Investigation of a mesospheric bore event over northern China

A mesospheric bore event was observed using an OH all-sky airglow imager (ASAI) at Xinglong (40.2° N, 117.4° E), in northern China, on the night of 8–9 January 2011. Simultaneous observations by a Doppler meteor radar, a broadband sodium lidar, and TIMED/SABER OH intensity and temperature measurements are used to investigate the characteristics and environment of the bore propagation and the possible relations with the Na density perturbations. The bore propagated from northeast to southwest and divided the sky into bright and dark halves. The calculations show that the bore has an average phase velocity of 68 m s−1. The crests following the bore have a horizontal wavelength of ~ 22 km. These parameters are consistent with the hydraulic jump theory proposed by Dewan and Picard, as well as the previous bore reports. Simultaneous wind measurements from the Doppler meteor radar at Shisanling (40.3° N, 116.2° E) and temperature data from SABER on board the TIMED satellite are used to characterize the propagating environment of the bore. The result shows that a thermal-Doppler duct exists near the OH layer that supports the horizontal propagation of the bore. Simultaneous Na lidar observations at Yanqing (40.4° N, 116.0° E) suggest that there is a downward displacement of Na density during the passage of the mesospheric bore event.Q. Li, J. Xu, J. Yue, X. Liu, W. Yuan, B. Ning, S. Guan, and J. P. Younge

Unveiling the Nature of Submillimeter Galaxy SXDF850.6

We present an 880 micron Submillimeter Array (SMA) detection of the submillimeter galaxy SXDF850.6. SXDF850.6 is a bright source (S(850 micron) = 8 mJy) detected in the SCUBA Half Degree Extragalactic Survey (SHADES), and has multiple possible radio counterparts in its deep radio image obtained at the VLA. Our new SMA detection finds that the submm emission coincides with the brightest radio emission that is found ~8" north of the coordinates determined from SCUBA. Despite the lack of detectable counterparts in deep UV/optical images, we find a source at the SMA position in near-infrared and longer wavelength images. We perform SED model fits to UV-optical-IR photometry (u, B, V, R, i', z', J, H, K, 3.6 micron, 4.5 micron, 5.8 micron, and 8.0 micron) and to submm-radio photometry (850 micron, 880 micron, 1100 micron, and 21 cm) independently, and we find both are well described by starburst templates at a redshift of z ~= 2.2 (+/- 0.3). The best-fit parameters from the UV-optical-IR SED fit are a redshift of z = 1.87 (+0.15/-0.07), a stellar mass of M_star = 2.5 +2.2/-0.3 x 10^11 M_sun, an extinction of A_V = 3.0 (+0.3/-1.0) mag, and an age of 720 (+1880/-210) Myr. The submm-radio SED fit provides a consistent redshift of z ~ 1.8-2.5, an IR luminosity of L_IR = (7-26) x 10^12 L_sun, and a star formation rate of 1300-4500 M_sun/yr. These results suggest that SXDF850.6 is a mature system already having a massive amount of old stellar population constructed before its submm bright phase and is experiencing a dusty starburst, possibly induced by major mergers.Comment: 7 pages, 5 figures, Accepted for publication in Astrophysical Journa

Constraining Cosmic Evolution of Type Ia Supernovae

We present the first large-scale effort of creating composite spectra of high-redshift type Ia supernovae (SNe Ia) and comparing them to low-redshift counterparts. Through the ESSENCE project, we have obtained 107 spectra of 88 high-redshift SNe Ia with excellent light-curve information. In addition, we have obtained 397 spectra of low-redshift SNe through a multiple-decade effort at Lick and Keck Observatories, and we have used 45 UV spectra obtained by HST/IUE. The low-redshift spectra act as a control sample when comparing to the ESSENCE spectra. In all instances, the ESSENCE and Lick composite spectra appear very similar. The addition of galaxy light to the Lick composite spectra allows a nearly perfect match of the overall spectral-energy distribution with the ESSENCE composite spectra, indicating that the high-redshift SNe are more contaminated with host-galaxy light than their low-redshift counterparts. This is caused by observing objects at all redshifts with the same slit width, which corresponds to different projected distances. After correcting for the galaxy-light contamination, subtle differences in the spectra remain. We have estimated the systematic errors when using current spectral templates for K-corrections to be ~0.02 mag. The variance in the composite spectra give an estimate of the intrinsic variance in low-redshift maximum-light SN spectra of ~3% in the optical and growing toward the UV. The difference between the maximum light low and high-redshift spectra constrain SN evolution between our samples to be < 10% in the rest-frame optical.Comment: 22 pages, 22 figures, submitted to ApJ. Composite spectra can be downloaded from http://astro.berkeley.edu/~rfoley/composite

ApoC-III and visceral adipose tissue contribute to paradoxically normal triglyceride levels in insulin-resistant African-American women

Background: African-Americans are more insulin-resistant than whites but have lower triglyceride (TG) concentrations. The metabolic basis for this is unknown. Our goal was to determine in a cross-sectional study the effect of insulin resistance, visceral adipose tissue (VAT) and the apolipoproteins, B, C-III and E, on race differences in TG content of very low density lipoproteins (VLDL). Methods: The participants were 31 women (16 African-American, 15 white) of similar age (37 ± 9 vs. 38 ± 11y (mean ± SD), P = 0.72) and BMI (32.4 ± 7.2 vs. 29.3 ± 6.0 kg/m2, P = 0.21). A standard diet (33% fat, 52% carbohydrate, 15% protein) was given for 7 days followed by a test meal (40% fat, 40% carbohydrate, 20% protein) on Day 8. Insulin sensitivity index (SI) was calculated from the minimal model. VAT was measured at L2-3. The influence of race, SI, VAT and apolipoproteins on the TG content of VLDL was determined by random effects models (REM). Results: African-Americans were more insulin-resistant (SI: 3.6 ± 1.3 vs. 5.6 ± 2.6 mU/L-1.min-1, P < 0.01) with less VAT (75 ± 59 vs. 102 ± 71 cm2, P < 0.01). TG, apoB and apoC-III content of light and dense VLDL were lower in African-Americans (all P < 0.05 except for apoC-III in light VLDL, P = 0.11). ApoE content did not vary by race. In REM, VAT but not SI influenced the TG concentration of VLDL. In models with race, SI, VAT and all apolipoproteins entered, race was not significant but apoC-III and VAT remained significant determinants of TG concentration in light and dense VLDL. Conclusions: Low concentrations of apoC-III and VAT in African-Americans contribute to race differences in TG concentrations. Trial registration ClinicalTrials.gov Identifier: NCT0048486

Evolution of the Cluster Mass and Correlation Functions in LCDM Cosmology

The evolution of the cluster mass function and the cluster correlation function from z = 0 to z = 3 are determined using 10^6 clusters obtained from high-resolution simulations of the current best-fit LCDM cosmology (\Omega_m = 0.27, \sigma_8 = 0.84, h = 0.7). The results provide predictions for comparisons with future observations of high redshift clusters. A comparison of the predicted mass function of low redshift clusters with observations from early Sloan Digital Sky Survey data, and the predicted abundance of massive distant clusters with observational results, favor a slightly larger amplitude of mass fluctuations (\sigma_8 = 0.9) and lower density parameter (\Omega_m = 0.2); these values are consistent within 1-\sigma with the current observational and model uncertainties. The cluster correlation function strength increases with redshift for a given mass limit; the clusters were more strongly correlated in the past, due to their increasing bias with redshift - the bias reaches b = 100 at z = 2 for M > 5 x 10^13 h^-1 M_sun. The richness-dependent cluster correlation function, represented by the correlation scale versus cluster mean separation relation, R0-d, is generally consistent with observations. This relation can be approximated as R_0 = 1.7 d^0.6 h^-1 Mpc for d = 20 - 60 h^-1 Mpc. The R0-d relation exhibits surprisingly little evolution with redshift for z < 2; this can provide a new test of the current LCDM model when compared with future observations of high redshift clusters.Comment: 20 pages, 9 figures, accepted for publication in Ap

Approximate min-max relations on plane graphs

Let G be a plane graph, let τ(G) (resp. τ′(G)) be the minimum number of vertices (resp. edges) that meet all cycles of G, and let ν(G) (resp. ν′(G)) be the maximum number of vertex-disjoint (resp. edge-disjoint) cycles in G. In this note we show that τ(G)≤3 ν(G) and τ′(G)≤4 ν′(G)-1; our proofs are constructive, which yield polynomial-time algorithms for finding corresponding objects with the desired properties. © 2011 The Author(s).published_or_final_versionSpringer Open Choice, 28 May 201

The Effects of Domestic Violence: The Male Victims Perspective.

Domestic violence from a male victim\u27s perspective is something that is not discussed in society very much because information is very limited and incidents are often unreported. Research was done on this aspect of domestic violence to see how the types of abuse have had an impact on the victim from a physical and emotional perspective. The secondary data used for this study were from the Violence and Threats of Violence Against Women and Men in the United States, 1994-1996. Eight thousand men were selected to participate in the survey. The question of whether domestic violence is a problem was examined by race. It was determined that there was a relationship between these 2 variables with an actual significance of .000

Outer-Disk Populations in NGC 7793: Evidence for Stellar Radial Migration

We analyzed the radial surface brightness profile of the spiral galaxy NGC 7793 using HST/ACS images from the GHOSTS survey and a new HST/WFC3 image across the disk break. We used the photometry of resolved stars to select distinct populations covering a wide range of stellar ages. We found breaks in the radial profiles of all stellar populations at 280" (~5.1 kpc). Beyond this disk break, the profiles become steeper for younger populations. This same trend is seen in numerical simulations where the outer disk is formed almost entirely by radial migration. We also found that the older stars of NGC 7793 extend significantly farther than the underlying HI disk. They are thus unlikely to have formed entirely at their current radii, unless the gas disk was substantially larger in the past. These observations thus provide evidence for substantial stellar radial migration in late-type disks.Comment: 8 pages, 6 figure. Accepted for publication in Ap

Deep 1.1 mm-wavelength imaging of the GOODS-S field by AzTEC/ASTE - I. Source catalogue and number counts

[Abridged] We present the first results from a 1.1 mm confusion-limited map of the GOODS-S field taken with AzTEC on the ASTE telescope. We imaged a 270 sq. arcmin field to a 1\sigma depth of 0.48 - 0.73 mJy/beam, making this one of the deepest blank-field surveys at mm-wavelengths ever achieved. Although our GOODS-S map is extremely confused, we demonstrate that our source identification and number counts analyses are robust, and the techniques discussed in this paper are relevant for other deeply confused surveys. We find a total of 41 dusty starburst galaxies with S/N >= 3.5 within this uniformly covered region, where only two are expected to be false detections. We derive the 1.1mm number counts from this field using both a "P(d)" analysis and a semi-Bayesian technique, and find that both methods give consistent results. Our data are well-fit by a Schechter function model with (S', N(3mJy), \alpha) = (1.30+0.19 mJy, 160+27 (mJy/deg^2)^(-1), -2.0). Given the depth of this survey, we put the first tight constraints on the 1.1 mm number counts at S(1.1mm) = 0.5 mJy, and we find evidence that the faint-end of the number counts at S(850\mu m) < 2.0 mJy from various SCUBA surveys towards lensing clusters are biased high. In contrast to the 870 \mu m survey of this field with the LABOCA camera, we find no apparent under-density of sources compared to previous surveys at 1.1 mm. Additionally, we find a significant number of SMGs not identified in the LABOCA catalogue. We find that in contrast to observations at wavelengths < 500 \mu m, MIPS 24 \mu m sources do not resolve the total energy density in the cosmic infrared background at 1.1 mm, demonstrating that a population of z > 3 dust-obscured galaxies that are unaccounted for at these shorter wavelengths potentially contribute to a large fraction (~2/3) of the infrared background at 1.1 mm.Comment: 21 pages, 9 figures. Accepted to MNRAS