Metallicities and dust content of proximate damped Lyman alpha systems in the Sloan Digital Sky Survey

Composite spectra of 85 proximate absorbers (log N(HI)>20 and velocity difference between the absorption and emission redshift, dv<10,000 km/s) in the SDSS are used to investigate the trends of metal line strengths with velocity separation from the QSO. We construct composites in 3 velocity bins: dv<3000 km/s, 30006000 km/s, with further sub-samples to investigate the metal line dependence on N(HI) and QSO luminosity. Low (e.g. SiII and FeII) and high ionization (e.g. SiIV and CIV) species alike have equivalent widths (EWs) that are larger by factors of 1.5 -- 3 in the dv<3000 km/s composite, compared to the dv>6000 km/s spectrum. The EWs show an even stronger dependence on dv if only the highest neutral hydrogen column density (log N(HI)>20.7) absorbers are considered. We conclude that PDLAs generally have higher metallicities than intervening absorbers, with the enhancement being a function of both dv and N(HI). It is also found that absorbers near QSOs with lower rest-frame UV luminosities have significantly stronger metal lines. We speculate that absorbers near to high luminosity QSOs may have had their star formation prematurely quenched. Finally, we search for the signature of dust reddening by the PDLAs, based on an analysis of the QSO continuum slopes relative to a control sample and determine a limit of E(B-V)<0.014 for an SMC extinction curve. This work provides an empirical motivation for distinguishing between proximate and intervening DLAs, and establishes a connection between the QSO environment and galaxy properties at high redshifts.Comment: Accepted for publication in MNRA

A new high-integrated weak field sensor for automotive applications

Especially in the field of automotive applications smart sensor systems for magnetic field sensing face increasing requirements concerning low cost, low power consumption and high magnetic performance. Over the past years AMR sensors play a decisive role in this application area because of their robustness and stability. In the following a high-integrated smart sensor system for magnetic field sensing is presented. A novel approach for the detection of weak magnetic fields is shown, which is based on an AC-excitation of AMR elements. In contrast to common used sensors this concept is based on a nonlinear AMR element without Barber pole construction. By means of this methodology sensitivity as well as temperature and life time stability is significantly improved, while the production costs compared to common-used sensors are reduced. Within this novel approach new signal conditioning algorithms and analog circuit topologies are presented, which are able to meet low offset and low noise requirements

The Discovery of Vibrationally-Excited H_2 in the Molecular Cloud near GRB 080607

GRB 080607 has provided the first strong observational signatures of molecular absorption bands toward any galaxy hosting a gamma-ray burst. Despite the identification of dozens of features as belonging to various atomic and molecular (H_2 and CO) carriers, many more absorption features remained unidentified. Here we report on a search among these features for absorption from vibrationally-excited H_2, a species that was predicted to be produced by the UV flash of a GRB impinging on a molecular cloud. Following a detailed comparison between our spectroscopy and static, as well as dynamic, models of H_2* absorption, we conclude that a column density of 10^{17.5+-0.2} cm^{-2} of H_2* was produced along the line of sight toward GRB 080607. Depending on the assumed amount of dust extinction between the molecular cloud and the GRB, the model distance between the two is found to be in the range 230--940 pc. Such a range is consistent with a conservative lower limit of 100 pc estimated from the presence of Mg I in the same data. These distances show that substantial molecular material is found within hundreds of pc from GRB 080607, part of the distribution of clouds within the GRB host galaxy.Comment: Submitted to ApJL, 6 pages emulate

Correcting CIV-Based Virial Black Hole Masses

The CIV broad emission line is visible in optical spectra to redshifts exceeding z~5. CIV has long been known to exhibit significant displacements to the blue and these `blueshifts' almost certainly signal the presence of strong outflows. As a consequence, single-epoch virial black hole (BH) mass estimates derived from CIV velocity-widths are known to be systematically biased compared to masses from the hydrogen Balmer lines. Using a large sample of 230 high-luminosity (log $L_{\rm Bol}$ = 45.5-48 erg/s), redshift 1.5<z<4.0 quasars with both CIV and Balmer line spectra, we have quantified the bias in CIV BH masses as a function of the CIV blueshift. CIV BH masses are shown to be a factor of five larger than the corresponding Balmer-line masses at CIV blueshifts of 3000 km/s and are over-estimated by almost an order of magnitude at the most extreme blueshifts, >5000 km/s. Using the monotonically increasing relationship between the CIV blueshift and the mass ratio BH(CIV)/BH(H$\alpha$) we derive an empirical correction to all CIV BH-masses. The scatter between the corrected CIV masses and the Balmer masses is 0.24 dex at low CIV blueshifts (~0 km/s) and just 0.10 dex at high blueshifts (~3000 km/s), compared to 0.40 dex before the correction. The correction depends only on the CIV line properties - i.e. full-width at half maximum and blueshift - and can therefore be applied to all quasars where CIV emission line properties have been measured, enabling the derivation of un-biased virial BH mass estimates for the majority of high-luminosity, high-redshift, spectroscopically confirmed quasars in the literature.Comment: Accepted for publication in MNRAS; fixed typo in CIV wavelengt

The missing gas problem in GRB host galaxies: evidence for a highly ionised component

There is considerable discrepancy between the amount of X-ray absorption and that inferred from optical (rest frame UV) as measured along gamma-ray burst (GRB) sight lines, with the former being typically an order of magnitude higher than what would be expected from the measurement of neutral element species via optical absorption line spectroscopy. We explore this "missing gas problem" by using X-ray and optical measurements in a sample of 29 z=0.7-6.3 GRBs from both spectroscopic data and the afterglow broadband spectral energy distributions. The low ionisation species detected in the UV are associated with the neutral interstellar medium in the GRB host galaxy, while soft X-ray absorption, which is weakly dependent on the ionisation state of the gas, provides a probe of the total column of gas along the sight line. After careful consideration of any systematic effects, we find that the neutral gas consists of less than ~10% of the total gas, and this limit decreases with the more ionised that the X-ray absorbing gas is, which in our spectral fits is assumed to be neutral. Only a very small fraction of this ionised gas, however, is detected in UV absorption lines with ionisation potentials up to ~200eV (i.e. SiIV, CIV, NV, OVI), which leaves us to postulate that the X-ray excess is due to ultra-highly-ionised, dense gas in the GRB vicinity.Comment: 10 pages, 4 figures, accepted for publication in A&

A Direct Precision Measurement of the Intergalactic Lyman-alpha Opacity at 2<z<4.2

We directly measure the evolution of the intergalactic Lya effective optical depth, tau_eff, over the redshift range 2<z<4.2 from a sample of 86 high-resolution, high-signal-to-noise quasar spectra obtained with the ESI and HIRES spectrographs on Keck, and with the MIKE spectrograph on Magellan. This represents an improvement over previous analyses of the Lya forest from high-resolution spectra in this redshift interval of a factor of two in the size of the data set alone. We pay particular attention to robust error estimation and extensively test for systematic effects. We find that our estimates of the quasar continuum levels in the Lya forest obtained by spline fitting are systematically biased low, with the magnitude of the bias increasing with redshift, but that this bias can be accounted for using mock spectra. The mean fractional error is <1% at z=2, 4% at z=3, and 12% at z=4. Previous measurements of tau_eff at z>~3 based on directly fitting the quasar continua in the Lya forest, which have generally neglected this effect, are therefore likely biased low. We provide estimates of the level of absorption arising from metals in the Lya forest based on both direct and statistical metal removal results in the literature, finding that this contribution is ~6-9% at z=3 and decreases monotonically with redshift. The high precision of our measurement, attaining 3% in redshift bins of width Delta z=0.2 around z=3, indicates significant departures from the best-fit power-law redshift evolution (tau_eff=0.0018(1+z)^3.92, when metals are left in), particularly near z=3.2. The observed downward departure is statistically consistent with a similar feature detected in a precision statistical measurement using Sloan Digital Sky Survey spectra by Bernardi and coworkers using an independent approach.Comment: 27 pages, including 18 figures, published in Ap

The kinetic temperature in a damped Lyman-alpha absorption system in Q2206-199 - an example of the warm neutral medium

By comparing the widths of absorption lines from OI, SiII and FeII in the redshift z=2.076 single-component damped Lyman alpha absorption system in the spectrum of Q2206-199 we establish that these absorption lines arise in Warm Neutral Medium gas at ~12000 +/- 3000K. This is consistent with thermal equilibrium model estimates of ~ 8000K for the Warm Neutral Medium in galaxies, but not with the presence of a significant cold component. It is also consistent with, but not required by, the absence of CII* fine structure absorption in this system. Some possible implications concerning abundance estimates in narrow-line WNM absorbers are discussed.Comment: 9 pages, 3 figures. MNRAS accepte

What makes a mobile app successful in supporting health behaviour change?

YesIntroduction: Health promotion apps designed to support and reinforce health behaviours or to reduce risk behaviours are the most commonly downloaded apps. Such technologies have the potential to reach and deliver health care to new populations. But the extent to which they are successful in enabling the adoption of new and desired behaviours can vary. Some apps are more effective than others, some are free to download while others require a nominal or substantial charge. Cost alone is not indicative of quality or effectiveness. This is important because the use of health apps by the public will likely increase, as is the expectation that health care professionals understand this technology and its heuristic role in personalised health. Practitioners therefore need to be better informed regarding what makes a health app appealing to service users and successful as an intervention to facilitate behaviour change. Objective: This paper describes and discusses how the structure and content of health care apps can facilitate or inhibit behavioural change. The aim is to support practitioners in the screening and identification of suitable apps for clinical use. Method: Theory and literature review. Conclusion: App content that involved clinician input at the design stage and included internal drivers such as motivation, self-efficacy and illness understanding and external drivers such as illness information, social networking and user compatibility tend to do better in facilitating behaviour change than those that do not. Of these factors, motivation is considered to be the most important