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33 papers · 2 filters
Big Bang nucleosynthesis and the baryonic content of the universe
T. X. Thuan, Y. I. Izotov
A review of the latest measurements of the primordial abundances of the light nuclei D, 3He, 4He and 7Li is given. We discuss in particular the primordial abundance Yp of 4He as me…
Nonthermal Emission in Radio Galaxies from Simulated Relativistic Electron Transport in 3D MHD Flows
I. L. Tregillis, T. W. Jones, Dongsu Ryu
We perform a series of so-called ``synthetic observations'' on a set of 3D MHD jet simulations which explicitly include energy-dependent transport of relativistic electrons, as des…
3D MHD Simulations of Radio Galaxies Including Nonthermal Electron Transport
T. W. Jones, I. L. Tregillis, Dongsu Ryu
We report on an effort to study the connections between dynamics in simulated radio galaxy plasma flows and the properties of nonthermal electron populations carried in those flows…
HST/STIS observations of the HeII Gunn-Peterson effect towards HE 2347-4342
Alain Smette, Sara R. Heap, Gerard M. Williger +3
We present an HST STIS spectrum of the HeII Gunn-Peterson effect towards HE2347-4342. Compared to the previous HST GHRS data obtained by Reimers et al. (1997), the STIS spectrum ha…
LOWL p-mode frequencies and their variation with solar activity
Sebastián J. Jiménez-Reyes, Thierry Corbard, Pere L. Pallé +1
We present an analysis of the frequency shift and the even terms of the frequency splitting coefficients carried out using six years of LOWL data, starting in 1994. The temporal va…
Evidence for Galaxy Formation at High Redshift
T. Shanks, N. Metcalfe, R. Fong +3
We have shown previously that galaxy counts from the UV to the near-IR are well-fitted by simple evolutionary models where the space density of galaxies remains constant with look-…
Dust disks around old Pre Main-Sequence stars: HST/NICMOS2 scattered light images and modeling
J. C. Augereau, A. M. Lagrange, D. Mouillet +1
We present recent near-infrared detections of circumstellar disks around the two old PMS Herbig stars HD 141569 and HD 100546 obtained with the HST/NICMOS2 camera. They reveal exte…
Groups and clusters detection on DPOSS catalogs
E. Puddu, E. De Filippis, V. Strazzullo +5
We discuss the implementation and validation of a procedure aimed to detect groups and clusters of galaxies in DPOSS catalogs.
HEXTE Detections of Hard X-Ray Tails in Sco X-1
F. D'Amico, W. A. Heindl, R. E. Rothschild +1
We report the detection of a non-thermal hard X-ray component from Sco X-1 based upon the analysis of 20-220 keV spectra obtained with the HEXTE experiment on-board the RXTE satell…
X-Ray Bursts and Proton Captures Close to the Dripline
T. Rauscher, F. Rembges, H. Schatz +2
The hydrogen-rich accreted envelopes of neutron stars in binary systems are the site for the rapid proton capture nucleosynthethic process (rp-process), which involves nuclei close…
Spectroscopic follow up of arclets in AC114 with the VLT
J. F. Le Borgne, L. Campusano, R. Pello +5
We present the first results on the VLT/FORS-1 spectroscopic survey of amplified sources and multiple images in the lensing cluster AC114. Background sources were selected in the c…
The Cometary Blue Compact Dwarf Galaxies Mkn 59 and Mkn 71: Clues to Dwarf Galaxy Evolution?
K. G. Noeske, N. G. Guseva, K. J. Fricke +3
"Cometary" Blue Compact Dwarf Galaxies (iI,C BCDs) are characterized by off-center starbursts close to the end of an elongated dwarf irregular (dI)-like host galaxy. This may eithe…
The Influence of Interactions and Minor Mergers on the Structure of Galactic Disks: II. Results and Interpretations
U. Schwarzkopf, R. -J. Dettmar
We present the second part of a detailed statistical study focussed on the effects of tidal interactions and minor mergers on the radial and vertical disk structure of spiral galax…
Low and High Frequency Quasi-Periodic Oscillations in 4U1915-05
L. Boirin, D. Barret, J. F. Olive +2
The X-ray burster and dipper 4U1915-05 (also known as XB1916-053) was observed 19 times for a total exposure of roughly 140 ks between 1996 February and October with the proportion…
A Self-Consistent Test of Comptonisation Models Using Bepposax Observations of Seyfert Galaxies
P. O. Petrucci, F. Haardt, L. Maraschi +6
We test accurate models of Comptonisation spectra over BeppoSAX observations of Seyfert galaxies focusing on the long look at NGC 5548. The hot plasma temperature derived with thes…
Extensive molecular gas in the tidal arms near NGC3077 - Birth of a dwarf galaxy?
Andreas Heithausen, Fabian Walter
Using the IRAM 30m radio telescope we have mapped the tidal arm feature south-east of NGC3077 where we recently detected molecular gas in the CO (J=1-0) and (2-1) transitions. We f…
The Disturbed ISM of the Local Group Dwarf Galaxy NGC 6822
W. J. G. de Blok, F. Walter
We present a wide-field, high spatial and velocity resolution map of the entire extended HI distribution of the nearby Local Group dwarf galaxy NGC 6822. The observations were obta…
A New Narrow-Line Seyfert 1 galaxy : RXJ1236.9+2656
G. C. Dewangan, K. P. Singh, Paula Szkody +1
We report identification of a narrow-line Seyfert 1 galaxy RXJ1236.9+2656. X-ray emission from the NLS1 galaxy undergoes long-term variability with 0.1--2.0 keV flux changing by a…
X-rays and regions of star formation: a combined ROSAT-HRI/near-to-mid IR study of the rho Oph dark cloud
Nicolas Grosso, Thierry Montmerle, Sylvain Bontemps +2
We have obtained two deep exposures of the rho Oph cloud core region with the ROSAT HRI. The improved position accuracy (1"-6") with respect to previous recent X-ray observations (…
The detection of spiral arm modulation in the stellar disk of an optically flocculent and an optically grand design galaxy
Ivanio Puerari, David L. Block, Bruce G. Elmegreen +2
Two dimensional Fourier spectra of near-infrared images of galaxies provide a powerful diagnostic tool for the detection of spiral arm modulation in stellar disks. Spiral arm modul…
Studies of the high luminosity quasar, PDS 456
J. Reeves, P. O'Brien, S. Vaughan +5
X-ray and multi-wavelength observations of the most luminous known local (z<0.3) AGN, the recently discovered radio-quiet quasar PDS 456, are presented. The spectral energy distrib…
Unravelling Active Galactic Nuclei
A. Y. K. N. Oshlack, R. L. Webster, M. J. Drinkwater +3
A complete flat-spectrum radio-loud sample of AGN includes a significant fraction of Seyfert-like AGN including a NLS1. Analysis of their optical spectra suggests that the reddest…
Search for radio recombination lines towards the gravitational lens PKS 1830-211
Niruj R. Mohan, K. R. Anantharamaiah, W. M. Goss
A search for radio recombination lines near 20 cm at z=0.193 and z=0.886 towards the gravitational lens system PKS 1830-211 has yielded upper limits on the line optical depth of 5…
Radio recombination lines from starburst galaxies : high and low density ionized gas
Niruj R. Mohan, K. R. Anantharamaiah, W. M. Goss
Radio recombination lines (RRL) at 8 GHz and 15 GHz detected from four starburst galaxies are shown to arise in compact high density HII regions, which are undetectable below ~4 GH…