13,145 research outputs found

    The Need for An Automated Acuity Tool for Children With Special Health Care Needs

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    Children with special health care needs (CSHCN) often require extended and continuous contact with health care professionals due to their chronic conditions. Additionally, some of these children have other non-health burdens, including multiple problems with access to care, that make it even more difficult to treat their medical illness. These extra obstacles illustrate that effective care for CSHCN requires proper care coordination among a network of doctors, nurses, and care coordinators. Unfortunately, care coordination has been inadequate due to large caseload assignments. An automated acuity tool that reassesses the child’s acuity (low, medium or high) regularly would help balance the caseloads and improve care coordination. Unique to this design, the tool would not only describe disease needs, but also account for modifiable psychosocial characteristics. It would first be deployed in South Florida where the population of CSHCN mainly consists of low-income, minority back- grounds with language barriers. The implementation of an acuity tool provides a thoughtful way to tackle the new challenges within the established structure of pediatric care

    Modified gravity without dark matter

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    On an empirical level, the most successful alternative to dark matter in bound gravitational systems is the modified Newtonian dynamics, or MOND, proposed by Milgrom. Here I discuss the attempts to formulate MOND as a modification of General Relativity. I begin with a summary of the phenomenological successes of MOND and then discuss the various covariant theories that have been proposed as a basis for the idea. I show why these proposals have led inevitably to a multi-field theory. I describe in some detail TeVeS, the tensor-vector-scalar theory proposed by Bekenstein, and discuss its successes and shortcomings. This lecture is primarily pedagogical and directed to those with some, but not a deep, background in General RelativityComment: 28 pages, 10 figures, lecture given at Third Aegean Summer School, The Invisible Universe: Dark Matter and Dark Energy, minor errors corrected, references update

    Stellar and Gaseous Nuclear Disks Observed in Nearby (U)LIRGs

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    We present near-infrared integral field spectroscopy of the central kiloparsec of 17 nearby luminous and ultra-luminous infrared galaxies undergoing major mergers. These observations were taken with OSIRIS assisted by the Keck I and II Adaptive Optics systems, providing spatial resolutions of a few tens of parsecs. The resulting kinematic maps reveal gas disks in at least 16 out of 19 nuclei and stellar disks in 11 out of 11 nuclei observed in these galaxy merger systems. In our late-stages mergers, these disks are young (stellar ages <30<30 Myr) and likely formed as gas disks which became unstable to star formation during the merger. On average, these disks have effective radii of a few hundred parsecs, masses between 10810^{8} and 1010MSun10^{10} M_{Sun}, and v/σv/\sigma between 1 and 5. These disks are similar to those created in high-resolution hydrodynamical simulations of gas-rich galaxy mergers, and favor short coalescence times for binary black holes. The few galaxies in our sample in earlier stages of mergers have disks which are larger (reff∼200−1800r_{eff}\sim200-1800 pc) and likely are remnants of the galactic disks that have not yet been completely disrupted by the merger.Comment: accepted for publication in Ap

    Shocked Gas in IRAS F17207-0014: ISM Collisions and Outflows

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    We combine optical and near-infrared AO-assisted integral field observations of the merging ULIRG IRAS F17207-0014 from the Wide-Field Spectrograph (WiFeS) and Keck/OSIRIS. The optical emission line ratios [N II]/Hα\alpha, [S II]/Hα\alpha, and [O I]/Hα\alpha reveal a mixing sequence of shocks present throughout the galaxy, with the strongest contributions coming from large radii (up to 100% at ∼\sim5 kpc in some directions), suggesting galactic-scale winds. The near-infrared observations, which have approximately 30 times higher spatial resolution, show that two sorts of shocks are present in the vicinity of the merging nuclei: low-level shocks distributed throughout our field-of-view evidenced by an H2_{2}/Brγ\gamma line ratio of ∼\sim0.6-4, and strong collimated shocks with a high H2_{2}/Brγ\gamma line ratio of ∼\sim4-8, extending south from the two nuclear disks approximately 400 pc (∼\sim0.5 arcsec). Our data suggest that the diffuse shocks are caused by the collision of the interstellar media associated with the two progenitor galaxies and the strong shocks trace the base of a collimated outflow coming from the nucleus of one of the two disks.Comment: accepted to MNRA

    Following Black Hole Scaling Relations Through Gas-Rich Mergers

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    We present black hole mass measurements from kinematic modeling of high-spatial resolution integral field spectroscopy of the inner regions of 9 nearby (ultra-)luminous infrared galaxies in a variety of merger stages. These observations were taken with OSIRIS and laser guide star adaptive optics on the Keck I and Keck II telescopes, and reveal gas and stellar kinematics inside the spheres of influence of these supermassive black holes. We find that this sample of black holes are overmassive (∼107−9\sim10^{7-9} MSun_{Sun}) compared to the expected values based on black hole scaling relations, and suggest that the major epoch of black hole growth occurs in early stages of a merger, as opposed to during a final episode of quasar-mode feedback. The black hole masses presented are the dynamical masses enclosed in ∼\sim25pc, and could include gas which is gravitationally bound to the black hole but has not yet lost sufficient angular momentum to be accreted. If present, this gas could in principle eventually fuel AGN feedback or be itself blown out from the system.Comment: accepted to Ap

    MOND vs. Newtonian dynamics in early-type galaxies. The case of NGC 4649 (M60)

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    Context: Regarding the significant interest in both dark matter and the application of MOND to early-type galaxies, we investigate the MOND theory by comparing its predictions, for models of constant mass-to-light ratio, with observational data of the early-type galaxy NGC 4649. Aims: We study whether measurements for NGC 3379 and NGC 1399 are typical of early-type systems and we test the assumption of a Newtonian constant M/L ratio underlying most of the published models. Methods: We employ the globular clusters of NGC 4649 as a mass tracer. The Jeans equation is calculated for both MOND and constant mass-to-light ratio assumptions. Spherical symmetry is assumed and the calculations are performed for both isotropic and anisotropic cases. Results: We found that both Jeans models with the assumption of a constant mass-to-light ratio and different MOND models provide good agreement with the observed values of the velocity dispersion. The most accurate fits of the velocity dispersion were obtained for the mass-to-light ratio in the B-band, which was equal to 7, implying that there is no need for significant amounts of dark matter in the outer parts (beyond 3 effective radii) of this galaxy. We also found that tangential anisotropies are most likely present in NGC 4649.Comment: 6 pages, 4 figure

    A Survey of Atomic Carbon [C I] in High-redshift Main-Sequence Galaxies

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    We present the first results of an ALMA survey of the lower fine structure line of atomic carbon [C I](^3P_1\,-\,^{3}P_0) in far infrared-selected galaxies on the main sequence at z∼1.2z\sim1.2 in the COSMOS field. We compare our sample with a comprehensive compilation of data available in the literature for local and high-redshift starbursting systems and quasars. We show that the [C I](3P1^3P_1→\rightarrow3P0^3P_0) luminosity correlates on global scales with the infrared luminosity LIRL_{\rm IR} similarly to low-JJ CO transitions. We report a systematic variation of L'_{\rm [C\,I]^3P_1\,-\, ^3P_0}/LIRL_{\rm IR} as a function of the galaxy type, with the ratio being larger for main-sequence galaxies than for starbursts and sub-millimeter galaxies at fixed LIRL_{\rm IR}. The L'_{\rm [C\,I]^3P_1\,-\, ^3P_0}/LCO(2−1)′L'_{\rm CO(2-1)} and M[CI]M_{\rm{[C I]}}/MdustM_{\rm dust} mass ratios are similar for main-sequence galaxies and for local and high-redshift starbursts within a 0.2 dex intrinsic scatter, suggesting that [C I] is a good tracer of molecular gas mass as CO and dust. We derive a fraction of f[C I]=M[C I]/MC∼3−13f_{\rm{[C\,I]}} = M_{\rm{[C\,I]}} / M_{\rm{C}}\sim3-13% of the total carbon mass in the atomic neutral phase. Moreover, we estimate the neutral atomic carbon abundance, the fundamental ingredient to calibrate [C I] as a gas tracer, by comparing L'_{\rm [C\,I]^3P_1\,-\, ^3P_0} and available gas masses from CO lines and dust emission. We find lower [C I] abundances in main-sequence galaxies than in starbursting systems and sub-millimeter galaxies, as a consequence of the canonical αCO\alpha_{\rm CO} and gas-to-dust conversion factors. This argues against the application to different galaxy populations of a universal standard [C I] abundance derived from highly biased samples.Comment: 14 pages + Appendix. Accepted for publication in ApJ. All the data tables in Appendix will be also released in electronic forma
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