HI Observations of an Ultra-Compact High-Velocity Cloud

We present HI observations of the compact high-velocity cloud HVC289+33+251 that was discovered by Putman et al. (2002). Observations with the 100-m Effelsberg telescope demonstrate that this cloud is still unresolved by the 9' beam of the Effelsberg telescope. The cloud shows a small line width of Delta v_FWHM = 4.9 km/s providing an upper limit to the kinetic temperature of the HI gas of T_k < 532 K. The total observed flux indicates an HI mass of M(HI) = 5.66 10^4 M_sun [d/150kpc]^2. Follow-up HI observations using the Australia Telescope Compact Array (ATCA) resolve HVC289+33+251 into 5 condensations that are embedded in a common HI envelope. The HVC shows a faint tail, indicating an ongoing ram-pressure interaction with an ambient low-density medium. A FWHM diameter of theta = 4.4 arcmin makes this HVC the by far most compact HVC known till now. The observed parameters suggest that pressure stabilization by an ambient medium is rather unlikely. At a distance of 150 kpc, the virial mass is by a factor of 5.6 higher than the observed gas mass -- consistent with HVC289+33+251 being one of the "missing" dark matter mini halos that were predicted by cosmological LCDM simulations (e.g. Klypin et al. 1999; Moore et al. 1999). Comparable clouds in other groups of galaxies or even around the Milky Way are not detectable with the resolution and sensitivity of present surveys.Comment: 5 pages, 3 figures, accepted for publication in A&A Letter

A Catalog of Extended Clusters and Ultra-Compact Dwarf Galaxies - An Analysis of their Parameters in Early- and Late-Type Galaxies

Extended stellar clusters with effective radii larger than 10 pc have been found in various environments. Objects with masses comparable to globular clusters (GCs) are called extended clusters (ECs), while objects with masses in the dwarf galaxy regime are called ultra-compact dwarf galaxies (UCDs). The paper analyses the observational parameters luminosity, effective radius, and projected distance to the host galaxy, of all known ECs and UCDs and the dependence of these parameters on the type and the luminosity of their host galaxy. We searched the available literature to compile a catalog of star clusters larger than 10 pc. As there is no clear distinction between ECs and UCDs, both types of objects will be called extended stellar objects (EOs). In total, we found 813 EOs of which 171 are associated with late-type and 642 with early-type galaxies. EOs cover a luminosity range from about MV = -4 to -14 mag. However, the vast majority of EOs brighter than -10 mag are associated with elliptical galaxies. At each magnitude EOs are found with effective radii between 10 pc and an upper size limit, which shows a clear trend: the more luminous the object the larger is the upper size limit. For EOs associated with early-and late-type galaxies, the luminosity functions peak at -6.40 and -6.47 mag, respectively, which is about one magnitude fainter than the peak of the GC luminosity function. EOs and GCs form a coherent structure in the reff vs. MV parameter space, while there is a clear gap between EOs and early type dwarf galaxies. However, there is a small potential overlap at the high-mass end, where the most extended EOs are close to the parameters of compact elliptical galaxies. We compare the EO sample with numerical models and conclude that the parameters of the EO sample as a whole can be very well explained by a star cluster origin, where EOs are the results of merged cluster complexes.Comment: 18 pages, 22 figures, accepted for publication in Astronomy & Astrophysic

Dynamical evolution of high velocity clouds in the intergalactic medium

HI observations of high-velocity clouds (HVCs) indicate, that they are interacting with their ambient medium. Even clouds located in the very outer Galactic halo or the intergalactic space seem to interact with their ambient medium. In this paper, we investigate the dynamical evolution of high velocity neutral gas clouds moving through a hot magnetized ambient plasma by means of two-dimensional magnetohydrodynamic plasma-neutral gas simulations. This situation is representative for the fast moving dense neutral gas cloudlets in the Magellanic Stream as well as for high velocity clouds in general. The question on the dynamical and thermal stabilization of a cold dense neutral cloud in a hot thin ambient halo plasma is numerically investigated. The simulations show the formation of a comet-like head-tail structure combined with a magnetic barrier of increased field strength which exerts a stabilizing pressure on the cloud and hinders hot plasma from diffusing into the cloud. The simulations can explain both the survival times in the intergalactic medium and the existence of head-tail high velocity clouds.Comment: 11 pages, 19 figure

Physical properties of two compact high-velocity clouds possibly associated with the Leading Arm of the Magellanic System

We observed two compact high-velocity clouds HVC 291+26+195 and HVC 297+09+253 to analyse their structure, dynamics, and physical parameters. In both cases there is evidence for an association with the Leading Arm of the Magellanic Clouds. The goal of our study is to learn more about the origin of the two CHVCs and to use them as probes for the structure and evolution of the Leading Arm. We have used the Parkes 64 m radio telescope and the Australia Telescope Compact Array (ATCA) to study the two CHVCs in the 21 cm line emission of neutral hydrogen. We present a method to estimate the distance of the two CHVCs. The investigation of the line profiles of HVC 297+09+253 reveals the presence of two line components in the spectra which can be identified with a cold and a warm gas phase. In addition, we find a distinct head-tail structure in combination with a radial velocity gradient along the tail, suggesting a ram-pressure interaction of this cloud with an ambient medium. HVC 291+26+195 has only a cold gas phase and no head-tail structure. The ATCA data show several cold, compact clumps in both clouds which, in the case of HVC 297+09+253, are embedded in the warm, diffuse envelope. All these clumps have very narrow HI lines with typical line widths between 2 and 4 km/s FWHM, yielding an upper limit for the kinetic temperature of the gas of T_max = 300 K. We obtain distance estimates for both CHVCs of the order of 10 to 60 kpc, providing additional evidence for an association of the clouds with the Leading Arm.Comment: 11 pages, 6 Postscript figures, 2 tables; accepted for publication in Astronomy & Astrophysic

Melting the Plastic Theories: Advocating the Common Law of Fraud in Credit Card Non-dischargeability Actions under 11 U.S.C. § 523(a)(2)(A)

If credit card-holders purchase items they cannot afford, they may make minimum payments and avoid default. Most people carry debt on their credit cards,\u27 and card-issuers who profit from interest on these balances encourage consumers to carry a balance. When a debtor acquires too much debt and files for bankruptcy, the debtor may generally discharge all of his debts to gain a fresh start. This discharge of debts completely bars creditors from collecting the money owed to them, and the resulting losses have frustrated the credit card industry. To prevent debts from becoming uncollectible due to discharge, credit card-issuers frequently claim fraud, alleging that a debtor used his credit card with the intention of filing for bankruptcy and discharging the debt. Card-issuers bring such claims under section 523(a)(2)(A) (the fraud exception ) of the Bankruptcy Code ( Bankruptcy Code or Code ) which excepts from discharge those debts obtained by false pretenses, false representations, or actual fraud. Upon proving that a debt is excepted from discharge, a card- issuer may collect that debt after the debtor obtains a discharge. Historically, courts have struggled when determining whether a credit card-holder committed fraud under section 523(a)(2)(A). To overcome conceptual dilemmas, courts have created different theories for analyzing credit card debt under the fraud exception. Some courts have recently discarded these credit card theories and have applied the common law of fraud to determine the dischargeability of credit card debt. The common law of fraud primarily differs from the credit card theories in that the common law requires the credit card-issuer to prove a debtor\u27s subjective intent to defraud and to show the creditor\u27s own justifiable reliance. Commentators have questioned the propriety of using the common law standard to evaluate modern credit card transactions. Additionally, the common law standard conflicts with a recent proposal to Congress by the consumer credit industry advocating an expansion of section 523(a)(2)(A) to except from discharge any debt incurred without a reasonable expectation of repayment. This proposal, precipitated by a record number of personal bankruptcies in 1996, is merely a means for consumer creditors to recover losses from bankruptcy without changing their lending practices

Deep H I observations of the compact high-velocity cloud HVC125+41-207

We present deep HI observations of the compact high-velocity cloud HVC125+41-207 using the 100-m Effelsberg telescope. Our goal was in particular to study the warm neutral medium (WNM) in detail. The Effelsberg data reveal a two phase core/halo structure - one component with a velocity width of FWHM approx 5 km/s (Westerbork data show FWHM approx 2 km/s, Braun & Burton 2000) and one with FWHM approx 18 km/s. The column density distribution of the warmer component is highly asymmetric and shows a head-tail structure. We performed a Gaussian decomposition of the cloud and found that 52% of the HI mass of the cloud is in the WNM. 24% of the WNM is located in the tail. The overall structure and the systematic variation of the observational parameters radial velocity, velocity dispersion and column density indicate that this cloud is currently interacting with the ambient medium. The Westerbork HI data of this HVC (Braun & Burton 2000) reveal an interesting dense condensation. Assuming that this condensation is virialized and in pressure equilibrium with the ambient medium, we derive a distance of 130 kpc for HVC125+41-207. Following these considerations, it is possible to constrain the parameters n_IGM 1.1 10^5 K of the intergalactic medium of the Local Group