The Baryonic Tully-Fisher Relation

We explore the Tully-Fisher relation over five decades in stellar mass in galaxies with circular velocities ranging over 30 < Vc < 300 km/s. We find a clear break in the optical Tully-Fisher relation: field galaxies with Vc < 90 km/s fall below the relation defined by brighter galaxies. These faint galaxies are however very gas rich; adding in the gas mass and plotting baryonic disk mass Md = M* + Mg in place of luminosity restores a single linear relation. The Tully-Fisher relation thus appears fundamentally to be a relation between rotation velocity and total baryonic mass of the form Md = A Vc^4.Comment: 10 pages including 1 color figure. Accepted for publication in ApJ Letter

On the Neutral Gas Content and Environment of NGC 3109 and the Antlia Dwarf Galaxy

As part of a continuing survey of nearby galaxies, we have mapped the neutral gas content of the low surface brightness, Magellanic-type galaxy NGC 3109 --- and its environment, including the Antlia dwarf galaxy --- at unprecedented velocity resolution and brightness sensitivity. The HI mass of NGC 3109 is measured to be (3.8 +/- 0.5) x 10^8 Msun. A substantial warp in the disk of NGC 3109 is detected in the HI emission image in the form of an extended low surface brightness feature. We report a positive detection in HI of the nearby Antlia dwarf galaxy, and measure its total neutral gas mass to be (6.8 +/- 1.4) x 10^5 Msun. We show the warp in NGC 3109 to lie at exactly the same radial velocity as the gas in the Antlia dwarf galaxy and speculate that Antlia disturbed the disk of NGC 3109 during a mild encounter ~1 Gyr in the past. HI data for a further eight galaxies detected in the background are presented.Comment: Accepted for publication in A

Moral dilemmas in contact-based care:The relevance of Moral Case Deliberation for forensic psychiatry

Currently, forensic psychiatry shows a shift from a control-based to a contact-based approach. Working from contact may, however, entail new moral questions and dilemmas. How to secure safety when focusing on contact? Does contact imply being physically close to the patient, or should one refrain from intimate relations? In order to help care professionals to deal with these moral issues, clinical ethics support can be useful. A specific approach in clinical ethics support is moral case deliberation (MCD). An MCD is a structured dialogue between professionals on a moral issue they experience in practice, structured by a conversation method and guided by a facilitator. In this article, we describe the background and procedures of MCD. Furthermore, we present a case example in which care professionals reflect on the moral question of whether provision of care in forensic psychiatry may entail physical closeness. The MCD shows that an open conversation results in a better understanding of different perspectives and creates the basis for finding a joint way to proceed in the case. We conclude that MCD can enable professionals to reflect on moral issues and develop shared values in forensic psychiatry

Spectroscopy of Low Surface Brightness Galaxies with the Hobby-Eberly Telescope

We have obtained low resolution spectra of nineteen red and blue low surface brightness galaxies, using the Marcario Low Resolution Spectrograph on the 9.2m Hobby-Eberly Telescope. These galaxies form a very heterogeneous class, whose spectra qualitatively resemble those of high surface brightness galaxies covering the full range of spectra seen in galaxies of Hubble types from E to Irr. We use a combination of emission line (EW(Halpha), NII/Halpha) and absorption line (Mgb, Hbeta, ) based diagnostics to investigate the star-formation and chemical enrichment histories of these galaxies. These are diverse, with some galaxies having low metallicity and very young mean stellar ages, and other galaxies showing old, super-solar metallicity stellar populations. In contrast with some previous studies which found a strong trend of decreasing metallicity with decreasing central surface brightness, we find a population of galaxies with low surface brightness and near-solar metallicity. Correlations between several of the gas phase and stellar population age and metallicity indicators are used to place contraints on plausible evolutionary scenarios for LSB galaxies. The redshift range spanned by these galaxies is broad, with radial velocities from 3400 km/s to more than 65000 km/s. A subset of the sample galaxies have published HI redshifts and gas masses based on observations with the Arecibo 305m single-dish radio telescope, which place these galaxies far off of the mean Tully-Fisher relation. Our new optical redshifts do not agree with the published HI redshifts for these galaxies. Most of the discrepancies can be explained by beam confusion in the Arecibo observations, causing erroneous HI detections for some of the galaxies.Comment: 31 pages, 12 figures, 7 tables. Uses emulateapj5.sty and onecolfloat5.sty, which are included. Accepted for publication in the Astronomical Journa

Galaxies on the Blue Edge

We have successfully constructed a catalog of HI-rich galaxies selected from the Minnesota Automated Plate Scanner Catalog of the Palomar Observatory Sky Survey (POSS I) based solely on optical criteria. We identify HI-rich candidates by selecting the bluest galaxies at a given apparent magnitude, those galaxies on the "blue edge" of POSS I color-magnitude parameter space. Subsequent 21-cm observations on the upgraded Arecibo 305m dish detected over 50% of the observed candidates. The detected galaxies are HI-rich with HI masses comparable to "normal" high surface brightness disk galaxies and they have gas mass-to-light ratios ranging from 0.1 to 4.8 (in solar units). Comparison of our candidate galaxies with known low surface brightness galaxies (hereafter LSBs) shows that they exhibit similar optical and HI properties to that population. We also show that previously identified LSBs, including several LSBs with red B-V colors, preferentially occupy the "blue edge" of POSS I color-magnitude parameter space. Their presence on the "blue edge" appears to be a selection effect due to differing plate limits in the two POSS I bandpasses. This suggests the POSS I is a good filter for separating galaxies on the higher surface brightness end of the LSB population from the general population of galaxies in the night sky.Comment: 56 pages, 19 figures, to be published in the Astronomical Journal (July 1, 2002

Evidence on continuous flow peritoneal dialysis: A review

Clinical application of continuous flow peritoneal dialysis (CFPD) has been explored since the 1960s, but despite anticipated clinical benefits, CFPD has failed to gain a foothold in clinical practice, among others due to the typical use of two catheters (or a dual-lumen catheter) and large dialysate volumes required per treatment. Novel systems applying CFPD via the existing single-lumen catheter using rapid dialysate cycling may solve one of these hurdles. Novel on-demand peritoneal dialysate generation systems and sorbent-based peritoneal dialysate regeneration systems may considerably reduce the storage space for peritoneal dialysate and/or the required dialysate volume. This review provides an overview of current evidence on CFPD in vivo. The available (pre)clinical evidence on CFPD is limited to case reports/series with inherently nonuniform study procedures, or studies with a small sample size, short follow-up, and no hard endpoints. Small solute clearance appears to be higher in CFPD compared to conventional PD, in particular at dialysate flows ≥100 mL/min using two single-lumen catheters or a double-lumen catheter. Results of CFPD using rapid cycling via a single-lumen catheter are too preliminary to draw any conclusions. Continuous addition of glucose to dialysate with CFPD appears to be effective in reducing the maximum intraperitoneal glucose concentration while increasing ultrafiltration efficiency (mL/g absorbed glucose). Patient tolerance may be an issue since abdominal discomfort and sterile peritonitis were reported with continuous circulation of the peritoneal dialysate. Thus, well-designed clinical trials of longer duration and larger sample size, in particular applying CFPD via the existing catheter, are urgently required

Star formation thresholds and galaxy edges: why and where

We study global star formation thresholds in the outer parts of galaxies by investigating the stability of disk galaxies embedded in dark halos. The disks are self-gravitating, contain metals and dust, and are exposed to UV radiation. We find that the critical surface density for the existence of a cold interstellar phase depends only weakly on the parameters of the model and coincides with the empirically derived surface density threshold for star formation. Furthermore, it is shown that the drop in the thermal velocity dispersion associated with the transition from the warm to the cold gas phase triggers gravitational instability on a wide range of scales. The presence of strong turbulence does not undermine this conclusion if the disk is self-gravitating. Models based on the hypothesis that the onset of thermal instability determines the star formation threshold in the outer parts of galaxies can reproduce many observations, including the threshold radii, column densities, and the sizes of stellar disks as a function of disk scale length and mass. Finally, prescriptions are given for implementing star formation thresholds in (semi-)analytic models and three-dimensional hydrodynamical simulations of galaxy formation.Comment: 16 pages, 6 figures, accepted for publication in the Astrophysical Journal. Version 2: text significantly revised (major improvements), physics unchanged. Version 3: minor correction

Cosmological Feedback from High-Redshift Dwarf Galaxies

We model how repeated supernova explosions in high-redshift dwarf starburst galaxies drive superbubbles and winds out of the galaxies. We compute the efficiencies of metal and mass ejection and energy transport from the galactic potentials, including the effect of cosmological infall of external gas. The starburst bubbles quickly blow out of small, high-redshift, galactic disks, but must compete with the ram pressure of the infalling gas to escape into intergalactic space. We show that the assumed efficiency of the star formation rate dominates the bubble evolution and the metal, mass, and energy feedback efficiencies. With star formation efficiency f*=0.01, the ram pressure of infall can confine the bubbles around high-redshift dwarf galaxies with circular velocities v_c>52 km/s. We can expect high metal and mass ejection efficiencies, and moderate energy transport efficiencies in halos with v_c~30-50 km/s and f*~0.01 as well as in halos with v_c~100 km/s and f*>>0.01. Such haloes collapse successively from 1-2 sigma peaks in LambdaCDM Gaussian density perturbations as time progresses. These dwarf galaxies can probably enrich low and high-density regions of intergalactic space with metals to 10^-3-10^-2 Zsun as they collapse at z~8 and z<5 respectively. They also may be able to provide adequate turbulent energy to prevent the collapse of other nearby halos, as well as to significantly broaden Lyman-alpha absorption lines to v_rms~20-40 km/s. We compute the timescales for the next starbursts if gas freely falls back after a starburst, and find that, for star formation efficiencies as low as f*<0.01, the next starburst should occur in less than half the Hubble time at the collapse redshift. This suggests that episodic star formation may be ubiquitous in dwarf galaxies.Comment: Accepted for ApJ v613, 60 pages, 15 figure

The mass surface density in the local disk and the chemical evolution of the Galaxy

We have studied the effect of adopting different values of the total baryonic mass surface density in the local disk at the present time in a model for the chemical evolution of the Galaxy. We have compared our model results with the G-dwarf metallicity distribution, the amounts of gas, stars, stellar remnants, infall rate and SN rate in the solar vicinity, and with the radial abundance gradients and gas distribution in the disk. This comparison strongly suggests that the value of the total baryonic mass surface density in the local disk which best fits the observational properties should lie in the range 50-75 Msun pc-2, and that values outside this range should be ruled out.Comment: 6 pages, LaTeX, 3 figures, accepted for publication in the Astrophysical Journal, uses emulateapj.st

Attenuation of picosecond electrical pulses by twodimensional electron gases integrated in coplanar striplines

We have measured the attenuation of picosecond electrical pulses by two-dimensional electron gases that are monolithically integrated in coplanar transmission lines. By integrating the two-dimensional electron gas structure into the transmission line, we avoid impedance mismatches that give rise to spurious reflection. The attenuated transients are simulated by an equivalent circuit transmission line model, where the conductivity of the two-dimensional electron gas underneath the transmission line is taken into account. The measured pulses are fitted with a specific conductivity of the layers corrected with a mode overlap factor, which describes the overlap of the electrical field lines with the two-dimensional layer. We obtain an overlap factor of 0.8 -1.1