2,116 research outputs found
News from the "Dentist's Chair": Observations of AM 1353-272 with the VIMOS IFU
The galaxy pair AM 1353-272 nicknamed "The Dentist's Chair" shows two ~30 kpc
long tidal tails. Previous observations using multi-slit masks showed that they
host up to seven tidal dwarf galaxies. The kinematics of these tidal dwarfs
appeared to be decoupled from the surrounding tidal material. New observations
of the tip of the southern tidal tail with the VIMOS integral field unit
confirm the results for two of these genuine tidal dwarfs but raise doubts
whether the velocity gradient attributed to the outermost tidal dwarf candidate
is real. We also discuss possible effects to explain the observational
difference of the strongest velocity gradient seen in the slit data which is
undetected in the new integral field data, but arrive at no firm conclusion.
Additionally, low-resolution data covering most of the two interacting partners
show that the strongest line emitting regions of this system are the central
parts.Comment: Comments welcome, especially ideas to explain the difference between
the two datasets. 5 pages, 3 figures, to appear in "Science Perspectives for
3D Spectroscopy", eds. M. Kissler-Patig, M. M. Roth and J. R. Walsh, ESO
Astrophysics Symposi
Detection and Mapping of Decoupled Stellar and Ionized Gas Structures in the Ultraluminous Infrared Galaxy IRAS 12112+0305
Integral field optical spectroscopy with the INTEGRAL fiber-fed system and
HST optical imaging are used to map the complex stellar and warm ionized gas
structure in the ultraluminous infrared galaxy IRAS 12112+0305. Images
reconstructed from wavelength-delimited extractions of the integral field
spectra reveal that the observed ionized gas distribution is decoupled from the
stellar main body of the galaxy, with the dominant continuum and emission-line
regions separated by projected distances of up to 7.5 kpc. The two optical
nuclei are detected as apparently faint emission-line regions, and their
optical properties are consistent with being dust-enshrouded weak-[OI] LINERs.
The brightest emission-line region is associated with a faint (m_{I}= 20.4),
giant HII region of 600 pc diameter, where a young (about 5 Myr) massive
cluster of about 2 10 dominates the ionization.
Internal reddening towards the line-emitting regions and the optical nuclei
ranges from 1 to 8 magnitudes, in the visual. Taken the reddening into aacount,
the overall star formation in IRAS 12112+0305 is dominated by starbursts
associated with the two nuclei and corresponding to a star formation rate of 80
yr.Comment: 2 figures, accepted to Ap.J. Letter
Ionization processes in a local analogue of distant clumpy galaxies: VLT MUSE IFU spectroscopy and FORS deep images of the TDG NGC 5291N
We present IFU observations with MUSE@VLT and deep imaging with FORS@VLT of a
dwarf galaxy recently formed within the giant collisional HI ring surrounding
NGC 5291. This TDG-like object has the characteristics of typical z=1-2
gas-rich spiral galaxies: a high gas fraction, a rather turbulent clumpy ISM,
the absence of an old stellar population, a moderate metallicity and star
formation efficiency. The MUSE spectra allow us to determine the physical
conditions within the various complex substructures revealed by the deep
optical images, and to scrutinize at unprecedented spatial resolution the
ionization processes at play in this specific medium. Starburst age, extinction
and metallicity maps of the TDG and surrounding regions were determined using
the strong emission lines Hbeta, [OIII], [OI], [NII], Halpha and [SII] combined
with empirical diagnostics. Discrimination between different ionization
mechanisms was made using BPT--like diagrams and shock plus photoionization
models. Globally, the physical conditions within the star--forming regions are
homogeneous, with in particular an uniform half-solar oxygen abundance. At
small scales, the derived extinction map shows narrow dust lanes. Regions with
atypically strong [OI] emission line immediately surround the TDG. The [OI] /
Halpha ratio cannot be easily accounted for by photoionization by young stars
or shock models. At larger distances from the main star--forming clumps, a
faint diffuse blue continuum emission is observed, both with the deep FORS
images and MUSE data. It does not have a clear counterpart in the UV regime
probed by GALEX. A stacked spectrum towards this region does not exhibit any
emission line, excluding faint levels of star formation, nor stellar absorption
lines that might have revealed the presence of old stars. Several hypotheses
are discussed for the origin of these intriguing features.Comment: 13 pages, 15 figures, accepted for publication in A&
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