The spectral energy distribution of NGC 1275

An analysis of absolute spectral energy distributions of interstellar gas for a galaxy (NGC 1275) is presented. Infrared spectra data shows heavy reddening. It is proposed that the interstellar gas may be ionized by shock waves or by nonthermal or stellar radiation. It is suggested, that high velocity, emission-line knots are H2 regions in a Perseus cluster galaxy or intergalactic gas cloud seen in projection against NGC 1275

Classical Cosmological Tests for Galaxies of the Hubble Ultra Deep Field

Images of the Hubble Ultra Deep Field are analyzed to obtain a catalog of galaxies for which the angular sizes, surface brightness, photometric redshifts, and absolute magnitudes are found. The catalog contains a total of about 4000 galaxies identified at a high signal-to-noise ratio, which allows the cosmological relations angular size{redshift and surface brightness-redshift to be analyzed. The parameters of the evolution of linear sizes and surface brightness of distant galaxies in the redshift interval 0.5-6.5 are estimated in terms of a grid of cosmological models with different density parameters. The distribution of photometric redshifts of galaxies is analyzed and possible superlarge inhomogeneities in the radial distribution of galaxies are found with scale lengths as large as 2000 Mpc.Comment: 23 pages, 9 figures, 1 tabl

Quasi-simultaneous observations of the BL Lac object MK 501 in X-ray, UV, visible, IR and radio frequencies

Quasi-simultaneous observations of the BL Lacertae (Lac) objects MK 501 were performed for the first time at X-ray, ultraviolet, visible, infrared, and radio frequencies. The observed spectral slope from the X-ray to UV regions is positive and continuous, but that from the mid UV to visible light region becomes gradually flat and possibly turns down toward lower frequencies; the optical radio emission can not be accounted for by a single power law. Several theoretical models were considered for the emission mechanism. A quantitative comparison was performed with the synchrotron-self-Compton model; the total spectrum is found consistent with this model. The spectrum from visible light to X-ray is consistent with synchrotron radiation or with inverse-Compton scattering by a hot thermal cloud of electrons. The continuity of the spectral slope from X-ray to UV implied by the current data suggests that the previous estimates of the total luminosity of this BL Lac object is underestimated by a factor of about three or four

Compressive Strength of Concrete Containing Milled Glass as Partial Substitute for Cement

This work reports the outcome of an experiment carried out by using milled glass (MG) of varying percentages (20%, 40% and 60% by weight)of cement in concrete making. MG was sourced for and milled to required fineness. The concrete was batched with mix ratio of 1։2։ 4. Concrete Cube specimens produced were allowed to cure for 7-28 days and compressive strength, slump and setting time tests were carried out and were compared with those of conventional concrete (0% MG). Results obtained showed that compressive strength of the concrete increased with increase in length of curing age, but decreased as the percentage of MG increased. However, the strength still remained in the allowable range of workability for concrete in line with British standard. MG replacement of 20% was found to be the most suitable mix considering the strength and safe use of the concrete. It was concluded that MG replacement of 20% showed no significant loss in strength compared to the control sample and is stable and could be acceptable in most concrete. At the long run. Waste glass that currently constitutes waste concern in built environment in Nigeria can best be managed through alternative use in concrete production

The H Beta Index as an Age Indicator of Old Stellar Systems: The Effects of Horizontal-Branch Stars

The strength of the H$\beta$ index has been computed for the integrated spectra of model globular clusters from the evolutionary population synthesis. These models take into account, for the first time, the detailed systematic variation of horizontal-branch (HB) morphology with age and metallicity. Our models show that the H$\beta$ index is significantly affected by the presence of blue HB stars. Because of the contribution from blue HB stars, the H$\beta$ does not monotonically decrease as metallicity increases at a given age. Instead, it reaches a maximum strength when the distribution of HB stars is centered around 9500 K, the temperature where the H$\beta$ index becomes strongest. Our models indicate that the strength of the H$\beta$ index increases as much as 0.75 {\AA} due to the presence of blue HB stars. The comparison of the recent Keck observations of the globular cluster system in the Milky Way Galaxy with those in giant elliptical galaxies, NGC 1399 and M87, shows a systematic shift in the H$\beta$ against metallicity plane. Our models suggest that this systematic difference is understood if the globular cluster systems in giant elliptical galaxies are several billion years older, in the mean, than the Galactic counterpart. Further observations of globular cluster systems in the external galaxies from the large ground-based telescopes and space UV facilities will enable to clarify whether this difference is indeed due to the age difference or other explanations are also possible.Comment: 21 pages, 8 figures, Accepted for publication in the Astronomical Journal, August 2000 issue, Postscript files are available at http://csaweb.yonsei.ac.kr/~hclee/Hbet

Diffraction-limited imaging with ground-based optical telescopes

The construction of diffraction-limited images with ground-based optical telescopes by means of closure-phase observations is explored. The effect of redundant baselines on closure-phase observations is analyzed, and it is shown that for bright objects a nonredundant-mask approach is superior to the use of the full aperture. Observations of closure phase with a nonredundant mask on the 200 in. Hale Telescope are presented, and compared with the predictions of atmospheric seeing theory. It is demonstrated that fairly complex images can be constructed from closure-phase observations alone

On the Nature of Ryle and Bailey's Candidate Star for the Pulsating Radio Source CP 1919

The energy distribution and spectrum of the "blue" star near CP 1919 indicate that it is a normal early F, main-sequence star and therefore is not likely to be related to the radio source. No regular variations were found in the light from the star, to within an accuracy of a few tenths of 1 per cent