Issue |
A&A
Volume 433, Number 1, April I 2005
|
|
---|---|---|
Page(s) | L1 - L4 | |
Section | Letters | |
DOI | https://doi.org/10.1051/0004-6361:200500026 | |
Published online | 14 March 2005 |
Letter to the Editor
A dwarf galaxy with a giant HI disk
1
National Centre for Radio Astrophysics, Post Bag 3, Ganeshkhind, Pune 411 007, India e-mail: ayesha@ncra.tifr.res.in
2
Special Astrophysical Observatory, Nizhnii Arkhys 369167, Russia
Received:
7
January
2005
Accepted:
1
February
2005
We present Giant Meterwave Radio Telescope (GMRT) HI 21 cm images of a nearby dwarf
irregular galaxy NGC 3741 () which show it to have a gas
disk that extends to ~8.3 times its Holmberg radius. This makes
it probably the most extended gas disk known. Our observations
allow us to derive the rotation curve (which is flat in the outer regions)
out to ~38 optical scale lengths. NGC 3741 has a dynamical mass to light
ratio of ~107 and is one of the “darkest” irregular galaxies known.
However, the bulk of the baryonic mass in NGC 3741 is in the form of gas
and the ratio of the dynamic mass to the baryonic mass (~8), falls
within the range that is typical for galaxies. Thus the dark matter halo
of NGC 3741 has acquired its fair share of baryons, but for some reason,
these baryons have been unable to collapse to form stars. A comparison
of NGC 3741's dark halo properties with those of a sample of galaxies with
well measured rotation curves suggests that if one has to reconcile the
observations with the expectation that low mass galaxies suffer fractionally
greater baryon loss then baryon loss from halos occurs in such a way
that, in the net, the remaining baryons occupy a fractionally smaller
volume of the total halo.
Key words: galaxies: dwarf / galaxies: kinematics and dynamics / galaxies: individual: NGC 3741
© ESO, 2005
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