High resolution electronic spectroscopy of para-alkyl substituted phenols and tetramethyl cyclobutane-1,3-dione

High resolution electronic spectroscopy is demonstrated in the study of the electronic structure of para-alkyl substituted phenols (p-cresol, p-ethylphenol, p-isopropylphenol, p-propylphenol, p-sec-butylphenol, p-tert-butylphenol, and p-pentylphenol) and 2,2,4,4-tetramethyl cyclobutane-1,3-dione (TMCBD). The study on p-alkyl substituted phenols performed by laser induced fluorescence in a supersonic jet provided rich information of the electronic and vibrational structures of p-alkyl substituted phenols in the excited state as well as in the ground state. This study also provided a convenient method for the identification of conformational isomers of molecules in the excited state by observing fluorescence excitation spectra of the molecules to be studied;The study of TMCBD performed by fluorescence and low temperature polarized absorption spectroscopies provided an alternative technique for the study of electronic structures of molecules which cannot be studied in the gas phase under high resolution conditions due to the low fluorescence quantum yields or low vapor pressures of the molecules to be studied. These studies along with polarized infrared spectroscopy provided enough information about the electronic structure of TMCBD to resolve and confirm several arguments on the S[subscript]1 ([superscript]1A[subscript] u) leftharpoons S[subscript]0 ([superscript]1A[subscript] g) transition. These experiments confirm the point symmetry group change to TMCBD upon excitation to the first excited singlet state (S[subscript]1), the symmetry of progression forming modes, the observation of C-H stretching vibrations in the S[subscript]1 state, and the existence of a double minimum potential in the S[subscript]1 state. Additionally, a complete vibrational analysis in the excited state (S[subscript]1) as well as in the ground state was performed. ftn[superscript] aDOE Report IS-T 1367. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy

Improved and Quality-assessed Emission and Absorption Line measurements in Sloan Digital Sky Survey galaxies

We present a new database of absorption and emission-line measurements based on the entire spectral atlas from the Sloan Digital Sky Survey (SDSS) 7th data release of galaxies within a redshift of 0.2. Our work makes use of the publicly available penalized pixel-fitting(pPXF) and gas and absorption line fitting (gandalf) IDL codes, aiming to improve the existing measurements for stellar kinematics, the strength of various absorption-line features, and the flux and width of the emissions from different species of ionised gas. Our fit to the stellar continuum uses both standard stellar population models and empirical templates obtained by combining a large number of stellar spectra in order to fit a subsample of high-quality SDSS spectra for quiescent galaxies. Furthermore, our fit to the nebular spectrum includes an exhaustive list of both recombination and forbidden lines. Foreground Galactic extinction is implicitly treated in our models, whereas reddening in the SDSS galaxies is included in the form of a simple dust screen component affecting the entire spectrum that is accompanied by a second reddening component affecting only the ionised gas emission. In order to check for systematic departures, we provide a quality assessment for our fit to the SDSS spectra in our sample. This quality assessment also allows the identification of objects with either problematic data or peculiar features. For example, based on the quality assessment, approximately 1% of the SDSS spectra classified as "galaxies" by the SDSS pipeline do in fact require additional broad lines to be matched, even though they do not show a strong continuum from an active nucleus, as do the SDSS objects classified as "quasars". Finally, we provide new spectral templates for galaxies of different Hubble types, obtained by combining the results of our spectral fit for a subsample of 452 morphologically selected objects.Comment: Accepted for publication in ApJS. 23 pages, 14 figures, 4 tables. A version with high-resolution figures is available at http://gem.yonsei.ac.kr/~ksoh/ossy/arXiv/Oh_11_OSSY.pd

A Note on Linear Time Algorithms for Maximum Error Histograms

Histograms and Wavelet synopses provide useful tools in query optimization and approximate query answering. Traditional histogram construction algorithms, e.g., V-Optimal, use error measures which are the sums of a suitable function, e.g., square, of the error at each point. Although the best-known algorithms for solving these problems run in quadratic time, a sequence of results have given us a linear time approximation scheme for these algorithms. In recent years, there have been many emerging applications where we are interested in measuring the maximum (absolute or relative) error at a point. We show that this problem is fundamentally different from the other traditional nonl∞ error measures and provide an optimal algorithm that runs in linear time for a small number of buckets. We also present results which work for arbitrary weighted maximum error measures

Diffuse Gas in Retired Galaxies: Nebular Emission Templates and Constraints on the Sources of Ionization

We present emission line templates for passively evolving ("retired") galaxies, useful for investigation of the evolution of the ISM in these galaxies, and characterization of their high-temperature source populations. The templates are based on high signal-to-noise ($>800$) co-added spectra ($3700-6800$\AA) of $\sim11500$ gas-rich Sloan Digital Sky Survey galaxies devoid of star-formation and active galactic nuclei. Stacked spectra are provided for the entire sample and sub-samples binned by mean stellar age. In Johansson~et al (2014), these spectra provided the first measurements of the He II 4686\AA\ line in passively-evolving galaxies, and the observed He II/H$\beta$ ratio constrained the contribution of accreting white dwarfs (the "single-degenerate" scenario) to the type Ia supernova rate. In this paper, the full range of unambiguously detected emission lines are presented. Comparison of the observed [O I] 6300\AA/H$\alpha$ ratio with photoionization models further constrains any high-temperature single-degenerate scenario for type Ia supernovae (with 1.5 $\lesssim$ T/$10^{5}K$ $\lesssim$ 10) to $\lesssim$3-6\% of the observed rate in the youngest age bin (i.e. highest SN Ia rate). Hence, for the same temperatures, in the presence of an ambient population of post-AGB stars, we exclude additional high-temperature sources with a combined ionizing luminosity of $\approx 1.35\times 10^{30} L_{\odot}/M_{\odot,*}$ for stellar populations with mean ages of 1 - 4 Gyrs. Furthermore, we investigate the extinction affecting both the stellar and nebular continuum. The latter shows about five times higher values. This contradicts isotropically distributed dust and gas that renders similar extinction values for both cases.Comment: Accepted for publication in MNRAS, 16 pages, 12 figure

Special Section on the International Conference on Data Engineering 2015

The papers in this special section were presented at the 31st International Conference on Data Engineering that was held in Seoul, Korea, on April 13-17, 2015. 17, 2015