High Resolution HI Mapping of NGC 4038/9 (``The Antennae")
and its Tidal Dwarf Galaxy Candidates
We present new VLA C+D-array HI observations and optical and NIR
imaging of the well known interacting system NGC 4038/9, ``The
Antennae''. At low spatial resolution (~40"), the radio data
reach a limiting column density of ~1E19 cm^-2 (2.5sigma),
providing significantly deeper mapping of the tidal
features than afforded by earlier HI maps. At relatively high
spatial resolution (~10"), the radio data reveal a wealth of
gaseous sub-structure both within the main bodies of the galaxies and
along the tidal tails. In agreement with previous HI studies, we
find that the northern tail has HI along its outer length, but none
along its base. We suggest that the HI at the base of this tail has
been ionized by massive stars in the disk of NGC 4038. The gas in the
southern tail has a bifurcated structure, with one filament lying
along the optical tail and another running parallel to it but with no
optical counterpart. The two filaments join just before the location
of several star forming regions near the end of the tail. The HI
velocity field at the end of the tail is dominated by strong velocity
gradients which suggest that at this location the tail is bending away
from us. We delineate and examine two regions within the
tail previously identified as possible sites of a so-called "tidal
dwarf galaxy'' condensing out of the expanding tidal material. The
tail velocity gradients mask any clear kinematic signature of a
self-gravitating condensation in this region. A dynamical analysis
suggest that there is not enough mass in gas alone for either of these
regions to be self-gravitating. Conversely, if they are bound they
require a significant contribution to their dynamical mass from
evolved stars or dark matter. Even if there are no distinct dynamical
tidal entities, it is clear that there is a unique concentration of
gas, stars and star forming regions within the southern tail: the HI
channel maps show clear evidence for a significant condensation near
the tail star forming regions, with the single-channel HI column
densities higher than anywhere else in the system, including within
the main disks. Finally, the data reveal HI emission associated with
the edge-on "superthin" Scd galaxy ESO 572-G045 that lies just
beyond the southern tidal tail of The Antennae, showing it to be a
companion system.
Go here for more figures on NGC 4038/9
Versions and Color GIFs of Figures
- AJ PDF (7.0 MB)
- Fig1: low-res HI + DSS; HI on low-res optical
(gif)
- Fig2: C+D array global mom0+opt, B-R, mom1, mom2 Mosaic:
(gif)
- Fig3: P-V plot:
(gif)
- Fig4: 40" global Channel maps HI on opt:
(gif)
- Fig5: R+1 Channel maps greys:
(gif)
(ps.gz)
- Fig6: TDG mom0, B-R, mom1, mom2 Mosaic: (gif)
- Fig7: MHI(r), Lb(r) for TDGs
(gif)
(ps.gz)
- Fig8: TDG Channel Maps:
(gif)
(ps.gz)
- Fig9: Disk B+mom0, K+mom0, B-K+mom0, mom0+K, mom1, mom2 Mosaic:
first 4 panels (gif)
next 2 panels (gif)
- Fig10: R=1 disk Channel maps:
(gif)
- Fig11: Companion MOM0 + DSS:
(gif)
- Fig12: TDG Mlum(r)/Mdyn(r) analysis
(gif)
(ps.gz)
Last modified: Sun Feb 27 14:08:28 EST 2005
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