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HI in the Interacting Pair NGC 4618/4625

HI in the Interacting Pair NGC 4618/4625. Stephanie J. Bush Case Western Reserve University. Why neutral hydrogen? we can observe it! often more extended and possibly more massive distributions than stars more sensitive to interactions. What's so exciting?.

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HI in the Interacting Pair NGC 4618/4625

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  1. HI in the Interacting Pair NGC 4618/4625 Stephanie J. Bush Case Western Reserve University

  2. Why neutral hydrogen? we can observe it! often more extended and possibly more massive distributions than stars more sensitive to interactions What's so exciting? • Why do we care about NGC 4618/4625? • intermediate masses • lopsided galaxies • Interactions

  3. Objectives • We hope to calculate: • spatial distribution • masses • rotation curves • Interaction history

  4. HI Detection 101 • HI gives off radio emission with a 21 cm wavelength • Higher column density HI gives off more emission • Doppler shift gives velocities • Can display channels as a movie or as a sum http:///burro.cwru.edu/Academics/Astr222/Galaxy/Structure/gas.html So how about some data?

  5. A quick optical glimpse... Sloan Digital Sky Survey

  6. Total HI distribution

  7. NGC 4618 Spatial Analysis • Intensity vs. radius plots • Adopting 6 Mpc distance and effective radii (Odewahn 1991) we find... • Extent • 4618: 4 x effective radii • 4625: 9 x effective radii • HI mass • 4618: (5.3 +/- 0.6) x 108 Msun • 4625: (3.9 +/- 0.6) x 108 Msun NGC 4625

  8. Dynamical Analysis:Velocity Field

  9. Dynamical Analysis:Rotation Curve for NGC 4618 Preliminary Dynamical Mass: 4.1 x 109 M sun

  10. Dynamical Analysis:Rotation Curve for NGC 4625 Preliminary dynamical mass: 8.2 x 108 Msun

  11. Future work(Preferably, in the next week...) • Dynamical masses with more detailed halo models, perhaps including a disk model • Interaction history: • What constraints can we put on the galaxies being bound or unbound? • If they are bound what will the merger remnant look like? • Compare with other pairs of galaxies (perhaps NGC 672 - IC 1727) to find trends.

  12. References • Odewahn, S. C. 1991, AJ, 101, 829.

  13. Acknowledgments • Dr. Eric Wilcots • Dr. Bob Benjamin • The first year grad student office (ok, ok, no pixels!) • Kiwi Davis and Adrienne Stilp • the bug graveyard survivors • the NSF

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