The Chandra gratings exceed a resolving power R = 1000, but only at the longest wavelengths and with relatively low effective areas. Recent X-ray observations of cool stars illustrate the problem of line blending at different resolutions and give a good sense of what we will routinely be able to measure with Constellation-X, provided it has high enough spectral resolution. We also expect new diagnostics from weak lines and line profiles. Support for this work is provided by NASA NAS8-39083 to SAO for the CXC and LTSA NAG5-3559.

The diffraction grating spectra from Chandra and XMM-Newton have given the astronomical community a huge step forward in x-ray spectroscopy of celestial sources. They have proven the scientific richness of the field. But the spectra have resolution of only 300 to 1000 – low by the standards of the visible and the ultraviolet. We discuss some of the exciting new science that can be addressed if spectral resolution of up to 10,000 (or more) can be achieved in the x-ray. We then show how practical, high efficiency, high resolution x-ray spectrographs can be built for high throughput missions like Constellation-X and XEUS.

The Far Ultraviolet Spectroscopic Explorer (FUSE) instrument covers the spectral range 912-1187 Å with a resolving power of 15,000 to 20,000. This spectral region provides unique access for the study of many atomic and ionic species found in the interstellar medium, intergalactic medium, stars, and extragalactic objects. This paper summarizes the status of the mission and then discusses the need for higher resolution spectroscopy. Although the FUSE instrumental resolution is sufficient to separate most species, it usually it is not adequate for analyzing the gas velocity structure in detail. Implications for future missions are discussed.

APEX is a proposed Small Explorer satellite that will obtain high-resolution EUV spectra of white dwarfs, CVs, stellar coronae, and the local ISM. The APEX effective area (30-50 cm2) and resolution (~10,000) are an order of magnitude improvement over Chandra.

We have used the high spatial and high spectral resolution of the Space Telescope Imaging Spectrograph (STIS) to study Eta Carinae and the Homunculus. Since the last minimum in 1998.0, CCD spectral modes have followed changes in the Eta Carinae, and large-scale changes in the Homunculus. Since 2001.7, MAMA echelle-mode observations have followed changes in the Eta Carinae and the very nearby ejecta through the 2003.5 minimum. Very significant changes in the star and nebular occur as the X-Ray drop occurs in the minimum.

In the post-HST era, advanced missions for performing UV spectroscopy must excel in many ways. We must not overlook the importance of high wavelength resolution for investigating absorption lines from gas systems in the Galaxy and beyond. We consider here some basic principles on this topic, both scientific and technical.

Doppler imaging has been used to image dark spots on the surfaces of rapidly rotating, magnetically active stars for the last 20 years. More recently, methods have been developed for combining line-profile information from large numbers of spectral lines simultaneously. This has allowed starspot distributions to be mapped in sufficient detail to allow tracking of individual spots over several stellar rotations, delineating surface differential rotation patterns for a number of stars. Zeeman-Doppler imaging allows the creation of stellar magnetograms, which are providing the first insights into the 3D topology of stellar coronal magnetic fields. The advent of cryogenic infrared echelle spectrographs opens up exciting new possibilities for Doppler imaging in molecular lines of species such as TiO, OH, and FeH.

We briefly note several current topics concerning the properties of interstellar clouds for which high-resolution optical spectra play a significant role: (1) the recognition and characterization of small-scale (sub-pc) structure in both atomic and molecular gas; (2) the discovery of variations in the 7Li/6Li isotopic ratio in the nearby Galactic ISM; (3) the determination of atomic and molecular abundances and physical conditions for heavily reddened (“translucent”) Galactic sightlines; and (4) studies of interstellar clouds in the LMC and SMC.

The first detection and identification of deuterium Balmer lines were recently reported in H ii regions, using high spectral resolution data secured at CFHT and VLT. The Di lines appear as faint, narrow emission features in the blue wings of the H i Balmer lines and can be distinguished from high-velocity Hi emission. The identification as deuterium and the excitation mechanism as fluorescence are both established beyond doubt. The deuterium Balmer series might lead to a new, optical method of deuterium abundance measurement in the interstellar medium. This may be the only way to observe atomic deuterium in objects like the Magellanic Clouds or low metallicity blue compact galaxies.

Using high-resolution optical spectra, we determine effective temperatures and gravities for a sample of very low-mass stellar and substellar PMS cluster objects. Masses and radii are then derived using known cluster distance and photometry; two of our targets seem to have planetary masses. Our results are independent of theoretical evolutionary tracks. While our results agree with the track predictions for hotter, higher mass objects, discrepancies appear for the coolest, lowest mass ones. This may be due to track uncertainties related to formation effects, and/or internal conditions, in these very young, ultra-low-mass objects.

Plans for future high-resolution infrared spectrometers on large groundbased telescopes, their capabilities and science goals are briefly reviewed.

NASA and the DLR are developing SOFIA, the Stratospheric Observatory for Infrared Astronomy: a 2.5 m telescope in a Boeing 747SP aircraft. By flying in the lower stratosphere, SOFIA will allow astronomical measurements covering the wavelength range from 0.3 μm to 1.6 mm, with an emphasis on the spectral regions inaccessible from the ground, particularly the 6-8 μm and 30-300 μm regions. SOFIA will see “first light” in 2004; the science program will start in 2005. An operational lifetime of 20 years is planned.

SOFIA will support a diverse and evolving complement of state-of-theart science instruments. Its spectrometers will have resolutions ranging from ~ 108 down to ~ 100, as needed to measure absorption and emission from astrophysically significant atoms, ions, molecules, aerosols, and solids. This paper describes the spectrometers being developed to fly on SOFIA soon after first light, and summarizes some of the high-spectral resolution investigations expected.

We present and review recent millimeter-wave observations with interferometers, in particular, with the Plateau de Bure interferometer, that stress the importance of high-frequency resolution for studying the chemistry of diffuse interstellar clouds and of post main-sequence circumstellar envelopes. The future impact of new instruments, such as the Atacama Large Millimeter and submillimeter Array (ALMA), is also investigated.

Millimeter and submillimeter astronomy has achieved very high spectral resolution (λ/Δλ ≥ 106-107) over the past 20 years. Broad-band spectral-line surveys at these wavelengths have only taken partial advantage of these capabilities. Such surveys could be more effective with an increase in spectral resolution, accompanied by improvement in the stability and bandwidth of spectrometers and the employment of single-sideband detectors.

In this paper I discuss two examples of the science that can be done with high-resolution spectroscopy at low radio frequencies.

This review talk summarizes the main results obtained from the just completed survey of molecular hydrogen in damped Lyman-a systems (DLAs). Preliminary results based on modeling ionization conditions and chemical network is also presented. The presence of H2 and fine-structure lines of C 1 in 13-20% of DLAs allow one to investigate the physical conditions using the techniques that are commonly used in the studies of the Galactic ISM. It is shown that the DLAs with H2 trace regions with higher density, lower temperature, moderate to high dust depletion, and local star-formation. Absence of H2 in DLAs with moderate dust depletion could just be a simple consequence of lower densities in the systems.

Molecular absorption lines have become an important tool in studying the astrochemistry of the dense and cold interstellar medium in both our own Galaxy and high redshift systems. The sensitivity is to first order only dependent on the observed continuum flux. Apart from a few nearby galaxies, molecular absorption lines have been used to study the molecular ISM in 4 galaxies at redshifts 0.25-0.89. A large number of molecular species and transitions have been observed, allowing a detailed comparison with molecular gas in our own Galaxy. Planned instruments, such as ALMA, will allow studies of a larger number of molecular absorption line systems.

Millimetre-band scans of the frequency space towards optically dim quasars is potentially a highly efficient method for detecting new high red-shift molecular absorption systems. Here we describe scans towards 7 quasars over wide bandwidths (up to 23 GHz) with sensitivity limits sufficient to detect the 4 redshifted absorbers already known. With wider frequency bands, highly efficient searches of large numbers of possibly obscured objects will yield many new molecular absorbers.

We observed OH maser emission at 18cm in a circumnuclear torus surrounding the center of IRAS10173+0828 using the 7 telescopes of MERLIN, together with the Lovell antenna. IRAS10173+0828 is a distant super-luminous far-infrared galaxy. The OH maser emission is remarkably narrow (FWHP = 39km s_1) for its strength, and the 1667 and 1665 MHz lines are well separated. The 1667 transition shows two distinct peaks displaced from one another by 100 km s−1. Using our MERLIN observational results we probe the physics in the circumnuclear torus surrounding the center of IRAS10173+0828, obtain the kinematic properties of the torus, and study the central source.

We report new detections of three H2O megamasers and one kilomaser using the Effelsberg 100-m telescope. Isotropic luminosities are ~50, 300, 1, and 230 L⊙ for Mrk 1066, Mrk 34, NGC 3556, and Arp 299, respectively. Mrk 34 contains the most distant H2O megamaser ever detected in a Seyfert. Our targets in this survey were chosen to fit one of the following criteria: 1) to have a high probability of interaction between the radio jet and the ISM within the central few parsecs of the radio galaxy, yielding masers which arise in local molecular clouds; or 2) to have very bright IRAS sources in which massive star forming regions might yield powerful masers. The ‘jet maser’ sources can provide detailed information about the conditions in the ISM in the central 1-10 pc of AGN. The extra-galactic ‘star formation masers’ can be used to pinpoint and characterize locations of high mass star formation in nearby galaxies. In addition, these sources will help to provide a better understanding of the chemical properties of molecular clouds in extra-galactic systems.