| 1. |
- van Groningen, Ernst, et al.
(författare)
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A search for electron-scattered wings in Halpha in Seyfert-1 galaxies
- 1989
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 211:2, s. 318-323323
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Tidskriftsartikel (refereegranskat)abstract
- Spectra were obtained of a dozen bright Seyfert-1 galaxies to search for the presence of ultra-broad wings in Halpha, caused by electron scattering in the hypothetical hot intercloud medium. The spectra, which covered the wavelength range from 5300 Aring to 8750 Aring, were carefully calibrated to obtain the accurate continuum shape. In no case were ultra-broad wings of the type expected from electron scattering found, although significantly broader wings are detected than in previous data. Synthesized spectra were used to estimate the sensitivity of the survey for electron scattered wings. The results can be converted into a lower limit on the temperature of 7times10 7 K, and an upper limit of 0.15 on the electron scattering optical depth
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| 2. |
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| 3. |
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| 4. |
- Ronnback, Jari, et al.
(författare)
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Host galaxies of intermediate redshift radio-loud and radio-quiet quasars
- 1996
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Ingår i: MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. - : BLACKWELL SCIENCE LTD. - 0035-8711. ; 283:1, s. 282-296
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Tidskriftsartikel (refereegranskat)abstract
- In a search for host galaxies associated with quasars, we present results from deep CCD imaging using the European Southern Observatory (ESO) 3.5-m New Technology Telescope (NTT). 21 targets, 12 radio-loud and nine radio-quiet quasars, were observed in R,
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| 5. |
- van Groningen, Ernst
(författare)
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Further evidence for Raman scattering in RR Tel
- 1993
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Ingår i: Monthly notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 264:4, s. 975-979979
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Tidskriftsartikel (refereegranskat)abstract
- Raman scattering of O VIlambdalambda13O2, 1308 photons on the ground level of neutral hydrogen has been suggested as the cause of the broad emission features at 6825 and 7088 Aring in the spectra of symbiotic stars. The authors report on the detection of other Raman lines in the optical spectrum of the symbiotic star RR Tel. The lines detected are two He II Balmer lines that are Raman-scattered to wavelengths close to hydrogen Hbeta and Hgamma. Another possible detection is scattered C III lambda977, which appears at about 4977 Aring in the optical spectrum
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| 6. |
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| 7. |
- Örndahl, E., et al.
(författare)
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An optical imaging study of 0.4 <= z <= 0.8 quasar host galaxies. I. Observations and reduction
- 2003
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Ingår i: Astronomy and Astrophysics. - 0004-6361 .- 1432-0746. ; 404, s. 883-899
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Tidskriftsartikel (refereegranskat)abstract
- We have conducted an optical imaging study aimed at resolving the host galaxies of 79 radio-loud and radio-quiet quasars at z=0.4-0.8, extending the number of investigated objects in this redshift range by ~ 45%. Observations were performed mainly in the R band but also in V and I band using the Nordic Optical Telescope on La Palma. In this paper we discuss the sample composition and observations and the reduction techniques used. The quasars were selected in pairs of radio-loud and radio-quiet objects matched in the z-V plane in order to facilitate a statistical comparison. The radio-loud part of the sample contains comparable numbers of flat and steep radio spectrum sources which also are matched in redshift and V magnitude. Point spread function subtraction was performed using one-dimensional luminosity profiles both on the quasar image and on a field star, and subtracted images and luminosity profiles are shown for each quasar field. The detection rate is 60% for the radio-quiet host galaxies and 80% for radio-loud hosts. The host galaxies have magnitudes which make them brighter than an L* galaxy by a factor of 1.5-4 at the low end of the redshift range, which increases by 2-3 times towards the higher end of the redshift range. Both radio-quiet and radio-loud hosts follow the radio galaxy R-z Hubble relation well. Analysis and discussion of colours and morphology is presented in \citet{orn}. Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.
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