HI in the Interacting Pair NGC 4618/4625 Stephanie J. Bush Case Western Reserve University What's so exciting? Why do we care about NGC 4618/4625?
Why neutral hydrogen? intermediate masses we can observe it!
lopsided galaxies Interactions often more extended and
possibly more massive distributions than stars more sensitive to interactions Objectives We hope to calculate:
spatial distribution masses rotation curves
Interaction history 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?
A quick optical glimpse... Sloan Digital Sky Survey Total HI distribution 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 Dynamical Analysis: Velocity Field Dynamical Analysis: Rotation Curve for NGC 4618
Preliminary Dynamical Mass: 4.1 x 109 M sun Dynamical Analysis: Rotation Curve for NGC 4625 Preliminary dynamical mass: 8.2 x 108 Msun 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.
References Odewahn, S. C. 1991, AJ, 101, 829. 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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