Preserving Value in the Post-BAPCPA Era — An Empirical Study

Through the use of a multivariate regression model, this article studies the effect on debtor reorganization values of the shortened reorganization timeframe imposed by the Bankruptcy Abuse Prevention and Consumer Protection Act (“BAPCPA”). The study shows that BAPCPA is positively correlated at a statistically significant level with higher reorganization recoveries. This result is attributed to the increased proportion of prepackaged and prenegotiated bankruptcies observed in the post-2005 era, as these “fast-track” bankruptcy cases entail lower costs and better preserve the firm’s value

Constraining stochastic 3-D structural geological models with topology information using Approximate Bayesian Computation in GemPy 2.1

Acknowledgements. We would like to thank Total E&P UK in Aberdeen for funding this research. We also thank Fabian Stamm for providing the wonderful synthetic geomodel used in this paper. We are grateful for the constructive reviews from Ashton Krajnovich and an anonymous reviewer for helping us improve this manuscript.Peer reviewedPublisher PD

The Kinematic Evolution of Strong MgII Absorbers

We consider the evolution of strong (W_r(2796) > 0.3A) MgII absorbers, most of which are closely related to luminous galaxies. Using 20 high resolution quasar spectra from the VLT/UVES public archive, we examine 33 strong MgII absorbers in the redshift range 0.3 < z < 2.5. We compare and supplement this sample with 23 strong MgII absorbers at 0.4 < z < 1.4 observed previously with HIRES/Keck. We find that neither equivalent width nor kinematic spread (the optical depth weighted second moment of velocity) of MgII2796 evolve. However, the kinematic spread is sensitive to the highest velocity component, and therefore not as sensitive to additional weak components at intermediate velocities relative to the profile center. The fraction of absorbing pixels within the full velocity range of the system does show a trend of decreasing with decreasing redshift. Most high redshift systems (14/20) exhibit absorption over the entire system velocity range, which differs from the result for low redshift systems (18/36) at the 95% level. This leads to a smaller number of separate subsystems for high redshift systems because weak absorping components tend to connect the stronger regions of absorption. We hypothesize that low redshift MgII profiles are more likely to represent well formed galaxies, many of which have kinematics consistent with a disk/halo structure. High redshift MgII profiles are more likely to show evidence of complex protogalactic structures, with multiple accretion or outflow events. Although these results are derived from measurements of gas kinematics, they are consistent with hierarchical galaxy formation evidenced by deep galaxy surveys.Comment: Accepted to the Astrophysical Journa

Metallicity Evolution of Damped Lyman-Alpha Galaxies

We have reanalyzed the existing data on Zinc abundances in damped Ly-alpha (DLA) absorbers to investigate whether their mean metallicity evolves with time. Most models of cosmic chemical evolution predict that the mass- weighted mean interstellar metallicity of galaxies should rise with time from a low value ~ 1/30 solar at z ~ 3 to a nearly solar value at z ~ 0. However, several previous analyses have suggested that there is little or no evolution in the global metallicity of DLAs. We have used a variety of statistical techniques to quantify the global metallicity-redshift relation and its uncertainties, taking into account both measurement and sampling errors. Three new features of our analysis are: (a) an unbinned N(H I)-weighted nonlinear chi-square fit to an exponential relation; (b) survival analysis to treat the large number of limits in the existing data; and (c) a comparison of the data with several models of cosmic chemical evolution based on an unbinned N(H I)-weighted chi-square. We find that a wider range of evolutionary rates is allowed by the present data than claimed in previous studies. The slope of the exponential fit to the N(H I)-weighted mean Zn metallicity vs. redshift relation is -0.20 plus minus 0.11 counting limits as detections and -0.27 plus minus 0.12 counting limits as zeros. Similar results are also obtained if the data are binned in redshift, and if survival analysis is used. These slopes are marginally consistent with no evolution, but are also consistent with the rates predicted by several models of cosmic chemical evolution. Finally, we outline some future measurements necessary to improve the statistics of the global metallicity-redshift relation.Comment: 25 pages, 1 figure, accepted for publication in the Astrophysical Journa

A physical upper limit on the HI column density of gas clouds

An intriguing fact about cosmic gas clouds is that they all appear to have neutral (atomic) hydrogen column densities smaller than 10^{22} cm^{-2}. Observations of damped Ly-alpha (DLA) absorption systems further indicate that the maximum N(HI) decreases with increasing metallicity. It is generally assumed that this trend is due to a dust-induced selection bias: DLA systems with high N(HI) and high metallicity contain so much dust that the background QSO becomes too dim to be included in optically selected surveys. Here, it is argued that this explanation may not be viable. Instead, it is proposed that conversion to molecular hydrogen determines the maximum HI column density. Molecular hydrogen forms on the surface of dust grains and is destroyed by photodissociation. Therefore, the molecular fraction correlates with both the dust content and, because of self-shielding, the total hydrogen column density, and anticorrelates with the intensity of the incident UV radiation. It is shown that the first relation can account for the observed anticorrelation between the maximum N(HI) and metallicity.Comment: Accepted for publication in the Astrophysical Journal Letters. 4 pages, 2 figures. Minor change

Super-Solar Metallicity in Weak Mg II Absorption Systems at z ~ 1.7

Through photoionization modeling, constraints on the physical conditions of three z ~ 1.7 single-cloud weak Mg II systems (W_r(2796) < 0.3A) are derived. Constraints are provided by high resolution R = 45,000, high signal-to-noise spectra of the three quasars HE0141-3932, HE0429-4091, and HE2243-6031 which we have obtained from the ESO archive of VLT/UVES. Results are as follows: (1) The single-cloud weak Mg II absorption in the three z ~ 1.7 systems is produced by clouds with ionization parameters of -3.8 < logU < -2.0 and sizes of 1-100 pc. (2) In addition to the low-ionization phase Mg II clouds, all systems need an additional 1-3 high-ionization phase C IV clouds within 100 km/s of the Mg II component. The ionization parameters of the C IV phases range from -1.9 < logU < -1.0, with sizes of tens of parsecs to kiloparsecs. (3) Two of the three single-cloud weak Mg II absorbers have near-solar or super-solar metallicities, if we assume a solar abundance pattern. Although such large metallicities have been found for z < 1 weak Mg II absorbers, these are the first high metallicities derived for such systems at higher redshifts. (4) Two of the three weak Mg II systems also need additional low-metallicity, broad Lya absorption lines, offset in velocity from the metal-line absorption, in order to reproduce the full Lya profile. (5) Metallicity in single-cloud weak Mg II systems are more than an order of magnitude larger than those in Damped Lya systems at z ~ 1.7. In fact, there appears to be a gradual decrease in metallicity with increasing N(HI), from these, the most metal-rich Lya forest clouds, to Lyman limit systems, to sub-DLAs, and finally to the DLAs.Comment: 25 pages, 7 figures, accepted by the Astrophysical Journa

Elemental Abundances in Two High Column Density Damped Lyman Alpha Systems at z < 1.5

We present Keck/HIRES abundance measurements and metal-line kinematic profiles of the damped Lyman alpha systems (DLAs) towards the quasars Q0933+733 (z_abs=1.479) and Q0948+433 (z_abs=1.233). These two DLAs have among the five highest HI column densities at any redshift: N(HI)=4.2E21 cm^{-2}. The metal-line data, presented here for the first time, reveal that these DLAs are noteworthy for several other reasons as well. 1) The Q0933+733 DLA exhibits simple kinematic structure with unusually narrow velocity widths as measured from its unsaturated metal lines (delta v=16 km/s). At 2.6% solar, it has the second lowest metallicity at z<2. 2) The Q0948+433 DLA has among the strongest metal-line transitions of any known DLA. The saturated SiII1808 line implies a high metallicity ([Si/H]> -1) and a significant alpha-enhancement. The strong metal lines of this DLA have made possible the detection of TiII1910, CoII2012, and MgI2026. 3) We find that the relative gas-phase abundances of both DLAs follow the general trend seen at high redshift, e.g., enhanced Zn/Fe and Si/Fe, and sub-solar Mn/Fe, indicating that there is little evolution in the nucleosynthetic patterns of DLAs down to this epoch. 4) Their high HI column densities imply that these DLAs dominate the column density-weighted cosmic mean metallicity, , of the universe at z<1.5. Using the 15 DLAs with measured metallicities in the redshift interval 0.4 = -0.89^{+0.40}_{-0.33}, where the uncertainties are 95% confidence limits.Comment: 25 pages. Accepted for publication in the Astronomical Journa

Hubble Space Telescope Observations of Element Abundances in Low-redshift Damped Lyman-alpha Galaxies and Implications for the Global Metallicity-Redshift Relation

Most models of cosmic chemical evolution predict that the mass-weighted mean interstellar metallicity of galaxies should rise with time from a low value $\sim 1/30$ solar at $z \sim 3$ to a nearly solar value at $z = 0$. In the absence of any selection effects, the damped Lyman-alpha absorbers (DLAs) in quasar spectra are expected to show such a rise in global metallicity. However, it has been difficult to determine whether or not DLAs show this effect, primarily because of the very small number of DLA metallicity measurements at low redshifts. In an attempt to put tighter constraints on the low-redshift end of the DLA metallicity-redshift relation, we have observed Zn II and Cr II lines in four DLAs at $0.09 < z < 0.52$, using the Space Telescope Imaging Spectrograph (STIS) onboard the Hubble Space Telescope (HST). These observations have provided the first constraints on Zn abundances in DLAs with $z < 0.4$. In all the three DLAs for which our observations offer meaningful constraints on the metallicity, the data suggest that the metallicities are much lower than the solar value. These results are consistent with recent imaging studies indicating that these DLAs may be associated with dwarf or low surface brightness galaxies. We combine our results with higher redshift data from the literature to estimate the global mean metallicity-redshift relation for DLAs. We find that the global mean metallicity shows at most a slow increase with decreasing redshift. ...(Please see the paper for the complete abstract).Comment: 56 pages, including 13 figures. Accepted for publication in the Astrophysical Journa