12,885 research outputs found
HST-COS Observations of AGN. I. Ultraviolet Composite Spectra of the Ionizing Continuum and Emission Lines
The ionizing fluxes from quasars and other active galactic nuclei (AGN) are
critical for interpreting the emission-line spectra of AGN and for
photoionization and heating of the intergalactic medium. Using ultraviolet
spectra from the Cosmic Origins Spectrograph (COS) on the Hubble Space
Telescope (HST), we have directly measured the rest-frame ionizing continua and
emission lines for 22 AGN. Over the redshift range 0.026 < z < 1.44, COS
samples the Lyman continuum and many far-UV emission lines (Lya 1216, C IV
1549, Si IV/OIV] 1400, N V 1240, O VI 1035). Strong EUV emission lines with
14-22 eV excitation energies (Ne VIII 770,780, Ne V 569, O II 834, O III 833,
702, O IV 788,608,554, O V 630, N III 685) suggest the presence of hot gas in
the broad emission-line region. The rest-frame continuum, F_nu ~ nu^{alpha_nu},
shows a break at wavelengths below 1000 A, with spectral index alpha_nu = -0.68
+/- 0.14 in the FUV (1200-2000 A) steepening to alpha_nu = -1.41 +/- 0.21 in
the EUV (500-1000 A). The COS EUV index is similar to that of radio-quiet AGN
in the 2002 HST/FOS survey (alpha_nu = -1.57 +/- 0.17). We see no Lyman edge
(tau_HI < 0.03) or He I 584 emission in the AGN composite. Our 22 AGN exhibit a
substantial range of FUV/EUV spectral indices and a correlation with AGN
luminosity and redshift, likely due to observing below the 1000 A break.Comment: 17 pages, 10 figs, accepted to Astrophysical Journal (revised AGN
luminosities and fluxes, updated figures
The Bright Ages Survey. II. Evolution of Luminosity, Dust Extinction, and Star Formation from z = 0.5 to z = 2.5
The Bright Ages Survey is a K-band-selected redshift survey over six separate fields with UBVRIzJHK imaging covering a total of 75.6 arcmin(2) and reaching K = 20-20.5. Two fields have deep HST imaging, while all are centered on possible overdensities in the z similar to 2 range. Here we report photometric redshifts and spectroscopy for this sample, which has been described in Paper I. We find 18 galaxies with spectroscopic redshifts of z > 1:5. The derived rest-frame R-band luminosity functions show strong evolution out to z = 2. The luminosity function at z = 2 shows more bright galaxies than at any other epoch, even the extrapolated z = 3 luminosity function from Shapley et al. However, the R-band integrated luminosity density remains roughly constant from to z = 0:5 to z = 2. Evolved galaxies (E, S0, Sa) show a decreasing contribution to the total R-band luminosity density with redshift. The dust extinction in our K-selected sample is moderately larger [median z = 2 E(B - V) 0:30] than that found in Lyman break
galaxies, although not enough to make a significant impact on the total light or star formation found at high redshift. We measure the extinction-corrected star formation rate density at z 2, finding ρ_(SFR)(z = 1.5-2.5)= 0.093 M_⊙ yr^(-1) Mpc^(-3), consistent with a relatively flat instantaneous star formation rate from z = 1-4
FINANCIAL PERFORMANCE IN MEAT AND POULTRY MANUFACTURING AND WHOLESALING: AN HISTORICAL PERSPECTIVE
The financial performance of meat and poultry manufacturing and wholesaling firms is examined for the period from 1970 to 1986. Measures of liquidity, solvency, profitability, cash generation, and efficiency reported in the Robert Morris Associates Annual Statement Studies are used to examine relative performance across the different industries. The results suggest a similar performance in the wholesaling and manufacturing industries across the period in terms of liquidity. Profitability levels are similar for meat and poultry firms, although the poultry firms show a higher level of variability across the period. It appears that poultry firms leveraged themselves relatively more than did meat firms during the period. In terms of cash generation and efficiency the meat manufacturing industry performs slightly better than the other industries.Agricultural Finance,
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New Clarification About Observation Billing May Improve Care for Behavioral Health Patients
Emergency Physicians provide ongoing care to psychiatric patients beyond the confines of a standard emergency room visit. Often, when we identify patients who need specialty psychiatric care, patients board in the emergency department awaiting acceptance and transfer to an outside facility. Even in cases where it has taken multiple days to complete the transfer, it has been unclear how to properly obtain reimbursement for this care. We discuss a new coding clarification that may provide a pathway to improve part of this situation
The Spectroscopic Orbits of Five Solar Type, Single Lined Binaries
We have determined spectroscopic orbits for five single-lined spectroscopic
binaries, HD 100167, HD 135991, HD 140667, HD 158222, HD 217924. Their periods
range from 60.6 to 2403 days and the eccentricities, from 0.20 to 0.84. Our
spectral classes for the stars confirm that they are of solar type, F9 to G5,
and all are dwarfs. Their [Fe/H] abundances, determined spectroscopically, are
close to the solar value and on average are 0.12 greater than abundances from a
photometric calibration. Four of the five stars are rotating faster than their
predicted pseudosynchronous rotational velocities.Comment: 12 pages emulateap
LIVESTOCK FUTURES MARKETS AND RATIONAL PRICE FORMATION: EVIDENCE FOR LIVE CATTLE AND LIVE HOGS
The efficiency of livestock futures markets continues to receive attention, particularly with regard to their forward pricing or forecasting ability. The purpose of this paper is to present a more general theory that encompasses the forward pricing concept. It is argued that futures contract prices for competitively produced nonstorable commodities, such as live cattle and live hogs, follow a rational formation process. Futures contract prices reflect expected market conditions when contracts are sufficiently close to the delivery month that the supply of the underlying commodity cannot be changed. However, prior to the period when future supplies are relatively fixed, futures contract prices should adjust to reflect the competitive equilibrium, where output price equals average costs of production. Presented evidence suggests that live cattle and live hog futures markets support the rational price formation hypothesis: prices for distant contracts reflect average costs of feeding. Implications for risk management strategies are considered.Demand and Price Analysis, Livestock Production/Industries,
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