We present time-resolved broad-band observations of the quasar 3C 279 obtained from multiwavelength campaigns conducted during the first two years of the Fermi Gamma-ray Space Telescope mission. While investigating the previously reported γ-ray/optical flare accompanied by a change in optical polarization, we found that the optical emission appears delayed with respect to the γ-ray emission by about 10 days. X-ray observations reveal a pair of 'isolated' flares separated by ∼ 90 days, with only weak γ-ray/optical counterparts. The spectral structure measured by Spitzer reveals a synchrotron component peaking in the mid-infrared band with a sharp break at the far-infrared band during the γ-ray flare, while the peak appears in the mm/sub-mm band in the low state. Selected spectral energy distributions are fitted with leptonic models including Comptonization of external radiation produced in a dusty torus or the broad-line region. Adopting the interpretation of the polarization swing involving propagation of the emitting region along a curved trajectory, we can explain the evolution of the broad-band spectra during the γ-ray flaring event by a shift of its location from ∼ 1 pc to ∼ 4 pc from the central black hole. On the other hand, if the γ-ray flare is generated instead at sub-pc distance from the central black hole, the far-infrared break can be explained by synchrotron self-absorption. We also model the low spectral state, dominated by the mm/sub-mm peaking synchrotron component, and suggest that the corresponding inverse-Compton component explains the steady X-ray emission.

We present the first observations of the Frontier Fields cluster Abell S1063 taken with the newly commissioned Multi Unit Spectroscopic Explorer (MUSE) integral field spectrograph. Because of the relatively large field of view (1 arcmin 2 ), MUSE is ideal to simultaneously target multiple galaxies in blank and cluster fields over the full optical spectrum. We analysed the four hours of data obtained in the science verification phase on this cluster and measured redshifts for 53 galaxies. We confirm the redshift of five cluster galaxies, and determine the redshift of 29 other cluster members. Behind the cluster, we find 17 galaxies at higher redshift, including three previously unknown Lyman-α emitters at z > 3, and five multiply-lensed galaxies. We report the detection of a new z = 4.113 multiply lensed galaxy, with images that are consistent with lensing model predictions derived for the Frontier Fields. We detect C ], C , and He  emission in a multiply lensed galaxy at z = 3.116, suggesting the likely presence of an active galactic nucleus. We also created narrow-band images from the MUSE datacube to automatically search for additional line emitters corresponding to high-redshift candidates, but we could not identify any significant detections other than those found by visual inspection. With the new redshifts, it will become possible to obtain an accurate mass reconstruction in the core of Abell S1063 through refined strong lensing modelling. Overall, our results illustrate the breadth of scientific topics that can be addressed with a single MUSE pointing. We conclude that MUSE is a very efficient instrument to observe galaxy clusters, enabling their mass modelling, and to perform a blind search for high-redshift galaxies.

There is considerable discrepancy between the amount of X-ray absorption and what is inferred from optical (rest frame UV) as measured along gamma-ray burst (GRB) sight lines, with the former typically an order of magnitude higher than what would be expected from the measurement of neutral element species via optical absorption line spectroscopy. We explored this "missing gas problem" in a sample of 29 GRBs with redshifts in the range 0.7-6.3 by studying the X-ray and optical spectra, as well as the afterglow broadband spectral energy distributions. The low ionisation species detected in the UV are associated with the neutral interstellar medium in the GRB host galaxy, while soft X-ray absorption, which is weakly dependent on the ionisation state of the gas, provides a probe of the total column of gas along the sight line. After careful consideration of any systematic effects, we find that the neutral gas consists of 10% of the total gas, and this limit decreases the more ionised the X-ray absorbing gas is, which in our spectral fits is assumed to be neutral. Only a very small fraction of this ionised gas, however, is detected in UV absorption lines with ionisation potentials up to ∼200 eV (i.e. Si iv, C iv, N v, O vi), which leaves us to postulate that the X-ray excess comes from ultra-highly-ionised, dense gas in the GRB vicinity.

We present a study of the H ii regions in the galaxy NGC 6754 from a two pointing mosaic comprising 197 637 individual spectra, using integral field spectroscopy recently acquired with the MUSE instrument during its Science Verification program. The data cover the entire galaxy out to ∼2 effective radii (r e ), sampling its morphological structures with unprecedented spatial resolution for a wide-field Integral Field Unit. A complete census of the H ii regions limited by the atmospheric seeing conditions was derived, comprising 396 individual ionized sources. This is one of the largest and most complete catalogues of H ii regions with spectroscopic information in a single galaxy. We use this catalogue to derive the radial abundance gradient in this SBb galaxy, finding a negative gradient with a slope consistent with the characteristic value for disk galaxies recently reported. The large number of H ii regions allows us to estimate the typical mixing scale length (r mix ∼ 0.4 r e ), which sets strong constraints on the proposed mechanisms for metal mixing in disk galaxies, like radial movements associated with bars and spiral arms. We found evidence of an azimuthal variation in the oxygen abundance that may be connected with the radial migration. These results illustrate the unique capabilities of MUSE for the study of the enrichment mechanisms in Local Universe galaxies.

We present and analyse an extensive dataset of the superluminous supernova (SLSN) LSQ14mo (z = 0.256), consisting of a multicolour lightcurve from −30 d to +70 d in the rest-frame (relative to maximum light) and a series of six spectra from PESSTO covering −7 d to +50 d. This is among the densest spectroscopic coverage, and best-constrained rising lightcurve, for a fast-declining hydrogenpoor SLSN. The bolometric lightcurve can be reproduced with a millisecond magnetar model with ∼ 4 M ejecta mass, and the temperature and velocity evolution is also suggestive of a magnetar as the power source. Spectral modelling indicates that the SN ejected ∼ 6 M of CO-rich material with a kinetic energy of ∼ 7 × 10 51 erg, and suggests a partially thermalised additional source of luminosity between −2 d and +22 d. This may be due to interaction with a shell of material originating from pre-explosion mass loss. We further present a detailed analysis of the host galaxy system of LSQ14mo. PESSTO and GROND imaging show three spatially resolved bright regions, and we used the VLT and FORS2 to obtain a deep (five-hour exposure) spectra of the SN position and the three star-forming regions, which are at a similar redshift. The FORS spectrum at +300 days shows no trace of SN emission lines and we place limits on the strength of [O i] from comparisons with other Ic supernovae. The deep spectra provides a unique chance to investigate spatial variations in the host star-formation activity and metallicity. The specific star-formation rate is similar in all three components, as is the presence of a young stellar population. However, the position of LSQ14mo exhibits a lower metallicity, with 12 + log(O/H) = 8.2 in both the R 23 and N2 scales (corresponding to ∼ 0.3 Z ). We propose that the three bright regions in the host system are interacting, which thus triggers star formation and forms young stellar populations.