Extragalactic OH megamasers in strong IRAS sources

From the OH and HI survey of the strongest far infrared IRAS sources, 3 new powerful OH megamasers were discovered in Arp 143, IRAS 1510+0724 and in the uncatalogued IRAS source, IRAS 17208-0014. The HI line, the OH 1667 and 1665 MHz main lines and the 21 cm continuum observations were made with Nancy radio telescope. The optical spectra and images were obtained at the European Southern Observatory. The spectra are displayed in figures together with the main IR and OH properties of the 8 megamasers detected up to now, including IC 4553, NGC 3690 and Mrk 231, Mrk 273 and III ZW35

A Universal Neutral Gas Profile for Nearby Disk Galaxies

Based on sensitive CO measurements from HERACLES and HI data from THINGS, we show that the azimuthally averaged radial distribution of the neutral gas surface density (Sigma_HI + Sigma_H2) in 33 nearby spiral galaxies exhibits a well-constrained universal exponential distribution beyond 0.2*r25 (inside of which the scatter is large) with less than a factor of two scatter out to two optical radii r25. Scaling the radius to r25 and the total gas surface density to the surface density at the transition radius, i.e., where Sigma_HI and Sigma_H2 are equal, as well as removing galaxies that are interacting with their environment, yields a tightly constrained exponential fit with average scale length 0.61+-0.06 r25. In this case, the scatter reduces to less than 40% across the optical disks (and remains below a factor of two at larger radii). We show that the tight exponential distribution of neutral gas implies that the total neutral gas mass of nearby disk galaxies depends primarily on the size of the stellar disk (influenced to some degree by the great variability of Sigma_H2 inside 0.2*r25). The derived prescription predicts the total gas mass in our sub-sample of 17 non-interacting disk galaxies to within a factor of two. Given the short timescale over which star formation depletes the H2 content of these galaxies and the large range of r25 in our sample, there appears to be some mechanism leading to these largely self-similar radial gas distributions in nearby disk galaxies.Comment: 7 pages, 4 figures, accepted for publication in the Astrophysical Journa

The Distance to NGC 5128 (Centaurus A)

In this paper we review the various high precision methods that are now available to determine the distance to NGC 5128. These methods include: Cepheids, TRGB (tip of the red giant branch), PNLF (planetary nebula luminosity function), SBF (surface brightness fluctuations) and Long Period Variable (LPV) Mira stars. From an evaluation of these methods and their uncertainties, we derive a best-estimate distance of 3.8 +- 0.1 Mpc to NGC 5128 and find that this mean is now well supported by the current data. We also discuss the role of NGC 5128 more generally for the extragalactic distance scale as a testbed for the most direct possible comparison among these key methods.Comment: in press PASA; minor text change

Extragalactic database. VII Reduction of astrophysical parameters

The Lyon-Meudon Extragalactic database (LEDA) gives a free access to the main astrophysical parameters for more than 100,000 galaxies. The most common names are compiled allowing users to recover quickly any galaxy. All these measured astrophysical parameters are first reduced to a common system according to well defined reduction formulae leading to mean homogeneized parameters. Further, these parameters are also transformed into corrected parameters from widely accepted models. For instance, raw 21-cm line widths are transformed into mean standard widths after correction for instrumental effect and then into maximum velocity rotation properly corrected for inclination and non-circular velocity. This paper presents the reduction formulae for each parameter: coordinates, morphological type and luminosity class, diameter and axis ratio, apparent magnitude (UBV, IR, HI) and colors, maximum velocity rotation and central velocity dispersion, radial velocity, mean surface brightness, distance modulus and absolute magnitude, and group membership. For each of these parameters intermediate quantities are given: galactic extinction, inclination, K-correction etc.. All these parameters are available from direct connexion to LEDA (telnet lmc.univ-lyon1.fr, login: leda, no passwd OR http://www-obs.univ-lyon1.fr/leda ) and distributed on a standard CD-ROM (PGC-ROM 1996) by the Observatoire de Lyon via the CNRS (mail to [email protected]).Comment: 13 pages, 12 figures. The CDROM of the extragalactic database LEDA is available by mailing to: [email protected]

Shape of the Galactic Orbits in Clusters

A kinematical analysis applied to a sample of galaxy clusters indicates that the differences between the velocity distribution of elliptical and spiral galaxies are associated with the shape of their orbit families. The orbital anisotropies present on each morphological population could be measured with the use of a parameter which is the ratio of the radial and tangential velocity dispersions, and can be recovered through the observed line-of-sight velocity distribution. When a Gaussian velocity distribution is assumed, having different dispersions along the radial and tangential directions, we conclude that the orbits of elliptical galaxies in clusters are close to radial, while spirals have more circular shaped or isotropic orbits. Lenticulars galaxies shares an intermediate orbital parameter, between spirals and ellipticals.Comment: 23 pages including 6 EPS-figures, and 4 tables. Accepted for publication by ApJ, April 199