Dynamical Masses in Luminous Infrared Galaxies

We have studied the dynamics and masses of a sample of ten nearby luminous and ultraluminous infrared galaxies (LIRGS and ULIRGs), using 2.3 micron CO absorption line spectroscopy and near-infrared H- and Ks-band imaging. By combining velocity dispersions derived from the spectroscopy, disk scale-lengths obtained from the imaging, and a set of likely model density profiles, we calculate dynamical masses for each LIRG. For the majority of the sample, it is difficult to reconcile our mass estimates with the large amounts of gas derived from millimeter observations and from a standard conversion between CO emission and H_2 mass. Our results imply that LIRGs do not have huge amounts of molecular gas (10^10-10^11 Msolar) at their centers, and support previous indications that the standard conversion of CO to H_2 probably overestimates the gas masses and cannot be used in these environments. This in turn suggests much more modest levels of extinction in the near-infrared for LIRGs than previously predicted (A_V~10-20 versus A_V~100-1000). The lower gas mass estimates indicated by our observations imply that the star formation efficiency in these systems is very high and is triggered by cloud-cloud collisions, shocks, and winds rather than by gravitational instabilities in circumnuclear gas disks.Comment: 14 pages, 2 figures, accepted to Ap

Forging a Cage into a Chain: Stepwise Transformation of P4_4 by Silylenes to a Si3_3P4_4 Motif

We have discovered a route to access the longest low-valent molecular silaphospha-chain, a seven-membered chain structure that incorporates three silicon and four phosphorus atoms by stepwise activation of white phosphorus (P$_4$) using two different silylene precursors. The chain species was formed via a highly reactive polyphosphide intermediate. The isolation of a stable analogue of this reaction intermediate was achieved by stepwise reaction with mono and bis(silylenes). Due to the rigidity of the ferrocenediyl framework of the bis(silylene), the isomerization process of the chain structure was hampered. Theoretical studies such as natural bond orbital and atoms in molecules analyses of the seven-membered chain species indicated some degree of delocalization of the double bond system

Controlled Waterfowl Hunting At Lake Odessa, Louisa County, Iowa

The Lake Odessa Public Hunting Area supports two systems of regulated waterfowl hunting. Control Area A consists of 55 marked blind sites which are chosen randomly by hunters during a daily drawing. Hunters using the second area, Control Area B, are not restricted to blind sites and a daily fee is not required, but all parties must possess a valid permit. Hunter use of Control Area A was uniform throughout the 1972 and 1973 hunting seasons due to the better mallard (Anas platy rhynchos) shooting on that area. Control Area B hunter use decreased as the season progressed, reflecting the early migration of wood ducks (Aix sponsa) which were more prevalent. In 1973, a year of poor mallard production but good wood duck production, hunter use of Control Area B increased over the previous year as hunters sought wood ducks. Hunters using Control Area A belonged to higher income, education, and occupation brackets, spent more money on equipment, and drove further to hunt than hunters in Control Area B. Hunter success was positively related to increasing values of vegetation parameters, but the dominant influence was not apparent. A heavy zone of annual emergent vegetation appeared to influence hunter success, but a lack of this zone could be compensated for with a strong representation of buttonbush (Cephalanthus occidentalis). Sites on medium-sized water areas (14-20 ac.) with a strong zone of annual emergent vegetation produced the highest success rates in 1972, but the same or similar sites produced low success rates in 1973 after severe loss of vegetation. Because of reduced annual emergent vegetation on the area and the receding zones of bottonbush, a summer drawdown of water level was recommended

Spitzer Observations of Cold Dust Galaxies

We combine new Spitzer Space Telescope observations in the mid- and far-infrared with SCUBA 850 micron observations to improve the measurement of dust temperatures, masses and luminosities for 11 galaxies of the SCUBA Local Universe Galaxy Survey (SLUGS). By fitting dust models we measure typical dust masses of 10E7.9 M_sol and dust luminosities of ~ 10E10 L_sol, for galaxies with modest star formation rates. The data presented in this paper combined with previous observations show that cold dust is present in all types of spiral galaxies and is a major contributor to their total luminosity. Because of the lower dust temperature of the SCUBA sources measured in this paper, they have flatter Far-IR nu F_nu(160um)/nu F_nu(850um) slopes than the larger Spitzer Nearby Galaxies Survey (SINGS), the sample that provides the best measurements of the dust properties of galaxies in the nearby universe. The new data presented here added to SINGS extend the parameter space that is well covered by local galaxies, providing a comprehensive set of templates that can be used to interpret the observations of nearby and distant galaxies.Comment: Accepted by A.J. 16 pages, 10 figures, 7 tables. High resolution version at http://mips.as.arizona.edu/~cnaw/slugs_hires.pd

Stable bidentate silylene adducts of alkaline‐earth amides

The coordination chemistry of silylenes is known for a vast number of elements of all blocks of the periodic table. However, only a handful of examples of silylene complexes have been reported for heavy alkaline-earth elements, which is mainly attributed to the “hard-soft” mismatch between the “hard” metal center and the “soft” silicon donor. Herein, we report the synthesis and characterization of a series of alkaline-earth silylene complexes comprising a bidentate pyridyl-amido-silylene ligand. The isolated Ca, Sr and Ba complexes show considerably increased stability in comparison to other known alkaline-earth silylene complexes. The molecular structures of all three complexes are essentially similar. Interestingly, depending on the central metal, the 1H NMR chemical shifts of the ortho-H atom show unexpected large differences. DFT computations were conducted to elucidate this trend in the NMR resonances

Semigroups of distributions with linear Jacobi parameters

We show that a convolution semigroup of measures has Jacobi parameters polynomial in the convolution parameter $t$ if and only if the measures come from the Meixner class. Moreover, we prove the parallel result, in a more explicit way, for the free convolution and the free Meixner class. We then construct the class of measures satisfying the same property for the two-state free convolution. This class of two-state free convolution semigroups has not been considered explicitly before. We show that it also has Meixner-type properties. Specifically, it contains the analogs of the normal, Poisson, and binomial distributions, has a Laha-Lukacs-type characterization, and is related to the $q=0$ case of quadratic harnesses.Comment: v3: the article is merged back together with arXiv:1003.4025. A significant revision following suggestions by the referee. 2 pdf figure

High Spatial Resolution Thermal-Infrared Spectroscopy with ALES: Resolved Spectra of the Benchmark Brown Dwarf Binary HD 130948BC

We present 2.9-4.1 micron integral field spectroscopy of the L4+L4 brown dwarf binary HD 130948BC, obtained with the Arizona Lenslets for Exoplanet Spectroscopy (ALES) mode of the Large Binocular Telescope Interferometer (LBTI). The HD 130948 system is a hierarchical triple system, in which the G2V primary is joined by two co-orbiting brown dwarfs. By combining the age of the system with the dynamical masses and luminosities of the substellar companions, we can test evolutionary models of cool brown dwarfs and extra-solar giant planets. Previous near-infrared studies suggest a disagreement between HD 130948BC luminosities and those derived from evolutionary models. We obtained spatially-resolved, low-resolution (R~20) L-band spectra of HD 130948B and C to extend the wavelength coverage into the thermal infrared. Jointly using JHK photometry and ALES L-band spectra for HD 130948BC, we derive atmospheric parameters that are consistent with parameters derived from evolutionary models. We leverage the consistency of these atmospheric quantities to favor a younger age (0.50 \pm 0.07 Gyr) of the system compared to the older age (0.79 \pm 0.22 Gyr) determined with gyrochronology in order to address the luminosity discrepancy.Comment: 17 pages, 9 figures, Accepted to Ap