We report on a survey of the brightest portions of the Orion Nebula made with the Wide Field Planetary Camera 2 of the Hubble Space Telescope. Fifteen paintings were made, each employing interference filters isolating the principal emission lines of HI, [NII], and [OIII] and another isolating an interval similar to the V bandpass. A careful survey of compact objects of stellar and nearly stellar appearance was made and astrometric solutions for individual fields were used to determine positions accurate to about 0.1". 344 stars were measured, down to about V=22. In addition to structures in several of the previously known Herbig-Haro objects, 145 compact sources that can be classified as proplyds were found. Proplyds are young stars surrounded by circumstellar material which is rendered visible by being in or near an HII region. In the central region, where detection of proplyds is easiest, almost all of the low-mass pre-main-sequence stars have obvious circumstellar material. The fraction falls as one views areas away from the dominant photoionizing star {theta}^1^C Ori. Six new dark disk proplyds are found, bringing the total to seven. These are objects showing only in silhouette against the bright background of the HII region. Most of these are elliptical in form, indicating that they are circumstellar disks. In addition to these compact sources, the new images allow detection of numerous large structures previously unreported from ground-based observations. These include shells and shocks apparently related to Herbig-Haro objects and high velocity outflows from young stellar objects.
The Outer Solar System Origins Survey (OSSOS), a wide-field imaging program in 2013-2017 with the Canada-France-Hawaii Telescope, surveyed 155deg^2^ of sky to depths of m_r_=24.1-25.2. We present 838 outer solar system discoveries that are entirely free of ephemeris bias. This increases the inventory of trans-Neptunian objects (TNOs) with accurately known orbits by nearly 50%. Each minor planet has 20-60 Gaia/Pan-STARRS-calibrated astrometric measurements made over 2-5 oppositions, which allows accurate classification of their orbits within the trans-Neptunian dynamical populations. The populations orbiting in mean-motion resonance with Neptune are key to understanding Neptune's early migration. Our 313 resonant TNOs, including 132 plutinos, triple the available characterized sample and include new occupancy of distant resonances out to semimajor axis a ~130au. OSSOS doubles the known population of the nonresonant Kuiper Belt, providing 436 TNOs in this region, all with exceptionally high-quality orbits of a uncertainty {sigma}_a_<=0.1%; they show that the belt exists from a>~37au, with a lower perihelion bound of 35au. We confirm the presence of a concentrated low-inclination a~44 au "kernel" population and a dynamically cold population extending beyond the 2:1 resonance. We finely quantify the survey's observational biases. Our survey simulator provides a straightforward way to impose these biases on models of the trans-Neptunian orbit distributions, allowing statistical comparison to the discoveries. The OSSOS TNOs, unprecedented in their orbital precision for the size of the sample, are ideal for testing concepts of the history of giant planet migration in the solar system.
We report the discovery, tracking, and detection circumstances for 85 trans-Neptunian objects (TNOs) from the first 42deg^2^ of the Outer Solar System Origins Survey. This ongoing r-band solar system survey uses the 0.9deg^2^ field of view MegaPrime camera on the 3.6m Canada-France-Hawaii Telescope. Our orbital elements for these TNOs are precise to a fractional semimajor axis uncertainty <0.1%. We achieve this precision in just two oppositions, as compared to the normal three to five oppositions, via a dense observing cadence and innovative astrometric technique. These discoveries are free of ephemeris bias, a first for large trans-Neptunian surveys. We also provide the necessary information to enable models of TNO orbital distributions to be tested against our TNO sample. We confirm the existence of a cold "kernel" of objects within the main cold classical Kuiper Belt and infer the existence of an extension of the "stirred" cold classical Kuiper Belt to at least several au beyond the 2:1 mean motion resonance with Neptune. We find that the population model of Petit et al. remains a plausible representation of the Kuiper Belt. The full survey, to be completed in 2017, will provide an exquisitely characterized sample of important resonant TNO populations, ideal for testing models of giant planet migration during the early history of the solar system.
The U.S. Naval Observatory is in the process of making new reductions of the Astrographic Catalogue (AC) using a modern reference system, the ACRS, which represents the system of the FK5. The data from the Oxford 2 Zone, whose plates are centered between declinations +32 and +33 degrees (eq. 1900), have been analyzed for scale, rotation, tilt, coma, magnitude equation, radial distortion and distortions introduced by the use of reseaux in the Carte du Ciel program. The result is a positional catalog of over 117,000 stars on eq. J2000.0, epoch of observation. Additionally, all stars have been matched with the Tycho Input Catalog (revised); those numbers have been added for additional identification purposes.
The U.S. Naval Observatory is in the process of making new reductions of the Astrographic Catalogue (AC) using a modern reference system, the ACRS, which represents the system of the FK5. The data from the Oxford 1 Zone, whose plates are centered between declinations +25 and +31 degrees (eq. 1900), have been analyzed for scale, rotation, tilt, coma, magnitude equation, radial distortion and distortions introduced by the use of reseaux in the Carte du Ciel program. The result is a positional catalog of over 277,000 stars on eq. J2000.0, epoch of observation. Additionally, all stars have been matched with the Tycho Input Catalog (revised); those numbers have been added for additional identification purposes.
Deep far-infrared photometric surveys studying galaxy evolution and the nature of the cosmic infrared background are a key strength of the Herschel mission. We describe the scientific motivation for the PACS Evolutionary Probe (PEP) guaranteed time key program and its role within the entire set of Herschel surveys, and the field selection that includes popular multiwavelength fields such as GOODS, COSMOS, Lockman Hole (LH), ECDFS (Extended Chandra Deep Field South), and EGS (Extended Groth Strip). We present results from the deepest Herschel-PACS (Photodetector Array Camera and Spectrometer) far-infrared blank field extragalactic survey, obtained by combining observations of the GOODS (Great Observatories Origins Deep Survey) fields from the PACS Evolutionary Probe (PEP) and GOODS-Herschel key programmes.
We study quasar clustering on small scales, modeling clustering amplitudes using halo-driven dark matter descriptions. From 91 pairs n scales <35h^-1^kpc, we detect only a slight excess in quasar clustering over our best-fit large-scale model. Integrated across all redshifts, the implied quasar bias is bQ=4.21+/-0.98 (bQ=3.93+/-0.71) at ~18h^-1^kpc (~28h^-1^kpc).
We present the Palermo Swift-BAT hard X-ray catalogue obtained from the analysis of the the data relative to the first 39 months of the Swift mission. We have developed a dedicated software to perform data reduction, mosaicking and source detection on the BAT survey data. We analyzed the BAT dataset in three energy bands (14-150keV, 14-30keV, 14-70keV), obtaining a list of 962 detections above a significance threshold of 4.8 standard deviations. The identification of the source counterparts was pursued using three strategies: cross-correlation with published hard X-ray catalogues, analysis of field observations of soft X-ray instruments, cross-correlation with the SIMBAD database. The survey covers 90% of the sky down to a flux limit of 2.5x10^-11^erg/cm^2^/s and 50% of the sky down to a flux limit of 1.8x10^-11^erg/cm^2^/s in the 14-150keV band. We derived a catalogue of 754 identified sources, of which ~69% are extragalactic, ~27% are Galactic objects, ~4% are already known X-ray or gamma ray emitters whose nature has not been determined yet. The integrated flux of the extragalactic sample is ~1% of the Cosmic X-ray background in the 14-150keV range.
We introduce the Pan-Pacific Planet Search, a survey of 170 metal-rich Southern Hemisphere subgiants using the 3.9m Anglo-Australian Telescope. We report the first discovery from this program, a giant planet orbiting 7 CMa (HD 47205) with a period of 763+/-17 days, eccentricity e=0.14+/-0.06, and msin i=2.6+/-0.6M_Jup_. The host star is a K giant with a mass of 1.5+/-0.3M_{sun}_ and metallicity [Fe/H]=0.21+/-0.10. The mass and period of 7 CMa b are typical of planets which have been found to orbit intermediate-mass stars (M_*_>1.3M_{sun}_). Hipparcos photometry shows this star to be stable to 0.0004 mag on the radial-velocity period, giving confidence that this signal can be attributed to reflex motion caused by an orbiting planet.
We present a systematic search for wide-separation (with Einstein radius ~1.5"), galaxy-scale strong lenses in the 30000 sq.deg of the Pan-STARRS 3pi survey on the Northern sky. With long time delays of a few days to weeks, these types of systems are particularly well-suited for catching strongly lensed supernovae with spatially-resolved multiple images and offer new insights on early-phase supernova spectroscopy and cosmography. We produced a set of realistic simulations by painting lensed COSMOS sources on Pan-STARRS image cutouts of lens luminous red galaxies (LRGs) with redshift and velocity dispersion known from the sloan digital sky survey (SDSS). First, we computed the photometry of mock lenses in gri bands and applied a simple catalog-level neural network to identify a sample of 1050207 galaxies with similar colors and magnitudes as the mocks. Second, we trained a convolutional neural network (CNN) on Pan-STARRS gri image cutouts to classify this sample and obtain sets of 105760 and 12382 lens candidates with scores of pCNN>0.5 and >0.9, respectively. Extensive tests showed that CNN performances rely heavily on the design of lens simulations and the choice of negative examples for training, but little on the network architecture. The CNN correctly classified 14 out of 16 test lenses, which are previously confirmed lens systems above the detection limit of Pan-STARRS. Finally, we visually inspected all galaxies with pCNN>0.9 to assemble a final set of 330 high-quality newly-discovered lens candidates while recovering 23 published systems. For a subset, SDSS spectroscopy on the lens central regions proves that our method correctly identifies lens LRGs at z~0.1-0.7. Five spectra also show robust signatures of high-redshift background sources, and Pan-STARRS imaging confirms one of them as a quadruply-imaged red source at z_s_=1.185, which is likely a recently quenched galaxy strongly lensed by a foreground LRG at z_d_=0.3155. In the future, high-resolution imaging and spectroscopic follow-up will be required to validate Pan-STARRS lens candidates and derive strong lensing models. We also expect that the efficient and automated two-step classification method presented in this paper will be applicable to the ~4 mag deeper gri stacks from the Rubin Observatory Legacy Survey of Space and Time (LSST) with minor adjustments.
