Protostellar Feedback in Turbulent Fragmentation: Consequences for Stellar Clustering and Multiplicity

Stars are strongly clustered on both large (~pc) and small (~binary) scales, but there are few analytic or even semi-analytic theories for the correlation function and multiplicity of stars. In this paper we present such a theory, based on our recently-developed semi-analytic framework called MISFIT, which models gravito-turbulent fragmentation, including the suppression of fragmentation by protostellar radiation feedback. We compare the results including feedback to a control model in which it is omitted. We show that both classes of models robustly reproduce the stellar correlation function at >0.01 pc scales, which is well approximated by a power-law that follows generally from scale-free physics (turbulence plus gravity) on large scales. On smaller scales protostellar disk fragmentation becomes dominant over common core fragmentation, leading to a steepening of the correlation function. Multiplicity is more sensitive to feedback: we found that a model with the protostellar heating reproduces the observed multiplicity fractions and mass ratio distributions for both Solar and sub-Solar mass stars (in particular the brown dwarf desert), while a model without feedback fails to do so. The model with feedback also produces an at-formation period distribution consistent with the one inferred from observations. However, it is unable to produce short-range binaries below the length scale of protostellar disks. We suggest that such close binaries are produced primarily by disk fragmentation and further decrease their separation through orbital decay.Comment: 17 pages, 15 figures, submitted to MNRA

The Trans-Pacific Partnership (TPP): In Brief

The Trans-Pacific Partnership (TPP) is a proposed free trade agreement (FTA) among 12 Asia-Pacific countries, with both economic and strategic significance for the United States. If approved, it would be the largest FTA in which the United States participates. The 12 countries announced the conclusion of the TPP negotiations on October 5, 2015, after several years of ongoing talks. The President released the text of the agreement and notified Congress of his intent to sign on November 5, 2015. Congress would need to pass implementing legislation for a final TPP agreement to enter into force for the United States. Such legislation would be eligible to receive expedited legislative consideration under the recent grant of Trade Promotion Authority (TPA), P.L. 114-26, if Congress determines the Administration has advanced the TPA negotiating objectives, and met various notification and consultation requirements. TPP negotiating parties include Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, the United States, and Vietnam. Through the TPP, the participating countries seek to liberalize trade and investment and establish new rules and disciplines in the region beyond what exists in the World Trade Organization (WTO). The FTA is envisioned as a living agreement that will be open to future members and may become a vehicle to advance a wider Asia-Pacific free trade area. It is a U.S. policy response to the rapidly increasing economic and strategic linkages among Asian-Pacific nations and has become the economic centerpiece of the Administration’s “rebalance” to the region. The TPP has slowly evolved from a more limited agreement among four countries concluded in 2006 into the current 12-country FTA agreement, with the United States joining the negotiations in 2008. Japan, the most recent country to participate, joined the negotiations in 2013. This significantly increased the potential economic significance of the agreement to the United States, because Japan is the largest economy and trading partner without an existing U.S. FTA among TPP negotiating partners (thus having greater scope for trade liberalization with the United States). The United States already has FTAs with 6 of the 11 other countries participating. Malaysia and Vietnam also stand out among the TPP countries without existing U.S. FTAs, given the rapid growth in U.S. trade with the two nations over the past three decades and substantial presence of state-owned enterprises (SOEs) that will be affected by the TPP’s SOE provisions. Views on the potential impact of the agreement vary. Proponents argue that the TPP has the opportunity to boost economic growth and jobs through expanded trade and investment opportunities with negotiating partners that currently make up 37% of total U.S. goods and services trade, involves writing new trade rules and disciplines, and deepening U.S. trade and investment integration in what many see as the world’s most economically vibrant region. The agreement would eventually eliminate all tariffs on manufactured products and most agricultural goods. It also includes new trade disciplines on issues such as digital trade barriers, state-owned enterprises (SOEs), and regulatory coherence, among other provisions. Opponents voice concerns over potential job loss and competition in import-sensitive industries, and how a TPP agreement might limit U.S. ability to regulate in areas such as health, food safety, and the environment, among other concerns. The Obama Administration, joined by many analysts as well as many policymakers in the region, has argued that the strategic value of a potential TPP agreement parallels its economic value, contending that the agreement would strengthen U.S. allies and partners and reaffirm U.S. economic leadership in the region. The President has repeatedly highlighted the importance of maintaining U.S. leadership in crafting global trade rules, notably with reference to potentially alternative Chinese initiatives. China is not a party to the TPP. Others argue that past trade pacts have had a limited impact on broad foreign policy dynamics

The Trans-Pacific Partnership (TPP): Negotiations and Issues for Congress

The Trans-Pacific Partnership (TPP) is a potential free trade agreement (FTA) among 12, and perhaps more, countries (Figure 1). The United States and 11 other countries o f the Asia-Pacific region—Australia, Brunei, Canada, Chile, Japan, Malaysia, Mexico, New Zealand, Peru, Singapore, and Vietnam—are negotiating the text of the FTA. With over 20 chapters under negotiation, the TPP partners envision the agreement to be “comprehensive and high-standard,” in that they seek to eliminate tariffs and nontariff barriers to trade in goods, services, and agriculture, and to establish or expand rules on a wide range of issues including intellectual property rights, foreign direct investment, and other trade-related issues. They also strive to create a “21st-century agreement” that addresses new and cross-cutting issues presented by an increasingly globalized economy. The TPP draws congressional interest on a number of fronts. Congress would have to approve implementing legislation for U.S. commitments under the agreement to enter into force. In addition, under long-established executive-legislative practice, the Administration notifies and consults with congressional leaders, before, during, and after trade agreements have been negotiated. Furthermore, the TPP will likely affect a range of sectors and regions of the U.S. economy of direct interest to Members of Congress and could influence the shape and path of U.S. trade policy for the foreseeable future. This report examines the issues related to the proposed TPP, the state and substance of the negotiations (to the degree that the information is publicly available), the specific areas under negotiation, the policy and economic contexts in which the TPP would fit, and the issues for Congress that the TPP presents. The report will be revised and updated as events warrant

Radiation Pressure in Massive Star Formation

Stars with masses of >~ 20 solar masses have short Kelvin times that enable them to reach the main sequence while still accreting from their natal clouds. The resulting nuclear burning produces a huge luminosity and a correspondingly large radiation pressure force on dust grains in the accreting gas. This effect may limit the upper mass of stars that can form by accretion. Indeed, simulations and analytic calculations to date have been unable to resolve the mystery of how stars of 50 solar masses and up form. We present two new ideas to solve the radiation pressure problem. First, we use three-dimensional radiation hydrodynamic adaptive mesh refinement simulations to study the collapse of massive cores. We find that in three dimensions a configuration in which radiation holds up an infalling envelope is Rayleigh-Taylor unstable, leading radiation driven bubbles to collapse and accretion to continue. We also present Monte Carlo radiative transfer calculations showing that the cavities created by protostellar winds provides a valve that allow radiation to escape the accreting envelope, further reducing the ability of radiation pressure to inhibit accretion.Comment: To be appear in "IAU 227: Massive Star Birth: A Crossroads of Astrophysics"; 6 pages, 1 figur

\u3ci\u3eAnthidium Oblongatum\u3c/i\u3e (Apoidea: Megachilidae) Confirmed as a Michigan Resident, with Notes on Other Michigan \u3ci\u3eAnthidium\u3c/i\u3e Species

The Palearctic wool-carder bee, Anthidium oblongatum (Illiger) is newly documented in Michigan, with vouchers from Kent, Washtenaw, and Wayne Counties. Additional Michigan records are provided for Anthidium manicatum (L.) and the native Anthidium psoraleae Robertson