The Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the... Show moreThe Planet Formation Imager (PFI) project aims to provide a strong scientific vision for ground-based optical astronomy beyond the upcoming generation of Extremely Large Telescopes. We make the case that a breakthrough in angular resolution imaging capabilities is required in order to unravel the processes involved in planet formation. PFI will be optimised to provide a complete census of the protoplanet population at all stellocentric radii and over the age range from 0.1 to 100 Myr. Within this age period, planetary systems undergo dramatic changes and the final architecture of planetary systems is determined. Our goal is to study the planetary birth on the natural spatial scale where the material is assembled, which is the "Hill Sphere" of the forming planet, and to characterise the protoplanetary cores by measuring their masses and physical properties. Our science working group has investigated the observational characteristics of these young protoplanets as well as the migration mechanisms that might alter the system architecture. We simulated the imprints that the planets leave in the disk and study how PFI could revolutionise areas ranging from exoplanet to extragalactic science. In this contribution we outline the key science drivers of PFI and discuss the requirements that will guide the technology choices, the site selection, and potential science/technology tradeoffs. Show less
This Research Note presents the outcome of an investigation into the processes of lone-actor terrorism which was part of the Countering Lone-Actor Terrorism (CLAT) Project. The research is based... Show moreThis Research Note presents the outcome of an investigation into the processes of lone-actor terrorism which was part of the Countering Lone-Actor Terrorism (CLAT) Project. The research is based on a database of both plots and attacks across the twenty-eight EU member states, plus Norway and Switzerland, in the period 1 January 2000 to 31 December 2014. The database covers more than 70 variables and includes information relating to 120 individuals. This Research Note outlines some of the key findings of the CLAT project pertaining to 1) attack methodology and logistics; 2) political engagement and online activity and 3) leakage and interactions with authorities. The results relating to the personal characteristics of lone-actor terrorists are presented in a different Research Note in this issue of Perspectives on Terrorism. Show less
Using the IRAM Plateau de Bure interferometer (PdBI), we report the detection of water vapor in six new lensed ultra-luminous starburst galaxies at high redshift, discovered in the Herschel... Show moreUsing the IRAM Plateau de Bure interferometer (PdBI), we report the detection of water vapor in six new lensed ultra-luminous starburst galaxies at high redshift, discovered in the Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS). The sources are detected either in the 2$_{02}$-1$_{11}$ or 2$_{11}$-2$_{02}$ H$_{2}$O emission lines with integrated line fluxes ranging from 1.8 to 14 Jy km s$^{-1}$. The corresponding apparent luminosities are {$μ$}L$_{H2}$O ~{} 3-12 { imes} 10$^{8}$ L$_{⊙}$, where {$μ$} is the lensing magnification factor (3 {lt} {$μ$} {lt} 12). These results confirm that H$_{2}$O lines are among the strongest molecular lines in high-z ultra-luminous starburst galaxies, with intensities almost comparable to those of the high-J CO lines, and similar profiles and line widths (~{}200-900 km s$^{-1}$). With the current sensitivity of the PdBI, the water lines can therefore easily be detected in high-z lensed galaxies (with F(500 {$μ$}m) {gt} 100 mJy) discovered in the Herschel surveys. Correcting the luminosities for amplification, using existing lensing models, L$_{H2}$O is found to have a strong dependence on the infrared luminosity, varying as ~{}L$_{IR}$$^{1.2}$. This relation, which needs to be confirmed with better statistics, may indicate a role of radiative (infrared) excitation of the H$_{2}$O lines, and implies that high-z galaxies with L$_{IR}$ {gsim} 10$^{13}$ L$_{⊙}$ tend to be very strong emitters in water vapor, that have no equivalent in the local universe. Herschel (Pilbratt et al. 2010) is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. Show less
Ivison, R.; Swinbank, A.; Smail, I.; Harris, A.; Bussmann, R.; Cooray, A.; ... ; Werf, P.P. van der 2013
Panchromatic observations of the best candidate hyperluminous infrared galaxies from the widest Herschel extragalactic imaging survey have led to the discovery of at least four intrinsically... Show morePanchromatic observations of the best candidate hyperluminous infrared galaxies from the widest Herschel extragalactic imaging survey have led to the discovery of at least four intrinsically luminous z = 2.41 galaxies across an {ap}100 kpc region{mdash}a cluster of starbursting protoellipticals. Via subarcsecond interferometric imaging we have measured accurate gas and star formation surface densities. The two brightest galaxies span ~{}3 kpc FWHM in submillimeter/radio continuum and CO J = 4-3, and double that in CO J = 1-0. The broad CO line is due partly to the multitude of constituent galaxies and partly to large rotational velocities in two counter-rotating gas disks{mdash}a scenario predicted to lead to the most intense starbursts, which will therefore come in pairs. The disks have M $_{dyn}$ of several { imes} 10$^{11}$ M $_{⊙}$, and gas fractions of ~{}40%. Velocity dispersions are modest so the disks are unstable, potentially on scales commensurate with their radii: these galaxies are undergoing extreme bursts of star formation, not confined to their nuclei, at close to the Eddington limit. Their specific star formation rates place them {gt}~{} 5 { imes} above the main sequence, which supposedly comprises large gas disks like these. Their high star formation efficiencies are difficult to reconcile with a simple volumetric star formation law. N-body and dark matter simulations suggest that this system is the progenitor of a B(inary)-type {ap}10$^{14.6}$-M $_{⊙}$ cluster. Show less
Thacker, C.; Cooray, A.; Smidt, J.; De Bernardis, F.; Mitchell-Wynne, K.; Amblard, A.; ... ; Werf, P.P. van der 2013
We present a measurement of the angular power spectrum of the cosmic far-infrared background (CFIRB) anisotropies in one of the extragalactic fields of the Herschel Astrophysical Terahertz Large... Show moreWe present a measurement of the angular power spectrum of the cosmic far-infrared background (CFIRB) anisotropies in one of the extragalactic fields of the Herschel Astrophysical Terahertz Large Area Survey at 250, 350, and 500 {$μ$}m bands. Consistent with recent measurements of the CFIRB power spectrum in Herschel-SPIRE maps, we confirm the existence of a clear one-halo term of galaxy clustering on arcminute angular scales with large-scale two-halo term of clustering at 30 arcmin to angular scales of a few degrees. The power spectrum at the largest angular scales, especially at 250 {$μ$}m, is contaminated by the Galactic cirrus. The angular power spectrum is modeled using a conditional luminosity function approach to describe the spatial distribution of unresolved galaxies that make up the bulk of the CFIRB. Integrating over the dusty galaxy population responsible for the background anisotropies, we find that the cosmic abundance of dust, relative to the critical density, to be between {$Omega$}$_{dust}$ = 10$^{-6}$ and 8 { imes} 10$^{-6}$ in the redshift range z ~{} 0-3. This dust abundance is consistent with estimates of the dust content in the universe using quasar reddening and magnification measurements in the Sloan Digital Sky Survey. Show less
Bussmann, R.; Pérez-Fournon, I.; Amber, S.; Calanog, J.; Gurwell, M.; Dannerbauer, H.; ... ; Wilner, D. 2013
Strong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and... Show moreStrong gravitational lenses are now being routinely discovered in wide-field surveys at (sub-)millimeter wavelengths. We present Submillimeter Array (SMA) high-spatial resolution imaging and Gemini-South and Multiple Mirror Telescope optical spectroscopy of strong lens candidates discovered in the two widest extragalactic surveys conducted by the Herschel Space Observatory: the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS) and the Herschel Multi-tiered Extragalactic Survey (HerMES). From a sample of 30 Herschel sources with S $_{500}$ {gt} 100 mJy, 21 are strongly lensed (i.e., multiply imaged), 4 are moderately lensed (i.e., singly imaged), and the remainder require additional data to determine their lensing status. We apply a visibility-plane lens modeling technique to the SMA data to recover information about the masses of the lenses as well as the intrinsic (i.e., unlensed) sizes (r $_{half}$) and far-infrared luminosities (L $_{FIR}$) of the lensed submillimeter galaxies (SMGs). The sample of lenses comprises primarily isolated massive galaxies, but includes some groups and clusters as well. Several of the lenses are located at z $_{lens}$ {gt} 0.7, a redshift regime that is inaccessible to lens searches based on Sloan Digital Sky Survey spectroscopy. The lensed SMGs are amplified by factors that are significantly below statistical model predictions given the 500 {$μ$}m flux densities of our sample. We speculate that this may reflect a deficiency in our understanding of the intrinsic sizes and luminosities of the brightest SMGs. The lensed SMGs span nearly one decade in L $_{FIR}$ (median L $_{FIR}$ = 7.9 { imes} 10$^{12}$ L $_{☉}$) and two decades in FIR luminosity surface density (median {$Sigma$}$_{FIR}$ = 6.0 { imes} 10$^{11}$ L $_{☉}$ kpc$^{–2}$). The strong lenses in this sample and others identified via (sub-)mm surveys will provide a wealth of information regarding the astrophysics of galaxy formation and evolution over a wide range in redshift. IMAGING OF HERSCHEL Show less
