The dynamics of quantised vorticity in neutron star interiors is at the heart of most pulsar glitch models. However, the large number of vortices (up to ≈1013) involved in a glitch and the huge disparity in scales between the femtometre scale of vortex cores and the kilometre scale of the star makes quantum dynamical simulations of the problem computationally intractable. In this paper, we take a first step towards developing a mean field prescription to include the dynamics of vortices in large-scale hydrodynamical simulations of superfluid neutron stars. We consider a one-dimensional setup and show that vortex accumulation and differential rotation in the neutron superfluid lead to propagating waves, or ‘avalanches’, as solutions for the equations of motion for the superfluid velocities. We introduce an additional variable, the fraction of free vortices, and test different prescriptions for its advection with the superfluid flow. We find that the new terms lead to solutions with a linear component in the rise of a glitch, and that, in specific setups, they can give rise to glitch precursors and even to decreases in frequency, or ‘anti-glitches’.

We detail tentative detections of low-frequency carbon radio recombination lines from within the Orion molecular cloud complex observed at 99–129 MHz. These tentative detections include one alpha transition and one beta transition over three locations and are located within the diffuse regions of dust observed in the infrared at 100 μm, the Hα emission detected in the optical, and the synchrotron radiation observed in the radio. With these observations, we are able to study the radiation mechanism transition from collisionally pumped to radiatively pumped within the H ii regions within the Orion molecular cloud complex.

Astrophysical measurements regarding compact stars are just ahead of a big evolution jump, since the NICER experiment deployed on ISS on 2017 June 14. This will provide soon data that would enable the determination of compact star radius with less than 10% error. This can be further constrained by the new observation of gravitational waves originated from merging neutron stars, GW170817. This poses new challenges to nuclear models aiming to explain the structure of super dense nuclear matter found in neutron stars. Detailed studies of the QCD phase diagram show the importance of bosonic quantum fluctuations in the cold dense matter equation of state. Here we used a demonstrative model with one bosonic and one fermionic degree of freedom coupled by Yukawa coupling, we show the effect of bosonic quantum fluctuations on compact star observables such as mass, radius, and compactness. We have also calculated the difference in the value of compressibility which is caused by quantum fluctuations. The above-mentioned quantities are calculated in the mean field, one-loop, and in high order many loop approximation. The results show that the magnitude of these effects is in the range of 4–5%, which place it into the region where modern measurements may detect it. This forms a base for further investigations that how these results carry over to more complicated models.

Surface abundance observations of halo stars hint at the occurrence of r-process nucleosynthesis at low metallicity ([Fe/H] < -3), possibly within the first 108 yr after the formation of the first stars. Possible loci of early-Universe r-process nucleosynthesis are the ejecta of either black hole–neutron star or neutron star–neutron star binary mergers. Here, we study the effect of the inclination–eccentricity oscillations raised by a tertiary (e.g. a star) on the coalescence time-scale of the inner compact object binaries. Our results are highly sensitive to the assumed initial distribution of the inner binary semi-major axes. Distributions with mostly wide compact object binaries are most affected by the third object, resulting in a strong increase (by more than a factor of 2) in the fraction of fast coalescences. If instead the distribution preferentially populates very close compact binaries, general relativistic precession prevents the third body from increasing the inner binary eccentricity to very high values. In this last case, the fraction of coalescing binaries is increased much less by tertiaries, but the fraction of binaries that would coalesce within 108 yr even without a third object is already high. Our results provide additional support to the compact-binary merger scenario for r-process nucleosynthesis.

The recent observations in the high energy γ-ray band show that the extragalactic γ-ray sky is dominated by the emission from blazars. However, γ-ray emission from other types of AGNs, e.g., radiogalaxies, also have been detected. These sources were not considered as favored GeV emitters because the nonthermal emission from their jets is less Doppler boosted. Now, the γ-ray emission from more than 25 non-blazar AGNs has been already detected which opened a new window to have an insight into the particle acceleration and emission processes in different components of AGNs. Here, I will present the γ-ray variability of two well-known radiogalaxies, NGC 1275 and 3C 120, which show a rapid flux increase in the γ-ray band.

We present deep low radio frequency (230-470 MHz) observations from the Karl G. Jansky Very Large Array of the Perseus cluster, probing the non-thermal emission from the old particle population of the AGN outflows. Our observations of this nearby relaxed cool core cluster have revealed a multitude of new structures associated with the mini-halo, extending to hundreds of kpc in size. Its irregular morphology seems to have been influenced both by the AGN activity and by the sloshing motion of the cluster’ gas. In addition, it has a filamentary structure similar to that seen in radio relics found in merging clusters. These results illustrate the high-quality images that can be obtained with the new JVLA at low radio-frequencies.

We re-analyzed OJ287 in 120 Very Long Baseline Array (VLBA, MOJAVE) observations (at 15 GHz) covering the time span between Apr. 1995 and Apr. 2017. We find that the radio jet motion over the sky is consistent with a precessing and nutating jet source. The variability of the radio flux-density can be explained by Doppler beaming due to a change in the viewing angle. We suggest that part of the optical emission is due to synchrotron emission related to the jet radiation. We find a strikingly similar scaling for the timescales for precession and nutation as indicated for SS433 with a factor of roughly 50 times longer in OJ287.

An abundance of information about the magnetic (B) fields of relativistic AGN jets has been obtained through radio polarization observations made on a wide range of scales, from the parsec scales probed by Very Long Baseline Interferometry to the kiloparsec scales probed by instruments such as the the Jansky Very Large Array and e-MERLIN. The observed radio emission is synchrotron radiation, for which the linear polarization angles in optically thin regions is orthogonal to the local synchrotron B fields. The characteristic B field structures observed for these jets on parsec scales are described. A key question is whether B field structures observed in particular AGN jets come about primarily due to “global” effects such as the intrinsic B field of the jet itself, which is expected to be helical, or local phenomena such as shocks, shear and bending of the jets. Observational criteria that can be used to try to distinguish between various possible origins for observed B field structures are described. There is now considerable evidence that the relativistic jets of AGNs do indeed carry helical B fields, with the observed polarization also sometimes appreciably influenced by local effects. Patterns seen in the helical B field components, indicated for example by Faraday rotation observations, provide unique information about the processes involved in the generation of these helical B fields. The collected observations on parsec and kiloparsec scales provide weighty evidence that an important role is played by the action of a cosmic “battery” that acts to generate an inward current along the jet axis and an outward current in a more extended region surrounding the jet.

NGC 1275 is one of the best targets to study the high energy emission mechanism in radio galaxies and the accretion flow properties using a young re-started jet 3C 84 as a prober of subpc-to-pc scale environment. In this proceeding, we review the observation results from a series of our VLBI observations and discuss on the origin of gamma-ray emission and accretion flow properties. We also briefly present the preliminary results from our recent ALMA observations.

As revealed by the Fermi-LAT, blazars represent the dominant population of γ-ray emitters. An essential step for understanding blazar physics and the emission mechanisms is the investigation of a possible connection between the observed low- and high-energy emission. A number of works report on the existence of a significant correlation between radio emission and 0.1-100 GeV γ rays. How does this correlation evolve when very high energy (VHE, E > 0.1 TeV) γ rays are considered? The possible radio-VHE emission connection is still elusive mainly because of the lack of a homogeneous VHE sky coverage. In this work we explore the connection between the parsec-scale radio emission and GeV-TeV γ rays by using two unbiased blazar samples extracted from the 1FHL ( E > 10 GeV) and 2FHL (E > 50 GeV) Fermi catalogs. For comparison, we perform the same analysis by using the 3FGL 0.1-300 GeV γ-ray energy flux. Overall, we find out that there is no significant connection between radio and γ-ray emission above 10 GeV for all the blazar sub-classes with the exception of high synchrotron peaked objects. Conversely, when 0.1-300 GeV γ-ray energies are considered, a strong and significant correlation is found for all of the blazar sub-classes. We interpret these results within the context of the blazar spectral energy distribution properties.

Globular clusters (GCs) — compact and massive star clusters found ubiquitously around galaxies — are believed to be ancient relics (ages ≳ 10 Gyr) from the early formative phase of galaxies, although their physical origin remains widely debated. The most numerous GC populations are hosted by giant elliptical galaxies, where they can exhibit a broad dispersion in colour interpreted as a wide spread in metallicity. Here, we show that many thousands of similarly compact and massive super star clusters have formed at an approximately steady rate over, at least, the past ~1 Gyr around the nearby giant elliptical galaxy, NGC 1275, at the centre of the Perseus cluster. The number distribution of these young star clusters appears to exhibit a similar dependence in luminosity and mass as the even more numerous but older GCs around NGC 1275. In just a few Gyr, these super star clusters will evolve to become indistinguishable in broadband optical colours from the older GCs, and their spread in age add to the dispersion in colour of these GCs. The spatial distribution of the super star clusters resembles the filamentary network of multiphase gas in the cluster core, implying that they formed from molecular gas amassed from cooling of the hot intracluster gas. The sustained formation of super star clusters from cooled intracluster gas constitutes a previously unrecognised but prodigious source of GCs over cosmic timescales, and contributes to both their enormous numbers and broad colour dispersion in giant elliptical galaxies.

Supernovae and astrophysical jets are two of the most energetic and intriguing objects in the universe. We examine an interesting scenario that involves the interaction of these two extreme phenomena, motivated by observations of the W50-SS433 system: a jet launched from the microquasar SS433 (an X-ray binary) located inside a supernova remnant, W50. These observations revealed a unique morphology of the remnant, attributed to the presence of the jet. We performed full 3D relativistic hydrodynamic simulations to better capture the interaction between the remnant and the jet and post-processed the data with a radiative transfer code to create emission maps.

Galaxy clusters are excellent targets for high energy astrophysics with gamma rays. Not only they may host active galaxies, but they are often expected to provide signatures of accelerations of electrons and protons to PeV energies. Furthermore, according to ΛCDM scenario, they should be embedded in an extremely massive dark matter halo, the largest halo expected. In this report, we summarize the recently published MAGIC lower limits on the decaying dark matter lifetime using 202 h of selected high quality data taken on the Perseus galaxy cluster, in a 5-year long campaign.

We have conducted VLBI monitoring observations for a radio galaxy 3C 84 to investigate how the pc scale jet structure changes over a long period. VERA, a VLBI observation network in Japan, was used for the observation. The C3 component of the jet has continuously moved toward the south from the core. The motion was, however, not straight, but it showed a bending of about 0.3 mas (0.1 pc) with a time scale of 500-1000 days. Two models explaining the bending, local brightness distribution change or real change of the jet traveling direction, are discussed.

NGC 1275 has been known as a ppint-like X-ray source with a continuum and a Fe-K line. Unlike radio and GeV/TeV gamma-ray emissions, origin of X-ray emission is not yet understood; is it a jet emission like blazars or an accretion corona emission like Seyfert galaxies. X-ray emission is important to determine the SED of jet emission to constrain jet parameters and also understand the relation between accretion and jet. Here we report a recent X-ray probing of NGC 1275 nuclear region with Hitomi/SXS, Swift/XRT, and Suzaku/XIS. Hitomi/SXS gave the first opportunity to measure a Fe-K line of AGNs with several eV resolution. The line center is consistent with the neutral iron emission, and the width is constrained to be 500-1600 km/s (FWHM). This ruled out the origin of broad line region and inner accretion disk. A low-covering-fraction molecular torus or a rotating molecular disk around pc scales, illuminated by accretion corona emission, is suggested as a possible origin. For the continuum emission, Suzaku/XIS monitor observations revealed that the X-ray flux has gradually increased as the GeV gamma-ray flux. Swift/XRT showed a several-days flux increase, associated with the GeV gamma-ray flare. These results on the continuum emission suggests a contribution of jet emission to the X-ray emission. Based on the combined results of Fe-K line and continuum, we discuss some scenarios for X-ray emitting region.

Relativistic jets are one of the most powerful manifestations of the release of energy produced around supermassive black holes at the centre of active galactic nuclei (AGN). Their emission is observed across the entire electromagnetic spectrum, from the radio band to gamma rays. Despite decades of efforts, many aspects of the physics of relativistic jets remain elusive. In particular, the location and the mechanisms responsible for the high-energy emission and the connection of the variability at different wavelengths are among the greatest challenges in the study of AGN. Recent high resolution radio observations of flaring objects locate the high energy emitting region downstream the jet at parsec scale distance from the central engine. Furthermore, monitoring campaigns of the most active blazars indicate that not all the high energy flares have the same characteristics in the various energy bands, even from the same source, making the interpretation of the mechanism responsible for the high-energy emission not trivial. Here I will discuss gamma-ray properties of blazars obtained by Fermi Large Area Telescope observations and the connection between radio and high-energy emission in relativistic jets, and I will focus on the importance of high angular resolution observations.

M87, in the Virgo cluster, allows us to study the interaction of a supermassive black hole (SMBH) with its hot gaseous atmosphere. Deep Chandra observations reveal a nearly circular shock front with a Mach number of 1.2 and a radius of 13 kpc which is driven by a central cavity inflated by an SMBH outburst began 12 million years ago. An outburst with an energy of a ~5×57 ergs and a duration of ~2 Myrs provides a good match to all the constraints. For an outburst repetition rate of about 12 Myrs (the outburst age), the outburst energy is sufficient to balance the radiative cooling of the gas. The outburst duration in M87 argues for a “gentle” (long duration) outburst that does not generate strong shocks and where much of the outburst energy is deposited in the cavities that then transfer energy to the surrounding gas as they buoyantly rise.

We present a method that uses photoionization codes (CLOUDY) to estimate the supermassive black hole masses (MBH) for quasars at low and high redshift. This method is based on the determination of the physical conditions of the broad line region (BLR) using observational diagnostic diagrams from line ratios in the UV. We also considered that the density and metallicity of the BLR in quasars at high z could be different from those at the nearby Universe. The computed black hole masses obtained using this method are in agreement with those derived from the method of reverberation mapping.

Recent molecular line observations with ALMA and NOEMA in several Brightest Cluster Galaxies (BCG) have revealed the large-scale filamentary structure at the center of cool core clusters. These filaments extend over 20-100kpc, they are tightly correlated with ionized gas (Hα, [NII]) emission, and have characteristic shapes: either radial and straight, or also showing a U-turn, like a horse-shoe structure. The kinematics is quite regular and laminar, and the derived infall time is much longer than the free-fall time. The filaments extend up to the radius where the cooling time becomes larger than the infall time. Filaments can be perturbed by the sloshing of the BCG in its cluster, and spectacular cooling wakes have been observed. Filaments tend to occur at the border of cavities driven in the X-ray gas by the AGN radio jets. Observations of cool core clusters support the thermal instability scenario, which accounts for the multiphase medium in the upper atmospheres of BCG, where the right balance between heating and cooling is reached, and a chaotic cold gas accretion occurs. Molecular filaments are also seen associated to ram-pressure stripped spiral galaxies in rich galaxy clusters, and in jet-induced star formation, suggesting a very efficient molecular cloud formation even in hostile cluster environments.

The international collaboration of VLBI in East Asia (EA) is rapidly growing. Besides the recent successful operation of the KVN and VERA Array (KaVA), the effort of joint VLBI operation in EA is being expanded into China. This forms the East Asian VLBI Network (EAVN), which offers detailed imaging and monitoring of the innermost regions of relativistic jets at cm wavelengths and thus complementary to the Event Horizon Telescope operated at mm wavelengths. In this contribution we present some of the ongoing KaVA/EAVN studies for the inner jets of the two important nearby radio galaxies 3C84 and M87. The observations have revealed detailed kinematics for the parsec-to-subparsec-scale structures of these jets. Future regular observations with the East-Asia-To-Italy-Nearly-Global (EATING) VLBI, a joint effort between EAVN and the Italian VLBI Network, will enable us to resolve and regularly monitor the innermost regions of nearby AGN jets at tens of micro-arcsecond scales.