Browsing by Subject "recombination"

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Broad-Line Reverberation In The Kepler-Field Seyfert Galaxy Zw 229-015
(2011-05) Barth, Aaron J.; Nguyen, My L.; Malkan, Matthew A.; Filippenko, Alexei V.; Li, Weidong; Gorjian, Varoujan; Joner, Michael D.; Bennert, Vardha Nicola; Botyanszki, Janos; Cenko, S. Bradley; Childress, Michael; Choi, Jieun; Comerford, Julia M.; Cucciara, Antonino; da Silva, Robert; Duchene, Gaspard; Fumagalli, Michele; Ganeshalingam, Mohan; Gates, Elinor L.; Gerke, Brian F.; Griffith, Christopher V.; Harris, Chelsea; Hintz, Eric G.; Hsiao, Eric; Kandrashoff, Michael T.; Keel, William C.; Kirkman, David; Kleiser, Io K. W.; Laney, C. David; Lee, Jeffrey; Lopez, Liliana; Lowe, Thomas B.; Moody, J. Ward; Morton, Alekzandir; Nierenberg, A. M.; Nugent, Peter; Pancoast, Anna; Rex, Jacob; Rich, R. Michael; Silverman, Jeffrey M.; Smith, Graeme H.; Sonnenfeld, Alessandro; Suzuki, Nao; Tytler, David; Walsh, Jonelle L.; Woo, Jong-Hak; Yang, Yizhe; Zeisse, Carl; Comerford, Julia M.
The Seyfert 1 galaxy Zw 229-015 is among the brightest active galaxies being monitored by the Kepler mission. In order to determine the black hole mass in Zw 229-015 from H beta reverberation mapping, we have carried out nightly observations with the Kast Spectrograph at the Lick 3 m telescope during the dark runs from 2010 June through December, obtaining 54 spectroscopic observations in total. We have also obtained nightly V-band imaging with the Katzman Automatic Imaging Telescope at Lick Observatory and with the 0.9 m telescope at the Brigham Young University West Mountain Observatory over the same period. We detect strong variability in the source, which exhibited more than a factor of two change in broad H beta flux. From cross-correlation measurements, we find that the H beta light curve has a rest-frame lag of 3.86(-0.90)(+0.69) days with respect to the V-band continuum variations. We also measure reverberation lags for H alpha and H gamma and find an upper limit to the H delta lag. Combining the H beta lag measurement with a broad H beta width of sigma(line) = 1590 +/- 47 km s(-1) measured from the rms variability spectrum, we obtain a virial estimate of M-BH = 1.00(-0.24)(+0.19) x 10(7) M-circle dot for the black hole in Zw 229-015. As a Kepler target, Zw 229-015 will eventually have one of the highest-quality optical light curves ever measured for any active galaxy, and the black hole mass determined from reverberation mapping will serve as a benchmark for testing relationships between black hole mass and continuum variability characteristics in active galactic nuclei.
Effects Of Varying The Three-Body Molecular Hydrogen Formation Rate In Primordial Star Formation
(2011-01) Turk, Matthew J.; Clark, Paul; Glover, Simon C. O.; Greif, Thomas H.; Abel, Tom; Klessen, Ralf; Bromm, Volker; Bromm, Volker
The transformation of atomic hydrogen to molecular hydrogen through three-body reactions is a crucial stage in the collapse of primordial, metal-free halos, where the first generation of stars (Population III stars) in the universe is formed. However, in the published literature, the rate coefficient for this reaction is uncertain by nearly an order of magnitude. We report on the results of both adaptive mesh refinement and smoothed particle hydrodynamics simulations of the collapse of metal-free halos as a function of the value of this rate coefficient. For each simulation method, we have simulated a single halo three times, using three different values of the rate coefficient. We find that while variation between halo realizations may be greater than that caused by the three-body rate coefficient being used, both the accretion physics onto Population III protostars as well as the long-term stability of the disk and any potential fragmentation may depend strongly on this rate coefficient.
Extensive Structural Variations Between Mitochondrial Genomes of CMS and Normal Peppers (Capsicum Annuum L.) Revealed by Complete Nucleotide Sequencing
(2014-07) Jo, Yeong Deuk; Choi, Yoomi; Kim, Dong-Hwan; Kim, Byung-Dong; Kang, Byoung-Cheorl; Kim, Dong-Hwan
Cytoplasmic male sterility (CMS) is an inability to produce functional pollen that is caused by mutation of the mitochondrial genome. Comparative analyses of mitochondrial genomes of lines with and without CMS in several species have revealed structural differences between genomes, including extensive rearrangements caused by recombination. However, the mitochondrial genome structure and the DNA rearrangements that may be related to CMS have not been characterized in Capsicum spp. Results: We obtained the complete mitochondrial genome sequences of the pepper CMS line FS4401 (507,452 bp) and the fertile line Jeju (511,530 bp). Comparative analysis between mitochondrial genomes of peppers and tobacco that are included in Solanaceae revealed extensive DNA rearrangements and poor conservation in non-coding DNA. In comparison between pepper lines, FS4401 and Jeju mitochondrial DNAs contained the same complement of protein coding genes except for one additional copy of an atp6 gene (psi atp6-2) in FS4401. In terms of genome structure, we found eighteen syntenic blocks in the two mitochondrial genomes, which have been rearranged in each genome. By contrast, sequences between syntenic blocks, which were specific to each line, accounted for 30,380 and 17,847 bp in FS4401 and Jeju, respectively. The previously-reported CMS candidate genes, orf507 and psi atp6-2, were located on the edges of the largest sequence segments that were specific to FS4401. In this region, large number of small sequence segments which were absent or found on different locations in Jeju mitochondrial genome were combined together. The incorporation of repeats and overlapping of connected sequence segments by a few nucleotides implied that extensive rearrangements by homologous recombination might be involved in evolution of this region. Further analysis using mtDNA pairs from other plant species revealed common features of DNA regions around CMS-associated genes. Conclusions: Although large portion of sequence context was shared by mitochondrial genomes of CMS and male-fertile pepper lines, extensive genome rearrangements were detected. CMS candidate genes located on the edges of highly-rearranged CMS-specific DNA regions and near to repeat sequences. These characteristics were detected among CMS-associated genes in other species, implying a common mechanism might be involved in the evolution of CMS-associated genes.
Seven-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Power Spectra and WMAP-Derived Parameters
(2011-02) Larson, D.; Dunkley, J.; Hinshaw, G.; Komatsu, Eiichiro; Nolta, M. R.; Bennett, C. L.; Gold, B.; Halpern, M.; Hill, R. S.; Jarosik, N.; Kogut, A.; Limon, M.; Meyer, S. S.; Odegard, N.; Page, L.; Smith, K. M.; Spergel, D. N.; Tucker, G. S.; Weiland, J. L.; Wollack, E.; Wright, E. L.; Komatsu, Eiichiro
The WMAP mission has produced sky maps from seven years of observations at L2. We present the angular power spectra derived from the seven-year maps and discuss the cosmological conclusions that can be inferred from WMAP data alone. With the seven-year data, the temperature (TT) spectrum measurement has a signal-to-noise ratio per multipole that exceeds unity for l < 919; and in band powers of width Delta l = 10, the signal-to-noise ratio exceeds unity up to l = 1060. The third acoustic peak in the TT spectrum is now well measured by WMAP. In the context of a flat Lambda CDM model, this improvement allows us to place tighter constraints on the matter density from WMAP data alone, Omega(m)h(2) = 0.1334(-0.0055)(+0.0056), and on the epoch of matter-radiation equality, z(eq) = 3196(-133)(+134). The temperature-polarization (TE) spectrum is detected in the seven-year data with a significance of 20 sigma, compared to 13 sigma with the five-year data. We now detect the second dip in the TE spectrum near l similar to 450 with high confidence. The TB and EB spectra remain consistent with zero, thus demonstrating low systematic errors and foreground residuals in the data. The low-l EE spectrum, a measure of the optical depth due to reionization, is detected at 5.5 sigma significance when averaged over l = 2-7: l(l+ 1)C-l(EE)/(2 pi) = 0.074(-0.025)(+0.034) mu K-2 (68% CL). We now detect the high-l, 24 <= l <= 800, EE spectrum at over 8 sigma. The BB spectrum, an important probe of gravitational waves from inflation, remains consistent with zero; when averaged over l = 2-7, l(l + 1)C-l(BB)/(2 pi) < 0.055 mu K-2 (95% CL). The upper limit on tensor modes from polarization data alone is a factor of two lower with the seven-year data than it was using the five-year data. The data remain consistent with the simple Lambda CDM model: the best-fit TT spectrum has an effective chi(2) of 1227 for 1170 degrees of freedom, with a probability to exceed of 9.6%. The allowable volume in the six-dimensional space of Lambda CDM parameters has been reduced by a factor of 1.5 relative to the five-year volume, while the Lambda CDM model that allows for tensor modes and a running scalar spectral index has a factor of three lower volume when fit to the seven-year data. We test the parameter recovery process for bias and find that the scalar spectral index, n(s), is biased high, but only by 0.09 sigma, while the remaining parameters are biased by <0.15 sigma. The improvement in the third peak measurement leads to tighter lower limits from WMAP on the number of relativistic degrees of freedom (e.g., neutrinos) in the early universe: N-eff > 2.7 (95% CL). Also, using WMAP data alone, the primordial helium mass fraction is found to be Y-He = 0.28(-0.15)(+0.14), and with data from higher-resolution cosmic microwave background experiments included, we now establish the existence of pre-stellar helium at >3 sigma. These new WMAP measurements provide important tests of big bang cosmology.