J/A+A/559/A29 BR 1202-0725 system in [CII] line (Carniani+, 2013)
Strongly star-forming rotating disks in a complex merging system at z=4.7
as revealed by ALMA.
Carniani S., Marconi A., Biggs A., Cresci G., Cupani G., D'Odorico V.,
Humphreys E., Maiolino R., Mannucci F., Molaro P., Nagao T., Testi L.,
Zwaan M.A.
<Astron. Astrophys. 559, A29 (2013)>
=2013A&A...559A..29C 2013A&A...559A..29C
ADC_Keywords: QSOs ; Spectra, infrared
Keywords: galaxies: kinematics and dynamics - galaxies: evolution -
galaxies: high-redshift - quasars: general - galaxies: starburst -
galaxies: star formation
Abstract:
We performed a kinematical analysis of the [CII] line emission of the
BR 1202-0725 system at z∼4.7 using ALMA science verification
observations. The most prominent sources of this system are a quasar
(QSO) and a submillimeter galaxy (SMG), separated by a projected
distance of about ∼24kpc and characterized by very high star formation
rates, higher than 1000M☉/yr. However, the ALMA observations
reveal that these galaxies apparently have undisturbed rotating disks,
which is at variance with the commonly accepted scenario in which
strong star formation activity is induced by a major merger.We also
detected faint components which, after spectral deblending, were
spatially resolved from the main QSO and SMG emissions. The relative
velocities and positions of these components are compatible with
orbital motions within the gravitational potentials generated by the
QSO host galaxy and the SMG, suggesting that they are smaller galaxies
in interaction or gas clouds in accretion flows of tidal streams.
Moreover, we did not find any clear spectral evidence for outflows
caused by active galactic nuclei or stellar feedback. This suggests
that the high star formation rates might be induced by interactions or
minor mergers with these companions, which do not affect the
large-scale kinematics of the disks, however. Alternatively, the
strong star formation may be fueled by the accretion of pristine gas
from the host halo. Our kinematical analysis also indicates that the
QSO and the SMG have similar dynamical masses, mostly in the form of
molecular gas, and that the QSO host galaxy and the SMG are seen close
to face-on with slightly different disk inclinations: the QSO host
galaxy is seen almost face-on (i∼15°), while the SMG is seen at
higher inclinations (i∼25°). Finally, the ratio between the black
hole mass of the QSO, obtained from new X-shooter spectroscopy, and
the dynamical mass of the host galaxy is similar to value found in
very massive local galaxies, suggesting that the evolution of black
hole galaxy relations is probably better studied with dynamical than
with stellar host galaxy masses.
Description:
Data cubes in FITS format of the [CII] lines for the 2 galaxies of
BR1202-0725 system.
The receivers were tuned to a [CII] redshifted frequency of about
333GHz (the rest frequency of [CII] is 1900.539GHz). The ALMA
correlator has a total bandwidth of 7.5GHz and was divided in to four
spectral windows of ∼1.8GHz with a channel width of 15.6MHz (∼14km/s).
In the datacube we can observe only the first and second spectral
window. The data were calibrated by using the CASA software. The units
of the data are Jy/beam.
Objects:
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RA (2000) DE Designation(s)
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12 05 23.12 -07 42 32.4 BR 1202-0725 = QSO B1202-074
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
br1202.fits 2880 774 *Data cube in FITS format
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Note on br1202.fits: Scale is 0.15arcsec/pix, the interval of frequency is
332.984/336.859GHz, with a step of 31.25eMHz corresponding to the
redshifted CII line.
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Acknowledgements:
Stefano Carniani, carniani(at)arcetri.astro.it
(End) Stefano Carniani [Univ. Florence], Patricia Vannier [CDS] 02-Oct-2013