ABSTRACT We report on the radio brightening of the blazar TXS 0506+056 (at z = 0.3365), and we support its identification by the IceCube Neutrino Observatory as a source of the high-energy (HE) ...neutrino IC-170922A. Data from the Monitoring Of Jets in AGN with VLBA Experiments (MOJAVE)/Very Long Baseline Array (VLBA) survey indicate that its radio brightness has abruptly increased since 2016 January. When decomposing the total radio flux density curve (in the period 2008 January to 2018 July), provided by the Owens Valley Radio Observatory, into eight Gaussian flares, the peak time of the largest flare overlaps with the HE neutrino detection, while the total flux density has exhibited a threefold increase since 2016 January. We reveal the radio structure of TXS 0506+056 by analysing very long baseline interferometry (VLBI) data from the MOJAVE/VLBA survey. The jet components maintain quasi-stationary core separations. The structure of the ridge line is indicative of a jet curve in the region 0.5–2 mas (2.5–9.9 pc projected) from the VLBI core. The brightness temperature of the core and the pc-scale radio morphology support a helical jet structure at small inclination angle (<8${^{\circ}_{.}}$2). The jet pointing towards the Earth is a key property facilitating multimessenger observations (HE neutrinos, γ-rays and radio flares). The radio brightening preceding the detection of a HE neutrino is similar to the one reported for the blazar PKS 0723–008 and IceCube event ID5.
Abstract
A steady-state, semi-analytical model of energetic particle acceleration in radio-jet shear flows due to cosmic-ray viscosity obtained by Webb et al. is generalized to take into account more ...general cosmic-ray boundary spectra. This involves solving a mixed Dirichlet–Von Neumann boundary value problem at the edge of the jet. The energetic particle distribution function
f
0
(
r
,
p
) at cylindrical radius
r
from the jet axis (assumed to lie along the
z
-axis) is given by convolving the particle momentum spectrum
f
0
(
∞
,
p
′
)
with the Green’s function
G
(
r
,
p
;
p
′
)
, which describes the monoenergetic spectrum solution in which
f
0
→
δ
(
p
−
p
′
)
as
r
→ ∞ . Previous work by Webb et al. studied only the Green’s function solution for
G
(
r
,
p
;
p
′
)
. In this paper, we explore for the first time, solutions for more general and realistic forms for
f
0
(
∞
,
p
′
)
. The flow velocity
u
=
u
(
r
)
e
z
is along the axis of the jet (the
z
-axis).
u
is independent of
z
, and
u
(
r
) is a monotonic decreasing function of
r
. The scattering time
τ
(
r
,
p
)
=
τ
0
(
p
/
p
0
)
α
in the shear flow region 0 <
r
<
r
2
, and
τ
(
r
,
p
)
=
τ
0
(
p
/
p
0
)
α
(
r
/
r
2
)
s
, where
s
> 0 in the region
r
>
r
2
is outside the jet. Other original aspects of the analysis are (i) the use of cosmic ray flow lines in (
r
,
p
) space to clarify the particle spatial transport and momentum changes and (ii) the determination of the probability distribution
ψ
p
(
r
,
p
;
p
′
)
that particles observed at (
r
,
p
) originated from
r
→ ∞ with momentum
p
′
. The acceleration of ultrahigh-energy cosmic rays in active galactic nuclei jet sources is discussed. Leaky box models for electron acceleration are described.
LOPES, the LOFAR prototype station, was an antenna array for cosmic-ray air showers operating from 2003 to 2013 within the KASCADE-Grande experiment. Meanwhile, the analysis is finished and the data ...of air-shower events measured by LOPES are available with open access in the KASCADE Cosmic Ray Data Center (KCDC). This article intends to provide a summary of the achievements, results, and lessons learned from LOPES. By digital, interferometric beamforming the detection of air showers became possible in the radio-loud environment of the Karlsruhe Institute of Technology (KIT). As a prototype experiment, LOPES tested several antenna types, array configurations and calibration techniques, and pioneered analysis methods for the reconstruction of the most important shower parameters, i.e., the arrival direction, the energy, and mass-dependent observables such as the position of the shower maximum. In addition to a review and update of previously published results, we also present new results based on end-to-end simulations including all known instrumental properties. For this, we applied the detector response to radio signals simulated with the CoREAS extension of CORSIKA, and analyzed them in the same way as measured data. Thus, we were able to study the detector performance more accurately than before, including some previously inaccessible features such as the impact of noise on the interferometric cross-correlation beam. These results led to several improvements, which are documented in this paper and can provide useful input for the design of future cosmic-ray experiments based on the digital radio-detection technique.
Context. The mass function of supermassive black holes in our cosmic neighborhood is required to understand the statistics of their activity and consequently the origin of ultra high energy ...particles. Aims. We determine a mass function of supermassive black hole candidates from the entire sky except for the Galactic plane. Methods. Using the 2MASS catalogue as a starting point, and the well-established correlation between black hole mass and the bulge of old population of stars, we derive a list of nearby black hole candidates within the redshift range z < 0.025, then perform an additional selection based on the Hubble type. We present our resulting catalogue elsewhere. The final list of black hole candidates above a mass of MBH > 3 × 106 $M_{\odot}$ has 5829 entries. We perform a Hubble-type correction to account for selection effects, which reduces this number to 2919 black hole candidates. Here we use this catalogue to derive the black-hole mass function. We also correct for volume, so that this mass function is a volume-limited distribution to redshift 0.025. Results. The differential mass function of nearby black hole candidates is a curved function, with a straight simple power-law of index -3 above 108 $M_{\odot}$ that becomes progressively flatter towards lower masses, turns off towards a gap below 3 × 106 $M_{\odot}$, and then extends into the range where nuclear star clusters replace black holes. The shape of this mass function can be explained in a simple merger picture. Integrating this mass function over the redshift range for which it has been derived, infers a total number of black holes with z < 0.025, and MBH > 107 $M_{\odot}$ of about 2.4 × 104, or, if we average uniformly, 0.6 for every square degree on the sky.
Observations of the FR I radio galaxy Centaurus A in radio, X-ray, and gamma-ray bands provide evidence for lepton acceleration up to several TeV and clues about hadron acceleration to tens of EeV. ...Synthesising the available observational constraints on the physical conditions and particle content in the jets, inner lobes and giant lobes of Centaurus A, we aim to evaluate its feasibility as an ultra-high-energy cosmic-ray source. We apply several methods of determining jet power and affirm the consistency of various power estimates of ~1 × 1043 erg s-1. Employing scaling relations based on previous results for 3C 31, we estimate particle number densities in the jets, encompassing available radio through X-ray observations. Our model is compatible with the jets ingesting ~3 × 1021 g s-1 of matter via external entrainment from hot gas and ~7 × 1022 g s-1 via internal entrainment from jet-contained stars. This leads to an imbalance between the internal lobe pressure available from radiating particles and magnetic field, and our derived external pressure. Based on knowledge of the external environments of other FR I sources, we estimate the thermal pressure in the giant lobes as 1.5 × 10-12 dyn cm-2, from which we deduce a lower limit to the temperature of ~1.6 × 108 K. Using dynamical and buoyancy arguments, we infer ~440−645 Myr and ~560 Myr as the sound-crossing and buoyancy ages of the giant lobes respectively, inconsistent with their spectral ages. We re-investigate the feasibility of particle acceleration via stochastic processes in the lobes, placing new constraints on the energetics and on turbulent input to the lobes. The same “very hot” temperatures that allow self-consistency between the entrainment calculations and the missing pressure also allow stochastic UHECR acceleration models to work.
The statistics of black holes and their masses strongly suggests that their mass distribution has a cut-off towards lower masses near 3 × 106 M⊙. This is consistent with a classical formation ...mechanism from the agglomeration of the first massive stars in the universe. However, when the masses of the stars approach 106 M⊙, the stars become unstable and collapse, possibly forming the first generation of cosmological black holes. Here, we speculate that the claimed detection of an isotropic radio background may constitute evidence of the formation of these first supermassive black holes, since their data are compatible in spectrum and intensity with synchrotron emission from the remnants. The model proposed fulfils all observational conditions for the background, in terms of single-source strength, number of sources, far-infrared and gamma-ray emission. The observed high-energy neutrino flux is consistent with our calculations in flux and spectrum. The proposal described in this paper may also explain the early formation and growth of massive bulge-less disc galaxies as derived from the massive, gaseous shell formed during the explosion prior to the formation of a supermassive black hole.
This study aims to validate the Multiple Sclerosis (MS) International Quality of Life (MusiQoL) questionnaire, a multi-dimensional, self-administered questionnaire, available in 14 languages, as a ...disease-specific quality of life scale that can be applied internationally. A total of 1992 patients with different types and severities of MS from 15 countries were recruited. At baseline and day 21 ± 7, each patient completed the MusiQoL, a symptom checklist and the short-form (SF)-36 QoL questionnaire. Neurologists also collected socio-demographic, MS history and outcome data. The database was randomly divided into two subgroups and analysed according to different patient characteristics. For each model, psychometric properties were tested and the number of items was reduced by various statistical methods. Construct validity, internal consistency, reproducibility and external consistency were also tested. Nine dimensions, explaining 71% of the total variance, were isolated. Internal consistency and reproducibility were satisfactory for all the dimensions. External validity testing revealed that dimension scores correlated significantly with all SF-36 scores, but showed discriminant validity by gender, socio-economic and health status. Significant correlations were found between activity in daily life scores and clinical indices. These results demonstrate the validity and reliability of the MusiQoL as an international scale to evaluate QoL in patients with MS. Multiple Sclerosis 2008; 14: 219—230. http://msj.sagepub.com
The X-ray mission Chandra has observed a dramatic X-ray flare -a brightening by a factor of 50 for only three hours -from Sgr A*, the Galactic Center supermassive black hole. Sgr A* has never shown ...variability of this amplitude in the radio and we therefore argue that a jump of this order in the accretion rate does not seem the likely cause. Based on our model for jet-dominated emission in the quiescent state of Sgr A*, we suggest that the flare is a consequence of extra electron heating near the black hole. This can either lead to direct heating of thermal electrons to $T_{\rm e}\sim6\times 10^{11}$ K and significantly increased synchrotron-self Compton emission, or result from non-thermal particle acceleration with increased synchrotron radiation and electron Lorentz factors up to $\gamma_{\rm e}\ga10^{5}$. While the former scenario is currently favored by the data, simultaneous VLBI, submm, mid-infrared and X-ray observations should ultimately be able to distinguish between the two cases.
Aims.We study the distribution of fermionic dark matter at the center of galaxies using NFW, Moore and isothermal density profiles and show that dark matter becomes degenerate for particle masses of ...a few keV and for distances less than a few parsec from the center of our galaxy. Methods.A compact degenerate core forms after galaxy merging and boosts the growth of supermassive black holes at the center of galaxies. Results.To explain the galactic center black hole of mass of ~3.5 $\times$ $10^{6}~M_{\odot}$ and a supermassive black hole of ~3 $\times$ $10^{9}~M_{\odot}$ at a redshift of 6.41 in SDSS quasars, we require a degenerate core of mass between 3 $\times$ $10^{3}~M_{\odot}$ and 3.5 $\times$ $10^{6}~M_{\odot}$. This constrains the mass of the dark matter particle between $0.6~{\rm keV}$ and $82~{\rm keV}$. The lower limit on the dark matter mass is improved to 7 keV if exact solutions of Poisson's equation are used in the isothermal power law case. We argue that the constrained particle could be the long sought dark matter of the Universe that is interpreted here as a sterile neutrino.
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