Search Publications
A simultaneous maximum likelihood approach for galaxy-galaxy lensing and cluster lens reconstruction
Schneider, Peter; Geiger, Bernhard
In a previous paper we investigated means for constraining the mass distribution of cluster galaxies by weak lensing. We concluded that a comprehensive method should treat the lensing effects of individual cluster galaxies and those resulting from a general cluster component simultaneously. To this end we now develop a non-parametric maximum likel…
Direct calibration of the Cepheid period-luminosity relation
Paturel, G.; Garnier, R.; Lanoix, P.
After the first release of Hipparcos data, Feast & Catchpole gave a new value for the zero-point of the visual Cepheid period-luminosity relation, based on trigonometric parallaxes. Because of the large uncertainties on these parallaxes, the way in which individual measurements are weighted is of crucial importance. We therefore conclude that …
The extended emission-line region of the Seyfert galaxy Mrk 573
Falcke, H.; Durret, F.; Wilson, A. S. +3 more
We present the results of observations of the extended emission-line region of the Seyfert 2 galaxy Mrk 573, obtained using the WFPC2 on board HST and the TIGER integral field spectrograph on the CFHT. We describe and use a new `guided' deconvolution technique in which the spatial resolution of the TIGER data cubes is improved, allowing us to obta…
Evidence for the stratification of Fe in the photosphere of G191-B2B
Barstow, M. A.; Holberg, J. B.; Hubeny, I.
The presence of heavy elements in the atmospheres of the hottest H-rich DA white dwarfs has been the subject of considerable interest. While theoretical calculations can demonstrate that radiative forces, counteracting the effects of gravitational settling, can explain the detections of individual species, the predicted abundances do not accord we…
Emission lines of [O II] in the optical and ultraviolet spectra of planetary nebulae
Feibelman, W. A.; Keenan, F. P.; Hyung, S. +5 more
Recent R-matrix calculations of electron impact excitation rates in O II are used to calculate the emission-line ratio-ratio diagrams (R_1, R_2), (R_1, R_3) and (R_1, R_4), where R_1 = I(3729 A)/I(3726 A), R_2 = I(7320 A)/I(3726 + 3729 A), R_3 = I(7330 A)/I(3726 + 3729 A) and R_4 = I(2470 A)/I(3726 + 3729 A), for a range of electron temperatures (…
A new radio double lens from CLASS: B1127+385
Pearson, T. J.; Blandford, R. D.; Koopmans, L. V. E. +9 more
We present the discovery of a new gravitational lens system with two compact radio images separated by 0.701 +/- 0.001 arcsec. The lens system was discovered in the Cosmic Lens All Sky Survey (CLASS) as a flat-spectrum radio source. Both radio components show structure in a Very Long Baseline Array (VLBA) 8.4-GHz radio image. No further extended s…
The Cepheid distance to M96 and the Hubble constant
Ferguson, H. C.; Tanvir, N. R.; Shanks, T.
HST WFPC2 observations of Cepheids in M96 (NGC 3368) are used to find a distance to that galaxy of 11.2+/-1.0Mpc. This estimate is based on a calibration of the Cepheid period-luminosity relation in the Large Magellanic Cloud, and includes a correction for the difference in metallicity between the two systems. There are good reasons for believing …
[CII] emission and star formation in late-type galaxies
Tuffs, R. J.; Pierini, D.; Leech, K. J. +1 more
We demonstrate the existence of a reasonably tight linear correlation between the ratio of the [CII (^2P_3/2-^2 P_1/2)] (lambda 158 mu m) fine-structure cooling line intensity to the [^12CO (J=1 -> 0)] (lambda 2.6 mm) line emission, I_CII/I_CO, and the H alpha (lambda 6563 A ) equivalent width (EW), over the range 2-71 A in H alpha EW, for a sa…
M4-18: the planetary nebula and its WC10 central star
De Marco, Orsola; Crowther, Paul A.
We present a detailed analysis of the planetary nebula M4-18 (G146.7+07.6) and its WC10-type Wolf-Rayet (WR) central star, based on high-quality optical spectroscopy (WHT/UES, INT/IDS, WIYN/DensPak) and imaging (HST/WFPC2). From a non-LTE model atmosphere analysis of the stellar spectrum, we derive T_eff=31kK, log(Msolar/M_solaryr^-1)=-6.05, v_∞=1…
Quasar host galaxy images from the Hubble Space Telescope Archive
Disney, M. J.; Boyce, P. J.; Bleaken, D. G.
We systematically searched the non-proprietary data in the Hubble Space Telescope (HST) Archive to identify low-redshift quasars that have been imaged with the Wide Field Planetary Camera-2 (WFPC-2) but that have not yet been presented in the literature. We identified five such objects. Since these represent a significant increment to the number o…