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Theoretical Astrophysics in Australia
Submission to Decadal Plan Working Group 3.1
G.V. Bicknell and A. Melatos

April 2005
Introduction
In this document, we identify the v alue of theoretical and c omputational astrophysics to the astronomy community generally and to the aims of the Dec adal Plan. We also pres ent our vision for the fut ure. In particular, we point out: · · The c entral role played by indi vidual researchers in delivering the theoretical infrastructure to support Australian astronomy. The need for a specific plan to increase the number and diversity (whilst maint aining the quality) of personnel with ex pertise in theoretic al astrophysics who are employed in National Facilities, univ ersit ies, and Centres of Excellence (CoEs ). The need t o incorporate theoretic al infrastructure into ev ery st age of t he life cycle of a National Facility: setting science goals, selecting and designing instruments, handling and interpreting scientific data. The need to provide nationally c ompetitive s upercomputing fac ilities, net work infrastructure, and local CPU and storage resources to support theoretical work based on large-sc ale c omputations. The value of the Australian National Institute for Theoretic al Astrophysics (ANI TA) as a high-lev el organizational structure for some of thes e initiatives. The value of ANITA in c ontinuing to develop astronomy within Australia as a coherent, rigorous ac ademic discipline and educational pathway for attracting young people into science and engineering, e. g. by organizing postgraduate winter schools and training mediated by facilities such as the Access Grid.

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People Advances in t heoretic al astrophysics (and physic s generally) underpin the discipline of astronomy as a whole. The sy mbiosis between experimental and t heoretic al science is typical of all scientific disciplines ­ wit h each branch inf orming and stimulating the other. Australian astronomy therefore needs a strong t heoretic al infrastruct ure to remain vit al and robust. This infrastructure is mainly composed of people. The need for human infrastructure has already been rec ognized, with a number of new tenured appoint ments in theoretical astrophysics being made in univ ersity depart ments over the last five years. 1 It is essential that t his pattern be maintained. We also rec ommend that it be enhanc ed in the following ways.

1

Asplund, Suther land ( RSAA) ; Donea ( Monash); Cairns, Ku ncic, Lew is, Wheatland (Sydney); Melatos, Wyith e ( Melbourne); Gibson, Madd ison (Sw inburne); W ardle ( Macquarie).


1. Institutional diversificati on. At the present tim e, our theoretical infrastructure resides almost entirely in university depart ments (physics, astronomy, and mathematics). Whilst t his is nat ural to s ome degree, some diversification will become necessary in the next decade. Univ ersity appoint ments should be supplemented with appoint ments in National Facilities and Centres of Exc ellenc e (combining obs ervational, theoretic al, and c omputational astrophysics) to maximiz e the scientific impact of the next generation of National Facilities. This is discussed further below. 2. New positions and critical mass. It is possible that opport unities will arise to create new positions in univ ersities ov er the next decade, driv en by demand from foreign students, for example. Suc h opportunit ies might flow from a broad national initiative to boost the number of res earc h-intensiv e ac ademics, as occurred rec ently in Canada, or from individual institutions wishing to boost their representation in astronomy, a subject that is a proven draw card with students. In such a climate of increased resources, c areful thought s hould be given t o building theoretical groups with critic al mass. 3. Career str ucture. At the present time, most theoretical and computational astrophysicists (and indeed most obs ervational astrophysicists) operate within the standard `career pyramid', progressing from student to post doctoral researc h associat e to fix ed t erm research or lecturing appoint ments to t enured ac ademic (with subst antial attrition at each stage). This struc ture meets some ­ but not all ­ of the needs of the Australian astronomy community, especially in view of the long-term nature of the planned invest ment in new National Facilities. An issue in this regard is the spec ial position of code-developers ­ people who engage in the time-consuming and challenging task of writing general-purpos e comput er simulations, whic h are subs equently used by hundreds of people to model basic physical process es, motivat e the design of new obs ervational facilities, and interpret the dat a from facilities. Code-dev elopers are the theory analogue of instrument-builders. Both groups are somewhat underapprec iated in academe, because the painstaking and long-term nature of their work harms their rate of publication. Nevert heless, they are absolutely vit al to the astronomical ent erprise. We rec ommend that alternative c areer struct ures be developed f or thes e groups, e.g. wit hin National Facilities, or through multi-stage, long-term postdoct oral schemes where public ation rate is not the only selection crit erion. Integr ati ng Theory i nto National Facilities Theory will be integrat ed deeply into every stage of the life cycle of the next generation of major observ ational facilities ­ the telescopes themselv es and the instruments they host. Bef ore c onstruction, theory inspires the science driv ers and design ­ what do we really need to build, and with what specifications (given theoretical predictions of what one will s ee)? How should the science c ase be localized to the Australian context? After construction, theorists maximize the scientific impact of the facility ­ by interpreting and synthesizing the enormous amounts of data it produces, and by fertilizing the next round of "big" theoretic al ideas. Internationally, this symbiosis is well established (e.g. in missions lik e NGST, Chandra, and WMAP, and in facility-related scienc e institutes like STScI) and is inevitable in large ($10M+) projects.


We recommend that a s pecific plan be developed t o resource the int egration of theoretical and comput ational infrastructure into National Facilities. Such integration cannot be sustained s olely on t he back of ARC grant funding t o theoretical and computational astrophysicists in universities. At the pres ent time, approximately $1M per annum in ARC DP funding (inc luding fellows hips) comes to astronomy, and t here is the possibility of securing a similar additional amount through a Centre of Exc ellence. Ev en in an extreme sc enario where these res ources are dev oted entirely to scientific (including theoretical and computational) support of National Facilities, they are insufficient (as a percentage of the capital and operating costs of a $100M-class facility) to ensure that the scientific impact of the Facilities is maximized (at least, that part of the impact whic h is identifiably Australian). Two types of resources are needed to implement t his plan. Before construction, the main requirement is for (modest) project-spec ific funding to support theoretical and computational modeling of the scienc e goals and to feed scientific input int o the engineering design of the National Facility. After construction, the main requirement is for a sensible fraction of the scienc e component of the facility/instrument operating budget to be devoted to relev ant theoretical work. For ex ample, the ATNF and AAO currently employ staff scientists (approx imately 10-15% of f acility staff) who fulfill dual functional and researc h roles. We recommend that these dual-role positions be opened to applicants with theoretical and computational expertise as well, and that suc h applicants are proactiv ely enc ouraged to apply, in line with international practic e (e.g. STScI). Ex amples of functional roles ideally suited to such applic ants include dev eloping data processing pipelines, algorithms, and Virt ual Obs ervat ory infrastructure, simulating the obs erv ational parameter spac e (and hence influencing the design) of new facilities, and participating in policy dev elopment and facility management. Similarly, we recommend that a balanced frac tion of the post doctoral positions in National Facilities (e. g. Bolton and ot her fellows hips) s hould be opened to theoretical/ computational applic ants whos e res earch interests are c ompatible with the Facility. Again, such positions would include a functional component where appropriate. Below we summarize Fac ilities planned for these opport unities infrastr ucture in that some of the key scientific opportunities available to the National the next decade. To help exploit them fully, we match each of with Australian institutions that currently provide theoreti cal area.

Radio: Square Kilometer Array, Extended New Technology Demonstr ator, Low Frequency Demonstrator 1. Structure of the Univ erse at the epoch of reioniz at ion ­ formation of the first stars (Melbourne, Swinburne) 2. Origin and dynamics of magnetic fields in the Galactic interstellar medium, including new techniques for scintillation imaging (Sydney, Macquarie) 3. Energy generation by compact objects ­ radiation and outflows from black holes and neutron stars (Sy dney, Melbourne, RSAA, Monash) 4. Cos mological distribution of neutral hy drogen ­ evolution of structure, star formation, and the dark energy equation of state (UNSW, Swinburne)


Optical/Infrar ed: Extremely Lar ge Telescope, Antarcti cic Astr onomy 1. Formation of extras olar planets in disks around young stars (Monas h, Swinburne, RSAA) 2. Distribution of matter and energy in the Univers e ­ theoretical analysis of dat a from future wide-field reds hift surveys, the successors of 2dF and 6dF (UNSW, Sydney, Swinburne, RSAA, Melbourne) 3. Sy mbiosis bet ween supermassiv e black holes, galaxy formation, and galactic activity (RSAA, Melbourne, Sydney ) Millimeter: Australia Telescope Compact Array Upgrade 1. Formation of stars, especially high-mass stars, in the turbulent, magnetized interstellar medium (Macquarie, Swinburne) 2. Galactic arc haeology ­ the hist ory of the chemic al elements in the galaxy (RSAA, Swinburne, Monash) Gravitati onal waves: Australian Consorti um for Interfer ometric Gravitati onal Wave Astr onomy, Pulsar Ti ming Array 1. Grav ity wav es from accreting neutron stars and merging neutron stars ­ a new non-electromagnetic window on the Univ ers e (ANU, Monas h, Melbourne) 2. Grav ity wav es from merging galaxies in the early Univers e (Melbourne) 3. Tests of strong-field gravity (ANU, Monash, Melbourne) Hi gh-ener gy particles: CANGAROO 1. Origin and composition of the highest-energy cosmic rays (Adelaide, Monas h, Melbourne) 2. High-energy radiation from neutron stars and supernova remnants (Sydney, Melbourne) 3. Particle (e. g. neutrino) astrophysics (Adelaide, Melbourne) 4. High energy radiation from blazers (Adeldaide, RSAA) Computati onal Resources Approximately 50% of theoretical astrophysics research in Australia utiliz es advanced computation on stat e of the art computational fac ilities. It is fortunate that these facilities can be easily c entralized and s hared across a wide range of scienc es, so that the initial capital cost and s ubsequent upgrades, maint enance, and depreciation are spread ov er a divers e range of scientific programs. The welc ome and far-sighted establishment of centres such as the Australian Partnership f or Adv anc ed Comput ation (APAC), the Sydney­bas ed Australian Centre for Adv anced Computing and Communications (AC3), and the Victorian Partnership in Adv anc ed Computation (VPAC) testifies t o the fact t hat this type of activity cannot be s upported on a stand-alone basis by every University; when supercomputing was introduced int o Australia in the mid 1980's, it was quickly realized t hat a national fac ility model would be effective. It is therefore ess ential that the existing superc omputing centres be maint ained and expanded, t ogether with the software and maintenance infrastructure needed to support c omputational astrophysics in particular. An ess ential element of the abov e model is t he provision of high-bandwidth connectivity to all academic us ers. This will ass ume even greater importance s hortly, when grid computing and Access Grid c ommunications become common.


At the same time, advanced computation requires significant local facilities in the form of multi-terabyt e storage and CPU c apability for the post-proc essing of out put, for specialpurpos e experiments, and for student training. There are numerous examples where these activities, especially student training, hav e subs equently led to applications in other tec hnological areas. For thes e reasons, the development of computational infrastructure wit hin univ ersities should be enc ouraged. The international trend t owards publishing s oftware f or, and output from, theoretical simulations on-line, in parallel with the on-line publication of obs ervational data, opens up new opportunities conc erning how comput ational astrophysics will be done in the future. We recommend that sufficient resources be alloc ated (through the us ual funding channels, e.g. LI EF) to the development of the theory component of the Australian Virtual Observ atory (AVO), e.g. standardizing and doc umenting simulation software for publication, c ompiling standard dictionaries of c ontent descript ors, and designing port als to facilitat e running t he s oftware on t he grid and combining its out put with observational data in the VO. ANI TA The mission of ANI TA is to: 1. Develop the Australian theoretic al and computational astrophysics community by facilitating communic ation and collaboration bet ween theorists and providing a focus for the community; 2. Raise the national and int ernational profile of theoretical astrophysics; 3. Promote links with the national astronomic al community by assisting in the theoretical interpretation of obs ervations, motiv ating new obs erv ational programmes and increasing the scientific ret urn from national inv est ment in observational infrastructure. ANITA currently consists of 39 ac ademic/professional staff, 23 student members and is operated by a steering committee cons isting of a convenor, an immediat e past convenor, seven steering c ommittee members including a student member and ex officio the president of the ASA. ANI TA has a good relationship wit h the ASA; the c onv enor has been invited t o serv e on ASA c ouncil. ANI TA f ormally commenced in October 2003 but had been active for about a year previously. Full details of ANI TA's activities may be found at the website www.anita. edu. au. ANITA provides a ready-made organiz ational structure t o coordinate efficiently many of the activities disc ussed abov e. For example, ANI TA supplies representatives to working groups that form to plan new observational facilities (telescopes and instruments). ANITA can also help to coordinat e the inv olvement of theoretical and computational groups in Centres of Exc ellence and related initiatives. And ANI TA is well plac ed t o represent the interests of the community in devising a national strat egy f or the development of computational (superc omputing and net work ing) infrastructure through APAC, VPAC, and university facilities, as well as devising a national strategy for the theoretical and obs ervational components of the Virtual Obs ervatory. We propose that a mechanis m be identified to gain some operational funding for ANI TA in the short term. The main use of this funding will be to support the highly s uccessful


program of workshops and conferences organized with minimal res ourc es by ANI TA since its inception.2 Excitingly, these workshops have been attended by a wide crosssection of the Australian astronomical community, including observ ational astronomers and PhD students. They are bec oming an important community resourc e. With increased funding, ANI TA would be able, for exam ple, to subs idiz e student attendance and invite international researc hers to give key not e talks. The required amount of funding is modest, approximately $20k per annum.

ANI TA and Graduate Education Separately, we recommend that funding be secured to design and then run an annual series of graduate lecture courses in astrophysic s, delivered partly via the Access Grid but also through a t wo-week residential workshop analogous to the Harley Wood Winter School. ANI TA is prepared t o coordinat e suc h a lecture s eries. It is import ant that Australian graduate students in astronomy are well trained in the f oundations of their discipline. Training opportunities are currently provided in obs ervational techniques (e.g. ATNF Synthesis Works hop); the ANI TA lectures would provide an analogous training opportunity in the fundamentals of astrophysics, which do not rec eive uniform coverage in the c urric ula of all Australian univers ities at the present time. Leading scientists fro m Australian institutions would offer the courses, supplemented by international lecturers if funding permits. The scale of funding required is estimated at approx imately $100k to establis h the programme and produc e teac hing materials, followed by annual operating costs of $50k, funded perhaps from an endowment or long-term grant. General comments 1. We emphasiz e t hat the interpretation of data should not be s een as the only role of theory, alt hough all good theoretical work is ultimately inspired by t he richness of the observ ed sky. Aspects of astrophysic al theory that may not be amenable to immediate observational tests are nonetheless crucial to our understanding of astrophysical proc esses. 2. Theorists are res ponsible f or the dev elopment of new techniques that have a wide-ranging impact on astronomy. Australian examples include t he t heory of thermal and nonthermal emission from astrophysic al plas mas and the computational t echnique Smoothed Particle Hy drodynamics (SPH). The latter is a good ex ample of an industrial linkage ­ SPH is used in the movie industry for the realistic generation of sequenc es of moving gases and fluids. 3. New major observ ational projects (say equivalent in sc ope to the 2dF project) should factor in budgetary support for theoreticians and should inv olve theoreticians in the planning stages. This would maximiz e the scientific payoff to the Australian community from key observ ational projects.
2

Stellar Astrophysics (Swin, 2005), Computational Astrophysics (ATN F, 2005), High-Energy Astrophysics ( RSAA, 2004), Grav ity (U Syd, 2004), 2nd ANI TA Workshop ( Macq, 2003), Galactic Ceh modynamics (Swin, 2003), Th eoretical Astrophysics and the VO (USyd , 2003), AGN and Starbursts ­ Char lene Heisler ( RSAA , 2002), Nu clear Astrophysics with the Murchison Meteor ite ( Monash , 2002), 1st ANITA Workshop ( Monash, 2002).


4. Many theoreticians and observ ers participate in scientific projects involvin overs eas­bas ed fac ilities suc h as the Chandra X­ray Observ atory. A fund s houl be establis hed to s upport aspects of this activit y that are not covered by th ANSTO Large Facilities Fund and to educate other Australian astronomers in th utilization of suc h international facilities.

g d e e

5. As a res ult of the ARC funding program for Centres of Excellence, it is expected that both theorists and obs ervers will seiz e the opportunity to formulat e competitive bids for such centres. The theoretic al community is enc ouraged to take adv antage of these opportunities and to formulate internationally competitive and widely-inc lusiv e proposals. 6. There is strong interest in some quarters for the creation of a theoretical institut e with a mandat e to take a leading national role, similar in some respects to the role of our national observ ational facilities. This would inv olve a large amount of lobbying of state and federal governments and Universities and would require a dedicated individual or group of individuals to lead such an initiative. Whilst there is no c urrent propos al for suc h a c entre, we do not rule it out as a possibility within the next ten y ears. 7. The main tradition of Australian astronomical observational research is in radio and optical astronomy. However, both theoreticians and observers realize that qualitatively different information comes from areas such as X­ray and gamma­ ray astronomy ­ true multi-wavelength research must embrace these parts of the electromagnetic spectrum as well. In many c ases, theoreticians lead new research in thes e fields, developing important link ages for the whole c ommunity.


Appendix A: Summary of theoretical and computati onal resear ch pr oj ects and infrastr ucture in Australian astr onomy

Fiel d(s) Solar and Space Physics (Solar seis mology, s olar and planetary radio emission, solar radio bursts and flares, auroras) Plas ma astrophysics (Plas ma emission, absorption and transfer processes, particle acceleration) Planetary Science Stellar structure and ev olution; effects of env ironment on nuclear fusion Star formation Interstellar medium (HII regions, Galactic Centre, scintillation, molecular shock waves, phot odiss ociation regions) Astrobiology Compact objects (neutron stars, puls ars, relativistic puls ar winds, accretion disk-magnetosphere interaction) Extragalactic astronomy (galaxy formation and evolution, activ e galactic nuc lei) Cos mology (big bang, microwav e back ground, dark matter, dark energy, epoc h of reionis ation, variation of fundamental constants, Ly man alpha forest) General relativity (classic al and quantum) Grav itational lensing (mass models of lensing galaxies, cos mological and statistical lensing, quasar structure) Grav itational waves and their detection Computational astrophysics

Institution(s) Sydney, Monash Sydney ANU, Monash, Swinburne ANU, Monash, UNSW Macquarie, NSW ANU, UNSW, Sy dney Macquarie, UNSW ANU, Melbourne, Sydney Adelaide, ANU, Monash, UNSW, Swinburne, Sydney, Melbourne ANU, Melbourne, UNSW ANU, Monash, UNSW Melbourne, Sydney ANU, Melbourne, UNSW ANU, Macquarie, Monas h, UNSW, Swinburne, Sydney

In many of the above areas of activity listed in the abov e table, theorists hav e collaborated with observ ers, adding value to the substantial observational programs carried out using Australian national and universit y facilities. Other theoretic al res earc h contributes to the design of new facilities such as the Square Kilomet er Array.


Appendix B: Summary of i nternati onal pr ojects invol ving Australian theoreti cians Proj ect CANGAROO GammaRay Obs ervat ory Hadronic models of active galactic nuclei Project LUNASKA: UHE neutrino astrophysics with the SKA Grav itational Wave Detection High energy astrophysics of Active Galaxies Australian Institutions Adelaide, ANU, Sydney Adelaide Adelaide, ATNF Adelaide, ANU, UWA, Monash, Edith Cowan Univ, CSI RO ANU, Sydney Inter nati onal Instituti ons Univ. of Tokyo led cons ortium of Japanes e universities Max Planck Institut fuer Radioastronomie, Bonn Univ. of Delaware, University of Santiago de Compostela LIGO (US project), GEO (UK/German project), TAMA (Japanese project) Landessternwarte & Max Planck Institut fuer Astrophysik, Heidelberg, Univers ity College, London; Consortium of US astronomers using the Chandra X-ray Obs ervat ory Berk eley, Univ. of Maryland, Caltech, Oxf ord Berk eley and U. Wisc onsin, Royal Obs. Edinburgh Mic higan State Univ. and Univ. of Copenhagen Univ. of Heidelberg Victoria Univ. of Wellington, MaxPlanck-Institut fÝr Quantenoptik Northwestern University, Illinois CfA Harvard; Princet on MI T; Canadian Institute for Theoretic al Astrophysics Univ. of Oslo Colorado Res earc h Assoc iates, GONG High Altitude Observ atory, Colorado IoA, Cambridge IoA, Cambridge IoA, Cambridge and U. Utrec ht American Museum of Nat ural History, IoA Cambridge Univers ity of California, Sant a Cruz

Starburst Galax ies and Galactic Centre Epoch of Galaxy Formation Three Dimensional Stellar Convection Models of Mira Variable Stars Laboratory Cos mology Supernov a remnant masers Epoch of reionisation Neutron star accretion Relativistic pulsar winds Solar Activ e Region Seis mology Solar Tac hocline Instabilities Evolution of Stellar Populations SPH and MHD Blue Straggler Production in Open Clusters Planetary Disruption in Star Clusters Stability and evolution of

ANU, AAO A NU A NU A NU A NU Macquarie Melbourne Melbourne Melbourne Monash Monash Monash Monash Monash Monash Monash


planetary cores Evolution of neutron star binaries Stability of small-N systems in star clusters Interactions between VLBI jets and the surrounding medium The effects of voids of primordial origins Formation of the Milky Way Origin of post-starburst galaxies Ultra Compact Dwarf galaxy formation Cos mological variation of fundamental constants Thick disk sub-structure & halo kinematics Effects of environment on nuclear fusion Galactic Streams Cos mological simulations/ SKA Galactic Chemical Evolution Accretion onto Magnetised Stars Warped CV Disks Building Planets with Dusty Gas Synthetic IR I mages of Prot ostars Planets in Binary Systems Dusty Debris Disks Solar system radio bursts Sub-mm cos mology Grav itational lensing Giant puls es from pulsars Puls ar polarisation Interstellar scintillation Puls ar spectra

Monash Monash Monash, Adelaide NS W NS W NS W NS W NS W Swinburne NS W Sydney, Swinburne Swinburne, Sydney Monash Sydney, Swinburne Swinburne Swinburne Swinburne Swinburne Swinburne Sydney Sydney Sydney, Melbourne Sydney Sydney Sydney Sydney

Oxford IoA, Cambridge Astronomic al Institute of the Romanian Ac ademy; University College Cork, Ireland Sussex, Oxf ord Tohok u Univ ersity Tohok u Univ ersity U. of Bonn, Space Telescope Science Institute; Univ. of Calif.; Bristol U.; Nottingham Univ. Imperial College; Cambridge; UC San Diego; UC Lick Obs.; Penn. State; Novos ibirsk Tuorla Observ atory, Finland Princ eton; Mic higan State U. Strassbourg Observatory, Franc e; Cambridge University Arizona State; Durham Univ ersity; Univ. of Victoria, BC; Univ. of Washingt on St Mary's College, Canada Rome Obs. St Andrews, UK Open University, UK Canadian Institute for Theoretical Astrophysics, Universite de Lyon Univers ite de Grenoble Potsdam, Germany Princ eton and CfA, USA UC Berk eley Caltech MI T, Heidelberg, NRAO Stanford Jodrell Bank; GMRT UCSD; Palermo Univ.; Kaptey n Institute; NAO, Beijing Oberling College, Yamagata U.


Energy balance of the solar corona Solar neutrino time-series analysis Magnetic rec onnection & solar flare statistics

Sydney Sydney Sydney

U. New Hamps hire Stanford U. Waikato