The Initial Conditions for Gravitational Collapse of a Core: An Extremely Young Low-Mass Class 0 Protostar GF9-2

We present a study of the natal core harboring the class 0 protostar GF9-2 in the filamentary dark cloud GF 9 (d = 200 pc). GF9-2 stands unique in the sense that it shows H2O maser emission, a clear signpost of protostar formation, whereas it does not have a high-velocity large-scale molecular outflow evidenced by our deep search for CO wing emission. These facts indicate that GF9-2 core is early enough after star formation so that it still retains some information of initial conditions for collapse. Our 350 um dust continuum emission image revealed the presence of a protostellar envelope in the center of a molecular core. The mass of the envelope is ~0.6 Msun from the 350 um flux density, while LTE mass of the core is ~3 Msun from moleuclar line observations. Combining visibility data from the OVRO mm-array and the 45m telescope, we found that the core has a radial density profile of $\rho(r)\propto r^{-2}$ for 0.003 < r/pc < 0.08 region. Molecular line data analysis revealed that the velocity width of the core gas increases inward,while the outermost region maintains a velocity dispersion of a few times of the ambient sound speed. The broadened velocity width can be interpreted as infall. Thus, the collapse in GF9-2 is likely to be described by an extension of the Larson-Penston solution for the period after formation of a central star. We derived the current mass accretion rate of ~3E-05 Msun/year from infall velocity of ~ 0.3 km/s at r~ 7000 AU. All results suggest that GF9-2 core has been undergoing gravitational collapse for ~ 5000 years since the formation of central protostar(s), and that the unstable state initiated the collapse ~2E+05 years (the free-fall time) ago.Comment: ApJ Accepted. The preprint including figures with the original quality is available at http://subarutelescope.org/staff/rsf/publication.htm

A 1000 AU Scale Molecular Outflow Driven by a Protostar with an age of <4000 Years

To shed light on the early phase of a low-mass protostar formation process, we conducted interferometric observations towards a protostar GF9-2 using the CARMA and SMA. The observations have been carried out in the CO J=3-2 line and in the continuum emission at the wavelengths of 3 mm, 1 mm and 850 micron. All the continuum images detected a single point-like source with a radius of 250+/-80 AU at the center of the previously known ~3 Msun molecular cloud core. A compact emission is detected towards the object at the Spitzer MIPS and IRAC bands as well as the four bands at the WISE. Our spectroscopic imaging of the CO line revealed that the continuum source is driving a 1000 AU scale molecular outflow, including a pair of lobes where a collimated "higher" velocity red lobe exists inside a poorly collimated "lower" velocity red lobe. These lobes are rather young and the least powerful ones so far detected. A protostellar mass of M~<0.06 Msun was estimated using an upper limit of the protostellar age of (4+/-1)x10^3 yrs and an inferred non-spherical steady mass accretion rate of ~10^{-5} Msun/yr. Together with results from an SED analysis, we discuss that the outflow system is driven by a protostar whose surface temperature of~3,000K, and that the natal cloud core is being dispersed by the outflow.Comment: 27 pages, 14 figures, accepted for publication in Astrophysical Journa

Credit vs. Exemption: A Comparative Study of Double Tax Relief in the United States and Japan

The overriding issue in international taxation is the problem of double taxation. Under the tax laws of most countries, income may be taxed on the basis of either residence or source. That is, a country may tax residents of the country on worldwide income and may tax nonresidents on income from sources within the country. Thus, if a resident of one country has income from a business activity or investment in another country, the person may be taxed on the income on a residence basis by its home country and on a source basis in the other country. Most countries observe an international consensus on two points: First, relief from double taxation is essential to a healthy flow of international investment and business activity, and second, a taxpayer\u27s country of residence should assume the burden of alleviating double taxation of the taxpayer\u27s cross-border income. Under this consensus, a country may generally tax nonresidents on income from sources within the country, without regard to the possibility of double taxation, but a country should relieve double taxation for its residents. This article explores how an exemption system might work in the United States by applying both U.S. law and Japanese law, as recently amended, to three hypothetical cases. Each of the cases involves a domestic corporation (Japanese or American) with one or more subsidiaries organized, managed, and doing business in other countries

Credit vs. Exemption: A Comparative Study of Double Tax Relief in the United States and Japan

The overriding issue in international taxation is the problem of double taxation. Under the tax laws of most countries, income may be taxed on the basis of either residence or source. That is, a country may tax residents of the country on worldwide income and may tax nonresidents on income from sources within the country. Thus, if a resident of one country has income from a business activity or investment in another country, the person may be taxed on the income on a residence basis by its home country and on a source basis in the other country. Most countries observe an international consensus on two points: First, relief from double taxation is essential to a healthy flow of international investment and business activity, and second, a taxpayer\u27s country of residence should assume the burden of alleviating double taxation of the taxpayer\u27s cross-border income. Under this consensus, a country may generally tax nonresidents on income from sources within the country, without regard to the possibility of double taxation, but a country should relieve double taxation for its residents. This article explores how an exemption system might work in the United States by applying both U.S. law and Japanese law, as recently amended, to three hypothetical cases. Each of the cases involves a domestic corporation (Japanese or American) with one or more subsidiaries organized, managed, and doing business in other countries

Low-Mass Star Forming Cores in the GF9 Filament

We carried out an unbiased mapping survey of dense molecular cloud cores traced by the NH3 (1,1) and (2,2) inversion lines in the GF9 filament which contains an extremely young low-mass protostar GF9-2 (Furuya et al. 2006, ApJ, 653, 1369). The survey was conducted using the Nobeyama 45m telescope over a region of ~1.5 deg with an angular resolution of 73". The large-scale map revealed that the filament contains at least 7 dense cores, as well as 3 possible ones, located at regular intervals of ~0.9 pc. Our analysis shows that these cores have kinetic temperatures of $\lesssim$ 10 K and LTE-masses of 1.8 -- 8.2 Msun, making them typical sites of low-mass star formation. All the identified cores are likely to be gravitationally unstable because their LTE-masses are larger than their virial masses. Since the LTE-masses and separations of the cores are consistent with the Jeans masses and lengths, respectively, for the low-density ambient gas, we argue that the identified cores have formed via the gravitational fragmentation of the natal filamentary cloud.Comment: accepted by pas