Optical and IR luminosity functions of IRAS galaxies

The optical and infrared luminosity functions are determined for a 60 micron flux-limited sample of 68 IRAS galaxies covering a total area of 150 deg sq. The IR function is in good agreement with that obtained by other authors. The shape of the optical luminosity function is similar to that of optically selected galaxy samples. The integrated light of most objects in the sample have (NII) to H alpha line flux ratios characteristic of HII-region galaxies. In the absolute magnitude range M sub J = -18, -22 about 14% of late-type galaxies are IRAS galaxies. The apparent companionship frequency is about twice as large as that for a comparable sample of non-IRAS late-type galaxies

Demografie in de Natuurverkenning 2011

Demografische ontwikkelingen hebben invloed op natuur en landschap. Met name via ruimtebeslag door bebouwing, recreatieve consumptie en vestigingspatronen. In WOt-paper 3 wordt ingegaan op een studie die is uitgevoerd om input te leveren voor de omgevingsscenario's van de Natuurverkenning 2010-2040. Naast de lichte bevolkingsgroei die wordt voorzien, bepalen ook welvaart, samenstelling en herkomst van de bevolking het ruimtebeslag. Door de vergrijzing zal er een grotere behoefte zijn aan groen in de directe woonomgeving en aan wandel- en fietsmogelijkheden. De woonlocatie wordt steeds minder bepaald door sociale en economische motieven en steeds meer door kwaliteit van de woonomgeving. De druk op de Randstad neemt toe en wonen op het platteland nabij de stad is in trek

A Search for Low Surface Brightness Structure Around Compact Narrow Emission Line Galaxies

As the most extreme members of the rapidly evolving faint blue galaxy population at intermediate redshift, the compact narrow emission line galaxies (CNELGs) are intrinsically luminous (-22 < M_B < -18) with narrow emission linewidths (30 < \sigma < 125 km/s). Their nature is heavily debated: they may be low-mass starbursting galaxies that will fade to present-day dwarf galaxies or bursts of star formation temporarily dominating the flux of more massive galaxies, possibly related to in situ bulge formation or the formation of cores of galaxies. We present deep, high-quality (~0.6 - 0.8 arcsec) images with CFHT of 27 CNELGs. One galaxy shows clear evidence for a tidal tail; the others are not unambiguously embedded in galactic disks. Approximately 55% of the CNELGS have sizes consistent with local dwarfs of small-to-intermediate sizes, while 45% have sizes consistent with large dwarfs or disks galaxies. At least 4 CNELGs cannot harbor substantial underlying disk material; they are low-luminosity galaxies at the present epoch (M_B > -18). Conversely, 15 are not blue enough to fade to low-luminosity dwarfs (M_B > -15.2). The majority of the CNELGs are consistent with progenitors of intermediate-luminosity dwarfs and low-luminosity spiral galaxies with small disks. CNELGs are a heterogeneous progenitor population with significant fractions (up to 44%) capable of fading into today's faint dwarfs (M_B > -15.2), while 15 to 85% may only experience an apparently extremely compact CNELG phase at intermediate redshift but remain more luminous galaxies at the present epoch.Comment: 16 pages, 14 figures, emulateapj, published in Ap

Central activity in 60 micron peakers

The authors present charge coupled device (CCD) imaging results of their sample of Infrared Astronomy Satellite (IRAS) galaxies with spectral energy distributions peaking at 60 microns (Vader et al 1988). The results support the author's suggestion that the activity in 60 micron peaking galaxies is centrally concentrated, and represents an early stage of dust-embedded nuclear activity. This activity is probably triggered by a recent interaction/merger event as indicated by their peculiar optical morphologies. The authors propose that 60 micron peakers are the precursors of SO's in the case of amorphous systems, and ellipticals in the case of interacting galaxies

A Supergiant Supernova-Blown Bubble in the Spiral Galaxy NGC 1620

We present UBR and H$\alpha$ imaging of NGC 1620, a highly inclined spiral galaxy that contains a large scale, arc-like feature of radius 3 kpc in its outer disk at a distance of $\sim$ 11 kpc from the center. What is unusual about this arc-like feature is its stellar nature and the presence of a luminous star cluster at its center. The arc is fragmented into HII region complexes and OB star clusters and shows two kinks in optical continuum light. It spans an angle of 220$^{\circ}$ on our U image and a full, though fragmented, circle on an unsharp masked R image. It is centered on a young star cluster that is the most luminous clump in blue optical continuum light besides the nucleus of the galaxy. This central star cluster has UBR colors and a surface brightness similar to those of other HII regions, but is a relatively weak H$\alpha$ emitter. It consists of at least three unresolved condensations in optical continuum light. Its location at the center of the arc and its prominence within the galaxy suggests that it has been the site of several generations of supernova explosions that swept up the surrounding gas into a supershell. When it attained a radius of $0.5-1$ kpc, this shell became gravitationally unstable and formed the stars which now delineate the arc. The constraints imposed by the survival of the expanding arc against random stellar motions and the age of the stars in the arc yield a required energy input by a minimum of 400 and a maximum of 6500 supernovae. In this scenario the asymmetry in surface brightness of the arc reflects the radial gradient of the gas density in the disk of NGC 1620, while the kinks reflect inhomogeneities in the original gas distribution with respect to the central star cluster. The supernova superbubble formed at least $5 \times 10^7$ yr ago so that, unlessComment: 12 pages, AAS LaTeX, postscript file available from: ftp://ftp.cita.utoronto.ca/cita/brian/papers/n1620.ps Figures not included. Hard copy of figures available upon request to: [email protected]

Burgers en overheid samenwerkend voor landschap : Local Ownership in de praktijk

Een van de actieve vormen van lokale betrokkenheid bij landschap is Local Ownership, waarbij bewoners samen met overheden zeggenschap en verantwoordelijkheid willen delen bij het opzetten en uitvoeren van lokale initiatieven voor landschap. Hoe dit streven door burgers en overheden in de praktijk wordt gerealiseerd, is in dit LEI onderzoek uitgewerkt. Een analyse van de samenwerking tussen burgers en overheden vond plaats bij vijf cases. Het gaat daarbij om Buurtschap IJsselzone, Dorpsvisie Gelselaar, Groenprojecten Sevenum, Ommetje van Hoofdplaat en Naobers van Zuder

Radiation exposure by radio-diagnostics in Switzerland: a pilot patient-oriented survey

A patient-oriented survey was conducted in Switzerland with the aim to establishing the distribution of medical X-ray examinations among the population. A sample of 1235 people aged between 15 and 74 y (589 males and 637 females) was contacted. The participants were asked to give the number of medical X-ray examinations performed during the previous 12 months. Three-fourths of the sample did not undergo any medical X-ray examination during a 12 month-period, and 10% of the population underwent more than 1 medical X-ray examination in a year. These results were independent of the geographic region. The age distributions of the participants who did not undergo any medical X-ray examination and those who underwent one medical X-ray examination were similar. On the other hand, the age distribution of the participants who underwent more than one medical X-ray examination was characterised by a higher contribution from the elderl

Revision of the Antarctic and sub-Antarctic species of the family Stegocephalidae (Crustacea: Amphipoda) with description of two new species

The Antarctic and sub-Antarctic elements of the family Stegocephalidae DANA, 1855 (Crustacea: Amphipoda) are revised, and a key to the species is presented. Two new species are described: Andaniexis ollii n.sp. and Phippsiella watlingi n.sp. The family is represented in the Southern Ocean by 19 species belonging to 11 genera, of which one is reported as new to the area

A Broad Search for Counterrotating Gas and Stars: Evidence for Mergers and Accretion

We measure the frequency of bulk gas-stellar counterrotation in a sample of 67 galaxies drawn from the Nearby Field Galaxy Survey, a broadly representative survey of the local galaxy population down to M_B-15. We detect 4 counterrotators among 17 E/S0's with extended gas emission (24% +8 -6). In contrast, we find no clear examples of bulk counterrotation among 38 Sa-Sbc spirals, although one Sa does show peculiar gas kinematics. This result implies that, at 95% confidence, no more than 8% of Sa-Sbc spirals are bulk counterrotators. Among types Sc and later, we identify only one possible counterrotator, a Magellanic irregular. We use these results together with the physical properties of the counterrotators to constrain possible origins for this phenomenon.Comment: 19 pages, 4 figures, AJ, accepte