3D OPTICAL OBSERVATIONS OF
BLUE COMPACT DWARF GALAXIES
.
1
1
1
2
C. Muñoz-Tuñón , B.García-Lorenzo , L.M. Cairós , A. Moiseev and
1
1
3
3
I.Martinez-Delgado , V. Melo , S. Silich , and G. Tenorio-Tagle
gotzon
18-1-95
.
(1) Instituto de Astrofísica de Canarias, Tenerife, Spain
(2) Special Astrophysical Observatory, Russia
(3) INAOE, Puebla, Mexico
Introduction
We aim to understand the nature and evolution of the
star formation process in BCDs. BCDs are morphologically
complex objects, which usually show several knots of star
formation scattered all over the galaxy, are ideal objects
for two dimensional observational techniques (spatial and
spectroscopic data sets). Most studies of BCDs have been
done using traditional set-ups (imaging and long-slit
spectroscopy). 3D optical techniques allow recording
spatial and spectral information simultaneously, allowing
to study the kinematical state of the starburts knots, their
physical conditions to writing the star formation history of
BCDs. Like this, the fate of processed matter as well as
the feedback mechanisms can be addressed.
Fabry-Perot interferometry, where larger spatial fields of
view and higher spectral resolutions can be achieved,
are ideal for kinematics. INTEGRAL allows the mapping
of the physical parameters.
In this poster, we present as an example, the comparison
of Fabry-Perot and Integral field spectroscopy of IIIZw102
pointing out the advantages and limitations of both
techniques, which turn out to be complementaries.
Observations
III Zw102 was observed on the 6m telescope , (SAO,
RAS) with the scanning interferometer Fabry-Perot
ITF, installed in the focal reducer SCORPIO.
The detector was the EEV 42-40, and the field of view
INTEGRAL field spectroscopy of IIIZw102 has been
6 arcmins, with a pixel size about 0.70 arcsec.
obtained at the 4.2 m William Herschell Telescope at
the Observatorio del Roque de los Muchachos on the The IFP spectral resolution was FWHM 1 A, and FSR
island of La Palma (Spain) (see Arribas et al. 1998 for a detail about 13 A dividel in 33 channels (17km/sec per
channel) in Ha . The total exposure time was
description of INTEGRAL).
36 x 180 sec .The seeing around 1.4-1.8 arcsec.
The spectrograph was equipped with a grating of
600 groove/mm, and a Tek6 CCD array of 1124 x 1124
pixels of 24 microns size was used. The spectral range The interferometric observations were reduced using
an IDL-based software (Moiseev A.V. 2002). After
coverage was 4390-7450Å giving a linear dispersion
primary reductions (bias, flat-fielding etc ...) removing
of about 3 Å. The observed spectral range includes
the night-sky emission lines and converting to the
Ha , [OIII], Hb, [NII], and [SII] emission lines.
wavelength scale, the data are presented as datacubes
(512,512,36). The ionized gas velocity fields, the maps
of the gas velocity dispersion and fluxes in Ha and
Main Advantages
Disadvantages
[NII] lines were constructed by means of a Gaussian
Large Spatial Coverage Sequential
Fabry Perot Spectral resolution
Small Spectral range
fitting of the line profiles.
INTEGRAL
Simultaneity
Spectral coverage
Continuum Maps
Figure 1A: Continuum map of IIIZw102
from our F-P observations.
Spatial coverage
Spectral resolution
Emision Line Maps
Figure 1B: IIIZw102 continua recovered from IFS
data and color maps .
Figure 2A: IIIZw102 Há map from our Fabry Figure 2B: IIIZw102 line intensity maps of [OIII] and
Perot data
Há derived by fitting a gaussian to these lines. The
ionization and extinction maps are also plotted.
Continuum maps obtained from Fabry Perot observations allows to study in detail
the morphological structure of the object. Morphological features can be compared
and connected to any kinematic perturbation present in the velocity field.
From Integral spectroscopy we can reconstructed (from individual spectra) continuum
maps at different bands. Combining these continua, colour maps can be obtained. As
in traditional filter image, we can study dust extinction and/or stellar populations.
High resolution intensity line maps can be derived from Fabry Perot observations.
This allow a proper identification of the different star formation knots and the option
of find possible extended emission structures such us bubbles.
High and low ionization gas can be study from Integral observations. Therefore,
ionization maps can be derived from these data. Moreover, extinction maps can also
be recovered from Balmer emission lines.
In the case of IIZw102, continuum map obtained from our Fabry Perot data reveals a
well defined optical nucleus. Colour map derived from Integral data shows a ring
morphology.
For IIIZw102, several knots of star formation have been identify in the central region
of the galaxy. Extinction peaks in the Ha /Hb map are shifted respect to the emission
peaks.
Ongoing and future work:
Kinematics
Ten BCDs have already been observed in FP mode. The data
have been reduced and we are currently working in the data
analysis.
Similarly, we have 6 BCDs observed with integral, which have
been also reduced and analyzed.
The joint analysis of this dataset will provide a very important
issue for the OSIRIS at the GTC scientific case.
OSIRIS AT THE GRANTECAN
Figure 3A: Ha velocity field of IIIZw102
obtained from Fabry Perot observations.
Figure 3B: Velocity field of the ionized gas of IIIZw102 derived for the labeled
emission lines from the Integral spectra.Contours correspond to the intensity maps
of the indicated emission lines.
FP Velocity fields -better velocity resolution-,allow the identification of low velocity structures, such us
expanding bubbles. Moreover, it is possible to study in detail the connection of kinematic perturbations
to morphological features.
Kinematics maps from Integral data allow to have a view of the global velocity field.
IIIZw102 presents an important rotating pattern -about 200km/sec-, larger than what expected in typical
BCDs. We propose that the galaxy is a dwarf spiral as for example NGC 4214 / see Maiz-Apellaniz
etal. 1999. The deviations from the rotation pattern are not detected at our spectral resolution.
will allow to produce maps similar to those obtained
with INTEGRAL (similar spectral resolution with the
Tunable Filters), in adittion recovering the lower
intensity features.
Fabry Perot studies of resolution about 15-30 km/sec
are crucial to understand typical internal motions of
bubbles and structures present in BCDs.
FP OSIRIS is of paramount importance to study the low
emissivity features and kinematics which are to
be related e.g. to the Super-Galactic Winds processes
in BCDs galaxies.