Related papers: Structure, spectra and variability of some GPS rad…
We present a catalogue of positions and correlated flux densities of 410 flat-spectrum, compact extragalactic radio sources, previously detected in the AT20G survey. The catalogue spans the declination range -90deg, -40deg and was…
The radio spectral index is a powerful probe for classifying cosmic radio sources and understanding the origin of the radio emission. Combining data at 147 MHz and 1.4 GHz from the TIFR GMRT Sky Survey (TGSS) and the NRAO VLA Sky Survey…
We observed 20 Palomar-Green (PG) quasars at low redshift ($z<0.5$) with total flux density > 1 mJy, including 4 radio-loud quasars (RLQs) and 16 radio-quiet quasars (RQQs), using the Very Long Baseline Array (VLBA) at 5 GHz. Ten RQQs are…
We report the results of high-resolution 5 GHz Very Long Baseline Array and European VLBI Network observations of 36 nearby galaxies, an extension of the Legacy e-MERLIN Multi-band Imaging of Nearby Galaxies (LeMMINGs) survey. Our sample…
We present VLBI (EVN+MERLIN) observations of a sample of three low-redshift radio-intermediate PG quasars (RIQ) with flat and variable radio spectrum (III Zw 2, PG 1309+355, PG 2209+184). Their radio-to-optical flux ratio (R) is slightly…
Compact symmetric objects (CSOs) are intrinsically compact extragalactic radio sources that are thought to be the progenitors of classical radio galaxies. To date, evolutionary models have mainly focused on the formation and growth of…
High redshift active galactic nuclei (AGN) provide key insights into early supermassive black hole growth and cosmic evolution. This study investigates the parsec-scale properties of 86 radio-loud quasars at z $\geq$ 3 using very long…
The Compact Symmetric Objects (CSOs) are small (<1 kiloparsec) and powerful extragalactic radio sources showing emission on both sides of an active galactic nucleus and no signs of strong relativistic beaming. They may be young radio…
Multifrequency Very Long Baseline Array (VLBA) observations were performed to study the radio morphology and the synchrotron spectra of four high frequency peaking radio sources. They are resolved in several compact components and the radio…
We present new deep multi-frequency radio-polarimetric images of a sample of high redshift radio galaxies (HzRGs), having redshift between 1.7 and 4.1. The radio data at 4.7 and 8.2 GHz were taken with the Very Large Array in the A…
SDSSJ1539+3954 ($z\approx 1.935$), a radio-quiet weak-line quasar (WLQ), exhibited exceptional X-ray variability in 2019$-$2020, with its X-ray flux increasing by over 20 times from 2013 to 2019 and subsequently dropping by at least a…
VLA imaging at kiloparsec-scale resolution of sixteen core-dominated radio-loud QSOs is presented. Many objects appear to display variable radio emission and their radio morphologies are significantly smaller than those of steep-spectrum…
We present the detection of compact radio structures of fourteen radio-loud narrow line Seyfert 1 (NLS1) galaxies from Very Long Baseline Array observations at 5 GHz, which were performed in 2013. While 50\% of the sources of our sample…
Recent sensitive wide-field radio surveys, such as the LOFAR Two Meter Sky Survey (LoTSS), the LOFAR LBA Sky Survey (LoLSS), and the Very Large Array Sky Survey (VLASS), enable the selection of statistically large samples of peaked-spectrum…
We summarize previous VLBI observations of Sgr A* at millimeter wavelengths and present new results from VLBI observations at 86 and at 215 GHz. At 86 GHz the measured closure phase is close to zero, consistent with a point-like or…
It is anticipated that future space-born missions, such as Gaia, will be able to determine in optical domain positions of more than 100,000 bright quasars with sub-mas accuracies that are comparable to very long baseline interferometry…
We present radio observations of 19 candidate compact steep-spectrum (CSS) objects selected from a well-defined, complete sample of 52 B2 radio sources of intermediate strength. These observations were made with the VLA A-array at 4.835…
We present the results of multi-wavelength observations of cores and hotspots at L, C, X and U bands with the Very Large Array, of a matched sample of radio galaxies and quasars selected from the Molonglo Reference Catalogue. We use these…
Our previous work identified a class of SDSS quasars exhibiting multiple Gaia detections, classifying them as candidates for various astrophysical systems such as quasar-star pairs, dual quasars, and gravitationally lensed quasars. In this…
We show an archival 1.4-GHz Very Large Array (VLA) image of the core-dominated triple (CDT) radio source J1628+3906, along with a recent high-resolution 5-GHz Very Long Baseline Interferometry (VLBI) image of its core. This core is resolved…