Search Publications
Temporal variability of Mrk 421 from XMM-Newton observations
Haberl, F.; Papadakis, I.; Brinkmann, W. +1 more
Mrk 421 has been observed several times as a calibration target for the instruments on board XMM-Newton. We have studied in some detail the temporal and spectral variability of the source during eight pointings, mainly from the PN camera, which provides the by far highest S/N data available for that source.
X-ray emission diagnostics from the M87 jet
Wilson, A. S.; Perlman, E. S.
We use Chandra, HST and VLA observations of M87 to investigate the physics of X-ray emission from AGN jets. We find that X-ray hotspots in the M87 jet occur primarily in regions with hard optical-to-X-ray spectra and lower than average polarization. Particle injection appears to be required both continuously in the jet sheath as well as locally at…
Two new optical jets in B2 radio galaxies
Bondi, M.; Capetti, A.; Morganti, R. +5 more
We present HST observations of previously undetected optical jets in the low-luminosity radio galaxies B2 0755+37 and B2 1553+24. We show that there is accurate spatial coincidence between optical and radio emission, implying that the former is likely to be synchrotron radiation. The physical properties of the jets are similar to those known previ…
Optical and infrared observations of radioactive elements in supernovae
Sollerman, Jesper
At late phases the powering of supernova light curves is often provided by the decay of radioactive elements synthesized in the explosions. This is unambiguously revealed when the light curve decline follows the half-life time of the decaying elements, and the bolometric luminosity then directly provides the mass of ejected radioactive material. I…
HST NICMOS imaging of z∼2-3 radio-quiet quasars
Calzetti, D.; Lehnert, M.; Ridgway, S. +1 more
We will present the results of a NICMOS H-band imaging survey of a small sample of z∼2-3 radio-quiet quasars. We have resolved extension in at least four of five objects and find evidence for a wide range in the morphologies and magnitudes of these hosts. The host galaxy luminosities range from sub- L ∗ to about 4 L ∗, with m…
Spectral energy distributions of five FR I radio galaxies
Capetti, A.; Chiaberge, M.; Celotti, A. +2 more
We discuss the multi-wavelength properties of the radio galaxies 3C 31, 3C 264, 3C 270, 3C 465 and NGC 7052. The data have been deduced from observations with the VLBI/VLA arrays, HST and ROSAT. The SED of these sources, when compared with that of BL Lacs shows that beaming effects are important, but are not enough—in the simplest scenario—to expl…
Irradiation phenomena in young solar-type stars and the early solar system: X-ray observations and γ-ray constraints
Montmerle, Thierry
The high levels of X-ray flaring activity observed in young stars and protostars suggest correspondingly high levels of low-energy particle irradiation of their circumstellar disks, and hence of early solar system material like meteorites. We first briefly review the latest X-ray observational results obtained by Chandra and XMM-Newton on two 'typ…
Hubble space telescope observations of BL Lacertae environments
Urry, C. Megan; O'Dowd, Matthew; Scarpa, Riccardo +3 more
We analyze images of BL Lacertae objects obtained with the Hubble Space Telescope WFPC2 and the F814W filter. The nine objects cover a redshift range of 0.19 to 0.997. The relatively deep images are sufficient to detect galaxies at least one magnitude below MI* (-21.4) and in most cases to three magnitudes below M*. Galaxy enhancement o…
HST imaging of radio galaxies at /z=0.2: a comparison with quasar hosts and normal ellipticals
McLure, R. J.; Dunlop, J. S.; Hughes, D. H. +3 more
We summarise the results of our recently completed HST R-band study of low-redshift (0.1< z<0.25) FRII radio galaxies along with the host galaxies of quasars of similar redshifts. We find that, like radio galaxies, the hosts of radio-loud quasars and all but the least luminous radio-quiet quasars are massive elliptical galaxies with relative…
The nuclear dust disks of five nearby 3CR elliptical galaxies
Sparks, W. B.; Baum, S. A.; Biretta, J. A. +3 more
We present broad- and narrow-band WFPC2 images of the nuclear dust disks and rings of five low- z elliptical galaxies hosting 3C radio sources: NGC 383 (3C 31)/NGC 382, NGC 3862 (3C 264), NGC 4261 (3C 270), UGC 12064 (3C 449), and NGC 7720 (3C 465)/NGC 7720A. We detect resolved line emission in all the disks. In NGC 383, the line emission consists…