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A new population of galactic bulge planetary nebulas

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posted on 29.03.2022, 03:26 by Travis Stenborg
A new population of Galactic bulge planetary nebulas is presented. Nebula candidates were discovered by systematically reviewing archival [OIII] on/off band survey imaging of the central -5⁰ ≤ l ≤ 5⁰, -5⁰ ≤ b ≤ 5⁰ region around the Galactic centre. An image segmentation and interleaving scheme was developed to facilitate this review. The resultant candidates (> 200) were then double checked against complementary archival Hα sky survey data to screen for obvious planetary nebula (PN) mimics or spurious image artefacts. Confirmatory spectroscopy of the PN candidates was pursued with thin slit, fibre multiobject and wide field spectrographs. Custom software was built to streamline interfacing with third-party spectroscopic management tools and a parallel greedy set cover algorithm implemented for efficient field selection in constrained multi-object observations. The combined imaging and spectroscopic evidence yielded true (4), probable (31) and possible (83) PNs toward the bulge. Secondary discoveries such as new PN mimics and late type stars were by-products of the confirmatory spectroscopy. Instances of literature PN duplication encountered during the investigation were noticed and documented. Spectral analysis of new PNs, including those obtained with a new optimised sky subtraction technique devised and demonstrated here, provided diagnostic data allowing radial velocity and Balmer decrement determination. Using a combined diameter and radial velocity criterion, bona fide bulge PNs were distinguished from new foreground PNs. Where Balmer decrements were available for new bulge PNs, differential aperture photometry was used to provide a modest data increment to Galactic bulge planetary nebula luminosity function (PNLF). The PNLF was revised with data from some new bulge PNs, but more significantly, by a series of corrections to the data derived from previously known bulge PNs (~225), such as improved filter transmission effects, statistically justified binning and application of a uniform bulge-relevant extinction law. The result was the most rigorous bulge PNLF to date. An improvement on the legacy PNLF, the revised PNLF exhibited a form inconsistent with typical extragalactic examples, an expected result of the unusual extinction correction method used to address bulge-specific observational limitations. Issues restricting the accuracy of the bulge PNLF were identified. Until those restrictions are ameliorated, the utility of the PNLF in aiding physical understanding of its constituent members or their progenitors cannot be realised.

History

Table of Contents

1. Planetary nebulas - history and overview -- 2. The planetary nebula luminosity function -- 3. New bulge PNs -- 4. Duplicate objects -- 5. Other observations -- 6. New bulge PNLF -- 7. Results and discussion -- A. Spectral features -- B. Galactic bulge mosaic II survey fields -- C. Galactic bulge PNs -- D. Publications -- References.

Notes

"January 2016"--title page. Includes bibliographical references The Academic Senate of Macquarie University granted this degree in 2015, but the date 2016 appears on the title page, the verso of the title page and the spine.

Awarding Institution

Macquarie University

Degree Type

Thesis PhD

Degree

PhD, Macquarie University, Faculty of Science and Engineering, Department of Physics and Astronomy

Department, Centre or School

Department of Physics and Astronomy

Year of Award

2016

Principal Supervisor

Orsola De Marco

Rights

Copyright Travis Stenborg 2016. Copyright disclaimer: http://www.copyright.mq.edu.au

Language

English

Extent

1 online resource (xxxiv, 295 pages) illustrations

Former Identifiers

mq:46277 http://hdl.handle.net/1959.14/1083686