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Limits on Dark Matter Annihilation Signals from the Fermi LAT 4-year Measurement of the Isotropic Gamma-Ray Background
The Fermi LAT Collaboration, M. Ackermann, M. Ajello +110
We search for evidence of dark matter (DM) annihilation in the isotropic gamma-ray background (IGRB) measured with 50 months of Fermi Large Area Telescope (LAT) observations. An im…
Physical properties in young radio sources. VLBA observations of high frequency peaking radio sources
M. Orienti, D. Dallacasa
Multifrequency Very Long Baseline Array (VLBA) observations were performed to study the radio morphology and the synchrotron spectra of four high frequency peaking radio sources. T…
Radio Jets Clearing the Way Through a Galaxy: Watching Feedback in Action
Raffaella Morganti, Judit Fogasy, Zsolt Paragi +2
The energy released by an active galactic nucleus (AGN) has a strong impact on the surrounding interstellar medium (ISM). This feedback is considered to be the regulating factor fo…
A sample of small size compact steep-spectrum radio sources. VLBI images and VLA polarization at 5 GHz
D. Dallacasa, M. Orienti, C. Fanti +2
Global VLBI observations at 5 GHz have been performed to study the source morphology in 10 compact steep-spectrum (CSS) sources selected from the Peacock & Wall catalogue with the…
The Imprint of The Extragalactic Background Light in the Gamma-Ray Spectra of Blazars
LAT Collaboration
The light emitted by stars and accreting compact objects through the history of the Universe is encoded in the intensity of the extragalactic background light (EBL). Knowledge of t…
Physical properties of the nuclear region in Seyfert galaxies derived from observations with the European VLBI Network
P. Bontempi, M. Giroletti, F. Panessa +2
We report on sensitive dual-frequency (1.7 and 5 GHz) European VLBI Network observations of the central region of nine Seyfert galaxies. These sources are among the faintest and le…
Parsec-scale morphology and spectral index distribution in faint high frequency peakers
M. Orienti, D. Dallacasa
We investigate the parsec-scale structure of 17 high frequency peaking radio sources from the faint HFP sample. VLBA observations were carried out at two adjacent frequencies, 8.4…
Constraints on the Galactic Halo Dark Matter from Fermi-LAT Diffuse Measurements
LAT collaboration, M. Ackermann, M. Ajello +139
We have performed an analysis of the diffuse gamma-ray emission with the Fermi Large Area Telescope in the Milky Way Halo region searching for a signal from dark matter annihilatio…
Complex particle acceleration processes in the hotspots of 3C105 and 3C445
M. Orienti, M. A. Prieto, G. Brunetti +3
We investigate the nature of the broad-band emission associated with the low-power radio hotspots 3C105 South and 3C445 South. Both hotspot regions are resolved in multiple radio/o…
Multi-epoch parsec-scale observations of the blazar PKS 1510-089
M. Orienti, T. Venturi, D. Dallacasa +5
(Abridged) We investigate the flux density variability and changes in the parsec-scale radio structure of the flat spectrum radio quasar PKS 1510-089. This source was target of mul…
Steep-spectrum sources and the duty cycle of the radio emission
M. Orienti, D. Dallacasa
It is currently accepted that intrinsically compact and bright radio sources characterized by a convex spectrum peaking at frequencies ranging from 100 MHz to a few GHz are young o…
Flux variability in the FSRQ 1510-089. A radio-gamma perspective
M. Orienti, G. Giovannini, D. Dallacasa +5
The knowledge of the physical conditions occurring in the relativistic jet of radio-loud active galactic nuclei (AGNs) is important to understand the mechanisms at the basis of the…
Young radio sources: a radio-gamma perspective
M. Orienti, G. Migliori, A. Siemiginowska +1
The evolutionary stage of a powerful radio source originated by an AGN is related to its linear size. In this context, compact symmetric objects (CSOs), which are powerful and intr…
Spectral variability in faint high frequency peakers
M. Orienti, D. Dallacasa, C. Stanghellini
We present the analysis of simultaneous multi-frequency Very Large Array (VLA) observations of 57 out of 61 sources from the ``faint'' high frequency peaker (HFP) sample carried ou…
Proper motion and apparent contraction in J0650+6001
M. Orienti, D. Dallacasa
We present a multi-epoch and multi-frequency VLBI study of the compact radio source J0650+6001. In VLBI images the source is resolved into three components. The central component s…
The last breath of the young gigahertz-peaked spectrum radio source PKS 1518+047
M. Orienti, M. Murgia, D. Dallacasa
We present the results from multi-frequency VLBA observations from 327 MHz to 8.4 GHz of the gigahertz-peaked spectrum radio source PKS 1518+047 (4C 04.51) aimed at studying the sp…
Radio structures of the nuclei of nearby Seyfert galaxies and the nature of the missing diffuse emission
M. Orienti, M. A. Prieto
We present archival high spatial resolution VLA and VLBA data of the nuclei of seven of the nearest and brightest Seyfert galaxies in the Southern Hemisphere. At VLA resolution (~0…
The spectral energy distribution of the central parsecs of the nearest AGN
M. A. Prieto, J. Reunanen, K. R. W. Tristram +4
Spectral energy distributions (SEDs) of the central few tens of parsec region of some of the nearest, most well studied, active galactic nuclei (AGN) are presented. These genuine A…
Small and young radio sources
M. Orienti
It is currently accepted that compact and bright radio sources characterized by a convex spectrum peaking at frequencies ranging from 100 MHz to a few GHz are young objects. In thi…
High Frequency Peakers: The Faint Sample
Carlo Stanghellini, Daniele Dallacasa, Monica Orienti
We present a sample of sources with convex radio spectra peaking at frequencies above a few GHz, known as "High Frequency Peakers" (HFPs). A "bright" sample with a flux density lim…