We have completed a robotic wide‐angle imaging survey of the southern sky ( \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 $\delta =+15^{\circ }$ \end{document} to −90°) at 656.3 nm wavelength, the Hα emission line of hydrogen. Each image of the resulting Southern Hα Sky Survey Atlas (SHASSA) covers an area of the sky 13° square at an angular resolution of approximately 0 \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepa...

/pdf/a-robotic-wide-angle-ha-survey-of-the-southern-sky-52eph5ybus.pdf

A Robotic Wide-Angle Hα Survey of the Southern Sky

We report the results of [O III] λ5007 surveys for planetary nebulae (PNe) in six galaxies: NGC 2403, NGC 3115, NGC 3351, NGC 3627, NGC 4258, and NGC 5866. Using on-band/off-band [O III] λ5007 images, as well as images taken in Hα, we identify samples of PNe in these galaxies and derive their distances using the planetary nebula luminosity function (PNLF). We then combine these measurements with previous data to compare the PNLF, Cepheid, and surface brightness fluctuation (SBF) distance scales. We use a sample of 13 galaxies to show that the absolute magnitude of the PNLF cutoff is fainter in small, low-metallicity systems, but the trend is well modeled by the theoretical relation of Dopita, Jacoby, & Vassiliadis. When this metallicity dependence is removed, the scatter between the Cepheid and PNLF distances becomes consistent with the internal errors of the methods and independent of any obvious galaxy parameter. We then use these data to recalibrate the zero point of the PNLF distance scale. We use a sample of 28 galaxies to show that the scatter between the PNLF and SBF distance measurements agrees with that predicted from the techniques' internal errors and that there is no systematic trend between the distance residuals and stellar population. However, we also find that the PNLF and SBF methods have a significant scale offset: Cepheid-calibrated PNLF distances are, on average, ~0.3 mag smaller than Cepheid-calibrated SBF distances. We discuss the possible causes of this offset and suggest that internal extinction in the bulges of the SBF calibration galaxies is the principal cause of the discrepancy. If this hypothesis is correct, then the SBF-based Hubble constant must be increased by ~7%. We also use our distance to NGC 4258 to argue that the short distance scale to the LMC is correct and that the global Hubble constant inferred from the Hubble Space Telescope Key Project should be increased by 8% ± 3% to H0 = 78 ± 7 km s-1 Mpc-1.

Planetary nebulae as standard candles. xii. connecting the population i and population ii distance scales

We present the Macquarie/AAO/Strasbourg Hα Planetary Nebula Catalogue (MASH) of over 900 true, likely and possible new Galactic planetary nebulae (PNe) discovered from the AAO/UKST Hα survey of the southern Galactic plane. The combination of depth, resolution, uniformity and areal coverage of the Hα survey has opened up a hitherto unexplored region of parameter space permitting the detection of this significant new PN sample. Away from the Galactic bulge the new PNe are typically more evolved, of larger angular extent, of lower surface brightness and more obscured (i.e. extinguished) than those in most previous surveys. We have also doubled the number of PNe in the Galactic bulge itself and although most are compact, we have also found more evolved examples. The MASH catalogue represents the culmination of a seven-year programme of identification and confirmatory spectroscopy. A key strength is that the entire sample has been derived from the same, uniform observational data. The 60 per cent increase in known Galactic PNe represents the largest ever incremental sample of such discoveries and will have a significant impact on many aspects of PN research. This is especially important for studies at the faint end of the PN luminosity function which was previously poorly represented.

/pdf/the-macquarie-aao-strasbourg-ha-planetary-nebula-catalogue-12ms9qzbeb.pdf

The Macquarie/AAO/Strasbourg Hα Planetary Nebula Catalogue: MASH

Planetary Nebulae in our Galaxy and Beyond

Far-Ultraviolet Spectroscopic Explorer (FUSE) spectra of 100 extragalactic objects and two distant halo stars are analyzed to obtain measures of O VI λλ1031.93, 1037.62 absorption along paths through the Milky Way thick disk/halo. Strong O VI absorption over the velocity range from -100 to 100 km s-1 reveals a widespread but highly irregular distribution of O VI, implying the existence of substantial amounts of hot gas with T ~ 3 × 105 K in the Milky Way thick disk/halo. The integrated column density, log [N(O VI) cm-2], ranges from 13.85 to 14.78 with an average value of 14.38 and a standard deviation of 0.18. Large irregularities in the gas distribution are found to be similar over angular scales extending from 45°) range from -46 to 82 km s-1, with a high-latitude sample average of 0 km s-1 and a standard deviation of 21 km s-1. High positive velocity O VI absorbing wings extending from ~100 to ~250 km s-1 observed along 21 lines of sight may be tracing the flow of O VI into the halo. A combination of models involving the radiative cooling of hot fountain gas, the cooling of supernova bubbles in the halo, and the turbulent mixing of warm and hot halo gases is required to explain the presence of O VI and other highly ionized atoms found in the halo. The preferential venting of hot gas from local bubbles and superbubbles into the northern Galactic polar region may explain the enhancement of O VI in the north. If a fountain flow dominates, a mass flow rate of approximately 1.4 M⊙ yr-1 of cooling hot gas to each side of the Galactic plane with an average density of 10-3 cm-3 is required to explain the average value of log [N(O VI) sin |b|] observed in the southern Galactic hemisphere. Such a flow rate is comparable to that estimated for the Galactic intermediate-velocity clouds.

Distribution and Kinematics of O VI in the Galactic Halo

A list of 1820 objects, each of them called at least once a planetary nebula, has been inspected; 1143 of them have been classified as true or probable planetary nebulae by the authors of the catalogue (Tables 1); 347 objects, the status of which is still unclear, were classified among the “possible” planetary nebulae (Table 2).; 330 objects have been rejected, on various grounds, from the community of planetary nebulae (Table 3).

Strasbourg-ESO Catalogue of Galactic Planetary Nebulae

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Strasbourg-ESO Catalogue of Galactic Planetary Nebulae