Kinematics with Gaia DR2: the force of a dwarf

We use Gaia DR2 astrometric and line-of-sight velocity information combined with two sets of distances obtained with a Bayesian inference method to study the 3D velocity distribution in the Milky Way disc. We search for variations in all Galactocentric cylindrical velocity components (Vϕ, VR, and Vz) with Galactic radius, azimuth, and distance from the disc mid-plane. We confirm recent work showing that bulk vertical motions in the R–z plane are consistent with a combination of breathing and bending modes. In the x–y plane, we show that, although the amplitudes change, the structure produced by these modes is mostly invariant as a function of distance from the plane. Comparing to two different Galactic disc models, we demonstrate that the observed patterns can drastically change in short time intervals, showing the complexity of understanding the origin of vertical perturbations. A strong radial VR gradient was identified in the inner disc, transitioning smoothly from 16 km s−1 kpc−1 at an azimuth of 30° < ϕ < 45° ahead of the Sun-Galactic centre line to −16 km s−1 kpc−1 at an azimuth of −45° < ϕ < −30° lagging the solar azimuth. We use a simulation with no significant recent mergers to show that exactly the opposite trend is expected from a barred potential, but overestimated distances can flip this trend to match the data. Alternatively, using an N-body simulation of the Sagittarius dwarf–Milky Way interaction, we demonstrate that a major recent perturbation is necessary to reproduce the observations. Such an impact may have strongly perturbed the existing bar or even triggered its formation in the last 1–2 Gyr

Abundance analysis of APOGEE spectra for 58 metal-poor stars from the bulge spheroid

The central part of the Galaxy hosts a multitude of stellar populations, including the spheroidal bulge stars, stars moved to the bulge through secular evolution of the bar, inner halo, inner thick disc, inner thin disc, as well as debris from past accretion events. We identified a sample of 58 candidate stars belonging to the stellar population of the spheroidal bulge, and analyse their abundances. The present calculations of Mg, Ca, and Si lines are in agreement with the ASPCAP abundances, whereas abundances of C, N, O, and Ce are re-examined. We find normal α-element enhancements in oxygen, similar to magnesium, Si, and Ca abundances, which are typical of other bulge stars surveyed in the optical in Baade’s Window. The enhancement of [O/Fe] in these stars suggests that they do not belong to accreted debris. No spread in N abundances is found, and none of the sample stars is N-rich, indicating that these stars are not second generation stars originated in globular clusters. Ce instead is enhanced in the sample stars, which points to an s-process origin such as due to enrichment from early generations of massive fast rotating stars, the so-called spinstars

Representações sociais de mulheres sobre a amamentação: teste de associação livre de idéias acerca da interrupção precoce do aleitamento materno exclusivo Representaciones Sociales de Mujeres Sobre el Amamantamiento: Prueba de Asociación Libre de Ideas Acerca de la Interrupción Precoz del Amamantamiento Materno Exclusivo Social Representations of Women on Breastfeeding: Free Association of Ideas Test About the Early Interruption of the Exclusive Maternal Breastfeeding

A interrupção prematura do aleitamento materno exclusivo (AME) constitui um problema com características biológicas, psicológicas e socioculturais. Este trabalho visa descrever as representações sociais da amamentação para mulheres que interromperam precocemente o AME. Foram entrevistadas 30 mulheres (15 trabalhavam no lar - Ntr, 15 trabalhavam fora - Tr) em aleitamento misto atendidas no Programa Saúde da Família do município de Resende (RJ). Os dados foram coletados de agosto a outubro de 2005 através do Teste de Associação Livre de Idéias, visando emergir associações relativas às palavras exploradas ao nível dos estereótipos sociais, seguido da análise de conteúdo de Bardin. Os dados mostraram elevada freqüência da categoria "prazer, amor e carinho", demonstrando o reconhecimento da importância do aleitamento e do leite humano. "Saúde do bebê" teve maior expressividade no grupo NTr, sugerindo que essas mulheres ancoraram a amamentação no processo saúde-doença. Concluiu-se que as mulheres reconhecem a importância de amamentar, mas não de sua exclusividade até o sexto mês.<br>La interrupción prematura del amamantar materno exclusivo (AME) constituye un problema con características biológicas, psicológicas y socioculturales. El presente trabajo pretende describir las representaciones sociales sobre el amamantar por mujeres que interrumpen de manera precoz el AME. Entrevistamos 30 mujeres (15 trabajaban en hogar - Ntr, 15 trabajaban fuera de la casa - Tr) en amamantar mezclado asistidas en el PSF del municipio de Resende (RJ). Los datos fueron coleccionados de agosto a septiembre de 2005, por medio de una Prueba de Libre Asociación de Ideas, pretendiendo resultar asociaciones relativas a las palabras exploradas al nivel de los estereotipos sociales, al que se siguió el análisis del contenido de Bardin. Los datos apuntaron señales de elevada frecuencia de categoría "placer, amor y cariño", que demuestran el reconocimiento de la importancia del amamantar materno y de la leche humana. "Salud del bebé" tuvo mayor expresividad en el grupo NTr, sugerido que esas mujeres anclaron el amamantar en el proceso salud-enfermedad. Concluyese que las mujeres reconocen la importancia de amamantar, pero no de su exclusivismo hasta el sexto mes de vida.<br>The early interruption of exclusive breastfeeding (EB) constitutes a problem with biological, psychological and sociocultural characteristics. This paper aims to describe the social representations of women who have early weaned EB. We have interviewed 30 women (15 were housewives HM, 15 were working mothers WM) in mixed assited nursering in the Family Health Program in the city of Resende (RJ). From August to September 2005, we have collected data through a Free Association of Ideas test, aiming to emerge associations related to the words exploited at the level of social stereotypes, which was followed by the Bardin's content analyses. The data have shown high frequency of the category "pleasure, love and affection", showing the recognition of the importance of breastfeeding and of human milk. "Baby's health" has been more expressive in the HM group, suggesting that these women anchored breastfeeding in the health-sickness process. In conclusion, our women recognize the importance of breastfeeding but not its exclusiveness up to the sixth month of age

The RAdial Velocity Experiment (RAVE): Parameterisation of RAVE spectra based on convolutional neural networks

Context. Data-driven methods play an increasingly important role in the field of astrophysics. In the context of large spectroscopic surveys of stars, data-driven methods are key in deducing physical parameters for millions of spectra in a short time. Convolutional neural networks (CNNs) enable us to connect observables (e.g. spectra, stellar magnitudes) to physical properties (atmospheric parameters, chemical abundances, or labels in general). / Aims. We test whether it is possible to transfer the labels derived from a high-resolution stellar survey to intermediate-resolution spectra of another survey by using a CNN. / Methods. We trained a CNN, adopting stellar atmospheric parameters and chemical abundances from APOGEE DR16 (resolution R = 22 500) data as training set labels. As input, we used parts of the intermediate-resolution RAVE DR6 spectra (R ∼ 7500) overlapping with the APOGEE DR16 data as well as broad-band ALL_WISE and 2MASS photometry, together with Gaia DR2 photometry and parallaxes. / Results. We derived precise atmospheric parameters Teff, log(g), and [M/H], along with the chemical abundances of [Fe/H], [α/M], [Mg/Fe], [Si/Fe], [Al/Fe], and [Ni/Fe] for 420 165 RAVE spectra. The precision typically amounts to 60 K in Teff, 0.06 in log(g) and 0.02−0.04 dex for individual chemical abundances. Incorporating photometry and astrometry as additional constraints substantially improves the results in terms of the accuracy and precision of the derived labels, as long as we operate in those parts of the parameter space that are well-covered by the training sample. Scientific validation confirms the robustness of the CNN results. We provide a catalogue of CNN-trained atmospheric parameters and abundances along with their uncertainties for 420 165 stars in the RAVE survey. / Conclusions. CNN-based methods provide a powerful way to combine spectroscopic, photometric, and astrometric data without the need to apply any priors in the form of stellar evolutionary models. The developed procedure can extend the scientific output of RAVE spectra beyond DR6 to ongoing and planned surveys such as Gaia RVS, 4MOST, and WEAVE. We call on the community to place a particular collective emphasis and on efforts to create unbiased training samples for such future spectroscopic surveys

Physical properties of star clusters in the outer LMC as observed by the Dark Energy Survey

The Large Magellanic Cloud (LMC) harbors a rich and diverse system of star clusters, whose ages, chemical abundances, and positions provide information about the LMC history of star formation. We use Science Verification imaging data from the Dark Energy Survey to increase the census of known star clusters in the outer LMC and to derive physical parameters for a large sample of such objects using a spatially and photometrically homogeneous data set. Our sample contains 255 visually identified cluster candidates, of which 109 were not listed in any previous catalog. We quantify the crowding effect for the stellar sample produced by the DES Data Management pipeline and conclude that the stellar completeness is < 10% inside typical LMC cluster cores. We therefore develop a pipeline to sample and measure stellar magnitudes and positions around the cluster candidates using DAOPHOT. We also implement a maximum-likelihood method to fit individual density profiles and colour-magnitude diagrams. For 117 (from a total of 255) of the cluster candidates (28 uncatalogued clusters), we obtain reliable ages, metallicities, distance moduli and structural parameters, confirming their nature as physical systems. The distribution of cluster metallicities shows a radial dependence, with no clusters more metal-rich than [Fe/H] ~ -0.7 beyond 8 kpc from the LMC center. The age distribution has two peaks at ~ 1.2 Gyr and ~ 2.7 Gyr