Polarized Emission In The Mm Band Of Pks0521-365: Alma Observations

The role of magnetic field in the AGN jet physics is still not fully determined. At pc scale, it is known that it is important in the acceleration and collimation processes while at arcsecond scale it could reveal fundamental pieces of the jet dynamics and energetics and its surrounding environment. At intermediate scales, the scenario is more debated. To contribute in this framework, we need to resolve polarized emission even in the low surface brightness extended structures (e.g. lobes). This absolutely requires high sensitivity observations. With the advent of ALMA, now it is possible also in the millimeter, a band which was unexplored by previous facilities. Here I present the impressive images in polarization obtained using ALMA archival multiband data of an ALMA calibrator PKS 0521-365 which represents a prototype of BL Lac object with extended resolved structures (jet and hotspot) at all frequencies from optical to X-rays

The Jet of the BL Lac Object PKS 0521-365 in the mm-Band: ALMA Observations

BL Lac objects are low-power active nuclei exhibiting a variety of peculiar properties caused by the presence of a relativistic jet and orientation effects. Since the jet is closely aligned with the line of sight, it is very difficult to observe unless the angular resolution is high. At millimeter wavelength in particular, until the advent of ALMA, information on the jet emission was lacking from the previous facilities. Here we report our preliminary results on the millimeter emission of PKS 0521-365, one of the most interesting BL Lac objects of the southern sky, using ALMA multifrequency archival data...

Synergies between SKA and ALMA: observations of Nearby Galaxies

The past decade has seen amazing advances in radioastronomy, which led to the construction of brand-new instruments such as LOFAR and ALMA, and the updating of existing ones, e. g. JVLA and e-MERLIN. The SKA will be the spearhead of a future technological development and it will change the way astrophysical topics have been studied so far by opening up new frequency windows with unprecedented spatial resolution and sensitivity. The SKA location in the southern hemisphere makes it particularly suitable to complement ALMA, which is already giving exciting results both on the local and the more distant Universe. Among the possible synergies between SKA and ALMA, we focus on the observations of nearby star forming galaxies. Star formation processes in galaxies involve all the components of the interstellar medium, so the only way to have a complete picture of them is through multifrequency observations. ALMA observes gas and dust emission, while the SKA will trace both the free-free thermal and the non-thermal synchrotron emission. The spatial comparison between these components gives information about the contribution to star formation processes provided by magnetic fields and cosmic rays. The high spatial resolution achievable with ALMA and SKA will make it possible to compare these emissions on very small spatial scales, by resolving single molecular clouds in nearby galaxies. By the time the SKA will start observing, ALMA will have already imaged many nearby galaxies in the southern hemisphere, for which no low frequency data at comparably high spatial resolution will be available. The SKA will fill this gap, and have a profound impact on the studies of nearby galaxies, making valuable contributions to our understanding of star formation processes, and of the role of magnetic fields and cosmic rays in them

The ALMA Re-imaging Project Study

In the first 6 years of ALMA operations, data for more than 1700 projects have been calibrated and manually imaged for quality assessment purposes before being delivered to the PI and being added to the ALMA Science Archive. However, imaging is a time-consuming process and therefore the data-reducers have only created image products for a small fraction of the original data for quality control purposes. We study the feasibility and cost of a potential ALMA Re-Imaging project which would use the newly developed ALMA imaging pipeline to create image products for all the existing data. We here report about the concept and the currrent state of this study

Swift observations of unidentified radio sources in the revised Third Cambridge Catalogue

We have investigated a group of unassociated radio sources included in the Third Cambridge Catalogue (3CR) to increase the multifrequency information on them and possibly obtain an identification. We have carried out an observational campaign with the Swift satellite to observe with the Ultraviolet/Optical Telescope (UVOT) and the X-Ray Telescope (XRT) the field of view of 21 bright NRAO VLA Sky Survey (NVSS) sources within the positional uncertainty region of the 3CR sources. Furthermore, we have searched in the recent AllWISE Source Catalogue for infrared sources matching the position of these NVSS sources. We have detected significant emission in the soft X-ray band for nine of the investigated NVSS sources. To all of them, and in four cases with no soft X-ray association, we have associated a Wide-field Infrared Survey Explorer infrared counterpart. Eight of these infrared candidates have not been proposed earlier in the literature. In the five remaining cases our candidate matches one among a few optical candidates suggested for the same 3CR source in previous studies. No source has been detected in the UVOT filters at the position of the NVSS objects, confirming the scenario that all of them are heavily obscured. With this in mind, a spectroscopic campaign, preferably in the infrared band, will be necessary to establish the nature of the sources that we have finally identified

KAFE: the Key-analysis Automated FITS-images Explorer

We present KAFE—the Key-analysis Automated FITS-images Explorer. KAFE is a web-based FITS image postprocessing analysis tool designed to be applicable in the radio to sub-mm wavelength domain. KAFE was developed to complement selected FITS files with metadata based on a uniform image analysis approach as well as to provide advanced image diagnostic plots. It is ideally suited for data mining purposes and multiwavelength/multi-instrument data samples that require uniform data diagnostic criteria. We present the code structure and interface, the keyword definitions, the products generated for selected users’ science cases, and application examples

Square Kilometre Array Science Data Challenge 1: analysis and results

As the largest radio telescope in the world, the Square Kilometre Array (SKA) will lead the next generation of radio astronomy. The feats of engineering required to construct the telescope array will be matched only by the techniques developed to exploit the rich scientific value of the data. To drive forward the development of efficient and accurate analysis methods, we are designing a series of data challenges that will provide the scientific community with high-quality data sets for testing and evaluating new techniques. In this paper, we present a description and results from the first such Science Data Challenge 1 (SDC1). Based on SKA MID continuum simulated observations and covering three frequencies (560, 1400, and 9200 MHz) at three depths (8, 100, and 1000 h), SDC1 asked participants to apply source detection, characterization, and classification methods to simulated data. The challenge opened in 2018 November, with nine teams submitting results by the deadline of 2019 April. In this work, we analyse the results for eight of those teams, showcasing the variety of approaches that can be successfully used to find, characterize, and classify sources in a deep, crowded field. The results also demonstrate the importance of building domain knowledge and expertise on this kind of analysis to obtain the best performance. As high-resolution observations begin revealing the true complexity of the sky, one of the outstanding challenges emerging from this analysis is the ability to deal with highly resolved and complex sources as effectively as the unresolved source population

Event Horizon Telescope observations of the jet launching and collimation in Centaurus A

Abstract: Very-long-baseline interferometry (VLBI) observations of active galactic nuclei at millimetre wavelengths have the power to reveal the launching and initial collimation region of extragalactic radio jets, down to 10–100 gravitational radii (rg ≡ GM/c2) scales in nearby sources1. Centaurus A is the closest radio-loud source to Earth2. It bridges the gap in mass and accretion rate between the supermassive black holes (SMBHs) in Messier 87 and our Galactic Centre. A large southern declination of −43° has, however, prevented VLBI imaging of Centaurus A below a wavelength of 1 cm thus far. Here we show the millimetre VLBI image of the source, which we obtained with the Event Horizon Telescope at 228 GHz. Compared with previous observations3, we image the jet of Centaurus A at a tenfold higher frequency and sixteen times sharper resolution and thereby probe sub-lightday structures. We reveal a highly collimated, asymmetrically edge-brightened jet as well as the fainter counterjet. We find that the source structure of Centaurus A resembles the jet in Messier 87 on ~500 rg scales remarkably well. Furthermore, we identify the location of Centaurus A’s SMBH with respect to its resolved jet core at a wavelength of 1.3 mm and conclude that the source’s event horizon shadow4 should be visible at terahertz frequencies. This location further supports the universal scale invariance of black holes over a wide range of masses5, 6