Recent Helena Kluyver visitors



Preeti Kharb visited ASTRON for ten days in March-April of 2018. She is currently a faculty member at the National Centre for Radio Astrophysics - Tata Institute of Fundamental Research (NCRA - TIFR) in Pune, India. She specialises in multi-wavelength observational studies of active galactic nuclei (AGN). During her visit to ASTRON, she worked on collaborative projects with Raffaella Morganti of ASTRON. Together, they identified at least two samples of radio sources that appeared to have intermediate radio properties between the "radio-loud" Fanaroff-Riley type I (FRI) radio galaxies and the "radio-quiet" Seyfert galaxies. These sources could turn out to be the key to resolving the long-standing question of the radio-loud/radio-quiet AGN divide. A couple of proposals were prepared for international facilities including the Very Long Baseline Array (VLBA) and the Giant Metrewave Radio Telescope (GMRT), for carrying out continuum as well as line observations of a subset of sources belonging to these samples. A Ph.D. student from Kapteyn University/ASTRON working with Raffaella Morganti was also involved in these projects, so that when the data are eventually acquired, the student could participate more fully in the projects. This Ph.D. student will soon be visiting NCRA and GMRT at Pune, India, to move our collaborative projects ahead.


Prof. Nectaria Gizani used the Helena Kluyver fellowship in June 2016 to visit JIVE - ASTRON and work on finalizing the analysis of the radio galaxy 3C310's global VLBI data. "The visit was fruitful from all aspects in terms of work and interaction with fellow scientists. The paper of this analysis is almost at its end, and we hope to publish it soon. I would like to sincerely thank the Committee of the Helena Kluyver fellowship scheme for their attention and for offering this fellowship to me. Coming from Greece with all the financial difficulties, and being a woman, the whole plan to conclude my work on the radio galaxy would have been impossible. It is indeed a very well thought financial program."


Prof Imke de Pater (Berkeley) will be paying us multiple visits this year in the context of the Helena Kluyver Programme.
Among other things, she is taking this opportunity to reduce a unique set of simultaneous observations (in 2013) of Jupiter with the WSRT (MFFE 6, 21, 35 and 92 cm) and LOFAR (LBA and HBA). This will produce an unusually wide spectrum (50-5000 MHz) that can be used to test new (and old) radiation models of our ruling planet. The polarization information will help to separate Jupiter's thermal (atmospheric) and non-thermal (magnetosphere) emissions.

Imke was the first to image Jupiter's radio emission with the WSRT, as part of her Leiden thesis in the late 70's. Since Jupiter moves w.r.t. the background sky, and rapidly rotates around its axis, this challenged the WSRT observations and data reduction systems considerably. After this success, she has been studying Solar System objects ever since (Her own model of Jupiter's radio emission has stood for 20 years). She recently served as department chair in Berkeley.

The picture shows her reducing the WSRT data, assisted by Richard Strom and Ger de Bruyn. The latter is wielding the rapier of NEWSTAR, still the ablest data reduction system for WSRT data (until APERTIF comes along, of course). The associated LOFAR data is being reduced by Julien Girard (Paris).

Imke will be back in Dwingeloo in May.
Liese van Zee visited ASTRON for three months in August-November 2015.  She is currently an associate professor of astronomy at Indiana University in Bloomington.  Her research interests include studies of the gaseous and stellar properties of nearby galaxies and investigation of the formation and evolution of galaxies.  The primary purpose of her visit to ASTRON was to analyze neutral hydrogen data for galaxies in the EDGES Survey, a deep near-infrared imaging survey of nearby galaxies.  During her visit, she processed data for several galaxies in the WSRT archive and recovered data for several others that were no longer easily available through the archive.  Ultimately, the gas distributions and kinematics will be compared with the faint extended stellar populations in these galaxies.  Her visit also coincided with a week-long conference on the Life Cycle of Gas in Galaxies during which she presented a comparison of stellar and gaseous distributions in nearby dwarf irregular galaxies.  She also presented a talk during Astrofest that highlighted her planned future work on correlating gas kinematics, resolved star formation histories, and the chemical enrichment processes in low mass galaxies.  During her visit, she interacted with ASTRON staff on a variety of topics, including learning about science planned with Apertif and LOFAR.  She also participated in several activities organized by the Astronomy group and helped with the liquid nitrogen demonstration during Open Dag.


Delphine PerrodinDelphine Perrodin visited ASTRON for one month in April/May 2014. She is currently a postdoctoral fellow at the Osservatorio Astronomico di Cagliari in Italy, home of the Sardinia Radio Telescope (SRT). Delphine is involved with The Large European Array for Pulsars (LEAP) project, which performs simultaneous observations of millisecond pulsars at 5 large European radio telescopes (Jodrell Bank, Effelsberg, Nançay, as well as the Westerbork Synthesis Radio Telescope and SRT). By correlating and coherently adding the data from all telescopes, the signal-to-noise of pulsar observations is significantly increased, which in turn could lead to the first direct detection of gravitational waves. Delphine is working on implementing the LEAP project at the Sardinia Radio Telescope (SRT), while also working on the analysis of the correlated data from all telescopes. At SRT she has been working on the commissioning of the ROACH pulsar backend and computer cluster (e.g. installing the necessary hardware and software), performing pulsar tests, coordinating monthly LEAP observations, and working on automating pulsar data acquisition, analysis and storage. During her stay at ASTRON, she had very productive work sessions with ASTRON collaborators Cees Bassa, Gemma Janssen and Roy Smits. The collaborative work helped her optimize the automation of data acquisition, analysis and storage at SRT. She worked on incorporating SRT into the LEAP correlation software. During her stay, Delphine and ASTRON collaborators coordinated the simultaneous observation at SRT and WSRT of a bright pulsar. This helped them find the very first fringe, therefore the time offset, between the two telescopes. This is a great step forward for LEAP and SRT, since it will now be possible to correlate the SRT data with the other four telescopes and obtain 5-telescope additions, thereby significantly increasing the signal-to-noise of the LEAP detector.


Natalia Lewandowska visited ASTRON for two months from October until December 2013. She is currently a PhD student at the Astronomy department of the University of Wuerzburg in Germany, working under the supervision of Prof. Karl Mannheim. One of her main research interest is multi-frequency studies of giant pulses emitted by radio pulsars. Detected for the first time in the case of the Crab pulsar, nowadays a small group of pulsars is known to emit such very bright, seemingly random single pulses. The question of their emission mechanism is still unsolved. To unravel it, simultaneous multi-wavelength studies of the respective pulsars are carried out, in order to search for a correlation between radio giant pulses and photons at different wavelengths. The central aspect of Natalia's PhD thesis is to perform this analysis for the Crab pulsar with radio and gamma ray photons. She uses data taken with the Effelsberg radio telescope, the WSRT and the MAGIC telescopes.
An alternative branch of her studies deals with low-frequency observations of giant radio pulses from the Crab pulsar, for which she uses data taken with LOFAR. During her stay at ASTRON Natalia worked on single pulse radio data in collaboration with Vlad Kondratiev. Weekly pulsar meetings gave rise to discussions about different branches of pulsar research and provided a pleasant work environment. While at ASTRON she also discussed further options for single pulse studies using LOFAR and also ALMA in the future. Furthermore she assisted in the Open Day at ASTRON in October 2013 and gave an astrolunch talk at the end of her stay.

Natalia would like to thank ASTRON and the Helena Kluyver organizers for their support, the pulsar group for their hospitality and Vlad Kondratiev, Gemma Janssen, Maura Pilia, Charlotte Sobey, Anne Archibald, Roy Smits and also Dan Stinebring for many fruitful discussions making her stay most productive.

Rosita Paladino visited ASTRON for one month from mid September to mid October 2013, and plans to visit it again in Feb-March 2014. She is currently a member of the Italian ALMA Regional Center node, in Bologna (Italy).

Her main scientific interest is the study of star formation processes in galaxies, particularly focusing on the role of magnetic fields in star formation, which is relevant, even though so far not understood. The best way to study this problem is facing it from many different points of view, observing the different components of interstellar medium, and analyzing their correlations. Observations in the mm range give insights on the chemical composition and physical conditions in molecular clouds, where star formation happens. Long wavelength observations allow in turn to study the non-thermal components and magnetic fields in the interstellar medium, and the cosmic rays propagation processes.

As member of the nearby galaxies working group of the LOFAR Magnetism KSP, she is involved in the LOFAR Survey of Nearby galaxies project, partly observed during LOFAR observing Cycle 0. During her visits at ASTRON  she focuses on the data reduction of some of these observations.


O. Ivy Wong visited ASTRON for 3 weeks during the month of April in 2013.  She is an Australian Research council Super Science Fellow working at CSIRO Astronomy & Space Science in Sydney, Australia.  Her primary research interests are in the physical processes of star formation and galaxy evolution using multiwavelength observations.  The main purpose of her visit is to work with Gyula Jozsa on recent pilot observations of HI in blue early-type galaxies using the WSRT. The aim of this project is to use HI to shed light on what caused the sudden truncation of star formation in a local sample of post-starburst galaxies which appear to be descendants of blue early-type galaxies.  During her visit, she also had many useful discussions with HI experts based both at ASTRON and Groningen. Ivy thanks ASTRON and the Helena Kluyver program for their hospitality and support.





Preeti Kharb visited JIVE/ASTRON for 3 months from July to October 2012, as a postdoctoral fellow from the Rochester Institute of Technology (RIT) in Rochester, NY. She is currently a faculty member at the Indian Institute of Astrophysics  (IIA) in Bangalore, India. Her main research interest is the phenomenology of active galactic nuclei (AGN). She follows a multiwavelength observational approach to understand the workings of jets in AGN. During her Helena Kluyver visit, she worked with Leonid Gurvits & Giuseppe Cimo at JIVE, and Ger de Bruyn at ASTRON, on data from multi-epoch space VLBI observations of the extreme scintillator quasar, J1819+3548. The premilinary results from this study were included in a presentation by Giuseppe Cimo in the 11th European VLBI Network (EVN) Symposium & Users Meeting, held in Bordeaux, France, in October 2012, and will be appearing as a conference proceedings soon. She also collaborated with Zsolt Paragi at JIVE and with him as PI, successfully obtained observing time on the EVN to study a dwarf galaxy with an intermediate mass (10^5 M_sun) black hole in its center. Weekly meetings with astronomers at ASTRON, and especially the AGN meetings with Raffaella Morganti, Elizabeth Mahony, Ilse van Bemmel, and others, made for a stimulating work environment. The presence of several international students for the JIVE/ASTRON Summer school coinciding with the visit, also made it fun. Preeti Kharb would like to thank JIVE/ASTRON and the Helena Kluyver program organizers for a productive and memorable summer.


Simona Vegetti visited ASTRON for 2 months from the beginning December 2011 till the end of January 2012. She is currently a postdoctoral Pappalardo Fellow at the Massachusetts Institute of Technology. Her main research interest is testing cosmological models at the small scales using strong gravitational lensing. She came to ASTRON to work with John McKean on the Strong Lensing at High Angular Resolution Program (SHARP). SHARP was founded by S. Vegetti, J. Mckean, D. Lagattuta, M. Auger, C. Fassnacht and L. Koopmans with the goals of searching for low mass substructure in cosmological distant galaxies, built up information on the substructure mass function and compare with prediction from numerical simulations. During Simona’s visit a SHARP workshop was held at ASTRON and the first results by the collaboration on the detection of a dwarf galaxy at redshift 1 were published in Nature. Simona really enjoyed her stay and would like to thank ASTRON and the Helena Kluyver program.


Lakshmi Saripalli visited ASTRON for three months from September to November 2011. Her research centers on radio galaxy populations and addresses questions relating to their origin, morphologies and growth. She would like to thank the Helena Kluyver women visitor program for the opportunity to visit ASTRON at the exciting time when science with LOFAR has begun to take its sure steps towards solid results. In her visit she plans to collaborate with Dr Raffaella Morganti on a few projects with the common theme of radio galaxies. One of the projects involves HI absorption studies of a sample of radio galaxies where the interest is to determine the detection rate of absorbing neutral hydrogen gas towards the core regions. Combining this sample with previous samples will enable a wider study that will allow exploration of several interesting questions. Her stay is also aimed at wider interactions on the general theme of radio galaxy science. A sensitive radio survey that she recently carried out forms the backdrop to their discussions where they use the imaging data on faint radio galaxy populations to identify future lines of study particularly in the area of their origin and lifecycles. Lakshmi is a staff member at the Raman Research Institute, Bangalore (India).


Prof Renée Kraan-Korteweg - Head of the Department of Astronomy at the University of Capetown (2011)
As part of her sabbatical leave, Renee Kraan-Korteweg spent about one third of the period March to August 2011 at ASTRON - the remainder at the Kapteyn Institute. Renee holds the Chair of Astronomy and is Head of the Astronomy Department at the University of Cape Town (UCT), and one of the (founding) directors of the Research Centre of Astrophysics, Cosmology and Gravity there. Her research interests encompass extragalactic large-scale structures, dynamics in the local Universe, cosmic flow fields and systematic HI-surveys. In this she is particular passionate about identifying galaxies (like Dwingeloo 1) and unveiling the large-scale structures of galaxies hidden by the Zone of Avoidance. During her visits, she interacted mostly with the astronomers involved in the preparation of the future Apertif HI-surveys. Given the complementarity of the large HI-projects planned with the SKA Pathfinders Apertif, MeerKAT and ASKAP, their discussions focused on future research collaborations between UCT and ASTRON, as well as joint student supervision options. She gave a lunch talk on Astronomy Development in South Africa, a colloquium on the Great Attractor, and a talk at the bi-monthly HI meetings on the importance of the WNSHS in resolving bulk flow controversies due to the Zone of Avoidance. She furthermore assisted at the Girlsday organized by ASTRON, JIVE & NOVA on April 14 (see photo).

While at ASTRON, she was named second runner-up by the Minister of Science and Technology of South Africa for the "Distinguished Women in Science Awards". The awards in 2011 were in honour of "Promoting Women's Access and Excellence in Reseach and Innovation Careers", hence much in line with the aims of the Helena Kluyver programme.


Katarzyna Otmianowska-MazurKatarzyna Otmianowska-Mazur  visited ASTRON for two weeks (8-19) in November 2010. She started a scientific collaboration with Marijke Haverkorn (ASTRON) on the subject of modeling of the evolution of the magnetic field structure, cosmic ray distribution and gas density topology in the Milky Way. The project involves making MHD simulations of the cosmic-ray driven dynamo model for the Milky Way as a barred galaxy in order to get results similar to the observed polarized intensity, magnetic vectors, gas velocity and HI distribution. The scientific field: she specializes in magnetohydrodynamical (MHD) models of galaxies of all astrophysical scales. Her research is focused on issues like reconnections in galactic interstellar medium, cosmic ray-driven dynamo in galaxies, magnetic field evolution in spiral, barred and irregular galaxies and in Virgo cluster galaxies. Since 2005, Katarzyna holds the post of the Director of the Astronomical Observatory at Jagiellonian University in Krakow. She is also the PI of the LOFAR project in Poland.


Luisa OstoreroLuisa Ostorero  visited ASTRON for two weeks in August 2010. She is currently a postdoc fellow at the University of Torino, and she was one of the 2009 Italian fellows of the L'Oreal-UNESCO programme "For Women in Science". Her main research topic is the study of active galactic nuclei with a multiwavelength perspective. The project which brought her to ASTRON focuses on the class of compact radio galaxies, likely representing the early phase of the evolution of active galaxies. In collaboration with Raffaella Morganti, Luisa carried out a program of observations of the HI absorption in a sample of X-ray emitting compact radio galaxies. The observations were performed with the WSRT during 2008-2009, and analysed during Luisa's stay. The data acquired with the WSRT will be relevant for the investigation of the connection between the absorptions of the radio and X-ray radiation in these galaxies: this connection is expected to shed light both on the origin of their X-ray emission and on the properties of the absorbing circumnuclear matter.


Anya Bilous Anya Bilous visited ASTRON in June-August 2010. Currently, she is a PhD student at the University of Virginia, working within the NRAO pulsar group under the supervision of Dr. Scott Ransom. Her research interests concentrate mainly on pulsars, especially on multiwavelength single-pulse studies. During her stay at ASTRON she used the data from the just-opened LOFAR telescope to look for Abnormally Intensive Pulses, which have been recently discovered at frequencies below 30 MHz. The huge bandwidth of LOFAR allowed her to do a thorough single-pulse study of pulsars with Abnormally Intensive Pulses at frequencies from 30 to 170 MHz, revealing the differences in single-pulse properties in this frequency range. Miss Bilous would like to thank ASTRON and the Helena Kluyver Female Visitor Programme for a wonderful experience of working in ASTRON.


Trish HenningPatricia (Trish) Henning  visited ASTRON in June 2010. She is an associate professor of physics and astronomy at the University of New Mexico in Albuquerque, and also is the director of its Institute for Astrophysics. She is currently serving as the vice chair of the US SKA Consortium. Her research efforts include large surveys for HI galaxies for mapping large-scale structure, and studying the HI properties of the galaxies themselves. She leads a low-Galactic-latitude HI survey with the Arecibo L-band Feed Array, and collaborates on other high-latitude projects. During her visit, she discussed with ASTRON staff and other visiting astronomers the opportunities for future extragalactic HI emission surveys with WSRT and Apertif. While at ASTRON, she gave a colloquium looking at the state of large HI surveys, and their future into the SKA era.


Snezana StanimirovicSnežana Stanimirović visited ASTRON in mid June-July 2010. She is currently an assistant professor of astronomy at the University of Wisconsin, Madison. Her research interests involve studies of the interstellar and intergalactic medium through various radio surveys (e.g. GALFA-HI, GASKAP). With ASTRON colleagues, she explored possibilities for future very sensitive observations of HI in absorption with the WSRT and large-scale HI emission surveys with Apertif. Snežana also gave a lecture for the summer students focusing on HI studies of the interstellar medium. For about ten days she was accompanied by a graduate student Min-Young Lee (UW) to work on the analysis of the interface region between atomic and molecular gas across the Perseus molecular cloud.


Mousumi RoyMousumi Roy visited ASTRON for 5 weeks in Nov-Dec 2009. Currently, she is pursuing a PhD under Dr. Danielle George at the University of Manchester, within the Microwave and Communication Systems Research group. Her research interests involve design of MMIC-based front-end transceiver components, with special emphasis on LNAs. During her stay in ASTRON, in collaboration with Roel Witvers and Laurens Bakker, she helped set-up an on-wafer probing system, to be used in conjunction with an automated tuner used for noise parameter measurements and the state-of-the-art PNAX. Using this set-up, she performed noise and S-parameter measurements and characterization of wafer pHEMT and mHEMT transistors of various technologies (GaAs, InP) and gate lengths, from four different foundries, across a wide range of biases. The aim of this noise modelling and characterization work was to analyze the suitability of these transistors in front-end LNA designs for the SKA project. Miss Roy and Dr. George would like to thank ASTRON and the Helena Kluyver Female Visitor Programme for giving Miss Roy an opportunity to work in ASTRON.


Paola Di MatteoPaola Di Matteo visited ASTRON in November 2009. Currently, she is a postdoc fellow at the Paris Observatory. Her main research interests include the physical processes related to galaxy interactions and mergers and how they affect the observedproperties of galaxies. During her stay at ASTRON, in collaboration with Paolo Serra, she beganthe analysis of N-body simulations of gas-rich major mergers in order to study the properties of stellar populations in the early-type merger remnants and how they compare with the gas distribution. The results of this study will be compared to observational data of stellar populations and age gradients in early-type galaxies and to their HI distribution obtained with the Westerbork radio telescope.


Rym FeliachiRym Feliachi visited ASTRON in the period January-March 2009. Her research interest is mitigation of radio frequency interference by using cyclostationary signal processing techniques. Currently she is pursuing a PhD at the Prism Institute of the University of Orleans. She investigates the effectiveness of cyclostationary spatial filters to suppress interference, by theoretical analysis, simulation, and by experimental verification. During her stay at ASTRON, she applied her algorithms on LOFAR data. She demonstrated experimentally that cyclostationary spatial filters have certain advantages over “classic” spatial filters. As cyclostationary techniques offer a better separation between transmitter signals and noise signals, cyclostationary filters are less sensitive to calibration errors. When applied to a strong pager signal in the LOFAR band at 169 MHz, the cyclostationary filter showed a 10 dB better suppression than the classic spatial filter approach.


Isabella Prandoni visited ASTRON for three weeks in August 2008. At ASTRON, she has worked on the First Look Survey, using WSRT/VLA and GMRT data, and exploiting the available multiwavelength information (optical, FIR, etc.). This work is mainly aimed at studying the radio spectral properties of the faint AGN population, in order to disentangle different accretion regimes. This also represents preparatory work for what we will be able to do in more detail with Lofar. Isabella is a staff astronomer at the Institute of Radioastronomy in Bologna and an expert on radio and optical deep surveys. Her main scientific interest is the understanding of the faint radio population, a mix of star-forming galaxies and active galactic nuclei (AGN). She is particularly interested in the physical and evolutionary properties of the low-luminosity AGN component. 


Elena Redkina visited ASTRON for a period of 3 weeks during summer 2007. She performed the assembling and measurements of the 16 Vivaldi element array, which was initially designed by her in collaboration with antenna designers of ASTRON. This array was used for verification of the combined EM-MW model of the connected Vivaldi elements with microstrip feed excitations. The positive measurement results of this array complement the initial modeling study and are currently being prepared for submission to AP Trans. journal.
Elena is currently a lecturer at the Sevastopol National Technical University, Crimea, Ukraine.


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