Changes in Testing and Paying for Milk Components as Proposed under the Final Rule of Federal Order Reform: Implications for Dairy Producers

Agricultural and Food Policy, Livestock Production/Industries,

Scattered Lyman-alpha Radiation Around Sources Before Cosmological Reionization

The spectra of the first galaxies and quasars in the Universe should be strongly absorbed shortward of their rest-frame Lyman-alpha wavelength by neutral hydrogen (HI) in the intervening intergalactic medium. However, the Lyman-alpha line photons emitted by these sources are not eliminated but rather scatter until they redshift out of resonance and escape due to the Hubble expansion of the surrounding intergalactic HI. We calculate the resulting brightness distribution and the spectral shape of the diffuse Lyman-alpha line emission around high redshift sources, before the intergalactic medium was reionized. Typically, the Lyman-alpha photons emitted by a source at z=10 scatter over a characteristic angular radius of order 15 arcseconds around the source and compose a line which is broadened and redshifted by about a thousand km/s relative to the source. The scattered photons are highly polarized. Detection of the diffuse Lyman-alpha halos around high redshift sources would provide a unique tool for probing the neutral intergalactic medium before the epoch of reionization. On sufficiently large scales where the Hubble flow is smooth and the gas is neutral, the Lyman-alpha brightness distribution can be used to determine the cosmological mass densities of baryons and matter.Comment: 21 pages, 5 Postscript figures, accepted by ApJ; figures 1--3 corrected; new section added on the detectability of Lyman alpha halos; conclusions update

J06587-5558 -- A Very Unusual Polarised Radio Source

We have found a peculiar radio source in the field of one of the hottest known clusters of galaxies 1E0657-56. It is slightly extended, highly polarised (54% at 8.8GHz) and has a very steep spectrum, with alpha ~ -1 at 1.3 GHz, steepening to ~ -1.5 at 8.8GHz (S \propto nu^alpha). No extragalactic sources are known with such high integrated polarisation, and sources with spectra as steep as this are rare. In this paper, we report the unusual properties of the source J06587-5558 and speculate on its origin and optical identification.Comment: 5 pages, 6 figures, accepted by MNRAS letter

Redshifted 21cm Signatures Around the Highest Redshift Quasars

The Ly-alpha absorption spectrum of the highest redshift quasars indicates that they are surrounded by giant HII regions, a few Mpc in size. The neutral gas around these HII regions should emit 21cm radiation in excess of the Cosmic Microwave Background, and enable future radio telescopes to measure the transverse extent of these HII regions. At early times, the HII regions expand with a relativistic speed. Consequently, their measured sizes along the line-of-sight (via Ly-alpha absorption) and transverse to it (via 21 cm emission) should have different observed values due to relativistic time-delay. We show that the combined measurement of these sizes would directly constrain the neutral fraction of the surrounding intergalactic medium (IGM) as well as the quasar lifetime. Based on current number counts of luminous quasars at z>6, an instrument like LOFAR should detect >2 redshifted 21cm shells per field (with a radius of 11 degrees) around active quasars as bright as those already discovered by SDSS, and >200 relic shells of inactive quasars per field. We show that Ly-alpha photons from the quasar are unable to heat the IGM or to couple the spin and kinetic temperatures of atomic hydrogen beyond the edge of the HII region. The detection of the IGM in 21cm emission around high redshift quasars would therefore gauge the presence of a cosmic Ly-alpha background during the reionization epoch.Comment: 11 pages, 6 figures. Submitted to Ap

Discovery of distant high luminosity infrared galaxies

We have developed a method for selecting the most luminous galaxies detected by IRAS based on their extreme values of R, the ratio of 60 micron and B-band luminosity. These objects have optical counterparts that are close to or below the limits of Schmidt surveys. We have tested our method on a 1079 deg^2 region of sky, where we have selected a sample of IRAS sources with 60 micron flux densities greater than 0.2 Jy, corresponding to a redshift limit z~1 for objects with far-IR luminosities of 10^{13} L_sun. Optical identifications for these were obtained from the UK Schmidt Telescope plates, using the likelihood ratio method. Optical spectroscopy has been carried out to reliably identify and measure the redshifts of six objects with very faint optical counterparts, which are the only objects with R>100 in the sample. One object is a hyperluminous infrared galaxy (HyLIG) at z=0.834. Of the remaining, fainter objects, five are ultraluminous infrared galaxies (ULIGs) with a mean redshift of 0.45, higher than the highest known redshift of any non-hyperluminous ULIG prior to this study. High excitation lines reveal the presence of an active nucleus in the HyLIG, just as in the other known infrared-selected HyLIGs. In contrast, no high excitation lines are found in the non-hyperluminous ULIGs. We discuss the implications of our results for the number density of HyLIGs at z<1 and for the evolution of the infrared galaxy population out to this redshift, and show that substantial evolution is indicated. Our selection method is robust against the presence of gravitational lensing if the optical and infrared magnification factors are similar, and we suggest a way of using it to select candidate gravitationally lensed infrared galaxies.Comment: 6 pages, accepted for publication in A&

NCR366

Sponsored by the Extension services of Illinois, Kansas, Minnesota, Missouri, South Dakota and Wisconsin, in cooperation with Extension Service, USDA, Washington, D.C.Randy D. Shaver & W. Terry Howard, Feeding dairy cows for efficient reproductive performance, University of Wisconsin-Madison, August 1998

Modifications to the Cosmic 21-cm Background Frequency Spectrum by Scattering via electrons in Galaxy Clusters

The cosmic 21-cm background frequency spectrum related to the spin-flip transition of neutral Hydrogen present during and before the era of reionization is rich in features associated with physical processes that govern transitions between the two spin states. The intervening electrons in foreground galaxy clusters inversely Compton scatter the 21-cm background spectrum and modify it just as the cosmic microwave background (CMB) spectrum is modified by inverse-Compton scattering. Towards typical galaxy clusters at low redshifts, the resulting modification is a few tenths milli-Kelvin correction to the few tens milli-Kelvin temperature of 21-cm signal relative to that of the cosmic microwave background black body spectrum. The modifications are mostly associated with sharp changes in the cosmic 21-cm background spectrum such as due to the onset of a Lyman-$\alpha$ radiation field or heating of neutral gas. Though low frequency radio interferometers that are now planned for 21-cm anisotropy measurements are insensitive to the mean 21-cm spectrum, differential observations of galaxy clusters with these interferometers can be utilized to indirectly establish global features in the 21-cm frequency spectrum. We discuss the feasibility to detect the spectrum modified by clusters and find that for upcoming interferometers, while a detection towards an individual cluster is challenging, one can average signals over a number of clusters, selected based on the strength of the Sunyave-Zel'dovich effect at high radio frequencies involving CMB scattering alone, to establish the mean 21-cm spectrum.Comment: 6 pages, 3 figures, PRD in press; expanded and title changed from v1. Final version in pres

New Constraints on the Energetics, Progenitor Mass, and Age of the Supernova Remnant G292.0+1.8 Containing PSR J1124-5916

We present spatially resolved spectroscopy of the supernova remnant (SNR) G292.0+1.8 with the Chandra X-ray observatory. This SNR contains the 135 ms pulsar, J1124-5916. We apply non-equilibrium ionization (NEI) models to the data. By comparing the derived abundances with those predicted from nucleosynthesis models, we estimate a progenitor mass of 30-40 solar masses. We also derive the intrinsic parameters of the supernova explosion such as its energy, the age of the SNR, the blast wave velocity, and the swept-up mass. In the Sedov interpretation, our estimated SNR age of 2,600 years is close to the pulsar's characteristic age of 2,900 years. This confirms the pulsar/SNR association and relaxes the need for the pulsar to have a non-canonical value for the braking index, a large period at birth or a large transverse velocity. We discuss the properties of the pulsar wind nebula (PWN) in the light of the Kennel and Coroniti model and estimate the pulsar wind magnetization parameter. We also report the first evidence for steepening of the power law spectral index with increasing radius from the pulsar.Comment: 5 pages, 3 figures. To appear in ApJL, Feb 1 2003 (submitted Oct 9 2002, accepted Dec 19 2002