Search Publications
The cometary blue compact dwarf galaxies Mkn 59 and Mkn 71. A clue to dwarf galaxy evolution?
Thuan, T. X.; Izotov, Y. I.; Papaderos, P. +3 more
``Cometary'' Blue Compact Dwarf Galaxies (iI,C BCDs) are characterized by an off-center starburst close to the end of their elongated stellar bodies. This rare phenomenon may carry some clues on how collective star formation ignites and propagates in gas-rich low-mass stellar systems. This off-center burst may be a fortuitous enhancement of the ot…
The evolution of the color gradients of early-type cluster galaxies
Greggio, L.; Saglia, R. P.; Bender, R. +2 more
We investigate the origin of color gradients in cluster early-type galaxies to probe whether pure age or pure metallicity gradients can explain the observed data in local and distant (z ≈ 0.4) samples. We measure the surface brightness profiles of the 20 brightest early-type galaxies of CL0949+44 (hereafter CL0949) at redshift z=0.35-0.38 from HST…
The elusive active nucleus of NGC 4945
Maiolino, R.; Marconi, A.; Macchetto, F. +4 more
We present new HST NICMOS observations of NGC 4945, a starburst galaxy hosting a highly obscured active nucleus that is one of the brightest extragalactic sources at 100 keV. The HST data are complemented with ground based Fe II line and mid-IR observations. A 100pc-scale starburst ring is detected in Paα, while H2 traces the walls of a…
Characteristics of solar coronal streamers. Element abundance, temperature and density from coordinated CDS and UVCS SOHO observations
Bromage, G. E.; Parenti, S.; Raymond, J. C. +3 more
This paper presents the results from coordinated observations of streamers acquired by the SOHO Coronal Diagnostic Spectrometer (CDS) and UltraViolet Coronograph Spectrometer (UVCS) experiments. Data from different altitudes within the solar corona were taken, with the purpose of determining their physical parameters - densities, electron temperat…
Absorption spectra of Mg-rich Mg-Fe and Ca pyroxenes in the mid- and far-infrared regions
Koike, C.; Tsuchiyama, A.; Shibai, H. +6 more
Absorption spectra of the pyroxene group have been measured in mid and far infrared wavelengths. The samples are crystalline pyroxenes (enstatite, diopside, and natural pyroxene) and amorphous pyroxenes (enstatite and diopside glass). Especially, the synthetic pyroxenes such as orthoenstatite, clinoenstatite and diopside are pure and high-quality …
New PAH mode at 16.4 mu m
Schmidt, W.; Léger, A.; Moutou, C. +2 more
The detection of a new 16.4 mu m emission feature in the ISO-SWS spectra of NGC 7023, M17, and the Orion Bar is reported. Previous laboratory experiments measured a mode near this wavelength in spectra of PAHs (Polycyclic Aromatic Hydrocarbons), and so we suggest the new interstellar 16.4 mu m feature could be assigned to low-frequency vibrations …
The first VLT FORS1 spectra of Lyman-break candidates in the HDF-S and AXAF Deep Field
Aragón-Salamanca, A.; Cristiani, S.; Arnouts, S. +9 more
We report on low-resolution multi-object spectroscopy of 30 faint targets (R =~ 24-25) in the HDF-S and AXAF deep field obtained with the VLT Focal Reducer/low dispersion Spectrograph (FORS1). Eight high-redshift galaxies with 2.75< z < 4 have been identified. The spectroscopic redshifts are in good agreement with the photometric ones with a…
Multi-component structure of solar and stellar transition regions
Peter, H.
Emission lines from the solar transition region between the chromosphere and the corona often show a two Gaussian component profile with a core and a broad second component contributing up to 25% to the total intensity. For the first time a systematic study of the broadening and Doppler shift of the second weaker components is performed using SUME…
ISO spectroscopy of circumstellar dust in the Herbig Ae systems AB Aur and HD 163296
Waters, L. B. F. M.; van Dishoeck, E. F.; van den Ancker, M. E. +3 more
Using both the Short- and Long-wavelength Spectrometers on board the Infrared Space Observatory (ISO), we have obtained infrared spectra of the Herbig Ae systems AB Aur and HD 163296. In addition, we obtained ground-based N band images of HD 163296. Our results can be summarized as follows: (1) The main dust components in AB Aur are amorphous sili…
The γ Velorum binary system. II. WR stellar parameters and the photon loss mechanism
Schmutz, W.; Hillier, D. J.; Crowther, P. A. +4 more
In this paper we derive stellar parameters for the Wolf-Rayet star in the gamma Velorum binary system (WR11), from a detailed non-LTE model of its optical and infrared spectra. Compared to the study of Schaerer et al., the parameters of the WC8 star are revised to a hotter effective temperature (T_eff ~ 57 kK), a higher luminosity (log (L/Lsu…