Evolution of the 1.4 GHz Radio Luminosity Function

The results of an optical and infrared investigation of a complete sub-sample of the Leiden-Berkeley Deep Survey (flux > 1 mJy at 1.4 GHz) are presented. Optical counterparts have been identified for 69 of the 73 sources in the two Hercules fields, and redshifts obtained for 49 of them. Photometric redshifts are computed from the g,r,i,K data for the remaining 21 sources. This complete sample is compared with the radio luminosity functions (RLFs) of Dunlop and Peacock (1990). The RLF models successfully trace the evolution of the radio sources with redshift, but there is some disagreement between the luminosity-dependence of the models and the data. The observed RLF for the lower luminosity population (log P < 26) shows evidence for a cut-off at lower redshifts (z=0.5-1.5) than for the more powerful objects.Comment: To appear in "After the Dark Ages: When Galaxies Were Young (the Universe at 2 < z < 5)", University of Maryland, October 1998, S. S. Holt and E. P. Smith (eds), (AIP), 4 pages, 4 figures, uses aipproc.sty and epsfig.st

The cosmological evolution of galaxies

The results of an extensive optical and infrared investigation of a complete sub-sample of the Leiden-Berkeley Deep Survey of radio sources at 1.4 GHz are presented. Optical coun­terparts have been identified for 69 of the 73 sources in the two Hercules fields, and redshifts obtained for 49 of them. Photometric redshifts are computed from the griK data for the remaining 20 sources.Redshifts have been measured for fifteen sources in the brighter Parkes Selected Regions radio survey, in order to test the accuracy of redshift estimates based on the K -z relation for brighter radio sources. The results enhance the evidence for a high-redshift cut-off in the2.7 GHz radio luminosity function.The data from the LBDS Hercules sample is compared with the radio luminosity func­tions (RLFs) of Dunlop and Peacock (1990). Two of the RLF models successfully trace the evolution of the radio sources with redshift, but there is some disagreement between the luminosity-dependence of the models and the data. The observed RLF for the lower lumi­nosity population (log10 P2.7 < 26) shows evidence for a cut-off at lower redshifts (z ~ 0.5-1.5) than for the more powerful objects in the Parkes Selected Regions survey.The spectral evolution of these radio sources is investigated, with particular emphasis on modelling the red envelope of galaxies. Together with a sample of passively-evolving galaxies believed to be at z ~ 2.4, these data are used to show that the oldest galaxies at high- redshift are incompatable with a critical-density (Ho = 1) universe, unless there is a significant cosmological constant

Weathering the storm: developments in the acoustic sensing of wind and rain

An Acoustic Rain Gauge (ARG) analyses the underwater sound levels across a wide frequency range, classifies the observed spectrum according to likely source and then determines the local wind speed or rain rate as appropriate. Thispaper covers a trial on the Scotian Shelf off Canada, comparing the geophysical information derived from the acoustic signals with those obtained from other sources

The spatial clustering of ultraluminous infrared galaxies over 1.5 < z < 3

We present measurements of the spatial clustering of galaxies with stellar masses 1011 M, infrared luminosities 1012 L, and star formation rates 200 M yr-1 in two redshift intervals: 1.5 &lt; z &lt; 2.0 and 2 &lt; z &lt; 3. Both samples cluster moderately strongly, with spatial correlation lengths of r0 = 6.14 B1 0.84 h-1 Mpc for the 2 &lt; z &lt; 3 sample and r0 = 5.36 B1 1.28 h-1 Mpc for the 1.5 &lt; z &lt; 2.0 sample. These clustering amplitudes are consistent with both populations residing in dark matter halos with masses of 7 C 1012 M, which is comparable to that seen for optical QSOs at the same epochs. We infer that a minimum dark matter halo mass is an important factor for all forms of luminous, obscured activity in galaxies at z &gt; 1, both starbursts and active galactic nuclei. Adopting plausible models for the growth of dark matter halos with redshift, the halos hosting the 2 &lt; z &lt; 3 sample will likely host poor to rich clusters of galaxies at z = 0, whereas the halos hosting the 1.5 &lt; z &lt; 2.0 sample will likely host L* elliptical galaxies or poor clusters at z = 0. We conclude that ultraluminous infrared galaxies (ULIRGs) at z 2.5 likely signpost stellar buildup in galaxies that will reside in clusters at z = 0 and that ULIRGs at z 1.7 signpost stellar buildup in sources that will either become L* elliptical galaxies or reside in poor clusters at z = 0

Identification of novel candidate genes for follicle selection in the broiler breeder ovary

BACKGROUND: Broiler breeders fed ad libitum are characterised by multiple ovulation, which leads to poor shell quality and egg production. Multiple ovulation is controlled by food restriction in commercial flocks. However, the level of food restriction raises welfare concerns, including that of severe hunger. Reducing the rate of multiple ovulation by genetic selection would facilitate progress towards developing a growth profile for optimum animal welfare. RESULTS: The study utilised 3 models of ovarian follicle development; laying hens fed ad libitum (experiment 2) and broiler breeders fed ad libitum or a restricted diet (experiments 1 & 3). This allowed us to investigate gene candidates for follicular development by comparing normal, abnormal and “controlled” follicle hierarchies at different stages of development. Several candidate genes for multiple ovulation were identified by combining microarray analysis of restricted vs. ad libitum feeding, literature searches and QPCR expression profiling throughout follicle development. Three candidate genes were confirmed by QPCR as showing significant differential expression between restricted and ad libitum feeding: FSHR, GDF9 and PDGFRL. PDGFRL, a candidate for steroidogenesis, showed significantly up-regulated expression in 6–8 mm follicles of ad libitum fed broiler breeders (P = 0.016), the period at which follicle recruitment occurs. CONCLUSIONS: Gene candidates have been identified and evidence provided to support a possible role in regulation of ovarian function and follicle number. Further characterisation of these genes will be required to assess their potential for inclusion into breeding programmes to improve the regulation of follicle selection and reduce the need for feed restriction