of fossil groups (FGs) is still under debate, and, because of their relative rarity, large samples of such objects are still missing. Aims. The aim of the present paper is to increase the sample of known FGs, to analyse the properties of their brightest group galaxies (BGGs), and to compare them with a control sample of non-FG BGGs. Methods. We extracted a sample of 87 FG and 100 non-FG candidates from a large spectroscopic catalogue of haloes and galaxies. For all the objects with data available in UNIONS (initially the Canada France Imaging Survey, CFIS) in the u and r bands, and/or in an extra r-band processed to preserve all low-surface-brightness features (rLSB), we performed a 2D photometric fit of the BGG with GALFIT with one or two Sérsic components. We also analysed how the subtraction of the intracluster light (ICL) contribution modifies the BGG properties. From the SDSS spectra available for the BGGs of 65 FGs and 82 non-FGs, we extracted the properties of their stellar populations with Firefly. To complement our study, and in order to provide a detailed illustration of the possible origin of emission lines in the FG BGGs, involving the presence or absence of an AGN, we investigated the origin of the emission lines in a nearby FG that is dominated by the NGC 4104 galaxy. Results. Morphologically, a single Sérsic profile can fit most objects in the u band, while two Sérsics are needed in the r and rLSB bands, both for FGs and non-FGs. Non-FG BGGs cover a larger range of Sérsic index n. FG BGGs follow the Kormendy relation (mean surface brightness versus effective radius) previously derived for almost 1000 brightest cluster galaxies (BCGs), while the majority of non-FGs BGGs are located below this relation, with fainter mean surface brightnesses. This suggests that FG BGGs have evolved similarly to BCGs, and non-FG BGGs have evolved differently from both FG BGGs and BCGs. All the above properties can be strongly modified by the subtraction of the ICL contribution. Based on spectral fitting, the stellar populations of FG and non-FG BGGs do not differ significantly. Conclusions. FG and non-FG BGGs differ from one another in terms of their morphological properties and Kormendy relation, suggesting they have had different formation histories. However, it is not possible to trace differences in their stellar populations or in their large-scale distributions.

A detailed spectroscopic study of tidal disruption events

Spectroscopically, tidal disruption events (TDEs) are characterized by broad (∼104 km s−1) emission lines and show a large diversity as well as different line profiles. After carefully and consistently performing a series of data reduction tasks including host galaxy light subtraction, we present here the first detailed, spectroscopic population study of 16 optical and UV TDEs. We study a number of emission lines prominent among TDEs including Hydrogen, Helium, and Bowen lines and we quantify their evolution with time in terms of line luminosities, velocity widths, and velocity offsets. We report a time lag between the peaks of the optical light curves and the peak luminosity of Hα spanning between ∼7 and 45 days. If interpreted as light echoes, these lags correspond to distances of ∼2 − 12 × 1016 cm, which are one to two orders of magnitudes larger than the estimated blackbody radii (RBB) of the same TDEs and we discuss the possible origin of this surprisingly large discrepancy. We also report time lags for the peak luminosity of the He I 5876 Å line, which are smaller than the ones of Hα for H TDEs and similar or larger for N III Bowen TDEs. We report that N III Bowen TDEs have lower Hα velocity widths compared to the rest of the TDEs in our sample and we also find that a strong X-ray to optical ratio might imply weakening of the line widths. Furthermore, we study the evolution of line luminosities and ratios with respect to their radii (RBB) and temperatures (TBB). We find a linear relationship between Hα luminosity and the RBB (Lline ∝ RBB) and potentially an inverse power-law relation with TBB (Lline ∝ TBB−β), leading to weaker Hα emission for TBB ≥ 25 000 K. The He II/He I ratio becomes large at the same temperatures, possibly pointing to an ionization effect. The He II/Hα ratio becomes larger as the photospheric radius recedes, implying a stratified photosphere where Helium lies deeper than Hydrogen. We suggest that the large diversity of the spectroscopic features seen in TDEs along with their X-ray properties can potentially be attributed to viewing angle effects.

Proximal Imaging of Changes in Photochemical Reflectance Index in Leaves Based on Using Pulses of Green-Yellow Light

Plants are affected by numerous environmental factors that influence their physiological processes and productivity. Early revealing of their action based on measuring spectra of reflected light and calculating reflectance indices is an important stage in the protection of agricultural plants. Photochemical reflectance index (PRI) is a widely used parameter related to photosynthetic changes in plants under action of stressors. We developed a new system for proximal imaging of PRI based on using short pulses of measuring light detected simultaneously in green (530 nm) and yellow (570 nm) spectral bands. The system has several advances compared to those reported in literature. Active light illumination and subtraction of the ambient light allow for PRI measurements without periodic calibrations. Short duration of measuring pulses (18 ms) minimizes their influence on plants. Measurements in two spectral bands operated by separate cameras with aligned fields of visualization allow one to exclude mechanically switchable parts like filter wheels thus minimizing acquisition time and increasing durability of the setup. Absolute values of PRI and light-induced changes in PRI (ΔPRI) in pea leaves and changes of these parameters under action of light with different intensities, water shortage, and heating have been investigated using the developed setup. Changes in ΔPRI are shown to be more robust than the changes in the absolute value of PRI which is in a good agreement with our previous studies. Values of PRI and, especially, ΔPRI are strongly linearly related to the energy-dependent component of the non-photochemical quenching and can be potentially used for estimation of this component. Additionally, we demonstrate that the developed system can also measure fast changes in PRI (hundreds of milliseconds and seconds) under leaf illumination by the pulsed green-yellow measuring light. Thus, the developed system of proximal PRI imaging can be used for PRI measurements (including fast changes in PRI) and estimation of stressors-induced photosynthetic changes.

End benches scattered light modelling and subtraction in advanced Virgo

Advanced Virgo end benches were a significant source of scattered light noise during the third observing run that lasted from April 1 2019 until March 27 2020. We describe how that noise could be subtracted using auxiliary channels during the online strain data reconstruction. We model in detail the scattered light noise coupling and demonstrate that further noise subtraction can be achieved. We also show that the fitted model parameters can be used to optically characterized the interferometer and in particular provide a novel way of establishing an absolute calibration of the detector strain data.

Dynamic real-time subtraction of stray-light and background for multiphoton imaging.

We introduce a new approach to reduce uncorrelated background signals from fluorescence imaging data, using real-time subtraction of background light. This approach takes advantage of the short fluorescence lifetime of most popular fluorescent activity reporters, and the low duty-cycle of ultrafast lasers. By synchronizing excitation and recording, laser-induced multiphoton fluorescence can be discriminated from background light levels with each laser pulse. We demonstrate the ability of our method to – in real-time – remove image artifacts that in a conventional imaging setup lead to clipping of the signal. In other words, our method enables imaging under conditions that in a conventional setup would yield corrupted data from which no accurate information can be extracted. This is advantageous in experimental setups requiring additional light sources for applications such as optogenetic stimulation.

Machine learning for determination of the native background EPR signal amplitude in the teeth enamel

The measurement of teeth in vivo (i.e., in the mouth, without extraction) with EPR spectroscopy in the L-band would allow to screen large groups of population in an event of an acute radiation exposure and in routine epidemiological studies. The radiation dose is proportional to intensity of the radiation-induced signal amplitude determined after subtraction of both native and solar light induced signal amplitudes from the total signal amplitude measured in L-band. Therefore, to improve the dose assessments of in vivo tooth dosimetry a better accuracy of native background signal is necessary. In this work, we present a search for the optimal machine learning approach for predicting of intensity of the native signal amplitude.The study used the dataset from two institutes composed of 1800 EPR spectra which were recorded in the X-band at a large-scale examination of the population of the Central Russia and North Kazakhstan. To determine the relevance of 12 various features a preliminary statistical significance analysis was used. Predictive models for native signal amplitude determination were developed and trained using standard Python frameworks for machine learning and data processing. The employed algorithms included 8 most popular machine learning regressors. To tune the performance of each algorithm a common evaluation technique, namely cross-validation, was used. Finally, mean squared error and coefficient of determination were calculated for performance analysis of the employed models.Comparison among the performance of all established prediction models revealed that Random Forest and Gradient Boosting had most superior performance. Overall, the application of machine learning methods was shown to provide a minor (5–11% in terms of R2) but non negligible improvement to the accuracy of native signal amplitude prediction. Using the technique of adding synthetic noise variables, the most significant factor regarding the prediction was position of tooth in the quadrant.

The day-glow data application of FY-3D IPM in monitoring O/N2

The Ionosphere Photometer (IPM) is a far ultraviolet nadir-viewing photometer that flew aboard the second-generation, polar-orbiting Chinese meteorological satellite FY-3D, which was launched on November 25th, 2017. The F2 layer peak electron density (NmF2) and O/N2 the column density ratio can be deduced by far ultraviolet measurements of night-time OI 135.6 nm emissions, which are produced by the recombination of O+ ions and electrons, and the day-time OI 135.6 nm and N2LBH wavelength emissions produced by the photoelectron impact excitation of atomic oxygen O and molecular nitrogen N2. Analysis of the IPM data indicated the stray light at 135.6 nm wavelength is under deducted. Based on comparison with the emissive intensity calculation of AURIC model, the day-time data was conducted to make a revision of stray light. The reliable factor (1.13) of stray light subtraction was obtained by fitting the median values of the observed data points per each latitude bin to the model data. According to the O/N2 error estimation from the estimated factor of the stray light, when the factor does not change by more than 0.03, the error of O/N2 ratio from the factor will not exceed 20%. The O/N2 changes retrieved from revised IPM data during storms in April and August 2018 are well correlated with Dst indices. The research results show that the IPM data could provide a good monitoring of O/N2 changes during magnetic storms.

ALCC-Glasses: Arriving Light Chroma Controllable Optical See-Through Head-Mounted Display System for Color Vision Deficiency Compensation

About 250 million people in the world suffer from color vision deficiency (CVD). Contact lenses and glasses with a color filter are available to partially improve the vision of people with CVD. Tinted glasses uniformly change the colors in a user’s field of view (FoV), which can improve the contrast of certain colors while making others hard to identify. On the other hand, an optical see-through head-mounted display (OST-HMD) provides a new alternative by applying a controllable overlay to a user’s FoV. The method of color calibration for people with CVD, such as the Daltonization process, needs to make the calibrated color darker, which has not yet been featured on recent commercial OST-HMDs. We propose a new approach to realize light subtraction on OST-HMDs using a transmissive LCD panel, a prototype system, named ALCC-glasses, to validate and demonstrate the new arriving light chroma controllable augmented reality technology for CVD compensation.

Accurate device-independent colorimetric measurements using smartphones.

Smartphones provide an ideal platform for colorimetric measurements due to their low cost, portability and image quality. As with any imaging-based colorimetry system, ambient light and device variations introduce error which must be dealt with. We propose a novel processing method consisting of a one-time calibration stage to account for inter-phone variations, and an innovative use of ambient light subtraction with image pairs to account for variation in ambient light. Data collection is kept very simple, making it particularly useful for use in the field, since nothing additional is required in the images. Ambient subtraction is first demonstrated for a range of colors and phones (Samsung S8 and LG Nexus 5X), and the Subtracted Signal to Noise Ratio (SSNR) is defined as a metric for assessing whether an image pair is appropriate at the time of image capture. The experimentally determined SSNR threshold below which to suggest retaking the images is 3.4. The classification accuracy for results using the proposed calibration pipeline is then compared to the simplest image metadata-based alternative and is found to be greatly superior. Finally, a custom colorcard is shown to improve the accuracy of device-independent results for known smaller ranges of colors over a standard colorcard, making this a possible application-specific modification to the overall processing pipeline.

Research on an Infrared Multi-Target Saliency Detection Algorithm under Sky Background Conditions

Aiming at solving the problem of incomplete saliency detection and unclear boundaries in infrared multi-target images with different target sizes and low signal-to-noise ratio under sky background conditions, this paper proposes a saliency detection method for multiple targets based on multi-saliency detection. The multiple target areas of the infrared image are mainly bright and the background areas are dark. Combining with the multi-scale top hat (Top-hat) transformation, the image is firstly corroded and expanded to extract the subtraction of light and shade parts and reconstruct the image to reduce the interference of sky blurred background noise. Then the image obtained by a multi-scale Top-hat transformation is transformed from the time domain to the frequency domain, and the spectral residuals and phase spectrum are extracted directly to obtain two kinds of image saliency maps by multi-scale Gauss filtering reconstruction, respectively. On the other hand, the quaternion features are extracted directly to transform the phase spectrum, and then the phase spectrum is reconstructed to obtain one kind of image saliency map by the Gauss filtering. Finally, the above three saliency maps are fused to complete the saliency detection of infrared images. The test results show that after the experimental analysis of infrared video photographs and the comparative analysis of Receiver Operating Characteristic (ROC) curve and Area Under the Curve (AUC) index, the infrared image saliency map generated by this method has clear target details and good background suppression effect, and the AUC index performance is good, reaching over 99%. It effectively improves the multi-target saliency detection effect of the infrared image under the sky background and is beneficial to subsequent detection and tracking of image targets.

Three-dimensional resolution enhancement in confocal microscopy with radially polarized illumination using subtractive imaging

A method based on the subtraction of images taken under radially polarized illumination is provided to improve the three-dimensional resolution in confocal microscopy. Radially polarized light and vortex phase modulated radially polarized light are used as confocal microscopy illumination light. Our numerical simulations predict that lateral resolutions close to 0.218λ is possible for practical confocal laser scanning microscopy with visible light. Theoretically, by applying radially polarized light and image subtraction method, we can enhance lateral resolution 47.3% higher than that in confocal microscopy with a pinhole of 0.3AU, and improve the axial resolving ability by 20.9% simultaneously. Simulation results of both 3D array model and cell microtubules are presented to verify the applicability and effectiveness of our method. In conclusion, the resolution of confocal microscopy using radially polarized light illumination and image subtraction could be improved. Compared with other resolution enhancement technologies, this method can offer significant spatial resolution improvements for fluorescence imaging at lower cost.

Host galaxies of high-redshift extremely red and obscured quasars

Abstract We present Hubble Space Telescope 1.4–1.6 $\mu$m images of the hosts of 10 extremely red quasars (ERQs) and six type 2 quasar candidates at z = 2–3. ERQs, whose bolometric luminosities range between 1047 and 1048 erg s−1, show spectroscopic signs of powerful ionized winds, whereas type 2 quasar candidates are less luminous and show only mild outflows. After performing careful subtraction of the quasar light, we clearly detect almost all host galaxies. The median rest-frame B-band luminosity of the ERQ hosts in our sample is $10^{11.2}\, \mathrm{L}_{\odot }$, or ∼4L* at this redshift. Two of the 10 hosts of ERQs are in ongoing mergers. The hosts of the type 2 quasar candidates are 0.6 dex less luminous, with 2/6 in likely ongoing mergers. Intriguingly, despite some signs of interaction and presence of low-mass companions, our objects do not show nearly as much major merger activity as do high-redshift radio-loud galaxies and quasars. In the absence of an overt connection to major ongoing gas-rich merger activity, our observations are consistent with a model in which the near-Eddington accretion and strong feedback of ERQs are associated with relatively late stages of mergers resulting in early-type remnants. These results are in some tension with theoretical expectations of galaxy formation models, in which rapid black hole growth occurs within a short time of a major merger. Type 2 quasar candidates are less luminous, so they may instead be powered by internal galactic processes.

A Three-Phase, One-Tap High Background Light Subtraction Time-of-Flight Camera

In this paper, a time-of-flight 3-D camera is presented for indoor/outdoor high-speed applications. A three-phase algorithm is proposed using one-tap/capacitor in-pixel background light subtraction. By integrating the background light only once, the standard four-phase time-of-flight operation is done in three-phases. The use of a single tap in the proposed pixel provides background light subtraction with lower mismatch and additionally, increases the camera speed. A $24 \times 24 $ pixel array image sensor, fabricated in AMS 0.35- $\mu \text{m}$ CMOS process is characterized in 2-D and 3-D mode for background light subtraction and distance estimation. The pixel pitch is $48~\mu \text{m}$ with 17.36% fill-factor. The sensor subtracts 125-klx background light with 8.2-cm distance offset at 80-cm object distance, without using an optical filter. The background-to-signal-ratio is 32.04 dB while frame-rate of the camera is 207 and 100 fps in 2-D and 3-D mode, respectively.

High-resolution spectroscopy and high contrast imaging with the ELT: looking for O2 in Proxima b

We research the requirements of High Contrast Imaging when combined with the cross correlation (CC) of high resolution spectra with known spectroscopic templates for detecting and characterising exoplanets in reflected light. We simulate applying the technique to a potentially habitable Proxima b-like planet and show that the O$_2$ A-band spectral feature could feasibly be detected on nearby rocky exoplanets using future instruments on the ELT . The technique is then more widely analysed showing that detections of planets and O$_2$ with signal to noise in the CC function (SNR$_{CC}$) > 3 can be obtained when the signal to noise of the simulated planet spectrum (SNR$_{spec}$) is from 0.25 to 1.2. We place constraints on the spectral resolution, instrument contrast, point spread function (PSF), exposure times and systematic error in stellar light subtraction for making such detections. We find that accurate stellar light subtraction (with 99.99% removal) and PSFs with high spatial resolutions are key to making detections. Lastly a further investigation suggests the ELT could potentially discover and characterise planets of all sizes around different spectral type stars, as well as detecting O$_2$ on Super-Earths with habitable zone orbits around nearby M stars.

Improving confocal microscopy resolution by tangentially polarized illumination and image subtraction

Abstract Confocal microscopy is widely used, but its resolution is limited. To improve confocal microscopy resolution, tangentially polarized illumination light and image subtraction are studied. Tangentially polarized light or vortex phase modulated tangentially polarized light are used as confocal microscopy illumination light. The effective point spread function difference of the confocal microscopy using tangentially polarized light and using vortex phase modulated tangentially polarized light is got first. The full width at half maximum of the point spread function difference is smaller. Simulation shows that the resolution of the confocal microscopy using tangentially polarized light illumination and image subtraction is increased by 19.9% compared with ordinary circularly polarized light. When compared with confocal microscopy using vortex phase modulated tangentially polarized light, simulation and fluorescence beads imaging experiment show that the resolution of the aforementioned confocal microscopy is improved by 13.6% and 11.2%. In conclusion, the resolution of confocal microscopy using tangentially polarized light illumination and image subtraction could be improved. Compared with other resolution enhancement technologies, this method is much simpler and does not need strong lasers.

A 125-klx Background Light Subtraction Architecture for 2-D and Time-of-Flight 3-D Cameras

In this paper, an in-pixel background light (BGL) subtraction architecture is presented for indoor/outdoor 2-D and 3-D imaging. The subtraction is performed using a pulsed modulation technique used in time-of-flight cameras. Mostly BGL subtraction is done using two capacitors. However, two capacitors cause mismatch effects; therefore, a single capacitor approach is proposed. Using a single capacitor, the BGL subtraction and distance estimation are performed in three operational phases. Hence, the proposed architecture can be used in applications where high-speed depth imaging is required. An image sensor with $24\times24$ pixel array is designed with 48- $\mu \text{m}$ pixel pitch and 17.36% fill factor. The measurement results of the chip fabricated in AMS 0.35- $\mu \text{m}$ CMOS OPTO process show up to 125-klx BGL subtraction without using an optical filter with a background-to-signal ratio of 40 dB.

Dark matter dynamics in Abell 3827: new data consistent with standard cold dark matter

AbstractWe present integral field spectroscopy of galaxy cluster Abell 3827, using Atacama Large Millimetre Array (ALMA) and Very Large Telescope/Multi-Unit Spectroscopic Explorer. It reveals an unusual configuration of strong gravitational lensing in the cluster core, with at least seven lensed images of a single background spiral galaxy. Lens modelling based on Hubble Space Telescope imaging had suggested that the dark matter associated with one of the cluster's central galaxies may be offset. The new spectroscopic data enable better subtraction of foreground light, and better identification of multiple background images. The inferred distribution of dark matter is consistent with being centred on the galaxies, as expected by Λ cold dark matter. Each galaxy's dark matter also appears to be symmetric. Whilst, we do not find an offset between mass and light (suggestive of self-interacting dark matter) as previously reported, the numerical simulations that have been performed to calibrate Abell 3827 indicate that offsets and asymmetry are still worth looking for in collisions with particular geometries. Meanwhile, ALMA proves exceptionally useful for strong lens image identifications.

MUSE-inspired view of the quasar Q2059-360, its Lyman α blob, and its neighborhood

The radio-quiet quasar Q2059-360 at redshift $z=3.08$ is known to be close to a small Lyman $\alpha$ blob (LAB) and to be absorbed by a proximate damped Ly$\alpha$ (PDLA) system. Here, we present the Multi Unit Spectroscopic Explorer (MUSE) integral field spectroscopy follow-up of this quasi-stellar object (QSO). Our primary goal is to characterize this LAB in detail by mapping it both spatially and spectrally using the Ly$\alpha$ line, and by looking for high-ionization lines to constrain the emission mechanism. Combining the high sensitivity of the MUSE integral field spectrograph mounted on the Yepun telescope at ESO-VLT with the natural coronagraph provided by the PDLA, we map the LAB down to the QSO position, after robust subtraction of QSO light in the spectral domain. In addition to confirming earlier results for the small bright component of the LAB, we unveil a faint filamentary emission protruding to the south over about 80 pkpc (physical kpc); this results in a total size of about 120 pkpc. We derive the velocity field of the LAB (assuming no transfer effects) and map the Ly$\alpha$ line width. Upper limits are set to the flux of the N V $\lambda 1238-1242$, C IV $\lambda 1548-1551$, He II $\lambda 1640$, and C III] $\lambda 1548-1551$ lines. We have discovered two probable Ly$\alpha$ emitters at the same redshift as the LAB and at projected distances of 265 kpc and 207 kpc from the QSO; their Ly$\alpha$ luminosities might well be enhanced by the QSO radiation. We also find an emission line galaxy at $z=0.33$ near the line of sight to the QSO. This LAB shares the same general characteristics as the 17 others surrounding radio-quiet QSOs presented previously. However, there are indications that it may be centered on the PDLA galaxy rather than on the QSO.