The PdBI Arcsecond Whirlpool Survey (PAWS): The Role of Spiral Arms in Cloud and Star Formation

This is the final version of the article. Available from American Astronomical Society via the DOI in this record.The process that leads to the formation of the bright star-forming sites observed along prominent spiral arms remains elusive. We present results of a multi-wavelength study of a spiral arm segment in the nearby grand-design spiral galaxy M51 that belongs to a spiral density wave and exhibits nine gas spurs. The combined observations of the (ionized, atomic, molecular, dusty) interstellar medium with star formation tracers (H ii regions, young <10 Myr stellar clusters) suggest (1) no variation in giant molecular cloud (GMC) properties between arm and gas spurs, (2) gas spurs and extinction feathers arising from the same structure with a close spatial relation between gas spurs and ongoing/recent star formation (despite higher gas surface densities in the spiral arm), (3) no trend in star formation age either along the arm or along a spur, (4) evidence for strong star formation feedback in gas spurs, (5) tentative evidence for star formation triggered by stellar feedback for one spur, and (6) GMC associations being not special entities but the result of blending of gas arm/spur cross sections in lower resolution observations. We conclude that there is no evidence for a coherent star formation onset mechanism that can be solely associated with the presence of the spiral density wave. This suggests that other (more localized) mechanisms are important to delay star formation such that it occurs in spurs. The evidence of star formation proceeding over several million years within individual spurs implies that the mechanism that leads to star formation acts or is sustained over a longer timescale.S.E.M. and M.Q. acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG) via grant SCHI 536/7-2 as part of the priority program SPP 1573 "ISM-SPP: Physics of the Interstellar Medium." C.L.D. acknowledges funding from the European Research Council for the FP7 ERC starting grant project LOCALSTAR. J.P. acknowledges support from the CNRS programme Physique et Chimie du Milieu Interstellaire (PCMI). M.Q. acknowledges the International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD). S.G.B. thanks support from Spanish grant AYA2012-32295. We acknowledge financial support to the DAGAL network from the People Programme (Marie Curie Actions) of the European Unions Seventh Framework Programme FP7/2007-2013/ under REA grant agreement number PITN-GA-2011-289313. E.S. thanks NRAO for their support and hospitality during her visits in Socorro. E.S. thanks the Kavli Institute for Theoretical Physics for hospitality during the writing of this paper. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain)

The PdBI Arcsecond Whirlpool Survey (PAWS): Multi-phase cold gas kinematic of M51

This is the final version of the article. Available from the publisher via the DOI in this record.The kinematic complexity and the favorable position of M51 on the sky make this galaxy an ideal target to test different theories of spiral arm dynamics. Taking advantage of the new high-resolution PdBI Arcsecond Whirlpool Survey data, we undertake a detailed kinematic study of M51 to characterize and quantify the origin and nature of the non-circular motions. Using a tilted-ring analysis supported by several other archival data sets, we update the estimation of M51's position angle (P.A. = (173 ± 3)°) and inclination (i = (22 ± 5)°). Harmonic decomposition of the high-resolution (∼40 pc) CO velocity field shows the first kinematic evidence of an m = 3 wave in the inner disk of M51 with a corotation at R CR, m = 3 = 1.1 ± 0.1 kpc and a pattern speed of Ωp, m = 3 ≈ 140 km s -1 kpc-1. This mode seems to be excited by the nuclear bar, while the beat frequencies generated by the coupling between the m = 3 mode and the main spiral structure confirm its density-wave nature. We observe also a signature of an m = 1 mode that is likely responsible for the lopsidedness of M51 at small and large radii. We provide a simple method to estimate the radial variation of the amplitude of the spiral perturbation (V sp) attributed to the different modes. The main spiral arm structure has 〈V sp〉 = 50-70 km s-1, while the streaming velocity associated with the m = 1 and m = 3 modes is, in general, two times lower. Our joint analysis of H I and CO velocity fields at low and high spatial resolution reveals that the atomic and molecular gas phases respond differently to the spiral perturbation due to their different vertical distribution and emission morphology. © 2014. The American Astronomical Society. All rights reserved.We thank our anonymous referee for thoughtful comments that improved the quality of the paper. We thank the IRAM staff for their support during the observations with the Plateau de Bure interferometer and the 30 m telescope. D.C. and A.H. acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG) via grant SCHI 536/5-1 and SCHI 536/7-1 as part of the priority program SPP 1573 “ISM-SPP: Physics of the Interstellar Medium.” C.L.D. acknowledges funding from the European Research Council for the FP7 ERC starting grant project LOCALSTAR. T.A.T. acknowledges support from NASA grant No. NNX10AD01G. During this work, J.P. was partially funded by the grant ANR-09-BLAN-0231-01 from the French Agence Nationale de la Recherche as part of the SCHISM project (http://schism.ens.fr/). E.S., A.H. and D.C. thank NRAO for their support and hospitality during their visits in Charlottesville. E.S. thanks the Aspen Center for Physics and the NSF grant No. 1066293 for hospitality during the development and writing of this paper. D.C. thanks Glenn van de Ven for the useful discussion and the help with the harmonic decomposition code. S.G.B. acknowledges economic support from Junta de Andalucia grant P08 TIC 03531. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc

The PdBI Arcsecond Whirlpool Survey (PAWS): Environmental dependence of giant molecular cloud properties in M51

This is the final version of the article. Available fromAmerican Astronomical Society / IOP Publishing via the DOI in this recordUsing data from the PdBI Arcsecond Whirlpool Survey (PAWS), we have generated the largest extragalactic giant molecular cloud (GMC) catalog to date, containing 1507 individual objects. GMCs in the inner M51 disk account for only 54% of the total 12CO(1-0) luminosity of the survey, but on average they exhibit physical properties similar to Galactic GMCs. We do not find a strong correlation between the GMC size and velocity dispersion, and a simple virial analysis suggests that ∼30% of GMCs in M51 are unbound. We have analyzed the GMC properties within seven dynamically motivated galactic environments, finding that GMCs in the spiral arms and in the central region are brighter and have higher velocity dispersions than inter-arm clouds. Globally, the GMC mass distribution does not follow a simple power-law shape. Instead, we find that the shape of the mass distribution varies with galactic environment: the distribution is steeper in inter-arm region than in the spiral arms, and exhibits a sharp truncation at high masses for the nuclear bar region. We propose that the observed environmental variations in the GMC properties and mass distributions are a consequence of the combined action of large-scale dynamical processes and feedback from high-mass star formation. We describe some challenges of using existing GMC identification techniques for decomposing the 12CO(1-0) emission in molecule-rich environments, such as M51's inner disk. © 2014. The American Astronomical Society. All rights reserved

Gravitational torques imply molecular gas inflow towards the nucleus of M 51

PublishedJournal Article© 2016 ESO.The transport of gas towards the centre of galaxies is critical for black hole feeding and, indirectly, it can control active galactic nucleus (AGN) feedback. We have quantified the molecular gas inflow in the central R< 1 kpc of M 51 to be 1 M⊙/yr, using a new gravitational torque map and the molecular gas traced by the Plateau de Bure Interferometer Arcsecond Whirlpool Survey (PAWS). The nuclear stellar bar is responsible for this gas inflow. We also used torque profiles to estimate the location of dynamical resonances, and the results suggest a corotation for the bar CRbar ∼ 20″, and a corotation for the spiral CRsp ∼ 100″. We demonstrate how important it is to correct 3.6 μm images for dust emission when gravitational torques are to be computed, and we examine further sources of uncertainty. Our observational measurement of gas inflow can be compared with nuclear molecular outflow rates and provide useful constraints for numerical simulations.The authors would like to thank the anonymous referee for a helpful report, as well as Daniela Calzetti, Nick Z. Scoville and Mari Polletta for making the HST/F190N mosaic available to us. We also appreciate valuable comments from Françoise Combes and Sebastian Haan. We acknowledge financial support to the DAGAL network from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007- 2013/ under REA grant agreement number PITN-GA-2011-289313. M.Q. acknowledges the International Max Planck Research School for Astronomy and Cosmic Physics at the University of Heidelberg (IMPRS-HD). S.G.B. thanks support from Spanish grant AYA2012-32295. J.P. acknowledges support from the CNRS programme “Physique et Chimie du Milieu Interstellaire” (PCMI). M.Q., S.E.M., D.C. and A.H. acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG) via grants SCHI 536/7-2,SCHI 536/5-1, and SCHI 536/7-1 as part of the priority program SPP 1573 “ISM-SPP: Physics of the Interstellar Medium”

Short GMC lifetimes: an observational estimate with the PdBI Arcsecond Whirlpool Survey (PAWS)

PublishedJournal ArticleWe describe and execute a novel approach to observationally estimate the lifetimes of giant molecular clouds (GMCs). We focus on the cloud population between the two main spiral arms in M51 (the inter-arm region) where cloud destruction via shear and star formation feedback dominates over formation processes. By monitoring the change in GMC number densities and properties across the inter-arm, we estimate the lifetime as a fraction of the inter-arm travel time. We find that GMC lifetimes in M51's inter-arm are finite and short, 20-30 Myr. Over most of the region under investigation shear appears to regulate the lifetime. As the shear timescale increases with galactocentric radius, we expect cloud destruction to switch primarily to feedback at larger radii. We identify a transition from shear- to feedback-dominated disruption, finding that shear is more efficient at dispersing clouds, whereas feedback transforms the population, e.g., by fragmenting high-mass clouds into lower mass pieces. Compared to the characteristic timescale for molecular hydrogen in M51, our short lifetimes suggest that gas can remain molecular while clouds disperse and reassemble. We propose that galaxy dynamics regulates the cycling of molecular material from diffuse to bound (and ultimately star-forming) objects, contributing to long observed molecular depletion times in normal disk galaxies. We also speculate that, in extreme environments like elliptical galaxies and concentrated galaxy centers, star formation can be suppressed when the shear timescale is short enough that some clouds will not survive to form stars.We thank the IRAM staff for their support during the observations with the Plateau de Bure interferometer and the 30 m telescope. S.E.M., D.C., and A.H. acknowledge funding from the Deutsche Forschungsgemeinschaft (DFG) via grants SCHI 536/7-2, SCHI 536/5-1, and SCHI 536/7-1 as part of the priority program SPP 1573 “ISM-SPP: Physics of the Interstellar Medium.” C.L.D. acknowledges funding from the European Research Council for the FP7 ERC starting grant project LOCALSTAR. T.A.T. acknowledges support from NASA grant number NNX10AD01G. J.P. acknowledges support from the CNRS program “Physique et Chimie du Milieu Interstellaire” (PCMI). M.Q. acknowledges financial support to the DAGAL network from the People Programme (Marie Curie Actions) of the European Union’s Seventh Framework Programme FP7/2007-2013/ under REA grant agreement number PITN-GA-2011-289313

Transkingdom Networks: A Systems Biology Approach to Identify Causal Members of Host-Microbiota Interactions

Improvements in sequencing technologies and reduced experimental costs have resulted in a vast number of studies generating high-throughput data. Although the number of methods to analyze these "omics" data has also increased, computational complexity and lack of documentation hinder researchers from analyzing their high-throughput data to its true potential. In this chapter we detail our data-driven, transkingdom network (TransNet) analysis protocol to integrate and interrogate multi-omics data. This systems biology approach has allowed us to successfully identify important causal relationships between different taxonomic kingdoms (e.g. mammals and microbes) using diverse types of data

Predicting ICU survival: A meta-level approach

<p>Abstract</p> <p>Background</p> <p>The performance of separate Intensive Care Unit (ICU) status scoring systems vis-à-vis prediction of outcome is not satisfactory. Computer-based predictive modeling techniques may yield good results but their performance has seldom been extensively compared to that of other mature or emerging predictive models. The objective of the present study was twofold: to propose a prototype meta-level predicting approach concerning Intensive Care Unit (ICU) survival and to evaluate the effectiveness of typical mining models in this context.</p> <p>Methods</p> <p>Data on 158 men and 46 women, were used retrospectively (75% of the patients survived). We used Glasgow Coma Scale (GCS), Acute Physiology And Chronic Health Evaluation II (APACHE II), Sequential Organ Failure Assessment (SOFA) and Injury Severity Score (ISS) values to structure a decision tree (DTM), a neural network (NNM) and a logistic regression (LRM) model and we evaluated the assessment indicators implementing Receiver Operating Characteristics (ROC) plot analysis.</p> <p>Results</p> <p>Our findings indicate that regarding the assessment of indicators' capacity there are specific discrete limits that should be taken into account. The Az score ± SE was 0.8773± 0.0376 for the DTM, 0.8061± 0.0427 for the NNM and 0.8204± 0.0376 for the LRM, suggesting that the proposed DTM achieved a near optimal Az score.</p> <p>Conclusion</p> <p>The predicting processes of ICU survival may go "one step forward", by using classic composite assessment indicators as variables.</p

Introduction of Solid Food to Young Infants

Timing of the first introduction of solid food during infancy may have potential effects on life-long health. To understand the characteristics that are associated with the timing of infants’ initial exposure to solid foods. The 2000 National Survey of Early Childhood Health (NSECH) was a nationally representative telephone survey of 2,068 parents of children aged 4–35 months, which profiled content and quality of health care for young children. African-American and Latino families were over-sampled. Analyses in this report include bivariate tests and logistic regressions. 62% of parents reported introducing solids to their child between 4–6 months of age. African-American mothers (OR = 0.5 [0.3, 0.9]), English-speaking Latino mothers (OR = 0.4 [0.2, 0.7]), White mothers with more than high school education (OR = 0.5 [0.2, 1.0]), and mothers who breastfed for 4 months or longer (OR = 0.4 [0.3, 0.7]) were less likely to introduce solids early. Most parents (92%) of children 4–9 months of age reported that their pediatric provider had discussed introduction of solids with them since the child’s birth, and provider discussion of feeding was not associated with the timing of introduction of solids. Although most parents recall discussing the introduction of solid foods with their child’s physician, several subgroups of mothers introduce solid foods earlier than the AAP recommendation of 4–6 months. More effective discussion of solid food introduction linked to counseling and support of breastfeeding by the primary health care provider may reduce early introduction of solids

Caenorhabditis elegans Semi-Automated Liquid Screen Reveals a Specialized Role for the Chemotaxis Gene cheB2 in Pseudomonas aeruginosa Virulence

Pseudomonas aeruginosa is an opportunistic human pathogen that causes infections in a variety of animal and plant hosts. Caenorhabditis elegans is a simple model with which one can identify bacterial virulence genes. Previous studies with C. elegans have shown that depending on the growth medium, P. aeruginosa provokes different pathologies: slow or fast killing, lethal paralysis and red death. In this study, we developed a high-throughput semi-automated liquid-based assay such that an entire genome can readily be scanned for virulence genes in a short time period. We screened a 2,200-member STM mutant library generated in a cystic fibrosis airway P. aeruginosa isolate, TBCF10839. Twelve mutants were isolated each showing at least 70% attenuation in C. elegans killing. The selected mutants had insertions in regulatory genes, such as a histidine kinase sensor of two-component systems and a member of the AraC family, or in genes involved in adherence or chemotaxis. One mutant had an insertion in a cheB gene homologue, encoding a methylesterase involved in chemotaxis (CheB2). The cheB2 mutant was tested in a murine lung infection model and found to have a highly attenuated virulence. The cheB2 gene is part of the chemotactic gene cluster II, which was shown to be required for an optimal mobility in vitro. In P. aeruginosa, the main player in chemotaxis and mobility is the chemotactic gene cluster I, including cheB1. We show that, in contrast to the cheB2 mutant, a cheB1 mutant is not attenuated for virulence in C. elegans whereas in vitro motility and chemotaxis are severely impaired. We conclude that the virulence defect of the cheB2 mutant is not linked with a global motility defect but that instead the cheB2 gene is involved in a specific chemotactic response, which takes place during infection and is required for P. aeruginosa pathogenicity

Toward an integrated observing system for ocean carbon and biogeochemistry at a time of change

peer reviewedOcean biogeochemical cycles are currently undergoing fundamental changes – largely as a consequence of the addition of greenhouse gases to the atmosphere. The oceans are getting warmer, and their pH and oxygen levels are decreasing. Further changes may arise as a consequence of the perturbation of the global nitrogen cycle, leading to higher inputs of fixed nitrogen to the ocean by rivers and enhanced deposition of nitrogen to the surface ocean. These biogeochemical changes plus the concomitant changes in ocean circulation will have profound effects on some of the ocean’s key services, i.e. its capability to mitigate climate change by removing anthropogenic CO2 from the atmosphere, and its provision of important ecosystem services such as food and biodiversity. Documenting, understanding, and predicting these biogeochemical changes require a concerted and sustained observational effort that includes both the continuation of well-tested approaches and the development and implementation of novel systems. Of particular importance for the first set of approaches are the sustaining and extension of (i) a surface ocean volunteer ocean ship-based observing system primarily focusing on the determination of the air-sea exchange of CO2 and upper ocean changes in carbonate chemistry, of (ii) an interior ocean research-ship based system focusing on large-scale interior changes of the ocean’s biogeochemistry (carbon, oxygen, nutrients, etc), and of (iii) ship-based and moored time-series observations at key sites, including the coastal ocean. Of particular importance for the second set of approaches are (i) the accelerated improvement, development and implementation of new observational elements on the Argo array (especially oxygen, but also nutrient and bio-optical sensors), and (ii) the development, testing, and deployment of novel sensors for the ocean’s carbon system. Concerted synthesis efforts involving also novel approaches for merging observations with biogeochemical models will ensure that these observational elements realize their synergistic potential