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In this study of abdominal aortic aneurysm repair, endovascular repair was shown to have an early survival advantage over open repair during the first three years. However, interventions related to aneurysm and ruptures were more common after endovascular repair. The use of endovascular repair of abdominal aortic aneurysms is increasing. By 2010, endovascular repair accounted for 78% of all intact repairs. 1 , 2 Randomized, controlled trials comparing endovascular repair with open repair generally have shown a perioperative benefit of endovascular repair over open repair. 3 – 5 Long-term survival, however, is similar with the two approaches. 6 – 9 As data on long-term outcomes accumulate, concerns have been raised about endovascular repair with respect to the increased rate of late failure leading to rupture and higher rates of reintervention. In our previous analyses performed with the use of Medicare data, which account for more . . .

Stellar SiO masers are found in the atmospheres of asymptotic giant branch (AGB) stars with several maser transitions observed around 43 and 86 GHz. At least 28 SiO maser stars have been detected within ∼2 pc projected distance from Sgr A* by the Very Large Array (VLA) and Atacama Millimeter/submillimeter Array (ALMA). A subset of these masers have been studied for several decades and form the basis of the radio reference frame that anchors the reference frame for infrared stars in the Galactic Center (GC). We present new observations of the GC masers from VLA and ALMA. These new data combined with extant maser astrometry provide 3D positions, velocities, and acceleration limits. The proper motions and Doppler velocities are measured with unprecedented precision for these masers. We further demonstrate how these measurements may be used to trace the stellar and dark matter mass distributions within a few pc of Sgr A*.

OH megamasers (OHMs) are luminous masers found in (ultra-)luminous infrared galaxies ([U]LIRGs). OHMs are signposts of major gas-rich mergers associated with some of the most extreme star forming regions in our universe. The dominant OH masing line, occurring at 1667 MHz, can spoof the 1420 MHz neutral hydrogen (HI) line in untargeted HI emission line surveys. While only ∼120 OHMs are currently known, HI surveys on next-generation radio telescopes, such as the Square Kilometre Array (SKA) and its precursors, will detect unprecedented numbers of OHMs. This surge in detections will not only fundamentally change what we know about the OHM population, but will also unlock our ability to implement OHMs as tracers of major mergers and extreme star formation on cosmic scales. Here we present predictions for the number of OHMs that will be detected by these surveys. We also present our novel methods for identifying these interlopers using a k-Nearest Neighbors machine learning algorithm. Preliminary data from HI surveys on precursor SKA telescopes is being used to vet and strengthen these methods as well as give us a first look at a new era in OHM science. From a detection of one of the most luminous OHMs to the discovery of a megamaser at a record-shattering redshift, these new sources are glimpses into how our understanding of the known OHM population will soon be expanding and shifting rapidly and how they will influence our understanding of galaxy evolution.

The detection of the accelerated expansion of the Universe has been one of the major breakthroughs in modern cosmology. Several cosmological probes (Cosmic Microwave Background, Supernovae Type Ia, Baryon Acoustic Oscillations) have been studied in depth to better understand the nature of the mechanism driving this acceleration, and they are being currently pushed to their limits, obtaining remarkable constraints that allowed us to shape the standard cosmological model. In parallel to that, however, the percent precision achieved has recently revealed apparent tensions between measurements obtained from different methods. These are either indicating some unaccounted systematic effects, or are pointing toward new physics. Following the development of CMB, SNe, and BAO cosmology, it is critical to extend our selection of cosmological probes. Novel probes can be exploited to validate results, control or mitigate systematic effects, and, most importantly, to increase the accuracy and robustness of our results. This review is meant to provide a state-of-art benchmark of the latest advances in emerging “beyond-standard” cosmological probes. We present how several different methods can become a key resource for observational cosmology. In particular, we review cosmic chronometers, quasars, gamma-ray bursts, standard sirens, lensing time-delay with galaxies and clusters, cosmic voids, neutral hydrogen intensity mapping, surface brightness fluctuations, stellar ages of the oldest objects, secular redshift drift, and clustering of standard candles. The review describes the method, systematics, and results of each probe in a homogeneous way, giving the reader a clear picture of the available innovative methods that have been introduced in recent years and how to apply them. The review also discusses the potential synergies and complementarities between the various probes, exploring how they will contribute to the future of modern cosmology.

We discuss properties of the atmospheric water vapor above the high Andean plateau region known as the Llano de Chajnantor, in the Atacama Desert of northern Chile. A combination of radiometric and radiosonde measurements indicates that the median column of precipitable water vapor (PWV) above the plateau at an elevation of 5000 m is approximately 1.2 mm. The exponential scale height of the water vapor density in the median Chajnantor atmosphere is 1.13 km; the median PWV is 0.5 mm above an elevation of 5750 m. Both of these values appear to be lower at night. Annual, diurnal, and other dependences of PWV and its scale height are discussed, as well as the occurrence of temperature inversion layers below the elevation of peaks surrounding the plateau. We estimate the background for infrared observations and sensitivities for broadband and high‐resolution spectroscopy. The results suggest that exceptional atmospheric conditions are present in the region, yielding high infrared transparency and high sensitivity for future ground‐based infrared telescopes.

Masers in starburst galaxies are outstanding probes of a range of phenomena related to galaxy and black hole evolution, star formation, and magnetic fields. Here I briefly discuss five related topics: (1) Galactic analog water masers in nearby galaxies; (2) multiwavelength solutions to the OH megamaser puzzle in major galaxy mergers; (3) formaldehyde anti-inversion in starburst galaxies; (4) OH spoofing in HI surveys; and (5) new discovery space in radio line surveys. New insights into the physical conditions responsible for OH megamasers, including indications of a critical molecular gas density obtained from the formaldehyde “densitometer,” will be applicable to future surveys, particularly surveys for redshifted hydrogen where OH lines arising in major galaxy mergers can “contaminate” the disk population identified by the HI 21 cm line. Blind radio spectral line surveys also offer the opportunity for unexpected discoveries of new nonthermal radio lines.

An observer moving with respect to the cosmic rest frame should observe a concentration and brightening of galaxies in the direction of motion and a spreading and dimming in the opposite direction. The velocity inferred from this dipole should match that of the cosmic microwave background (CMB) temperature dipole if galaxies are on average at rest with respect to the CMB rest frame. However, recent studies have claimed a many-fold enhancement of galaxy counts and flux in the direction of the solar motion compared to the CMB expectation, calling into question the standard cosmology. Here we show that the sky distribution and brightness of extragalactic radio sources are consistent with the CMB dipole in direction and velocity. We use the first epoch of the Very Large Array Sky Survey combined with the Rapid Australian Square Kilometer Array Pathfinder Continuum Survey to estimate the dipole via several different methods, and all show similar results. Typical fits find a \\(331^{+161}_{-107}\\) km s\\(^{-1}\\) velocity dipole with apex \\((\\ell,b) = (271^{+55}_{-58}, 56^{+13}_{-35})\\) in Galactic coordinates from source counts and \\(399^{+264}_{-199}\\) km s\\(^{-1}\\) toward \\((\\ell,b) = (301^{+30}_{-30}, 43^{+19}_{-17})\\) from radio fluxes. These are consistent with the CMB-solar velocity, 370 km s\\(^{-1}\\) toward \\((\\ell,b) = (264, 48)\\), and show that galaxies are on average at rest with respect to the rest frame of the early universe, as predicted by the canonical cosmology.

We present new astrometric constraints on the stochastic gravitational wave background and construct the first astrometric Hellings-Downs curve using quasar proper motions. From quadrupolar vector spherical harmonic fits to the Gaia proper motions of 1,108,858 quasars, we obtain a frequency-integrated upper limit on the gravitational wave energy density, \\(h_{70}^2\\Omega_{GW} \\leq 0.023\\) (95% confidence limit), for frequencies between 11.2 nHz and \\(3.1\\times10^{-9}\\) nHz (\\(1.33/t_0\\)). However, from the astrometric Hellings-Downs curve that describes the correlated proper motions between 2,104,609,881 quasar pairs as a function of their angular separation, we find a much stronger constraint: a characteristic strain of \\(h_{c} \\leq 2.9 \\times 10^{-12}\\) for \\(f_{\\rm ref} = 1\\) yr\\(^{-1}\\) and \\(h_{70}^2\\Omega_{\\rm GW} \\leq 0.010\\) at 95% confidence. We probe down to \\(\\pm\\)0.005 \\(\\mu\\)as\\(^2\\) yr\\(^{-2}\\) in correlated power and obtain the lowest astrometric limit to date. This is also the first time that optical wavelength astrometry surpasses limits from radio-frequency interferometry. This astrometric analysis does not yet reach the sensitivity needed to detect the pulsar timing-based red gravitational wave spectrum extrapolated to the quasar gravitational wave sensitivity window, assuming that the turnover in the spectrum occurs at \\(\\sim\\)1 nHz for massive black hole binaries. The limits presented here may exclude some exotic interpretations of the stochastic gravitational wave background.

We report on a search for dark matter axion conversion photons from the magnetosphere of the Galactic Center magnetar PSR J1745-2900 using spectra obtained from the Karl G. Jansky Very Large Array. No significant spectral features are detected. Using a hybrid model for PSR J1745-2900 and canonical assumptions about the dark matter density profile, we exclude axion models with axion-photon coupling \\(g_{a\\gamma\\gamma}\\) > 6-34 x 10\\(^{-12}\\) GeV\\(^{-1}\\) with 95% confidence over the mass ranges 4.2-8.4, 18.6-26.9, 33.0-41.4, 53.7-62.1, and 126.0-159.3 \\(\\mu\\)eV. If there is a dark matter cusp, the limits reduce to \\(g_{a\\gamma\\gamma}\\) > 6-34 x 10\\(^{-14}\\) GeV\\(^{-1}\\), which overlap some axion models for the observed mass ranges > 33 \\(\\mu\\)eV. These limits may be improved by modeling the stimulated emission that can boost the axion-photon conversion process.

The region surrounding the Llano de Chajnantor, a high‐altitude plateau in the Atacama Desert in northern Chile, has caught the attention of the astronomical community for its potential as an observatory site. Combining high elevation and extremely low atmospheric water content, the Llano has been chosen as the future site of the Atacama Large Millimeter Array. We have initiated a campaign to investigate the astronomical potential of the region in the optical/infrared. Here we report on an aspect of our campaign aimed at establishing a seeing benchmark to be used as a reference for future activities in the region. After a brief description of the region and its climate, we describe the results of an astronomical seeing campaign, carried out with a Differential Image Motion Monitor that operates at 0.5 μm wavelength. The seeing at the Llano altitude of 5000 m, measured over 7 nights in 1998 May, yielded a median FWHM of 1 \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $\\farcs$\\end{document} 1. However, the seeing decreased to 0 \\documentclass{aastex} \\usepackage{amsbsy} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{bm} \\usepackage{mathrsfs} \\usepackage{pifont} \\usepackage{stmaryrd} \\usepackage{textcomp} \\usepackage{portland,xspace} \\usepackage{amsmath,amsxtra} \\usepackage[OT2,OT1]{fontenc} \\newcommand\\cyr{ \\renewcommand\\rmdefault{wncyr} \\renewcommand\\sfdefault{wncyss} \\renewcommand\\encodingdefault{OT2} \\normalfont \\selectfont} \\DeclareTextFontCommand{\\textcyr}{\\cyr} \\pagestyle{empty} \\DeclareMathSizes{10}{9}{7}{6} \\begin{document} \\landscape $\\farcs$\\end{document} 7 at a modest 100 m gain above the plateau (Cerro Chico), as measured over 38 nights spread between 1998 July and 2000 October. Neither of these represents the best seeing expected in the region; the set of measurements provides a reference base for simultaneous dual runs at Cerro Chico and at other sites of interest in the region, currently underway. A comparison between simultaneous measurements at Cerro Chico and Cerro Paranal indicates that the seeing at Cerro Chico is about 12% better than that at Paranal. The percentage of optically photometric nights in the Chajnantor region is about 60%, while that of nights useful for astronomical work is near 80%.