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The swirling centre of NGC4261 Evelyn Caris alias Reynders Walter Jaffe (Leiden University)

The swirling centre of NGC4261 Evelyn Caris alias Reynders Walter Jaffe (Leiden University) Davor Krajnovi ć (Oxford University) ‏. Overview. Kinematics around black holes Observations and data reduction Stellar and gas kinematics Conclusions and future work. Supermassive Black Holes.

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The swirling centre of NGC4261 Evelyn Caris alias Reynders Walter Jaffe (Leiden University)

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  1. The swirling centre of NGC4261 • Evelyn Caris alias Reynders • Walter Jaffe (Leiden University) • Davor Krajnović (Oxford University)‏

  2. Overview • Kinematics around black holes • Observations and data reduction • Stellar and gas kinematics • Conclusions and future work

  3. Supermassive Black Holes Supermassive Black holes: • Found at centre of most galaxies • Its mass correlates with physical properties of host galaxy Link between the growth of the black holes and their host galaxies

  4. Supermassive Black Holes and Galaxy Formation Di Matteo, Springel and Hernquist (2005)‏

  5. Supermassive Black Holes and their Environment Urry and Padovani (1995)‏

  6. Black Hole Mass Determination • Improve Mass Estimate of Black Hole • Stars : non-circular velocities • Hot gas : high turbulent velocities • Cold gas : low turbulent velocities • Study kinematics of the cool neutral gas at the centre of the galaxy • Explore HI region with the NaI D lines seen in absorption against stars

  7. Black Hole Mass Determination • Virial Theorem:

  8. NGC4261

  9. NGC 4261 • Elliptical galaxy • Virgo cluster • Cold disk: 240 pc • Massive black hole: 4.9‧108M⊙

  10. Requirements • Na I D1 line: 5889.9 Å • Na I D2 line: 5895.9 Å • High spectral resolution: • Good seeing: 0.5'' c Stellar lines Gaseous lines

  11. Observations • Ultraviolet and VisualEchelleSpectrograph • 0.5'' slit along the major and minor axis

  12. Data Reduction Raw Data Red & major axis Reduced Data [OIII] – 5007 Å 0 4995 Å 5025 Å

  13. Sodium Only Stellar Absorption!

  14. Sodium Where are the Na I D lines due to gas absorption? • Abundance too low? • Na ionised? • Turbulence? New goal: compare the kinematics extracted from the different lines - investigate structure of the disk

  15. Stellar Kinematics Star v1 + Star v2 + Star v3 Galaxy

  16. Stellar kinematics Optimal template x Galaxy Line-of-sight velocity distribution (LOSVD)‏

  17. Stellar kinematics Penalized Pixel-Fitting Method (pPXF) (Cappellari & Emsellem, 2004)‏ • Extracts the stellar kinematics from absorption-line spectra • Finds best fit using a template stellar spectrum • Obtains the mean velocity and velocity dispersion

  18. Stellar Kinematics • Important: • Need templates representative of the galaxy stellar population: • Giant stars: HD85859, Arcturus, HD47536 • Exclude spectral regions that could be contaminated by emission lines • RedL: 2984 – 3916 Å • Emission lines : Hβ, [OIII], [NI] • Absorption lines: MgI, FeI

  19. Rotation Curves

  20. Velocity Dispersion

  21. Rotation Curves

  22. Stellar Kinematics redU

  23. 20 20

  24. Stellar kinematics

  25. Stellar kinematics

  26. Gas kinematics Gas AND Absorption Line Fitting (GANDALF) (Sarzi, FalcÓn-Barroso & Peletier, 2006)‏ • Separates the stellar continuum and gas emission in the spectra • Treats emission lines as additional Gaussian templates • Solves for the best amplitude, mean velocity and velocity dispersion

  27. Gas Kinematics

  28. Gas Kinematics Hβ [NI] [OIII]

  29. Gas kinematics

  30. Conclusions • NaI D lines seen in absorption against the stars not visible • Stellar kinematics: the emission line [NI] close to absorption line Mg probably misleads the results near the core of the galaxy • Gas kinematics: Hβ, [OIII] and [NI] derived kinematics look similar at first sight

  31. Future Work • Extract stellar and gas kinematics: • Compare the kinematics: • Minor and major axis • Emission lines e.g. [OII]/Hβ , [OIII]/[OII] • Absorption lines e.g. Mg and Na

  32. Thank you for listening!

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