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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
• 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).
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
Let’s Play ‘Guess the Profile’
NGC 5996
NGC 6021
Spiral (SBc, starburst)
Elliptical
First 21-cm
detection of
NGC 6021 !
UGC 10281, SB(s)m, z~0.03
M(HI) = 3.8e8
Mdyn = 2.3e10
CGCG 082-035
M(HI) = 1.4e9
Mdyn = 7.5e9
Arms?
Unknown classification in NED,
found in 2MASS survey
UGC 10805
SBm
M(HI) = 9.7e8
Mdyn = 4.5e9
UGC 10841
M(HI) = 1.4e9
Mdyn
= 4.7e10
Sdm
IC 1135
Sa
i=30 deg
M(HI) = 3.6e8
Mdyn = 8.5e10
Mass Ratios
Target Name
Morphology
Mdyn/M(HI)
UGC 10805
Sbm
4.56
CGCG082-035
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.
Acknowledgements
We would like to thank Robert Minchin for his
help with observing and reducing our data.
Thanks Robert!