The relationship between [OIII]5007A equivalent width and obscuration in AGN

In this paper we study the relationship between the equivalent width (EW) of the [OIII]5007A narrow emission line in AGN and the level of obscuration. To this end, we combine the results of a systematic spectral analysis, both in the optical and in the X-rays, on a statistically complete sample of ~170 X-ray selected AGN from the XMM-Newton Bright Serendipitous Source sample (XBS). We find that the observed large range of [OIII]5007A equivalent widths observed in the sample (from a few A up to 500A) is well explained as a combination of an intrinsic spread, probably due to the large range of covering factors of the Narrow Line Region, and the effect of absorption. The intrinsic spread is dominant for EW below 40-50A while absorption brings the values of EW up to ~100-150A, for moderate levels of absorption (AV~0.5-2 mag) or up to ~500A for AV>2 mag. In this picture, the absorption has a significant impact on the observed EW also in type~1 AGN. Using numerical simulations we find that this model is able to reproduce the [OIII]5007A EW distribution observed in the XBS sample and correctly predicts the shape of the EW distribution observed in the optically selected sample of QSO taken from the SDSS survey.Comment: 7 pages, 5 figures. Accepted for publication in MNRA

Optical Spectroscopy of the unusual galaxy J2310-43

We present and discuss new spectroscopic observations of the unusual galaxy J2310-43. The observations cover a wide wavelength range, from 3700 A to 9800 A allowing the study of both the regions where H alpha and the Ca II ``contrast'' are expected. No evidence for H alpha in emission is found and we thus confirm the absence of emission lines in the spectrum of J2310-43, ruling out the possibility that it may host a Seyfert nucleus. The CaII break is clearly detected and the value of the contrast (38 +/-4 %) is intermediate between that of a typical elliptical galaxy (about 50 %) and that of a BL Lac object (<25 %). This result imposes limits on the intensity of a possible non-stellar continuum and, in the light of the radio and X-ray loudness of the source, draws further attention to the problem of the recognition of a BL Lac object. Objects like J2310-43 may be more common than previously recognized, and begin to emerge in surveys of radio-emitting X-ray sources.Comment: 7 pages, 1 figure; to be published in The Astronomical Journa

What is in a radio loud NLS1?

A fraction of Narrow Line Seyfert 1 galaxies (NLS1) are hosted by galaxies that present a disturbed morphology, in some cases hinting for merger processes, that are putative sources of gas replenishment. We have been investigating the poorly studied population of radio loud NLS1 (RL-NLS1) showing a flat radio spectrum, assumed to be the manifestation of the presence of a radio jet. In some of the objects the infrared emission is well fitted by a combination of an AGN component and an "active" host galaxy component like M82, the estimate SFR being in the LIRG/ULIRG range (10-500 Msun/year). In order to better characterize that component, we have been investigating the sub-millimeter/millimeter emission of the sources using APEX. Here we present the results concerning a pilot sample of 2 representative objects.Comment: 5 pages, published on Proceedings of Science - volume "Revisiting narrow-line Seyfert 1 galaxies and their place in the Universe

Hard synchrotron BL Lacs: the case of 1ES 1101-232

The bright X-ray selected BL Lac object 1ES1101--232 shows a flat X-ray spectrum, making it detectable with high statistics over the wide BeppoSAX energy range. We have observed it in two different epochs with BeppoSAX, and found a variation of the flux of about 30% that can be explained by a change in the spectral index above the synchrotron peak. We present here the data and infer limits on the strength of the magnetic field based on models of emission for High-frequency peaked BL Lacs.Comment: 4 pages, proceedings of `X-ray Astronomy '999 -- Stellar Endpoints, AGN and the Diffuse Background", held in Bologna - Italy, September 6-10, 1999, Astrophysical Letters and Communications. Needs bo99.st

Connecting blazars with ultra high energy cosmic rays and astrophysical neutrinos

We present a strong hint of a connection between high energy $\gamma$-ray emitting blazars, very high energy neutrinos, and ultra high energy cosmic rays. We first identify potential hadronic sources by filtering $\gamma$-ray emitters %from existing catalogs that are in spatial coincidence with the high energy neutrinos detected by IceCube. The neutrino filtered $\gamma$-ray emitters are then correlated with the ultra high energy cosmic rays from the Pierre Auger Observatory and the Telescope Array by scanning in $\gamma$-ray flux ($F_{\gamma}$) and angular separation ($\theta$) between sources and cosmic rays. A maximal excess of 80 cosmic rays (42.5 expected) is found at $\theta\leq10^{\circ}$ from the neutrino filtered $\gamma$-ray emitters selected from the second hard {\it Fermi}-LAT catalogue (2FHL) and for $F_\gamma\left(>50\:\mathrm{GeV}\right)\geq1.8\times10^{-11}\:\mathrm{ph}\,\mathrm{cm}^{-2}\,\mathrm{s}^{-1}$. The probability for this to happen is $2.4 \times 10^{-5}$, which translates to $\sim 2.4 \times 10^{-3}$ after compensation for all the considered trials. No excess of cosmic rays is instead observed for the complement sample of $\gamma$-ray emitters (i.e. not in spatial connection with IceCube neutrinos). A likelihood ratio test comparing the connection between the neutrino filtered and the complement source samples with the cosmic rays favours a connection between neutrino filtered emitters and cosmic rays with a probability of $\sim1.8\times10^{-3}$ ($2.9\sigma)$ after compensation for all the considered trials. The neutrino filtered $\gamma$-ray sources that make up the cosmic rays excess are blazars of the high synchrotron peak type. More statistics is needed to further investigate these sources as candidate cosmic ray and neutrino emitters.Comment: Accepted for publication in MNRAS, added one figure (redshift distribution), new IceCube data, and penalty factor for subsets within single catalogue

Recent results and future perspectives of the Borexino experiment

We present the main results achieved by the Borexino experiment on solar neutrino physics. Borexino is a large mass/high radiopurity liquid scintillator detector located under the Gran Sasso mountain (Italy). It has collected high quality data since May 2007. The results presented here refer to the so-called Phase 1 of the experiment which ended in May 2010. Borexino Phase 2 started in October 2011 after an intensive campaign of purification which significantly improved the (already exceptional) quality of the scintillator. The physics potentialities and future perspectives of this second phase of Borexino will be shortly discussed

Neutrino physics with the Borexino experiment

Borexino is a large mass, high radiopurity detector located under the Gran Sasso Mountain (Italy) and designed to measure in real-time the flux of low energy solar neutrinos. Borexino has been taking data continuously since May 2007. This talk is focused on the main goal of Borexino, the measurement of solar neutrinos produced in the 7Be reaction: I will present the result on the 7Be flux obtained in 2008 after 192 days of data-taking together with a preliminary evaluation of the daynight asymmetry of the signal. I will also discuss the impact on the analysis of the two extensive calibration campaigns performed in 2009. Thanks to these campaigns a new measurement of the 7Be flux will be shortly published with significantly reduced error. Borexino is also able of measuring the 8B neutrino flux with an unprecedented low threshold of 3MeV (scattered electron kinetic energy): it is the only experiment able of probing the survival probability in the vacuum dominated oscillation regime (with 7Be neutrinos) and in the matter enhanced oscillation regime (with 8B). Finally, I will also present another important result of Borexino, namely the first clear observation of geoneutrinos

GALEX measurements of the Big Blue Bump as a tool to study bolometric corrections in AGNs

Active Galactic Nuclei emit over the entire electromagnetic spectrum with the peak of the accretion disk emission in the far-UV, a wavelength range historically difficult to investigate. We use here the GALEX (Galaxy Evolution Explorer) Near-UV and Far-UV measurements (complemented with optical data from Sloan Digital Sky Survey (SDSS) and XMM-Newton X-ray spectra) of a sample of 83 X-ray selected type 1 AGN extracted from the XMM-Newton Bright Serendipitous Survey to study their spectral energy distribution (SED) in the optical, Near and Far-UV and X-ray energy bands. We have constrained the luminosity of the accretion disk emission component and calculated the hard X-ray bolometric corrections for a significant sample of AGN spanning a large range in properties (z, L(x)).Comment: 2 pages, 2 figures, To appear in refereed Proceedings of "X-ray Astronomy 2009: Present Status, Multi-Wavelength Approach and Future Perspectives", Bologna, Italy, September 7-11, 2009, AIP, eds. A. Comastri, M. Cappi, and L. Angelin