Search Publications

Distribution of extinction and star formation in NGC 1569

Battaner, E.; Relaño, M.; Lisenfeld, U. +1 more

We investigate the spatial distribution of the intrinsic extinction in the starburst dwarf galaxy NGC 1569 using an extinction map of the whole galaxy derived from the mbox H α/ mbox H β emission line ratio. We differentiate the extinction in the H ii regions from the extinction of the diffuse gas. The intrinsic extinction shows considerable varia…

WLM-1: An old, Nonrotating, Gravitationally Unperturbed, Highly Elliptical Extragalactic Globular Cluster

Stephens, Andrew W.; Catelan, Márcio; Contreras, Roxana P.

Globular clusters have long been known for presenting (at times) significant deviations from spherical symmetry. While rotation has been the main proposed explanation, other complicating factors such as their constant interaction with the strong gravitational potential of their host galaxy have made it difficult for a consensus to be reached. To a…

Subsurface characteristics of sunspots

Kosovichev, Alexander G.

Time distance helioseismology provides 3-D subphotospheric maps of sunspots, emerging magnetic structures and associated convective flows. This gives us new insights into the basic physical processes inside the Sun, formation of magnetic structures in the solar plasma and mechanisms of solar activity. Recent results from the MDI instrument on SOHO…

Plasma Waves Near Reconnection Sites

André, M.; Vaivads, A.; Treumann, R. A. +1 more

High-Ionization Forbidden Lines in the UV Spectrum of AG Draconis

Young, P. R.; Dupree, A. K.; Espey, B. R. +1 more

High-ionization forbidden lines from Ca VII, Fe VII, Mg V, Mg VI, Mg VII, and Si VII are found in recent Hubble Space Telescope STIS ultraviolet spectra of the symbiotic star AG Draconis. These species have ionization potentials between 99 and 205 eV, which are unexpected due to the high density (~10¹⁰ cm^-3) of the AG Dra neb…

Large Silicon Abundance in Photodissociation Regions

Nakagawa, Takao; Onaka, Takashi; Tomono, Daigo +3 more

We have made one-dimensional raster scan observations of the ρ Oph and σ Sco star-forming regions with two spectrometers (SWS and LWS) on board the ISO. In the ρ Oph region, [Si II] 35 µm, [O I] 63 µm, 146 µm, [C II] 158 µm, and the H₂ pure rotational transition lines S(0) to S(3) are detected, and the photodisso…

Radio and X-ray observations of an exceptional radio flare in the extreme z = 4.72 blazar GBB1428+4217

Fabian, A. C.; Worsley, M. A.; Pooley, G. G. +1 more

We report on the extreme behaviour of the high-redshift blazar GBB1428+4217 at z = 4.72. A continued programme of radio measurements has revealed an exceptional flare in the light curve, with the 15.2-GHz flux density rising by a factor of ~3 from ~140 to ~430 mJy in a rest-frame time-scale of only ~4 months - much larger than any previous flares …

Astrochemistry: Complex organic matter in Titan's aerosols?

Biemann, K.

Spectral shape of the UV ionizing background and O VI absorbers at z ∼ 1.5 towards HS 0747+4259

Reimers, D.; Hagen, H. -J.; Lopez, S. +5 more

Aims.We report on high resolution spectra of the bright QSO HS 0747+4259 (z_em = 1.90, V = 15.8) observed to search for intermediate redshift O VI absorption systems.Methods.The spectra were obtained by means of the Space Telescope Imaging Spectrograph (STIS) at the Hubble Space Telescope (HST) and the High Resolution Echelle Sp…

The Recent Star Formation in NGC 6822 from Hubble Space Telescope Imaging

Bianchi, Luciana; Efremova, Boryana V.

We present Hubble Space Telescope WFPC2 and STIS imaging of the low-metallicity galaxy NGC 6822, performed as part of a study of the young stellar populations in the galaxies of the Local Group. Eleven WFPC2 pointings, with some overlap, cover two regions extending over 19 and 13 arcmin², respectively, off the galaxy center. The filters…