Helge Rottmann
A5052232748- Astrophysics and Cosmic Phenomena
- Astrophysical Phenomena and Observations
- Radio Astronomy Observations and Technology
- Pulsars and Gravitational Waves Research
- Superconducting and THz Device Technology
- GNSS positioning and interference
- Gamma-ray bursts and supernovae
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Geophysics and Gravity Measurements
- Galaxies: Formation, Evolution, Phenomena
- Particle Accelerators and Free-Electron Lasers
- Stellar, planetary, and galactic studies
- Ionosphere and magnetosphere dynamics
- Mechanics and Biomechanics Studies
- Advanced X-ray Imaging Techniques
- Atmospheric Ozone and Climate
- Soil Moisture and Remote Sensing
- Historical Astronomy and Related Studies
- Atomic and Subatomic Physics Research
- Solar and Space Plasma Dynamics
- Neutrino Physics Research
- Relativity and Gravitational Theory
- Adaptive optics and wavefront sensing
- Wireless Communication Networks Research
Max Planck Institute for Radio Astronomy
2016-2025
Max Planck Society
2015-2020
W.M. Keck Observatory
2016
National Radio Astronomy Observatory
2016
National Astronomical Observatory of Japan
2016
Institute of Astronomy and Astrophysics, Academia Sinica
2016
University of Concepción
2011-2016
Atacama Large Millimeter Submillimeter Array
2016
Boston University
2016
Center for Astrophysics Harvard & Smithsonian
2016
Software correlation, where a correlation algorithm written in high-level language such as C++ is run on commodity computer hardware, has become increasingly attractive for small to medium sized and/or bandwidth constrained radio interferometers. In particular, many long baseline arrays (which typically have fewer than 20 elements and are restricted observing by costly recording hardware media) utilized software correlators rapid, cost-effective correlator upgrades allow compatibility with...
The nearby radio galaxy M87 is a prime target for studying black hole accretion and jet formation1,2. Event Horizon Telescope observations of in 2017, at wavelength 1.3 mm, revealed ring-like structure, which was interpreted as gravitationally lensed emission around central hole3. Here we report images obtained 2018, 3.5 showing that the compact core spatially resolved. High-resolution imaging shows structure [Formula: see text] Schwarzschild radii diameter, approximately 50% larger than...
Abstract The Galactic center supermassive black hole Sagittarius A* (Sgr A*) is one of the most promising targets to study dynamics accretion and outflow via direct imaging with very long baseline interferometry (VLBI). At 3.5 mm (86 GHz), emission from Sgr resolvable Global Millimeter VLBI Array (GMVA). We present first observations phased Atacama Large Millimeter/submillimeter (ALMA) joining GMVA. Our achieve an angular resolution ∼87 μ as, improving upon previous experiments by a factor...
The Galactic Center black hole Sagittarius A* (Sgr A*) is a prime observing target for the Event Horizon Telescope (EHT), which can resolve 1.3 mm emission from this source on angular scales comparable to that of general relativistic shadow. Previous EHT observations have used visibility amplitudes infer morphology millimeter-wavelength emission. Potentially much richer information contained in phases. We report phase Sgr obtained with total 13 nights over 4 years. Closure phases, sum phases...
The Atacama Millimeter/submillimeter Array (ALMA) Phasing Project (APP) has developed and deployed the hardware software necessary to coherently sum signals of individual ALMA antennas record aggregate in Very Long Baseline Interferometry (VLBI) Data Exchange Format. These beamforming capabilities allow array collectively function as equivalent a single large aperture participate global VLBI arrays. inclusion phased current networks operating at (sub)millimeter wavelengths provides an order...
Abstract We report results from very long baseline interferometric (VLBI) observations of the supermassive black hole in Galactic center, Sgr A*, at 1.3 mm (230 GHz). The were performed 2013 March using six VLBI stations Hawaii, California, Arizona, and Chile. Compared to earlier observations, addition APEX telescope Chile almost doubles longest length array, provides additional uv coverage N–S direction, leads a spatial resolution ∼30 μ as (∼3 Schwarzschild radii) for A*. source is detected...
We report the development of a semi-automatic pipeline for calibration 86 GHz full-polarization observations performed with Global Millimeter-VLBI array (GMVA) and describe strategy followed in data reduction. Our involves non-standard procedures, since VLBI polarimetry at frequencies above 43 is not yet well established. also present, first time, global-VLBI image (source 3C 345), as an example final product our pipeline, discuss effect instrumental limitations on fidelity polarization...
We present a detailed description of the special procedures for calibration and quality assurance Atacama Large Millimeter/submillimeter Array (ALMA) observations in Very Long Baseline Interferometry (VLBI) mode. These are required to turn phased ALMA array into fully calibrated VLBI station. As an illustration these methodologies, we full-polarization carried out with as at 3mm (Band 3) 1.3mm 6) part Cycle-4. first science conducted were obtained during 2017 campaign concert other...
The first very long baseline interferometry (VLBI) detections at 870$\mu$m wavelength (345$\,$GHz frequency) are reported, achieving the highest diffraction-limited angular resolution yet obtained from surface of Earth, and highest-frequency example VLBI technique to date. These include strong for multiple sources observed on inter-continental baselines between telescopes in Chile, Hawaii, Spain, during observations October 2018. longest-baseline approach 11$\,$G$\lambda$ corresponding an...
Wide-field surveys are a commonly-used method for studying thousands of objects simultaneously, to investigate, e.g., the joint evolution star-forming galaxies and active galactic nuclei. VLBI observations can yield valuable input such studies because they able identify AGN. However, large swaths sky impractical using standard methods, fields view order 10" or less. We have embarked on project carry out Very Long Baseline Array (VLBA) all 96 known radio sources in one best-studied areas sky,...
Abstract Frequency phase transfer (FPT) is a technique designed to increase coherence and sensitivity in radio interferometry by making use of the nondispersive nature troposphere calibrate high-frequency data using solutions derived at lower frequency. While Korean very long baseline (VLBI) network has pioneered simultaneous multiband systems for routine FPT up an observing frequency 130 GHz, this remains largely untested (sub)millimeter regime. A recent effort been made outfit dual-band...
An international consortium is presently constructing a beamformer for the Atacama Large Millimeter/submillimeter Array (ALMA) in Chile that will be available as facility instrument. The aggregate entire collecting area of array into single, very large aperture. extraordinary sensitivity phased ALMA, combined with extremely fine angular resolution on baselines to Northern Hemisphere, enable transformational new long baseline interferometry (VLBI) observations Bands 6 and 7 (1.3 0.8 mm)...
An astrometry project on PSR B1257+12, a millisecond pulsar with planetary system, has been carried out the Very Long Baseline Array and European Interferometry (VLBI) Network at central frequencies of 1465 1540 MHz, respectively. This consists nine epochs phase-referenced observations spanning about two years. Model-independent estimates distance velocity this have obtained using VLBI for first time. The precise to B1257+12 is 710−38+43 pc. in agreement timing results, but larger than...
Abstract The development of the Atacama Large Millimeter/submillimeter Array (ALMA) phasing system (APS) has allowed ALMA to function as an extraordinarily sensitive station for very long baseline interferometry (VLBI) at frequencies up 230 GHz ( λ ≈ 1.3 mm). Efforts are now underway extend use APS 345 0.87 Here we report a characterization performance based on series tests carried out between 2015 and 2021, including successful global VLBI test campaign conducted in 2018 October...
Abstract We report on the first pulsar and transient survey of Galactic Center (GC) with Atacama Large Millimeter/submillimeter Array (ALMA). The observations were conducted during Global Millimeter VLBI campaign in 2017 2018. carry out searches using time series both total intensity other polarization components form Stokes parameters. incorporate acceleration its derivative search, also search segments entire observation to compensate for potential orbital motion pulsar. While no new is...
We report about a 230 GHz very long baseline interferometry (VLBI) fringe finder observation of blazar 3C 279 with the APEX telescope in Chile, phased submillimeter array (SMA), and SMT Arizona Radio Observatory (ARO). installed VLBI equipment measured station position to 1 cm accuracy (1 sigma). then observed on 2012 May 7 5 hour track lengths 2800 M$\lambda$ 7200 finest spacing 28.6 micro-arcseconds. Fringes were detected all baselines SNRs 12 55 420 s. The correlated flux density longest...
Abstract In 2017 the Event Horizon Telescope (EHT) observed supermassive black hole at center of Milky Way, Sagittarius A* (Sgr A*), a frequency 228.1 GHz ( λ = 1.3 mm). The fundamental physics tests that even single pulsar orbiting Sgr would enable motivate searching for pulsars in EHT data sets. high observing means pulsars—which typically exhibit steep emission spectra—are expected to be very faint. However, it also negates pulse scattering, an effect could hinder detections Galactic...
The advancement of the Event Horizon Telescope has enabled study relativistic jets in active galactic nuclei down to sub-parsec linear scales even at high redshift. Quasi-simultaneous multifrequency observations provide insights into physical conditions compact regions and allow accretion theories be tested. Initially, we aimed measure magnetic field strength close central supermassive black hole by studying frequency-dependent opacity jet matter, Faraday rotation, spectral index...
We report on the first detection of pulsed radio emission from a pulsar with ALMA telescope. The was made in Band-3 frequency range (85-101 GHz) using phased-array mode developed for VLBI observations. A software pipeline has been implemented to enable regular observing future. describe and demonstrate capability perform timing searching. also measure flux density polarization properties Vela (PSR J0835$-$4510) at mm-wavelengths, providing polarimetric study any ordinary frequencies above 32...
In April 2019, the Event Horizon Telescope (EHT) collaboration revealed first image of candidate super-massive black hole (SMBH) at centre giant elliptical galaxy Messier 87 (M87). This event-horizon-scale shows a ring glowing plasma with dark patch centre, which is interpreted as shadow hole. breakthrough result, represents powerful confirmation Einstein's theory gravity, or general relativity, was made possible by assembling global network radio telescopes operating millimetre wavelengths...
The globular cluster (GC) M15 (NGC 7078) is host to at least eight pulsars and two low mass X-ray binaries (LMXBs) one of which also visible in the radio regime. Here we present results a multi-epoch global very long baseline interferometry (VLBI) campaign aiming i) measuring proper motion known compact sources, ii) finding classifying thus far undetected sources GC, iii) detecting signature putative intermediate black hole (IMBH) proposed reside core M15. We measure sky right ascension...
Global VLBI imaging at millimeter and sub-millimeter wavelengths overcomes the opacity barrier of synchrotron self-absorption in Active Galactic Nuclei (AGN) opens direct view into sub-pc scale regions not accessible before.Since AGN variability is more pronounced short wavelength, mm-VLBI can reveal structural changes very early stages after outbursts.When combined with observations longer global 3 mm 1 adds detailed information on source structure.This helps to determine fundamental...
The Event Horizon Telescope (EHT) observed in 2017 the supermassive black hole at center of Milky Way, Sagittarius A* (Sgr A*), a frequency 228.1 GHz ($\lambda$=1.3 mm). fundamental physics tests that even single pulsar orbiting Sgr would enable motivate searching for pulsars EHT datasets. high observing means - which typically exhibit steep emission spectra are expected to be very faint. However, it also negates pulse scattering, an effect could hinder detections Galactic Center....