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Jenness T.,Joint Astronomy Center | Robson E.I.,Astronomy Technology Center | Stevens J.A.,University of Hertfordshire
Monthly Notices of the Royal Astronomical Society | Year: 2010

Calibrated data for 143 flat-spectrum extragalactic radio sources are presented at a wavelength of 850 μm covering a 5-yr period from 2000 April. The data, obtained at the James Clerk Maxwell Telescope using the Submillimetre Common-User Bolometer Array (SCUBA) camera in pointing mode, were analysed using an automated pipeline process based on the Observatory Reduction and Acquisition Control - Data Reduction (ORAC-DR) system. This paper describes the techniques used to analyse and calibrate the data, and presents the data base of results along with a representative sample of the better-sampled light curves. A re-analysis of previously published data from 1997 to 2000 is also presented. The combined catalogue, comprising 10 493 flux density measurements, provides a unique and valuable resource for studies of extragalactic radio sources. © 2009 RAS.


Varricatt W.P.,Joint Astronomy Center | Davis C.J.,Joint Astronomy Center | Ramsay S.,European Southern Observatory | Todd S.P.,Astronomy Technology Center
Monthly Notices of the Royal Astronomical Society | Year: 2010

We have carried out a near-infrared imaging survey of luminous young stellar outflow candidates using the United Kingdom Infrared Telescope. Observations were obtained through the broad-band K (2.2 μm) and narrow-band filters at the wavelengths of H2 v = 1-0 S(1) (2.1218 μm) and Brγ (2.166 μm) lines. 50 regions were imaged with a field of view of 2.2 × 2.2 arcmin2. Several young embedded clusters are unveiled in our near-infrared images. 76 per cent of the objects exhibit H2 emission and 50 per cent or more of the objects exhibit aligned H2 emission features suggesting collimated outflows, many of which are new detections. These observations suggest that disc accretion is probably the leading mechanism in the formation of stars, at least up to late O spectral types. The young stellar objects (YSOs) responsible for many of these outflows are positively identified in our images based on their locations with respect to the outflow lobes, Two-Micron All-Sky Survey colours and association with Midcourse Space Experiment, Infrared Astronomical Satellite, millimetre and radio sources. The close association of molecular outflows detected in CO with the H2 emission features produced by shock excitation by jets from the YSOs suggests that the outflows from these objects are jet-driven. Towards strong radio emitting sources, H2 jets were either not detected or were weak when detected, implying that most of the accretion happens in the pre-ultracompact (pre-UC) H ii phase; accretion and outflows are probably weak when the YSO has advanced to its UC H ii stage. © 2010 The Authors. Journal compilation © 2010 RAS.


Leech J.,University of Oxford | Isaak K.G.,University of Cardiff | Papadopoulos P.P.,Argelander Institute For Astronomie | Gao Y.,Chinese Academy of Sciences | Davis G.R.,Joint Astronomy Center
Monthly Notices of the Royal Astronomical Society | Year: 2010

Luminous infrared galaxies (LIR > 1011 L⊙) are often associated with interacting galactic systems and are thought to be powered by merger-induced starbursts and/or dust-enshrouded active galactic nucleus. In such systems, the evolution of the dense, star-forming molecular gas as a function of merger separation is of particular interest. Here, we present observations of the CO(3-2) emission from a sample of luminous infrared galaxy mergers that span a range of galaxy-galaxy separations. The excitation of the molecular gas is studied by examining the CO(3-2)/CO(1-0) line ratio, r31, as a function of merger extent. We find these line ratios, r31, to be consistent with kinetic temperatures of Tk = (30-50) K and gas densities of We also find weak correlations between r31 and both merger progression and star formation efficiency [LFIR/LCO(1-0)]. These correlations show a tendency for gas excitation to increase as the merger progresses and the star formation efficiency rises. To conclude, we calculate the contributions of the CO(3-2) line to the 850-μm fluxes measured with SCUBA (Submillimetre Common-User Bolometer Array), which are seen to be significant (∼22 per cent). © 2010 The Authors. Journal compilation © 2010 RAS.


Long-slit spectroscopy observations of Uranus by the United Kingdom InfraRed Telescope UIST instrument in 2006, 2007 and 2008 have been used to monitor the change in Uranus' vertical and latitudinal cloud structure through the planet's Northern Spring Equinox in December 2007.These spectra were analysed and presented by Irwin et al. (Irwin, P.G.J., Teanby, N.A., Davis, G.R. [2009]. Icarus 203, 287-302), but since publication, a new set of methane absorption data has become available (Karkoschka, E., Tomasko, M. [2010]. Methane absorption coefficients for the jovian planets from laboratory, Huygens, and HST data. Icarus 205, 674-694.), which appears to be more reliable at the cold temperatures and high pressures of Uranus' deep atmosphere. We have fitted k-coefficients to these new methane absorption data and we find that although the latitudinal variation and inter-annual changes reported by Irwin et al. (2009) stand, the new k-data place the main cloud deck at lower pressures (2-3. bars) than derived previously in the H-band of ∼3-4. bars and ∼3. bars compared with ∼6. bars in the J-band. Indeed, we find that using the new k-data it is possible to reproduce satisfactorily the entire observed centre-of-disc Uranus spectrum from 1 to 1.75μm with a single cloud at 2-3. bars provided that we make the particles more back-scattering at wavelengths less than 1.2μm by, for example, increasing the assumed single-scattering albedo from 0.75 (assumed in the J and H-bands) to near 1.0. In addition, we find that using a deep methane mole fraction of 4% in combination with the associated warm 'F' temperature profile of Lindal et al. (Lindal, G.F., Lyons, J.R., Sweetnam, D.N., Eshleman, V.R., Hinson, D.P. [1987]. J. Geophys. Res. 92, 14987-15001), the retrieved cloud deck using the new (Karkoschka and Tomasko, 2010) methane absorption data moves to between 1 and 2. bars. The same methane absorption data and retrieval algorithm were applied to observations of Neptune made during the same programme and we find that we can again fit the entire 1-1.75μm centre-of-disc spectrum with a single cloud model, providing that we make the stratospheric haze particles (of much greater opacity than for Uranus) conservatively scattering (i.e ω=1) and we also make the deeper cloud particles, again at around the 2. bar level more reflective for wavelengths less than 1.2μm. Hence, apart from the increased opacity of stratospheric hazes in Neptune's atmosphere, the deeper cloud structure and cloud composition of Uranus and Neptune would appear to be very similar. © 2010 Elsevier Inc.


Varricatt W.P.,Joint Astronomy Center
Astronomy and Astrophysics | Year: 2011

Aims. We seek to understand the way massive stars form. The case of a luminous YSO IRAS 17527-2439 is studied in the infrared. Methods. Imaging observations of IRAS 17527-2439 are obtained in the near-IR JHK photometric bands and in a narrow-band filter centred at the wavelength of the H2 1-0S(1) line. The continuum-subtracted H2 image is used to identify outflows. The data obtained in this study are used in conjunction with Spitzer, AKARI, and IRAS data. The YSO driving the outflow is identified in the Spitzer images. The spectral energy distribution (SED) of the YSO is studied using available radiative transfer models. Results. A parsec-scale bipolar outflow is discovered in our H2 line image, which is supported by the detection in the archival Spitzer images. The H2 image exhibits signs of precession of the main jet and shows tentative evidence for a second outflow. These suggest the possibility of a companion to the outflow source. There is a strong component of continuum emission in the direction of the outflow, which supports the idea that the outflow cavity provides a path for radiation to escape, thereby reducing the radiation pressure on the accreted matter. The bulk of the emission observed close to the outflow in the WFCAM and Spitzer bands is rotated counter clockwise with respect to the outflow traced in H2, which may be due to precession. A model fit to the SED of the central source tells us that the YSO has a mass of 12.23 M⊙ and that it is in an early stage of evolution. © 2011 ESO.


Varricatt W.P.,Joint Astronomy Center
Astronomy and Astrophysics | Year: 2012

The luminous young stellar object (YSO) IRAS 07422-2001 is studied in the infrared (IR). We discover star forming activity in embedded clusters located in a cloud detected at mid-IR wavelengths in emission. Multiple outflows are discovered from these clusters in the H 2 ro-vibrational line at 2.122 μm. We detect at least six outflows from the cluster associated with the IRAS source and another outflow from a source located in a cluster detected ∼2.7 arcmin NE of the IRAS source. Additional star formation is taking place in two other cluster candidates within the cloud. Three of the YSOs in the cluster associated with the IRAS source are detected at 11.2 μm at an angular resolution of ∼0.8′′. We have a tentative detection of a circumstellar disk in this cluster, seen as an extinction lane in the J and H-band images. The spectral energy distributions (SEDs) of the dominant YSOs in the cluster associated with the IRAS source and in the NE cluster are studied using radiative transfer models and the properties of the YSOs are estimated. The YSO associated with the IRAS source is probably in a very early Class I stage of formation. The source identified as the dominant YSO in the NE cluster appears to be older than the dominant YSO in the cluster associated with the IRAS source, but its observed flux seems to be contaminated by extra emission, which suggests the presence of a young source contributing to the SED at far-IR wavelengths. The star formation observed in the field of IRAS 07422-2001 supports the idea of hierarchical formation of massive star clusters and the growth of massive young stellar objects near the centres of multiple sub-clusters in a star forming clump through competitive accretion. © 2012 ESO.


Dempsey J.T.,Joint Astronomy Center | Thomas H.S.,Joint Astronomy Center | Currie M.J.,Joint Astronomy Center
Astrophysical Journal, Supplement Series | Year: 2013

We present the first release (R1) of data from the CO High-Resolution Survey (COHRS), which maps a strip of the inner Galactic plane in 12CO (J = 3 → 2). The data are taken using the Heterodyne Array Receiver Programme on the James Clerk Maxwell Telescope (JCMT) in Hawaii, which has a 14 arcsec angular resolution at this frequency. When complete, this survey will cover |b| ≤ 0.°5 between 10° < l < 65°. This first release covers |b| ≤ 0.°5 between 10.°25 < l < 17.°5 and 50.°25 < l < 55.°25, and |b| ≤ 0.°25 between 17.°5 < l < 50.°25. The data are smoothed to a velocity resolution of 1 km s-1, a spatial resolution of 16 arcsec and achieve a mean rms of ∼1 K. COHRS data are available to the community online at http://dx.doi.org/10.11570/13.0002. In this paper we describe the data acquisition and reduction techniques used and present integrated intensity images and longitude-velocity maps. We also discuss the noise characteristics of the data. The high resolution is a powerful tool for morphological studies of bubbles and filaments while the velocity information shows the spiral arms and outflows. These data are intended to complement both existing and upcoming surveys, e.g., the Bolocam Galactic Plane Survey (BGPS), ATLASGAL, the Herschel Galactic Plane Survey (Hi-GAL) and the JCMT Galactic Plane Survey with SCUBA-2 (JPS). © 2013. The American Astronomical Society. All rights reserved.


Jenness T.,Joint Astronomy Center | Economou F.,Joint Astronomy Center
Astronomy and Computing | Year: 2015

ORAC-DR is a general purpose data reduction pipeline system designed to be instrument and observatory agnostic. The pipeline works with instruments as varied as infrared integral field units, imaging arrays and spectrographs, and sub-millimeter heterodyne arrays and continuum cameras. This paper describes the architecture of the pipeline system and the implementation of the core infrastructure. We finish by discussing the lessons learned since the initial deployment of the pipeline system in the late 1990s. © 2014 The Authors.


Berry D.S.,Joint Astronomy Center
Astronomy and Computing | Year: 2015

This paper describes the FellWalker algorithm, a watershed algorithm that segments a 1-, 2- or 3-dimensional array of data values into a set of disjoint clumps of emission, each containing a single significant peak. Pixels below a nominated constant data level are assumed to be background pixels and are not assigned to any clump. FellWalker is thus equivalent in purpose to the CLUMPFIND algorithm. However, unlike CLUMPFIND, which segments the array on the basis of a set of evenly-spaced contours and thus uses only a small fraction of the available data values, the FellWalker algorithm is based on a gradient-tracing scheme which uses all available data values. Comparisons of CLUMPFIND and FellWalker using a crowded field of artificial Gaussian clumps, all of equal peak value and width, suggest that the results produced by FellWalker are less dependent on specific parameter settings than are those of CLUMPFIND. © 2014 The Author.


Oliveira F.J.,Joint Astronomy Center
International Journal of Theoretical Physics | Year: 2014

In this paper the four-dimensional (4-D) space-velocity Cosmological General Relativity of Carmeli is developed by a general solution of the Einstein field equations. The Tolman metric is applied in the form (formula presented) where gμν is the metric tensor. We use comoving coordinates xα = (x0, x1, x2, x3) = (τv, r, θ, ϕ), where τ is the Hubble-Carmeli time constant, v is the universe expansion velocity and r, θ and ϕ are the spatial coordinates. We assume that μ and R are each functions of the coordinates τv and r.The vacuum mass density ρΛ is defined in terms of a cosmological constant Λ, (formula presented) where the Carmeli gravitational coupling constant κ = 8πG/c2τ2, where c is the speed of light in vacuum. This allows the definitions of the effective mass density (formula presented) and effective pressure (formula presented) where ρ is the mass density and pis the pressure. Then the energy-momentum tensor (formula presented) where uμ = (1,0,0,0) is the 4-velocity. The Einstein field equations are taken in the form (formula presented) where Rμν is the Ricci tensor, κ = 8πG/c2τ2 is Carmeli’s gravitation constant, where G is Newton’s constant and the trace T = gαβTαβ. By solving the field equations (6) a space-velocity cosmology is obtained analogous to the Friedmann-Lemaître-Robertson-Walker space-time cosmology.We choose an equation of state such that (formula presented) with an evolving state parameter (formula presented) where Rv = Rv(v) is the scale factor and w0 and wa are constants.Carmeli’s 4-D space-velocity cosmology is derived as a special case. © 2014, Springer Science+Business Media New York.

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