Search Publications
Measuring Flexion
Goldberg, David M.; Leonard, Adrienne
We describe practical approaches to measuring flexion in observed galaxies. In particular, we look at the issues involved in using the shapelets and HOLICs techniques as means of extracting second-order lensing information. We also develop an extension of HOLICs to estimate flexion in the presence of noise and with a nearly isotropic PSF. We test …
Gemini GMOS/integral field unit spectroscopy of NGC 1569 - II. Mapping the roots of the galactic outflow
Gallagher, J. S.; Smith, L. J.; Westmoquette, M. S. +1 more
We present a set of four Gemini-North Multi-Object Spectrograph/integral field unit (IFU) observations of the central disturbed regions of the dwarf irregular starburst galaxy NGC 1569, surrounding the well-known superstar clusters A and B. This continues on directly from a companion paper, in which we describe the data reduction and analysis tech…
Observations of Dark Lanes in Umbral Fine Structure from the Hinode Solar Optical Telescope: Evidence for Magnetoconvection
Bharti, Lokesh; Joshi, Chandan; Jaaffrey, S. N. A.
An analysis of high-resolution G-band images of active region NOAA 10930 is presented. The observations were recorded with the Broadband Filter Imager (BFI) attached to the Solar Optical Telescope (SOT) on board the Hinode mission. We observed dark lanes in umbral dots up to six folds in larger ones. Formation of umbral dots from dark core penumbr…
Radiative Transfer Effects on Doppler Measurements as Sources of Surface Effects in Sunspot Seismology
Scherrer, P. H.; Wachter, R.; Sankarasubramanian, K. +1 more
We show that the use of Doppler shifts of Zeeman-sensitive spectral lines to observe waves in sunspots is subject to measurement-specific phase shifts arising from (1) the altered height range of spectral line formation and the propagating character of p-mode waves in penumbrae and (2) Zeeman broadening and splitting. We also show that these phase…
Ion multi-nose structures observed by Cluster in the inner Magnetosphere
Sauvaud, J. -A.; Escoubet, C. P.; Dandouras, I. +7 more
During the last 30 years, several magnetospheric missions have recorded the presence of narrow proton structures in the ring current region. These structures have been referred as "nose-like" structures, due to their appearance when represented in energy-time spectrograms, characterized by a flux value increase for a narrow energy range.
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A nanoflare model of quiet Sun EUV emission
Solanki, S. K.; Pauluhn, A.
Nanoflares have been proposed as the main source of heating of the solar corona. However, detecting them directly has so far proved elusive, and extrapolating to them from the properties of larger brightenings gives unreliable estimates of the power-law exponent α characterising their distribution. Here we take the approach of statistically modell…
The iron K feature in narrow line Seyfert 1 galaxies: evidence for a P Cygni profile?
Done, Chris; Gierliński, Marek; Sobolewska, Małgorzata A. +1 more
Narrow line Seyfert 1 galaxies are generally accreting at high fractions of the Eddington limit. They can show complex X-ray spectra, with a strong `soft excess' below 2 keV and a sharp drop at ~7 keV. There is strong evidence linking the soft excess to either reflection or absorption from relativistic, partially ionized material close to the blac…
X-ray selected starbursts in the Great Observatories Origins Deep Survey-North
Georgakakis, A.; Georgantopoulos, I.; Rowan-Robinson, M. +1 more
We investigate claims that recent ultra-deep X-ray surveys are detecting starbursts at cosmologically interesting redshifts (z = 0-1). We combine X-ray data from the 2Ms Chandra Deep Field-North and multiwavelength observations obtained as part of the Great Observatories Origins Deep Survey (GOODS)-North to build the Spectral Energy Distributions …
A Schumann-like resonance on Titan driven by Saturn's magnetosphere possibly revealed by the Huygens Probe
Berthelier, J. J.; Krasnoselskikh, V.; López-Moreno, J. J. +9 more
The low-frequency data collected with the antenna of the Permittivity, Wave and Altimetry experiment on board the Huygens Probe that landed on Titan on 14 January 2005 have been thoroughly analyzed considering different possible natural and artificial effects. Although a definite conclusion is still subject to the outcome of complementary inquirie…
Modeling Spitzer Observations of VV Ser. I. The Circumstellar Disk of a UX Orionis Star
van Dishoeck, Ewine F.; Dullemond, Cornelis P.; Pontoppidan, Klaus M. +5 more
We present mid-infrared Spitzer IRS spectra of the UX Orionis star VV Ser, combined with interferometric and spectroscopic data from the literature covering UV to submillimeter wavelengths. The full set of data are modeled by an axisymmetric Monte Carlo radiative transfer code to test the prediction of Dullemond et al. that disks around UX Orionis…