Euniversity of VALPARAISO – CHILE
Under unification schemes, active galactic nuclei (AGN) can be explained by orientation effects. However, some sources show properties at different
frequencies that led to incongruent classifications and cannot be explained by such unification scheme. This is the case of PBC J2333.9-2343; its optical
pectrum is of a type 2 AGN but its X-ray spectrum does not show signs of absorption, and in the radio it has many features typical of a blazar but it is a giant
radio galaxy. Using multiwavelength simultaneous data from XMM-Newton, San Pedro Mártir telescope and VLBA, we find that these classifications cannot
be attributed to variability. We propose that PBC J2333.2343 is a blazar that has undergone a restarting activity episode in its nucleus. Interestingly, it has
changed from being a radio galaxy to become a blazar, showing an exceptional change in the direction of the jet that, by chance, occurred in the plane of the sky.
Moreover, we have analyzed Swift and New Technology Telescope (NTT) data to study the variability of the source, revealing a change in the broad line region
BLR) clouds and increasing variability at all observed wavelengths and we have detected an outflow in its optical spectra.
Area Tor Vergata – IAPS
Via Fosso Del Cavaliere, 100
INAF – Ossrvatorio Astronomico di Roma
It has been known for decades that the observed number of baryons in the local Universe falls about 30-40% short of the total number of baryons
predicted by Big-Bang Nucleosynthesis, inferred by density fluctuations of the Cosmic Microwave Background and seen during the first 2-3 billion
years of the universe (redshift z>2-3) in the so called “Lyman-α Forest”. While theory provides a reasonable solution to this paradox, by locating
the missing baryons in hot and tenuous filamentary gas connecting galaxies, it also sanctions the difficulty of detecting them because their by far
largest constituent, hydrogen, is mostly ionized and therefore virtually invisible in ordinary signal-to-noise Far-Ultraviolet spectra. Indeed, despite
the large observational efforts, only a few marginal claims of detection have been made so far.
Here I will first review the observational efforts pursued over the past 15 years by several groups and will then present our recent results that show
that the missing baryons are indeed found in a tenuous warm-hot and moderately enriched medium that traces large concentrations of galaxies
and permeates the space between and around them. I will show that the number of OVII systems detected down to the sensitivity threshold of our
data, agrees well with numerical simulation predictions for the long-sought hot intergalactic medium, and its detection adds a fundamental tile to
the long-standing missing baryon puzzle. Finally, I will comment on the implications of these new results for future high resolution X-ray missions
Area Tor Vergata – IAPS – Via Fosso Del Cavaliere, 100