Search Publications
The HST view of FR I radio galaxies: evidence for non-thermal nuclear sources
Capetti, A.; Chiaberge, M.; Celotti, A.
Unresolved nuclear sources are detected by the Hubble Space Telescope in the great majority of a complete sample of 33 FR I radio galaxies belonging to the 3CR catalogue. The optical flux of these Central Compact Cores (CCC) shows a striking linear correlation with the radio core one over four decades, arguing for a non-thermal synchrotron origin …
HST/NICMOS2 observations of the HD 141569 A circumstellar disk
Ménard, F.; Mouillet, D.; Augereau, J. C. +1 more
We report the first resolved scattered light images of the circumstellar dust disk around the old Pre-Main Sequence star da. The disk seen in HST/NICMOS2 images shapes a bright annulus inclined at 37.5degr +/- 4.5degr from edge-on. This ring peaks at 325+/-10 AU from the star with a characteristic width of ~ 150 AU. At 1.6 mu m, the dust grains sc…
HST luminosity functions of the globular clusters M10, M22, and M55. A comparison with other clusters
Zoccali, M.; Piotto, G.
From a combination of deep Hubble Space Telescope V and I images with groundbased images in the same bands, we have obtained color-magnitude diagrams of M10, M22, and M55, extending from just above the hydrogen burning limit to the tip of the red giant branch, down to the white dwarf cooling sequence. We have used the color-magnitude arrays to ext…
The ionizing cluster of 30 Doradus. III. Star-formation history and initial mass function
Terlevich, R.; Bosch, G.; Selman, F. +1 more
A new method is presented and used to determine the IMF of the starburst cluster NGC2070. A new correction, the magnitude-limit correction is introduced, and shown to be crucial when attempting to derive the IMF in the presence of variable reddening when the photometry is not several magnitudes deeper than the fainter stars analyzed. Failure to ap…
HST images and properties of the most distant radio galaxies
Pentericci, L.; Macchetto, F.; Spinrad, H. +4 more
With the Hubble Space Telescope we have obtained images of 9 of the most distant radio galaxies. The galaxies, which have redshifts between z=2.3 and z=3.6, were observed with the WFPC2 camera in a broad band filter (F606W or F707W, roughly equivalent to V or R-band), corresponding to the near ultraviolet emission in the rest frame of the radio ga…
Multiplicity of the HH 111 jet source: it Hubble Space Telescope NICMOS images and VLA maps
Bally, John; Rodríguez, Luis F.; Reipurth, Bo +2 more
We have observed the region around the HH 111 jet source with NICMOS onboard the Hubble Space Telescope, using two filters, F160W and F205W, which besides stellar continuum transmit the [FeII] 1.64 mu m and H_2 2.12 mu m emission lines, respectively. The jet can now be traced to within 2\farcs4 of the VLA source. In the F205W filter we detect for …
What heats the bright H II regions in I ZW 18?
Schaerer, D.; Stasińska, G.
We have used the radiation field from a starburst population synthesis model appropriate for the brightest H ii region of I Zw 18 to perform a photoionization model analysis of this object. We have investigated whether, with the observed nebular density distribution as revealed by the HST images and a total stellar radiation compatible with the ob…
High-resolution abundance analysis of two individual stars of the bulge globular cluster NGC 6553
Bica, E.; Barbuy, B.; Ortolani, S. +2 more
A detailed abundance analysis of 2 giants of the metal-rich bulge globular cluster NGC 6553 was carried out using high resolution échelle spectra obtained at the ESO 3.6m telescope. The temperature calibration of metal-rich cool giants needs high quality photometric data. We have obtained JK photometry at ESO and VI photometry with the Hubble Spac…
Probing early-type galaxy evolution with the Kormendy relation
Greggio, L.; Saglia, R. P.; Bender, R. +3 more
We investigate the evolution of early-type galaxies in four clusters at z=0.4 (Abell 370, Cl 0303+17, Cl 0939+47 and Cl 1447+26) and in one at z=0.55 (Cl 0016+16). The galaxies are selected according to their spectrophotometrically determined spectral types and comprise the morphological classes E, S0 and Sa galaxies. Structural parameters are det…
Ultraviolet observations of Sirius A and Sirius B with HST-GHRS. an interstellar cloud with a possible low deuterium abundance
Koester, D.; Ferlet, R.; Vidal-Madjar, A. +4 more
We present new observations of the binary Sirius A / Sirius B performed with HST-GHRS. Two interstellar clouds are detected on this sightline, one of them being identified as the Local Interstellar Cloud (LIC), in agreement with previous HST-GHRS observations of Sirius A (Lallement et al. \cite{lalle}). The interstellar structure of this sightline…