The optical spectrum of PKS 1222+216 and its black hole mass

We investigate the optical spectral properties of the blazar PKS 1222+216 during a period of 3 years. While the continuum is highly variable the broad line emission is practically constant. This supports a scenario in which the broad line region is not affected by jet continuum variations. We thus infer the thermal component of the continuum from the line luminosity and we show that it is comparable with the continuum level observed during the phases of minimum optical activity. The mass of the black hole is estimated through the virial method from the FWHM of MgII, Hbeta, and Halpha broad lines and from the thermal continuum luminosity. This yields a consistent black hole mass value of 6x10^8 solar masses.Comment: 7 pages, 4 figures, accepted for publication in MNRA

Probing the nature of the massive black hole binary candidate SDSS J1536+0441

We present an imaging study of the black hole binary candidate SDSS J1536+0441 (z=0.3893), based on deep, high resolution VzK images collected at the ESO/VLT. The images clearly show an asymmetric elongation, indicating the presence of a companion source at ~1" (~5 kpc projected distance) East from the quasar. The host galaxy of the quasar is marginally resolved. We find that the companion source is a luminous galaxy, the light profile of which suggests the presence of an unresolved, faint nucleus (either an obscured AGN or a compact stellar bulge). The study of the environment around the quasar indicates the occurrence of a significant over-density of galaxies with a redshift compatible with z~0.4. This suggests that it resides in a moderately rich cluster of galaxies.Comment: 4 figures, 1 table. Accepted for publication in ApJ Letter

Search of sub-parsec massive binary black holes through line diagnosis

We investigate on the spectral properties of an active black hole, member of a massive (10^7 - 10^9 Msun) sub-parsec black hole binary. We work under the hypothesis that the binary, surrounded by a circum-binary disc, has cleared a gap, and that accretion occurs onto the secondary black hole fed by material closer to the inner edge of the disc. Broad line emission clouds orbit around the active black hole and suffer erosion due to tidal truncation at the Roche Lobe surface, following gap opening and orbital decay. We consider three of the most prominent broad emission lines observed in the spectra of AGNs, i.e. CIV, MgII and H{\beta}, and compute the flux ratios between the lines of MgII and CIV (FMgII/FCIV) and those of MgII and H{\beta} (FMgII/FH{\beta}). We find that close black hole binaries have FMgII/FCIV up to one order of magnitude smaller than single black holes. By contrast FMgII/FH{\beta} may be significantly reduced only at the shortest separations. Peculiarly low values of line flux ratios together with large velocity offsets between the broad and narrow emission lines and/or periodic variability in the continuum (on timescales >= years) would identify genuine sub-pc binary candidates.Comment: 7 pages, 4 figures. Accepted for publication in MNRA

A comparison of trends in mortality from primary liver cancer and intrahepatic cholangiocarcinoma in Europe

Background To update and compare mortality from primary liver cancer (PLC) and intrahepatic cholangiocarcinoma (ICC) in Europe in 1990-2010. Materials and methods We used data from the World Health Organization (WHO) to compute age-standardized (world population) mortality rates, and used joinpoint analysis to identify substantial changes. Results Between 2002 and 2007, PLC rates in the European Union (EU) declined from 3.9 to 3.6/100 000 men. Around 2007, the highest male rates were in France (6.2/100 000), Spain (4.9), and Italy (4.0), while the lowest ones were in Sweden (1.1), the Netherlands (1.2), and the UK (1.8). In women, mortality was lower (0.8/100 000 in 2007 in the EU), and showed more favourable trends, with a decline of over 2% per year over the last two decades as compared with 0.4% in men, in the EU. In contrast, the EU mortality from ICC increased by around 9% in both sexes from 1990 to 2008, reaching rates of 1.1/100 000 men and 0.75/100 000 women. The highest rates were in UK, Germany, and France (1.2-1.5/100 000 men, 0.8-1.1/100 000 women). Conclusions PLC mortality has become more uniform across Europe over recent years, with an overall decline; in contrast, ICC mortality has substantially increased in most Europ

The compact, ∼1 kpc host galaxy of a quasar at a redshift of 7.1

We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of the [C ii] fine-structure line and the underlying far-infrared (FIR) dust continuum emission in J1120+0641, the most distant quasar currently known ($z=7.1$). We also present observations targeting the CO(2–1), CO(7–6), and [C i] 369 μm lines in the same source obtained at the Very Large Array and Plateau de Bure Interferometer. We find a [C ii] line flux of ${F}_{[{\rm{C}}{\rm{II}}]}=1.11\pm 0.10$ Jy $\mathrm{km}\,{{\rm{s}}}^{-1}$ and a continuum flux density of ${S}_{227\mathrm{GHz}}=0.53\pm 0.04$ mJy beam−1, consistent with previous unresolved measurements. No other source is detected in continuum or [C ii] emission in the field covered by ALMA (~ 25''). At the resolution of our ALMA observations (0farcs23, or 1.2 kpc, a factor of ~70 smaller beam area compared to previous measurements), we find that the majority of the emission is very compact: a high fraction (~80%) of the total line and continuum flux is associated with a region 1–1.5 kpc in diameter. The remaining ~20% of the emission is distributed over a larger area with radius lesssim4 kpc. The [C ii] emission does not exhibit ordered motion on kiloparsec scales: applying the virial theorem yields an upper limit on the dynamical mass of the host galaxy of $(4.3\pm 0.9)\times {10}^{10}$ ${M}_{\odot }$, only ~20 × higher than the central black hole (BH). The other targeted lines (CO(2–1), CO(7–6), and [C i]) are not detected, but the limits of the line ratios with respect to the [C ii] emission imply that the heating in the quasar host is dominated by star formation, and not by the accreting BH. The star formation rate (SFR) implied by the FIR continuum is 105–340 ${M}_{\odot }\,{\mathrm{yr}}^{-1}$, with a resulting SFR surface density of ~100–350 ${M}_{\odot }\,{\mathrm{yr}}^{-1}$ kpc−2, well below the value for Eddington-accretion-limited star formation

The kiloparsec-scale star formation law at redshift 4: wide-spread, highly efficient star formation in the dust-obscured starburst galaxy GN20

We present high-resolution observations of the 880 $\mu$m (rest-frame FIR) continuum emission in the z$=$4.05 submillimeter galaxy GN20 from the IRAM Plateau de Bure Interferometer (PdBI). These data resolve the obscured star formation in this unlensed galaxy on scales of 0.3$^{\prime\prime}$$\times$0.2$^{\prime\prime}$ ($\sim$2.1$\times$1.3 kpc). The observations reveal a bright (16$\pm$1 mJy) dusty starburst centered on the cold molecular gas reservoir and showing a bar-like extension along the major axis. The striking anti-correlation with the HST/WFC3 imaging suggests that the copious dust surrounding the starburst heavily obscures the rest-frame UV/optical emission. A comparison with 1.2 mm PdBI continuum data reveals no evidence for variations in the dust properties across the source within the uncertainties, consistent with extended star formation, and the peak star formation rate surface density (119$\pm$8 M$_{\odot}$ yr$^{-1}$ kpc$^{-2}$) implies that the star formation in GN20 remains sub-Eddington on scales down to 3 kpc$^2$. We find that the star formation efficiency is highest in the central regions of GN20, leading to a resolved star formation law with a power law slope of $\Sigma_{\rm SFR}$ $\sim$ $\Sigma_{\rm H_2}^{\rm 2.1\pm1.0}$, and that GN20 lies above the sequence of normal star-forming disks, implying that the dispersion in the star formation law is not due solely to morphology or choice of conversion factor. These data extend previous evidence for a fixed star formation efficiency per free-fall time to include the star-forming medium on $\sim$kpc-scales in a galaxy 12 Gyr ago.Comment: 6 pages, 5 figures, accepted to ApJ