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The spatial distribution of clusters of galaxies and the large scale structure of the universe is investigated. Correlations in the spatial cluster distribution are much stronger than those seen for galaxies, and over scales much larger than previously anticipated. The following main studies are completed and published; (1) The determination of the correlation functions of rich clusters of galaxies, and its dependence on richness and other parameters. Very large scale structure exists in the universe, and rich clusters participate in this structure more efficiently than galaxies. (2) A complete catalog of superclusters, is determined. The selection criteria is that of a volume density enhancement, and is done in 3 dimensions. (3) The giant galaxy void in Bootes is found to be surrouned by rich, large superclusters from the catalog described above. (4) A very large scale void of rich clusters of galaxies is found in the study of the spatial distribution of rich clusters.
Gravitational radiation from galactic and extragalactic astrophysical sources will induce spatial strains in the solar system, strains which can be measured directly by the Doppler radio link to distant spacecraft. Current noise sources in Pioneer and Voyager Doppler data are delineated and a comparison is made with expected signal levels from gravitational wave sources. The main conclusion is that it is possible to detect gravitational radiation with current DSN hydrogen maser systems stable in fractional frequency + or - 2 x 10 to the minus 14th power over 1000 sec. In the future, however, a serious Doppler observational program in gravitational wave astronomy will require frequency systems stable to at least 10 to the minus 16th power, but at the same time the current single frequency S-band uplink transmission will have to be replaced by a dual frequency capability.
The space interferometry mission (SIM), for launch in 2004, is expected to determine the positions of point sources to a global accuracy of 4 microarcsec, and an accuracy of 1 microarcsec over small angles. The instrument will reach 200 mag in 3 x 10(exp 4) s and has a nominal lifetime of five years. A nulling capability will be provided and synthesis imaging and near-infrared capabilities are being considered. These capabilities will extend those of the Hipparcos mission by almost three orders of magnitude in every sense. The NASA's expectation for the scientific return from the SIM mission is outlined in terms of the areas of stellar physics, galactic structure and extragalactic astrophysics, including the distance scale problem.
A radio interferometer array in space providing high dynamic range images with unprecedented angular resolution over the broad frequency range from 0.030 - 30 MHz will open new vistas in solar, terrestial, galactic, and extragalactic astrophysics.
The development of high-contrast capabilities has long been recognized as one of the top priorities for the VLTI (Very Large Telescope Interferometer). As of today, the VLTI routinely achieves contrasts of a few 103 in the near-infrared with PIONIER (Precision Integrated-Optics Near-infrared Imaging ExpeRiment) (H band) and GRAVITY (K band). Nulling interferometers in the northern hemisphere and non-redundant aperture masking experiments have, however, demonstrated that contrasts of at least a few 10 (sup -3) are within reach using specific beam combination and data acquisition techniques. In this paper, we explore the possibility to reach similar or higher contrasts on the VLTI. After reviewing the state-of-the-art in high-contrast infrared interferometry, we discuss key features that made the success of other high-contrast interferometric instruments (e.g., integrated optics, nulling, closure phase, and statistical data reduction) and address possible avenues to improve the contrast of the VLTI by at least one order of magnitude. In particular, we discuss the possibility to use integrated optics, proven in the near-infrared, in the thermal near-infrared (L and M bands, 3-5 microns), a sweet spot to image and characterize young extra-solar planetary systems. Finally, we address the science cases of a high-contrast VLTI imaging instrument and focus particularly on exoplanet science (young exoplanets, planet formation, and exozodiacal disks), stellar physics (fundamental parameters and multiplicity), and extragalactic astrophysics (active galactic nuclei and fundamental constants). Synergies and scientific preparation for other potential future instruments such as the Planet Formation Imager are also briefly discussed. This project is called Hi-5 for High-contrast Interferometry up to 5 microns.
Hi-5 is a high-contrast (or high dynamic range) infrared imager project for the VLTI. Its main goal is to characterize young extra-solar planetary systems and exozodiacal dust around southern main-sequence stars. In this paper, we present an update of the project and key technology pathways to improve the contrast achieved by the VLTI. In particular, we discuss the possibility to use integrated optics, proven in the near-infrared, in the thermal near-infrared (L and M bands, 3-5 μm) and advanced fringe tracking strategies. We also address the strong exoplanet science case (young exoplanets, planet formation, and exozodiacal disks) offered by this wavelength regime as well as other possible science cases such as stellar physics (fundamental parameters and multiplicity) and extragalactic astrophysics (active galactic nuclei and fundamental constants). Synergies and scientific preparation for other potential future instruments such as the Planet Formation Imager are also briefly discussed.
Solar, stellar, galactic and extragalactic neutrino astrophysics, discussing observational data on sources, nuclear processes, detection and cosmology
Neutrino astrophysics - supermassive stars, quasars, and extragalactic radio sources
One of the hallmarks of SIM's few-milliarcsecond astrometric precision is its ability to obtain accurate parallax measurements across more than half of the Galaxy. The "open and globular" project obtains parallax distances to a set of star clusters. One important, goal is to pinpoint the zeropoint of the distance scale for main-sequence fitting. Another goal is to improve stellar evolutionary isochrones and integrated light models. Another goal is to use the clusters themselves to address unsolved problems of late-stage stellar evolution and Galactic and extragalactic chemical evolution. The clusters to be observed are chosen to span the widest possible range of abundance and age, to be as rich as possible, and to be as well-studied as possible.
We present the Heraklion Extragalactic Catalogue, or HECATE, an all-sky value-added galaxy catalogue, aiming to facilitate present and future multiwavelength and multi messenger studies in the local Universe. It contains 204 733 galaxies up to a red shift of 0.047 (D200 Mpc), and it is>50 per cent complete in terms of the B-band luminosity density at distances in the0–170 Mpc range. By incorporating and homogenizing data from astronomical data bases and multiwavelength surveys, the catalogue offers positions, sizes, distances, morphological classifications, star formation rates, stellar masses, metallicities, and nuclear activity classifications. This wealth of information can enable a wide range of applications, such as (i) demographic studies of extragalactic sources, (ii) initial characterization of transient events, and (iii) searches for electromagnetic counterparts of gravitational-wave events. The catalogue is publicly available to the community at a dedicated portal, which will also host future extensions in terms of the covered volume and data products.
We present the analysis of the magnetic field (B-field) structure of galaxies measured with far-infrared (FIR) and radio (3 and 6 cm) polarimetric observations. We use the first data release of the Survey of extragALactic magnetiSm with SOFIA (SALSA) of 14 nearby (< 20 Mpc) galaxies with resolved (5′′ − 18′′; 90 pc–1 kpc) imaging polarimetric observations using SOFIA/HAWC+ from 53 to 214 μm. We compute the magnetic pitch angle (Ψ B ) profiles as a function of the galactocentric radius. We introduce a new magnetic alignment parameter (ζ) to estimate the disordered-to-ordered ratio of spiral B -fields. We find FIR and radio wavelengths to not generally trace the same B -field morphology in galaxies. The Ψ B profiles tend to be more ordered across all galactocentric radii in radio (ζ 6cm = 0.93 ± 0.03) than in FIR (ζ 154μm = 0.84 ± 0.14). For spiral galaxies, FIR B-fields are 2−75% more turbulent than the radio B -fields. For starburst galaxies, we find that FIR polarization is a better tracer of the B -fields along the galactic outflows than radio polarization. Our results suggest that the B -fields associated with dense, dusty, turbulent star-forming regions, those traced at FIR, are less ordered than warmer, less-dense regions, those traced at radio, of the interstellar medium. The FIR B -fields seem to be more sensitive to the activity of the star-forming regions and molecular clouds within a vertical height of few hundred pc in the disk of spiral galaxies than the radio B -fields.
Progress made in the following areas is discussed: low energy ion and electron experiments; instrument design for current experiments; magnetospheric measurement of particles; ion measurement in the earth plasma sheet; abundance measurement; X-ray data acquisition; high energy physics; extragalactic astronomy; compact object astrophysics; planetology; and high energy photon detector technology.
Topics considered include: Calibration and Astrometry Pipeline; Astrometry Anomaly Analysis; The STAT pipeline and software analysis tools; GTO Program; Parallaxes of Astrophysically Interesting Objects; HST- Hipparcos Extragalactic Link; Ground-Based Observations of Radial Velocities; GTO Globular Cluster Internal Motions; and GTO Hyades Cluster Member FGS Parallaxes.
A direct link to an extragalactic reference system is considered as being a principle aim of the global astrometric interferometer for astrophysics (GAIA) mission. The data available from an extragalactic data base and a quasi stellar object (QSO) catalog were used to obtain an estimation of the number of QSO link candidates. The quality of presently available data and the expected accuracy of the extragalactic link are discussed. It is concluded that at least 150 QSO's must be observed by GAIA in order to guarantee an accuracy of better than 1 microarcsec/year for the link. New observations will be needed before the GAIA launch in order to reduce uncertainties in the positions, magnitudes and redshifts for some known quasars. The variability of QSO's with magnitudes near the GAIA observation limit can raise a potential problem. The motions of nearby QSO's are expected to be much smaller than 2 microarcsec/year, and therefore, will not affect the accuracy of the link in the proposed GAIA mission.
The prime objectives of the Rossi X-ray Timing Explorer (RXTE) are the study of astrophysical compact objects: black holes (galactic and extragalactic), many types of neutron stars, and accreting white dwarfs. RXTE's capability for rapid timing is unique among all past and present X-ray observatories. It has enabled qualitatively new discoveries about dynamical timescale phenomena related to neutron stars and black holes. These phenomena probe basic physics in the most extreme environments of gravity, density, and magnetic fields. The observations to date are a public archive for studying questions not addressed in the initial studies. Proposed future observations emphasize the discovery of additional millisecond pulsars and finding the answers to questions about low mass X-ray binaries and black holes.
The prime scientific objectives of the Rossi X-Ray Timing Explorer (RXTE) were the study of astrophysical compact objects: black holes (galactic and extragalactic), many types of neutron stars, and accreting white dwarfs. RXTE was successful in achieving its original observing objectives of large area and high time resolution observations with broadband (2-200 keV) spectra, scheduled flexibly enough to enable observations of targets of opportunity on any timescale greater than a few hours. These capabilities enabled qualitatively new discoveries about dynamical timescale phenomena related to neutron stars and black holes, phenomena which probe basic physics in the most extreme environments of gravity, density, and magnetic fields. RXTE has extended its lifetime by applying the proportional counter area selectively and maintains schedule flexibility by making use of the distribution of targets around the sky. Proposed future observations emphasize opportunity to discover and study additional millisecond pulsars, pursue the high frequency quasi-periodic oscillations in black hole transients, and connect high frequency phenomena with longer term characteristics. RXTE will continue to strongly support, for both galactic and extragalactic targets, combining RXTE observations with other wavelengths (from IR to TeV) or with other capabilities, such as high spectral resolution.