S. Colafrancesco
A5047793211- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Gamma-ray bursts and supernovae
- Dark Matter and Cosmic Phenomena
- Radio Astronomy Observations and Technology
- Astrophysical Phenomena and Observations
- Astronomy and Astrophysical Research
- Cosmology and Gravitation Theories
- Particle Detector Development and Performance
- Stellar, planetary, and galactic studies
- Pulsars and Gravitational Waves Research
- Astrophysics and Star Formation Studies
- Neutrino Physics Research
- Particle Accelerators and Free-Electron Lasers
- Astronomical Observations and Instrumentation
- Scientific Research and Discoveries
- Solar and Space Plasma Dynamics
- Geophysics and Gravity Measurements
- Particle physics theoretical and experimental studies
- History and Developments in Astronomy
- Superconducting and THz Device Technology
- Nuclear Physics and Applications
- Atomic and Subatomic Physics Research
- Relativity and Gravitational Theory
- Atomic and Molecular Physics
University of the Witwatersrand
2012-2021
National Institute for Astrophysics
2004-2019
South African Radio Astronomy Observatory
2019
Astronomical Observatory of Rome
2007-2018
Clark Atlanta University
2018
University of Alaska Anchorage
2018
Providence College
2018
Southern University and Agricultural and Mechanical College
2018
The University of Adelaide
2018
The University of Texas at Arlington
2018
(Abridged) We have conducted a detailed investigation of the broad-band spectral properties \gamma-ray selected blazars Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated gamma-ray spectra with Swift, radio, infra-red, optical and other hard X-ray/gamma-ray data, collected within three months LBAS data taking period, we were able to assemble high-quality quasi-simultaneous Spectral Energy Distributions (SED) for 48 blazars.The SED these sources is similar that...
We present in this paper new and updated calculations of the ionization equilibrium for all elements from H to Ni. collected these data available literature radiative plus dielectronic recombination rates. In particular, rates have been fitted with a single formula related coefficients are tabulated. Our results compared previous works.
The first three months of sky-survey operation with the Fermi Gamma Ray Space Telescope (Fermi) Large Area (LAT) reveals 132 bright sources at |b|>10 deg test statistic greater than 100 (corresponding to about 10 sigma). Two methods, based on CGRaBS, CRATES and BZCat catalogs, indicate high-confidence associations 106 these known AGNs. This sample is referred as LAT Bright AGN Sample (LBAS). It contains two radio galaxies, namely Centaurus A NGC 1275, 104 blazars consisting 57 flat...
We present the first all-sky sample of galaxy clusters detected blindly by Planck satellite through Sunyaev-Zeldovich (SZ) effect from its six highest frequencies. This early SZ (ESZ) is comprised 189 candidates, which have a high signal-to-noise ratio ranging 6 to 29. Its reliability (purity above 95%) further ensured an extensive validation process based on internal quality assessments and external cross-identification follow-up observations. provides measured signal for about 80% 169...
The inner region of the Milky Way halo harbors a large amount dark matter (DM). Given its proximity, it is one most promising targets to look for DM. We report on search annihilations DM particles using γ-ray observations towards 300 pc Way, with H.E.S.S. array ground-based Cherenkov telescopes. analysis based 2D maximum likelihood method Galactic Center (GC) data accumulated by over last 10 years (2004-2014), and does not show any significant signal above background. Assuming Einasto...
Taking advantage of the all-sky coverage and broadfrequency range Planck satellite, we study Sunyaev-Zeldovich (SZ) pressure profiles 62 nearby massive clusters detected at high significance in 14-month nominal survey. Careful reconstruction SZ signal indicates that most are individually least out to R500. By stacking radial profiles, have statistically 3 × R500, i.e., a density contrast about 50–100, though dispersion mean profile dominates statistical errors across whole range. Our...
Gamma-ray line signatures can be expected in the very-high-energy (${E}_{\ensuremath{\gamma}}>100\text{ }\text{ }\mathrm{GeV}$) domain due to self-annihilation or decay of dark matter (DM) particles space. Such a signal would readily distinguishable from astrophysical $\ensuremath{\gamma}$-ray sources that most cases produce continuous spectra span over several orders magnitude energy. Using data collected with H.E.S.S. instrument, upper limits on linelike emission are obtained energy range...
PRISM (Polarized Radiation Imaging and Spectroscopy Mission) was proposed to ESA in May 2013 as a large-class mission for investigating within the framework of Cosmic Vision program set important scientific questions that require high resolution, sensitivity, full-sky observations sky emission at wavelengths ranging from millimeter-wave far-infrared. PRISM's main objective is explore distant universe, probing cosmic history very early times until now well structures, distribution matter,...
The long gamma-ray burst (GRB) 100621A, at the time brightest X-ray transient ever detected by Swift-XRT in $0.3\textrm{--}10$ keV range, has been observed with H.E.S.S. imaging air Cherenkov telescope array, sensitive to gamma radiation very-high-energy (VHE, $>100$ GeV) regime. Due its relatively small redshift of $z\sim0.5$, favourable position southern sky and short follow-up ($<700 \rm{s}$ after satellite trigger) observations, this GRB could be within sensitivity reach instrument....
We study the astrophysical implications of neutralino dark matter annihilations in galaxy clusters, with a specific application to Coma cluster. first address determination halo models for Coma, starting from structure formation and observational data, we discuss detail role sub-halos. then perform thorough analysis transport diffusion properties annihilation products, investigate resulting multi-frequency signals, radio gamma-ray frequencies. also other relevant effects annihilations, like...
The Fermi Gamma-ray Space Telescope has detected the gamma-ray glow emanating from giant radio lobes of galaxy Centaurus A. resolved image shows clearly separated central active source. In contrast to all other galaxies so far in high-energy gamma-rays, lobe flux constitutes a considerable portion (>1/2) total source emission. emission is interpreted as inverse Compton scattered relic radiation cosmic microwave background (CMB), with additional contribution at higher energies...
We report the discovery of high-energy (E>100 MeV) gamma-ray emission from NGC 1275, a giant elliptical galaxy lying at center Perseus cluster galaxies, based on observations made with Large Area Telescope (LAT) Fermi Gamma ray Space Telescope. The positional source is only ~3' away 1275 nucleus, well within 95% LAT error circle ~5'.The spatial distribution photons consistent point source. average flux and power-law photon index measured 2008 August 4 to December 5 are F_gamma =...
We present precise Sunyaev-Zeldovich (SZ) effect measurements in the direction of 62 nearby galaxy clusters (z <0.5) detected at high signal-to-noise first Planck all-sky dataset. The sample spans approximately a decade total mass, 10^14 < M_500 10^15, where is mass corresponding to density contrast 500. Combining these quality with deep XMM-Newton X-ray data, we investigate relations between D_A^2 Y_500, integrated Compton parameter due SZ effect, and X-ray-derived gas M_g,500, temperature...
We report the Fermi Large Area Telescope (LAT) discovery of high-energy (MeV/GeV) γ-ray emission positionally consistent with center radio galaxy M87, at a source significance over 10σ in 10 months all-sky survey data. Following detections Cen A and Per A, this makes M87 third seen LAT. The faint point-like has >100 MeV flux 2.45 (±0.63) × 10−8 photons cm−2 s−1 (photon index = 2.26 ± 0.13) no significant variability detected within LAT observation. This is comparable previous EGRET upper...
The nine-year H.E.S.S. Galactic Plane Survey (HGPS) yielded the most uniform observation scan of inner Milky Way in TeV gamma-ray band to date. sky maps and source catalogue HGPS allow for a systematic study population pulsar wind nebulae found throughout last decade. To investigate nature evolution nebulae, first time we also present several upper limits regions around pulsars without detected nebula. Our data exhibit correlation surface brightness with spin-down power $\dot{E}$. This seems...
Analysis is presented for 15 months of data taken with the Large Area Telescope (LAT) on Fermi Gamma-ray Space 11 non-blazar active galactic nuclei (AGNs), including seven FRI radio galaxies and four FRII sources consisting two steep spectrum quasars. The broad line galaxy 3C 120 reported here as a γ-ray source first time. analysis based directional associations LAT in 3CR, 3CRR, MS4 (collectively referred to 3C-MS) catalogs. Seven eleven associated 3C-MS have spectral indices larger than...
We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard gamma-ray bands. Our unique set has allowed us demonstrate that selection method strongly influences results, producing biases cannot be ignored. Almost all BL Lac objects have been detected by Fermi-LAT, whereas ~40% of flat-spectrum radio quasars (FSRQs) radio, X-ray selected are still below detection limit even after integrating 27 months...
We present γ-ray observations with the Large Area Telescope (LAT) on board Fermi Gamma-Ray Space of nearby radio galaxy Centaurus A (Cen A). The previous EGRET detection is confirmed, and localization improved using data from first 10 months science operation. In work, we presented lobes by LAT; in this concentrate core Cen A. Flux levels as seen LAT are not significantly different that found EGRET, nor extremely soft spectrum (Γ = 2.67 ± 0.10stat 0.08sys where photon flux Φ ∝ E−Γ)....
COrE (Cosmic Origins Explorer) is a fourth-generation full-sky, microwave-band satellite recently proposed to ESA within Cosmic Vision 2015-2025. will provide maps of the microwave sky in polarization and temperature 15 frequency bands, ranging from 45 GHz 795 GHz, with an angular resolution 23 arcmin (45 GHz) 1.3 (795 sensitivities roughly 10 30 times better than PLANCK (depending on channel). The mission lead breakthrough science wide range areas, primordial cosmology galactic...
Axionlike particles (ALPs) are hypothetical light (sub-eV) bosons predicted in some extensions of the Standard Model particle physics. In astrophysical environments comprising high-energy gamma rays and turbulent magnetic fields, existence ALPs can modify energy spectrum for a sufficiently large coupling between photons. This modification would take form an irregular behavior limited range. Data from H.E.S.S. observations distant BL Lac object PKS 2155-304 (z = 0.116) used to derive upper...