Search Publications
Scale Dependence of Magnetic Helicity in the Solar Wind
Brandenburg, Axel; Balogh, André; Subramanian, Kandaswamy +1 more
We determine the magnetic helicity, along with the magnetic energy, at high latitudes using data from the Ulysses mission. The data set spans the time period from 1993 to 1996. The basic assumption of the analysis is that the solar wind is homogeneous. Because the solar wind speed is high, we follow the approach first pioneered by Matthaeus et al.…
Ion- and electron-acoustic solitons and double layers in multi-component space plasmas
Lakhina, G. S.; Singh, S. V.; Kakad, A. P.
A general model for the ion- and electron-acoustic solitons and double layers in a multi-component unmagnetized plasma consisting of background electrons, counter-streaming electron beams and ions is discussed. The model is based on the multi-fluid equations and the Poisson equation, and uses the Sagdeev pseudo-potential techniques. For identical …
Intermediate-age stars as the origin of low stellar velocity dispersion nuclear rings: the case of Mrk 1157
Riffel, Rogério; Storchi-Bergmann, Thaisa; Riffel, Rogemar A. +1 more
We have used the Gemini Near-Infrared Integral-Field Spectrograph to map the age distribution of the stellar population in the inner 400 pc of the Seyfert 2 galaxy Mrk 1157 (NGC 591), at a spatial resolution of 35 pc. We have performed wavelet and principal component analysis on the data in order to remove instrumental signatures. An old stellar p…
Photochemistry of polycyclic aromatic hydrocarbons in cosmic water ice. I. Mid-IR spectroscopy and photoproducts
Allamandola, L. J.; Bouwman, J.; Linnartz, H. +1 more
Context. Polycyclic aromatic hydrocarbons (PAHs) are known to be abundantly present in photon-dominated regions (PDRs), as evidenced by their ubiquitous mid-IR emission bands. Towards dense clouds, however, their IR emission bands are strongly suppressed. It is here where molecules are known to reside on very cold grains (T ≤ 30 K) in the form of …
Extreme active galactic nucleus feedback and cool-core destruction in the X-ray luminous galaxy cluster MACS J1931.8-2634
Simionescu, A.; Kelly, P.; von der Linden, A. +14 more
We report on a deep, multiwavelength study of the galaxy cluster MACS J1931.8-2634 using Chandra X-ray, Subaru optical and Very Large Array 1.4-GHz radio data. This cluster (z= 0.352) harbours one of the most X-ray luminous cool cores yet discovered, with an equivalent mass, cooling rate within the central ? is ∼700 M⊙ yr-1. …
Physical Properties of the Circumnuclear Starburst Ring in the Barred Galaxy NGC 1097
Ho, Paul T. P.; Matsushita, Satoki; Oi, Nagisa +3 more
We report high-resolution 12CO(J = 2-1), 13CO(J = 2-1), and 12CO(J = 3-2) imaging of the Seyfert 1/starburst ring galaxy NGC 1097 with the Submillimeter Array for the purpose of studying the physical and kinematic properties of the 1 kpc circumnuclear starburst ring. Individual star clusters as detected in the Hubb…
The tumultuous formation of the Hubble sequence at z > 1 examined with HST/Wide-Field Camera-3 observations of the Hubble Ultra Deep Field
Koekemoer, A. M.; Ravindranath, S.; Conselice, C. J. +5 more
We examine in this paper a stellar-mass-selected sample of galaxies at 1 < z < 3 within the Hubble Ultra Deep Field, utilizing Wide-Field Camera-3 (WFC3) imaging, to study the rest-frame optical morphological and structural distribution of galaxies at this epoch. We measure how apparent morphologies (disc, elliptical, peculiar) correlate wit…
Evidence for environmentally dependent cluster disruption in M83
Bastian, N.; Larsen, S. S.; Smith, L. J. +8 more
Using multiwavelength imaging from the Wide Field Camera 3 on the Hubble Space Telescope we study the stellar cluster populations of two adjacent fields in the nearby face-on spiral galaxy, M83. The observations cover the galactic centre and reach out to ∼6 kpc, thereby spanning a large range of environmental conditions, ideal for testing empirica…
Variability of southern and northern periodicities of Saturn Kilometric Radiation
Lamy, L.
Among the persistent questions raised by the existence of a rotational modulation of the Saturn Kilometric Radiation (SKR), the origin of the variability of the 10.8 hours SKR period at a 1% level over weeks to years remains intriguing. While its short-term fluctuations (20-30 days) have been related to the variations of the solar wind speed, its …
Quasi-periodic polar flares at Jupiter: A signature of pulsed dayside reconnections?
Bonfond, B.; Vogt, M. F.; Gérard, J. -C. +3 more
The most dynamic part of the Jovian UV aurora is located inside the main auroral oval. This region is known to regularly show localized but dramatic enhancements on timescales of several tens of seconds, called polar flares. They have often been associated with the polar cusp, based on their location in the polar cap. The present study is based on…