A5101510967- Astrophysics and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Astrophysical Phenomena and Observations
- Pulsars and Gravitational Waves Research
- Photoacoustic and Ultrasonic Imaging
- Optical measurement and interference techniques
- Soil Moisture and Remote Sensing
- GNSS positioning and interference
- Gamma-ray bursts and supernovae
- Geophysics and Gravity Measurements
- Adaptive optics and wavefront sensing
- Galaxies: Formation, Evolution, Phenomena
- Particle Accelerators and Free-Electron Lasers
- Cosmology and Gravitation Theories
- Structural Health Monitoring Techniques
- Dark Matter and Cosmic Phenomena
- Superconducting and THz Device Technology
- Optical Polarization and Ellipsometry
- Ultrasound Imaging and Elastography
- Digital Transformation in Industry
- Image and Signal Denoising Methods
- Electron and X-Ray Spectroscopy Techniques
- Relativity and Gravitational Theory
- Sparse and Compressive Sensing Techniques
- Atmospheric Ozone and Climate
Max Planck Institute for Radio Astronomy
2022-2024
National Radio Astronomy Observatory
2024
Max Planck Institute for Research on Collective Goods
2023
Hochschule Fresenius
2023
King's College London
2022
University of Göttingen
2020-2021
The next-generation Event Horizon Telescope (ngEHT) will be a significant enhancement of the (EHT) array, with ∼10 new antennas and instrumental upgrades existing antennas. increased uv-coverage, sensitivity, frequency coverage allow wide range science opportunities to explored. ngEHT Analysis Challenges have been launched inform development array design, objectives, analysis pathways. For each challenge, synthetic EHT datasets are generated from theoretical source models released challenge...
Context. Very long baseline interferometry (VLBI) is a radio-astronomical technique whereby the correlated signal from various baselines combined into an image of highest possible angular resolution. Due to sparsity measurements, this imaging procedure constitutes ill-posed inverse problem. For decades, CLEAN algorithm has been standard choice in VLBI studies, despite it bringing on some serious disadvantages and pathologies that are brought by requirements modern frontline applications....
In the past few years, Event Horizon Telescope (EHT) has provided first-ever event horizon-scale images of supermassive black holes (BHs) (M87*) and Sagittarius A$^*$ (Sgr A*). The next-generation EHT project is an extension array that promises larger angular resolution higher sensitivity to dim, extended flux around central ring-like structure, possibly connecting accretion flow jet. ngEHT Analysis Challenges aim understand science extractability from synthetic movies inform design analysis...
We present results from the first 22 GHz space very-long-baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part Nearby AGN Key Science Program, source was observed in Feb 2014 at with 21 ground stations, reaching projected $(u,v)$-spacings up to $\sim11\,$G$\lambda$. The experiment complemented snapshot RadioAstron data obtained during 2013--2016 Survey Program. Their longest baselines extend $\sim25\,$G$\lambda$. For all these measurements, fringes are...
Reconstructing images from very long baseline interferometry (VLBI) data with sparse sampling of the Fourier domain (uv-coverage) constitutes an ill-posed deconvolution problem. It requires application robust algorithms maximizing information extraction all sampled spatial scales and minimizing influence unsampled on image quality. We develop a new multiscale wavelet algorithm DoG-HiT for imaging sparsely interferometric which combines difference Gaussian (DoG) wavelets hard thresholding...
Context. Imaging in radioastronomy is an ill-posed inverse problem. However, with increasing sensitivity and capabilities of telescopes, several strategies have been developed order to solve this challenging In particular, novel algorithms recently proposed using (constrained) nonlinear optimization Bayesian inference. Aims. The Event Horizon Telescope (EHT) Collaboration convincingly investigated the fidelity their image reconstructions large surveys, solving reconstruction problem...
Self-calibration methods with the CLEAN algorithm have been widely employed in Very Long Baseline Interferometry (VLBI) data processing order to correct antenna-based amplitude and phase corruptions present data. However, human interaction during conventional self-calibration process can impose a strong effective prior, which turn may produce artifacts within final image hinder reproducibility of results. In this work, we aim demonstrate combined imaging method for VLBI Bayesian inference...
The composition and magnetic field morphology of relativistic jets can be studied using circular polarization (CP) measurement. Recent three-dimensional magnetohydrodynamic (3D RMHD) simulations coupled with radiative transfer (RT) calculations make strong predictions about the level (and morphology) jet's CP emission. These show that sign electric vector position angle (EVPA) are both sensitive to within radio core. We probe this theory by exploring whether core EVPA orientation is...
The galaxy M87 is one of the prime targets for high resolution radio imaging to investigate ring-like "shadow" its supermassive black hole, innermost regions accretion flow, and formation relativistic jet. However, it remains challenging observe them jointly due sparsity UV coverage limited array sensitivity. In 2018, global mm-VLBI (GMVA)+ALMA observations at 86,GHz enabled simultaneous reconstruction a ring structure extended jet emission. order analyze M87, conventional CLEAN algorithms...
The deconvolution, imaging, and calibration of data from radio interferometers is a challenging computational (inverse) problem. upcoming generation telescopes poses significant challenges to existing well-proven reduction pipelines, due the large sizes expected these experiments high resolution dynamic range. In this manuscript we deal with deconvolution A variety multiscalar variants classical CLEAN algorithm (the de facto standard) have been proposed in past, often outperforming at cost...
Recently multiscale imaging approaches such as DoG-HiT were developed to solve the VLBI problem and showed a promising performance: they are fast, accurate, unbiased automatic. We extend multiscalar approach polarimetric imaging, reconstructions of dynamically evolving sources finally dynamic reconstructions. These extensions (mr-support imaging) utilize approach. The time-averaged Stokes I image is decomposed by wavelet transform into single subbands. use set statistically significant...
Context . In very long baseline interferometry (VLBI), signals recorded at multiple antennas are combined to form a sparsely sampled virtual aperture with an effective diameter set by the largest separation between antennas. Due sparsity of aperture, VLBI imaging constitutes ill-posed inverse problem. Various algorithms have been employed deal imaging, including recently proposed multiobjective evolutionary algorithm decomposition (MOEA/D) described in first paper this series. Aims Among...
Context. Reconstructing an image from noisy, sparsely sampled Fourier data is ill-posed inverse problem that occurs in a variety of subjects within science, including analysis for Very Long Baseline Interferometry (VLBI) and the Spectrometer/Telescope Imaging X-rays (STIX) with respect to solar observations. The need high-resolution, high-fidelity imaging fosters active development range novel algorithms different algorithmic settings. However, despite these ongoing, parallel developments,...
Context . In very long baseline interferometry (VLBI), the combination of multiple antennas permits synthesis a virtual telescope with larger diameter and consequently higher resolution than individual antennas. However, due to sparse nature array, recovering an image from observed data is challenging ill-posed inverse problem. Aims The VLBI community interested in not only total intensity interferometric data, but also obtaining results polarimetric temporal domain. Only few algorithms are...
Context . The reconstruction of the polarization a source in radio interferometry is challenging calibration problem since strongly depends on gains and leakages, which need to be inferred along with image. This particularly true for Event Horizon Telescope (EHT) due its small number antennas, low signal-to-noise ratio, large gain corruptions. Aims To recover linear polarization, one has either infer leakages together image structure or rely completely calibration-independent closure...
Dilatons (and moduli) couple to the masses and coupling constants of ordinary matter, these quantities are fixed by local value dilaton field. If, in addition, with mass ${m}_{\ensuremath{\phi}}$ contributes cosmic dark matter density, then such oscillate time at Compton frequency. We show how oscillations lead broadening shifting Voigt profile Lyman-$\ensuremath{\alpha}$ forest a manner that is correlated density. further tomographic methods allow effect be reconstructed observing spectrum...
ABSTRACT We present a novel procedure to estimate the equation of state intergalactic medium in quasi-linear regime structure formation based on Ly α forest tomography and apply it 21 high-quality quasar spectra from UVES_SQUAD survey at redshift z = 2.5. Our estimation is full tomographic inversion line sight. invert data with two different algorithms, iterative Gauss–Newton method regularized probability conservation approach, which depend priors compare results flux space density space....
We present a same-level comparison of the most prominent inversion methods for reconstruction matter density field in quasi-linear regime from Ly$\alpha$ forest flux. Moreover, we pathway refining framework numerical optimization. apply this approach to construct novel hybrid method. The which are used so far reconstructions Richardson-Lucy algorithm, an iterative Gauss-Newton method and statistical assuming one-to-one correspondence between study these high spectral resolutions such that...
We present results from the first 22 GHz space very-long-baseline interferometric (VLBI) imaging observations of M87 by RadioAstron. As a part Nearby AGN Key Science Program, source was observed in Feb 2014 at with 21 ground stations, reaching projected $(u,v)$-spacings up to $\sim11\,$G$λ$. The experiment complemented snapshot RadioAstron data obtained during 2013--2016 Survey Program. Their longest baselines extend $\sim25\,$G$λ$. For all these measurements, fringes are detected only...
Reconstructing an image from sparsely sampled Fourier data is ill-posed inverse problem that occurs in a variety of subjects within science, including the analysis for Very Long Baseline Interferometry (VLBI) and Spectrometer/Telescope Imaging X-rays (STIX) solar observations. Despite ongoing parallel developments novel imaging algorithms, synergies remain unexplored. We study between STIX instrument VLBI, compare methodologies evaluate their potential. In this way, we identify key trends...
In Very Long Baseline Interferometry (VLBI), signals from multiple antennas combine to create a sparsely sampled virtual aperture, its effective diameter determined by the largest antenna separation. The inherent sparsity makes VLBI imaging an ill-posed inverse problem, prompting use of algorithms like Multiobjective Evolutionary Algorithm Decomposition (MOEA/D), as proposed in first paper this series. This study focuses on extending MOEA/D polarimetric and time dynamic reconstructions,...
In very long baseline interferometry (VLBI) the combination of multiple antennas permits synthesis a virtual telescope with larger diameter and consequently higher resolution than individual antennae. Yet, due to sparse nature array, recovering an image from observed data is challenging ill-posed inverse problem. The VLBI community interested in not only total intensity interferometric data, but also obtain results polarimetric temporal domain. Only few algorithms are able work all these...
Interstellar neutral (ISN) hydrogen is the most abundant species in outer heliosheath and very local interstellar medium (VLISM). Charge exchange collisions result filtration, reducing ISN density inside heliosphere. Additionally, these atoms are intensively ionized close to Sun, resulting a substantial reduction of their within few au from Sun. The products this ionization - pickup ions (PUIs) detected by charged particle detectors. Solar Wind Around Pluto (SWAP) instrument on New Horizons...
The reconstruction of the polarization a source in radio interferometry is challenging calibration problem since strongly depends on gains and leakages that need to be inferred along with image. This particularly true for Event Horizon Telescope (EHT) due its small number antennas, signal-to-noise ratio large gain corruptions. To recover linear polarization, one either has infer together image structure, or rely completely independent closure quantities. While first approach been explored...