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Advisor: Robin Ciardullo George Jacoby, John Feldmeier, Pat Durrell

N. King, KPNO, NOAO, NSF, 4-m Mayall Telescope. W. Keel, KPNO, 4-m Mayall Telescope. W. Keel, KPNO, 4-m Mayall Telescope. Planetary Nebula Studies of Face-On Spiral Galaxies: Is the Disk Mass-to-Light Ratio Constant?. Advisor: Robin Ciardullo George Jacoby, John Feldmeier, Pat Durrell.

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Advisor: Robin Ciardullo George Jacoby, John Feldmeier, Pat Durrell

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  1. N. King, KPNO, NOAO, NSF, 4-m Mayall Telescope W. Keel, KPNO, 4-m Mayall Telescope W. Keel, KPNO, 4-m Mayall Telescope Planetary Nebula Studies of Face-On Spiral Galaxies: Is the Disk Mass-to-Light Ratio Constant? Advisor: Robin Ciardullo George Jacoby, John Feldmeier, Pat Durrell Kimberly Herrmann July 2nd, 2005 Penn State 1/15

  2. (Modified from Carroll & Ostlie 1996) HALO DISK (Astronomy Today, Chaisson & McMillan) Why study Disk Mass-to-Light Ratios? • Dark Matter Halos • Assume a constant Disk Mass-to-Light Ratio • Disk Distribution of Mass 2/15

  3. VLT ANTU + FORS1, ESO VLT ANTU + FORS1, ESO Our Project: PNe kinematics & Disk Mass The orbits of old disk stars will oscillate in z according to z = the velocity dispersion inz (R) = the disk mass surface density z0 = the disk scale height • Since • a disk’s surface brightness declines exponentially with radius, R • spiral disks are supposed to have a constant M/L • zshould decline exponentially with R 3/15

  4. HALO DISK (Modified from Carroll & Ostlie 1996) Why use PNe to study Spiral Disks? • PNe are found in outer regions • Easier than absorption line spectroscopy • Representative of old galactic disk • Easy to find ([O III] l5007 emission) • 1st step: Photometry • PNLF gives distance • Precise spectroscopic velocities (~2 km s-1) • 2nd step: Spectroscopy 4/15

  5. How do we find PNe? • Image the galaxy in several filters: [O III] 5007 (50 Å FWHM) Harris V H + [N II] (75 Å FWHM) 5/15

  6. How do we find PNe? • Image the galaxy in several filters: • Blinking Method • Find objects clearly on-band but not off-band • Eliminate H II region, SN contaminants • Determine locations (RA & dec) & magnitudes • Need follow-up spectroscopy to get velocities 5/15

  7. Candidate PNe 152 candidates in M33 6/15

  8. 242 candidates in M83 6/15

  9. 65 candidates in M101 6/15

  10. PNe Spectroscopy • Observations • Use HYDRA with WIYN (or 4 m at CTIO) • Multiple setups with 30-45 min exposures • Target as many PNe as many times as possible • Also target the blank sky, some miscellaneous objects, and random positions • Typical Spectral Reduction • Using IRAF: dohydra, bias subtraction, flat fielding, wavelength calibration, sky subtraction, combining multiple setups, barycentric & systemic velocity corrections • Extra concentration on wavelength calibration 7/15

  11. Resulting Velocities 140 velocities in M33 8/15

  12. -66.6 > v > -110 km/s -33.3 > v > -66.6 km/s 0 > v > -33.3 km/s 33.3 > v > 0 km/s 66.6 > v > 33.3 km/s 131 > v > 66.6 km/s ~190 velocities in M83 8/15

  13. 47 velocities in M101 (so far) 8/15

  14. Subtracting out Rotation 9/15

  15. Velocity Dispersion 10/15

  16. Velocity Ellipsoid • Epicyclic Approximation • Separate rotation from perpendicular oscillations • Maximum Likelihood Method • Determine which combinations of sz & sR are most likely • Toomre stability • A thin disk is stable against axisymmetric perturbations • Morosov stability • A thin disk is stable against the formation of a bar 11/15

  17. Scale length > twice the K band scale length! M/LV increases by a factor of 5 through the disk (not constant!) sR must turn down in center- otherwise sR > vR sz/sR(R) agrees with numerical models M33 Results 12/15

  18. Possible Problems • Possible H II region contaminants • Wrong value of scale height, z0 • Radial gradient in the scale height • Systematic extinction due to dust • Breakdown of isothermal disk approximation at large radii • Breakdown in stability arguments • (Mostly because of a sample of one) 13/15

  19. Conclusions • PNe are useful for studying galactic dynamics • They are easy to find & have good spectroscopic precision • Dispersion needs to be decomposed • Velocity dispersion in z (sz) shows exponential decay • For M33: the disk mass-to-light ratio is not constant throughout the disk • Need more spiral galaxies… 14/15

  20. J. Cuillandre. CFHT King, KPNO/NOAO/NSF, Mayall Teles VLT ANTU + FORS1, ESO A. Block, NOAO/AURA/NSF GMOS Team, Gemini T. Rector, Gemini/AURA M83: Finishing spectral analysis Stay Tuned! M33: Done! M101: Finishing spectral analysis M74: Granted time for imaging in Nov M94: Images obtained NGC 6946: Images obtained 15/15

  21. Eliminating H II Regions

  22. Velocity Ellipsoid • Epicyclic Approximation: • Maximum Likelihood Method • Determine probability for every combination of possible sz and sR • 0 < sz < 100 km s-1, 0.25 < sz/sR < 1.0 • Toomre (Morosov) stability

  23. P(PN) Maximum Likelihood Method • Determine probability for every combination of possible sz and sR • 0 < sz < 100 km s-1, 0.25 < sz/sR < 1.0 • For each bin: • Consider a sz and a sR • For each PN in the bin determine s2rotand s2res

  24. Toomre/Morosov Stability A thin stellar disk is stable against axisymmetric perturbations if where k (the epicyclic frequency) is The disk is stable against non-axisymmetric perturbations if The isothermal approximation can be used to show this is

  25. Epicyclic Frequency

  26. Collisionless Boltzmann Equation with Jeans Equation & symmetry & small asymmetric drift Epicyclic Approximation

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