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Energy-dependent variability and the origin of the soft X-ray excess in active galactic nuclei
Done, Chris; Gierliński, Marek
The origin of the soft excess seen in many active galactic nuclei (AGN) below ~1 keV is still an unsolved problem. It is unlikely to represent a true continuum component as its characteristic `temperature' shows a remarkable constancy over a wide range of AGN luminosity and black hole mass. This instead favours an association with atomic processes…
Probing the evolution of the near-infrared luminosity function of galaxies to z~= 3 in the Hubble Deep Field-South
Chincarini, G.; Fontana, A.; Vanzella, E. +6 more
We present the rest-frame Js- and Ks-band luminosity function (LF) of a sample of about 300 galaxies selected in the Hubble Deep Field-South (HDF-S) at Ks<= 23 (Vega). We use calibrated photometric redshift together with spectroscopic redshift for 25 per cent of the sample. The accuracy reached in the photometri…
Quasar Spectrum Classification with Principal Component Analysis (PCA): Emission Lines in the Lyα Forest
Suzuki, Nao
We investigate the variety in quasar UV spectra (λλ1020-1600), with emphasis on the weak emission lines in the Lyα forest region, using principal component analysis (PCA). We use 50 smooth continuum-fitted quasar spectra (0.14<z<1.04) taken by the Hubble Space Telescope (HST) Faint Object Spectrograph. The first, second, and third principal …
X-ray observations of RX J0822-4300 and Puppis-A
Hui, C. Y.; Becker, W.
Based on observations with the X-ray observatories Chandra and XMM-Newton we present results from a detailed spectro-imaging and timing analysis of the central compact X-ray source RX J0822-4300 in the supernova remnant Puppis-A. The superior angular resolution of Chandra allows for the first time to pinpoint the point source nature of this object…
An improved deprojection and PSF-deconvolution technique for galaxy-cluster X-ray surface-brightness profiles
Arnaud, M.; Pointecouteau, E.; Pratt, G. W. +1 more
We have developed a regularisation procedure for the direct deprojection and PSF-deconvolution of X-ray surface brightness profiles of clusters of galaxies. This procedure allows us to obtain accurate density profiles in a straightforward manner from X-ray observations (in particular data from XMM-Newton, where the PSF correction is important), wh…
Vertical distribution of ozone on Mars as measured by SPICAM/Mars Express using stellar occultations
Montmessin, Franck; Bertaux, Jean-Loup; Perrier, Séverine +4 more
The ultraviolet spectrometer of the SPICAM instrument on board the European Mars Express mission has performed stellar occultations to probe the atmosphere. Vertical profiles of ozone are retrieved from inversion of transmission spectra in the altitude range 20-30 to 70 km. They are analyzed here as functions of latitude and season of the observat…
The evolution of Lyman α absorbers in the redshift range 0.5 < z < 1.9
Reimers, D.; Janknecht, E.; Lopez, S. +1 more
We investigate the evolution and the statistical properties of the Ly α absorbers of the intergalactic medium (IGM) in the largely unexplored redshift range z=0.5-1.9. We use high-resolution (R ≥ 30 000) UV (STIS) and optical (VLT/UVES and Keck/HIRES) spectra of nine bright quasars with z_em < 1.94. The Ly α lines detected in the lines of sight…
Evidence for a Supernova Associated with the X-Ray Flash 020903
Covino, S.; Becker, A. C.; Filippenko, A. V. +24 more
We present ground-based and Hubble Space Telescope optical observations of the X-ray flash (XRF) 020903, covering 300 days. The afterglow showed a very rapid rise in the first day, followed by a relatively slow decay in the next few days. There was a clear bump in the light curve after ~25 days, accompanied by a drastic change in the spectral ener…
Rings and Bent Chain Galaxies in the GEMS and GOODS Fields
Elmegreen, Bruce G.; Elmegreen, Debra Meloy
Twenty-four galaxies with rings or partial rings were studied in the GEMS and GOODS fields out to z~1.4. Most resemble local collisional ring galaxies in morphology, size, and clumpy star formation. Clump ages range from 108 to 109 yr, and clump masses go up to several × 108 Msolar, based on color evolut…
A Multi-Wavelength Study of the Compact M1 Flare on October 22, 2002
Mason, H. E.; Schmieder, B.; Berlicki, A. +1 more
In this paper we present a further study of the Ml class flare observed on October 22, 2002. We focus on the SOHO Coronal Diagnostic Spectrometer (CDS) spectral observations performed during a multi-wavelength campaign with TRACE and ground-based instruments (VTT, THEMIS). Strong blue-shifts are observed in the CDS coronal lines in flare kernels d…