Submillimeter CO emission from shock-heated gas in the L1157 outflow

We present the CO J=6-5, 4-3, and 3-2 spectra from the blueshifted gas of the outflow driven by the low-mass class 0 protostar in the L1157 dark cloud. Strong submillimeter CO emission lines with T_mb > 30 K have been detected at 63" (~0.13 pc) south from the protostar. It is remarkable that the blue wings in the submillimeter lines are stronger by a factor of 3-4 than that of the CO J=1-0 emission line. The CO line ratios suggest that the blueshifted lobe of this outflow consists of moderately dense gas of n(H_2) = (1-3)x10^4 cm^-3 heated to T_kin = 50-170 K.It is also suggested that the kinetic temperature of the outflowing gas increases from ~80 K near the protostar to ~170 K at the shocked region in the lobe center, toward which the largest velocity dispersion of the CO emission is observed. A remarkable correlation between the kinetic temperature and velocity dispersion of the CO emission along the lobe provides us with direct evidence that the molecular gas at the head of the jet-driven bow shock is indeed heated kinematically. The lower temperature of ~80 K measured at the other shocked region near the end of the lobe is explained if this shock is in a later evolutionary stage, in which the gas has been cooled mainly through radiation of the CO rotational lines.Comment: 10 pages, 4 PDF figures, APJL in pres

Repeated Bursts from Relativistic Scattering of Compact Objects in Galactic Nuclei

Galactic nuclei are densely populated by stellar mass compact objects such as black holes and neutron stars. Bound, highly eccentric binaries form as a result of gravitational wave (GW) losses during close flybys between these objects. We study the evolution of these systems using 2.5 and 3.5 order post-Newtonian equations of motion. The GW signal consists of many thousand repeated bursts (RB) for minutes to days (depending on the impact parameter and masses), followed by a powerful GW chirp and an eccentric merger. We show that a significant signal to noise ratio (SNR) accumulates already in the RB phase, corresponding to a detection limit around 200-300 Mpc and 300--600 Mpc for Advanced LIGO for an average orientation BH/NS or BH/BH binary, respectively. The theoretical errors introduced by the inaccuracy of the PN templates are typically much less severe for the RB phase than in the following eccentric merger. The GW signal in the RB phase is broadband; we show that encounters involving intermediate mass black holes are detectable in multiple frequency bands coincidentally using LIGO and LISA.Comment: 16 pages, 10 figures, version accepted for publication in Physical Review

Giant Molecular Outflows Powered by Protostars in L1448

We present sensitive, large-scale maps of the CO J=1-0 emission of the L1448 dark cloud. These maps were acquired using the On-The-Fly capability of the NRAO 12-meter telescope. CO outflow activity is seen in L1448 on parsec-scales for the first time. Careful comparison of the spatial and velocity distribution of our high-velocity CO maps with previously published optical and near-infrared images and spectra has led to the identification of six distinct CO outflows. We show the direct link between the heretofore unknown, giant, highly-collimated, protostellar molecular outflows and their previously discovered, distant optical manifestations. The outflows traced by our CO mapping generally reach the projected cloud boundaries. Integrated intensity maps over narrow velocity intervals indicate there is significant overlap of blue- and red-shifted gas, suggesting the outflows are highly inclined with respect to the line-of-sight, although the individual outflow position angles are significantly different. The velocity channel maps also show that the outflows dominate the CO line cores as well as the high-velocity wings. The magnitude of the combined flow momenta, as well as the combined kinetic energy of the flows, are sufficient to disperse the 50 solar mass NH3 cores in which the protostars are currently forming, although some question remains as to the exact processes involved in redirecting the directionality of the outflow momenta to effect the complete dispersal of the parent cloud.Comment: 11 pages, 9 figures, to be published in the Astronomical Journa

SiO Emission in the Multi-Lobe Outflow associated with IRAS 16293-2422

We have mapped the thermal emission line of SiO (v = 0; J = 2-1) associated with the quadrupolar molecular outflow driven by the very cold far-infrared source IRAS 16293-2422. The SiO emission is significantly enhanced in the northeastern red lobe and at the position ~50" east of the IRAS source. Strong SiO emission observed at ~50" east of the IRAS source presents evidence for a dynamical interaction between a part of the eastern blue lobe and the dense ambient gas condensation, however, such an interaction is unlikely to be responsible for producing the quadrupolar morphology. The SiO emission in the northeastern red lobe shows the spatial and velocity structure similar to those of the CO outflow, suggesting that the SiO emission comes from the molecular outflow in the northeastern red lobe itself. The observed velocity structure is reproduced by a simple spatio-kinematic model of bow shock with a shock velocity of 19-24 km/s inclined by 30-45 deg from the plane of the sky. This implies that the northeastern red lobe is independent of the eastern blue lobe and that the quadrupolar structure is due to two separate bipolar outflows. The SiO emission observed in the western red lobe has a broad pedestal shape with low intensity. Unlike the SiO emission in the northeastern red lobe, the spatial extent of the SiO emission in the western red lobe is restricted to its central region. The spatial and velocity structures and the line profiles suggest that three different types of the SiO emission are observed in this outflow; the SiO emission arises from the interface between the outflowing gas and the dense ambient gas clump, the SiO emission coming from the outflow lobe itself, and the broad SiO emission with low intensity observed at the central region of the outflow lobe.Comment: 14 pages, 6 figures (figures 1 and 4 are color), gzipped tar file, To appear in the Ap

Turbulence driven by outflow-blown cavities in the molecular cloud of NGC 1333

Outflows from young stellar objects have been identified as a possible source of turbulence in molecular clouds. To investigate the relationship between outflows, cloud dynamics and turbulence, we compare the kinematics of the molecular gas associated with NGC 1333, traced in 13CO(1-0), with the distribution of young stellar objects (YSOs) within. We find a velocity dispersion of ~ 1-1.6 km/s in 13CO that does not significantly vary across the cloud, and is uncorrelated with the number of nearby young stellar outflows identified from optical and submillimeter observations. However, from velocity channel maps we identify about 20 cavities or depressions in the 13CO intensity of scales > 0.1-0.2 pc and velocity widths 1-3 km/s. The cavities exhibit limb brightened rims in both individual velocity channel maps and position velocity diagrams, suggesting that they are slowly expanding. We interpret these cavities to be remnants of past YSO outflow activity: If these cavities are presently empty, they would fill in on time scales of a million years. This can exceed the lifetime of a YSO outflow phase, or the transit time of the central star through the cavity, explaining the the absence of any clear correlation between the cavities and YSO outflows. We find that the momentum and energy deposition associated with the expansion of the cavities is sufficient to power the turbulence in the cloud. In this way we conclude that the cavities are an important intermediary step between the conversion of YSO outflow energy and momentum into cloud turbulent motions.Comment: Accepted for publication in ApJ. Check out http://astro.pas.rochester.edu/~aquillen/coolpics.html for channel map and PosVel movies of N133

Quantum and semiclassical study of magnetic anti-dots

We study the energy level structure of two-dimensional charged particles in inhomogeneous magnetic fields. In particular, for magnetic anti-dots the magnetic field is zero inside the dot and constant outside. Such a device can be fabricated with present-day technology. We present detailed semiclassical studies of such magnetic anti-dot systems and provide a comparison with exact quantum calculations. In the semiclassical approach we apply the Berry-Tabor formula for the density of states and the Borh-Sommerfeld quantization rules. In both cases we found good agreement with the exact spectrum in the weak magnetic field limit. The energy spectrum for a given missing flux quantum is classified in six possible classes of orbits and summarized in a so-called phase diagram. We also investigate the current flow patterns of different quantum states and show the clear correspondence with classical trajectories.Comment: 14 pages, 13 figure

Adipocyte-specific protein tyrosine phosphatase 1B deletion increases lipogenesis, adipocyte cell size and is a minor regulator of glucose homeostasis

Peer reviewedPublisher PD

Evaluating consumptive and nonconsumptive predator effects on prey density using field time‐series data

Determining the degree to which predation affects prey abundance in natural communities constitutes a key goal of ecological research. Predators can affect prey through both consumptive effects (CEs) and nonconsumptive effects (NCEs), although the contributions of each mechanism to the density of prey populations remain largely hypothetical in most systems. Common statistical methods applied to time‐series data cannot elucidate the mechanisms responsible for hypothesized predator effects on prey density (e.g., differentiate CEs from NCEs), nor can they provide parameters for predictive models. State‐space models (SSMs) applied to time‐series data offer a way to meet these goals. Here, we employ SSMs to assess effects of an invasive predatory zooplankter, Bythotrephes longimanus, on an important prey species, Daphnia mendotae, in Lake Michigan. We fit mechanistic models in an SSM framework to seasonal time series (1994–2012) using a recently developed, maximum‐likelihood–based optimization method, iterated filtering, which can overcome challenges in ecological data (e.g., nonlinearities, measurement error, and irregular sampling intervals). Our results indicate that B. longimanus strongly influences D. mendotae dynamics, with mean annual peak densities of B. longimanus observed in Lake Michigan estimated to cause a 61% reduction in D. mendotae population growth rate and a 59% reduction in peak biomass density. Further, the observed B. longimanus effect is most consistent with an NCE via reduced birth rates. The SSM approach also provided estimates for key biological parameters (e.g., demographic rates) and the contribution of dynamic stochasticity and measurement error. Our study therefore provides evidence derived directly from survey data that the invasive zooplankter B. longimanus is affecting zooplankton demographics and offer parameter estimates needed to inform predictive models that explore the effect of B. longimanus under different scenarios, such as climate change.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/148243/1/ecy2583-sup-0001-AppendixS1.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148243/2/ecy2583_am.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/148243/3/ecy2583.pd

Disruption of Arp2/3 results in asymmetric structural plasticity of dendritic spines and progressive synaptic and behavioral abnormalities

Despite evidence for a strong genetic contribution to several major psychiatric disorders, individual candidate genes account for only a small fraction of these disorders, leading to the suggestion that multigenetic pathways may be involved. Several known genetic risk factors for psychiatric disease are related to the regulation of actin polymerization, which plays a key role in synaptic plasticity. To gain insight into and test the possible pathogenetic role of this pathway, we designed a conditional knock-out of the Arp2/3 complex, a conserved final output for actin signaling pathways that orchestrates de novo actin polymerization. Here we report that postnatal loss of the Arp2/3 subunit ArpC3 in forebrain excitatory neurons leads to an asymmetric structural plasticity of dendritic spines, followed by a progressive loss of spine synapses. This progression of synaptic deficits corresponds with an evolution of distinct cognitive, psychomotor, and social disturbances as the mice age. Together, these results point to the dysfunction of actin signaling, specifically that which converges to regulate Arp2/3, as an important cellular pathway that may contribute to the etiology of complex psychiatric disorders