The unusual distribution of molecular gas and star formation in Arp 140

We investigate the atomic and molecular interstellar medium and star formation of NGC 275, the late-type spiral galaxy in Arp 140, which is interacting with NGC 274, an early-type system. The atomic gas (HI) observations reveal a tidal tail from NGC 275 which extends many optical radii beyond the interacting pair. The HI morphology implies a prograde encounter between the galaxy pair approximately 1.5 x 10**8 years ago. The Halpha emission from NGC 275 indicates clumpy irregular star-formation, clumpiness which is mirrored by the underlying mass distribution as traced by the Ks-band emission. The molecular gas distribution is striking in its anti-correlation with the {HII regions. Despite the evolved nature of NGC 275's interaction and its barred potential, neither the molecular gas nor the star formation are centrally concentrated. We suggest that this structure results from stochastic star formation leading to preferential consumption of the gas in certain regions of the galaxy. In contrast to the often assumed picture of interacting galaxies, NGC 275, which appears to be close to merger, does not display enhanced or centrally concentrated star formation. If the eventual merger is to lead to a significant burst of star formation it must be preceded by a significant conversion of atomic to molecular gas as at the current rate of star formation all the molecular gas will be exhausted by the time the merger is complete.Comment: 13 paper, accepted my Monthly Notices of the Royal Astronomical Societ

The costs of single species programes and the budget constraint

Despite the scarcity of funding for species conservation programs, estimation of the cost of threatened species programs occurs in only a few countries. This paper examines the reasons for the lack of species program cost estimates and the likely impacts of this on conservation management. We report methodology used to estimate cost for eleven New Zealand species programs and their estimated costs over a ten year period. Differences between species in the costs of the programs and the breakdown of the costs are highlighted. The estimated costs are compared with expected levels of expenditure on each species to illustrate the existence of a budget constraint for threatened species. The likely effects of cost of species conservation exceeding expenditures on species conservation are examined. Annual cost data is used together with information on rate of conservation progress to estimate time and total cost for each species to reach ‘Not Threatened’ status

Solutions of the fully compressible semi-geostrophic system

The fully compressible semi-geostrophic system is widely used in the modelling of large-scale atmospheric flows. In this paper, we prove rigorously the existence of weak Lagrangian solutions of this system, formulated in the original physical coordinates. In addition, we provide an alternative proof of the earlier result on the existence of weak solutions of this system expressed in the so-called geostrophic, or dual, coordinates. The proofs are based on the optimal transport formulation of the problem and on recent general results concerning transport problems posed in the Wasserstein space of probability measures

NLO corrections to h → bb¯ decay in SMEFT

We calculate the full set of next-to-leading order (NLO) corrections to h → b b¯¯ decay in the dimension-6 Standard Model Effective Field Theory (SMEFT). Our calculation forms the basis for precision studies of this decay mode in effective field theory, providing analytic and numerical results for contributions of the 45 dimension-6 operators appearing at NLO. On the technical side, we discuss several complications in NLO SMEFT computations which have not yet been addressed in the literature. These include subtleties in Higgs-Z mixing, electric charge renormalization, and especially the treatment of tadpoles in SMEFT. In particular, we highlight the role of decoupling relations in eliminating potentially large tadpole corrections to the decay rate in hybrid renormalization schemes which employ the MS¯¯¯¯¯¯¯ scheme for some Standard Model parameters (such as the b-quark mass and electric charge) and the on-shell scheme for others

Sampling Time Effects for Persistence and Survival in Step Structural Fluctuations

The effects of sampling rate and total measurement time have been determined for single-point measurements of step fluctuations within the context of first-passage properties. Time dependent STM has been used to evaluate step fluctuations on Ag(111) films grown on mica as a function of temperature (300-410 K), on screw dislocations on the facets of Pb crystallites at 320K, and on Al-terminated Si(111) over the temperature range 770K - 970K. Although the fundamental time constant for step fluctuations on Ag and Al/Si varies by orders of magnitude over the temperature ranges of measurement, no dependence of the persistence amplitude on temperature is observed. Instead, the persistence probability is found to scale directly with t/Dt where Dt is the time interval used for sampling. Survival probabilities show a more complex scaling dependence which includes both the sampling interval and the total measurement time tm. Scaling with t/Dt occurs only when Dt/tm is a constant. We show that this observation is equivalent to theoretical predictions that the survival probability will scale as Dt/L^z, where L is the effective length of a step. This implies that the survival probability for large systems, when measured with fixed values of tm or Dt should also show little or no temperature dependence.Comment: 27 pages, 10 figure

Spiral Evolution in a Confined Geometry

Supported nanoscale lead crystallites with a step emerging from a non-centered screw dislocation on the circular top facet were prepared by rapid cooling from just above the melting temperature. STM observations of the top facet show a nonuniform rotation rate and shape of the spiral step as the crystallite relaxes. These features can be accurately modeled using curvature driven dynamics, as in classical models of spiral growth, with boundary conditions fixing the dislocation core and regions of the step lying along the outer facet edge.Comment: 4 pages, 3 figures, to be published in Physical Review Letter