Halo substructure in the SDSS--Gaia catalogue: streams and clumps

We use the SDSS-Gaia Catalogue to identify six new pieces of halo substructure. SDSS-Gaia is an astrometric catalogue that exploits SDSS data release 9 to provide first epoch photometry for objects in the Gaia source catalogue. We use a version of the catalogue containing $245\,316$ stars with all phase space coordinates within a heliocentric distance of $\sim 10$ kpc. We devise a method to assess the significance of halo substructures based on their clustering in velocity space. The two most substantial structures are multiple wraps of a stream which has undergone considerable phase mixing (S1, with 94 members) and a kinematically cold stream (S2, with 61 members). The member stars of S1 have a median position of ($X,Y,Z$) = ($8.12, -0.22, 2.75$) kpc and a median metallicity of [Fe/H] $= -1.78$. The stars of S2 have median coordinates ($X,Y,Z$) = ($8.66, 0.30, 0.77$) kpc and a median metallicity of [Fe/H] $= -1.91$. They lie in velocity space close to some of the stars in the stream reported by Helmi et al. (1999). By modelling, we estimate that both structures had progenitors with virial masses $\approx 10^{10} M_\odot$ and infall times $\gtrsim 9$ Gyr ago. Using abundance matching, these correspond to stellar masses between $10^6$ and $10^7 M_\odot$. These are somewhat larger than the masses inferred through the mass-metallicity relation by factors of 5 to 15. Additionally, we identify two further substructures (S3 and S4 with 55 and 40 members) and two clusters or moving groups (C1 and C2 with 24 and 12) members. In all 6 cases, clustering in kinematics is found to correspond to clustering in both configuration space and metallicity, adding credence to the reliability of our detections.GCM thanks Boustany Foundation, Cambridge Commonwealth, European & International Trust and Isaac Newton Studentship for their support on his work. ... The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant Agreement n. 308024

Coupling models of cattle and farms with models of badgers for predicting the dynamics of bovine tuberculosis (TB)

Bovine TB is a major problem for the agricultural industry in several countries. TB can be contracted and spread by species other than cattle and this can cause a problem for disease control. In the UK and Ireland, badgers are a recognised reservoir of infection and there has been substantial discussion about potential control strategies. We present a coupling of individual based models of bovine TB in badgers and cattle, which aims to capture the key details of the natural history of the disease and of both species at approximately county scale. The model is spatially explicit it follows a very large number of cattle and badgers on a different grid size for each species and includes also winter housing. We show that the model can replicate the reported dynamics of both cattle and badger populations as well as the increasing prevalence of the disease in cattle. Parameter space used as input in simulations was swept out using Latin hypercube sampling and sensitivity analysis to model outputs was conducted using mixed effect models. By exploring a large and computationally intensive parameter space we show that of the available control strategies it is the frequency of TB testing and whether or not winter housing is practised that have the most significant effects on the number of infected cattle, with the effect of winter housing becoming stronger as farm size increases. Whether badgers were culled or not explained about 5%, while the accuracy of the test employed to detect infected cattle explained less than 3% of the variance in the number of infected cattle

Effects of growth rate, size, and light availability on tree survival across life stages: a demographic analysis accounting for missing values and small sample sizes.

The data set supporting the results of this article is available in the Dryad repository, http://dx.doi.org/10.5061/dryad.6f4qs. Moustakas, A. and Evans, M. R. (2015) Effects of growth rate, size, and light availability on tree survival across life stages: a demographic analysis accounting for missing values.Plant survival is a key factor in forest dynamics and survival probabilities often vary across life stages. Studies specifically aimed at assessing tree survival are unusual and so data initially designed for other purposes often need to be used; such data are more likely to contain errors than data collected for this specific purpose

The Sausage Globular Clusters

The Gaia Sausage is an elongated structure in velocity space discovered by Belokurov et al. using the kinematics of metal-rich halo stars. They showed that it could be created by a massive dwarf galaxy (∼5 1010 ) on a strongly radial orbit that merged with the Milky Way at a redshift z ≲ 3. This merger would also have brought in globular clusters (GCs). We seek evidence for the associated Sausage Globular Clusters (GCs) by analyzing the structure of 91 Milky Way GCs in action space using the Gaia Data Release 2 catalog, complemented with Hubble Space Telescope proper motions. There is a characteristic energy that separates the in situ objects, such as the bulge/disk clusters, from the accreted objects, such as the young halo clusters. There are 15 old halo GCs that have E > . Eight of the high-energy, old halo GCs are strongly clumped in azimuthal and vertical action, yet strung out like beads on a chain at extreme radial action. They are very radially anisotropic (β ∼ 0.95) and move on orbits that are all highly eccentric (e 0.80). They also form a track in the age-metallicity plane compatible with a dwarf galaxy origin. These properties are consistent with GCs associated with the merger event that gave rise to the Gaia Sausage

The Milky Way Halo in Action Space

We analyze the structure of the local stellar halo of the Milky Way using ~60000 stars with full phase space coordinates extracted from the SDSS–Gaia catalog. We display stars in action space as a function of metallicity in a realistic axisymmetric potential for the Milky Way Galaxy. The metal-rich population is more distended toward high radial action J R as compared to azimuthal or vertical action, J phgr or J z . It has a mild prograde rotation $(\langle {v}_{\phi }\rangle \approx 25\,\mathrm{km}\,{{\rm{s}}}^{-1}$), is radially anisotropic and highly flattened, with axis ratio q ≈ 0.6–0.7. The metal-poor population is more evenly distributed in all three actions. It has larger prograde rotation $(\langle {v}_{\phi }\rangle \approx 50\,\mathrm{km}\,{{\rm{s}}}^{-1}$), a mild radial anisotropy, and a roundish morphology (q ≈ 0.9). We identify two further components of the halo in action space. There is a high-energy, retrograde component that is only present in the metal-rich stars. This is suggestive of an origin in a retrograde encounter, possibly the one that created the stripped dwarf galaxy nucleus, ωCentauri. Also visible as a distinct entity in action space is a resonant component, which is flattened and prograde. It extends over a range of metallicities down to [Fe/H] ≈ −3. It has a net outward radial velocity $\langle {v}_{R}\rangle \approx 12\,\mathrm{km}\,{{\rm{s}}}^{-1}$ within the solar circle at $| z| \lt 3.5\,\mathrm{kpc}$. The existence of resonant stars at such extremely low metallicities has not been seen before.G.C.M. thanks the Boustany Foundation, Cambridge Commonwealth, European & International Trust and Isaac Newton Studentship for their support of his work. J.L.S. thanks the Science and Technology Facilities Council for financial support. The research leading to these results has received partial support from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013) / ERC Grant agreement No. 308024. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement

Discovery of new retrograde substructures: The shards of ω Centauri?

We use the Sloan Digital Sky Survey (SDSS)-Gaia catalogue to search for substructure in the stellar halo. The sample comprises 62 133 halo stars with full phase space coordinates and extends out to heliocentric distances of ~10 kpc. As actions are conserved under slow changes of the potential, they permit identification of groups of stars with a common accretion history. We devise a method to identify halo substructures based on their clustering in action space, using metallicity as a secondary check. This is validated against smooth models and numerical constructed stellar haloes from the Aquarius simulations. We identify 21 substructures in the SDSS-Gaia catalogue, including seven high-significance, high-energy and retrograde ones. We investigate whether the retrograde substructures may be material stripped offthe atypical globular cluster ω Centauri. Using a simple model of the accretion of the progenitor of the ω Centauri, we tentatively argue for the possible association of up to five of our new substructures (labelled Rg1, Rg3, Rg4, Rg6 and Rg7) with this event. This sets a minimum mass of 5 × 108M⊙ for the progenitor, so as to bring ω Centauri to its current location in action-energy space. Our proposal can be tested by high-resolution spectroscopy of the candidates to look for the unusual abundance patterns possessed by ω Centauri stars

A Halo Substructure in Gaia Data Release 1

We identify a halo substructure in the Tycho Gaia Astrometric Solution (TGAS) data set, cross-matched with the Radial Velocity Experiment (RAVE-on) data release. After quality cuts, the stars with large radial action (JR > 800 km s−1 kpc) are extracted. A subset of these stars is clustered in longitude and velocity and can be selected with further cuts. The 14 stars are centred on (X, Y, Z) ≈ (9.0, −1.0, −0.6) kpc and form a coherently moving structure in the halo with median (vR, vϕ, vz) = (167.33, 0.86, −94.85) km s−1. They are all metal-poor giants with median [Fe/H] = −0.83. To guard against the effects of distance errors, we compute spectrophotometric distances for 8 out of the 14 stars where this is possible. We find that six of the stars are still comoving. These six stars also have a much tighter [Fe/H] distribution ∼−0.7 with one exception ([Fe/H] = −2.12). We conclude that the existence of the comoving cluster is stable against changes in distance estimation and conjecture that this is the dissolving remnant of a globular cluster accreted long ago.GCM thanks the Boustany Foundation, Cambridge Commonwealth, European & International Trust, and Issac Newton Studentship for their support on his work. SEK thanks the United Kingdom Science and Technology Council (STFC) for the award of an Ernest Rutherford fellowship (grant number ST/N004493/1)

Lingual Salt Glands in Crocodylus acutus and C. johnstoni and Their Absence from Alligator mississipiensis and Caiman crocodilus

1. Lingual salt glands, secreting hyperosmotic Na/K solutions in response to methacholine, are present in Crocodylus acutus and C. johnstoni but apparently absent from the alligatorids, Alligator mississipiensis and Caiman crocodilus. 2. Both secretory rates (6-20 [micro-mol/100 g-h) and concentrations (450-600 mM Na) of glandular secretions are essentially identical in the marine/estuarine C. acutus and C. porosus and significantly higher than in the freshwater C. johnstoni (1-2 micro-mol/100 g-h; 320-420 mM Na). 3. Lingual glands in Alligator secrete isosmotic Na/K at low rates (1-2 micro-mol/100 g-h) while those of Caiman show no response to methacholine. 4. The physiological contrast between alligatorids and crocodylids is reflected in distinct differences in the superficial appearance of the tongue and lingual pores. 5. It is postulated that the alligatorid condition of low secretory capacity and isosmotic secretion reflects the primitive salivary function of lingual glands from which the salt-secreting capability in crocodylids was derived

A new rhynchocephalian from the late jurassic of Germany with a dentition that is unique amongst tetrapods.

Rhynchocephalians, the sister group of squamates (lizards and snakes), are only represented by the single genus Sphenodon today. This taxon is often considered to represent a very conservative lineage. However, rhynchocephalians were common during the late Triassic to latest Jurassic periods, but rapidly declined afterwards, which is generally attributed to their supposedly adaptive inferiority to squamates and/or Mesozoic mammals, which radiated at that time. New finds of Mesozoic rhynchocephalians can thus provide important new information on the evolutionary history of the group. A new fossil relative of Sphenodon from the latest Jurassic of southern Germany, Oenosaurus muehlheimensis gen. et sp. nov., presents a dentition that is unique amongst tetrapods. The dentition of this taxon consists of massive, continuously growing tooth plates, probably indicating a crushing dentition, thus representing a previously unknown trophic adaptation in rhynchocephalians. The evolution of the extraordinary dentition of Oenosaurus from the already highly specialized Zahnanlage generally present in derived rhynchocephalians demonstrates an unexpected evolutionary plasticity of these animals. Together with other lines of evidence, this seriously casts doubts on the assumption that rhynchocephalians are a conservative and adaptively inferior lineage. Furthermore, the new taxon underlines the high morphological and ecological diversity of rhynchocephalians in the latest Jurassic of Europe, just before the decline of this lineage on this continent. Thus, selection pressure by radiating squamates or Mesozoic mammals alone might not be sufficient to explain the demise of the clade in the Late Mesozoic, and climate change in the course of the fragmentation of the supercontinent of Pangaea might have played a major role

Benzyne in V4334 Sqr: A Quest for the Ring with SOFIA/EXES

Large aromatic molecules are ubiquitous in both circumstellar and interstellar environments. Detection of small aromatic molecules, such as benzene (C6H6) and benzyne (C6H4), are rare in astrophysical environments. Detection of such species will have major implications for our understanding of the astrochemistry involved in the formation of the molecules necessary for life, including modeling the chemical pathways to the formation of larger hydrocarbon molecules. We conducted a search for the infrared 18 μm spectral signature of benzyne in V4334 Sgr with the Stratospheric Observatory for Infrared Astronomy (SOFIA)/Echelon-Cross-Echelle Spectrograph (EXES) finding no evidence for a feature at the sensitivity of our observations