Search

In this work a search was carried out for globular clusters belonging to the Sagittarius (Sgr) tidal stream using the analysis of spatial positions, radial velocities relative to the Galactic Standard of Rest (V_{GSR}),proper motions and ratio of "age -- metallicity" ([Fe/H]) for globular clusters and for stars in the tidal stream. As a result, three categories of globular clusters were obtained: A -- most certainly in the stream: Terzan 8, Whiting 1, Arp 2, NGC 6715, Terzan 7, Pal 12; B -- kinematic outliers: Pal 5, NGC 5904, NGC 5024, NGC 5053, NGC 5272, NGC 288; C -- lowest rank candidates: NGC 6864, NGC 5466, NGC 5897, NGC 7492, NGC 4147.

We use the astrometric and photometric data from Gaia Data Release 2 and line-of-sight velocities from various other surveys to study the 3d structure and kinematics of the Sagittarius dwarf galaxy. The combination of photometric and astrometric data makes it possible to obtain a very clean separation of Sgr member stars from the Milky Way foreground; our final catalogue contains ~2.6e5 candidate members with magnitudes G, matches published version

Using wide-field $^{13}$CO ($J=1-0$) data taken with the Nobeyama 45-m telescope, we investigate cloud structures of the infrared dark cloud complex in M17 with SCIMES. In total, we identified 118 clouds that contain 11 large clouds with radii larger than 1 pc. The clouds are mainly distributed in the two representative velocity ranges of 10 $-$ 20 km s$^{-1}$ and 30 $-$ 40 km s$^{-1}$. By comparing with the ATLASGAL catalog, we found that the majority of the $^{13}$CO clouds with 10 $-$ 20 km s$^{-1}$ and 30 $-$ 40 km s$^{-1}$ are likely located at distances of 2 kpc (Sagittarius arm) and 3 kpc (Scutum arm), respectively. Analyzing the spatial configuration of the identified clouds and their velocity structures, we attempt to reveal the origin of the cloud structure in this region. Here we discuss three possibilities: (1) overlapping with different velocities, (2) cloud oscillation, and (3) cloud-cloud collision. From the position-velocity diagrams, we found spatially-extended faint emission between $\sim$ 20 km s$^{-1}$ and $\sim$ 35 km s$^{-1}$, which is mainly distributed in the spatially-overlapped areas of the clouds. We also found that in some areas where clouds with different velocities overlapped, the magnetic field orientation changes abruptly. The distribution of the diffuse emission in the position-position-velocity space and the bending magnetic fields appear to favor the cloud-cloud collision scenario compared to other scenarios. In the cloud-cloud collision scenario, we propose that two $\sim$35 km s$^{-1}$ foreground clouds are colliding with clouds at $\sim$20 km s$^{-1}$ with a relative velocity of 15 km s$^{-1}$. These clouds may be substructures of two larger clouds having velocities of $\sim$ 35 km s$^{-1}$ ($\gtrsim 10^3 $ M$_{\odot}$) and $\sim$ 20 km s$^{-1}$ ($\gtrsim 10^4 $ M$_{\odot}$), respectively., Comment: 34 pages, 13 figures, Accepted for publication in PASJ

Satellites orbiting disk galaxies can induce phase space features such as spirality, vertical heating and phase-mixing in their disks. Such features have also been observed in our own Galaxy, but the complexity of the Milky Way disk has only recently been fully mapped by Gaia Data Release 2 (DR2) data. This complex behaviour is mainly ascribed to repeated perturbations induced by the Sagittarius dwarf galaxy (Sgr) along its orbit, pointing to this satellite as the main dynamical architect of the Milky Way disk. Here, we model Gaia DR2-observed colour–magnitude diagrams to obtain a detailed star formation history of the ~2 kpc bubble around the Sun. It reveals three conspicuous and narrow episodes of enhanced star formation that we can precisely date as having occurred 5.7, 1.9 and 1.0 Gyr ago. The timing of these episodes coincides with proposed Sgr pericentre passages according to (1) orbit simulations, (2) phase space features in the Galactic disk and (3) Sgr stellar content. These findings most probably suggest that Sgr has also been an important actor in the build-up of the stellar mass of the Milky Way disk, with the perturbations from Sgr repeatedly triggering major episodes of star formation. Galactic close encounters can induce gravitational effects in the participants. Here Ruiz-Lara et al. have reconstructed the star formation history of the region of our Galaxy close to the Sun, finding that three recent visits of the neighbouring Sagittarius dwarf galaxy have resulted in well-defined episodes of star formation.

We obtain distances to a sample of RR Lyrae in the central core of the Sagittarius dwarf spheroidal galaxy from OGLE data. We use these distances, along with RR Lyrae from Gaia DR2, to measure the shape of the stellar distribution within the central ∼2 kpc. The best-fitting stellar distribution is triaxial, with axis ratios 1 : 0.76 : 0.43. A prolate-spheroid model is ruled out at high statistical significance relative to the triaxial model. The major axis is aligned nearly parallel to the sky plane as seen by an Earth-based observer and is nearly perpendicular to the direction of the Galactic Centre. This result may be compared to cosmological simulations which generally predict that the major axis of the dark matter distribution of subhalos is aligned with the Galactic Centre. The triaxial structure that we obtain can provide important constraints on the Sagittarius progenitor, as well as the central dark matter distribution under the assumption of dynamical equilibrium.

Podonychus gyobusp. nov., a second species of the genusPodonychusJäch & Kodada, 1997, hitherto known only from Indonesia, is described from Kyushu, Japan. This new species is similar toP. sagittariusJäch & Kodada, 1997, but differs from it in the straight penis, arcuate 2ndlabial palpomere, and in the 3rdantennomere being longer than wide. The endophallic structures and the larva ofP. gyobusp. nov.are described. A character matrix of the Macronychini genera and a key to the Japanese genera are provided.

The GD-1 stream is one of the longest and coldest stellar streams discovered to date, and one of the best objects for constraining the dark matter properties of the Milky Way. Using data from Gaia DR2, we study the proper motions (PMs), distance, morphology, and density of the stream to uncover small-scale perturbations. The PM cleaned data show a clear distance gradient across the stream, ranging from 7 to 12 kpc. However, unlike earlier studies that found a continuous gradient, we uncover a distance minimum at φ1 ≈ −40 deg, after which the distance increases again. We can reliably trace the stream between −85 < φ1, TdB and MG acknowledge support from the European Research Council (ERC, StG-335936).

We present a large, homogeneous catalogue of molecular clouds within 4 kpc from the Sun at low Galactic latitudes ($|b|$ $, Comment: 11 pages, 7 figures, 2 tables, MNRAS in press

Sagittarius serpentarius (J. F. Miller, 1779) LITERATURE. — Green & Sayer (1979); Thonnérieux et al. (1989); Dowsett (1993); Borrow & Demey (2001, 2014); Portier (2002c); Thiollay (2006a, b); Balanca et al. (2007); Sinclair & Ryan (2010); Dowsett et al. (2013); ABC (2020). FIELD DATA. — GBIF; WABD. STATUS. — Resident., Published as part of Boano, Giovanni, Belemsobgo, Urbain, Silvano, Fabrizio, Hema, Emmanuel M., Belemsobgo, Aristide, Dimobe, Kangbéni & Pavia, Marco, 2022, An annotated checklist of the birds of Burkina Faso, pp. 27-107 in Zoosystema 44 (2) on page 55, DOI: 10.5252/zoosystema2022v44a2, http://zenodo.org/record/5999691, {"references":["GREEN A. A. & SAYER J. A. 1979. - The birds of Pendjari and Arly National Parks (Benin and Upper Volta). Malimbus 1: 14 - 28.","THONNERIEUX Y., WALSH J. F. & BORTOLI L. 1989. - L'avifaune de la ville de Ouagadougou et ses environs (Burkina Faso). Malimbus 11: 7 - 39.","DOWSETT R. J. 1993. - Afrotropical avifaunas: annotated country checklists, in DOWSETT R. J. & DOWSETT- LEMAIRE F. (eds). A Contribution to the Distribution and Taxonomy of Afrotropical and Malagasy birds Tauraco Research Report 5, Tauraco Press, Liege: 1 - 322.","BORROW N. & DEMEY R. 2001. - Birds of Western Africa. Christopher Helm, London, 832 p.","BORROW N. & DEMEY R. 2014. - Field Guide of the Birds of Western Africa. II edition. Christopher Helm, London, 592 p.","PORTIER B. 2002 c. - Liste de l'avifaune du Ranch de Gibier de Nazinga. http: // environnement. wallonie. be / projet _ nazinga / PDF / Liste _ oiseaux _ Nazinga. pdf.","THIOLLAY J. - M. 2006 a. - Large Bird Declines with Increasing Human Pressure in Savanna Woodlands (Burkina Faso). Biodiversity and Conservation 15: 2085 - 2108. https: // doi. org / 10.1007 / s 10531 - 004 - 6684 - 3","BALANCA G., CORNELIS D. & WILSON R. 2007. - Les oiseaux du complexe WAP. ECOPAS. Cirad, Montpellier.","SINCLAIR I. & RYAN P. 2010. - Birds of Africa south of the Sahara. II edition. Struik Nature, Cape Town, 768 p.","DOWSETT R. J., ATKINSON P. W. & CADDICK J. A. 2013. - Checklist of the birds of Burkina Faso: 1 - 12. https: // www. africanbirdclub. org / [accessed 14 October 2013].","ABC 2020. - Burkina Faso. News. Available from https: // www. africanbirdclub. org / countries / burkina - faso [accessed 01 Nov. 2020]"]}

The Fermi Bubbles are giant, γ-ray emitting lobes emanating from the nucleus of the Milky Way [1, 2] discovered in ∼1-100 GeV data collected by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope [3]. Previous work [4] has revealed substructure within the Fermi Bubbles that has been interpreted as a signature of collimated outflows from the Galaxy’s super-massive black hole. Here we show that much of the γ-ray emission associated to the brightest region of substructure – the so-called cocoon – is actually due to the Sagittarius dwarf spheroidal (Sgr dSph) galaxy. This large Milky Way satellite is viewed through the Fermi Bubbles from the position of the Solar System. As a tidally and ram-pressure stripped remnant, the Sgr dSph has no on-going star formation, but we demonstrate that its γ-ray signal is naturally explained by inverse Compton scattering of cosmic microwave back-ground photons by high-energy electron-positron pairs injected by the dwarf’s millisecond pulsar (MSP) population, combined with these objects’ magnetospheric emission. This finding suggests that MSPs likely produce significant γ-ray emission amongst old stellar populations, potentially confounding indirect dark matter searches in regions such as the Galactic Centre, the Andromeda galaxy, and other massive Milky Way dwarf spheroidals.

We study the globular clusters (GCs) in the spiral galaxy NGC~5907 well-known for its spectacular stellar stream -- to better understand its origin. Using wide-field Subaru/Suprime-Cam $gri$ images and deep Keck/DEIMOS multi-object spectroscopy, we identify and obtain the kinematics of several GCs superimposed on the stellar stream and the galaxy disk. We estimate the total number of globular clusters in NGC 5907 to be $154\pm44$, with a specific frequency of $0.73\pm0.21$. Our analysis also reveals a significant, new population of young star cluster candidates found mostly along the outskirts of the stellar disk. Using the properties of the stream GCs, we estimate that the disrupted galaxy has a stellar mass similar to the Sagittarius dwarf galaxy accreted by the Milky Way, i.e. $\sim10^8~M_\odot$., Comment: 9 pages, 9 figures, catalog of GCs is available in online version

N-body simulations of the interaction between the Sagittarius dwarf galaxy and the Milky Way are performed to study whether it is possible to reproduce both the bifurcations in the tidal streams and the physical properties of Sagittarius. Both galaxies are simulated as sets of particles (live potentials). The initial structures are formed using GALIC and the gravitational interaction between these galaxies is simulated with gadget-2. Sagittarius initially is simulated as a rotating disk-type galaxy with two components: dark matter halo and stellar disk and the Milky Way is a disk galaxy with three components: dark matter halo, stellar disk and central spheroid. Several angles between the orbital angular momentum and the disc angular momentum in the range 180o ≤ θ ≤ 0o were simulated, showing that, although the position and physical properties of Sagittarius are not reproduced entirely by the remnant, the bifurcations appear clearly when 180o ≤ θ < 90o.

We present the S-Band Polarization All Sky Survey (S-PASS), a survey of polarized radio emission over the southern sky at Dec~$< -1^\circ$ taken with the Parkes radio telescope at 2.3~GHz. The main aim was to observe at a frequency high enough to avoid strong depolarization at intermediate Galactic latitudes (still present at 1.4 GHz) to study Galactic magnetism, but low enough to retain ample Signal-to-Noise ratio (S/N) at high latitudes for extragalactic and cosmological science. We developed a new scanning strategy based on long azimuth scans, and a corresponding map-making procedure to make recovery of the overall mean signal of Stokes $Q$ and $U$ possible, a long-standing problem with polarization observations. We describe the scanning strategy, map-making procedure, and validation tests. The overall mean signal is recovered with a precision better than 0.5\%. The maps have a mean sensitivity of 0.81 mK on beam--size scales and show clear polarized signals, typically to within a few degrees of the Galactic plane, with ample S/N everywhere (the typical signal in low emission regions is 13 mK, and 98.6\% of the pixels have S/N $> 3$). The largest depolarization areas are in the inner Galaxy, associated with the Sagittarius Arm. We have also computed a Rotation Measure map combining S-PASS with archival data from the WMAP and Planck experiments. A Stokes $I$ map has been generated, with a sensitivity limited to the confusion level of 9 mK., Accepted for publication on MNRAS. Maps are available for download at the website indicated in the manuscript

The new cardinalfish Gymnapogon sagittarius sp. nov. is described on the basis of eight specimens from Vietnam, Malaysia and the Andaman Sea. The new species is most similar to the Red Sea species G. melanogaster Gon and Golani 2002 (known only from two specimens) in having 9 soft dorsal-fin rays, 8 soft anal-fin rays, and 13 total gill rakers, but differs in having 16 pectoral-fin rays (vs. 14 or 15 rays in G. melanogaster), body depth 12.0–15.1% of SL (mean 14.2%) (vs. 21.7–24.0%), eye diameter 5.2–6.1% (5.6%) (vs. 10.0–11.6%), interorbital width 3.7–4.4% (4.0%) (vs. 5.7–8.2%), and longest pelvic-fin soft ray length 12.0–15.6% (14.1%) (vs. 25.4–34.3%).

In this fourth article on weighing the Galactic disk using the shape of the phase-space spiral, we have tested our method on a billion particle three-dimensional N-body simulation, comprised of a Milky Way like host galaxy and a merging dwarf satellite. The main purpose of this work was to test the validity of our model’s fundamental assumptions that the spiral inhabits a locally static and vertically separable gravitational potential. These assumptions might be compromised in the complex kinematic system of a disturbed three-dimensional disk galaxy; in fact, the statistical uncertainty and any potential biases related to these assumptions are expected to be amplified for this simulation, which differs from the Milky Way in that it is more strongly perturbed and has a phase-space spiral that inhabits higher vertical energies. We constructed 44 separate data samples from different spatial locations in the simulated host galaxy. Our method produced accurate results for the vertical gravitational potential of these 44 data samples, with an unbiased distribution of errors with a standard deviation of 7%. We also tested our method under severe and unknown spatially dependent selection effects, also with robust results; this sets it apart from traditional dynamical mass measurements that are based on the assumption of a steady state and which are highly sensitive to unknown or poorly modelled incompleteness. Hence, we will be able to make localised mass measurements of distant regions in the Milky Way disk, which would otherwise be compromised by complex and poorly understood selection effects., AW acknowledges support from the Carlsberg Foundation via a Semper Ardens grant (CF15-0384). JH is supported by a Flatiron Research Fellowship at the Flatiron institute, which is supported by the Simons Foundation. CL acknowledges funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 852839). GM acknowledges funding from the Agence Nationale de la Recherche (ANR project ANR-18-CE31-0006 and ANR-19-CE31-0017) and from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 834148). This work made use of an HPC facility funded by a grant from VILLUM FONDEN (projectnumber 16599). This research utilised the following open-source Python packages: MATPLOTLIB (Hunter 2007), NUMPY (Harris et al. 2020), SCIPY (Virtanen et al. 2020), PANDAS (McKinney et al. 2010), TENSORFLOW (Abadi et al. 2015).

We report the discovery of 34 new open clusters and candidates as a result of a systematic search carried out in 200 adjacent fields of 1x1 square degrees area projected towards the Galactic bulge, using Gaia DR2 data. The objects were identified and characterized by a joint analysis of their photometric, kinematic and spatial distribution, which has been consistently used and proved to be effective in our previous works. The discoveries were validated by cross-referencing the objects position and astrometric parameters with the available literature. Besides their coordinates and astrometric parameters, we also provide sizes, ages, distances and reddening for the discovered objects. In particular, 32 clusters are closer than 2 kpc from the Sun, which represents an increment of nearly 39% of objects with astrophysical parameters determined in the nearby inner disk. Although these objects fill an important gap in the open clusters distribution along the Sagittarius arm, this arm, traced by known clusters, appears to be interrupted, which may be an artifact due to the incompleteness of the cluster census., Comment: 5 pages, 4 figures, Accepted in MNRAS Jan-2021

Interactions between users and videos are the major data source of performing video recommendation. Despite lots of existing recommendation methods, user behaviors on videos, which imply the complex relations between users and videos, are still far from being fully explored. In the paper, we present a model named Sagittarius. Sagittarius adopts a graph convolutional neural network to capture the influence between users and videos. In particular, Sagittarius differentiates between different user behaviors by weighting and fuses the semantics of user behaviors into the embeddings of users and videos. Moreover, Sagittarius combines multiple optimization objectives to learn user and video embeddings and then achieves the video recommendation by the learned user and video embeddings. The experimental results on multiple datasets show that Sagittarius outperforms several state-of-the-art models in terms of recall, unique recall and NDCG.

[Context] In spiral galaxies, star formation tends to trace features of the spiral pattern, including arms, spurs, feathers, and branches. However, in our own Milky Way, it has been challenging to connect individual star-forming regions to their larger Galactic environment owing to our perspective from within the disk. One feature in nearly all modern models of the Milky Way is the Sagittarius Arm, located inward of the Sun with a pitch angle of ∼12°. [Aims] We map the 3D locations and velocities of star-forming regions in a segment of the Sagittarius Arm using young stellar objects (YSOs) from the Spitzer/IRAC Candidate YSO (SPICY) catalog to compare their distribution to models of the arm. [Methods] Distances and velocities for these objects are derived from Gaia EDR3 astrometry and molecular line surveys. We infer parallaxes and proper motions for spatially clustered groups of YSOs and estimate their radial velocities from the velocities of spatially associated molecular clouds. [Results] We identify 25 star-forming regions in the Galactic longitude range ∼ 4. ° 0-18. ° 5 arranged in a narrow, ∼1 kpc long linear structure with a high pitch angle of ψ = 56° and a high aspect ratio of ∼7:1. This structure includes massive star-forming regions such as M8, M16, M17, and M20. The motions in the structure are remarkably coherent, with velocities in the direction of Galactic rotation of |Vφ|≈240 ± 3 km s-1 (slightly higher than average) and slight drifts inward (VR ≈ -4.3 km s-1) and in the negative Z direction (VZ ≈ -2.9 km s-1). The rotational shear experienced by the structure is Δω = 4.6 km s-1 kpc-1. [Conclusions] The observed 56° pitch angle is remarkably high for a segment of the Sagittarius Arm. We discuss possible interpretations of this feature as a substructure within the lower pitch angle Sagittarius Arm, as a spur, or as an isolated structure., This work is based in part on archival data obtained with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. M.A.K. was partially supported by Chandra grant GO9-20002X. R.A.B. would like to acknowledge support from NASA grant NNX17AJ27G. AKM acknowledges the support from the Portuguese Fundação para a Ciência e a Tecnologia (FCT) grants UID/FIS/00099/2019, PTDC/FIS-AST/31546/2017.

Here we show that precise Gaia EDR3 proper motions have provided robust estimates of 3D velocities, angular momentum and total energy for 40 Milky Way dwarfs. The results are statistically robust and are independent of the Milky Way mass profile. Dwarfs do not behave like long-lived satellites of the Milky Way because of their excessively large velocities, angular momenta, and total energies. Comparing them to other MW halo population, we find that many are at first passage, $\le$ 2 Gyr ago, i.e., more recently than the passage of Sagittarius, $\sim$ 4-5 Gyr ago. We suggest that this is in agreement with the stellar populations of all dwarfs, for which we find that a small fraction of young stars cannot be excluded. We also find that dwarf radial velocities contribute too little to their kinetic energy when compared to satellite systems with motions only regulated by gravity, and some other mechanism must be at work such as ram pressure. The latter may have preferentially reduced radial velocities when dwarf progenitors entered the halo until they lost their gas. It could also explain why most dwarfs lie near their pericenter. We also discover a novel large scale structure perpendicular to the Milky Way disk, which is made by 20% of dwarfs orbiting or counter orbiting with the Sagittarius dwarf., Comment: Subtitle: "Are Milky Way dwarfs at first infall?"; 17 pages, 12 Figures, 1 Table, The Astrophysical Journal in press, 2021

We present a new method for inferring the gravitational potential of the Galactic disk, using the time-varying structure of a phase-space spiral in the $(z,w)$-plane (where $z$ and $w$ represent vertical position and vertical velocity). Our method of inference extracts information from the shape of the spiral and disregards the bulk density distribution that is usually used to perform dynamical mass measurements. In this manner, it is complementary to traditional methods that are based on the assumption of a steady state. Our method consists of fitting an analytical model for the phase-space spiral to data, where the spiral is seen as a perturbation of the stellar number density in the $(z,w)$-plane. We tested our method on one-dimensional simulations, which were initiated in a steady state and then perturbed by an external force similar to that of a passing satellite. We were able to retrieve the true gravitational potentials of the simulations with high accuracy. The gravitational potential at 400-500 parsec distances from the disk mid-plane was inferred with an error of only a few percent. This is the first paper of a series in which we plan to test and refine our method on more complex simulations, as well as apply our method to Gaia data., Comment: 16 pages, 12 figures

We have measured trigonometric parallaxes for four water masers associated with distant massive young stars in the inner regions of the Galaxy using the VLBA as part of the BeSSeL Survey. G026.50$+$0.28. is located at the near end of the Galactic bar, perhaps at the origin of the Norma spiral arm. G020.77$-$0.05 is in the Galactic Center region and is likely associated with a far-side extension of the Scutum arm. G019.60$-$0.23 and G020.08$-$0.13 are likely associated and lie well past the Galactic Center. These sources appear to be in the Sagittarius spiral arm, but an association with the Perseus arm cannot be ruled out., 17 pages, 3 figures, 5 tables

The taxonomy of Peruvian water beetles in the genus Hydrochus Leach, 1817 is presented. The known fauna now consists of 22 species, 14 of which are described as new species. The new species are diagnosed, and high-resolution images of the habitus and male genitalia of each species are given. The following new species are described: H. alternatus n. sp., H. astrictus n. sp., H. bisinuatus n. sp., H. bucapitus n. sp., H. cracentis n. sp., H. dualis n. sp., H. lescheni n. sp., H. obliquus n. sp., H. parvicollis n. sp., H. spinosus n. sp., H. subovatus n. sp., H. tambopaticus n. sp., H. tripartitus n. sp., and H. uniformis n. sp. New locality data are provided for H. argutus Knisch 1921, H. bituberculatus Perkins 2019, H. coeneni Makhan 1992, H. leei Perkins 2019, H. lobatus Perkins 2019, H. obscurus Sharp 1882, H. richteri Bruch 1915, and H. sagittarius Perkins 2019. Images of the habitus and male genitalia of H. coeneni Makhan 1992 are also given.

We assemble a catalogue of candidate Sagittarius stream members with 5d and 6d phase-space information, using astrometric data from Gaia DR2, distances estimated from RR Lyrae stars, and line-of-sight velocities from various spectroscopic surveys. We find a clear misalignment between the stream track and the direction of the reflex-corrected proper motions in the leading arm of the stream, which we interpret as a signature of a time-dependent perturbation of the gravitational potential. A likely cause of this perturbation is the recent passage of the most massive Milky Way satellite - the Large Magellanic Cloud (LMC). We develop novel methods for simulating the Sagittarius stream in the presence of the LMC, using specially tailored N-body simulations and a flexible parametrization of the Milky Way halo density profile. We find that while models without the LMC can fit most stream features rather well, they fail to reproduce the misalignment and overestimate the distance to the leading arm apocentre. On the other hand, models with an LMC mass in the range (1.3+-0.3)x10^11 Msun rectify these deficiencies. We demonstrate that the stream can not be modelled adequately in a static Milky Way. Instead, our Galaxy is required to lurch toward the massive in-falling Cloud, giving the Sgr stream its peculiar shape and kinematics. By exploring the parameter space of Milky Way potentials, we determine the enclosed mass within 100 kpc to be (5.6+-0.4)x10^11 Msun, and the virial mass to be (9.0+-1.3)x10^11 Msun, and find tentative evidence for a radially-varying shape and orientation of the Galactic halo., matches published version

Studies of the early chemical evolution of some larger dwarf galaxies ( $>10^7$ solar masses) are limited by the small number of stars known at low metallicities in these systems. Here we present metallicities and carbon abundances for eighteen stars with metallicities between $-3.08 \le \text{[Fe/H]} \le -1.47$ in the Sagittarius dwarf spheroidal galaxy, using medium-resolution spectra from the MagE spectrograph on the Magellan-Baade Telescope. This sample more than doubles the number of known very metal-poor stars ([Fe/H] $\leq -2.0$) in the Sagittarius dwarf galaxy, and identifies one of the first known extremely metal-poor stars ([Fe/H] $\leq -3.0$) in the system. These stars were identified as likely metal-poor members of Sagittarius using public, metallicity-sensitive photometry from SkyMapper DR1.1 and proper motion data from Gaia DR2, demonstrating that this dearth of metal-poor stars in some dwarf galaxies can be addressed with targeted searches using public data. We find that none of the stars in our sample are enhanced in carbon, in contrast to the relative prevalence of such stars in the Milky Way halo. Subsequent high-resolution spectroscopy of these stars would be key in detailing the early chemical evolution of the system., Comment: 13 pages, 7 figures, 3 tables; Accepted for publication in ApJ

We report on the discovery and chemical abundance analysis of the first CEMP-r/s star detected in the Sagittarius dwarf Spheroidal Galaxy, by means of UVES high resolution spectra. The star, found in the outskirts of Sgr dSph, along the main body major axis, is a moderately metal poor giant (T$_{eff}$=4753 K, log g=1.75, [Fe/H]=-1.55), with [C/Fe]=1.13 placing it in the so-called "high-carbon band", and strong s-process and r-process enrichment ([Ba/Fe]=1.4, [Eu/Fe]=1.01). Abundances of 29 elements from C to Dy were obtained. The chemical pattern appears to be best fitted by a scenario where an r-process pollution event pre-enriched the material out of which the star was born as secondary in a binary system whose primary evolved through the AGB phase, providing C and s-process enrichment., 10 pages, 9 figures, Accepted by Astronomy and Astrophysics

This study extends to the structure of the Galaxy. Our main goal is to focus on the first spiral arm beyond the Perseus arm, often called the Cygnus arm or the Outer Norma arm, by appraising the distributions of the masers near the Cygnus arm. The method is to employ masers whose trigonometric distances were measured with accuracy. The maser data come from published literature, having been obtained via the existing networks (US VLBA, the Japanese VERA, the European VLBI, and the Australian LBA). The new results for Cygnus are split in two groups: those located near a recent CO fitted global model spiral arm, and those congregating within an interarm island located halfway between the Perseus arm and the Cygnus arm. Next, we compare this island with other similar interarm objects near other spiral arms. Thus we delineate an interarm island (6 x 2 kpc) located between the two long spiral arms (Cygnus and Perseus arms); this is reminiscent of the small Local Orion arm (4 x 2 kpc) found earlier between the Perseus and Sagittarius arms, and of the old Loop (2 x 0.5 kpc) found earlier between the Sagittarius and Scutum arms. Various arm models are compared, based on observational data (masers, HII regions, HI gas, young stars, CO gas)., 26 pages; 4 figures; 3 tables; 71 references; 1 equation. Accepted for publication

We reconsider the case for the association of Galactic globular clusters (GCs) to the tidal stream of the Sagittarius dwarf spheroidal galaxy (Sgr dSph), using Gaia DR2 data. We use RR Lyrae to trace the stream in 6D and we select clusters matching the observed stream in position and velocity. In addition to the clusters residing in the main body of the galaxy (M 54, Ter 8, Ter 7, Arp 2) we confirm the membership of Pal 12 and Whiting 1 to the portion of the trailing arm populated by stars lost during recent perigalactic passages. NGC 2419, NGC 5634 and NGC 4147 are very interesting candidates, possibly associated to more ancient wraps of the stream. We note that all these clusters, with the exception of M 54, that lies within the stellar nucleus of the galaxy, are found in the trailing arm of the stream. The selected clusters are fully consistent with the [Fe/H] vs. [Mg/Fe], [Ca/Fe] patterns and the age-metallicity relation displayed by field stars in the main body of Sgr dSph., Comment: Accepted for publication by Astronomy & Astrophysics. Latex, 9 pages, 7 color figures

The Pristine survey uses narrow-band photometry to derive precise metallicities down to the extremely metal-poor regime ([Fe/H] < -3), and currently consists of over 4 million FGK-type stars over a sky area of $\sim 2~500\, \mathrm{deg}^2$. We focus our analysis on a subsample of $\sim 80~000$ main sequence turnoff stars with heliocentric distances between 6 and 20 kpc, which we take to be a representative sample of the inner halo. The resulting metallicity distribution function (MDF) has a peak at [Fe/H] = -1.6, and a slope of $��$(LogN)/$��[Fe/H] = 1.0 \pm 0.1$ in the metallicity range of -3.4 < [Fe/H] < -2.5. This agrees well with a simple closed-box chemical enrichment model in this range, but is shallower than previous spectroscopic MDFs presented in the literature, suggesting that there may be a larger proportion of metal-poor stars in the inner halo than previously reported. We identify the Monoceros/TriAnd/ACS/EBS/A13 structure in metallicity space in a low latitude field in the anticenter direction, and also discuss the possibility that the inner halo is dominated by a single, large merger event, but cannot strongly support or refute this idea with the current data. Finally, based on the MDF of field stars, we estimate the number of expected metal-poor globular clusters in the Milky Way halo to be 5.4 for [Fe/H] < -2.5 and 1.5 for [Fe/H] < -3, suggesting that the lack of low metallicity globular clusters in the Milky Way is not due simply to statistical undersampling., 17 pages, 12 figures, 5 tables, accepted for publication in MNRAS

The Milky Way is one of the very few spiral galaxies known to host large-scale magnetic field reversals. The existence of the field reversal in the first Galactic quadrant near the Sagittarius spiral arm has been well established, yet poorly characterised due to the insufficient number of reliable Faraday depths (FDs) from extragalactic radio sources (EGSs) through this reversal region. We have therefore performed broadband (1-2 GHz) spectro-polarimetric observations with the Karl G. Jansky Very Large Array (VLA) to determine the FD values of 194 EGSs in the Galactic longitude range of $20^\circ$-$52^\circ$ within $\pm 5^\circ$ from the Galactic mid-plane, covering the Sagittarius arm tangent. This factor of five increase in the EGS FD density has led to the discovery of a disparity in FD values across the Galactic mid-plane in the Galactic longitude range of $40^\circ$-$52^\circ$. Combined with existing pulsar FD measurements, we suggest that the Sagittarius arm can host an odd-parity disk field. We further compared our newly derived EGS FDs with the predictions of three major Galactic magnetic field models, and concluded that none of them can adequately reproduce our observational results. This has led to our development of new, improved models of the Milky Way disk magnetic field that will serve as an important step towards major future improvements in Galactic magnetic field models., Comment: 21 pages main text + 23 pages supplement; MNRAS accepted

A number of the massive clusters in the halo, bulge and disc of the Galaxy are not genuine globular clusters (GCs), but instead are different beasts altogether. They are the remnant nuclear star clusters (NSCs) of ancient galaxies since accreted by the Milky Way. While some clusters are readily identifiable as NSCs, and can be readily traced back to their host galaxy (e.g., M54 and the Sagittarius Dwarf galaxy) others have proven more elusive. Here we combine a number of independent constraints, focusing on their internal abundances and overall kinematics, to find NSCs accreted by the Galaxy and trace them to their accretion event. We find that the true NSCs accreted by the Galaxy are: M54 from the Sagittarius Dwarf, $\omega$ Centari from Gaia-Enceladus/Sausage, NGC 6273 from Kraken and (potentially) NGC 6934 from the Helmi Streams. These NSCs are prime candidates for searches of intermediate mass black holes (BHs) within star clusters, given the common occurrence of galaxies hosting both NSCs and central massive BHs. No NSC appears to be associated with Sequoia or other minor accretion events. Other claimed NSCs are shown not to be such. We also discuss the peculiar case of Terzan 5, which may represent a unique case of a cluster-cluster merger., Comment: 11 pages, accepted for publication in MNRAS

Nebular spectroscopy is a valuable tool for assessing the production of heavy elements by slow neutron(n)-capture nucleosynthesis (the s-process). Several transitions of n-capture elements have been identified in planetary nebulae (PNe) in the last few years, with the aid of sensitive high-resolution near-infrared spectrometers. Combined with optical spectroscopy, the newly discovered near-infrared lines enable more accurate abundance determinations than previously possible, and provide access to elements that had not previously been studied in PNe or their progenitors. Neutron-capture elements have also been detected in PNe in the Sagittarius Dwarf galaxy and in the Magellanic Clouds. In this brief review, I discuss developments in observational studies of s-process enrichments in PNe, with an emphasis on the last five years, and note some open questions and preliminary trends., Comment: 9 pages, one figure, to appear in Proceedings of WORKPLANS II (Lorentz Center Workshop, Leiden, the Netherlands, December 2019), edited by T. Ueta, accepted for publication by Galaxies

Research into the etymology of various names for the Secretarybird Sagittarius serpentarius reveals a comedy of errors from Vosmaer, his French translator, Buffon, Sonnerat, and Miller to Fry. The research suggests that the name Sagittarius resulted from a misunderstanding in Holland and that Buffon introduced the name Messager in error. The Arabic root proposed for the name by Fry in 1977 is historically implausible and linguistically illogical.

Low metallicity massive stars hold the key to interpret numerous processes in the past Universe including re-ionization, starburst galaxies, high-redshift supernovae and GRBs. The Sagittarius Dwarf Irregular Galaxy (SagDIG, 12+log(O/H)=7.37) represents an important landmark in the quest for analogues accessible with 10-m class telescopes. This paper presents low-resolution spectroscopy executed with the Gran Telescopio Canarias that confirms that SagDIG hosts massive stars. The observations unveiled three OBA-type stars and one red supergiant candidate. Pending confirmation from high-resolution follow-up studies, these could be the most metal-poor massive stars of the Local Group., Comment: Accepted for publication at MNRAS-Letters

The Chinese species of the genus Nakaharanus Ishihara are reviewed, and a new species Nakaharanus lii sp. nov. is described and illustrated. Nakaharanus sagittarius Kwon & Lee, 1979 is recorded from China for the first time. Two keys based on the male genitalia and female seventh sternum are given to distinguish Chinese species of this genus. The type specimens of the new species are deposited in the Institute of Entomology, Guizhou University, Guiyang, China (GUGC).

We present new photometry and analysis of the twelve variable stars (nine RR Lyrae, three SX Phoenicis) belonging to the Sagittarius globular cluster Arp 2. Of the nine RR Lyrae stars in the cluster, eight are RRab and one is RRc. From the RRab stars, we determined a mean period of $\langle P_{ab}\rangle=0.581\pm0.047$ days, where the error is the standard error of the mean. This places Arp 2 at the border between the Oosterhoff I and Oosterhoff-Int clusters. Using the $V$-band data from the RR Lyrae stars, a distance modulus of $(m-M)_0=17.24\pm0.17$ was determined. From the $I$-band data, we found $(m-M)_0=17.34\pm0.07$. We also used the SX Phoenicis variables to determine a distance modulus of $(m-M)_0=17.27\pm0.04$. Color excesses were determined from the RR Lyrae light curves using both the ($B-V$) and ($V-I$) colors. The mean reddening values were in line with or were a little higher than those found in the literature. Both methods indicated star-to-star variability in the reddening toward Arp 2. Of the nine RR Lyrae stars, seven were flagged as variables by Gaia, with three having periods determined. We used the Gaia data to investigate the membership of the seven Gaia RR Lyrae. Although Arp 2 is too distant for reliable Gaia parallax, the current data do not exclude any of the variables discussed in this paper from being members of Arp 2., 22 pages, 6 figures, accepted for publication in PASP

We estimate the mass of the inner ($1.9$) with 99\% probability. Our preferred model reproduces well the observed phase-space distribution of globular clusters and has a disc component that closely resembles that of the Galactic thick disc. The halo component follows a power-law density profile $��\propto r^{-3.3}$, has a mean rotational velocity of $V_{\rm rot}\simeq -14\,\rm km\,s^{-1}$ at 20 kpc, and has a mildly radially biased velocity distribution ($��\simeq 0.2 \pm 0.07$, fairly constant outside 15 kpc). We also find that our distinction between disc and halo clusters resembles, although not fully, the observed distinction in metal-rich ([Fe/H]$>-0.8$) and metal-poor ([Fe/H]$\leq-0.8$) cluster populations., Accepted for publication in A&A