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

Uma nova associação entre um caprelídeo e estrelas-do-mar: Caprella acanthifera s.l. (Crustacea: Amphipoda) em Ophidiaster ophidianus e Hacelia attenuata nos Açore

Uma nova associação entre um caprelídeo e estrelas-do-mar é descrita para os Açores, Atlântico nordeste. Caprella n.sp. , uma espécie do complexo Caprella acanthifera conhecida por viver sem hospedeiros no mar Mediterrâneo e no Atlântico oriental, foi encontrada em grupos, que atingiram até 77 indivíduos (em média 24), na superfície aboral das estrelas-do-mar Ophidiaster ophidianus e Hacelia attenuata na área de Monte da Guia, ilha do Faial, Açores. Não foi verificada nenhuma correlação entre o tamanho das estrelas-do-mar e o tamanho do grupo dos caprelídeos. A cor rosa dos caprelídeos sugere que eles raspam muco da superfície dos seus hospedeiros.ABSTRACT: A new caprellid-starfish association is described from the Azores, northeastern Atlantic. Caprella n.sp., a species in the Caprella acanthifera species complex known to occur free-living in the Mediterranean Sea and the eastern Atlantic Ocean, was encountered in groups of up to 77 animals (average 24) on the aboral surface of the starfish species Ophidiaster ophidianus and Hacelia attenuata at Monte da Guia, Faial Island, Azores. There was no correlation between starfish size and caprellid group size. The pinkish colour of the caprellids suggests that they scrape mucus off the surface of their starfish hosts. The known associations between caprellid amphipods and starfish are enumerated

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

Strain-induced alignment in collagen gels

Collagen is the most abundant extracellular-network-forming protein in animal biology and is important in both natural and artificial tissues, where it serves as a material of great mechanical versatility. This versatility arises from its almost unique ability to remodel under applied loads into anisotropic and inhomogeneous structures. To explore the origins of this property, we develop a set of analysis tools and a novel experimental setup that probes the mechanical response of fibrous networks in a geometry that mimics a typical deformation profile imposed by cells in vivo. We observe strong fiber alignment and densification as a function of applied strain for both uncrosslinked and crosslinked collagenous networks. This alignment is found to be irreversibly imprinted in uncrosslinked collagen networks, suggesting a simple mechanism for tissue organization at the microscale. However, crosslinked networks display similar fiber alignment and the same geometrical properties as uncrosslinked gels, but with full reversibility. Plasticity is therefore not required to align fibers. On the contrary, our data show that this effect is part of the fundamental non-linear properties of fibrous biological networks.Comment: 12 pages, 7 figures. 1 supporting material PDF with 2 figure

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

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