A Refined Measurement of the Mean Transmitted Flux in the Ly-alpha Forest over 2 < z < 5 Using Composite Quasar Spectra

We present new measurements of the mean transmitted flux in the Ly-alpha forest over 2 < z < 5 made using 6065 quasar spectra from the Sloan Digital Sky Survey DR7. We exploit the general lack of evolution in the mean quasar continuum to avoid the bias introduced by continuum fitting over the Ly-alpha forest at high redshifts, which has been the primary systematic uncertainty in previous measurements of the mean Ly-alpha transmission. The individual spectra are first combined into twenty-six composites with mean redshifts spanning 2.25 < z_comp < 5.08. The flux ratios of separate composites at the same rest wavelength are then used, without continuum fitting, to infer the mean transmitted flux, F(z), as a fraction of its value at z~2. Absolute values for F(z) are found by scaling our relative values to measurements made from high-resolution data by Faucher-Giguere et al. (2008) at z < 2.5, where continuum uncertainties are minimal. We find that F(z) evolves smoothly with redshift, with no evidence of a previously reported feature at z~3.2. This trend is consistent with a gradual evolution of the ionization and thermal state of the intergalactic medium over 2 < z < 5. Our results generally agree with the most careful measurements to date made from high-resolution data, but offer much greater precision and extend to higher redshifts. This work also improves upon previous efforts using SDSS spectra by significantly reducing the level of systematic error.Comment: 14 pages, 11 figures, MNRAS, in press. Supplementary materials may be downloaded from http://www.ast.cam.ac.uk/~gdb/mean_flu

The relationship between violence in Northern Mexico and potentially avoidable hospitalizations in the USA–Mexico border region

BACKGROUND: Substantial proportions of US residents in the USA-Mexico border region cross into Mexico for health care; increases in violence in northern Mexico may have affected this access. We quantified associations between violence in Mexico and decreases in access to care for border county residents. We also examined associations between border county residence and access. METHODS: We used hospital inpatient data for Arizona, California and Texas (2005-10) to estimate associations between homicide rates and the probability of hospitalization for ambulatory care sensitive (ACS) conditions. Hospitalizations for ACS conditions were compared with homicide rates in Mexican municipalities matched by patient residence. RESULTS: A 1 SD increase in the homicide rate of the nearest Mexican municipality was associated with a 2.2 percentage point increase in the probability of being hospitalized for an ACS condition for border county patients. Residence in a border county was associated with a 1.3 percentage point decrease in the probability of being hospitalized for an ACS condition. CONCLUSIONS: Increased homicide rates in Mexico were associated with increased hospitalizations for ACS conditions in the USA, although residence in a border county was associated with decreased probability of being hospitalized for an ACS condition. Expanding access in the border region may mitigate these effects by providing alternative sources of care

Testing metallicity indicators at z~1.4 with the gravitationally lensed galaxy CASSOWARY 20

We present X-shooter observations of CASSOWARY 20 (CSWA 20), a star-forming (SFR ~6 Msol/yr) galaxy at z=1.433, magnified by a factor of 11.5 by the gravitational lensing produced by a massive foreground galaxy at z=0.741. We analysed the integrated physical properties of the HII regions of CSWA 20 using temperature- and density-sensitive emission lines. We find the abundance of oxygen to be ~1/7 of solar, while carbon is ~50 times less abundant than in the Sun. The unusually low C/O ratio may be an indication of a particularly rapid timescale of chemical enrichment. The wide wavelength coverage of X-shooter gives us access to five different methods for determining the metallicity of CSWA 20, three based on emission lines from HII regions and two on absorption features formed in the atmospheres of massive stars. All five estimates are in agreement, within the factor of ~2 uncertainty of each method. The interstellar medium of CSWA 20 only partially covers the star-forming region as viewed from our direction; in particular, absorption lines from neutrals and first ions are exceptionally weak. We find evidence for large-scale outflows of the interstellar medium (ISM) with speeds of up 750 km/s, similar to the values measured in other high-z galaxies sustaining much higher rates of star formation.Comment: 18 pages, 11 figures, accepted for publication in MNRA

Large-Scale Correlations in the Lyman-alpha Forest at z = 3-4

We present a study of the spatial coherence of the intergalactic medium toward two pairs of high-redshift quasars with moderate angular separations observed with Keck/ESI, Q1422+2309A/Q1424+2255 (z_em = 3.63, theta = 39") and Q1439-0034A/B (z_em = 4.25, theta = 33"). The crosscorrelation of transmitted flux in the Lyman-alpha forest shows a 5-7 sigma peak at zero velocity lag for both pairs. This strongly suggests that at least some of the absorbing structures span the 230-300/h_70 proper kpc transverse separation between sightlines. We also statistically examine the similarity between paired spectra as a function of transmitted flux, a measure which may be useful for comparison with numerical simulations. In investigating the dependence of the correlation functions on spectral characteristics, we find that photon noise has little impact for S/N >~ 10 per resolution element. However, the agreement between the autocorrelation along the line sight and the crosscorrelation between sightlines, a potential test of cosmological geometry, depends significantly on instrumental resolution. Finally, we present an inventory of metal lines. These include a a pair of strong C IV systems at z ~ 3.4 appearing only toward Q1439B, and a Mg II + Fe II system present toward Q1439 A and B at z = 1.68.Comment: 33 pages, 13 figures, submitted to Ap

Violation of a Leggett-Garg inequality with ideal non-invasive measurements

The quantum superposition principle states that an entity can exist in two different states simultaneously, counter to our 'classical' intuition. Is it possible to understand a given system's behaviour without such a concept? A test designed by Leggett and Garg can rule out this possibility. The test, originally intended for macroscopic objects, has been implemented in various systems. However to-date no experiment has employed the 'ideal negative result' measurements that are required for the most robust test. Here we introduce a general protocol for these special measurements using an ancillary system which acts as a local measuring device but which need not be perfectly prepared. We report an experimental realisation using spin-bearing phosphorus impurities in silicon. The results demonstrate the necessity of a non-classical picture for this class of microscopic system. Our procedure can be applied to systems of any size, whether individually controlled or in a spatial ensemble.Comment: 6+4 pages. Supplementary Methods section include

Suzaku X-ray Spectra and Pulse Profile Variations during the Superorbital Cycle of LMC X-4

We present results from spectral and temporal analyses of Suzaku and RXTE observations of the high mass X-ray binary LMC X-4. Using the full 13 years of available RXTE/ASM data, we apply the ANOVA and Lomb normalized Periodogram methods to obtain an improved superorbital period measurement of 30.32 +/- 0.04 days. The phase-averaged X-ray spectra from Suzaku observations during the high state of the superorbital period can be modeled in the 0.6--50 keV band as the combination of a power-law with Gamma ~ 0.6 and a high-energy cutoff at ~ 25 keV, a blackbody with kT_BB ~ 0.18 keV, and emission lines from Fe K_alpha, O VIII, and Ne IX (X Lyalpha). Assuming a distance of 50 kpc, The source has luminosity L_X ~ 3 x 10^38 ergs s^-1 in the 2--50 keV band, and the luminosity of the soft (blackbody) component is L_BB ~ 1.5 x 10^37 ergs s^-1. The energy resolved pulse profiles show single-peaked soft (0.5-1 keV) and hard (6-10 keV) pulses but a more complex pattern of medium (2-10 keV) pulses; cross-correlation of the hard with the soft pulses shows a phase shift that varies between observations. We interpret these results in terms of a picture in which a precessing disk reprocesses the hard X-rays and produces the observed soft spectral component, as has been suggested for the similar sources Her X-1 and SMC X-1.Comment: 13 emulateapj pages, 11 figures, 4 tables; accepted for publication in Ap

Geology for Environmental Planning in Marion County, Indiana

Marion County is the center of a large and rapidly growing urban-industrial complex in the heartland of Indiana. The boundaries of the county and of Indianapolis, the state capital, are the same as a result of the UNIGOV concept. The rapid growth of Indianapolis and its suburbs makes effective land-use planning important for Marion County. This report is designed to provide information, based on the geologic setting of the area, that can be used for effective and environmentally sound development of the county

Handling qualities of a wide-body transport airplane utilizing Pitch Active Control Systems (PACS) for relaxed static stability application

Piloted simulation studies have been conducted to evaluate the effectiveness of two pitch active control systems (PACS) on the flying qualities of a wide-body transport airplane when operating at negative static margins. These two pitch active control systems consisted of a simple 'near-term' PACS and a more complex 'advanced' PACS. Eight different flight conditions, representing the entire flight envelope, were evaluated with emphasis on the cruise flight conditions. These studies were made utilizing the Langley Visual/Motion Simulator (VMS) which has six degrees of freedom. The simulation tests indicated that (1) the flying qualities of the baseline aircraft (PACS off) for the cruise and other high-speed flight conditions were unacceptable at center-of-gravity positions aft of the neutral static stability point; (2) within the linear static stability flight envelope, the near-term PACS provided acceptable flying qualities for static stabilty margins to -3 percent; and (3) with the advanced PACS operative, the flying qualities were demonstrated to be good (satisfactory to very acceptable) for static stabilty margins to -20 percent

Radiative rotational lifetimes and state-resolved relative detachment cross sections from photodetachment thermometry of molecular anions in a cryogenic storage ring

Photodetachment thermometry on a beam of OH$^-$ in a cryogenic storage ring cooled to below 10 K is carried out using two-dimensional, frequency and time dependent photodetachment spectroscopy over 20 minutes of ion storage. In equilibrium with the low-level blackbody field, we find an effective radiative temperature near 15 K with about 90% of all ions in the rotational ground state. We measure the J = 1 natural lifetime (about 193 s) and determine the OH$^-$ rotational transition dipole moment with 1.5% uncertainty. We also measure rotationally dependent relative near-threshold photodetachment cross sections for photodetachment thermometry.Comment: Manuscript LaTeX with 5 pages, 3 figures, and 1 table plus LaTeX supplement with 12 pages, 3 figures and 3 tables. This article has been accepted by Physical Review Letter