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The extreme, intra-hour and > 10% rms flux density scintillation observed in AGNs such as PKS 0405-385, J1819+3845 and PKS 1257-326 at cm wavelengths has been attributed to scattering in highly turbulent, nearby regions in the interstellar…

Astrophysics of Galaxies · Physics 2011-09-22 J. Y. Koay , H. E. Bignall , J. -P. Macquart , D. L. Jauncey , B. J. Rickett , J. E. J. Lovell

The Milky Way's satellite galaxies and Globular Clusters (GCs) are known to exhibit an anisotropic spatial distribution. We examine in detail this anisotropy by the means of the inertia tensor. We estimate the statistical significance of…

Astrophysics of Galaxies · Physics 2018-08-29 N. R. Arakelyan , S. V. Pilipenko , N. I. Libeskind

We have measured the scatter broadening of pulsars in the direction of the Gum nebula. For the first time, our observations show clear variations of scattering properties across the Gum nebula. The IRAS-Vela shell is shown to be a high…

Astrophysics · Physics 2009-11-06 D. Mitra , R. Ramachandran

We report the discovery of nineteen new HI shells in the Southern Galactic Plane Survey (SGPS). These shells, which range in radius from 40 pc to 1 kpc, were found in the low resolution Parkes portion of the SGPS dataset, covering Galactic…

Astrophysics · Physics 2009-11-07 N. M. McClure-Griffiths , John M. Dickey , B. M. Gaensler , A. J. Green

The Parkes 20 cm Multibeam pulsar surveys have discovered nearly half of the known pulsars and revealed many distant pulsars with high dispersion measures. Using a sample of 1,301 pulsars from these surveys, we have explored the spatial…

High Energy Astrophysical Phenomena · Physics 2024-02-23 J. T. Xie , J. B. Wang , N. Wang , R. Manchester , G. Hobbs

Using three dimensional Monte Carlo radiation transfer models of photoionisation and dust scattering, we explore different components of the widespread diffuse H$\alpha$ emission observed in the interstellar medium of the Milky Way and…

Astrophysics of Galaxies · Physics 2015-06-23 Joanna E. Barnes , Kenneth Wood , Alex S. Hill , L. Matthew Haffner

Scintillation arcs have become a powerful tool for exploring scattering in the ionized interstellar medium. There is accumulating evidence that the scattering from many pulsars is extremely anisotropic resulting in highly elongated, linear…

Astrophysics of Galaxies · Physics 2019-01-11 Dan R. Stinebring , Barney J. Rickett , Stella Koch Ocker

Pulsar scintillation observations have revealed ubiquitous discrete scintillation screens in the interstellar medium. A major obstacle in identifying the nature of these screens is the uncertainty in their distances, which prevents precise…

Astrophysics of Galaxies · Physics 2026-01-26 Yuanshang Huang , Xun Shi , Jumei Yao , Weiwei Zhu , Yonghua Xu

We analyze Hubble Space Telescope observations of scattering regions in 20 luminous obscured quasars at $0.24<z<0.65$ (11 new observations and 9 archival ones) observed at rest-frame $\sim 3000$\AA. We find spectacular $5-10$ kpc-scale…

Astrophysics of Galaxies · Physics 2016-01-27 Georges Obied , Nadia L. Zakamska , Dominika Wylezalek , Guilin Liu

Continuum low-frequency radio observations of the Galactic Center reveal the presence of two prominent radio sources, Sgr A East and its surrounding Halo, containing non-thermal particle distributions with power-law indices around 2.5-3.3…

Astrophysics · Physics 2009-10-30 Fulvio Melia , Farhad Yusef-Zadeh , Marco Fatuzzo

Extended gamma-ray emission, interpreted as halos formed by the inverse-Compton scattering of ambient photons by electron-positron pairs, is observed toward a number of middle-aged pulsars. The physical origin and actual commonness of the…

High Energy Astrophysical Phenomena · Physics 2022-09-21 Pierrick Martin , Alexandre Marcowith , Luigi Tibaldo

Sr I 4607\AA spectral line shows one of the strongest scattering polarization signals in the visible solar spectrum. The amplitudes of these signals are expected to vary at granular spatial scales. This variation can be due to changes in…

We present a catalog of 9017 X-ray sources identified in Chandra observations of a 2 by 0.8 degree field around the Galactic center. We increase the number of known X-ray sources in the region by a factor of 2.5. The catalog incorporates…

The magneto-ionic structures of the interstellar medium of the Milky Way and the intergalactic medium are still poorly understood, especially at distances larger than a few kiloparsecs from the Sun. The three-dimensional (3D) structure of…

We examine the spectrum of diffuse emission detected in the 17' by 17' field around Sgr A* during 625 ks of Chandra observations. The spectrum exhibits He-like and H-like lines from Si, S, Ar, Ca, and Fe, that are consistent with…

In galaxy clusters, hierarchical assembly predicts the formation of stellar substructures and intracluster light (ICL), a diffuse stellar component tracing the global cluster potential. Because these features are extremely faint,…

We examine the nHz gravitational wave (GW) foreground of stars and black holes (BHs) orbiting SgrA* in the Galactic Center. A cusp of stars and BHs generates a continuous GW spectrum below 40 nHz; individual BHs within 1 mpc to SgrA* stick…

Astrophysics of Galaxies · Physics 2015-05-30 Bence Kocsis , Alak Ray , Simon Portegies Zwart

Using the JVLA, we explored the Galactic center (GC) with a resolution of 0.05" at 33.0 and 44.6 GHz. We detected 64 hyper-compact radio sources (HCRs) in the central parsec. The dense group of HCRs can be divided into three spectral types:…

Astrophysics of Galaxies · Physics 2022-03-09 Jun-Hui Zhao , Mark R. Morris , W. M. Goss

Pulsars in the Galactic Center (GC) are important probes of General Relativity, star formation, stellar dynamics, stellar evolution, and the interstellar medium. Despite years of searching, only a handful of pulsars in the central 0.5 deg…

The parabolic arc phenomenon visible in the Fourier analysis of the scintillation spectra of pulsars provides a new method of investigating the small scale structure in the ionized interstellar medium (ISM). We report archival observations…

Astrophysics · Physics 2011-02-11 Frank S. Trang , Barney J. Rickett