scholarly journals Calibrating photometric redshift measurements with the Multi-channel Imager (MCI) of the China Space Station Telescope (CSST)

2021 ◽  
Author(s):  
Ye Cao ◽  
Yan Gong ◽  
Zhenya Zheng ◽  
Chun Xu
Keyword(s):  
High Spatial Resolution ◽  
Filter Design ◽  
Signal To Noise Ratio ◽  
Space Station ◽  
Photometric Redshift ◽  
Upper Limit ◽  
Band Position ◽  
Wide Wavelength Range ◽  
Medium Band ◽  
Photometric Imaging

Abstract The China Space Station Telescope (CSST) photometric survey aims to perform a high spatial resolution (~0.15'') photometric imaging for the targets that cover a large sky area (~17,500 deg^2) and wide wavelength range (from NUV to NIR). It expects to explore the properties of dark matter, dark energy, and other important cosmological and astronomical areas. In this work, we evaluate whether the filter design of the Multi-channel Imager (MCI), one of the five instruments of the CSST, can provide accurate photometric redshift (photo-$z$) measurements with its nine medium-band filters to meet the relevant scientific objectives. We generate the mock data based on the COSMOS photometric redshift catalog with astrophysical and instrumental effects. The application of upper limit information of low signal-to-noise ratio (SNR) data is adopted in the estimation of photo-z. We investigate the dependency of photo-z accuracy on the filter parameters, such as band position and width. We find that the current MCI filter design can achieve good photo-z measurements with accuracy sigma_z~0.017 and outlier fraction f_c~2.2%. It can effectively improve the photo-z measurements of the main CSST survey using the Survey Camera (SC) to an accuracy sigma_z~0.015 and outlier fraction f_c~1.5%. It indicates that the original MCI filters are proper for the photo-z calibration.

Median Morphological Filter Design Based on the PSO Algorithm

2011 ◽  
Vol 128-129 ◽  
pp. 181-184
Author(s):  
You Lian Zhu ◽  
Cheng Huang
Keyword(s):  
Filter Design ◽  
Design Method ◽  
Signal To Noise Ratio ◽  
Pso Algorithm ◽  
Morphological Operations ◽  
Morphological Filter ◽  
Signal To Noise ◽  
Noise Ratio ◽  
The Cost ◽  
Filter Design Method

Design of morphological filter greatly depends on morphological operations and structuring elements selection. A filter design method used median closing morphological operation is proposed to enhance the image denoising ability and the PSO algorithm is introduced for structural elements selecting. The method takes the peak value signal-to-noise ratio (PSNR) as the cost function and may adaptively build unit structuring elements with zero square matrix. Experimental results show the proposed method can effectively remove impulse noise from a noisy image, especially from a low signal-to-noise ratio (SNR) image; the noise reduction performance has obvious advantages than the other.

scholarly journals Discovery of allenyl acetylene, H2CCCHCCH, in TMC-1

2021 ◽  
Vol 647 ◽  
pp. L3 ◽  
Author(s):  
J. Cernicharo ◽  
C. Cabezas ◽  
M. Agúndez ◽  
B. Tercero ◽  
N. Marcelino ◽  
...  
Keyword(s):  
Column Density ◽  
State Of The Art ◽  
Rotational Temperature ◽  
Signal To Noise Ratio ◽  
Laboratory Data ◽  
The Other ◽  
Signal To Noise ◽  
Chemical Models ◽  
Upper Limit

We present the discovery in TMC-1 of allenyl acetylene, H2CCCHCCH, through the observation of nineteen lines with a signal-to-noise ratio ∼4–15. For this species, we derived a rotational temperature of 7 ± 1 K and a column density of 1.2 ± 0.2 × 1013 cm−2. The other well known isomer of this molecule, methyl diacetylene (CH3C4H), has also been observed and we derived a similar rotational temperature, Tr = 7.0 ± 0.3 K, and a column density for its two states (A and E) of 6.5 ± 0.3 × 1012 cm−2. Hence, allenyl acetylene and methyl diacetylene have a similar abundance. Remarkably, their abundances are close to that of vinyl acetylene (CH2CHCCH). We also searched for the other isomer of C5H4, HCCCH2CCH (1.4-Pentadiyne), but only a 3σ upper limit of 2.5 × 1012 cm−2 to the column density can be established. These results have been compared to state-of-the-art chemical models for TMC-1, indicating the important role of these hydrocarbons in its chemistry. The rotational parameters of allenyl acetylene have been improved by fitting the existing laboratory data together with the frequencies of the transitions observed in TMC-1.

scholarly journals Shadow monochromatic backlighting: Large-field high resolution X-ray shadowgraphy with improved spectral tunability

2001 ◽  
Vol 19 (2) ◽  
pp. 285-293 ◽  
Author(s):  
T.A. PIKUZ ◽  
A. YA. FAENOV ◽  
M. FRAENKEL ◽  
A. ZIGLER ◽  
F. FLORA ◽  
...  
Keyword(s):  
High Resolution ◽  
High Spatial Resolution ◽  
Field Of View ◽  
Large Field ◽  
X Ray ◽  
Traditional Scheme ◽  
Wide Range ◽  
Wide Wavelength Range ◽  
Bent Crystals ◽  
First Time

The shadow monochromatic backlighting (SMB) scheme, a modification of the well-known soft X-ray monochromatic backlighting scheme, is proposed. It is based on a spherical crystal as the dispersive element and extends the traditional scheme by allowing one to work with a wide range of Bragg angles and thus in a wide spectral range. The advantages of the new scheme are demonstrated experimentally and supported numerically by ray-tracing simulations. In the experiments, the X-ray backlighter source is a laser-produced plasma, created by the interaction of an ultrashort pulse, Ti:Sapphire laser (120 fs, 3–5 mJ, 1016 W/cm2 on target) or a short wavelength XeCl laser (10 ns, 1–2 J, 1013 W/cm2 on target) with various solid targets (Dy, Ni + Cr, BaF2). In both experiments, the X-ray sources are well localized spatially (∼20 μm) and are spectrally tunable in a relatively wide wavelength range (λ = 8–15 Å). High quality monochromatic (δλ/λ ∼ 10−5–10−3) images with high spatial resolution (up to ∼4 μm) over a large field of view (a few square millimeters) were obtained. Utilization of spherically bent crystals to obtain high-resolution, large field, monochromatic images in a wide range of Bragg angles (35° < Θ < 90°) is demonstrated for the first time.

scholarly journals The development of non-coherent passive radar techniques for space situational awareness with the Murchison Widefield Array

2020 ◽  
Vol 37 ◽  
Author(s):  
Steve Prabu ◽  
Paul J. Hancock ◽  
Xiang Zhang ◽  
Steven J. Tingay
Keyword(s):  
Situational Awareness ◽  
Signal To Noise Ratio ◽  
Space Station ◽  
Passive Radar ◽  
Space Situational Awareness ◽  
Direct Path ◽  
Orbital Parameters ◽  
Ratio Spectrum ◽  
Murchison Widefield Array ◽  
Future Work

Abstract The number of active and non active satellites in Earth orbit has dramatically increased in recent decades, requiring the development of novel surveillance techniques to monitor and track them. In this paper, we build upon previous non-coherent passive radar space surveillance demonstrations undertaken using the Murchison Widefield Array (MWA). We develop the concept of the Dynamic Signal to Noise Ratio Spectrum (DSNRS) in order to isolate signals of interest (reflections of FM transmissions of objects in orbit) and efficiently differentiate them from direct path reception events. We detect and track Alouette-2, ALOS, UKube-1, the International Space Station, and Duchifat-1 in this manner. We also identified out-of-band transmissions from Duchifat-1 and UKube-1 using these techniques, demonstrating the MWA’s capability to look for spurious transmissions from satellites. We identify an offset from the locations predicted by the cataloged orbital parameters for some of the satellites, demonstrating the potential of using MWA for satellite catalog maintenance. These results demonstrate the capability of the MWA for Space Situational Awareness and we describe future work in this area.

Feasibility Study of a Capacitive MEMS Filter Using Electrostatic Levitation

2019 ◽  
Author(s):  
Mark Pallay ◽  
Shahrzad Towfighian
Keyword(s):  
Mechanical Response ◽  
Filter Design ◽  
Signal To Noise Ratio ◽  
Capacitive Sensor ◽  
Electrostatic Levitation ◽  
Plate Electrode ◽  
System A ◽  
Capacitive Mems ◽  
Mems Filter ◽  
Large Output

Abstract We introduce a capacitive MEMS filter that uses electrostatic levitation for actuation and sensing. The advantage of this electrode configuration is that it does not suffer from the pull-in instability and therefore tremendously high voltages can be applied to this system. A large sensing voltage will produce a large output signal, which boosts the signal to noise ratio. The filter outputs about a 110mV peak-to-peak signal when operated at 175V, and can be boosted to 175mV by increasing the voltage to 250V. Because pull-in is eliminated, voltages much higher than 250V can be applied. An outline of the filter design and operating principle is discussed. A model of the filter is derived and analyzed to show the mechanical response and approximate peak-to-peak signal output. This study shows the feasibility of a capacitive sensor that is based on electrostatic levitation, and outlines the advantages it has over traditional parallel-plate electrode configurations. This design is promising for signal signal processing applications where large strokes are important.

scholarly journals Multifrequency filter search for high redshift sources and lensing systems in Herschel-ATLAS

2019 ◽  
Vol 622 ◽  
pp. A106
Author(s):  
A. Manjón-García ◽  
D. Herranz ◽  
J. M. Diego ◽  
L. Bonavera ◽  
J. González-Nuevo
Keyword(s):  
Signal To Noise Ratio ◽  
High Redshift ◽  
Simulated Data ◽  
Galaxy Cluster ◽  
Point Sources ◽  
Sloan Digital Sky Survey ◽  
Large Area ◽  
Redshift Range ◽  
Photometric Redshift ◽  
Area Survey

We present a new catalog of high-redshift candidate Herschel sources. Our sample is obtained after applying a multifrequency filtering method (“matched multifilter”), which is designed to improve the signal-to-noise ratio of faint extragalactic point sources. The method is tested against already-detected sources from the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) and used to search for new high-redshift candidates. The multifilter technique also produces an estimation of the photometric redshift of the sources. When compared with a sample of sources with known spectroscopic redshift, the photometric redshift returned from the multifilter is unbiased in the redshift range 0.8 <  z <  4.3. Using simulated data we reproduced the same unbiased result in roughly the same redshift range and determined the error (and bias above z ≈ 4) in the photometric redshifts. Based on the multifilter technique, and a selection based on color, flux, and agreement of fit between the observed photometry and assumed SED, we find 370 robust candidates to be relatively bright high-redshift sources. A second sample with 237 objects focuses on the faint end at high-redshift. These 237 sources were previously near the H-ATLAS detection limit but are now confirmed with our technique as high significance detections. Finally, we look for possible lensed Herschel sources by cross-correlating the first sample of 370 objects with two different catalogs of known low-redshift objects, the redMaPPer Galaxy Cluster Catalog and a catalog of galaxies with spectroscopic redshift from the Sloan Digital Sky Survey Data Release 14. Our search renders a number of candidates to be lensed systems from the SDSS cross-correlation but none from the redMaPPeR confirming the more likely galactic nature of the lenses.

scholarly journals Cosmological lensing ratios with DES Y1, SPT, and Planck

2019 ◽  
Vol 487 (1) ◽  
pp. 1363-1379 ◽  
Author(s):  
J Prat ◽  
E Baxter ◽  
T Shin ◽  
C Sánchez ◽  
C Chang ◽  
...  
Keyword(s):  
Gravitational Lensing ◽  
Correlation Functions ◽  
Signal To Noise Ratio ◽  
Cosmic Time ◽  
Cosmological Constraints ◽  
Photometric Redshift ◽  
Dark Energy Survey ◽  
Systematic Uncertainties ◽  
South Pole Telescope ◽  
Curvature Parameter

ABSTRACTCorrelations between tracers of the matter density field and gravitational lensing are sensitive to the evolution of the matter power spectrum and the expansion rate across cosmic time. Appropriately defined ratios of such correlation functions, on the other hand, depend only on the angular diameter distances to the tracer objects and to the gravitational lensing source planes. Because of their simple cosmological dependence, such ratios can exploit available signal-to-noise ratio down to small angular scales, even where directly modelling the correlation functions is difficult. We present a measurement of lensing ratios using galaxy position and lensing data from the Dark Energy Survey, and CMB lensing data from the South Pole Telescope and Planck, obtaining the highest precision lensing ratio measurements to date. Relative to the concordance ΛCDM model, we find a best-fitting lensing ratio amplitude of A = 1.1 ± 0.1. We use the ratio measurements to generate cosmological constraints, focusing on the curvature parameter. We demonstrate that photometrically selected galaxies can be used to measure lensing ratios, and argue that future lensing ratio measurements with data from a combination of LSST and Stage-4 CMB experiments can be used to place interesting cosmological constraints, even after considering the systematic uncertainties associated with photometric redshift and galaxy shear estimation.

Solar Cell Defects Detection Using Lock-In Amplifier

2012 ◽  
Vol 512-515 ◽  
pp. 276-279 ◽  
Author(s):  
Iat Fai Leong ◽  
Jing Jing Fang ◽  
Joseph Liao
Keyword(s):  
Solar Cell ◽  
High Spatial Resolution ◽  
Detection System ◽  
Signal To Noise Ratio ◽  
Ccd Camera ◽  
Inspection System ◽  
Signal To Noise ◽  
Excitation Light ◽  
Processing Control ◽  
Lock In

In this research we present a Lock-In amplifier photoluminescence image (PLI) detection system. Using a commercially available CCD camera, combined with a modulated excitation light source system, Lock-In amplifier technique is employed to enhance the sensitivity and signal-to-noise ratio of the image. Using a high resolution camera, we developed a high spatial resolution non-contact inspection system for solar cell. Each solar cell can be examined within 2s relevant for inline processing control.

scholarly journals Probing the existence of a rich galaxy overdensity at z = 5.2

2021 ◽  
Author(s):  
Rosa Calvi ◽  
Helmut Dannerbauer ◽  
Pablo Arrabal Haro ◽  
José M Rodríguez Espinosa ◽  
Casiana Muñoz-Tuñón ◽  
...  
Keyword(s):  
Central Region ◽  
Clustering Analysis ◽  
Large Scale ◽  
Rest Frame ◽  
Physical Space ◽  
Far Infrared ◽  
Photometric Redshift ◽  
The Galaxy ◽  
Medium Band

Abstract We report the results of a pilot spectroscopic program of a region at z = 5.2 in the GOODS-N field containing an overdensity of galaxies around the well-known submillimeter galaxy HDF850.1. We have selected candidate cluster members from the optical 25 medium-band photometric catalog of the project SHARDS (Survey for High-z Absorption Red and Dead Sources). 17 rest-frame UV selected galaxies (LAEs and LBGs) with 5.15&lt;zphot&lt;5.27, candidates to be physically associated with the overdensity, have been observed with the instrument OSIRIS at the GranTeCan telescope. 13 out of these 17 (76 per cent) sources have secure spectroscopic confirmations via the Lyα line at the redshift of the galaxy protocluster PCl−HDF850.1, demonstrating the high reliabilty of our photometric redshift method. 10 out of 13 sources are newly confirmed members. Thus, we increase the number of confirmed members in this overdensity from 13 to 23 objects. In order to fully characterize this structure we combined our dataset with the sample from the literature. Beside the SMG HDF850.1, none of the 23 spectroscopically confirmed members are bright in the far-infrared/submm wavelength regime (SFRIR &lt; few hundred M⊙ yr−1). The clustering analysis of the whole sample of 23 confirmed members reveals four distinct components in physical space in different evolutionary states, within Δz &lt; 0.04 from the central region hosting SMG HDF850.1. The halo mass of the whole structure at z = 5.2, estimated by a variety of methods, range between 2 − 8 × 1012M⊙. The comparison with literature suggests a large scale assembly comparable to the formation of a central Virgo-like cluster at z=0 with several satellite components which will possibly be incorporated in a single halo if the protocluster is the progenitor of a more massive Coma-like cluster (&gt;1015M⊙).

scholarly journals Photometric redshifts from SDSS images using a convolutional neural network

2018 ◽  
Vol 621 ◽  
pp. A26 ◽  
Author(s):  
Johanna Pasquet ◽  
E. Bertin ◽  
M. Treyer ◽  
S. Arnouts ◽  
D. Fouchez
Keyword(s):  
Neural Network ◽  
Convolutional Neural Network ◽  
Signal To Noise Ratio ◽  
Distribution Functions ◽  
Sloan Digital Sky Survey ◽  
Photometric Redshifts ◽  
Photometric Redshift ◽  
Probability Distribution Functions ◽  
Sky Survey ◽  
Galaxy Sample

We developed a deep convolutional neural network (CNN), used as a classifier, to estimate photometric redshifts and associated probability distribution functions (PDF) for galaxies in the Main Galaxy Sample of the Sloan Digital Sky Survey at z <  0.4. Our method exploits all the information present in the images without any feature extraction. The input data consist of 64 × 64 pixel ugriz images centered on the spectroscopic targets, plus the galactic reddening value on the line-of-sight. For training sets of 100k objects or more (≥20% of the database), we reach a dispersion σMAD <  0.01, significantly lower than the current best one obtained from another machine learning technique on the same sample. The bias is lower than 10−4, independent of photometric redshift. The PDFs are shown to have very good predictive power. We also find that the CNN redshifts are unbiased with respect to galaxy inclination, and that σMAD decreases with the signal-to-noise ratio (S/N), achieving values below 0.007 for S/N >  100, as in the deep stacked region of Stripe 82. We argue that for most galaxies the precision is limited by the S/N of SDSS images rather than by the method. The success of this experiment at low redshift opens promising perspectives for upcoming surveys.

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