<html><head><meta http-equiv="Content-Type" content="text/html charset=us-ascii"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>Hi everyone,</div><div><br></div><div>I think there is a small error in the angular momentum calculation.</div><div><br></div><div>Below, L is calculated as:</div><div><br></div><div>L = velocity x radius</div><div><br></div><div>def _SpecificAngularMomentumX(field, data):</div><div> xv, yv, zv = obtain_velocities(data)</div><div> rv = obtain_rvec(data)</div><div> return yv*rv[2,:] - zv*rv[1,:]</div><div>def _SpecificAngularMomentumY(field, data):</div><div> xv, yv, zv = obtain_velocities(data)</div><div> rv = obtain_rvec(data)</div><div> return -(xv*rv[2,:] - zv*rv[0,:])</div><div>def _SpecificAngularMomentumZ(field, data):</div><div> xv, yv, zv = obtain_velocities(data)</div><div> rv = obtain_rvec(data)</div><div> return xv*rv[1,:] - yv*rv[0,:]</div><div><div><br></div><div><br></div><div>but it should be:</div><div><br></div><div>L = radius x velocity</div><div><br></div><div>This leads to a sign error (and gives me a whole load of retrograde GMCs!)</div></div><div><br></div><div><div><br></div><div>def _SpecificAngularMomentumX(field, data):</div><div> xv, yv, zv = obtain_velocities(data)</div><div> rv = obtain_rvec(data)</div><div> return zv*rv[1,:] - yv*rv[2,:]</div><div>def _SpecificAngularMomentumY(field, data):</div><div> xv, yv, zv = obtain_velocities(data)</div><div> rv = obtain_rvec(data)</div><div> return -(zv*rv[0,:] - xv*rv[2,:])</div><div>def _SpecificAngularMomentumZ(field, data):</div><div> xv, yv, zv = obtain_velocities(data)</div><div> rv = obtain_rvec(data)</div><div> return yv*rv[0,:] - xv*rv[1,:]</div></div><div><br></div><div><br></div><div>Does that look right?</div><div><br></div><div><br></div><div>Elizabeth</div><div><br></div><div><br></div><br><br><div>
<span class="Apple-style-span" style="border-collapse: separate; color: rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: none; white-space: normal; widows: 2; word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div><div>------------------------------------------------------</div><div>Elizabeth TASKER</div><div>Assistant Professor</div><div><br></div><div>Physics Department, Faculty of Science</div><div>Hokkaido University</div><div><br></div><div>Sapporo, Japan</div><div><br></div><div><a moz-do-not-send="true" href="mailto:tasker@astro1.sci.hokudai.ac.jp" target="_blank">tasker@astro1.sci.hokudai.ac.jp</a></div><div><a moz-do-not-send="true" href="http://astro3.sci.hokudai.ac.jp/%7Etasker/" target="_blank">http://astro3.sci.hokudai.ac.jp/~tasker/</a></div><div><div>------------------------------------------------------</div></div></div><div><br></div></span><br class="Apple-interchange-newline">
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