Ten milliparsec-scale structure of the nucleus region in Centaurus A

We present the results of a VLBI Space Observatory Programme (VSOP) observation of the subparsec structure in Centaurus A at 4.9 GHz. Owing to its proximity, our Centaurus A space-VLBI image is one of the highest spatial resolution images of an AGN ever made -- 0.01 pc per beam. The elongated core region is resolved into several components over 10 milli-arcseconds long (0.2 pc) including a compact component of brightness temperature 2.2x10^10K. We analyze the jet geometry in terms of collimation. Assuming the strongest component to be the core, the jet opening angle at ~ 5,000 r_s (Schwarzchild radii) from the core is estimated to be ~ 12 degree, with collimation of the jet to ~ 3 degree continuing out to ~ 20,000 r_s. This result is consistent with previous studies of the jet in M87, which favor MHD disk outflow models. Future space VLBI observations at higher frequencies will probably be able to image the collimation region, within 1,000 r_s of the center of Centaurus A, together with the accretion disk itself.Comment: 12 pages, 6 figures, accepted for publication in PASJ, Vol.57 No.6, VSOP special issu

Two-neutron correlations in a Borromean 20C+n+n^{20}{\rm C}+n+n system: Sensitivity of unbound subsystems

The structure of $^{22}$C plays a vital role in the new physics at subshell closure of $N=16$ in the neutron-rich region. We study the two-neutron correlations in the ground state of the weakly-bound Borromean nucleus $^{22}$C sitting at the edge of the neutron-drip line and its sensitivity to ${\rm core}$-$n$ potential. For the present study, we employ a three-body (${\rm core}+n+n$) structure model designed for describing the Borromean system by explicit coupling of unbound continuum states of the subsystem (${\rm core}+n$). We use a density-independent contact-delta interaction to describe the neutron-neutron interaction and its strength is varied to fix the binding energy. Along with the ground-state properties of $^{22}$C, we investigate its electric-dipole and monopole responses, discussing the contribution of various configurations. Our results indicate more configuration mixing as compared to the previous studies in the ground state of $^{22}$C. However, they strongly depend upon the choice of the $^{20}{\rm C}$-$n$ potential as well as the binding energy of $^{22}$C, which call for new precise measurements for the low-lying continuum structure of the binary system ($^{20}{\rm C}+n$) and the mass of $^{22}$C. These measurements will be essential to understand the Borromean three-body system $^{22}$C with more accuracy.Comment: 13 pages, 6 figures, To appear in Few-Body Systems (2019

Three-body Description of 2n2n-Halo and Unbound 2n2n-Systems: 22^{22}C and 26^{26}O

We study the two-neutron correlations in the ground state of the weakly-bound two-neutron halo nucleus $^{22}$C sitting at the edge of the neutron-drip line and also in the unbound nucleus $^{26}$O sitting beyond the neutron dripline. For the present study, we employ a three-body (core$+n+n$) structure model designed for describing the two-neutron halo system by explicit inclusion of unbound continuum states of the subsystem (core$+n$). We use either a density-independent or a density-dependent contact-delta interaction to describe the neutron-neutron interaction and its strength is varied to fix the binding energy. We report the configuration mixing in the ground state of these systems for different choices of pairing interactions.Comment: 4 Pages, 1 Figure, 2 Tables. 13th International Conference on Nucleus-Nucleus Collisions (NN2018

Proton inelastic scattering to continuum studied with antisymmetrized molecular dynamics

Intermediate energy (p,p$'$x) reaction is studied with antisymmetrized molecular dynamics (AMD) in the cases of $^{58}$Ni target with $E_p = 120$ MeV and $^{12}$C target with $E_p =$ 200 and 90 MeV. Angular distributions for various $E_{p'}$ energies are shown to be reproduced well without any adjustable parameter, which shows the reliability and usefulness of AMD in describing light-ion reactions. Detailed analyses of the calculations are made in the case of $^{58}$Ni target and following results are obtained: Two-step contributions are found to be dominant in some large angle region and to be indispensable for the reproduction of data. Furthermore the reproduction of data in the large angle region \theta \agt 120^\circ for $E_{p'}$ = 100 MeV is shown to be due to three-step contributions. Angular distributions for E_{p'} \agt 40 MeV are found to be insensitive to the choice of different in-medium nucleon-nucleon cross sections $\sigma_{NN}$ and the reason of this insensitivity is discussed in detail. On the other hand, the total reaction cross section and the cross section of evaporated protons are found to be sensitive to $\sigma_{NN}$. In the course of the analyses of the calculations, comparison is made with the distorted wave approach.Comment: 16 pages, 7 Postscript figure

Electric dipole response of low-lying excitations in the two-neutron halo nucleus 29\boldsymbol{^{29}}F

The neutron-rich $^{28,29}$F isotopes have been recently studied via knockout and interaction cross-section measurements. The $2n$ halo in $^{29}$F has been linked to the occupancy of $pf$ intruder configurations. We investigate bound and continuum states in $^{29}$F, focusing on the $E1$ response of low-lying excitations and the effect of dipole couplings on nuclear reactions. $^{29}\text{F}$ ($^{27}\text{F}+n+n$) wave functions are built within the hyperspherical harmonics formalism, and reaction cross sections are calculated using the Glauber theory. Continuum states and $B(E1)$ transition probabilities are described in a pseudostate approach using the analytical THO basis. The corresponding structure form factors are used in CDCC calculations to describe low-energy scattering. Parity inversion in $^{28}$F leads to a $^{29}$F ground state characterized by 57.5% of $(p_{3/2})^2$ intruder components, a strong dineutron configuration, and an increase of the matter radius with respect to the core radius of $\Delta R=0.20$ fm. Glauber-model calculations for a carbon target at 240 MeV/nucleon provide a total reaction cross section of 1370 mb, in agreement with recent data. The model produces also a barely bound excited state corresponding to a quadrupole excitation. $B(E1)$ calculations into the continuum yield a total strength of 1.59 e$^2$fm$^2$ up to 6 MeV, and the $E1$ distribution exhibits a resonance at $\approx$ 0.85 MeV. Results using a standard shell-model order for $^{28}$F lead to a considerable reduction of the $B(E1)$ distribution. The four-body CDCC calculations for $^{29}\text{F}+^{120}\text{Sn}$ around the Coulomb barrier are dominated by dipole couplings, which totally cancel the Fresnel peak in the elastic cross section. These results are consistent with a two-neutron halo and may guide future experimental campaigns.Comment: 17 pages, 15 figures. Accepted in Physical Review

The 29F nucleus as a lighthouse on the coast of the island of inversion

The exotic, neutron-rich and weakly-bound isotope 29F stands out as a waymarker on the southern shore of the island of inversion, a portion of the nuclear chart where the effects of nuclear forces lead to a reshuffling of the single particle levels and to a reorganization of the nuclear structure far from stability. This nucleus has become very popular, as new measurements allow to refine theoretical models. We review the latest developments and suggest how to further assess the structure by proposing predictions on electromagnetic transitions that new experiments of Relativistic Coulomb Excitation should soon become able to measure

Is it time to reappraise blood pressure thresholds and targets? Statement from the international society of hypertension - a global perspective

No abstract available

Characterizing the transition from diffuse atomic to dense molecular clouds in the Magellanic clouds with [CII], [CI], and CO

We present and analyze deep Herschel/HIFI observations of the [CII] 158um, [CI] 609um, and [CI] 370um lines towards 54 lines-of-sight (LOS) in the Large and Small Magellanic clouds. These observations are used to determine the physical conditions of the line--emitting gas, which we use to study the transition from atomic to molecular gas and from C^+ to C^0 to CO in their low metallicity environments. We trace gas with molecular fractions in the range 0.1<f(H2)<1, between those in the diffuse H2 gas detected by UV absorption (f(H2)<0.2) and well shielded regions in which hydrogen is essentially completely molecular. The C^0 and CO column densities are only measurable in regions with molecular fractions f(H2)>0.45 in both the LMC and SMC. Ionized carbon is the dominant gas-phase form of this element that is associated with molecular gas, with C^0 and CO representing a small fraction, implying that most (89% in the LMC and 77% in the SMC) of the molecular gas in our sample is CO-dark H2. The mean X_CO conversion factors in our LMC and SMC sample are larger than the value typically found in the Milky Way. When applying a correction based on the filling factor of the CO emission, we find that the values of X_CO in the LMC and SMC are closer to that in the Milky Way. The observed [CII] intensity in our sample represents about 1% of the total far-infrared intensity from the LOSs observed in both Magellanic Clouds.Comment: 32 pages, 21 figures, Accepted to Ap

4,4′-Imino­dipyridinium bis­(hydrogen phthalate)

In the title salt, C10H11N3 2+·2C8H5O4 −, doubly protonated 4,4′-dipyridylamine (dpa) cations participate in N—H⋯O hydrogen bonding with two hydrogen phthalate anions to form a neutral unit. Both anions contain an intramolecular O—H⋯O hydrogen bond. In the crystal structure, these units form two-dimensional layers through π–π stacking inter­actions with a centroid-to-centroid distance of 3.763 (3) Å. In turn, these layers aggregate in three dimensions by additional N—H⋯O hydrogen bonding. The assignment to the noncentrosymmetric space group P1 is corroborated by chemically unreasonable aromatic ring bond distances and poor K scale factor distributions for a disordered model in the centrosymmetric P space group