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Planetary Nebula Research with Hexabundles

Planetary Nebula Research with Hexabundles. Warren Reid,Quentin Parker & David Frew Macquarie University / AAO / Perth Obs. Sydney, Australia 24 November, 2008. Topics Covered. Brief background to PN & their importance What we can we measure from PNe spectra

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Planetary Nebula Research with Hexabundles

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  1. Planetary Nebula Research with Hexabundles Warren Reid,Quentin Parker & David Frew Macquarie University / AAO / Perth Obs. Sydney, Australia 24 November, 2008 Hexabundle workshop Nov 24th

  2. Topics Covered • Brief background to PN & their importance • What we can we measure from PNe spectra • Need for new instrument technology • Current needs in PN research • Future requirements in PN research • Potential future role for Hexabundles in PN research Hexabundle workshop Nov 24th

  3. Why study PNe? • PNe are among the most complex, varied and fascinating of celestial phenomena…. • PNe hold the key to determining the physics and time-scales of mass loss and evolution for low to intermediate mass stars (Iben 1995). • They are also potent probes of: • nucleosynthesis processes • abundance gradients • chemical enrichment of the interstellar medium • Plasma physics • PNe also act powerful tracers of our Galaxy’s star-forming history (e.g. Maciel & Costa 2003) • They are useful kinematical probes, visible to large Galactic distances due to their rich emission line spectrum which enables accurate radial velocities. • These scientific drivers and others motivate the study of the PNe diaspora in our galaxy…. Hexabundle workshop Nov 24th

  4. Hexabundle workshop Nov 24th

  5. Basic PNe properties • Radii range from <0.02 pc to 2.5 pc for the most senile examples. • Surface brightness ranges from mag 4 /sq.arcmin to fainter than mag 18/sq.arcmin. • Broad range of excitation, dependent on Teff and luminosity of CS, and nebular diameter/morphology • Envelopes expand at 10 to 50 kms-1 • Oldest examples are 5x104 to 105 years old, but this is a very small fraction of the progenitor star’s main-sequence lifetime (typically 109 years)! • Total number in the Galaxy is estimated between 6,000 and 28,000 (out of 400 billion+ stars). Hexabundle workshop Nov 24th

  6. Spectral analysis Diagnostic emission lines in PNe Electron temperature, use [NII] l5755/l6584 Electron temperature, use [OIII] l4363/l5007 Electron density, use [SII] l6717/l6731 Electron density, use [OII] l3726/l3729 Electron density (rms) from integrated Hb flux, angular diameter, and distance Ionised mass from integrated flux, diameter, and distance. Instead, can assume mass to calculate distance (Shklovsky method) Chemical abundances from line strengths, but need to know electron temperature and density Hexabundle workshop Nov 24th

  7. Typical low res PN Spectroscopic Observations SAAO 1.9m, 300 grating 2.3m telescope DBS 300B grating 2dF 300B grating VLT FLAMES combining L2-427, L3-479 & L6-682 gratings 2dF 1200R grating AAOmega 580v grating Hexabundle workshop Nov 24th

  8. Chemical Evolution and the Weak Line Regime PN spectrophotometry can yield more than just chemical abundances. It can (potentially) allow us to trace evolution. From the central star’s position in the HR diagram, we can estimate its core mass. From the core mass and the initial mass-final mass relation, we can estimate progenitor mass. Hexabundle workshop Nov 24th

  9. Chemical Evolution and the Weak Line Regime PN spectrophotometry can yield more than just chemical abundances. It can (potentially) allow us to trace evolution. From the central star’s position in the HR diagram, we can estimate its core mass. From the core mass and the initial mass-final mass relation, we can estimate progenitor mass. And, from the pro- genitor mass, we can infer the star’s age, and thereby probe the history of chemical evolution. Hexabundle workshop Nov 24th

  10. Need for New Instrument Technology Advantages of current technology Disadvantages of current technology • Traditionally we have measured PNe using longslit or single fibre spectroscopy. This has the advantage of providing a sum of the flux for each recombination and collisionally excited line collected within the aperture. It thereby provides a high S/N per observational restraints. • Fibre spectroscopy permits up to ~380 objects to be observed simultaneously. • IFUs allow complex structure to be accurately mapped and measured. • A slit does not generally cover the entire area of a Galactic PN. • A PN observation with current fibre instrumentation covers only 2 arcsec aperture using 2dF and 1.2 arcsec aperture using FLAMES. • A PN is a complex region composing a central star, shell, winds, shocks, FLIERs and extended halos etc. Longslits and single fibres are unable to separate these complex structures. • IFUs reduce the number of objects able to be simultaneously observed. • IFUs have a set FOV. Hexabundle workshop Nov 24th

  11. Main Areas of Current PN Research • High & low resolution spectroscopic observations for object identification and measurement of emission line fluxes. • Identification of extragalactic PNe for luminosity functions, distance and mass estimates etc. • High spatial resolution mapping of emission lines for photoionisation modelling. • Need of accurate abundance estimates for metallicity mapping. • IR imaging/spectroscopy for object classification and crude abundance estimates. • Exploitation of significant new PNe discoveries in the Galaxy and LMC (eg Parker et al, 2006 Miszalski et al 2008: MASH/MASH-II and Reid & Parker, 2006: LMC) Hexabundle workshop Nov 24th

  12. Future Requirements in PN Research • High to ultra high spatial resolution mapping of emission lines. • High sensitivity spectroscopy of low surface brightness PNe and halo regions. • 3D (IFU) optical spectroscopy of galactic and extragalactic PNe. • 3D (IFU) spectroscopy in the NIR region. For the purpose of: • Hydrodynamic modelling of various regions of the nebula and halo. • To disentangle point sources and nebulae from crowded stellar fields. • Categorise the morphology of PNe, coupled with nebula abundance estimates and stellar properties. • To answer basic questions regarding formation of a PN eg. What mechanisms cause the large variety of shapes observed thus far? • To derive initial-to-final mass estimates. • To derive accurate velocities for kinematic studies. Hexabundle workshop Nov 24th

  13. Hexabundle workshop Nov 24th

  14. How Hexabundles Could Assist PN Research into the Future. • Provide IFU style 3D spectroscopy on multiple PNe over a wide and variable area. • Provide flexibility regarding the number of fibres required on individual PNe (from 69 to 397). • Allow single fibres to be deployed on other targets during the same observation (multi-tasking). • Permit high resolution spectroscopy with the ability to co-add the spectra from specific regions of the nebula to be measured. For example, if all 397 fibres in an individual bundle were co-added, the S/N gain would be a factor of 19.9. • The proposed bundles are circular, much like most PNe. • Permits the application of PSF-fitting algorithms in order to disentangle binaries, multiple star systems, varying background emission and galaxies etc. • Accurate modelling of the central star point source and its PSF. • The ability to disable fibres in the bundle which may fall on a bright, unwanted source. Hexabundle workshop Nov 24th

  15. Hexabundles could make a significant difference to unraveling chemical and kinemtatic structure in more compact PNe and their central stars when coupled with A0/good seeing on large telescopes Hexabundle workshop Nov 24th

  16. PNe in the MC’s: an excellent system for hexabundle use • LMC PNe subtend a diameter of only 3 to 14 arcsec on the sky (including the extended halos where seen-) • Current IFUs on Gemini South and VLT are excellent for detailed analysis of bright, strong emission lines into the faint halos • Emission from faint halos and highly evolved PNe must be co-added to improve S/N. • Hexabundle elements may sample larger areas of the inner nebulae and halo to be spectroscopically observed with fewer fibres on each region. This, plus the larger sky area to sample should improve S/N. LMC PN Images: HST WFPC2 clear, snapshot mode J33 SMP101 SMP83 Sa101 Hexabundle workshop Nov 24th

  17. Co-adding PNe Spectra Co-adding spectra: This example of spatial binning from PMAS at the Calar Alto 3.5m Telescope shows how the light collecting power is increased to that of a 16m telescope (Roth et al 2005 PASP 117, 620; Kelz et al. 2006 PASP 118, 129; Roth et al. 2006, IAU Symp. 234) Mean halo spectrum of NGC 3242, averaged from a total of 4547 spectra. Comparison with the middle curve illustrates the S/N gain with regard to a single spectrum (shifted by 1 unit for clarity). The bottom plot is the final sky-subtracted result. Hexabundle workshop Nov 24th

  18. Flexibility of Bundle Size Flexibility is a bonus when observing Galactic PNe followed by those in the Magellanic Clouds and beyond with the same instrument. 2.3 arcmin 1.86 arcsec NGC6826 placed at 50kpc in the LMC WFPC2 NGC6826, distance 2200 Ly Hexabundle workshop Nov 24th

  19. What size bundles will be optimum for future PN research ? An example LMC PN imaged on Gemini South using GMOS IFU. RP1679: Continuum only RP1679: Full IFU image Hexabundle workshop Nov 24th

  20. Best Hexabundle Options for PN Observations Hexabundle workshop Nov 24th

  21. Why Different Bundles for Different Telescopes? • Hexabundles need to be matched to Nyquist sampling of the best achievable angular resolution capabilities of the telescope whether AO assisted or in natural seeing. • They offer significant advantages over simple IFUs in their possibilities for focal plane sampling • Different types of hexabundle can be combined according to requirements eg low sampling rates on the CSPN and higher on the surrounding shells and halos. • Interesting configurations possible with placement of multi-bundle groupings Hexabundle workshop Nov 24th

  22. Conclusions • Hexabundles will greatly assist PN research by providing multiple pointings over strategic areas of the central star, inner shell, shock fronts and faint outer halos of more compact Galactic and Magellanic Cloud PNe. • It will be able to sample equally in all directions away from the central star. • Spectra from faint regions can be co-added in order to improve S/N and measure faint lines of great diagnostic value. Hexabundle workshop Nov 24th

  23. Examples of New Large very low surface brightness MASH-II PNe: BMP1808-1406: Diameter ~470 arcsec High [NII]/Hα ratio Blue Central Star Hexabundle workshop Nov 24th

  24. How can we obtain sufficient S/N for such objects? Conventional IFU’s better than hexabundles for large extended Low surface brightness objects Need to co-add large-numbers of spaxels from large IFU’s Hexabundle workshop Nov 24th

  25. Hexabundle workshop Nov 24th

  26. Advantages over IFUs • 2dF type fibre positioners can be used to place hexabundles or hexabundle bundles into interesting configurations across extended PNe according to objects shape  • Current hexabundle core sizes ~ 50-150microns but can be adapted to suit requirements • Cross talk is low < 0.05 dB – potentially less lossy • Wide variety of individual hexabungle formats possible: ~ 1×91, 1×127 Hexabundle workshop Nov 24th

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