Aims.
Spectroscopic surveys have by now collectively observed tens of thousands of stars in the bulge of our Galaxy. However, each of these surveys had unique observing and data processing strategies ...that led to distinct stellar parameter and abundance scales. Because of this, stellar samples from different surveys cannot be directly combined.
Methods.
Here we use the data-driven method,
The Cannon
, to bring 21 000 stars from the
ARGOS
bulge survey, including 10 000 red clump stars, onto the parameter and abundance scales of the cross-Galactic survey,
APOGEE
, obtaining rms precisions of 0.10 dex, 0.07 dex, 74 K, and 0.18 dex for Fe/H, Mg/Fe,
T
eff
, and log(
g
), respectively. The re-calibrated
ARGOS
survey – which we refer to as the A2A survey – is combined with the APOGEE survey to investigate the abundance structure of the Galactic bulge.
Results.
We find X-shaped Fe/H and Mg/Fe distributions in the bulge that are more pinched than the bulge density, a signature of its disk origin. The mean abundance along the major axis of the bar varies such that the stars are more Fe/H-poor and Mg/Fe-rich near the Galactic centre than in the outer bulge and the long bar region. The vertical Fe/H and Mg/Fe gradients vary between the inner bulge and the long bar, with the inner bulge showing a flattening near the plane that is absent in the long bar. The Fe/H − Mg/Fe distribution shows two main maxima, an ‘Fe/H-poor Mg/Fe- rich’ maximum and an ‘Fe/H-rich Mg/Fe-poor’ maximum, that vary in strength with position in the bulge. In particular, the outer long bar close to the Galactic plane is dominated by super-solar Fe/H, Mg/Fe-normal stars. Stars composing the Fe/H-rich maximum show little kinematic dependence on Fe/H, but for lower Fe/H the rotation and dispersion of the bulge increase slowly. Stars with Fe/H < −1 dex have a very different kinematic structure than stars with higher Fe/H.
Conclusions.
Comparing with recent models for the Galactic boxy-peanut bulge, the abundance gradients and distribution, and the relation between Fe/H and kinematics suggests that the stars comprising each maximum have separate disk origins with the ‘Fe/H-poor Mg/Fe-rich’ stars originating from a thicker disk than the ‘Fe/H-rich Mg/Fe-poor’ stars.
Context. M49 (NGC 4472) is the dominant galaxy in subcluster B of the Virgo Cluster, and a benchmark for studying the build-up of the extended halos of brightest group galaxies in the outskirts of ...galaxy clusters. Aims. We investigate the kinematics in the outer halo of M49, look for substructures, and describe the transition to the surrounding intra-group light. Methods. As kinematic tracers, we use planetary nebulae (PNe), combining kinematics from the extended Planetary Nebula Spectrograph (PN.S) early-type galaxy survey with our recent deep photometric sample. We study the position-velocity-plane for bright and faint PN populations out to 95 kpc radius, and employ a multi-Gaussian model for the velocity distribution to identify stellar populations with distinct kinematics and histories. Results. We report the detection of stellar-kinematic substructure associated with the interaction of M49 with the dwarf irregular galaxy VCC 1249. We find two kinematically distinct PN populations associated with the main M49 halo and the extended intra-group light (IGL). These have velocity dispersions σhalo ≃ 170 km s−1 and σIGL ≃ 400 km s−1 at 10–80 kpc radii. The overall luminosity profile and velocity dispersion at ~80 kpc are consistent with a flat circular velocity curve extrapolated from X-ray observations. The dispersion of the PNe associated with the IGL joins onto that of the satellite galaxies in subcluster B at ~100 kpc radius. This is the first time that the transition from halo to IGL is observed based on the velocities of individual stars. Conclusions. Therefore the halo of M49, consisting of at least three distinct components, has undergone an extended accretion history within its parent group potential. The blue colours of the IGL component are consistent with a population of stars formed in low-mass galaxies at redshift ~0.5 that has since evolved passively, as suggested by other data.
We determine the Galactic potential in the solar neigbourhood from RAVE observations. We select red clump stars for which accurate distances, radial velocities, and metallicities have been measured. ...Combined with data from the 2MASS and UCAC catalogues, we build a sample of ~4600 red clump stars within a cylinder of 500 pc radius oriented in the direction of the South Galactic Pole, in the range of 200 pc to 2000 pc distances. We deduce the vertical force and the total mass density distribution up to 2 kpc away from the Galactic plane by fitting a distribution function depending explicitly on three isolating integrals of the motion in a separable potential locally representing the Galactic one with four free parameters. Because of the deep extension of our sample, we can determine nearly independently the dark matter mass density and the baryonic disc surface mass density. We find (i) at 1 kpc Kz/ (2πG) = 68.5 ± 1.0 M⊙ pc-2; and (ii) at 2 kpc Kz/ (2πG) = 96.9 ± 2.2 M⊙ pc-2. Assuming the solar Galactic radius at R0 = 8.5 kpc, we deduce the local dark matter density ρDM(z = 0) = 0.0143 ± 0.0011 M⊙pc-3 = 0.542 ± 0.042 Gev cm-3 and the baryonic surface mass density Σbar = 44.4 ± 4.1 M⊙pc-2. Our results are in agreement with previously published Kz determinations up to 1 kpc, while the extension to 2 kpc shows some evidence for an unexpectedly large amount of dark matter. A flattening of the dark halo of order 0.8 can produce such a high local density in combination with a circular velocity of 240 km s-1. It could also be consistent with a spherical cored dark matter profile whose density does not drop sharply with radius. Another explanation, allowing for a lower circular velocity, could be the presence of a secondary dark component, a very thick disc resulting either from the deposit of dark matter from the accretion of multiple small dwarf galaxies, or from the presence of an effective “phantom” thick disc in the context of effective galactic-scale modifications of gravity.
Abstract
The decomposition of the rotation curve of galaxies into contribution from the disc and dark halo remains uncertain and depends on the adopted mass-to-light ratio (M/L) of the disc. Given ...the vertical velocity dispersion of stars and disc scale height, the disc surface mass density and hence the M/L can be estimated. We address a conceptual problem with previous measurements of the scale height and dispersion. When using this method, the dispersion and scale height must refer to the same population of stars. The scale height is obtained from near-infrared (IR) studies of edge-on galaxies and is weighted towards older kinematically hotter stars, whereas the dispersion obtained from integrated light in the optical bands includes stars of all ages. We aim to extract the dispersion for the hotter stars, so that it can then be used with the correct scale height to obtain the disc surface mass density. We use a sample of planetary nebulae (PNe) as dynamical tracers in the face-on galaxy NGC 628. We extract two different dispersions from its velocity histogram – representing the older and younger PNe. We also present complementary stellar absorption spectra in the inner regions of this galaxy and use a direct pixel fitting technique to extract the two components. Our analysis concludes that previous studies, which do not take account of the young disc, underestimate the disc surface mass density by a factor of ∼2. This is sufficient to make a maximal disc for NGC 628 appear like a submaximal disc.
We provide AAVSO Photometric All-Sky Survey (APASS) photometry in the Landolt BV and Sloan g r i bands for all 425, 743 stars included in the fourth RAVE Data Release. The internal accuracy of the ...APASS photometry of RAVE stars, expressed as the error of the mean of data obtained and separately calibrated over a median of four distinct observing epochs and distributed between 2009 and 2013, is 0.013, 0.012, 0.012, 0.014, and 0.021 mag for the B, V, g, r, and i bands, respectively. In the process, we find that the reddening caused by a homogeneous slab of dust, extending for 140 pc on either side of the Galactic plane and responsible for E poles B-V = 0.036 + or - 0.002 at the Galactic poles, is a suitable approximation of the actual reddening encountered at Galactic latitudes b 25degrees.
In preparation for the High Efficiency and Resolution Multi-Element Spectrograph (HERMES) chemical tagging survey of about a million Galactic FGK stars, we estimate the number of independent ...dimensions of the space defined by the stellar chemical element abundances X/Fe. This leads to a way to study the origin of elements from observed chemical abundances using principal component analysis. We explore abundances in several environments, including solar neighbourhood thin/thick disc stars, halo metal-poor stars, globular clusters, open clusters, the Large Magellanic Cloud and the Fornax dwarf spheroidal galaxy. By studying solar-neighbourhood stars, we confirm the universality of the r-process that tends to produce neutron-capture elements/Fe in a constant ratio. We find that, especially at low metallicity, the production of r-process elements is likely to be associated with the production of α-elements. This may support the core-collapse supernovae as the r-process site. We also verify the overabundances of light s-process elements at low metallicity, and find that the relative contribution decreases at higher metallicity, which suggests that this lighter elements primary process may be associated with massive stars. We also verify the contribution from the s-process in low-mass asymptotic giant branch (AGB) stars at high metallicity. Our analysis reveals two types of core-collapse supernovae: one produces mainly α-elements, the other produces both α-elements and Fe-peak elements with a large enhancement of heavy Fe-peak elements which may be the contribution from hypernovae. Excluding light elements that may be subject to internal mixing, K and Cu, we find that the X/Fe chemical abundance space in the solar neighbourhood has about six independent dimensions both at low metallicity (−3.5 ≲ Fe/H ≲−2) and high metallicity (Fe/H ≳−1). However the dimensions come from very different origins in these two cases. The extra contribution from low-mass AGB stars at high metallicity compensates the dimension loss due to the homogenization of the core-collapse supernovae ejecta. Including the extra dimensions from Fe/H, K, Cu and the light elements, the number of independent dimensions of the X/Fe+Fe/H chemical space in the solar neighbourhood for HERMES is about eight to nine. Comparing fainter galaxies and the solar neighbourhood, we find that the chemical space for fainter galaxies such as Fornax and the Large Magellanic Cloud has a higher dimensionality. This is consistent with the slower star formation history of fainter galaxies. We find that open clusters have more chemical space dimensions than the nearby metal-rich field stars. This suggests that a survey of stars in a larger Galactic volume than the solar neighbourhood may show about one more dimension in its chemical abundance space.
Objectives Esophageal stent placement has been shown to be a safe and effective treatment for acute esophageal perforation in selected patients. However, a comparison between surgical repair and ...stent placement has not been reported. This investigation compares the outcomes and costs of the 2 treatment modalities. Methods The Premiere database for a single health system's hospitals was used to identify patients undergoing treatment for an acute intrathoracic esophageal perforation over a 4-year period. Patient cohorts for stent placement or surgical repair were formed using propensity matching. The 2 cohorts were compared for length of stay, morbidity, mortality, and costs. Results Between 2009 and 2012, 60 patients undergoing esophageal stent placement or surgical repair were propensity matched. Mean patient age and Charlson comorbidity scores did not differ significantly ( P = .4 and P = .4, respectively). Significant differences in morbidity (4% vs 43%; P = .02), mean length of stay (6 vs 11 days; P = .0007), time to oral intake (3 vs 8 days; P = .0004), and cost ($91,000 vs $142,000; P < .0001) were identified in the esophageal stent cohort when compared with patients receiving surgical repair. Operative mortality did not differ significantly. Conclusions Esophageal stent placement for the treatment of an acute esophageal perforation seems to be as effective as surgical repair when compared between propensity-matched patients. However, stent placement resulted in a shorter length of stay, lower rates of morbidity, and lower costs when compared with traditional surgical repair.
Neuroblastoma (NBL) is an embryonal cancer of the sympathetic nervous system (SNS), which causes 15% of pediatric cancer deaths. High-risk NBL is characterized by N-Myc amplification and segmental ...chromosomal gains and losses. Owing to limited disease models, the etiology of NBL is largely unknown, including both the cell of origin and the majority of oncogenic drivers. We have established a novel system for studying NBL based on the transformation of neural crest cells (NCCs), the progenitor cells of the SNS, isolated from mouse embryonic day 9.5 trunk neural tube explants. Based on pathology and gene expression analysis, we report the first successful transformation of wild-type NCCs into NBL by enforced expression of N-Myc, to generate phenotypically and molecularly accurate tumors that closely model human MYCN-amplified NBL. Using comparative genomic hybridization, we found that NCC-derived NBL tumors acquired copy number gains and losses that are syntenic to those observed in human MYCN-amplified NBL including 17q gain, 2p gain and loss of 1p36. When p53-compromised NCCs were transformed with N-Myc, we generated primitive neuroectodermal tumors with divergent differentiation including osteosarcoma. These subcutaneous tumors were metastatic to regional lymph nodes, liver and lung. Our novel experimental approach accurately models human NBL and establishes a new system with potential to study early stages of NBL oncogenesis, to functionally assess NBL oncogenic drivers and to characterize NBL metastasis.
Rationale
Compounds lacking efficacy at the α1 subunit–containing GABA
A
(α1GABA
A
) receptor appear to have reduced abuse potential compared with those having measurable efficacy at this receptor, ...though their self-administration in nonhuman primates is dependent upon past drug experience.
Objectives
We used a drug vs. drug choice procedure to evaluate the hypothesis that L-838,417, a compound lacking efficacy at αGABA
A
receptors, would not enhance cocaine choice in monkeys trained to self-administer cocaine. We also hypothesized that zolpidem, a compound with preferential modulation of ⍺1GABA
A
receptors and midazolam, a nonselective benzodiazepine, would enhance cocaine choice in this procedure.
Methods
One female and three male rhesus monkeys chose between cocaine alone (0.1 mg/kg/injection) vs. the same dose of cocaine combined with midazolam (0.003–0.1 mg/kg/injection), zolpidem (0.003–0.3 mg/kg/injection), or L-838-417 (0.01–0.1 mg/kg/injection). In addition, we evaluated choice between saline and L-838,417 at select doses to determine whether L-838,417 would function as a reinforcer on its own.
Results
Consistent with our hypotheses, midazolam- and zolpidem-cocaine mixtures were chosen over cocaine alone at sufficiently high doses. However, L-838,417-cocaine mixtures also were chosen over cocaine alone in three of four subjects with at least one dose. When available alone vs. saline, L-838,417 did not function as a reinforcer in any subject.
Conclusion
Compounds that lack efficacy at α1GABA
A
receptors may have low abuse potential compared to classic benzodiazepines, but self-administration of these compounds is context-dependent.
Using a sample of 213 713 stars from the Radial Velocity Experiment (RAVE) survey, limited to a distance of 2 kpc from the Sun and to |z| < 1 kpc, we report the detection of a velocity gradient of ...disc stars in the fourth quadrant, directed radially from the Galactic Centre. In the direction of the Galactic Centre, we apply a simple method independent of stellar proper motions and of Galactic parameters to assess the existence of this gradient in the RAVE data. This velocity gradient corresponds to |K+C| > rsim 3 km s−1 kpc−1, where K and C are the Oort constants measuring the local divergence and radial shear of the velocity field, respectively. In order to illustrate the effect, assuming a zero radial velocity of the local standard of rest we then reconstruct the two-dimensional Galactocentric velocity maps using two different sets of proper motions and photometric distances based either on isochrone fitting or on K-band magnitudes, and considering two sets of values for the Galactocentric radius of the Sun and local circular speed. Further observational confirmation of our finding with line-of-sight velocities of stars at low latitudes, together with further modelling, should help constrain the non-axisymmetric components of the Galactic potential, including the bar, the spiral arms and possibly the ellipticity of the dark halo.
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