ABSTRACT We present new, more precise measurements of the mass and distance of our Galaxy's central supermassive black hole, Sgr A*. These results stem from a new analysis that more than doubles the ...time baseline for astrometry of faint stars orbiting Sgr A*, combining 2 decades of speckle imaging and adaptive optics data. Specifically, we improve our analysis of the speckle images by using information about a star's orbit from the deep adaptive optics data (2005-2013) to inform the search for the star in the speckle years (1995-2005). When this new analysis technique is combined with the first complete re-reduction of Keck Galactic Center speckle images using speckle holography, we are able to track the short-period star S0-38 (K-band magnitude = 17, orbital period = 19 yr) through the speckle years. We use the kinematic measurements from speckle holography and adaptive optics to estimate the orbits of S0-38 and S0-2 and thereby improve our constraints of the mass (Mbh) and distance (Ro) of Sgr A*: Mbh = (4.02 0.16 0.04) × 106 M and 7.86 0.14 0.04 kpc. The uncertainties in Mbh and Ro as determined by the combined orbital fit of S0-2 and S0-38 are improved by a factor of 2 and 2.5, respectively, compared to an orbital fit of S0-2 alone and a factor of ∼2.5 compared to previous results from stellar orbits. This analysis also limits the extended dark mass within 0.01 pc to less than 0.13 × 106 M at 99.7% confidence, a factor of 3 lower compared to prior work.
We report new precision measurements of the properties of our Galaxy's supermassive black hole. Based on astrometric (1995-2007) and radial velocity (RV; 2000-2007) measurements from the W. M. Keck ...10 m telescopes, a fully unconstrained Keplerian orbit for the short-period star S0-2 provides values for the distance of image kpc, the enclosed mass of image, and the black hole's RV, which is consistent with zero with 30 km s super(-1) uncertainty. If the black hole is assumed to be at rest with respect to the Galaxy (e.g., has no massive companion to induce motion), we can further constrain the fit, obtaining image kpc and image. More complex models constrain the extended dark mass distribution to be less than 3-image within 0.01 pc, image100 times higher than predictions from stellar and stellar remnant models. For all models, we identify transient astrometric shifts from source confusion (up to 5 times the astrometric error) and the assumptions regarding the black hole's radial motion as previously unrecognized limitations on orbital accuracy and the usefulness of fainter stars. Future astrometric and RV observations will remedy these effects. Our estimates of image and the Galaxy's local rotation speed, which it is derived from combining image with the apparent proper motion of Sgr A*, (image km s super(-1)), are compatible with measurements made using other methods. The increased black hole mass found in this study, compared to that determined using projected mass estimators, implies a longer period for the innermost stable orbit, longer resonant relaxation timescales for stars in the vicinity of the black hole and a better agreement with the image -image relation.
We present a study of the X-ray flaring activity of Sgr A⋆ during all the 150 XMM–Newton and Chandra observations pointed at the Milky Way centre over the last 15 years. This includes the latest ...XMM–Newton and Chandra campaigns devoted to monitoring the closest approach of the very red Brγ emitting object called G2. The entire data set analysed extends from 1999 September through 2014 November. We employed a Bayesian block analysis to investigate any possible variations in the characteristics (frequency, energetics, peak intensity, duration) of the flaring events that Sgr A⋆ has exhibited since their discovery in 2001. We observe that the total bright or very bright flare luminosity of Sgr A⋆ increased between 2013 and 2014 by a factor of 2–3 (∼3.5σ significance). We also observe an increase (∼99.9 per cent significance) from 0.27 ± 0.04 to 2.5 ± 1.0 d−1 of the bright or very bright flaring rate of Sgr A⋆, starting in late summer 2014, which happens to be about six months after G2's pericentre passage. This might indicate that clustering is a general property of bright flares and that it is associated with a stationary noise process producing flares not uniformly distributed in time (similar to what is observed in other quiescent black holes). If so, the variation in flaring properties would be revealed only now because of the increased monitoring frequency. Alternatively, this may be the first sign of an excess accretion activity induced by the close passage of G2. More observations are necessary to distinguish between these two hypotheses.
Dust formation in supernova ejecta is currently the leading candidate to explain the large quantities of dust observed in the distant, early universe. However, it is unclear whether the ejecta-formed ...dust can survive the hot interior of the supernova remnant (SNR). We present infrared observations of ∼0.02 solar masses of warm (∼100 kelvin) dust seen near the center of the ∼10,000-year-old Sagittarius A East SNR at the Galactic center. Our findings indicate the detection of dust within an older SNR that is expanding into a relatively dense surrounding medium (electron density ∼103 centimeters–3) and has survived the passage of the reverse shock. The results suggest that supernovae may be the dominant dust-production mechanism in the dense environment of galaxies of the early universe.
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BFBNIB, NMLJ, NUK, PNG, SAZU, UL, UM, UPUK
Curiosity investigated active eolian sands near linear dunes during Phase 2 of the Bagnold Dunes campaign in Gale crater, Mars. Ogunquit Beach, a sample scooped from a large‐ripple trough within the ...Mount Desert Island ripple field and delivered to the Chemistry and Mineralogy (CheMin) X‐ray diffraction instrument, is dominated by basaltic igneous minerals and X‐ray amorphous materials. CheMin mineralogy of the Gobabeb sample acquired at a large‐ripple crest on the Namib barchan dune during Phase 1 is similar to Ogunquit Beach. Ogunquit Beach, however, contains more plagioclase and Gobabeb contains more olivine. Compact Reconnaissance Imaging Spectrometer for Mars (CRISM)‐based estimates of mineralogy at the optical surface of Namib Dune and Mount Desert Island demonstrate that surface sands are enriched in olivine and depleted in plagioclase over Mount Desert Island relative to Namib Dune. Differences between CheMin‐derived and CRISM‐derived mineralogies suggest sorting by grain size on bedform to dune field scales. Crystal chemistry from CheMin suggests contributions from multiple igneous sources and the local bedrock.
Plain Language Summary
Remote sensing data from orbit indicate that wind‐blown sands in the Bagnold Dune Field in Gale crater, Mars, are sorted by their composition. The Mars Science Laboratory Curiosity rover studied the Bagnold Dune Field at two locations to investigate the chemical and mineral composition of the sands and why they are sorted across the dune field. Data from Curiosity show distinct differences between the minerals in the upwind portion of the dune field compared to the downwind portion, but these differences are not the same as those observed from orbit. The scale and location of the sampling by Curiosity compared to orbiters explains the discrepancy between the two techniques. Results from both techniques suggest subtle differences in mineralogy within a single dune and across the dune field that can be explained by sorting from wind and contribution from the erosion of local bedrock.
Key Points
The mineralogy of active eolian sands were measured by the Curiosity rover at two locations in the Bagnold Dune Field in Gale crater, Mars
X‐ray diffraction data from the CheMin instrument of two sand samples indicate differences in plagioclase and olivine abundances
The mineralogy derived from CheMin and CRISM can be used in concert to characterize sediment sorting and sources across the Bagnold Dunes
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
ABSTRACT
We present the first results from a study of O vi absorption around galaxies at z < 1.44 using data from a near-infrared grism spectroscopic Hubble Space Telescope Large Programme, the ...Quasar Sightline and Galaxy Evolution (QSAGE) survey. QSAGE is the first grism galaxy survey to focus on the circumgalactic medium at z ∼ 1, providing a blind survey of the galaxy population. The galaxy sample is H α flux limited (f(H α) > 2 × 10−17 erg s−1 cm−2) at 0.68 < z < 1.44, corresponding to ≳0.2–0.8 M⊙ yr−1. In this first of 12 fields, we combine the galaxy data with high-resolution STIS and COS spectroscopy of the background quasar to study O vi in the circumgalactic medium. At z ∼ 1, we find O vi absorption systems up to b ∼ 350 kpc (∼4Rvir) from the nearest detected galaxy. Further, we find ${\sim }50{{\ \rm per\ cent}}$ of ≳1 M⊙ yr−1 star-forming galaxies within 2Rvir show no associated O vi absorption to a limit of at least N(O vi) = 1013.9 cm−2. That we detect O vi at such large distances from galaxies and that a significant fraction of star-forming galaxies show no detectable O vi absorption disfavours outflows from ongoing star formation as the primary medium traced by these absorbers. Instead, by combining our own low- and high-redshift data with existing samples, we find tentative evidence for many strong (N(O vi) > 1014 cm−2) O vi absorption systems to be associated with M⋆ ∼ 109.5–10 M⊙ mass galaxies (Mhalo ∼ 1011.5–12 M⊙ dark matter haloes), and infer that they may be tracing predominantly collisionally ionized gas within the haloes of such galaxies.
Summary
This guideline updates and replaces the 4th edition of the AAGBI Standards of Monitoring published in 2007. The aim of this document is to provide guidance on the minimum standards for ...physiological monitoring of any patient undergoing anaesthesia or sedation under the care of an anaesthetist. The recommendations are primarily aimed at anaesthetists practising in the United Kingdom and Ireland. Minimum standards for monitoring patients during anaesthesia and in the recovery phase are included. There is also guidance on monitoring patients undergoing sedation and also during transfer of anaesthetised or sedated patients. There are new sections discussing the role of monitoring depth of anaesthesia, neuromuscular blockade and cardiac output. The indications for end‐tidal carbon dioxide monitoring have been updated.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The 2004 EJN Lecture was an attempt to lay out further aspects of a developing neurobiological theory of hippocampal function Morris, R.G.M., Moser, E.I., Riedel, G., Martin, S.J., Sandin, J., Day, ...M. & O'Carroll, C. (2003) Phil. Trans. R. Soc. Lond. B Biol. Sci., 358, 773–786. These are that (i) activity‐dependent synaptic plasticity plays a key role in the automatic encoding and initial storage of attended experience; (ii) the persistence of hippocampal synaptic potentiation over time can be influenced by other independent neural events happening closely in time, an idea with behavioural implications for memory; and (iii) that systems‐level consolidation of memory traces within neocortex is guided both by hippocampal traces that have been subject to cellular consolidation and by the presence of organized schema in neocortex into which relevant newly encoded information might be stored. Hippocampal memory is associative and, to study it more effectively than with previous paradigms, a new learning task is described which is unusual in requiring the incidental encoding of flavour–place paired associates, with the readout of successful storage being successful recall of a place given the flavour with which it was paired. NMDA receptor‐dependent synaptic plasticity is shown to be critical for the encoding and intermediate storage of memory traces in this task, while AMPA receptor‐mediated fast synaptic transmission is necessary for memory retrieval. Typically, these rapidly encoded traces decay quite rapidly over time. Synaptic potentiation also decays rapidly, but can be rendered more persistent by a process of cellular consolidation in which synaptic tagging and capture play a key part in determining whether or not it will be persistent. Synaptic tags set at the time of an event, even many trivial events, can capture the products of the synthesis of plasticity proteins set in train by events before, during or even after an event to be remembered. Tag–protein interactions stabilize synaptic potentiation and, by implication, memory. The behavioural implications of tagging are explored. Finally, using a different protocol for flavour–place paired associate learning, it is shown that rats can develop a spatial schema which represents the relative locations of several different flavours of food hidden at places within a familiar space. This schema is learned gradually but, once acquired, enables new paired associates to be encoded and stored in one trial. Their incorporation into the schema prevents rapid forgetting and suggests that schema play a key and hitherto unappreciated role in systems‐level memory consolidation. The elements of what may eventually mature into a more formal neurobiological theory of hippocampal memory are laid out as specific propositions with detailed conceptual discussion and reference to recent data.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
We present 19.7, 31.5, and 37.1 mu m images of the inner 6 pc of the Galactic center of the Milky Way with a spatial resolution of 3".2-4".6 taken by the Faint Object Infrared Camera on the ...Stratospheric Observatory for Infrared Astronomy. The images reveal in detail the "clumpy" structure of the circumnuclear ring (CNR)-the inner edge of the molecular torus orbiting the supermassive black hole at the Galactic center-and the prominent streamers of hot, ionized gas and dust within the CNR that compose the H II region Sgr A West. The CNR exhibits features of a classic H II region: the dust emission at 19.7 mu m closely traces the ionized gas emission observed in the radio while the 31.5 and 37.1 mu m emission traces the photo-dissociation region beyond the ionized gas. The 19.7/37.1 color temperature map reveals a radial temperature gradient across the CNR with temperatures ranging from 65 to 85 K, consistent with the prevailing paradigm in which the dust is centrally heated by the inner cluster of hot, young stars. We model the 37.1 mu m intensity of the CNR as an inclined (thetai = 67degrees) ring with a thickness and radius of 0.34 pc and 1.4 pc, respectively, and find that it is consistent with the observed 37.1 mu m map of the CNR. The 37.1 mu m optical depth map also reveals the clumpy dust distribution of the CNR and implies a total gas mass of ~610 M sub(middot in circle). Dense (5-9 x 10 super(4) cm super(-3)) clumps with an FWHM of ~0.15 pc exist along the inner edge of the CNR and shadow the material deeper into the ring. We find that the clumps are unlikely to be long-lived structures since they are not dense enough to be stable against tidal shear from the supermassive black hole and will be sheared out on a timescale of an orbital period (~10 super(5) yr).
We present the first results from the Bulge Asymmetries and Dynamic Evolution (BAaDE) survey. Though only a subset of the complete survey (∼2700 out of ∼20,000 final sources), our data comprise the ...largest radio kinematic survey to date of stellar SiO masers observed toward the Galactic bulge and plane from −15° < l < +12° and −6° < b < +6°. Our sources include a substantial number of line-of-sight velocities in high extinction regions within 1° of the Galactic plane. When matched with 2MASS photometry, our radio-detected sample lies significantly brighter than and redward of the first red giant branch tip, reaching extremes of (J − Ks)0 > 8, colors consistent with Mira variables and mass-losing AGB stars. We see a clean division into two kinematic populations: a kinematically cold ( ∼ 50 km s−1) population that we propose is in the foreground disk, consisting of giants with 2MASS Ks < 5.5, and a kinematically hot ( ∼ 100 km s−1) candidate bulge/bar population for most giants with Ks > 5.5. Only the kinematically hot giants with Ks > 5.5 include the reddest stars. Adopting 8.3 kpc to the Galactic center, and correcting for foreground extinction, we find that most of the sources have Mbol ∼ −5, consistent with their being luminous and possibly intermediate-age AGB stars. We note some tension between the possible intermediate age of the kinematically hot population, and its high-velocity dispersion compared to the disk.
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