J/A+A/631/A91 2 strongly lensed galaxies MUSE & ALMA datacubes (Girard+, 2019)
Towards sub-kpc scale kinematics of molecular and ionized gas of star-forming
galaxies at z∼1.
Girard M., Dessauges-Zavadsky M., Combes F., Chisholm J., Patricio V.,
Richard J., Schaerer D.
<Astron. Astrophys. 631, A91 (2019)>
=2019A&A...631A..91G 2019A&A...631A..91G (SIMBAD/NED BibCode)
ADC_Keywords: Galaxies, spectra ; Gravitational lensing; Galaxies, optical;
Galaxies, radio
Keywords: galaxies : high-redshift - galaxies : kinematics and dynamics -
gravitational lensing: strong
Abstract:
We compare the molecular and ionized gas kinematics of two strongly
lensed galaxies at z∼1 that lie on the main sequence at this redshift,
based on observations from ALMA and MUSE, respectively. We derive the
CO and [OII] rotation curves and dispersion profiles of these two
galaxies. We find a difference between the observed molecular and
ionized gas rotation curves for one of the two galaxies, the Cosmic
Snake, for which we obtain a spatial resolution of few hundred parsecs
along the major axis. The rotation curve of the molecular gas is
steeper than the rotation curve of the ionized gas. In the second
galaxy, A521, the molecular and ionized gas rotation curves are
consistent, but the spatial resolution is only of few kpc on the major
axis. Using simulations, we investigate the effect of the thickness of
the gas disk and effective radius on the observed rotation curves and
find that a more extended and thicker disk smooths the curve. We also
find that the presence of a strongly inclined (>70°) thick disk
(>1kpc) can smooth the rotation curve because it degrades the spatial
resolution along the line of sight. By building a model using a
stellar disk and two gas disks, we reproduce the rotation curves of
the Cosmic Snake with a molecular gas disk that is more massive and
more radially and vertically concentrated than the ionized gas disk.
Finally, we also obtain an intrinsic velocity dispersion in the Cosmic
Snake of 18.5±7km/s and 19.5±6km/s for the molecular and ionized
gas, respectively, which is consistent with a molecular disk with a
smaller and thinner disk. For A521, the intrinsic velocity dispersion
values are 11±8km/s and 54±11km/s, with a higher value for the
ionized gas. This could indicate that the ionized gas disk is thicker
and more turbulent in this galaxy. These results highlight the
diversity of the kinematics of galaxies at z∼1 and the different
spatial distribution of the molecular and ionized gas disks. It
suggests the presence of thick ionized gas disks at this epoch and
that the formation of the molecular gas is limited to the midplane and
center of the galaxy in some objects.
Description:
MUSE data cubes : The observations, data reduction and emission line
measurements are described in Patricio et al. (2018MNRAS.477...18P 2018MNRAS.477...18P).
The observations were seeing-limited for the Cosmic Snake while A521
was observed with adaptive optics. The PSF obtained during the
observations were 0.51" and 0.57", respectively.
ALMA data cubes : Observations of the Cosmic Snake were carried out in
Cycle 3 (project 2013.1.01330.S) and were performed in the extended
C38-5 configuration with the maximum baseline of 1.6km and 38 of the
12 meters antennae. The total on-source integration time was of 52.3
minutes in band 6. We observed the CO(4-3) emission line at the
observed frequency of 226.44GHz which corresponds to a redshift of
z=1.036. A521 was observed in Cycle 4 (project 2016.1.00643.S) using
the C40-6 configuration with the maximum baseline of 3.1km and 41 12
meters antennae. Similarly, the observations were carried out in band
6 to detect the CO(4-3) emission line at an observed frequency of
225.66GHz, corresponding to a redshift of z=1.043, with an on-source
time of 89.0 minutes. The spectral resolution was tuned to 7.8125MHz
(∼10.3km/s) for both galaxies
The data reduction was performed with the standard automated
reduction procedure from the pipeline of the Common Astronomy Software
Application (CASA) package (McMullin et al., 2007, ASP Conf. Ser.,
376, 127). To image the CO(4-3) line, we used the Briggs weighting and
the robust factor of 0.5, which gives a good compromise between the
resolution and sensitivity. We cleaned all channels interactively,
with the clean routine in CASA, until convergence. To perform the
cleaning, we used a custom mask for which we made sure to include the
CO emission of all the channels. We then applied the primary beam
correction. The final synthesized beam size is 0.22"x0.18" with a
position angle of +85°for the Cosmic Snake and 0.20"x0.17" at
-71° A521. We reach an rms of 0.29mJy/beam and 0.34mJy/beam per
7.8125MHz channel for the Cosmic Snake and A521, respectively.
Objects:
-----------------------------------------
RA (2000) DE Designation(s)
-----------------------------------------
12 06 11 -08 48 05 Cosmic Snake
04 54 06 -10 13 23 A521
-----------------------------------------
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 203 4 List of fits datacubes
fits/* . 4 Individual fits datacubes
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Byte-by-byte Description of file: list.dat
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Bytes Format Units Label Explanations
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1- 9 F9.5 deg RAdeg Right Ascension of center (J2000)
10- 18 F9.5 deg DEdeg Declination of center (J2000)
20- 22 F3.1 arcsec/pix scale ? Scale of the image
24- 27 I4 --- Nx Number of pixels along X-axis
29- 32 I4 --- Ny Number of pixels along Y-axis
34- 36 I3 --- Nz Number of slices
38- 60 A23 "datime" Obs.date Observation date
62- 72 E11.6 Hz bFREQ ? Lower value of frequency interval
74- 84 E11.6 Hz BFREQ ? Upper value of frequency interval
86- 96 E11.6 Hz dFREQ ? Frequency resolution
98-108 E11.6 0.1nm bAWAV ? Lower value of wavelength interval
110-120 E11.6 0.1nm BAWAV ? Upper value of wavelength interval
122-132 E11.6 0.1nm dAWAV ? Wavelength resolution
134-139 I6 Kibyte size Size of FITS file
141-160 A20 --- FileName Name of FITS file, in subdirectory fits
162-203 A42 --- Title Title of the FITS file
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Acknowledgements:
Marianne Girard, Marianne.Girard(at)unige.ch
(End) M. Girard [Geneva Obs., Switzerland], P. Vannier [CDS] 26-Sep-2019