Astroparticle physics plays a central role in addressing fundamental questions in modern physics by connecting particle physics, cosmology, and astrophysics. Among the main problems, we highlight the nature of dark matter and dark energy, primordial inflation, the matter-antimatter asymmetry of the universe, and the origin of ultra-high-energy cosmic messengers. In this article, we review the main observational evidence for dark matter, which spans scales from galactic to cosmological, and discuss the two most explored scenarios for its nature: primordial black holes and new fundamental particles beyond the Standard Model. We explore the main theoretical and experimental bottlenecks that challenge the search for the nature of dark matter, highlighting those associated with extended mass distributions of primordial black holes and the absence of weakly interacting massive particle signals in direct, indirect, and accelerator detection experiments. We also discuss the role of next-generation experiments, including very high-energy gamma-ray telescopes and multi-messenger detectors. Finally, we conclude that the combination of high-precision observations and theoretical advances will be crucial to elucidating the microphysics of dark matter and deepening our understanding of the extreme universe.
Estrelas de nêutrons são astros absolutamente fascinantes. Em seu interior, a matéria está sujeita a condições extremas, manifestando-se em formas muito diversas daquelas encontradas em nosso planeta, ou mesmo acessíveis experimentalmente; assim, sua observação abre uma janela para uma maior compreensão das interações nucleares. São abarcadas por intensos campos gravitacionais, permitindo que comportamentos intrigantes da gravitação se manifestem. Cumprem um papel importantíssimo na evolução química das galáxias, com seu nascimento e fusão estando ligados à produção de vários elementos químicos que encontramos no nosso dia a dia. Estrelas de nêutrons são hoje observadas em todas as faixas do espectro eletromagnético e também em ondas gravitacionais. A combinação da pletora de informações carregadas por esses mensageiros tem ajudado a compor uma imagem cada vez mais nítida e coerente da física que envolve esses astros, oferecendo chaves para o aprofundamento do nosso conhecimento sobre a natureza.
Kouichi Hagino, Kazuhiro Nakazawa, Goro Sato
et al.
The Hard X-ray Imager (HXI) onboard Hitomi (ASTRO-H) is an imaging spectrometer covering hard X-ray energies of 5-80 keV. Combined with the hard X-ray telescope, it enables imaging spectroscopy with an angular resolution of $1^\prime.7$ half-power diameter, in a field of view of $9^\prime\times9^\prime$. The main imager is composed of 4 layers of Si detectors and 1 layer of CdTe detector, stacked to cover wide energy band up to 80 keV, surrounded by an active shield made of BGO scintillator to reduce the background. The HXI started observations 12 days before the Hitomi loss, and successfully obtained data from G21.5$-$0.9, Crab and blank sky. Utilizing these data, we calibrate the detector response and study properties of in-orbit background. The observed Crab spectra agree well with a powerlaw model convolved with the detector response, within 5% accuracy. We find that albedo electrons in specified orbit strongly affect the background of Si top layer, and establish a screening method to reduce it. The background level over the full field of view after all the processing and screening is as low as the pre-flight requirement of $1$-$3\times10^{-4}$ counts s$^{-1}$ cm$^{-2}$ keV$^{-1}$.
Frederic Bournaud, Valentin Perret, Florent Renaud
et al.
Star-forming disk galaxies at high redshift are often subject to violent disk instability, characterized by giant clumps whose fate is yet to be understood. The main question is whether the clumps disrupt within their dynamical timescale (<50Myr), like molecular clouds in today's galaxies, or whether they survive stellar feedback for more than a disk orbital time (~300Myr) in which case they can migrate inward and help building the central bulge. We present 3.5-7pc resolution AMR simulations of high-redshift disks including photo-ionization, radiation pressure, and supernovae feedback (Renaud et al. 2013, and Perret et al., this astro-ph issue). Our modeling of radiation pressure determines the mass loading and initial velocity of winds from basic physical principles. We find that the giant clumps produce steady outflow rates comparable to and sometimes somewhat larger than their star formation rate, with velocities largely sufficient to escape galaxy. The clumps also lose mass, especially old stars, by tidal stripping, and the stellar populations contained in the clumps hence remain relatively young (<=200Myr), as observed. The clumps survive gaseous outflows and stellar loss, because they are wandering in gas-rich turbulent disks from which they can re-accrete gas at high rates compensating for outflows and tidal stripping, overall keeping realistic and self-regulated gaseous and stellar masses. Our simulations produce gaseous outflows with velocities, densities and mass loading consistent with observations, and at the same time suggest that the giant clumps survive for hundreds of Myr and complete their migration to the center of high-redshift galaxies, without rapid dispersion and reformation of clumps.
Abstract Technological and scientific developments during the past century made a new branch of astronomy flourish, i.e. astrophysics, and resulted in our present deep understanding of the whole Universe. But this brought astrometry almost to extinction because it was considered to be dull and old-fashioned, especially by young astronomers. Astrometry is the much older branch of astronomy, in fact 2000 years of age, which performs accurate measurements of positions, motions and distances of stars and other celestial bodies. Astrometric data are of great scientific and practical importance for investigation of celestial phenomena and also for control of telescopes and satellites and for monitoring of Earth rotation. Our main subject is the development during the 20th century which finally made astrometry flourish as an integral part of astronomy through the success of the Hipparcos astrometric satellite, soon to be followed by the even more powerful Gaia mission.
T. M. C. H. Anderhub, L. A. Antonelli, P. Antoranz
et al.
Index entry listing the contributed papers of the MAGIC collaboration to the 31th International Cosmic Ray Conference (ICRC 2009), July 7-15 2009, \L\'od\'z, Poland. The individual papers are sorted by subject: Overview and Highlight Papers; MAGIC-II Status and Components; Software and Analysis Techniques; Technical Developments; Scientific Results. This HTML document includes clickable links to the papers that exist on the astro-ph arXiv. We hope that this will make it easy to access the MAGIC contributions in a systematic way.
This is a report on the findings of the gamma ray burst working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper is an APS commissioned document, and the overall version has also been released and can be found on astro-ph. This detailed section of the white paper discusses the status of past and current attempts to observe gamma ray bursts at GeV-TeV energies. We concentrate on the potential of future ground-based gamma-ray experiments to observe the highest energy emission ever recorded for GRBs, particularly for those that are nearby and have high Lorentz factors in the GRB jet. It is clear that major advances are possible and that the detection of very high energy emission would have strong implications for GRB models, as well as cosmic ray origin.
This is a report on the findings of the technology working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper is an APS commissioned document, and the overall version has also been released and can be found on astro-ph. This detailed section of the white paper discusses different technology opportunities and the technical feasibility for substantially improving IACTS and ground based particle detectors to achieve an order of magnitude better sensitivity than the instruments employed today as well as their planned upgrades. A technology roadmap for improving IACTS and ground based particle detectors is presented.
This is a report on the findings of the Galactic compact objects working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper is an APS commissioned document, and the full version has also been released and can be found on astro-ph. This section of the white paper discusses the potential of future ground-based gamma-ray experiments to advance our understanding of the physics of Galactic compact objects including pulsars, pulsar wind nebulae, and X-ray binaries.
It is pointed out that the exact renormalization group approach to cosmological perturbation theory, proposed in Matarrese and Pietroni (2007 J. Cosmol. Astropart. Phys. JCAP06(2007)026 [astro-ph/0703563]) and Matarrese and Pietroni (2007 Preprint astro-ph/0702653), constitutes a misnomer. Rather, having instructively cast this classical problem into path integral form, the evolution equation then derived comes about as a special case of considering how the generating functional responds to variations of the primordial power spectrum.