A High Current Proton Linac with 352 MHz SC Cavities

A proposal for a 10-120 mA proton linac employing superconducting beta-graded, CERN type, four cell cavities at 352 MHz is presented. The high energy part (100 MeV-1 GeV) of the machine is split in three beta-graded sections, and transverse focusing is provided via a periodic doublet array. All the parameters, like power in the couplers and accelerating fields in the cavities, are within the state of the art, achieved in operating machines. A first stage of operation at 30 mA beam current is proposed, while the upgrade of the machine to 120 mA operation can be obtained increasing the number of klystrons and couplers per cavity. The additional coupler ports, up to four, will be integrated in the cavity design. Preliminary calculations indicate that beam transport is feasible, given the wide aperture of the 352 MHz structures. A capital cost of less than 100 M$at 10 mA, reaching up to 280 M$ for the 120 mA extension, has been estimated for the superconducting high energy section (100 MeV-1 GeV). The high efficiency of the proposed machine, reaching 50% at 15 mA, makes it a good candidate for proposed nuclear waste incineration facilities and Energy Amplifier studies.Comment: 9 Pages, 4 figures, LaTeX2e, html version found from http://hptesla.mi.infn.it/~pierini/publication_list.html . To Appear in the Proceedings of the 1996 LINAC Conference, Geneve, August 26-30 199

1.65 micrometers (H-band) surface photometry of galaxies. III: observations of 558 galaxies with the TIRGO 1.5m telescope

We present near-infrared H-band (1.65 micron) surface photometry of 558 galaxies in the Coma Supercluster and in the Virgo cluster. This data set, obtained with the Arcetri NICMOS3 camera ARNICA mounted on the Gornergrat Infrared Telescope, is aimed at complementing, with observations of mostly early-type objects, our NIR survey of spiral galaxies in these regions, presented in previous papers of this series. Magnitudes at the optical radius, total magnitudes, isophotal radii and light concentration indices are derived. We confirm the existence of a positive correlation between the near-infrared concentration index and the galaxy H-band luminosity. (Tables 1 and 2 are only available in electronic form upon request to [email protected])Comment: 12 pages, 6 figures. Accepted for publication in A&A

Dust Attenuation in Late-Type Galaxies. I. Effects on Bulge and Disk Components

We present results of new Monte Carlo calculations made with the DIRTY code of radiative transfer of stellar and scattered radiation for a dusty giant late-type galaxy like the Milky Way, which illustrate the effect of the attenuation of stellar light by internal dust on the integrated photometry of the individual bulge and disk components. Here we focus on the behavior of the attenuation function, the color excess, and the fraction of light scattered or directly transmitted towards the outside observer as a function of the total amount of dust and the inclination of the galaxy, and the structure of the dusty interstellar medium (ISM) of the disk. We confirm that dust attenuation produces qualitatively and quantitatively different effects on the integrated photometry of bulge and disk, whatever the wavelength. In addition, we find that the structure of the dusty ISM affects more sensitively the observed magnitudes than the observed colors of both bulge and disk. Finally, we show that the contribution of the scattered radiation to the total monochromatic light received by the outside observer is significant, particularly at UV wavelengths, even for a two-phase, clumpy, dusty ISM. Thus understanding dust scattering properties is fundamental for the interpretation of extragalactic observations in the rest-frame UV.Comment: 62 pages, 28 eps-figures, 1 table, accepted for publication in ApJ Main Journa

1.65 micrometers (H-band) surface photometry of galaxies. IV:observations of 170 galaxies with the Calar Alto 2.2m telescope

We present near-infrared (H band) surface photometry of 170 galaxies, obtained in 1997 using the Calar Alto 2.2m telescope equipped with the NICMOS3 camera MAGIC. The majority of our targets are selected among bright members of the Virgo cluster, however galaxies in the A262 and Cancer clusters and in the Coma/A1367 supercluster are also included. This data set is aimed at complementing the NIR survey in the Virgo cluster discussed in Boselli et al. (1997) and in the Coma Supercluster, presented in Papers I, II and III of this series. Magnitudes at the optical radius, total magnitudes, isophotal radii and light concentration indices are derived. (Tables 1 and 2 are only available in electronic form upon request to [email protected])Comment: 11 pages, 6 figures. Accepted for publication in A&A

On the Maximum Luminosity of Galaxies and Their Central Black Holes: Feedback From Momentum-Driven Winds

We investigate large-scale galactic winds driven by momentum deposition. Momentum injection is provided by (1) radiation pressure produced by the continuum absorption and scattering of UV photons on dust grains and (2) supernovae. UV radiation can be produced by a starburst or AGN activity. We argue that momentum-driven winds are an efficient mechanism for feedback during the formation of galaxies. We show that above a limiting luminosity, momentum deposition from star formation can expel a significant fraction of the gas in a galaxy. The limiting, Eddington-like luminosity is $L_{\rm M}\simeq(4f_g c/G) \sigma^4$, where $\sigma$ is the galaxy velocity dispersion and $f_g$ is the gas fraction. A starburst that attains $L_{\rm M}$ moderates its star formation rate and its luminosity does not increase significantly further. We argue that ellipticals attain this limit during their growth at $z \gtrsim 1$ and that this is the origin of the Faber-Jackson relation. We show that Lyman break galaxies and ultra-luminous infrared galaxies have luminosities near $L_{\rm M}$. Star formation is unlikely to efficiently remove gas from very small scales in galactic nuclei, i.e., scales much smaller than that of a nuclear starburst. This gas is available to fuel a central black hole (BH). We argue that a BH clears gas out of its galactic nucleus when the luminosity of the BH itself reaches $\approx L_{\rm M}$. This shuts off the fuel supply to the BH and may also terminate star formation in the surrounding galaxy. As a result, the BH mass is fixed to be $M_{\rm BH}\simeq (f_g \kappa_{\rm es}/\pi G^2)\sigma^4$, where $\kappa_{\rm es}$ is the electron scattering opacity. This limit is in accord with the observed $M_{\rm BH}-\sigma$ relation. (Abridged)Comment: 21 pages, emulateapj, accepted to ApJ, minor changes to discussio