HALOGAS: HI Observations and Modeling of the Nearby Edge-on Spiral Galaxy NGC 4565

We present 21-cm observations and models of the neutral hydrogen in NGC 4565, a nearby, edge-on spiral galaxy, as part of the Westerbork Hydrogen Accretion in LOcal GAlaxieS (HALOGAS) survey. These models provide insight concerning both the morphology and kinematics of HI above, as well as within, the disk. NGC 4565 exhibits a distinctly warped and asymmetric disk with a flaring layer. Our modeling provides no evidence for a massive, extended HI halo. We see evidence for a bar and associated radial motions. Additionally, there are indications of radial motions within the disk, possibly associated with a ring of higher density. We see a substantial decrease in rotational velocity with height above the plane of the disk (a lag) of -40 +5/-20 km/s/kpc and -30 +5/-30 km s/kpc in the approaching and receding halves, respectively. This lag is only seen within the inner ~4.75' (14.9 kpc) on the approaching half and ~4.25' (13.4 kpc) on the receding, making this a radially shallowing lag, which is now seen in the HI layers of several galaxies. When comparing results for NGC 4565 and those for other galaxies, there are tentative indications of high star formation rate per unit area being associated with the presence of a halo. Finally, HI is found in two companion galaxies, one of which is clearly interacting with NGC 4565.Comment: 17 pages, 16 figures, accepted for publication in the Astrophysical Journal, modified affiliatio

Global modeling of secondary organic aerosol formation from aromatic hydrocarbons: high- vs low-yield pathways

Formation of SOA from the aromatic species toluene, xylene, and, for the first time, benzene, is added to a global chemical transport model. A simple mechanism is presented that accounts for competition between low and high-yield pathways of SOA formation, wherein secondary gas-phase products react further with either nitrogen oxide (NO) or hydroperoxy radical (HO2) to yield semi- or non-volatile products, respectively. Aromatic species yield more SOA when they react with OH in regions where the [NO]/[HO2] ratios are lower. The SOA yield thus depends upon the distribution of aromatic emissions, with biomass burning emissions being in areas with lower [NO]/[HO2] ratios, and the reactivity of the aromatic with respect to OH, as a lower initial reactivity allows transport away from industrial source regions, where [NO]/[HO2] ratios are higher, to more remote regions, where this ratio is lower and, hence, the ultimate yield of SOA is higher. As a result, benzene is estimated to be the most important aromatic species with regards to formation of SOA, with a total production nearly equal that of toluene and xylene combined. In total, while only 39% percent of the aromatic species react via the low-NOx pathway, 72% of the aromatic SOA is formed via this mechanism. Predicted SOA concentrations from aromatics in the Eastern United States and Eastern Europe are actually largest during the summer, when the [NO]/[HO2] ratio is lower. Global production of SOA from aromatic sources is estimated at 3.5 Tg/yr, resulting in a global burden of 0.08 Tg, twice as large as previous estimates. The contribution of these largely anthropogenic sources to global SOA is still small relative to biogenic sources, which are estimated to comprise 90% of the global SOA burden, about half of which comes from isoprene. Compared to recent observations, it would appear there are additional pathways beyond those accounted for here for production of anthropogenic SOA. However, owing to differences in spatial distributions of sources and seasons of peak production, there are still regions in which aromatic SOA produced via the mechanisms identified here are predicted to contribute substantially to, and even dominate, the local SOA concentrations, such as outflow regions from North America and South East Asia during the wintertime, though total SOA concentrations there are small (~0.1 μg/m^³)

Seeking large-scale magnetic fields in a pure-disk dwarf galaxy NGC 2976

It is still unknown how magnetic field-generation mechanisms could operate in low-mass dwarf galaxies. Here, we present a detailed study of a nearby pure-disk dwarf galaxy NGC 2976. Unlike previously observed dwarf objects, this galaxy possesses a clearly defined disk. For the purpose of our studies, we performed deep multi-frequency polarimetric observations of NGC 2976 with the VLA and Effelsberg radio telescopes. Additionally, we supplement them with re-imaged data from the WSRT-SINGS survey. The magnetic field morphology discovered in NGC 2976 consists of a southern polarized ridge. This structure does not seem to be due to just a pure large-scale dynamo process (possibly cosmic-ray driven) at work in this object, as indicated by the RM data and dynamo number calculations. Instead, the field of NGC 2976 is modified by past gravitational interactions and possibly also by ram pressure inside the M 81 galaxy group environment. The estimates of total (7 muG) and ordered (3 muG) magnetic field strengths, as well as degree of field order (0.46), which is similar to those observed in spirals, suggest that tidally generated magnetized gas flows can further enhance dynamo action in the object. NGC 2976 is apparently a good candidate for the efficient magnetization of its neighbourhood. It is able to provide an ordered (perhaps also regular) magnetic field into the intergalactic space up to a distance of about 5 kpc. Tidal interactions (and possibly also ram pressure) can lead to the formation of unusual magnetic field morphologies (like polarized ridges) in galaxies out of the star-forming disks, which do not follow any observed component of the interstellar medium (ISM), as observed in NGC 2976. These galaxies are able to provide ordered magnetic fields far out of their main disks.Comment: 16 page

The radial variation of HI velocity dispersions in dwarfs and spirals

Gas velocity dispersions provide important diagnostics of the forces counteracting gravity to prevent collapse of the gas. We use the 21 cm line of neutral atomic hydrogen (HI) to study HI velocity dispersion and HI phases as a function of galaxy morphology in 22 galaxies from The HI Nearby Galaxy Survey (THINGS). We stack individual HI velocity profiles and decompose them into broad and narrow Gaussian components. We study the HI velocity dispersion and the HI surface density, as a function of radius. For spirals, the velocity dispersions of the narrow and broad components decline with radius and their radial profiles are well described by an exponential function. For dwarfs, however, the profiles are much flatter. The single Gaussian dispersion profiles are, in general, flatter than those of the narrow and broad components. In most cases, the dispersion profiles in the outer disks do not drop as fast as the star formation profiles, derived in the literature. This indicates the importance of other energy sources in driving HI velocity dispersion in the outer disks. The radial surface density profiles of spirals and dwarfs are similar. The surface density profiles of the narrow component decline more steeply than those of the broad component, but not as steep as what was found previously for the molecular component. As a consequence, the surface density ratio between the narrow and broad components, an estimate of the mass ratio between cold HI and warm HI, tends to decrease with radius. On average, this ratio is lower in dwarfs than in spirals. This lack of a narrow, cold HI component in dwarfs may explain their low star formation activity.Comment: Accepted for publication in The Astronomical Journal, 13 pages, 10 figures, 4 table

Sex differences in plasma clozapine and norclozapine concentrations in clinical practice and in relation to body mass index and plasma glucose concentrations: a retrospective survey

Background Clozapine is widely prescribed and, although effective, can cause weight gain and dysglycemia. The dysmetabolic effects of clozapine are thought to be more prevalent in women with this gender on average attaining 17 % higher plasma clozapine concentrations than men. Methods We investigated the relationship between dose, body mass index (BMI), plasma glucose concentration, and plasma clozapine and N-desmethylclozapine (norclozapine) concentrations in 100 individuals with a severe enduring mental illness. Results Mean (10th/90th percentile) plasma clozapine concentrations were higher for women [0.49 (0.27–0.79) mg/L] compared with men [0.44 (0.26–0.70) mg/L] (F = 2.2; p = 0.035). There was no significant gender difference in the prescribed clozapine dose. BMI was significantly higher in women [mean (95 % CI) = 34.5 (26.0–45.3)] for females compared with 32.5 (25.2–41.0) for males. Overall, BMI increased by 0.7 kg/m 2 over a mean follow-up period of 210 days. A lower proportion, 41 % of women had a fasting blood glucose ≤6.0 mmol/L (<6.0 mmol/L is defined by the International Diabetes Federation as normal glucose handling), compared with 88 % of men (χ2  = 18.6, p < 0.0001). Conclusions We have shown that mean BMI and blood glucose concentrations are higher in women prescribed clozapine than in men. Women also tended to attain higher plasma clozapine concentrations than men. The higher BMI and blood glucose in women may relate to higher tissue exposure to clozapine, as a consequence of sex differences in drug metabolism

Accurate Recovery of H i Velocity Dispersion from Radio Interferometers

Gas velocity dispersion measures the amount of disordered motion of a rotating disk. Accurate estimates of this parameter are of the utmost importance because the parameter is directly linked to disk stability and star formation. A global measure of the gas velocity dispersion can be inferred from the width of the atomic hydrogen (H I) 21 cm line. We explore how several systematic effects involved in the production of H I cubes affect the estimate of H I velocity dispersion. We do so by comparing the H I velocity dispersion derived from different types of data cubes provided by The H I Nearby Galaxy Survey. We find that residual-scaled cubes best recover the H I velocity dispersion, independent of the weighting scheme used and for a large range of signal-to-noise ratio. For H I observations, where the dirty beam is substantially different from a Gaussian, the velocity dispersion values are overestimated unless the cubes are cleaned close to (e.g., ˜1.5 times) the noise level

Equation of the field lines of an axisymmetric multipole with a source surface

Optical spectropolarimeters can be used to produce maps of the surface magnetic fields of stars and hence to determine how stellar magnetic fields vary with stellar mass, rotation rate, and evolutionary stage. In particular, we now can map the surface magnetic fields of forming solar-like stars, which are still contracting under gravity and are surrounded by a disk of gas and dust. Their large scale magnetic fields are almost dipolar on some stars, and there is evidence for many higher order multipole field components on other stars. The availability of new data has renewed interest in incorporating multipolar magnetic fields into models of stellar magnetospheres. I describe the basic properties of axial multipoles of arbitrary degree ℓ and derive the equation of the field lines in spherical coordinates. The spherical magnetic field components that describe the global stellar field topology are obtained analytically assuming that currents can be neglected in the region exterior to the star, and interior to some fixed spherical equipotential surface. The field components follow from the solution of Laplace’s equation for the magnetostatic potential

Imaging Fabry-Perot Spectroscopy of NGC 5775: Kinematics of the Diffuse Ionized Gas Halo

We present imaging Fabry-Perot observations of Halpha emission in the nearly edge-on spiral galaxy NGC 5775. We have derived a rotation curve and a radial density profile along the major axis by examining position-velocity (PV) diagrams from the Fabry-Perot data cube as well as a CO 2-1 data cube from the literature. PV diagrams constructed parallel to the major axis are used to examine changes in azimuthal velocity as a function of height above the midplane. The results of this analysis reveal the presence of a vertical gradient in azimuthal velocity. The magnitude of this gradient is approximately 1 km/s/arcsec, or about 8 km/s/kpc, though a higher value of the gradient may be appropriate in localized regions of the halo. The evidence for an azimuthal velocity gradient is much stronger for the approaching half of the galaxy, although earlier slit spectra are consistent with a gradient on both sides. There is evidence for an outward radial redistribution of gas in the halo. The form of the rotation curve may also change with height, but this is not certain. We compare these results with those of an entirely ballistic model of a disk-halo flow. The model predicts a vertical gradient in azimuthal velocity which is shallower than the observed gradient, indicating that an additional mechanism is required to further slow the rotation speeds in the halo.Comment: 18 pages, 18 figures. Uses emulateapj.cls. Accepted for publication in Ap

Integral Field Unit Observations of NGC 891: Kinematics of the Diffuse Ionized Gas Halo

We present high and moderate spectral resolution spectroscopy of diffuse ionized gas (DIG) emission in the halo of NGC 891. The data were obtained with the SparsePak integral field unit at the WIYN Observatory. The wavelength coverage includes the [NII]6548,6583, Halpha, and [SII]6716,6731 emission lines. Position-velocity (PV) diagrams, constructed using spectra extracted from four SparsePak pointings in the halo, are used to examine the kinematics of the DIG. Using two independent methods, a vertical gradient in azimuthal velocity is found to be present in the northeast quadrant of the halo, with magnitude approximately 15-18 km/s/kpc, in agreement with results from HI observations. The kinematics of the DIG suggest that this gradient begins at approximately 1 kpc above the midplane. In another part of the halo, the southeast quadrant, the kinematics are markedly different, and suggest rotation at about 175 km/s, much slower than the disk but with no vertical gradient. We utilize an entirely ballistic model of disk-halo flow in an attempt to reproduce the kinematics observed in the northeast quadrant. Analysis shows that the velocity gradient predicted by the ballistic model is far too shallow. Based on intensity cuts made parallel to the major axis in the ballistic model and an Halpha image of NGC 891 from the literature, we conclude that the DIG halo is much more centrally concentrated than the model, suggesting that hydrodynamics dominate over ballistic motion in shaping the density structure of the halo. Velocity dispersion measurements along the minor axis of NGC 891 seem to indicate a lack of radial motions in the halo, but the uncertainties do not allow us to set firm limits.Comment: 31 pages, 10 figures. Accepted for publication in the Astrophysical Journa