* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download ph600-12 - University of Kent
Survey
Document related concepts
History of astronomy wikipedia , lookup
History of Solar System formation and evolution hypotheses wikipedia , lookup
Timeline of astronomy wikipedia , lookup
Aquarius (constellation) wikipedia , lookup
International Ultraviolet Explorer wikipedia , lookup
Corvus (constellation) wikipedia , lookup
High-velocity cloud wikipedia , lookup
Theoretical astronomy wikipedia , lookup
Type II supernova wikipedia , lookup
Observational astronomy wikipedia , lookup
Stellar evolution wikipedia , lookup
Transcript
PH700 Project Prof Michael D. Smith Centre for Astrophysics & Planetary Science University of Kent Towards a resolution of a burning issue in Astrophysics, from the fields of solar system, galactic or extragalactic astronomy. Recent problems between observational data and theory provide a rich source of issues to be investigated. This project will focus on a specific phenomenom of high interest and motivation, in one of extragalactic astronomy, galactic astronomy, or solar system astronomy. The study will begin with a review of recent publications which address the issue and an evaluation of possible solutions. To achieve this, all major physical processes involved will be understood in depth and detail. Then, data will be obtained from an appropriate source and analysed in order to generate, in an original way, fresh evidence for or against the available solutions. The study will then consider new or hybrid solutions before considering how these can be tested. The relevance of new ground-based telescopes or space missions will be discussed. +++++++++++++++++++++++++++++++++++++++++++++++ The aim of this PH600 project is to investigate how low mass stars like our Sun and brown dwarves are formed. Models for the formation of such stars through infall from a molecular core into an envelope and then via a spinning accretion disc on to the protosatr can be tested by comparing predictions to a range of observational parameters. These include the bolometric and extreme ultraviolet luminosities, the core, envelope and disc mass, and the jet and outflow momentum and energy. If there is a gradual evolution, these parameters should undergo coordinated changes. Or, if there are short superimposed outbursts, the effects on the statistics should be apparent. The specific method is to further develop a code written in the IDL language (similar to matlab) to determine possible evolutionary tracks on assuming the variation with time of the accretion rate from the clump on to the star and calculating how the star, envelope and outflow evolve. This is achieved by making analytical prescriptions for the components based on current knowledge. Learning Outcomes: Experience in computational physics. Experience in undertaking a literature review Detailed knowledge of an area of astrophysics Experience in obtaining new data, data analysis and presenting data Experience in communicating findings through a written report +++++++++++++++++++++++++++++++++++++++++++++++ The project will be based on an aspect of: How do stars like the Sun form? Watch talks by Testi, Garay, and try others: http://www.eso.org/sci/meetings/2012/ESOat50/program.html From a cloud, into a clump, into a core where angular momentum holds it up - it forms the spinning disc from which material slowly accretes on to the star. How is the angular momentum extracted? through jets? Diverted into planets? Or diffused out through the accretion disc? As our starting point, we could take: http://adsabs.harvard.edu/abs/2000IrAJ...27...25S and update or reconstruct using IDL which is very similar to matlab. I am doing the case of massive stars at this moment. You could revisit the low-mass brown dwarf formation scenario, add new observational data sets and update the theory. http://adsabs.harvard.edu/abs/2006MNRAS.368..435F There is plenty in those papers so dont worry if you get lost - we have a habit of not explaining things properly except to the initiated! http://adsabs.harvard.edu/abs/2011AAS...21734035B http://adsabs.harvard.edu/abs/2005ApJ...627..293Y Evolutionary Signatures in the Formation of Low-Mass Protostars Authors: Young, Chadwick H.; Evans, Neal J., II We present an evolutionary picture of a forming star. We assume a singular isothermal sphere as the initial state of the core that undergoes collapse, as described by Shu. We include the evolution of a first hydrostatic core at early times and allow a disk to grow, as predicted by Adams & Shu. We use a onedimensional radiative transfer code to calculate the spectral energy distribution for the evolving protostar from the beginning of collapse to the point when all envelope material has accreted onto the star + disk system. Then, we calculate various observational signatures (Tbol, Lbol/Lsmm, and infrared colors) as a function of time. As defined by the bolometric temperature criterion, the Class 0 stage should be very short, while the Class I stage persists for much of the protostar's early life. We present physical distinctions among the classes of forming stars and calculate the observational signatures for these classes. Finally, we present models of infrared colormagnitude diagrams, as observed by the Spitzer Space Telescope, that should be strong discriminators in determining the stage of evolution for a protostar. http://adsabs.harvard.edu/abs/2010ApJ...710..470D Evolutionary Models of the Formation of Protostars out of LowMass, Dense Cores: Towards Reconciling Models and Observations Authors: Dunham, M. M.; Evans, N. J., II; Terebey, S.; Dullemond, C. P.; Young, C. H. A long-standing problem in low-mass star formation is the “luminosity problem,” whereby protostars are underluminous compared to the expected accretion luminosity. Motivated by this problem, we present a set of evolutionary models describing the collapse of low-mass, dense cores into protostars, using the evolutionary models describing the collapse of low-mass, dense cores into protostars, using the Young & Evans (2005) evolutionary models as our starting point. We calculate the radiative transfer, spectral energy distributions, and observational signatures of the collapsing cores to directly compare to observations. We incorporate several additions to the Young & Evans (2005) model in an effort to better match observations, including: (1) the opacity from scattering, (2) a circumstellar disk directly in the 2-D radiative transfer, (3) a two-dimensional, rotationally flattened envelope, (4) mass-loss and the opening of outflow cavities, and (5) a simple treatment of episodic mass accretion. We find that scattering, twodimensional geometry, mass-loss, and outflow cavities all affect the model predictions, as expected, but none resolve the luminosity problem. On the other hand, a cycle of episodic mass accretion similar to that predicted by recent theoretical work can resolve this problem and bring the model predictions into better agreement with observations. http://adsabs.harvard.edu/abs/2012ApJ...747...52D Resolving the Luminosity Problem in Low-mass Star Formation Authors: Dunham, Michael M.; Vorobyov, Eduard I. dddd Resolving the Luminosity Problem in Low-mass Star Formation Authors: Dunham, Michael M.; Vorobyov, Eduard I. http://adsabs.harvard.edu/abs/2012ApJ...747. ..52D Resolving the Luminosity Problem in Low-mass Star Formation Authors: Dunham, Michael M.; Vorobyov, Eduard I. . Stage 1 Review Subject: literature from journals Read Emily Tipper’s Intro to the Code. Note that you must build on this and will not be allowed to copy anything from this. What is a low mass star ? Why are they important? How do we observe them and their effects? How do they form? What models are there for star formation? What are the issues that still need resolving? Use ADS system to perform literature review. http://adsabs.harvard.edu/abstract_service.html Stage 2: Understand the Model Read 2001ureview.pdf http://adsabs.harvard.edu/abs/2000IrAJ...27...25S massive120930.pdf What does the Unification Scheme do? What is it good for and what are its limitations? Are there alternative schemes? The widely accepted paradigm for the formation of solar-type stars via spherical accretion (Shu et al. 1987) predicts an evolution from cores to protostars, and finally pre-main sequence stars. The peak of the SED shifted from wavelengths longward of 100 m for Class 0 objects toward shorter wavelengths the more the YSO approaches the Main Sequence (MS). Establishing a similar scenario for high-mass YSOs is much more difficult due to the clustered environments in which they are born and to the large ( kpc) characteristic distances exceeding one kiloparsec. Stage 3: Understand the Code What is IDL and how does it work? Quick Start: IDL Introduction What it is and why is it so good? http://www.astro.virginia.edu/class/oconnell/astr511/IDLguide.html All IDL programmes have the explicit extension '.pro'. http://chaos.swarthmore.edu/courses/phys6_2004/IDL_Notes_P6.pdf There are many other IDL guides on the internet. Find your favourite. e.g. http://www.dfanning.com/ There is also the help associated with the installed programme. What you need to know….quick confidence booster: Save the programme intro.pro Click on your IDL icon to start IDL. Go to the top bar and 'file' 'open...' and open intro.pro Find wherever you put intro.pro and click on that. it appears in the main grey area, where it can be edited. This is just a calculator, reading in useful constants and then calculated a density near the end and giving print commands. To run it: Go to the top bar and choose Run, compile intro.pro The answer comes in the middle window. ************************************************** Next level; More complicated: open intro-cosmo run intro-cosmo In the middle window appears the names of two modules: PARAMETERS and COSMO These are the two separate programmes contained in intro-cosmo.pro. In this case, actually, running PARAMETERS will ask it to also run COSMO before finishing. You can see that if you scan through it. To run the programme, go to the command line right at the bottom ....the one-liner with IDL> Type just the one word: parameters Then you should see that it calculates, in the middle window, the complete set of parameters for 3c465 ....this is my own tool for calculating the distance of a quasar or galaxy from its redshift - you have to integrate from us to the object to do it. There is a loop in the code over 30000 steps which does the integration - dont worry about that - its the whole concept of programming contained here. More help ideas: http://vis.lbl.gov/NERSC/Software/idl/help/docs6.0/getstart.pdf eg there are commands to write images into various formats…..lots to get familiar with. What is The Unification Code – what algorithms are used? How is it put together? See Ph700-2012-Tipper pdf. MAKING IDL DO THE WORK FOR YOU Make a directory in some tidy place where it can stay. Put the attached setup.pro in it. Open it up in IDL and change the first line.to YOUR directory. Save it. Put the other *.pro files in the same directory Having set up setup.pro ............ (2) START IDL In IDL select Preferences under the File menu. (3) Click STARTUP. Click SELECT WORKING DIRECTORY and browse and select your working folder. Click SELECT STARTUP FILE and browse and select the file setup.pro (4) Click PATHS Click INSERT and browse and select your working folder Click the box in the window next to the listing of your working folder (check mark should appear) (5) Click APPLY Click SAVE Click OK - if it asks. (6) Restart IDL Now it should automatically choose the directory In the future setup.pro may contain anything you always use, loaded in at the start automatically. Neat...see attached idl-notes.pdf for the full instructions....it all worked on my toshiba. ++++++++++++++++++++++++++++++++++++++++++++++++++++ ++++++++++++++++++++++++++++++++++++++++++++ Final Code Stage: set up the working code My set up: C:\Documents and Settings\Michael\My Documents\Massiv contains Massive Code and setup.pro This new setup.pro has two added lines which make the figures appear in reverse video – black lines. Then, Massive contains massiv.pro This now displays to screen and saves a jpeg file (at the end, it dumps the window to the d****.jpg) ( display to screen set by iprint=0 in input.d. - all set up already. THE REST BELOW IS WRONG AND NEEDS UPDATING ………….. massive.pro chooses accretion rate and time from Data/inputA-accB.d where A=1,2,3,4 track parameters eg maximum accretion rate and B = accretion type eg power-law, conastant accretion,…. What it decides to do is now controlled directly from the main programme: massiv.pro This yields three lines for accretion rates 10^-3, 10^-4 and 10^-5 10^-5 Msun/year For a 100 solar mass – final stellar mass. Try it. See where diag.jpg turns up. Reminder – to try start the IDL application ( hopefully it is set to automatically run the new setup.pro) Open: massiv.pro Run massiv.pro ( compiles unify) Type unify in the lower command line. ++++++++++++++++++++++++++++++++++++++++++++ Final Stage: Research – The Issue or Problem 1. Data: use the code to calculate tracks but concentrate on getting new sets of data and reading them in. 2. Use data present but ask what if ……………….. 3. . Do Luminosity – Clump mass analysis for different accretion types. 4. Include periodic outbursts, each 1000 years, have a 100 year outburst in which most of the accretion occurs. 5. ……….