We present ALMA mosaic observations at 1.3 mm (223 GHz) of the Fomalhaut system with a sensitivity of 14 Jy/beam. These observations provide the first millimeter map of the continuum dust emission ...from the complete outer debris disk with uniform sensitivity, enabling the first conclusive detection of apocenter glow. We adopt an MCMC modeling approach that accounts for the eccentric orbital parameters of a collection of particles within the disk. The outer belt is radially confined with an inner edge of 136.3 0.9 au and width of 13.5 1.8 au. We determine a best-fit eccentricity of 0.12 0.01. Assuming a size distribution power-law index of q = 3.46 0.09, we constrain the dust absorptivity power-law index β to be 0.9 < β < 1.5. The geometry of the disk is robustly constrained with inclination 65 6 0 3, position angle 337 9 0 3, and argument of periastron 22 5 4 3. Our observations do not confirm any of the azimuthal features found in previous imaging studies of the disk with Hubble Space Telescope, SCUBA, and ALMA. However, we cannot rule out structures ≤10 au in size or that only affect smaller grains. The central star is clearly detected with a flux density of 0.75 0.02 mJy, significantly lower than predicted by current photospheric models. We discuss the implications of these observations for the directly imaged Fomalhaut b and the inner dust belt detected at infrared wavelengths.
The Submillimetre Common User Bolometer Array 2 (SCUBA-2) is an instrument operating on the 15-m James Clerk Maxwell Telescope, nominally consisting of 5120 bolometers in each of two simultaneous ...imaging bands centred over 450 and 850 μm. The camera is operated by scanning across the sky and recording data at a rate of 200 Hz. As the largest of a new generation of multiplexed kilopixel bolometer cameras operating in the (sub)millimetre, SCUBA-2 data analysis represents a significant challenge. We describe the production of maps using smurf (Sub-Millimetre User Reduction Facility) in which we have adopted a fast, iterative approach to map-making that enables data reduction on single, modern, high-end desktop computers, with execution times that are typically shorter than the observing times. smurf is used in an automated setting, both at the telescope for real-time feedback to observers and for the production of science products for the JCMT Science Archive at the Canadian Astronomy Data Centre. Three detailed case studies are used to: (i) explore convergence properties of the map-maker using simple prior constraints (Uranus - a point source); (ii) achieve the white-noise limit for faint point-source studies (extragalactic blank-field survey of the Lockman Hole); and (iii) demonstrate that our strategy is capable of recovering angular scales comparable to the size of the array footprint (approximately 5 arcmin) for bright extended sources (star-forming region M17).
ABSTRACT We present far-infrared and submillimeter maps from the Herschel Space Observatory and the James Clerk Maxwell Telescope of the debris disk host star AU Microscopii. Disk emission is ...detected at 70, 160, 250, 350, 450, 500, and 850 m. The disk is resolved at 70, 160, and 450 m. In addition to the planetesimal belt, we detect thermal emission from AU Mic's halo for the first time. In contrast to the scattered light images, no asymmetries are evident in the disk. The fractional luminosity of the disk is and its milimeter-grain dust mass is ( 20%). We create a simple spatial model that reconciles the disk spectral energy distribution as a blackbody of 53 2 K (a composite of 39 and 50 K components) and the presence of small (non-blackbody) grains which populate the extended halo. The best-fit model is consistent with the "birth ring" model explored in earlier works, i.e., an edge-on dust belt extending from 8.8 to 40 AU, but with an additional halo component with an surface density profile extending to the limits of sensitivity (140 AU). We confirm that AU Mic does not exert enough radiation force to blow out grains. For stellar mass-loss rates of 10-100 times solar, compact (zero porosity) grains can only be removed if they are very small; consistently with previous work, if the porosity is 0.9, then grains approaching 0.1 m can be removed via corpuscular forces (i.e., the stellar wind).
MS 0451.6−0305 is a rich galaxy cluster whose strong lensing is particularly prominent at submm wavelengths. We combine new Submillimetre Common-User Bolometer Array (SCUBA)-2 data with imaging from ...Herschel Spectral and Photometric Imaging Receiver (SPIRE) and PACS and Hubble Space Telescope in order to try to understand the nature of the sources being lensed. In the region of the ‘giant submm arc’, we uncover seven multiply imaged galaxies (up from the previously known four), of which six are found to be at a redshift of z ∼ 2.9, and possibly constitute an interacting system. Using a novel forward-modelling approach, we are able to simultaneously deblend and fit spectral energy distributions to the individual galaxies that contribute to the giant submm arc, constraining their dust temperatures, far-infrared luminosities, and star formation rates (SFRs). The submm arc first identified by SCUBA can now be seen to be composed of at least five distinct sources, four of these within a galaxy group at z ∼ 2.9. Only a handful of lensed galaxy groups at this redshift are expected on the sky, and thus this is a unique opportunity for studying such systems in detail. The total unlensed luminosity for this galaxy group is (3.1 ± 0.3) × 1012 L⊙, which gives an unlensed SFR of (450 ± 50) M⊙ yr−1. This finding suggests that submm source multiplicity, due to physically associated groupings as opposed to chance alignment, extends to fainter flux densities than previously discovered. Many of these systems may also host optical companions undetected in the submm, as is the case here.
The James Clerk Maxwell Telescope (JCMT) has been the world’s most successful single-dish telescope at submillimetre wavelengths since it began operations in 1987. From the pioneering days of ...single-element photometers and mixers, through to the state-of-the-art imaging and spectroscopic cameras, the JCMT has been associated with a number of major scientific discoveries. Famous for the discovery of ‘SCUBA’ galaxies, which are responsible for a large fraction of the far-infrared background, the JCMT has pushed the sensitivity limits arguably more than any other facility in this most difficult of wavebands in which to observe. Closer to home, the first images of huge discs of cool debris around nearby stars gave us clues to the evolution of planetary systems, further evidence of the importance of studying astrophysics in the submillimetre region. Now approaching the 30th anniversary of the first observations, the telescope continues to carry out unique and innovative science. In this review article, we look back on some of the major scientific highlights from the past 30 years.
ABSTRACT
We present the highest resolution single-dish submillimetre observations of the detached shell source U Antliae to date. The observations were obtained at $450$ and $850\,{\mu}{\rm m}$ with ...SCUBA-2 instrument on the James Clerk Maxwell Telescope as part of the Nearby Evolved Stars Survey. The emission at $850\,{\mu}{\rm m}$ peaks at 40 arcsec with hints of a second peak seen at ∼20 arcsec. The emission can be traced out to a radius of 56 arcsec at a 3σ level. The outer peak observed at $850\,{\mu}{\rm m}$ aligns well with the peak observed at Herschel/PACS wavelengths. With the help of spectral energy distribution fitting and radiative transfer calculations of multiple-shell models for the circumstellar envelope, we explore the various shell structures and the variation of grain sizes along the in the circumstellar envelope. We determine a total shell dust mass of (2.0 ± 0.3) × 10−5 M⊙ and established that the thermal pulse that gave rise to the detached shell occurred 3500 ± 500 yr ago.
COLD DUST IN HOT REGIONS Sreenilayam, Gopika; Fich, Michel; Ade, Peter ...
The Astronomical journal,
03/2014, Volume:
147, Issue:
3
Journal Article
Peer reviewed
Open access
We mapped five massive star-forming regions with the SCUBA-2 camera on the James Clerk Maxwell Telescope. Temperature and column density maps are obtained from the SCUBA-2 450 and 850 mu m images. ...Most of the dense clumps we find have central temperatures below 20 K, with some as cold as 8 K, suggesting that they have no internal heating due to the presence of embedded protostars. This is surprising, because at the high densities inferred from these images and at these low temperatures such clumps should be unstable, collapsing to form stars and generating internal heating. The column densities at the clump centers exceed 10 super(23) cm super(-2), and the derived peak visual extinction values are from 25 to 500 mag for beta = 1.5-2.5, indicating highly opaque centers. The observed cloud gas masses range from ~10 to 10 super(3) M sub(middot in circle). The outer regions of the clumps follow an r super(-2.36+ or -0.35) density distribution, and this power-law structure is observed outside of typically 10 super(4) AU. All these findings suggest that these clumps are high-mass starless clumps and most likely contain high-mass starless cores.
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