Discovery of a Gas-Rich Companion to the Extremely Metal-Poor Galaxy DDO 68

We present HI spectral-line imaging of the extremely metal-poor galaxy DDO 68. This system has a nebular oxygen abundance of only 3% Z$_{\odot}$, making it one of the most metal-deficient galaxies known in the local volume. Surprisingly, DDO 68 is a relatively massive and luminous galaxy for its metal content, making it a significant outlier in the mass-metallicity and luminosity-metallicity relationships. The origin of such a low oxygen abundance in DDO 68 presents a challenge for models of the chemical evolution of galaxies. One possible solution to this problem is the infall of pristine neutral gas, potentially initiated during a gravitational interaction. Using archival HI spectral-line imaging obtained with the Karl G. Jansky Very Large Array, we have discovered a previously unknown companion of DDO 68. This low-mass (M$_{\rm HI}$ $=$ 2.8$\times$10$^{7}$ M$_{\odot}$), recently star-forming (SFR$_{\rm FUV}$ $=$ 1.4$\times$10$^{-3}$ M$_{\odot}$ yr$^{-1}$, SFR$_{\rm H\alpha}$ $<$ 7$\times$10$^{-5}$ M$_{\odot}$ yr$^{-1}$) companion has the same systemic velocity as DDO 68 (V$_{\rm sys}$ $=$ 506 km s$^{-1}$; D $=$ 12.74$\pm$0.27 Mpc) and is located at a projected distance of 42 kpc. New HI maps obtained with the 100m Robert C. Byrd Green Bank Telescope provide evidence that DDO 68 and this companion are gravitationally interacting at the present time. Low surface brightness HI gas forms a bridge between these objects.Comment: Accepted for publication in the Astrophysical Journal Letter

Hamlet Without the Prince of Denmark: Relationship Banking and Conditionality Lending in the London Market for Foreign Government Debt, 1815-1913

This paper offers a theory of conditionality lending in 19th century international capital markets. We argue that ownership of reputation signals by prestigious banks rendered them able and willing to monitor government borrowing. Monitoring was a source of rent, and it led bankers to support countries facing liquidity crises in a manner similar to modern descriptions of relationship lending to corporate clients by parent banks. Prestigious bankers' ability to implement conditionality loans and monitor countries' financial policies also enabled them to deal with solvency. We find that, compared with prestigious bankers, bondholders' committees had neither the tools nor the prestige required for effectively dealing with defaulters. Hence such committees were far less important than previous research has claimed

Cost-Effectiveness of HIV Drug Resistance Testing to Inform Switching to Second Line Antiretroviral Therapy in Low Income Settings: Supporting material

Supplementary data to support publication investigating the cost-Effectiveness of HIV Drug Resistance Testing and how it may be used to inform Antiretroviral Therapy in Low Income environment