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Observations of Extragalactic Neutral Hydrogen

Observations of Extragalactic Neutral Hydrogen. Spencer Wolfe Kristina Nyland Laura Trouille Blakesley Burkhart Robert Minchin. Why observe the 21 cm line in other galaxies?. Center of line provides recessional velocity of galaxy provides distance to galaxy (if unknown) Width of line

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Observations of Extragalactic Neutral Hydrogen

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  1. Observations of Extragalactic Neutral Hydrogen Spencer Wolfe Kristina Nyland Laura Trouille Blakesley Burkhart Robert Minchin

  2. Why observe the 21 cm line in other galaxies? • Center of line • provides recessional velocity of galaxy • provides distance to galaxy (if unknown) • Width of line • provides rotational velocity of the galaxy • provides dynamical mass of the galaxy • Total flux in HI line • provides HI mass of the galaxy • probes correlations with optical galaxy morphology, dynamical mass, IR flux, and variations with redshift Above: The Circinus spiral galaxy mapped in HI by the ATCA. The left and right sides represent (respectively) the moment 0 (integrated flux) and the moment 1 (velocity).

  3. Instrument Set-up • L-band receiver (centered at 1420.406 MHz) • Filter at 1370-1470 MHz • Backend: WAPP correlator (25-50 MHz) • Standard on/off observing mode • 8 galaxies observed in 2 hours • all galaxies chosen w/ velocities < 10,000 km/s • 300 sec integration time per target

  4. Let’s Play ‘Guess the Profile’ NGC 6021 NGC 5996 Spiral (SBc, starburst) Elliptical First 21-cm detection of NGC 6021 !

  5. UGC 10281, SB(s)m, z~0.03 M(HI) = 3.8e8 Mdyn = 2.3e10

  6. Arms? CGCG 082-035 M(HI) = 1.4e9 Mdyn = 7.5e9 Unknown classification in NED, found in 2MASS survey M(HI) = 9.7e8 Mdyn = 4.5e9 UGC 10805 SBm

  7. M(HI) = 1.4e9 Mdyn = 4.7e10 UGC 10841 Sdm M(HI) = 3.6e8 Mdyn = 8.5e10 IC 1135 Sa i=30 deg

  8. Mass Ratios 1) HI in looser spirals tends to account for a greater portion of their total mass. 2) Tighter spiral and elliptical have a lower fraction of HI compared to their total mass. 3) This supports the general view of spiral vs elliptical galaxy characteristics.

  9. Acknowledgements We would like to thank Robert Minchin for his help with observing and reducing our data. Thanks Robert!

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