Radio 2024

12 Nov 2024, 09:00 → 15 Nov 2024, 14:40 Europe/Berlin

Erlangen Center for Astroparticle Physics

Anna Nelles, Jörn Wilms, Matthias Kadler

Radio astronomy provides an exciting window on the Universe, allowing us to study a vast realm of astronomical objects and processes, ranging from our local environment of cosmic rays entering the Earth's atmosphere, the Sun and space weather, exoplanets, the Galactic Centre and the intrastellar medium, processes around massive black holes and distant radio galaxies, to cosmic structures and epoch or reionisation.

Current new and upgraded telescopes such as MeerKAT and LOFAR, future telescopes such as the Square Kilometre Array, and planned instruments such as DSA-2000 and the ngVLA will allow us to study radio phenomena with greatly improved sensitivity and resolution. 

 

The Radio2024 Symposium will present the latest highlights in radio astronomy and related fields, bringing together radio astronomers from Germany and other countries. The symposium will cover both scientific and technological advances.

 

The symposium is jointly organised by GLOW and VdR e.V. During the symposium, the GLOW Annual Meeting and the VdR Mitgliederversammlung will take place. In addition, working groups such as LOFAR WG and D-MeerKAT WG will meet.

 

The envisaged time line is as follows:

 

  - March 15, first Announcement of the Radio2024 Symposium 

  - June 15, second announcement, registration opens 

  - September 30,  abstract submission deadline 

  - October 15, program release, registration deadline 

 

The Radio2024 Symposium, GLOW Annual Assembly, and VdR Mitgliederversammlung will take place at the Erlangen Centre for Astroparticle Physics of the Friedrich-Alexander-Universität Erlangen-Nürnberg.

The following speakers have been invited:

- Jessica Agarwal (solar system astronomy)
- Anne Baczko (AGN)
- Eleonora Bianchi (Astrochemistry)
- Michiel van Haarlem (LOFAR2.0)
- Katie Mulrey (Cosmic Rays)
- Wolfgang Nagel (SKA SRCNet)
- Amelie Saintonge (Star formation and galaxy evolution)
- Kevin Schmitz (Machine Learning)
- Jonah Wagenveld (Cosmic Dipole)

Tuesday 12 November

11:00 Registration Open

12:45 Lunch

1 Opening

2024_Welcome_Radio2024.pdf

2 Uncovering the origin of the cosmic radio dipole

The cosmic radio dipole is an anisotropy in the number counts of radio sources, analogous to the dipole seen in the cosmic microwave background (CMB). Measurements of the radio dipole with large radio surveys have shown that though the radio dipole is aligned in direction with the CMB dipole, the amplitudes are in tension. These observations present an intriguing puzzle as to the cause of this discrepancy, with a true anisotropy having large repercussions for cosmology as a whole. I discuss recent measurements of the dipole, and what these measurements might tell us about the dipole. I will also discuss the technique of combining different catalogues for dipole measurements, which can aid in breaking degeneracies which are present for single catalogues. I will discuss the combination of catalogues at different frequencies, survey depths, and sky coverages, and how these measurements can help uncover the origin of the anomalous dipole excess.

Speaker: Jonah Wagenveld (Max Planck institute for Radio Astronomy)

Radio2024 talk.pdf

3 Imaging the Spatial Evolution of Cosmic Ray Air Showers with Radio Measurements

Extensive air showers are generated from the interaction of cosmic rays in the Earth's atmosphere and produce radio emission throughout their evolution, which can readily be measured with radio antennas. Reconstructing the full air shower is crucial to understanding the mass composition of cosmic rays, which provides valuable insight on their possible source of origin. While this can be achieved with dense radio detector arrays such as the LOFAR telescope or the future SKA-low array, current reconstruction frameworks can only reconstruct shower parameters that provide limited information on the mass composition and rely heavily on computationally expensive simulations. In this work, we develop an imaging algorithm to reconstruct the 1-D spatial evolution of air showers using measurements from radio detector arrays. We utilise prior knowledge about the physical process of the radio emission to generate a fast-forward model that produces electric field traces at each radio antenna. The reconstruction is performed using Information Field Theory, a state-of-the-art reconstruction framework based on Bayesian inference. We apply our approach with realistic simulated datasets based on the SKA detector layout and analyse the reconstruction efficiency to standard shower parameters to highlight the performance of our model. We plan to extend the framework to reconstruct the full 3-D air shower profile.

Speaker: Keito Watanabe (Institute for Astroparticle Physics, Karlsruhe Institute of Technology)

WatanabeKeito_Radio2024.pdf

4 The APEX view of the outer Galaxy: structure, star formation, and chemistry

Star formation is ubiquitous in the Galaxy, but the physical and chemical conditions in star-forming sites might differ as a function of galactocentric radius. Due to the negative metallicity gradient, the efficiency of gas cooling and dust shielding decreases in more distant regions. A lower interstellar radiation field and a decrease in cosmic-ray fluxes lead to a decrease in gas heating and ultimately cause lower gas and dust temperatures in the outer Galaxy. The balance between these processes sets the physical conditions of the gas and dust and likely affects star-formation rates and efficiencies. In this talk, we will present the first research highlights of the recently completed APEX legacy survey “Outer Galaxy High Resolution Survey” (OGHReS), which covers 100 deg^2 in the 3rd Galactic quadrant in the 2-1 transition of CO and its rare isotopologues. We will discuss important characteristics of the structure of the outer Galaxy, highlighting the differences with the inner Galaxy. We observed that large-scale filaments in the outer Galaxy are fundamentally quiescent objects, with a mass one order of magnitude lower compared to similar size filaments in the inner Galaxy. Additionally, outer galaxy filaments are found exclusively in inter-arm regions, which might point towards a different formation mechanism with respect to the inner Galaxy. The most prominent filament in the outer Galaxy, Falcor, is the only exception, being a site of efficient star formation and a host of the hot core candidate. Finally, we will present preliminary results of the follow-up studies of selected star-forming clumps in additional molecular and atomic lines, and discuss their gradients across the Milky Way. We will initiate the discussion to what extent the outer Galaxy can act as a laboratory of star formation in a low-metallicity environment, and propose the next steps necessary to interpret star formation in diverse ecosystems.

Speaker: Agata Karska (Max Planck Institute for Radio Astronomy)

5 MeerKLASS: A Large-Area L-Band Survey with MeerKAT – Imaging, Source Catalog, and Spectral Analysis

MeerKAT Large Area Synoptic Survey (MeerKLASS) has observed 236 square degrees of sky at the L band (900-1670 MHz) at declinations < -25 degrees. We present radio continuum images and a catalog of radio sources detected at a signal-to-noise ratio (S/N) > 5 across multiple sub-bands. The data used for this study were collected using the “on-the-fly” interferometric imaging scanning mode, where the MeerKAT array moves back and forth around a fixed point while saving observations every 2 seconds. This method allows for efficient mapping of large sky areas over a few hours, with the observation point gradually shifting as the Earth rotates. The resulting catalog has a median spatial resolution of 10 arcsec. The flux density scale ratio and astrometric accuracy, derived from comparison with previous catalogs, exhibit a scatter within 10% and 1 arcsec, respectively. We also present the spectral indices of the detected sources, providing insights into the source populations and their distribution.

Speaker: Dr Sarvesh Mangla (University Observatory, Faculty of Physics, Ludwig-Maximilians-Universitat, Munich, Germany)

6 Status of the DSA-2000 Deep Synoptic Array

The DSA-2000 will be a world-leading radio survey telescope and multi-messenger discovery engine. The array will consist of 2000 × 5m dishes instantaneously covering the 0.7 - 2 GHz frequency range, spanning an area of 19 km × 15 km in Nevada. In an initial five-year survey, the DSA-2000 will image ~30,000 deg2repeatedly over sixteen epochs, producing a combined full-Stokes sky map with 500 nJy/beam rms noise and 3.3 arcsecond spatial resolution. Fundamental questions surrounding the baryon cycle in galaxies, the formation of stars over cosmic time, and the influence of active SMBHs on galaxies, will be addressed by detecting over a billion star-forming galaxies and active SMBHs, and by observing the neutral-hydrogen kinematics and contents of several million galaxies. The array will revolutionize the field of radio transients, detecting >10,000 FRBs and >1 million slow transients, with sub-arcsecond localization for host galaxy identification. The DSA-2000 will be a leading instrument for the discovery and characterization of the electromagnetic counterparts to neutron-star mergers found by ground-based GW detectors. The DSA-2000 is enabled by two breakthrough technologies, i) a low-cost antenna with an ambient temperature receiver and ii) a new generation of digital back-end known as a radio camera, that outputs image data in real time. I will present the current status of the project and the timeline for construction.

Speaker: Fabian Walter

16:10 Coffee Break

7 MuSES: Multi-messenger Studies of Extragalactic Super-colliders

I present the ERC project MuSES, which will study the physical processes near supermassive black holes that are responsible for launching and propagating relativistic jets in active galactic nuclei (AGN). Project objectives include (i) observational studies of AGN jet geometry, collimation and acceleration; (ii) probing the physical mechanism of neutrino production on the basis of multi-messenger blazar data. The prime goal is to use VLBI observations together with other electromagnetic and neutrino data to understand particle acceleration and neutrino production in active galaxies.

Speaker: Yuri Kovalev (MPIfR-Bonn)

8 Investigating the filamentary emission of radio phoenices

Diffuse radio emission has been observed in plenty of galaxy clusters and classified in radio halos, relics or radio phoenices depending on its morphological and spectral properties. A category that is still less widely studied is that of radio phoenices.
These sources are typically characterised by an irregular and filamentary morphology with an ultra-steep radio spectrum ($\alpha\ge1.5-2$). They are thought to trace fossil lobes of radio galaxies that have been re-energised by adiabatic compression after the passage of a shock wave. However, their precise origin and connection to shocks is still uncertain.
To investigate in more details the radio morphology of these sources we have decided to exploit the very high resolution and sensitivity of LOFAR VLBI observations at 144 MHz.

In this talk, I will present the LOFAR high resolution images of the clusters A1914 and A566. At sub-arcsecond resolution the emission of the radio phoenix in the cluster A1914 is highly filamentary: it presents two bright filamentary structures with many parallel filaments connecting them, while other filaments elongates in different directions in the ICM. The radio phoenix in the cluster A566 also presents filamentary emission resembling the ``mushroom-shape'' structure observed in the galaxy group Nest200047 (Brienza et al. 2021). The flat surface brightness profiles of the filaments suggest they are generated by compression of magnetic field lines. However, it is still unclear whether these filaments reflect the internal magnetic field structure of the remnant radio lobes or magnetic fields in the intracluster medium. Inquiring the origin of these filaments could therefore help us to make a step forward on the comprehension of radio phoenices formation.

Speaker: Nadia Biava (Thüringer Landessternwarte)

9 Analysing the effect of focal-line expansion in the Canadian Hydrogen Intensity Mapping Experiment

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is a cylinder radio telescope that is designed to map the redshifted 21 cm neutral hydrogen signal to constrain the expansion history of the Universe. The measurement is challenging due to bright astrophysical foregrounds, radio frequency interference (RFI) and a complex instrument response function. In this presentation, we focus on analysing subtle instrumental effects of focal-line expansion in CHIME.
CHIME consists of four large cylindrical reflectors. Each reflector collects radio waves and focuses them onto antennas along the steel focal line. The instrument temperature varies by up to 20 degrees daily and 60 degrees seasonally. As a result, the distances between antennas vary slightly with the time-dependent ambient temperature. This slight displacement subtly affects the phase of a source at a given sky position as a function of time (i.e., hour angle), which, in principle, can be observed in high-resolution sky images. Assuming that the focal-line expansion is small compared to other effects (e.g. astrophysical foregrounds or crosstalk), we use a 96-day visibility stack as a regression template to estimate the daily effect of focal line expansion. We present our first results on estimating the focal-line expansion in visibility and image domains. We aim to understand the properties of focal-line expansion, model it and eventually mitigate it.

Speaker: Hyoyin Gan (Leibniz-Institut für Astrophysik Potsdam)

Radio2024_H.Gan.pdf

10 Probing jet formation and acceleration at event horizon scales

Relativistic jets are among the most fascinating objects in the Universe, being launched in the direct vicinity of black holes and accelerating particles to the highest energies. This makes them unique laboratories to study fundamental physics under extreme conditions. Despite significant theoretical and observational efforts in the last decades, the physical processes behind their formation and acceleration are not yet fully understood. To shed light on the physics behind these mechanisms, we perform 3D jet launching and acceleration simulations and compute their radiative signatures throughout the electromagnetic spectrum. Through the production of synthetic observations, we show that the ngVLA and its improved sensitivity and high-frequency coverage will be able to not only image, but also capture the variability of the jet launching zone with great detail. This will prove crucial to our ability to discern between different models of jet formation and particle acceleration.

Speaker: Ainara Saiz Pérez (Julius-Maximilians-Universität Würzburg)

radio2024.pdf

11 A 20-kpc radio superbubble in the star-forming galaxy NGC 4217

Galactic winds are essential in the baryonic cycle of galaxies with cosmic rays and magnetic fields possibly playing an important role. Their influence, however, is yet poorly constrained by observations. In this talk, I will present recent results obtained from radio continuum polarimetry observations of the nearby edge-on galaxy NGC 4217, observing both with the Jansky Very Large Array and the LOw Frequency ARray. We discover a new 20-kpc radio superbubble with limb-brightening and with its base aligned with the X-shaped magnetic fields in the halo of this galaxy. We model the radio halo with cosmic-ray electron transport and find advection speeds between 300 km/s near the disc and 600 km/s in the halo. The energy injected by supernovae is enough to inflate the bubble, although the influence of an active galactic nucleus cannot be ruled out either. Such bubbles may be ubiquitous in star-forming galaxies showing the presence of bipolar outflows as a result of feedback.

Speaker: Dr Volker Heesen

18:00 Welcome Reception

In the Foyer of the ECAP Laboratory

Wednesday 13 November

08:25 Registration open

12 Upgrading the Low Frequency Array: LOFAR 2.0

Upgrading the Low Frequency Array: LOFAR 2.0

Speaker: Michiel van Haarlem

13 The Polar simulations for studying the 21-cm signal

I will show the Polar simulation suite developed by the LOFAR Epoch of Reionisation Key Science Project team. The suite consists of simulations with different cosmological and astrophysical parameters that are tuned to match the UV luminosity function of galaxies at redshifts 9 and 10. I showcase that even with an eventual detection of the 21-cm signal at these redshifts, the parameter space that we need to explore for viable models of the Universe needs to be significantly expanded. Additionally, I highlight the necessity to boost resolutions of simulations beyond what is traditionally feasible as we currently don't include dwarf galaxies at high redshifts. This severely limits the utility of simulations at high redshifts. To tackle this, I will talk about resolution-boosting algorithms that are temporally consistent and the plans for developing them further. These simulations shall be used for inference modelling by LOFAR, and eventually by SKA too. Additionally, the LOFAR team uses it for building templates for the 21-cm signal power spectrum using Machine Learning and then using the template to look for the signal in observational data.

Speaker: Anshuman Acharya (Max Planck Institute for Astrophysics)

Radio2024_Polar_AnshumanA.pdf

14 Miniaturized Chip-based Receiver Components for the ngVLA and Beyond

The ngVLA is designed to play a critical role in achieving key scientific goals related to the evolution of galaxies, the formation of supermassive black holes, and more. To do so, it aims to achieve ten times the sensitivity of the Jansky VLA and ALMA. Thereby, placing high demands on the used receivers. To meet these requirements, custom solutions based on the combination and interconnection of individual, bulky components are traditionally pursued. Instead, we investigate the possibility of replacing the ngVLA’s band 6 warm cartridge assembly concept with a single chip in SiGe. The results demonstrate the ability to meet the phase noise requirements for the ngVLA local oscillator. In addition, the dramatic reduction in complexity may open the door to new concepts and ideas for the radio telescopes of the future.

Speaker: Tobias Thiemo Braun (Ruhr University Bochum)

MiniaturizedChip-basedReceiverComponents.pptx

15 Reconstructing cosmic ray induced air showers for LOFAR

The Low Frequency Array (LOFAR) has been measuring cosmic rays for over a decade. Its dense core of antenna fields makes it an ideal tool for studying the radio emission of extensive air showers, sensitive to energies between 10^16 eV and 10^18.5 eV. Each air shower is recorded using a small particle detector array and hundreds of antennas. The current state-of-the-art method for reconstructing properties such as the shower maximum (Xmax), known as the LOFAR method, relies on various simulations and achieves the highest precision to date. However, it does not fully utilize all available information from the data and is computationally intensive.
We present the current state of development of a new, holistic approach that incorporates all available information, and combines both particle detector and antenna data. This method is based on Bayesian inference and offers a physics-informed, simulation-independent reconstruction, while also providing uncertainties for all reconstructed parameters.

Speaker: Karen Terveer (Friedrich-Alexander-University Erlangen-Nürnberg, Erlangen Centre for Astroparticle Physics)

Radio2024_Terveer.pdf

16 Intercontinental decametric VLBI

Between December 2023 and April 2024 we conducted a VLBI experiment with LOFAR, NenuFAR, KAIRA and several stations of the LWA to try transatlantic interferometry below 100MHz. Targets were Jupiter (at times of expected decametric bursts) and three bright pulsars. First goal is detecting fringes at all, which was not possible in a smaller experiment more than ten years ago. In the case of success, we can study the decametric emission from Jupiter at the finest scales. I will report on the progress, show preliminary results, and explain what can be done in the case of Jupiter, based on earlier European interferometry.

Speaker: Olaf Wucknitz (MPIfR)

wucknitz.pdf

10:25 Coffee Break

17 Small bodies in our solar system

While spacecraft visiting individual bodies in our solar system reveal their targets in unrivaled detail, astronomical observations are irreplaceable for some aspects of solar system exploration. Astronomy gives us access to a large number of objects, enabling population studies and providing a comprehensive view of the solar system's inventory. Also, astronomical observations can be planned and carried out on much shorter timescales than space missions, enabling the discovery and follow-up of unexpected events like collisions, disruptions and temporary visitors, crucial to understanding the on-going evolution of the solar system. Both aspects are particularly relevant for studying the solar system's small body populations, including, but not limited to, comets and asteroids.

This talk provides an overview of the small bodies in our solar system that are thought to have been preserved from the time before planet formation in three dynamical reservoirs: the asteroid belt between Mars and Jupiter, the Transneptunian region beyond Neptune, and the Oort Cloud at the very limit of the sun's gravitational influence. The talk will explore some aspects of small body research where radio astronomy plays a crucial role or may become relevant in the future with increasing telescope sensitivity and resolution.

Speaker: Jessica Agarwal

agarwal_sosy_radio_241113.pdf

18 Millimetre-VLBI with Frequency Phase Transfer

Recent developments of multi-frequency receivers with shared optical paths (SOP) have brought a number of new scientific and technological opportunities to VLBI. With these receivers, the frequency phase transfer (FPT) method can become a backbone of VLBI operations at frequencies above 22 GHz. This opportunity has already been exploited at the Korean VLBI Network (KVN) and is gaining ever more prominent attention in Europe, where up to six telescopes may soon start operating three-band (22/43/86 GHz) SOP receivers, including one for the 100-m radio telescope in Effelsberg, which is funded in the framework of the M2FINDERS project and with large facility project funding from the Max Planck Society.
Observations with this new network of telescopes would bring order of magnitude improvements in sensitivity and dynamic range of mm-VLBI imaging and deliver astrometric measurements with an accuracy of a few microarcseconds. The resulting exceptional discovery potential would strongly impact a number of scientific fields ranging from fundamental cosmology and black hole physics to stellar astrophysics and studies of transient phenomena.

In this talk, we will review the recent developments in frequency-domain atmospheric phase calibrations and the development of new triple-band receivers, and we will present highlights from recent test observations with a prototype array consisting of radio telescopes in East Asia and Spain.

Speaker: Guang-Yao Zhao (Max Planck Institute for Radio Astronomy)

GyZhao_Radio2024.pdf

19 The current and future state of the german LTA at FZJ

FZ Jülich hosts one of three LTA sites which provide a long term archive that stores LOFAR data. I will present the current state of the archive, statistics on the archive usage, and future plans for it.

Speaker: Arpad Miskolczi

LTA_Status_Update_2024.pdf

20 Networkdesign for LOFAR 2.0

The quite technical talk will give an overview of the actual network-setup for the operation of the German LOFAR antennafields in combination with correlators at Dwingeloo, Juelich and Bonn as well as for the operation of the LTA at Juelich. Information about operational issues as well as statistics covering the last 12 months of LOFAR observations and data-transfers will be given. In the 2nd part the talk will focus on the actual planning and design activities together with Astron, Surf and the DFN to cope with the upcoming demands of LOFAR 2.0 and even empower GLOW by a capable new high-bandwidth network to address new science-projects between the involved sites.

Speaker: Olaf Mextorf (Forschungszentrum Jülich)

Radio2024_lofar_networkstatus_olaf_mextorf_241113.pdf

21 Improving the accuracy of geodesy and astrometry with Astrogeodesy by VLBI Global Observing System

Active Galactic Nuclei (AGNs) are used by the space geodetic technique of very long baseline interferometry (VLBI) as references on the sky to precisely measure the shape and orientation of the Earth due to their extreme distances. Their positions form the celestial reference frame (CRF) that plays an important role in both astronomy and geodesy. The geodetic products and the CRF are determined by simultaneous VLBI observations at four frequency bands, centered at 3.3, 5.5, 6.6, and 10.5\,GHz. These quad-band observations are carried out by the new generation geodetic VLBI system, named VLBI Global Observing System. The AGNs in VGOS observations are all resolved at milli-arcsecond scales to have angular structure. Based on the different impacts, source structure can be divided into two parts: visible structure (large scales) and invisible structure (in beam sizes). The former one causes closure delays enlarging post-fit delay residuals in geodetic solutions whereas the latter causes source position changes. The study aims to model this time- and frequency-dependent source structure and to have the AGNs as point-like anchors on the sky for improving the accuracy of geodesy and astrometry. This study is funded by an ERC starting grant in 2023, the Astrogeodesy project, and it will also have a profound impact on the future VLBI facilities, such as SKA and ngVLA. I will report on the project and discuss the progress and challenges.

Speaker: Minghui Xu (German Research Center for Geosciences)

Radio_2024_Xu_v2.pdf

12:30 Lunch Break

Breakout Session: LOFAR Stand-Alone & Upgrade (public)

DSA_Session.txt

22 D-LOFAR Network upgrade

23 LOFAR2.0 upgrade

24 Stand-alone operations, discussion

25 Galactic Astrophysics with Imaging Atmospheric Cherenkov Telescopes: Gamma-ray astronomy, intensity interferometry & other radio synergies

This talk will provide a brief overview of several topics of synergetic interest, bringing together opposite ends of the electromagnetic spectrum. Galactic gamma-ray sources producing photons at ~TeV energies include supernova remnants, pulsars and their nebulae, stellar clusters and binary systems. Imaging Atmospheric Cherenkov Telescopes also have other commonalities with radio facilities, such as interferometric measurements, detection of extensive air showers and combating satellite interference. New gamma-ray and radio facilities will be coming online in the near future, lending themselves to further MWL collaboration.

Speaker: Alison Mitchell

Radio2024_IACT_gamma.pdf

26 Millimetre-VLBI in the Multi-Messenger Era

The highest resolution in radio interferometry is achieved by using very long baseline interferometry at millimetre wavelengths (mm-VLBI) or by using antennas in space. The Event Horizon Telescope (EHT) and the Global mm-VLBI Array (GMVA) have made significant advances in our understanding of supermassive black holes. German radio astronomy has played a key role in these endeavours. For instance, the 100-metre Effelsberg radio telescope, operated by the Max Planck Institute for Radio Astronomy, is a key component of the GMVA. All GMVA data and 50% of the EHT data are correlated in Bonn. Apart from that, advances in digital back-ends, calibration procedures and imaging methods, coupled with the advent of multi-band options, are significantly expanding the capabilities of VLBI at the highest resolution. The introduction of frequency phase transfer will significantly improve the sensitivity and positional accuracy of radio interferometry at frequencies above 22 GHz. This technology, first proposed at the MPI for Radio Astronomy, will allow astronomers to study the most compact and powerful objects in the Universe in unprecedented detail. Observations of very high-energy gamma-ray and neutrino interactions will complement radio data in the coming era of multimessenger astronomy. The German community is actively involved in international collaborations to study these phenomena, using the capabilities of telescopes such as the 100-metre Effelsberg radio telescope, and the IceCube and Km3Net neutrino observatories.

Speaker: Eduardo Ros (MPI für Radioastronomie)

RadioDays_Ros_20241113.pdf

27 Diffuse emission in the galaxy cluster RXJ 1347.5-1145

Diffuse radio sources, known as mini-halos and halos, are sometimes found at the centres of galaxy clusters, though both are rarely observed together. The origin of these sources remains unclear. In this talk I will present our investigation on the massive galaxy cluster RXJ 1347.5-1145, known to host a central mini-halo and possible extended emission. Using deep multi-frequency observations from MeerKAT and uGMRT, we confirm the presence of the central mini-halo, but discover an additional diffuse source extending up to 840 kpc that is classified as a giant radio halo. We examine the correlation between radio and X-ray brightness to understand the physical processes that govern the acceleration of radio-emitting relativistic electrons in these diffuse sources.

Speaker: Duy Hoang (TLS)

DHoang_RXJ1347_Radio2024.pdf

28 Probing the polarized innermost structure of the relativistic jet of 4C +01.28

The formation of relativistic jets from active galactic nuclei remains a subject of intense debate. Despite significant advances in understanding the underlying mechanisms, numerous questions remain. To address them, high-angular-resolution observations performed with the very long baseline interferometry (VLBI) technique are needed. In this context, we present preliminary results on 4C +01.28 (B1055+018), a blazar that shows a relevant correlation between emission at radio and gamma-ray wavelengths, and whose previous VLBI observations highlight the presence of a remarkable jet stratification. The latter consists of an inner spine with a transverse magnetic field and a distinct boundary layer - the sheath - with a longitudinal magnetic field. Exploring the properties of this unique jet stratification, alongside the jet magnetization on sub-parsec and parsec scales, is key to unlocking the secrets of the jet launching mechanisms in such a source. Thanks to the synergy between VLBI maps at various frequencies, including new 86 GHz GMVA and 230 GHz EHT observations, and relativistic MHD numerical simulations, 4C +01.28 offers an excellent opportunity for testing state-of-the-art models of jet formation.

Speaker: Luca Ricci (JMU Würzburg)

1055 presentation.pdf

29 Observational constraints on dark matter from lensing

The Cold Dark Matter model for structure formation is currently the most successful at reproducing many observations, but it remains largely untested in the non-linear sub-galactic regime. A clear prediction of this model is that a significant number of low-mass haloes should populate any galaxy and its line of sight. As most of these objects are expected to be completely dark, strong gravitational lensing provides a unique channel to detect them and determine the properties of dark matter by constraining the halo-mass function at the low-mass end.

In this talk, I will present the latest observational constraints on dark matter from lensing and discuss the challenges in deriving robust constraints. I will particularly focus on the main sources of systematic errors from both the observational and theoretical sides of the problem. I will then focus on the expected role of existing and upcoming observing facilities such as LOFAR, the SKA and the ngVLA in this field.

Speaker: Dr Simona Vegetti

15:55 Coffee Break

VdR Mitgliederversammlung: VdR Mitgliederversammlung (members and invited guests only)

Thursday 14 November

08:30 Registration open

GLOW: D-LOFAR-ERIC Lenkungsausschuss (non-public)

30 Report from LOFAR ERIC Council and Committees

31 Budget plans 2025+

32 German participation in DANTE

GLOW: GLOW Council (non-public)

33 Report from GLOW EC

34 Report from Working Groups

35 Representative for ngVLA International Development Consortium

10:30 Coffee

36 DZA and IT services: About the next steps

To be added

Speaker: Wolfgang Nagel

37 4D air shower reconstruction with SKA

Extensive air showers (EAS), created from interactions of highly energetic cosmic particles with the atmosphere, produce radio emission via the geomagnetic and Askaryan effect. These radio signals provide valuable information about the properties of the primary particle that started the air shower. Dense radio detector arrays such as LOFAR and the future SKA-low allow high-precision reconstruction of shower parameters such as the depth of the shower maximum. However, current reconstruction methods rely heavily on simulations and hadronic interaction models. Thus, a model-agnostic reconstruction approach is of great interest. Furthermore, current state-of-the-art reconstruction algorithms are able to reconstruct air showers in at most three dimensions. However, the time evolution of the air shower may also provide crucial information. The goal of this project is therefore to develop a model-agnostic algorithm to reconstruct air showers in 4D (space + time). Using this method, we expect to reconstruct shower parameters with unprecedented precision and possibly alter our understanding of air shower development. In order to tackle this endeavor, a vast abundance of high-precision data is required, which the future SKA-low array with its dense core of roughly 60000 antennas is expected to deliver. The reconstruction algorithm itself will employ Information Field Theory (IFT), a novel reconstruction framework based on Bayesian inference.

Speaker: Mr Philipp Laub (ECAP, FAU Erlangen-Nürnberg)

Radio2024PhilippLaub.pdf

38 Improved Coverage for VLBI networks through the SKAMPI telescope

The SKA-MPIfR telescope (SKAMPI) is a 15 m prototype dish of the Square Kilometer Array (SKA)-MID located in the Karoo Desert, South Africa. The telescope is funded and operated by the MPIfR, including the implementation of a novel VLBI backend. As one of the potentially longest baselines for both southern and northern VLBI observations, the SKAMPI telescope will play a crucial role in the future of radio astronomy, providing excellent spatial resolution and schedule flexibility. Furthermore, the addition of the SKAMPI telescope to the VLBI array is an important step towards accessing faint source populations in the era of SKA VLBI. I will show the simulated observations after adding the SKAMPI telescope to different existing VLBI networks and the expected sensitivity. I will also discuss recent developments regarding the VLBI observing mode of the SKAMPI telescope, including fringe detections and successful implementation in S-band observations with the Australian Long Baseline Array in an experiment within the scope of the TANAMI program. This program is a multi-wavelength observing program aimed at monitoring relativistic jets from Active Galactic Nuclei in the southern sky.

Speaker: Jompoj Wongphechauxsorn (JMU)

Updates on VLBI with SKAMPI-main.pdf

39 SKAMPI: The SKA-mid MPIfR Demonstrator Dish

The SKAMPI dish has been build at the SKA site as a prototype and technology demonstrator for the SKA-mid array. It is a fully operational telescope by its own, build to SKA-mid specifications. It is equipped with two cryogenically cooled receivers, one operating in the S-Band, and one in the Ku-Band, respectively. While primarily intended for technology commissioning, SKAMPI also supports independent science programs. For this purpose, it is connected to a multi-science backend running on COTS computing hardware and equipped with a novel telescope control system for semi-automatic operation with a minimum of human interaction. Here, we give an overview on the technology and scientific capabilities of SKAMPI.

Speaker: Tobias Winchen (Max Planck Institute for Radio Astronomy)

241112_SKAMPI_Winchen.pdf

40 Evolution of fundamental and harmonic sources in LOFAR type III radio burst images

We present LOFAR observations of an M class flare, that was accompanied by intense type III radio bursts. Some isolated burst have a fundamental-harmonic structure, but for most bursts this is not visible due to a rapid succession of bursts. Spectroscopic imaging with LOFAR shows type III bursts as a compact source for a given observing frequency. The intensity varies with burst evolution, but the location remains largely fixed since it is determined by where in the solar corona the local plasma frequency matches the observing frequency. But from time to time the source changes its position, with dual structures during the transition. We interpret this as signatures of fundamental and harmonic emission, the latter originating from a higher location in the corona so that the local plasma frequency there matches half of the observing frequency. Fundamental-harmonic pairs, e.g. fundamental emission at 35 MHz and harmonic emission at 70 MHz, should originate from the same plasma volume. Differences in their positions and intensity variations are expected since radio wave transport effects in the corona, like scattering and refraction, should affect fundamental more than harmonic emission. Analyzing such differences therefore allows for quantifying these effects.

Speaker: Christian Vocks (Leibniz-Institut für Astrophysik Potsdam (AIP))

12:20 Lunch Break

41 Satellite Constellations & Astronomy: What is the problem? What are we doing about it?

This is the regular ECAP Seminar, given this week by Olivier Hainaut.

See here for details: https://ecap.nat.fau.de/index.php/event/ecap-seminar-2024-11-14-olivier-hainaut/

Breakout Session: German DSA-2000 prototype mini-array (public)

DSA_Session.txt

42 Update of OVRO test array

43 Update on site survey in Saxony

44 Path towards construction of German test array

45 Test to be undertaken in 2025

46 Potential science applications

47 Astrochemistry at radio wavelengths: perspectives for the SKAO

The formation of a planetary system similar to our own involves several physical processes, beginning with the collapse of a cold (≤ 10 K) and dense (≥ 10⁵ cm⁻³) prestellar core into a protostar, a protoplanetary disk, and eventually a planetary system. These stages are also accompanied by the evolution of the chemical composition, and astrochemistry serves as a powerful diagnostic tool to trace both past and present physical conditions.
The vast majority of observations that revealed the chemical composition of solar-type protostars have been made using millimeter-wavelength telescopes. In this spectral range, several relatively light molecules, like the interstellar complex organic molecules (iCOMs) or the small carbon chains (e.g., HC3N, c-C3H2) have their peak of emission. Radio wavelengths, on the other hand, allow us to observe more complex carbon species (e.g., C4H, C6H, HC7N, HC9N, C3S), which may play a crucial role in the transfer of organic material from the pre- and protostellar phases to newly formed planetary system objects like asteroids and comets. I will present preliminary results obtained with single-dish telescopes (GBT and Yebes) and discuss future perspectives on next-generation radio interferometers to map the spatial distribution of complex carbon species. In this context, I will also present a specific SKA1-MID Scientific Use Case (Band 5), developed as part of the "Cradle of Life" science working group activities.

Speaker: Eleonora Bianchi

Bianchi-Erlangen-SKA.pdf

48 Summary statistics from LoTSS wide and deep fields

Speaker: Dominik Schwarz

LoTSSatRadio2024.pdf

49 A VLBI view of strong gravitational lenses

Galaxy-scale strong lens systems are powerful laboratories for studying the nature of dark matter, galaxy formation history, magnetic fields, and cosmology. Very long baseline radio interferometry (VLBI) is the current gold standard for observing individual strong lens systems, with the ability to probe milli-arcsecond scales in both the lens plane and source plane. However, only a handful of such observations currently exist, and their analysis was (until recently) computationally prohibitive. The next few years will see the discovery of over $10^5$ strong lens systems thanks to the Euclid space telescope, the Vera C. Rubin observatory, and the Square Kilometre Array (SKA). Follow-up of newly discovered lens systems with high-resolution radio imaging will provide a unique opportunity to make major contributions to the strong lensing field within the next five years, and to develop analysis tools capable of handling a further flood of high-resolution data from next-generation VLBI observatories like SKA-VLBI and ngVLA within the decade. In this talk, I will review my work on modeling strong lens systems observed at milli-arcsecond resolution with VLBI, and my development of the computational techniques needed to do so. I will then discuss future research opportunities using VLBI follow-up of Euclid and SKA lenses, as well as my long-term vision for developing the analysis tools and expertise needed to produce the best possible strong lensing science in an era of abundant high-quality VLBI lens observations.

Speaker: Devon Powell (Max Planck Institute for Astrophysics)

talk_radio2024_powell.pdf

50 The MPIfR-MeerKAT Galactic Plane Survey-- current status and future

The MPIfR-MeerKAT Galactic Plane Survey (MMGPS) is an unique 3000-hr
programme with the MeerKAT telescope that effectively utilizes the backend
capability of the system to simultaneously perform time-domain searches, e.g.,
of pulsars, and provide high quality, full Stokes, continuum data. This ongoing
survey will cover the inner Galactic plane between the longitude range 260 to
15 deg, through the Galactic center, using three frequency bands over the
ultra-broad frequency range from 540 to 2850 MHz. This places MMGPS uniquely in
the current landscape of pre-SKA surveys in general, and especially in
exploring the different phases of the Galactic ISM with unprecedented detail.
In this talk I will present the current status of the survey, and the
preliminary results. I will highlight the plethora of science cases MMGPS will
enable to glean deeper insights into the properties of the turbulent Galactic
magneto-ionic medium on scales ranging from 0.2 to 100s of parsecs.

Speaker: Aritra Basu (Thüringer Landessternwarte, Tautenburg)

AritraBasu_glow2024.pdf

Poster Flash Talks: Posters

51 Probes of Jet Physics in Neutrino-Candidate Blazars with cm- and mm-VLBI

In recent years, evidence has accumulated that some high-energy cosmic neutrinos may be associated with blazars. The strongest evidence for an individual association was found in the case of the blazar TXS 0506+056 which exhibited a major multi-wavelength flare coinciding with an IceCube neutrino event in 2017. A major open question is the production site of neutrinos in blazar jets, especially the possible seed photon fields needed for the hadronic processes are not well constrained. VLBI observations can constrain the jet geometry, magnetic field and Doppler factor in AGN jets to gain insight into the possible neutrino production regions. We have performed a multi-frequency VLBI study from 15 GHz up to 86 GHz on TXS 0506+056 and two additional neutrino-candidate blazars (PKS 0215+015, PKS1502+106) to study the radio structure of neutrino-candidate blazars. We have obtained target of opportunity observations with the VLBA for all three sources within ~1 month from the associated neutrino event and are performing multi-epoch studies on the jet kinematics at 15 GHz as part of the MOJAVE program. Here, we present first results on the contemporary parsec-scale jet morphology of all three sources in total intensity and polarization to constrain possible physical processes leading to neutrino emission in blazars.

Speaker: Florian Eppel (JMU Würzburg)

FlashTalk_Erlangen_Eppel.pdf

52 HST-1 knot in the M87 jet: Results from quad-frequency observations with milliarcsecond resolution

HST-1 is a knot in the conical kiloparsec-scale M87 jet, observed for the first time by the Hubble Space Telescope. In the images, it is the first resolved feature near the jet's "core" on the arcsecond scale. HST-1 showed superluminal speeds up to 6c and significant flaring activity in optical and across all bands from radio to X-rays and even gamma-rays. From the perspective of VLBI, the M87 jet exhibits a parabolic geometry, which indicates the significant role of HST-1 in the jet's collimation and evolution. However, due to its distance from the jet base and, consequently, the smearing effects limiting the field of view for VLBI, HST-1 remains a challenging feature to study in detail, resulting in a lack of high-resolution VLBI data and spectral information.

In this talk, I will present our attempt to mitigate the problems introduced above using quad-frequency observations of HST-1 at 2, 5, 8, and 15 GHz with the VLBA and the EVN arrays. By utilizing these four frequencies, we have constructed a spectral index map of the knot and, notably, a turnover frequency map for the first time.

The spectral index maps reveal a uniform structure with a steep spectrum slope of approximately -0.7, suggesting that HST-1 is likely part of an optically thin jet rather than a standing shock. The turnover frequency maps have also allowed us to estimate the magnetic field strength of the milliGauss order.

Speaker: Aleksei Nikonov (Max-Planck-Institut für Radioastronomie)

Nikonov_Flash_poster.pdf

53 Black Hole Explorer - the next generation millimeter Space VLBI mission

We present an overview of a proposal for the next generation Space VLBI mission Black Hole Explorer (BHEX). Its main scientific goal is to detect the photon ring and directly measure the mass and spin of supermassive black holes in centers of M87 and the Milky Way. Other science cases include demographics on a dozen of additional near-horizon sources as well as studying accretion, formation, and collimation of jets in active galaxies. In order to do it, a 3.5-m radio dish will be launched into space to an orbit longer than 3 Earth diameters and will observe together with the most sensitive ground millimeter telescopes. BHEX will be equipped with two cooled receivers covering a frequency range from 80-106 and 240-320 GHz, which can observe simultaneously. A laser-com link will deliver a real-time data stream of 100 Gbps to the ground. BHEX is planned to launch in 2031 and expects to actively observe together with the most sensitive ground telescopes, including ALMA, NOEMA, Effelsberg, IRAM 30-m, APEX.

Speaker: Prof. Yuri Kovalev (MPIfR)

Kovalev_BHEX_Radio2024.pdf

54 Using Self-Organising Maps to classify complex radio morphologies in current and next-generation radio surveys

Radio galaxies often exhibit complex morphologies that are challenging to identify using traditional source finders, necessitating visual inspection of radio maps. The large data volumes of the current and next generation of radio continuum surveys makes such visual inspection impractical. The objective of my research is to develop a more efficient method to identify and classify complex radio sources, including potentially rare objects such as Odd Radio Circles (ORCs). I am utilising an unsupervised machine learning technique, specifically a Self-Organising Map (SOM), which has been trained on 251,259 sources from the Rapid ASKAP Continuum Survey (RACS). Morphological labels (compact, extended, double, and triple sources, among others) were assigned to the SOM neurons through visual inspection. These labels were subsequently transferred to the sources in the catalogue via their best-matching neurons. Visual inspection of a sample of our catalogue showed that the reliability of the SOM-derived morphological labels in our catalogue exceeds 90% for approximately 80% of our sources, demonstrating its efficacy in identifying different types of radio sources. Notably, our method identified approximately 84,424 potential double sources with a >90% reliability. The trained SOM can be used to predict whether new radio galaxy images can be classified as complex sources or not. This project has the potential to improve the classification of complex radio sources, including those with rare or unusual morphologies, in future surveys. This talk will delve into detailed results and implications and discuss the potential impact of our approach on large-scale radio surveys.

Speaker: Ms Afrida Alam (University of Hull)

55 A Census of Variable and Transient Radio Sources within Southern-Hemisphere IceCube Neutrino Fields

The origin of high-energy cosmic neutrinos detected by the IceCube observatory is a hotly debated topic in astroparticle physics. There are multiple candidate source classes which can accelerate cosmic particles to the energies required to emit high-energy cosmic neutrinos and which have in common that they lead to variable/transient radio emissions. Recent observational results suggest that high-energy neutrinos may be associated with individual AGN jets. Aside from some promising associations with bright AGN, the bulk of the diffuse IceCube neutrino flux must be emitted from a rather faint and numerous source population. The sub-mJy low-frequency radio sky may harbor these neutrino emitters that have gone unnoticed in previous searches. On July 16th 2024, IceCube reported on two track-like neutrino events in spatial coincidence with each other and with the cascade-like neutrino event IC240714A. We observed the overlap of the 90% uncertainty regions of all three neutrino events with MeerKAT at 815 MHz, to perform a census of variable and transient radio sources that could have produced all three detected neutrinos. Here, we present first results of this MeerKAT census of variable and transient faint radio sources in this IceCube multiplet neutrino field.

Speaker: Florian Rösch (JMU Würzburg, MPIfR)

Flash_Talk_Radio2024_Rösch.pdf

56 Feeding the Giant: The Unified Picture of AGN Life Cycles, Feeding and Feedback in MSH05–22

Giant radio galaxies are a spectacular and gargantuan form of AGN, often living in under-dense environments and hosting jets that have been switched on for extended periods. Many seem ancient, with estimated ages over 100 Myr, and/or exhibit complex characteristics, suggesting multiple epochs of activity over their lifetime. In particular, studying giant radio galaxies with signs of young, restarted jets provides a key window into jet triggering and feedback mechanisms.

These jets play a pivotal role in the evolution of both the host galaxy and the ambient medium, as they may trigger and/or inhibit star formation, drive the mixing of gas and dust internally to the galaxy, drive outflows into the ambient medium, and even sufficiently cut off the supply of infalling material that fuels the central engine.

In this talk I will present the results of a multi-wavelength observational campaign studying the nearby giant radio galaxy MSH05–22, which shows highly asymmetric radio lobes. Our campaign covers radio frequencies from 70 MHz to 40 GHz using the Murchison Widefield Array (MWA), the Australian Square Kilometre Array Pathfinder (ASKAP), and the Australia Telescope Compact Array (ATCA) as well as the MeerKAT radio telescope in South Africa, combined with optical integral field unit (IFU) spectroscopic observations.

Put together, our exquisite dataset paints the picture of periodic activity from MSH05-22, from which we study the duty cycle of the AGN, the processes by which the central engine was fed, and the feedback from the AGN into the ambient medium. On the largest scales, the megaparsec-scale lobes are diffuse and steep spectrum with no hotspots, indicating they are no longer powered by fresh activity and have estimated ages well over 100 Myr. On intermediate scales, our radio data show evidence of asymmetric jets on scales up to around 100 kpc with a highly-ordered magnetic field. On small scales, the radio core associated with the central engine shows complex spectral structure suggesting different components tracing historic activity, as well as a high-frequency break indicating that the central engine switched off some 8 Myr ago.

Our IFU and MeerKAT HI observations show evidence of a recent interaction between MSH05-22 and its near neighbours, with neutral inflow of material onto the dominant elliptical galaxy as well as extended HI emission spanning the system. This interaction and inflow triggered an epoch of star formation as recently as 10 Myr ago, as well as likely triggering the most recent episode of AGN activity. Overall MSH05-22 is a highly rich system which provides many insights into the life cycles of these most giant and most ancient of radio galaxies.

Speaker: Chris Riseley (Alma Mater Studiorum - Università di Bologna)

Radio2024_Sparkler_CJRiseley.pdf

57 Exploring the Disk-Jet Connection in Nearby Jetted AGN

Relativistic jets from Active Galactic Nuclei (AGN) are suggested to originate from supermassive black holes at the center of galaxies, surrounded by their accretion disks. The properties of the disks are intrinsically linked to the characteristics of the launched jets, in what is known as disk-jet connection. When considering their magnetization, accretion disks fall into two main categories: the low-magnetized Standard and Normal Evolution (SANE) disks, and the highly- magnetized Magnetically Arrested Disks (MAD). These distinct disk classes result in different magnetic fields within the jets, impacting observational signatures such as their acceleration, collimation, and polarization. These phenomena can be probed by means of cm-/mm-Very Long Baseline Interferometry (VLBI) observations. Through the characterization of the mentioned observational jet properties, we can employ theoretical models to constrain the magnetization of the jets and, correspondingly, their accretion disks. In this talk, our recent results on the disk-jet connection, focusing mainly on the nearby jetted radio galaxy NGC315, will be presented.

Speaker: Luca Ricci (JMU Würzburg)

Poster_slide_Ricci.pdf

58 Spectral Ages of Remnant Radio Galaxies with MIGHTEE and SuperMIGHTEE in XMM-LSS Field

Remnant radio galaxies (RRGs) are characterized with switched off AGN activity resulting relic lobes devoid of any supply of plasma from jets. Despite the cessation of AGN activity, lobes can be detected for a period of time before they fade away due to radiative and dynamical energy losses. The time-scale of the remnant phase and AGN duty cycle are vital to understanding the evolution of radio galaxies. In this work, we present spectral age estimates of RRGs by modeling their radio spectral energy distributions (SEDs) across 144 MHz−1.5 GHz using LOFAR, uGMRT, MeerKAT and JVLA observations. The new radio observations at band-3 and band-4 from uGMRT (superMIGHTEE) and L-band from MeerKAT carried out under the MIGHTEE project allow us to build densely sample SEDs which in turn yields better constraints on the spectral age estimates. In this presentation, I shall highlight the importance of sensitive multi-frequency radio observations to identify new population of RRGs.

Speaker: Sushant Dutta (IDIA, University of Cape Town)

59 Exploring AGN feedback with LOFAR and multi-frequency surveys

Firstly, I will present our work on linking the radio-AGN life-cycle with feedback on the ionized gas. By combining the LOFAR survey LoTSS with other large radio surveys like FIRST and VLASS, we identified a sample of 5,700 radio-AGN at various evolutionary stages and ~150 restarted AGN. We characterized the [OIII] kinematics of the sample and found a significant correlation between the feedback on ionized gas and the evolutionary stages of the radio-AGN. Our findings show that feedback is strongest (~3 times more likely) when the radio-AGN (and the jets) are young, and becomes much gentler at later evolutionary stages. Additionally, using the sample of restarted AGN selected with the high sensitivity of LOFAR, we discovered that the impact on ionized gas is linked only to the most recent phase of jet activity.

Furthermore, I will present results from our study combining LoTSS and MaNGA (optical IFU survey) to investigate the relationship between the spatial extent of disturbed gas and radio luminosity in AGN in the local Universe. While such relationships have been studied for optical luminosity in Seyferts and Quasars, none has been found with radio luminosity. We find that the spatial extent of the most disturbed ionized gas increases with radio luminosity, with the gas being disturbed up to 0.75$\times R_{eff}$ (effective radius) of the galaxy. This indicates that radio-AGN impact is typically strongest in the central region, beyond which different power sources do not significantly disturb the gas.

Through these studies, I aim to demonstrate the immense value of LOFAR surveys and their capability to enhance our understanding of galaxy evolution when combined with surveys at other frequencies.

Speaker: Pranav Kukreti (ARI, Heidelberg University)

16:00 Coffee Break

60 Detecting cosmic particles with radio telescopes

Although cosmic rays were first detected over 100 years ago, we still don’t understand their sources and the physical processes that can create such extreme energies. Particularly interesting is the question of which cosmic-rays originate from our galaxy, and which ones from extragalactic sources. Particles in this so-called “transition region” can tell us about the most extreme astrophysics in our region of the cosmos. Cosmic rays at these energies must be detected indirectly, via the particle cascades called “air showers” that are induced when primary cosmic rays interact in the atmosphere. These air showers emit a sharp pulse of radio light. In the last decade, it has been demonstrated that radio telescopes make excellent instruments with which to detect this emission. In particular, radio measurements of cosmic rays at LOFAR helped bring this technique into maturity. Now, we are embarking on the next generation of radio observations with the SKA telescope. In this talk, I will give an overview of the field, the current status, and discuss prospects for what we will be able to do in the next decade.

Speaker: Katie Mulrey (Radboud University)

Radio2024_cosmicrays_mulrey.pdf

61 The lightest black hole or the heaviest neutron star?

The exceptionally high stellar densities in the cores of globular clusters (GCs) makes them remarkable hosts for an exotic pulsar population. In this talk, I will discuss the results from the searching for and timing of a couple of massive binary pulsars in the dense globular cluster NGC 1851, observed with the MeerKAT as a part of the TRAPUM (TRAnsients and Pulsars with MeerKAT) GC Survey. Both systems consist of millisecond pulsars in eccentric orbits with massive companions, suggesting they are the likely products of secondary exchange encounters.
The first binary is very fascinating as the total mass of the system exceeds the heaviest double neutron star known in our Galaxy. Additionally, it is also heavier than the most massive NS-NS merger candidate in LIGO/Virgo data. The derived companion mass places it as a compact object mass-gap candidate, with a mass larger than the largest precisely measured pulsars and smaller than the lightest known stellar-mass black holes (BHs). If the companion is identified as a massive neutron star, it would provide valuable insights into the equation of state of dense nuclear matter, leading to new constraints. On the other hand, if it is identified as a BH, it would signify the discovery of the first millisecond pulsar-BH system. This would offer a unique opportunity to test the properties and formation mechanisms of black holes.
The second one is an eccentric binary pulsar with a massive carbon-oxygen white dwarf companion, and we have obtained precise measurements of three spin frequency derivatives of the pulsar. The second derivative is too large to be accounted for by the cluster and suggests an ongoing encounter with a third mass around the binary. We discuss the nature of this nearby star and address the effects of the frequency derivatives on other timing parameters.

Speaker: Arumina Dutta

Dutta_Radio2024.pptx

62 Classical theory of the optimal detection in context of radio astronomy

Modern radio astronomy is a data-intensive field with high discovery potential, operating with both large data volumes and high-rate data streams. As is the case in some other fields, not all data in radio astronomy are scientifically useful due to the constant presence of noise. The challenge of detecting signals in the presence of noise has been extensively investigated in the context of signal processing for radars and sonars. The solution to this problem forms the basis of the classical theory of optimal detection. This theory provides a clear mathematical framework for signal processing that attains the minimal possible detection threshold, thereby gathering useful information from data in the most efficient way. Nevertheless, this theory has not been extensively explored in the context of radio astronomy. This presentation will provide an overview of the classical theory of optimal signal detection and illustrate how it can serve as a guiding framework for the development of efficient data analysis techniques for the current and future generations of radio astronomy instrumentation.

Speaker: Vladimir Lenok

lenok-radio2024.pdf

63 How scintillation reshapes small-scale ISM models

Pulsars scintillate because their radio emission is split into multiple interfering paths by the interstellar medium (ISM). For a long time, the dominant model for the responsible medium has been that of a dense and turbulent ionized medium. However, with the advent of modern techniques of scintillometry, phenomena emerged that are difficult to explain in this model. Using data obtained over several years with the Effelsberg 100m telescope, including data from the recently installed wideband receiver (UBB), I will show that the ISM splits a pulsar into many distinct images that are positioned along a straight line and that are stable over long times and wide bands. This requires the ionized ISM to have a filamentary structure on small scales whose physical nature remains a mystery.

Speaker: Tim Sprenger (MPIfR)

tsprenger_RADIO2024_laptop.pdf

64 Modelling the afterglow of binary neutron star mergers

Binary neutron star mergers offer a multitude of observable signatures.
They emit gravitational waves during the in-spiral and merger and produce rich kilo nova signatures from the neutron-rich ejected matter. Furthermore, they launch ultra-relativistic jets which give rise to the prompt and late-time afterglow emission.
The properties of the afterglow depend mainly on the jet structure, the ambient medium density and our line of sight. We use GRMHD simulations of different jet launching scenarios to explore their imprint on the multi-frequency afterglow. In addition we compute radio images of the afterglow in the GHz range in order to capture possible observable signature using the ngVLA long on milliarcsecond scales

Speaker: Christian Fromm (University of Wuerzburg)

19:00 Conference Dinner

Restaurant Thalermühle, Thalermühle 1, 91054 Erlangen
Walking distance from train station.

Friday 15 November

Breakout Session: Short Wavelength Working Group (public)

DSA_Session.txt

65 Misaligned AGN jets from formation to dissipation

Our present understanding of Active Galactic Nuclei (AGN) and their jets is biased towards observations of bright, one-sided and strongly Doppler boosted AGN jets, such as in M 87. However, for an all-inclusive physical description we have to include all flavors of AGN, at all possible jet powers and at all scales. Combining AGN studies across the radio spectrum, from LOFAR wavelengths to mm-VLBI, is crucial to unraveling the underlying physics from black hole feeding to jet formation, acceleration, and collimation, towards the interplay of jets with the host galaxy, leading to AGN feedback. This requires us to combine the small and large scales in AGN from mpc to Mpc. This is challenging with current instruments, but has good prospects with future advances represented by the SKA (-VLBI) and the ngVLA.

To work towards this goal I am focusing on nearby AGN with misaligned jets, including a subset of strongly misaligned, doubled-sided jets, allowing to study the symmetry in these systems. I will show examples on how VLBI can be used to uncover the processes of jet expansion and evolution, specifically for the cases of 3C 293, NGC 3894 and NGC 1052, combining observations from the HSA, EVN+eMERLIN and LOFAR. To overcome the problem of the low number statistics of VLBI studies of double-sided jets required for symmetry studies, I will present possible solutions using clustering algorithms on large radio astronomical datasets such as the LOFAR Two-metre Sky Survey.

Speaker: Anne-Kathrin Baczko

Radio2024.pdf

66 LOFAR 2.0 and the development of station test pipeline

I'll present the current status and commissioning progress of LOFAR2.0. Also, I will show the development of the LOFAR2.0 Real-time station monitor and station test pipeline.

Speaker: Dr Jun Wang

2024_GLOW_JunWang.pdf

67 Short-Wavelength Radio Monitoring of Blazars with Very-High-Energy Emission in Total and Polarized Intensity

We present recent results of the TELAMON program, which is a key-science program on the Effelsberg 100-m telescope to monitor the radio spectra of AGN under scrutiny in astroparticle physics, namely TeV blazars and neutrino-associated AGN. Here, we give an update of the program after ~4 years of observations. Recent results support the association between AGN and ultrahigh-energy cosmic-ray and neutrino emission, where the latter might be characteristically associated with radio flares in blazars. In this context, the Effelsberg telescope yields superior radio data compared to other monitoring programs in the low flux density regime due to its large dish aperture and sensitive instrumentation. This is particularly important as TeV-emitting blazars are often comparatively faint radio sources. Our sample includes all known northern TeV-emitting blazars as well as blazars positionally coincident with IceCube neutrino alerts. In order to compile a unique radio-defined sample of likely neutrino-associated AGN, we follow up on new IceCube alerts and include relevant sources into our monitoring sample. We recover total intensity as well as polarization information at high radio frequencies up to 44GHz. Coordinated and triggered mm-VLBI observations of selected TELAMON sources help to get a better understanding of the physical processes in parsec-scale jets related to high-energy astrophysics.

Speaker: Jonas Heßdörfer (JMU Würzburg)

Radio2024_Hessdoerfer.pdf

11:25 Coffee Break

68 The long-wavelength view from the land down under: highlights from a decade of science with the Murchison Widefield Array

The Murchison Widefield Array (MWA) is an open-access radio interferometric telescope based in the world’s quietest radio astronomy zone: the Murchison Radio-astronomy Observatory (MRO) in rural Western Australia. In its role as the designated Precursor to the Square Kilometre Array (SKA) Low telescope, the MWA has revolutionised our understanding of the low-frequency (80–300 MHz) radio sky since the commencement of operations in mid-2013.

Four key themes drive the scientific impact of the MWA: (i) observing the 21cm signal from the Epoch of Reionisation (EoR), (ii) Galactic and extragalactic surveys, (iii) exploring the time-domain radio Universe, and (iv) studying Solar, heliospheric, and ionospheric phenomena.

In 21cm cosmology, the MWA has allowed astronomers to achieve the tightest limits to-date on the elusive signals of EoR and Cosmic Dawn across a vast redshift range. In the time domain, new rapid-response capabilities, along with the MWA’s unparalleled low-frequency bandwidth and rich archive, have enabled new understanding of a plethora of explosive transient events and characterising hundreds of pulsars, but also raised new challenges to our understanding of the radio sky with the discovery of unusual exotic phenomena such as a new ultra-long period transients. In the Solar, heliospheric and ionospheric regime, the MWA has ushered in a new era of precision broad-band and high time resolution studies of complex emission modes and physical processes at work on the surface of the Sun.

Finally, across the rest of the Universe, Galactic and extragalactic surveys have heralded a paradigm shift in our understanding of both the static and variable low-frequency sky, in both radio continuum and full polarisation. New insights have been unlocked into star formation in our own Galaxy and other galaxies; feeding and feedback mechanisms in some of the most spectacular radio sources across the sky; detections of intergalactic magnetic fields in the Universe’s large-scale structure; detailed studies of novel non-thermal phenomena in complex cluster environments, and more besides.

In this talk, I will present selected highlights from across the depth and breadth of scientific outcomes brought about by the MWA during the last decade of science operations. Alongside the science, I will emphasise the key technical and operational capabilities that made these results possible, and conclude with a look forward to what we can expect in the SKA era, as well as the lessons that we as a community must carry forward with us to the next generation.

Speaker: Chris Riseley (Alma Mater Studiorum - Università di Bologna)

RADIO2024_Talk_CJRiseley.pdf

69 Deep learning-based imaging of MeerKat observations

Machine learning and deep learning-based analysis techniques have recently become prominent in the scientific community. While fields such as particle physics and medical physics already successfully use deep learning methods in their analysis pipelines, these advantages still need to be explored in radio interferometry.
The radionets-project has been working on establishing deep learning-based imaging of radiointerferometric data for five years. Especially for the new generation of radio interferometers such as MeerKat and SKA, deep learning can offer enormous performance gains and improved sensitivities for the existing analysis pipelines. Recent publications have validated the general application of radionets on simulated test data sets for interferometers such as VLA, VLBA, and ALMA. The potential applications for MeerKat are currently being explored, with the goal of training a deep learning model capable of imaging actual observational data. This talk will give an overview of the first reconstructed radio skies, as seen by MeerKat, and an outlook on what deep learning can accomplish to analyze radio interferometer data in the future.

Speaker: Kevin Schmitz

radio2024_schmitz.pdf

70 The integrated synchrotron spectrum of HETDEX blazars with LOFAR surveys

Blazars are under-studied at low radio frequencies in the MHz regime. This is a consequence of the difficulties in reaching the sensitivity and resolution levels necessary for accurate cross-matching to that frequency band. With the release of both the LOFAR Two-metre Sky Survey Data Release 2 (LoTSS DR2) at 140 MHz and LOFAR LBA Sky Survey (LoLSS DR1) at 54 MHz, it is now possible to create complete blazar catalogues in the Northern sky, finding counterparts to blazars identified in Roma-BZCAT(5th Edition) and MOJAVE samples. Here, we present the first results of this study to understand the spectral properties, compactness and radio luminosity distributions of our blazar sample down to the LOFAR bands. Furthermore, we investigate whether the radio-flat spectra (i.e., spectral indices ~0.5) observed in blazars in the GHz regime extend to 144 MHz and 54 MHz, and analyze what deviations from this behavior imply about the physical properties of the underlying plasma population.

Speaker: Hrishikesh Shetgaonkar (University of Wuerzburg)

Shetgaonkar_Erlangen.pptx

12:40 Lunch Break