We present the results of the Gemini Deep Planet Survey, a near-infrared adaptive optics search for giant planets and brown dwarfs around nearby young stars. The observations were obtained with the Altair adaptive optics system at the Gemini North telescope and angular differential imaging was used to suppress the speckle noise of the central star. Detection limits for the 85 stars observed are presented, along with a list of all faint point sources detected around them. Typically, the observations are sensitive to angular separations beyond 0.5 ′′ with 5σ contrast sensitivities in magnitude difference at 1.6 µm of 9.5 at 0.5 ′′ , 12.9 at 1 ′′ , 15.0 at 2 ′′ , and 16.5 at 5 ′′ . For the typical target of the survey, a 100 Myr old K0 star located 22 pc from the Sun, the observations are sensitive enough to detect planets more massive than 2 M Jup with a projected separation in the range 40-200 AU. Depending on the age, spectral type, and distance of the target stars, the detection limit can be as low as ∼1 M Jup . Second epoch observations of 48 stars with candidates (out of 54) have confirmed that all candidates are unrelated background stars. A detailed statistical analysis of the survey results, yielding upper limits on the fractions of stars with giant planet or low mass brown dwarf companions, is presented. Assuming a planet mass distribution dn/dm ∝ m −1.2 and a semi-major axis distribution dn/da ∝ a −1 , the 95% credible upper limits on the fraction of stars with at least one planet of mass 0.5-13 M Jup are 0.28 for the range 10-25 AU, 0.13 for 25-50 AU, and 0.093 for 50-250 AU; this result is weakly dependent on the semi-major axis distribution power-law index. The 95% credible interval for the fraction of stars with at least one brown dwarf companion having a semi-major axis in the range 25-250 AU is 0.019 +0.083 −0.015 , irrespective of any assumption on the mass and semi-major axis distributions. The observations made as part of this survey have resolved the stars HD 14802, HD 166181, and HD 213845 into binaries for the first time.

We used the CLUMPY torus models and a Bayesian approach to fit the infrared spectral energy distributions (SEDs) and ground-based high-angular resolution mid-infrared spectroscopy of 13 nearby Seyfert galaxies. This allowed us to put tight constraints on torus model parameters such as the viewing angle i, the radial thickness of the torus Y , the angular size of the cloud distribution σ torus , and the average number of clouds along radial equatorial rays N 0 . We found that the viewing angle i is not the only parameter controlling the classification of a galaxy into a type 1 or a type 2. In principle type 2s could be viewed at any viewing angle i as long as there is one cloud along the line of sight. A more relevant quantity for clumpy media is the probability for an AGN photon to escape unabsorbed. In our sample, type 1s have relatively high escape probabilities, P esc ∼ 12 − 44%, while type 2s, as expected, tend to have very low escape probabilities. Our fits also confirmed that the tori of Seyfert galaxies are compact with torus model radii in the range 1-6 pc. The scaling of the models to the data also provided the AGN bolometric luminosities L bol (AGN), which were found to be in good agreement with estimates from the literature. When we combined our sample of Seyfert galaxies with a sample of PG quasars from the literature to span a range of L bol (AGN) ∼ 10 43 − 10 47 erg s −1 , we found plausible evidence of the receding torus. That is, there is a tendency for the torus geometrical covering factor to be lower (f 2 ∼ 0.1 − 0.3) at high AGN luminosities than at low AGN luminosities (f 2 ∼ 0.9 − 1 at ∼ 10 43−44 erg s −1 ). This is because at low AGN luminosities the tori appear to have wider angular sizes (larger σ torus ) and more clouds along radial equatorial rays. We cannot, however rule out the possibility that this is due to contamination by extended dust structures not associated with the dusty torus at low AGN luminosities, since most of these in our sample are hosted in highly inclined galaxies.

We present broad‐band spectra of a sample of 21 low‐luminosity sources in the Trapezium cluster, with masses in the range 0.008–0.10 M⊙ (assuming an age of 1 Myr). These were selected for low extinction in most cases, and are located west of the brighter nebulosity. The spectra are in the H bandpass (1.4–1.95 μm) and K bandpass (1.9–2.5 μm) also for most of the brighter sources, with a resolution of 50 nm. They were taken with the United Kingdom Infrared Telescope (UKIRT) using the CGS4 spectrometer. Absorption by water vapour bands is detected in all the substellar candidates except one, which is a highly reddened object with strong H2 emission and an anomalously blue (I−J) colour, implying that it is a very young cluster member with circumstellar matter. The observation of prominent water vapour bands confirms the low effective temperatures implied by our (I−J) colour measurements in an earlier paper, and would imply late‐M or L spectral types if these were older field dwarfs. However, the profiles of the H‐bandpass spectra are very different from those of field dwarfs with similar water absorption strength, demonstrating that they are not foreground or background objects. In addition, the CO absorption bands at 2.3 μm and the Na i absorption feature at 2.21 μm are very weak for such cool sources. All these features are quite well reproduced by the AMES‐Dusty‐1999 model atmospheres of Allard et al., and arise from the much lower gravities predicted for the Trapezium sources (3.5< log g<4.0) compared to evolved objects (log g∼5.5). This represents a new proof of the substellar status of our sources, independent of the statistical arguments for low contamination, which are re‐examined here. The very late spectral types of the planetary mass objects and very low‐mass brown dwarfs demonstrate that they are cluster members, since they are too luminous to be field dwarfs in the background. We also present additional UKIRT photometry of a small region in the south of the Trapezium cluster where the extinction and nebular brightness are low, which permitted the detection of objects with 1‐Myr masses slightly lower than our previous least massive source at 8 MJup. Following a minor update to our previous J‐band photometry, due to a new UKIRT filter calibration, there are ∼15 planetary mass candidates in the full data set.

Recent theoretical and observational works indicate the presence of a correlation between the star formation rate (SFR) and the active galactic nuclei (AGN) luminosity (and, therefore, the black hole accretion rate,Ṁ BH ) of Seyfert galaxies. This suggests a physical connection between the gas forming stars on kpc scales and the gas on sub-pc scales that is feeding the black hole. We compiled the largest sample of Seyfert galaxies to date with high angular resolution (∼ 0.4 − 0.8 ′′ ) mid-infrared (8-13 µm) spectroscopy. The sample includes 29 Seyfert galaxies drawn from the AGN Revised Shapley-Ames catalogue. At a median distance of 33 Mpc, our data allow us to probe nuclear regions on scales of ∼ 65 pc (median value). We found no general evidence of suppression of the 11.3 µm polycyclic aromatic hydrocarbon (PAH) emission in the vicinity of these AGN, and used this feature as a proxy for the SFR. We detected the 11.3 µm PAH feature in the nuclear spectra of 45% of our sample. The derived nuclear SFRs are, on average, five times lower than those measured in circumnuclear regions of 600 pc in size (median value). However, the projected nuclear SFR densities (median value of 22 M ⊙ yr −1 kpc −2 ) are a factor of 20 higher than those measured on circumnuclear scales. This indicates that the SF activity per unit area in the central ∼ 65 pc of Seyfert galaxies is much higher than at larger distances from their nuclei. We studied the connection between the nuclear SFR anḋ M BH and showed that numerical simulations reproduce fairly well our observed relation.

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