Astronomy and Astrophysics – Astrophysics – Cosmology and Extragalactic Astrophysics
Scientific paper
2010-03-19
Astronomy and Astrophysics
Astrophysics
Cosmology and Extragalactic Astrophysics
Astronomical Journal, in press. Full-resolution version available from http://www.macalester.edu/~jcannon/pubs.html
Scientific paper
We present new KPNO 0.9-m optical and VLA HI spectral line observations of the Orion dwarf galaxy. This nearby (D ~ 5.4 Mpc), intermediate-mass (M_dyn = 1.1x10^10 Solar masses) dwarf displays a wealth of structure in its neutral ISM, including three prominent "hole/depression" features in the inner HI disk. We explore the rich gas kinematics, where solid-body rotation dominates and the rotation curve is flat out to the observed edge of the HI disk (~6.8 kpc). The Orion dwarf contains a substantial fraction of dark matter throughout its disk: comparing the 4.7x10^8 Solar masses of detected neutral gas with estimates of the stellar mass from optical and near-infrared imaging (3.7x10^8 Solar masses) implies a mass-to-light ratio of ~13. New H alpha observations show only modest-strength current star formation (~0.04 Solar masses per year); this star formation rate is consistent with our 1.4 GHz radio continuum non-detection.
Cannon John M.
Haugland Kaitlin
Haynes Korey
Most Hans
Salzer John Joseph
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