Search Publications
On stars with weak winds: the Galactic case
Schaerer, D.; Martins, F.; Hillier, D. J. +3 more
We study the stellar and wind properties of a sample of Galactic O dwarfs to track the conditions under which weak winds (i.e. mass loss rates lower than 10-8 M⊙ yr-1) appear. The sample is composed of low and high luminosity dwarfs including Vz stars and stars known to display qualitatively weak winds. Atmosphere …
Mass-to-Light Ratios of Field Early-Type Galaxies at z ~ 1 from Ultradeep Spectroscopy: Evidence for Mass-dependent Evolution
Rosati, P.; Rix, H. -W.; van der Wel, A. +3 more
We present an analysis of the fundamental plane for a sample of 27 field early-type galaxies in the redshift range 0.6<z<1.15 in the Chandra Deep Field-South and the field of the background cluster RDCS 1252.9-2927. Sixteen of the galaxies are at z>0.95. The galaxies in this sample have high signal-to-noise ratio spectra obtained at the V…
The Assembly of Diversity in the Morphologies and Stellar Populations of High-Redshift Galaxies
Papovich, Casey; Dickinson, Mark; Ferguson, Henry C. +2 more
We have used deep images from the Hubble Space Telescope to study the evolution in the morphologies, sizes, stellar masses, colors, and internal color dispersion of galaxies in the Hubble Deep Field-North. We selected two galaxy samples at 0.7<=z<=1.4 and 1.9<=z<=3.0 from a near-infrared, flux-limited catalog with complete photometric …
A statistical study of the properties of interplanetary coronal mass ejections from 0.3 to 5.4 AU
Liu, Y.; Richardson, J. D.; Belcher, J. W.
We make a comprehensive survey of interplanetary coronal mass ejections (ICMEs) observed by the Helios 1 and 2, Ulysses, WIND and ACE spacecraft, which together cover heliocentric distances from 0.3 to 5.4 AU. The signatures used to identify ICMEs are enhanced helium abundances and depressed proton temperatures. We use the ICME list to study the r…
Properties and geoeffectiveness of magnetic clouds in the rising, maximum and early declining phases of solar cycle 23
Schwenn, R.; Bothmer, V.; Koskinen, H. E. J. +1 more
The magnetic structure and geomagnetic response of 73 magnetic clouds (MC) observed by the WIND and ACE satellites in solar cycle 23 are examined. The results have been compared with the surveys from the previous solar cycles. The preselected candidate MC events were investigated using the minimum variance analysis to determine if they have a flux…
High-Ionization Emission in Metal-deficient Blue Compact Dwarf Galaxies
Thuan, Trinh X.; Izotov, Yuri I.
Primordial stars are expected to be very massive and hot, producing copious amounts of hard ionizing radiation. The best place to study hard ionizing radiation in the local universe is in very metal-deficient blue compact dwarf (BCD) galaxies. We have carried out a MMT spectroscopic search for [Ne V] λ3426 (ionization potential of 7.1 ryd), [Fe V]…
Galaxy Morphologies in the Hubble Ultra Deep Field: Dominance of Linear Structures at the Detection Limit
Elmegreen, Bruce G.; Elmegreen, Debra Meloy; Rubin, Douglas S. +1 more
Galaxies in the Hubble Ultra Deep Field (UDF) larger than 10 pixels (0.3") have been classified according to morphology, and their photometric properties are presented. There are 269 spiral, 100 elliptical, 114 chain, 126 double-clump, 97 tadpole, and 178 clump-cluster galaxies. We also cataloged 30 B-band and 13 V-band dropouts and calculated the…
How to Channel Photospheric Oscillations into the Corona
Erdélyi, R.; De Pontieu, B.; De Moortel, I.
There are now many observations of waves in the solar corona with periods around 5 minutes. The source of these waves is uncertain, although global p-modes in the photosphere are an obvious candidate, given the similarity of the dominant periods. However, p-modes are traditionally considered evanescent in the upper photosphere, and it has been unc…
The primordial binary population. I. A near-infrared adaptive optics search for close visual companions to A star members of Scorpius OB2
Kaper, L.; Brown, A. G. A.; Zinnecker, H. +2 more
We present the results of a near-infrared adaptive optics survey with the aim to detect close companions to Hipparcos members in the three subgroups of the nearby OB association Sco OB2: Upper Scorpius (US), Upper Centaurus Lupus (UCL) and Lower Centaurus Crux (LCC). We have targeted 199 A-type and late B-type stars in the KS band, and …
Electric current and magnetic field geometry in flapping magnetotail current sheets
Sauvaud, J. -A.; Balogh, A.; Zhang, T. L. +11 more
Using four-point magnetic field measurements by the Cluster spacecraft, we statistically analyze the magnetic field and electric current configurations during rapid crossings of the current sheet observed in July-October 2001 at geocentric distances of 19 RE. The database includes 78 crossings, specially selected to apply multi-point da…