[en] Medium-resolution infrared CVF spectra of the 2.3-μm CO absorption feature sensitive to stellar luminosity class have been obtained in a sample of elliptical galaxies and standard stars. These are the highest quality spectra of this feature published and have the potential of determining relative numbers of late-type giants and cool main-sequence dwarfs in elliptical galaxies more accurately than previous narrow-band filter measurements. A synthesis technique based on data on Baade's window is introduced and the limits on numbers of low-mass stars are investigated. (author)

[en] The discovery of a diffuse Lyα flux from NGC 1275 is reported. The emission is probably due to the optical filaments surrounding the galaxy which are due to the cooling flow of intracluster gas. The lack of any detectable 1250-1900 A stellar continuum limits the formation rate of stars more massive than 3 solar masses to less than 6 solar masses yr^-1, or 2 per cent of the accretion rate. (author)

[en] The Einstein imaging proportional counter observations of the poor cluster of galaxies centered on the radio galaxy Hydra A are examined. From the surface brightness profile, it is found that the X-ray-emitting gas in the Hydra A cluster must be condensing out of the intracluster medium at a rate of 600 solar masses/yr. This is one of the largest mass deposition rates observed in a cluster of galaxies. The ratio of gas mass to stellar mass is compared for a variety of systems, showing that this ratio correlates with the gas temperature. 55 refs

[en] The X-ray source 3A0745-191 is identified with intracluster gas surrounding the giant galaxy containing the radio source, PKS 0745-191, which lies at z=0.1. The gas is cooling at the unprecedented rate of 1000 solar masses yr^-1. Optical line-emitting gas extends more than 10 kpc from the centre of the galaxy and corroborates the high mass-flow rate. The optical spectrum is similar to that of distant 3CR radio galaxies reported by others. It is concluded that the formation of a giant galaxy is being observed. (author)

[en] The Einstein X-ray data for the two luminous infrared galaxies, Arp 220 and Markarian 231 have been analyzed. There is an X-ray source about 1 arcmin from the position of Arp 220 that is probably associated with it. Mrk 231 was not detected. The size of the source and its soft X-ray spectrum implies that the bulk of the X-ray emission from Arp 220 cannot be coming from the obscured active nucleus at the galaxy's center. The absence of strong X-ray emission from the active nuclei in Arp 220 and Mrk 231 suggests that there must be more line-of-sight absorption to the active nuclei than is inferred from many of the absorption indicators available. 32 references

[en] The X-ray spectrum of Seyfert 1 galaxies is characterized by a hard power-law spectrum. It is often postulated that this maintains a Compton-heated two-phase Broad-Line Region (BLR) around the central source. It is shown here that the strong excess soft X-ray emission observed in MKN 841 and other Seyfert galaxies invalidates this model if the BLR is spherically symmetric. Alternatives are proposed. (author)

[en] The focal plane crystal spectrometer (FPCS) on the Einstein Observatory has been used to perform a high-resolution spectroscopic search for oxygen X-ray line emission from four active galaxies: Fairall 9, Mrk 421, Mrk 501, and PKS 0548 - 322. Specifically, O VIII Ly-alpha and Ly-beta, whose unredshifted energies are 653 and 775 eV, respectively, were sought. No narrow-line emission was detected within the energy bands searched. Upper limits are calculated on the line flux from these sources of 30 eV equivalent width and use a photoionization model to place corresponding upper limits on the densities of diffuse gas surrounding the active nuclei. The upper limits on gas density range from about 0.02-50/cu cm and probe various radial distances from the central source. This is the first time high-resolution X-ray spectroscopy has been used to place constraints on the intercloud medium in active galaxies. 57 refs

[en] We present X-ray, optical and ultraviolet observations of the rich cluster A2597 and confirm the presence of a central cooling flow. The intra-cluster gas is cooling at a rate of ∼ 370 solar masses yr^-1 and we observe extended optical line-emitting gas around the central galaxy over a radial distance of ∼ 25 kpc. Examination of the blue continuum spectrum of the central galaxy indicates that only <0.1 solar mass yr^-1 of detectable star formation is taking place. These stars are restricted to the mass range 1-3 solar masses. The emission-line gas cannot be photoionized by OB stars. (author)

[en] A statistically complete sample of galaxy clusters is presented which also has complete X-ray temperature information. Using this sample, the cluster bolometric luminosity and temperature functions are derived. The temperature function constrains the shape and amplitude of the mass fluctuation power spectrum. For a power law, i.e., with the fluctuation power spectrum proportional to k exp n, n = -(1.7 + 0.65, - 0.35), and an amplitude is obtained which implies that the rms value of δ-M/M is 0.59 + or - 0.02 on a scale of 8/h Mpc at the present epoch. 31 refs

[en] The density profiles of the hot interstellar gas in 18 galaxies, mostly ellipticals, have been determined using X-ray data from the Einstein Observatory. Radiative cooling is important throughout most of this gas leading to mass-deposition rates of between 0.02 and 3 solar masses yr^-1. There are problems in determining the nature of the resultant cooling flows since these mass-deposition rates are significantly less than the expected injection of gas from stellar mass loss, and supernova heating is not accounted for. Possible solutions involving a multi-phase medium and cooling outflows, are suggested. (author)