Richard A. Shaw

Scientist
National Optical Astronomy Observatory
950 N. Cherry Avenue
Tucson, AZ 85719
USA

Office: +1-520-318-8398
Fax: +1-520-318-8360
E-mail: shaw at noao dot edu
http://www.noao.edu/noao/staff/shaw/

I could hardly call myself a student of Jim Kaler or Don Osterbrock without having cultivated a deep interest in the astrophysics of gaseous nebulae. This area of knowledge is central to the understanding a wide variety of phenomena, from active galaxies to novae, star-forming regions to planetary nebulae. Analyzing the narrow emission lines from these objects is a powerful means to measure gas density, temperature, and chemical abundances. Some years back, I worked with Reggie Dufour to recast a FORTRAN program developed by Lick Observatory postdocs and graduate students, called FIVEL, into a powerful package in IRAF called nebular, to analyze collisionally excited emission lines. It has evidently had a significant impact on research in this area (see Shaw & Dufour 1995, PASP, 107, 896). Check out the nebular analysis software, which is part of the STSDAS package. Two of the applications are web-enabled: temden, which calculates the electron temperature or density from ratios of collisionally excited ions, and ionic, which calculates line volume-emissivities and ionic abundances. After 13 years, it is time to upgrade this software to a more modern language, add new features and ions, and to make it VO-enabled. I am now working with Arturo Manchado and (soon) a new post-doc on the next generation of nebular.

Planetary nebulae (PNe) are produced by post-Asympotic Giant Branch stars, whose progenitors span a mass range of about 1—8 M_Sun. This relatively brief phase of stellar evolution involves rapid evolution of the central star to very high temperatures, followed by a decline in luminosity as the star approaches white dwarf dimensions. While much is known about PNe, there are a number of fairly profound (and in some cases, simple) questions that remain unanswered: How many PNe are there in the Galaxy? What fraction of sub-supernova stars produce detectible PNe? What forces produce the complex (and beautiful!) morphologies seen in PNe? How many PNe are produced by stars in binary systems?

To probe the questions of the origin of PN shaping, the evolution of dust, and the early star-nebula interaction, I am participating in ongoing Spitzer and HST programs to observe the 130 angularly smallest PNe in the Galaxy. Questions of PN production rates, luminosity functions, and progenitor duplicity can only be examined with complete samples, which are much easier to construct in the Magellanic Clouds (see below).

One of the great advantages of studying Planetary Nebulae (PNe) in the Magellanic Clouds is that we know how far away they are (to ~10% accuracy). This is not so of Galactic PNe, where distances are rarely known to better than 50%. Also, the degree of interstellar extinction is low, so that it is possible to construct flux-limited, volume-complete samples of PNe in the Clouds. Study of such samples can reveal important properties, such as the intrinsic number of PNe per unit stellar luminosity in these galaxies, the distribution among PN morphological types, the range in mass of stars that form PNe, the content and evolution of dust chemistry as the PN central star evolves, and the yield of heavy elements that were generated by their parent AGB stars.

Using most ground-based telescopes, PNe in the Magellanic Clouds are angularly too small to be resolved. But they are easily resolved with Hubble Space Telescope. My colleague Letizia Stanghellini and I have been awarded hundreds of orbits of HST time, and dozens of hours with Spitzer Space Telescope to study Magellanic Cloud PNe. Take a tour of nearly 150 Planetary nebulae in the Large and Small Magellanic Clouds, as seen by HST. This represents 25–30% of all known PNe in these systems.

Often the scope of a question is too broad to address with a small number of targeted observations, and too costly in telescope time to justify a dedicated observing campaign. One major, unresolved question in PN research is to determine the number of PN that are produced by binary progenitors. I have been working lately with key members of the SuperMACHO and OGLE-3 survey teams to study variability in Magellanic Cloud PNe, which could indicate duplicity in the central star. A spectacular, and unexpected result of variability in the nebula itself is shown at right.

One of the expectations (or hopes?) from theory, based largely on momentum considerations, is that PNe with asymmetric morphology are shaped via interaction of the central star with a binary companion or massive planet. Some have argued that all visible PNe may be produced by binary central stars. This works only if the central stars are, in fact, close binaries—which lends itself to observational verification. The SuperMACHO and OGLE-3 surveys observed a large area of the central LMC in broad continuum bands, with a nightly or few-night cadence, over 5 or more years. I've begun to examine the light curves from a complete sample of LMC PNe for indications of binary central stars. Although there are significant selection effects, there are also many signatures that suggest binarity, including outburst events, eclipses, variability within the nebula itself, and irregular light curves. Planned follow-up photometric campaigns on the best candidates will clear up marginal cases, and will help characterize the binary systems.

To complement the search for binary CSs, I am examining IR photometric properties of these PNe from the 2MASS and SAGE catalogs, in order to identify potential Giant binary companions through IR excess.

Accepting institutional responsibility for instrument signature characterization has been slow to catch on in the ground-based optical/IR community, except for the very largest of the publically operated observatories. This was my motivation for compiling and editing the inaugural NOAO Data Handbook, which describes NOAO data products, their processing, and the means to discover and access the data. One chapter covers data from the wide-field Mosaic cameras (the most heavily used instruments); a new chapter on the recently commissioned NEWFIRM IR camera is in preparation.

ADASS: I've been involved with astronomical data systems since 1988: first with NASA's IUE satellite, later with HST, and later still with NOAO. I've been deeply involved in the Astronomical Data Analysis Software and Systems (ADASS) conference, which is the premiere forum for software-intensive systems in astronomy. I spent 15 years on the Program Organizing Committee, and served as chair of that group for 4 years; I also chaired the Local Organizing Committee when ADASS XVI was held in Tucson.

LSST: To this day, data systems and archives in even the most sophisticated astronomical observatories are under-appreciated, yet they are becoming more critical to the scientific success of the observatories and the communities they serve. On no project is this more true than the planned Large Synoptic Survey Telescope, which will survey the entire accessible sky roughly once every 3 nights, to a depth of roughly 25^th mag. Many Tera-bytes of imaging data will be generated per night (a data volume comparable to the entire Sloan Digital Sky Survey), which will result in several Peta-bytes per year of data, catalogs, and database contents.

The bulk of the data management, transport, reduction, calibration, and analysis will have to be fully automated if this project is to succeed. I participate on a team that is designing the Science Data Quality Analysis system, which (as the name implies) measures the realized data quality and the performance of the data management system with respect to expectations and real-time environmental factors. This system will enable evaluation of the observing strategy, the scientific quality of the accumulated data, and progress against the goals of the 10 yr survey.