Search Publications
The XXL Survey. XVI. The clustering of X-ray selected galaxy clusters at z 0.3
Altieri, B.; Valtchanov, I.; Lidman, C. +20 more
Context. Galaxy clusters trace the highest density peaks in the large-scale structure of the Universe. Their clustering provides a powerful probe that can be exploited in combination with cluster mass measurements to strengthen the cosmological constraints provided by cluster number counts.
Aims: We investigate the spatial properties of a hom…
High-contrast imaging of HD 163296 with the Keck/NIRC2 L'-band vortex coronograph
Absil, O.; Guidi, G.; Testi, L. +16 more
We present observations of the nearby (D∼100 pc) Herbig star HD 163296 taken with the vortex coronograph at Keck/NIRC2 in the L' band (3.7 µm) to search for planetary mass companions in the ringed disc surrounding this pre-main-sequence star. The images reveal an arc-like region of scattered light from the disc surface layers that is likely …
The Charge State of Polycyclic Aromatic Hydrocarbons across a Reflection Nebula, an H II Region, and a Planetary Nebula
Boersma, C.; Allamandola, L. J.; Bregman, J.
Low-resolution Spitzer-IRS spectral map data of a reflection nebula (NGC 7023), H II region (M17), and planetary nebula (NGC 40), totaling 1417 spectra, are analyzed using the data and tools available through the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbon (PAH) emission is broken down into PAH charge and size subc…
Accretion Disk Size Measurement and Time Delays in the Lensed Quasar WFI 2033-4723
Kochanek, Christopher S.; Bonvin, Vivien; Courbin, Frederic +5 more
We present 13 seasons of R-band photometry of the quadruply lensed quasar WFI 2033-4723 from the 1.3 m SMARTS telescope at CTIO and the 1.2 m Euler Swiss Telescope at La Silla, in which we detect microlensing variability of ∼0.2 mag on a timescale of ∼6 years. Using a Bayesian Monte Carlo technique, we analyze the microlensing signal to obtain a m…
Extreme submillimetre starburst galaxies
Rowan-Robinson, M.; Clements, David L.; Pearson, William J. +6 more
We have used two catalogues, a Herschel catalogue selected at 500 µm (HerMES) and an IRAS catalogue selected at 60 µm (RIFSCz), to contrast the sky at these two wavelengths. Both surveys demonstrate the existence of "extreme" starbursts, with star-formation rates (SFRs) > 5000 M⊙ yr-1. The maximum intrinsic sta…
Astrometric effects of gravitational wave backgrounds with non-Einsteinian polarizations
Gilmore, Gerard; Mihaylov, Deyan P.; Moore, Christopher J. +2 more
The Gaia mission offers a new opportunity to search for the low-frequency gravitational wave background using astrometric measurements. In this paper, the astrometric effect of gravitational waves is reviewed, with a particular focus on the effect of non-Einsteinian gravitational wave polarizations. A stochastic gravitational wave background gener…
Nearby High-speed Stars in Gaia DR2
Geller, Margaret J.; Brown, Warren R.; Kenyon, Scott J. +1 more
We investigate the nature of nearby (10-15 kpc) high-speed stars in the Gaia DR2 archive identified on the basis of parallax, proper motion and radial velocity. Together with a consideration of their kinematic, orbital, and photometric properties, we develop a novel strategy for evaluating whether high-speed stars are statistical outliers of the b…
On the Stellar Velocity Distribution in the Solar Neighborhood in Light of Gaia DR2
Pérez-Villegas, Angeles; Barros, Douglas A.; Michtchenko, Tatiana A. +2 more
The aim of this Letter is to contribute to the understanding of the stellar velocity distribution in the solar neighborhood (SN). We propose that the structures on the U-V planes, known as the moving groups, can be mainly explained by the spiral arms perturbations. The applied model of the Galactic disk and spiral arms, with the parameters defined…
Recoiling Supermassive Black Hole in Changing-look AGN Mrk 1018
Kim, D. -C.; Evans, A. S.; Yoon, Ilsang
The spectral type of Mrk 1018 changed from Type 1.9 to 1 and returned back to 1.9 over a period of 40 years. We have investigated physical mechanisms responsible for the spectral change in Mrk 1018 by analyzing archival spectral and imaging data. Two kinematically distinct broad-line components, blueshifted and redshifted components, are found fro…
Parameterizations of Chromospheric Condensations in dG and dMe Model Flare Atmospheres
Kowalski, Adam F.; Allred, Joel C.
The origin of the near-ultraviolet and optical continuum radiation in flares is critical for understanding particle acceleration and impulsive heating in stellar atmospheres. Radiative-hydrodynamic (RHD) simulations in 1D have shown that high energy deposition rates from electron beams produce two flaring layers at T ∼ 104 K that develo…