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The past fifty years have been an epoch of impressive progress in the field of astronomical technology. Practically all the technical tools, which we use today, have been developed during that time span. While the first half of this period has been dominated by advances in the detector technologies, during the past two decades innovative telescope concepts have been developed for practically all wavelength ranges where astronomical observations are possible. Further important advances can be expected in the next few decades. Based on the experience of the past, some of the main sources of technological progress can be identified., Comment: 9 pages, 9 figures, Review article associated with the Karl Schwarzschild Award Lecture 2015, Published in Astron. Nachrichten; doi: 10.1002/asna.201612360

CONTEXT. Because of the presence of rotation and accretion disks, classical T Tauri stars have symmetry planes that are normally inclined relative to the plane of the sky. The inclination angles affect the observed spectral properties of these objects. AIMS. We study the influence of the inclination angles on classical T Tauri star spectra in an empirical manner. METHODS. Published inclination angles, derived from the stellar photospheric rotation or from spatially resolved circumstellar disk observations, are compared with various observed spectral properties, and correlations are established and investigated. RESULTS. Inclinations derived from the stellar rotation are found to be much less accurate than the published disk inclinations, and no significant correlations between spectral properties and inclinations based on rotation data could be detected. In contrast, significant correlations are found between the disk inclination angles and the apparent velocities observed for the forbidden emission lines and the wind absorption features of permitted lines. These data support the assumption of cone-like polar winds with opening angles smaller than $\approx 45^\circ$. Other spectral features show weaker or no inclination dependence. Using these results, the true (deprojected) flow velocities of the polar winds are derived for the investigated sample of T Tauri stars. Deprojected wind-ejection velocities appear to differ by a factor of two among the stars in our sample, which spans a range of mass-loss rates from $10^{-10} $M$_\odot$/yr to $3 \times 10^{-7} $M$_\odot$/yr., Comment: accepted by Astronomy and Astrophysics

Using the UVES echelle spectrograph at the ESO VLT we obtained two-dimensional high-resolution (R = 50 000) spectra of the edge-on disk objects HH30*, HK Tau B, and HV Tau C. For comparison purposes we also observed with the same equipment both the classical T Tauri star HL Tau and the active late-type star LDN 1551-9. The spectra of all three observed edge-on disks consist of a T Tauri emission and absorption line spectrum with superimposed jet emission lines. Analysis of the spectra confirmed that the disks are completely opaque at visible wavelengths and that light from the central objects reaches us only via scattering layers above and below the disk planes. The central objects of our targets were found to be normal T Tauri stars showing moderate but different amounts of veiling of their photospheric spectra, indicating different accretion rates or evolutionary stages. We suggest that all classical T Tauri stars (CTTSs) show this observed morphology when viewed edge-on. Part of the jet emission from edge-on systems is directly visible to us in the forbidden lines as well as in Halpha and He I, a finding which contradicts the present paradigm of a pure magnetospheric accretion origin for the formation of hydrogen and helium emission lines in moderately active CTTSs. From a comparison with those Taurus-Auriga CTTSs for which the inclination is reliably known, we conclude that the view angle of CTTS systems is one of the key parameters governing apparent Halpha emission strength in the T Tauri class. We discuss the various possible formation regions for the Na I D lines and show that profiles similar to observed ones can be formed at the base of the disk wind., Comment: 16 pages, 15 figures, accepted by A&A

Using the Uves echelle spectrograph at the ESO VLT, we observed the absorption line spectrum of the QSO 0103-260 in the Fors Deep Field. In addition to the expected Ly-alpha forest lines, we detected at least 16 metal absorption systems with highly different ionization levels in the observed spectral range. The redshifts of the metal absorption systems are strongly correlated with the redshift distribution of the high-z galaxies in the Fors Deep Field and with the strength (but not the number density) of the Ly-alpha forest lines. Both the metal systems and the galaxies show clustering at least up to the QSO emission line redshift of 3.365, but only few of these galaxy accumulations seem to form bound systems., Comment: 12 pages, 8 figures, accepted for publication in Astron. & Astrophys

Using the VLT we have obtained high quality spectra of about 70 high redshift (1- 4.6) galaxies within the FORS Deep Field (FDF). As expected most of them turn out to be (bright) starburst galaxies and the observed spectra agree with synthetic ones. The equivalent width of the CIV(1550) absorption line turns out to be a good indicator for the galaxies metallicity. Furthermore our high-z starburst galaxies show increasing metal content with decreasing redshift. Compared with local starburst galaxies they tend to be overliminous for their metallicity., Comment: 3 pages, including 4 eps-figures, Latex2e, to appear in proceedings of MPA/ESO/MPE/USM Joint Astronomy Conference on "Lighthouses of the Universe" (Eds.: R. Sunyaev, M. Gilfanov, E. Churazov)

We present the first intermediate-resolution (lambda / 3000) spectrum of the bright quasi-stellar object 3C273 at wavelengths between 900 and 1200 A. Observations were performed with the Berkeley spectrograph aboard the ORFEUS-SPAS II mission. We detect Lyman beta counterparts to previously-identified intergalactic Lyman-alpha features at cz = 19900, 1600, and 1000 km/s; counterparts to other putative Lyman-alpha clouds along the sight line are below our detection limit. The strengths of the two very low redshift Lyman-beta features, which are believed to arise in Virgo intracluster gas, exceed preflight expectations, suggesting that the previous determination of the cloud parameters may underestimate the true column densities. A curve-of-growth analysis sets a minimum H I column density of 4 E14/cm^2 for the 1600 km/s cloud. We find marginally significant evidence for Galactic H_2 along the sight line, with a total column density of about 1 E15/cm^2. We detect the stronger interstellar O VI doublet member unambiguously; the weaker member is blended with other features. If the Doppler b value for O VI is comparable to that determined for N V then the O VI column density is 7 +/- 2 E14/cm^2, significantly above the only previous estimate. The O VI / N V ratio is about 10, consistent with the low end of the range observed in the disk. Additional interstellar species detected for the first time toward 3C273 (at modest statistical significance) include P II, Fe III, Ar I, and S III., Comment: LaTeX file, 11 pages, 4 encapsulated PostScript figures. Uses aaspp4.sty and astrobib.sty. (Astrobib is available from http://www.stsci.edu/software/TeX.html .) The ORFEUS telescope is described at http://sag-www.ssl.berkeley.edu/orfeus/ . To appear in ApJ (Letters)