Bonn-Dwingeloo Neighbourhood VLBI Meeting

4 July 2017
MPIfR
Europe/Berlin timezone
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Contribution List

Displaying 24 contributions out of 24
Session: Session I
We present total and linearly polarised 3 mm GMVA images of a  sample of blazars and radio galaxies from the VLBA-BU-BLAZAR 7 mm monitoring  program aimed to probe the innermost regions of AGN jets and locate the sites  of gamma-ray emission observed by Fermi-LAT. The reduced opacity at 3 mm and improved angular resolution, of the order of 50 $\mu$arcseconds, allow us to estimate the angu ... More
Presented by Dr. Carolina CASADIO on 4 Jul 2017 at 11:23
Session: Session I
Very Long Baseline Interferometry (VLBI) Observations at 86$\,$GHz reach a resolution of about 50 $\mu$as and sample the scales as small as 10$^3$--10$^4$ Schwarzschild radii of the central black hole in Active Galactic Nuclei (AGN), and uncover the jet regions where acceleration and collimation of the relativistic flow takes place. Synchrotron radiation becomes optically thin at millimetre wavel ... More
Presented by Ms. Dhanya G. NAIR on 4 Jul 2017 at 10:59
Session: Session III
The high resolution and high sensitivity to diffuse emission at low radio frequencies make LOFAR a unique discovery instrument. I will outline how I use its potential to time the activity of AGN hosted by massive, multi-core galaxies found in nearby galaxy clusters.
Presented by Dr. Aleksandar SHULEVSKI on 4 Jul 2017 at 15:42
Session: Session I
Using Very Long Base Interferometry (VLBI), the Bar and Spiral Legacy (BeSSeL) survey has provided distances and proper motions for maser-bearing young massive stars (Reid et al. 2009,2014), allowing an accurate measure of the spiral Galactic structure and kinematics. By the same technique, we are planning to map the inner Galaxy and bulge using positions and velocities of SiO masers stars (Bulge ... More
Presented by Prof. Huib VAN LANGEVELDE on 4 Jul 2017 at 11:35
Session: Session II
Fast radio bursts (FRBs) are a new radio transient phenomena that puzzles scientists over their nature. These millisecond, Janksky bright single pulses are seen with dispersion measures (DMs) several times larger then those caused by the electron density in our own Milky Way and therefore thought to be of extra-galactic origin. Their non-repetitive behaviour (only one FRB has seen to repeat thus f ... More
Presented by Leonard HOUBEN on 4 Jul 2017 at 13:30
Session: Session II
I will present new results on spectral index imaging of several AGN using multi-frequency space VLBI observations with RadioAstron, in combination with ground array images. I will introduce a GUI-based Python tool for spectral analysis of VLBI data, that was used to produce the results.
Presented by Ms. Laura VEGA GARCÍA on 4 Jul 2017 at 14:42
Session: Session III
Radio observations play an important role to understand the processes involved in the formation and evolution of stellar and substellar objects. In this context, we have made several contributions to binary stars belonging to the AB Doradus moving group, namely, AB Dor A/C (Guirado et al. 2006; 2011), AB Dor Ba/Bb (Azulay et al. 2015), and HD 160934 A/c (Azulay et al. 2014; 2017). In these cases, ... More
Presented by Dr. Rebecca S. AZULAY on 4 Jul 2017 at 15:54
Session: Session II
As a participant in the Black Hole Cam project, JIVE undertook to develop a fringe-fitting tool in the Casa dataprocessing package closely modeled on the AIPS FRING task. A Python prototype has been completed and is now in preliminary use by colleagues at Radboud University Nijmegen; the C++ code to apply the calibrations is now mature, and a first draft of a C++ implementation is now complete alt ... More
Presented by Dr. Des SMALL on 4 Jul 2017 at 14:18
Session: Session III
Many active galactic nuclei (AGN) show a spectral peak in their radio spectra. Peaked-spectrum radio sources (including gigahertz-peaked spectrum and compact steep spectrum sources) are radio galaxies that often display small angular extents, suggesting that they are either very young AGN or are confined by a dense surrounding medium. We here present a spectacular sample of 1484 low-frequency peak ... More
Presented by Dr. Joseph CALLINGHAM on 4 Jul 2017 at 16:06
Session: Session I
We performed full polarimetric VLBA observations of water masers towards the Turner-Welch Object in the W3(OH) high-mass star forming complex. This object drives a synchrotron jet, which is quite exceptional for a high-mass protostar, and is associated with a strongly polarized water maser source, W3(H$_2$O), making it an optimal target to investigate the role of magnetic fields on the innermo ... More
Presented by Dr. Ciriaco GODDI
Session: Session I
Understanding how mass accretion and jet formation occurs near the central engine of AGN has been one of major challenges in modern astrophyiscs. The apparent size of the jet forming region is desperately small even for an extraordinary massive BH system (10Rs=0.001pc for a BH mass of 10^9Msun), making a direct comparison of theories and observations difficult. Therefore, it is indispensable to im ... More
Presented by Mr. Jae-Young KIM on 4 Jul 2017 at 11:47
Session: Session II
SKA phase 2 sensitivity could be achieved at relatively low cost if we can piggyback a radio astronomy receiver on solar concentrators, of which four square kilometres are operating in the form of solar power towers. However the mirror arrays form a speckle pattern rather than a point focus, but we can restore full sensitivity in principle using a focal-plane array to collect the power from ... More
Presented by Dr. Alan ROY on 4 Jul 2017 at 13:54
Session: Session III
After a review of the robopol project and its main findings in the angle domain, we will present average R-band optopolarimetric data, as well as variability parameters, from the first and second RoboPol observing season. We investigate whether gamma-ray-loud and gamma-ray-quiet blazars exhibit systematic differences in their optical polarization proper- ties. We find that gamma-ray-loud blazars h ... More
Presented by Dr. Emmanouil ANGELAKIS on 4 Jul 2017 at 16:18
Session: Session II
The Event Horizon Telescope (EHT) project aims to image the supermassive black holes in the center of our Galaxy (Sgr A*) and M87 at event horizon scales using very long baseline interferometry (VLBI) at (sub-)millimetre wavelengths. The EHT currently consists of a number of telescopes around the globe. A telescope in Africa will greatly improve the uv-coverage and the image quality. We prop ... More
Presented by Dr. Cornelia MUELLER on 4 Jul 2017 at 14:30
Session: Session II
The powerful radio galaxy Cygnus A is one of the very few targets where the jet acceleration and collimation region can be probed directly through VLBI imaging. Through a rich, multi-wavelength VLBI data set, we were able to reconstruct the two-sided collimation profile of the outflow, and to follow its evolution from scales of a few hundreds to millions Schwarzschild radii. Preliminary results su ... More
Presented by Dr. Biagina BOCCARDI on 4 Jul 2017 at 14:06
Session: Session I
The jets of powerful radio galaxies are known to play a vital role in regulating the gas distribution of the host galaxy. Evidence for this includes observations of fast outflows of neutral hydrogen gas detected in absorption in a number of radio galaxies, though these observations mostly lacked the resolution to pinpoint the location of the outflow with respect to the jet system. However, this ca ... More
Presented by Dr. Robert SCHULZ on 4 Jul 2017 at 10:35
Session: Session III
I will briefly discuss the interpretation of the peculiar light curve of J1415+1320, that shows time-symmetric and recurring U-shaped features across the cm-wave and mm-wave bands, which we call Symmetric Achromatic Variability (SAV). Although a common proposal to explain simmilar features in blazar radio light curves are Extreme Scattering Events (ESEs), this is shown to be not viable for this pa ... More
Presented by Dr. Walter MAX-MOERBECK on 4 Jul 2017 at 15:30
Session: Session II
Blazars, a subclass of AGN jets, show extreme flux variability across the electromagnetic spectrum from radio to gamma-rays. A challenge to theoretical interpretation is the rapid flux variability at GeV energies, which implies an origin from ultra-compact emission regions (< sub-pc). The exact location of the gamma-ray emitting region within the AGN is also controversially discussed. The pri ... More
Presented by Ms. Efthalia TRAIANOU on 4 Jul 2017 at 14:54
Session: Session I
The $\gamma$-ray sky is strongly dominated by blazars, i.e. AGN with relativistic jets oriented closely with our line of sight. Radio galaxies are their misaligned counterpart, and make up about $\sim$1-2% of all AGN observed by *Fermi*-LAT. Nonetheless, they provide us with a view of AGN jets which is less biased by Doppler boosting effects, and allow us to test jet production and emission models ... More
Presented by Mr. Roberto ANGIONI on 4 Jul 2017 at 10:47
Session: Session III
We use the VLBI technique to obtain precise astrometric measurements to several young stars in nearby star-forming regions belonging to the galactic structure known as the Gould's Belt. These measurements will allow us to investigate the structure of the clouds and their internal kinematics and eventually to characterize the overall dynamics of the Belt. I will present the current status of the pr ... More
Presented by Dr. Gisela Noemí ORTIZ-LEÓN on 4 Jul 2017 at 16:42
Session: Session III
Stars similar to our Sun undergo radical changes as their lives draw to an end. After swelling up to huge red giants, they start to pulsate, blowing off large clouds of gas and dust, to create intricately shaped and mesmerizing planetary nebulae. The remaining part of the star collapses under gravity, creating a compact white dwarf to slowly cool and fade away. One of the pivotal questions in this ... More
Presented by Dr. Gabor OROSZ on 4 Jul 2017 at 16:30
Session: Session I