Weight filtration on the cohomology of complex analytic spaces

We extend Deligne's weight filtration to the integer cohomology of complex analytic spaces (endowed with an equivalence class of compactifications). In general, the weight filtration that we obtain is not part of a mixed Hodge structure. Our purely geometric proof is based on cubical descent for resolution of singularities and Poincar\'e-Verdier duality. Using similar techniques, we introduce the singularity filtration on the cohomology of compactificable analytic spaces. This is a new and natural analytic invariant which does not depend on the equivalence class of compactifications and is related to the weight filtration.Comment: examples added + minor correction

Large-scale HI in nearby radio galaxies: segregation in neutral gas content with radio source size

We present results of a study of neutral hydrogen (HI) in a complete sample of nearby non-cluster radio galaxies. We find that radio galaxies with large amounts of extended HI (M_HI >= 10^9 M_solar) all have a compact radio source. The host galaxies of the more extended radio sources, all of Fanaroff & Riley type-I, do not contain these amounts of HI. We discuss several possible explanations for this segregation. The large-scale HI is mainly distributed in disk- and ring-like structures with sizes up to 190 kpc and masses up to 2 x 10^10 M_solar. The formation of these structures could be related to past merger events, although in some cases it may also be consistent with a cold-accretion scenario.Comment: 4 pages, 2 figures. Accepted for publication in A&A Letters. A version with full resolution figures can be found at http://www.astro.rug.nl/~emonts/emonts_HIletter_jan07.pd

Senior Design Final Report: Destination Distillation

The goal of this project is to retrofit the distillation column owned by the Trinity Engineering Department in order to make it safe and easy to use in the learning environment. A final design has been agreed upon, parts have been ordered, installed and tested, and the final design is complete and determined to be working as it should

The Mass-to-Light Ratio of Binary Galaxies

We report on the mass-to-light ratio determination based on a newly selected binary galaxy sample, which includes a large number of pairs whose separations exceed a few hundred kpc. The probability distributions of the projected separation and the velocity difference have been calculated considering the contamination of optical pairs, and the mass-to-light ratio has been determined based on the maximum likelihood method. The best estimate of $M/L$ in the B band for 57 pairs is found to be 28 $\sim$ 36 depending on the orbital parameters and the distribution of optical pairs (solar unit, $H_0=50$ km s$^{-1}$ Mpc$^{-1}$). The best estimate of $M/L$ for 30 pure spiral pairs is found to be 12 $\sim$ 16. These results are relatively smaller than those obtained in previous studies, but consistent with each other within the errors. Although the number of pairs with large separation is significantly increased compared to previous samples, $M/L$ does not show any tendency of increase, but found to be almost independent of the separation of pairs beyond 100 kpc. The constancy of $M/L$ beyond 100 kpc may indicate that the typical halo size of spiral galaxies is less than $\sim 100$ kpc.Comment: 18 pages + 8 figures, to appear in ApJ Vol. 516 (May 10

HI absorption in radio galaxies: effect of orientation or interstellar medium?

A search for HI absorption has been made in 23 radio galaxies using the ATCA, the VLA and the WSRT. In five galaxies HI absorption was detected. We investigate how the detection rate is distributed among galaxies with different radio and optical properties. Among the Fanaroff-Riley (FR) type I radio galaxies, only one object (10% of total) was detected. The HI absorption in these objects is likely to come from a nuclear disk, as found for other galaxies of this type. The low detection rate is consistent with the hypothesis (as suggested by optical and X-ray data) that the ``standard'' pc scale, geometrically thick torus is not required in low-luminosity radio galaxies. In the case of FR type-II powerful radio galaxies, no HI absorption has been detected in broad line radio galaxies, while three out of four narrow-line radio galaxies have been detected (the one non-detection having quite a high upper limit). All these are compact or small radio galaxies. To first order this is consistent with the predictions of the unified schemes, assuming that the HI absorption is due to an obscuring torus. However, the indications of this being the only cause of the absorption are not very strong. In particular, we find that in two of the three detected objects that the HI is blueshifted compared to the systemic velocity. In the third galaxy (PKS 1549-79) two redshift systems (from the optical lines) are found. The uncertainty in the systemic velocity derived from optical lines is discussed. Finally, we find a tendency for radio galaxies with a strong component of young stellar population and far-IR emission to show HI absorption. The overall richer ISM that is likely to be present in these galaxies may be a factor in producing the absorption

The disc-dominated host galaxy of FR-I radio source B2 0722+30

We present new observational results that conclude that the nearby radio galaxy B2 0722+30 is one of the very few known disc galaxies in the low-redshift Universe that host a classical double-lobed radio source. In this paper we use HI observations, deep optical imaging, stellar population synthesis modelling and emission-line diagnostics to study the host galaxy, classify the Active Galactic Nucleus and investigate environmental properties under which a radio-loud AGN can occur in this system. Typical for spiral galaxies, B2 0722+30 has a regularly rotating gaseous disc throughout which star formation occurs. Dust heating by the ongoing star formation is likely responsible for the high infrared luminosity of the system. The optical emission-line properties of the central region identify a Low Ionization Nuclear Emission-line Region (LINER)-type nucleus with a relatively low [OIII] luminosity, in particular when compared with the total power of the Fanaroff & Riley type-I radio source that is present in this system. This classifies B2 0722+30 as a classical radio galaxy rather than a typical Seyfert galaxy. The environment of B2 0722+30 is extremely HI-rich, with several nearby interacting galaxies. We argue that a gas-rich interaction involving B2 0722+30 is a likely cause for the triggering of the radio-AGN and/or the fact that the radio source managed to escape the optical boundaries of the host galaxy.Comment: To appear in MNRAS (in press); 16 pages, 11 figures. A full-resolution version of this paper is available at http://www.atnf.csiro.au/people/emo004/MNRAS_Emonts_B20722_fullres.pd