Abstract. -The Far Infrared (FIR) properties of galaxies which are members of compact groups bear relevant information on the dynamical status and the physical properties of these structures. All studies published so far have been undermined by the poor sensitivity and spatial resolution of the IRAS-PSC and IRAS Sky Survey data. We used the HIRAS software available at the IRAS server at the Laboratory for Space Research in Groningen to fully exploit the redundancy of the IRAS data and to approach the theoretical diffraction limit of IRAS. Among the 97 groups which were observed by IRAS, 62 were detected in at least one band, while reliable upper limits were derived for all the others. Among the detected groups, 49 were fully or partially resolved, i.e. it was possible to discriminate which member or members emit most of the FIR light. At 60 µm, for instance, 87 individual sources were detected in 62 groups. In order to ease the comparison with data obtained at other wavelengths -and in particular in the X and radio domains -we give co-added and HIRAS maps for all the detected groups.

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Abstract. A system for measuring the two-dimensional (2-D) spatial distribution of atmospheric CO 2 over complex industrial sites and urban areas on the order of 1 to 30 km 2 every few minutes with a spatial resolution as high as tens of meters has been developed and demonstrated over the past 3 years. The greenhouse gas (GHG) laser imaging tomography experiment (GreenLITE™) provides improved measurement capabilities for applications ranging from automated 24∕7 monitoring of ground carbon storage/sequestration (GCS) sites to long-duration real-time analyses of GHG sources and sinks in urban environments. GreenLITE combines a set of sensors based on an intensity modulated continuous wave approach with 2-D sparse tomographic reconstruction mechanisms to compute a 2-D map of CO 2 concentrations over the area of interest. GreenLITE systems have recently been deployed at a number of test facilities, including a 4000-h demonstration at a GCS site in Illinois and an urban deployment in Paris, France, from November 2015 to the present. This paper describes the GreenLITE concept and the associated measurement capabilities and provides proof of concept results and analyses of observations from both short-term tests as well as longer-term industrial and urban deployments. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

The ISOPHOT Serendipity Survey utilizes the slew time between ISO's pointed observations with strip scanning measurements of the sky in the far-infrared at 170 m. The slews contain information about two fundamentally different types of objects, namely (almost) unresolved galactic and extragalactic far-infrared sources as well as extended regions of galactic cirrus emission. Since the structure of the obtained data is almost unique, the development of dedicated software to extract astrophysically interesting parameters for the crossed sources is mandatory. Data analysis is currently in its early stages and concentrates on the detection of point sources. First results from an investigation of a high galactic latitude field near the North Galactic Pole indicate that the detection completeness with respect to previously known IRAS sources will be almost 100 % for sources with f1OOm >2 Jy, dropping below 50% for flOOpm < 1.5 Jy. Nevertheless, even faint sources down to a level of f17Om 1 Jy can be detected. Since the majority of the detected point sources are galaxies, the Serendipity Survey will result in a large database of 2000 galaxies.

We present the position and references (if available) of all the galaxies of the Shakhbazian survey being the largest survey of compact galaxy groups. For the estimation of the coordinates the Digitized Sky Survey was used. This paper contains the data of 48 Shakhbazian groups north of δ > + 2deg;30' (Shkh 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 22, 23, 25, 26, 28, 29, 31, 34, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56).

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Laser absorption spectroscopy (LAS) has been used over the last several decades for the measurement of trace gasses in the atmosphere. For over a decade, LAS measurements from multiple sources and tens of retroreflectors have been combined with sparse-sample tomography methods to estimate the 2-D distribution of trace gas concentrations and underlying fluxes from point-like sources. In this work, we consider the ability of such a system to detect and estimate the position and rate of a single point leak which may arise as a failure mode for carbon dioxide storage. The leak is assumed to be at a constant rate giving rise to a plume with a concentration and distribution that depend on the wind velocity. We demonstrate the ability of our approach to detect a leak using numerical simulation and also present a preliminary measurement.

The differences between optical and X-ray structures of galaxy clusters are discussed. We analyse in detail 7 Abell clusters. There is an increasing number of arguments in favour of different distributions of galaxies, gas, and dark matter in many dusters. We argue that most clusters present sub-structures at least in the gaseous and galactic components and, moreover, the subclustering of different components does not always coincide. Such arguments strongly support the idea that most galaxy clusters are by far more complex systems than accepted until now and are usually not in an hydrostatic isothermal equilibrium.Key words: galaxy clusters -structures -dominant galaxies A A A subject classification: 160 IntroductionGalaxy clusters are normally characterized by the BM types I, 11, and I11 or by the RS types cD, B, L, F, and I. Correlations between these morphological cluster types and the physical properties of the clusters are expected. This expectation concerns among others the X-ray properties. However many authors find only marginal evidence for such a correlation. In this connection the question arises which kind of observation is better suited for the description of the physical properties of galaxy clusters. Very often it is argued that optical observations are plagued by projection effects and by small number statistics. It is assumed that X-ray observations of clusters can overcome these problems because the relaxation time-scale of the X-ray emitting gas is much shorter than the age of a cluster. Thus, it is usually assumed that the gas is relaxed and the X-ray emission can be used as a tracer of the gravitational potential of clusters. A second point is that many galaxy clusters are observed to be commonly bright in X-rays due to the high gas densities in their cores. Therefore, they should be detected out to large redshifts making them useful probes of cosmological studies.Since all components of a given cluster share the total gravitational potential, it is assumed that both the intra-cluster medium and galaxy number densities are related to the potential well of the cluster in a similar way, or that dark matter, hot gas, and galaxy distribution evolve in a tightly coupled way (Frenk et al. 1995). Traditionally an hydrostatic equilibrium of both the hot intra-cluster gas and the galaxies with the binding cluster potential is assumed (e.g., Wu 1994, Lubin and Bahcalll993).In connection with all these theoretical considerations the distributions of different components in clusters (galaxies, gas, and dark matter) should show the same behaviour. The usefulness of the observation of one or more components is considered to be determined only by the possibility of observations. In principle, results from all such kinds of observations -galaxy distribution or X-ray emissivity, for example -should lead to equivalent results.However, the very observation of sub-structures in the majority of rich clusters, the different scale lengths of the various components in a cluster, or the so-called &problem, point to ...