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 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 5996
NGC 6021
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? Unknown classification in NED, found in 2MASS survey SBm
CGCG
M(HI) = 1.4e9
Mdyn = 7.5e9
Arms?
Unknown classification in NED,
found in 2MASS survey
M(HI) = 9.7e8
Mdyn = 4.5e9
UGC 10805
SBm

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

8. Mass Ratios
Target Name
Morphology
Mdyn/M(HI)
UGC 10805
Sbm
4.56
CGCG
unknown
5.2
NGC 5996
Sbc stbur
16.3
UGC 10841
Sdm
23.9
UGC 10281
SB(s)m
59.8
IC 1135 Sa
233
NGC 6021 E
1390
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!