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Interaction in the NGC 3079 group

Interaction in the NGC 3079 group. Nebiha Shafi University of Witwatersrand and HartRAO. Supervisors: Prof. Roy Booth (HartRAO) Dr. Raffaella Morganti Dr. Tom Oosterloo (ASTRON). Bursary and Fellowship Conference 2009. Outline.

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Interaction in the NGC 3079 group

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  1. Interaction in the NGC 3079 group Nebiha Shafi University of Witwatersrand and HartRAO Supervisors: Prof. Roy Booth (HartRAO) Dr. Raffaella Morganti Dr. Tom Oosterloo (ASTRON) Bursary and Fellowship Conference 2009

  2. Outline • Introduction to the primary source • Observation & Data reduction • Results • Interaction in the NGC 3079 group • Summary & Future work N. Shafi Bursary and Fellowship Conference 2009

  3. The primary Source NGC 3079 Type: SB(s)c RA: 10 01 57.8 DEC: +55 40 47 Inclination: ~ 84o Velocity: ~ 1116 km s-1 Distance: ~ 16 Mpc • Host to a nuclear starburst and an AGN. • Classified as Seyfert2. • Displays 2 extended radio lobes. • Rapid ionized gas outflow up to 1000 km s-1. HST image N. Shafi Bursary and Fellowship Conference 2009

  4. Observation & Data reduction Observations: The data cube Telescope: WSRT Bandwidth: 20 MHz Frequency : 1.42 GHz Integration time: 5 x 12 hrs Velocity resolution: 16 km s-1 • Data reduction: MIRIAD • Standard reduction • Non-Standard reduction • “Peeling” Beam size: 47″.5 x 44″.7 Rms noise: 0.18 mJy beam-1‏ N. Shafi Bursary and Fellowship Conference 2009

  5. Interaction in the NGC 3079 group: The NGC 3079 Group Total HI contours overlaid on DSS2 image MCG 9-17-9 NGC 3073 N – new redshift information N. Shafi Bursary and Fellowship Conference 2009

  6. Interaction Scenarios • Ram pressure • The ram pressure required to strip off gas from a galaxy as it moves in the intergalactic medium (IGM) : Where ρ - the density of the IGM G - gravitational constant v - the velocity dispersion of the group Σ∗ and ΣHI are the stellar and gas surface mass densities (Gunn & Gott 1972) ρv2 ≥ 2πGΣ∗ ΣHI Gravitational restoring force Force due to IGM N. Shafi Bursary and Fellowship Conference 2009

  7. Interaction Scenarios • Tidal interaction • The strength of the tidal force on a galaxy can be inferred from the tidal radius (Jacobi limit): (Binney & Tremaine 1987) rJ = Rsep ( m /3M )1/3 Where rJ - radius in which material remain bound to one galaxy m- mass of the companion M - mass of the primary galaxy Rsep - the separation between the two galaxies • Disruption happens at radius r> rJ (r - size of the companion) N. Shafi Bursary and Fellowship Conference 2009

  8. Total HI overlaid on DSS2 red image contoursof 0.2, 1, 5,10, 20, 50 100 x 1019 cm-2 contours in steps of 3σ MCG 9-17-9: Tidal or Ram pressure stripped? MCG 9-17-9 HI bridge A third tail? N. Shafi Bursary and Fellowship Conference 2009

  9. Problems with tidal scenario 1 . At the projected distance of 30 kpc between the two galaxies, NGC 3079 and MCG 9-17-9 the tidal radius is: rJ ∼ 8 kpc And the size of MGC 9-17-9 is: r ∼ 5 kpc 1018 cm -2 6x1020 cm -2 2. The lack of any disturbance sign in the optical disk of the galaxy N. Shafi Bursary and Fellowship Conference 2009

  10. IS MCG 9-17-9 being ram pressure stripped? Assuming ΣHI/Σ∗ = constant, theminimum ram pressure required to strip off gas from MCG 9-17-9 (for NH at half-maximum) is: ρv2 ≥ 6.9x10 -12 dyn cm-2 • Ram pressure due to the super-wind or the hot X-ray halo of NGC 3079? 1. Ram pressure due to the super-wind from NGC 3079: N. Shafi Bursary and Fellowship Conference 2009

  11. 2. Ram pressure due to the hot X-ray halo of NGC 3079: • Lx ∼ 6 × 1039 erg/s and extends 13-17 kpc • (Cecil et al. 2002). • Assuming T= 3.5 × 106 K • gives an electron density of : • ne = 7 × 10− 4 cm−3 • This yields a ram pressure: • ρv2 =2.4 × 10− 11 dyn cm−2 (Breitschwerdt et al. 2002) N. Shafi Bursary and Fellowship Conference 2009

  12. The case of NGC 3073: • What is the origin of the ‘Cometary’ appearance? Tidal or ram pressure? N. Shafi Bursary and Fellowship Conference 2009

  13. Problems with tidal scenario 1 . At the projected distance of 50 kpc between the two galaxies, NGC 3079 and NGC 3073 the tidal radius is: rJ ∼ 10 kpc And the size of NGC 3073is: r ∼ 7.5 kpc 2.5x1020 cm -2 1018 cm -2 2. The lack of any disturbance sign in the optical disk of the galaxy. N. Shafi Bursary and Fellowship Conference 2009

  14. Ram pressure due to the super-wind or X-ray halo of NGC 3079? • The minimum ram pressure required to strip off gas from NGC 3073 (for NH half-maximum) is: • ρv2 ≥ 9x10 -14 dyn cm-2 1. Ram pressure due to the hot X-ray halo of NGC 3079: N. Shafi Bursary and Fellowship Conference 2009

  15. 2. Ram pressure due to the super-wind of NGC 3079: • Adopting the lower limit for the electron density and the velocity of the super-wind from Cecil et al. (2001): • ne = 1.35 × 102 cm−3 , and V ~1000 km s−1 • Considering density decline as a function of distance gives a ram pressure of: • ρv2 ~ 3.6 × 10− 8 dyn cm−2 N. Shafi N. Shafi Dec 2009 Bursary and Fellowship Conference 2009

  16. Summary& future work • Five new galaxies associated with NGC 3079 group were revealed. • Two of the companion galaxies, MCG 9-17-9 and NGC 3073 seem to be ram pressure stripped due to the hot X-ray halo and super-wind of NGC 3079 respectively. • Investigate the effect of the interaction on the individual companion galaxies. • Study the role of the companions in the nuclear activity of NGC 3079. N. Shafi Bursary and Fellowship Conference 2009

  17. Thank you!

  18. Results • HI emission • Much extended HI emission than previous observations. • Five new companion galaxies were revealed. • Asymmetric HI disk. • Extraplanar HI. • Interaction with three companions. • HI Absorption • Broad and strong central absorption with a hint of blue shifted absorption detected. N. Shafi Dec 2009

  19. > 600 km s-1 Vsys Hi absorption • Broad and strong central absorption with a hint of blueshifted component blue-shifted? τpeak= 0.18

  20. Model Thin disk Thick disk slow rotating halo TiRiFiC (Jozsa et al. 2007) • Free parameters: SBR VROT PA INCL • Constant parameters: Z0 XPOS YPOS VSYS DISP N. Shafi Oct 2009

  21. The results of the models • Data • Thin disk • Thick disk N. Shafi Oct 2009

  22. NGC3079 NGC 891 Oosterloo et al. 2007

  23. Data reduction- Miriad • Non-Standard reduction • Standard reduction After “Peeling” The result of the standard reduction ← Need different calibration for different direction -- “peeling” N. Shafi Oct 2009

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