J/A+A/631/A78 QSOs at z∼6 spectral cubes (Stanley+, 2019)
A spectral stacking analysis to search for faint outflow signatures in
z ∼ 6 quasars.
Stanley F., Jolly J.B., Koenig S., Knudsen K.K.
<Astron. Astrophys. 631, A78 (2019)>
=2019A&A...631A..78S 2019A&A...631A..78S (SIMBAD/NED BibCode)
ADC_Keywords: QSOs ; Spectroscopy
Keywords: galaxies: high-redshift - quasars: general - galaxy evolution -
submillimeter: galaxies
Abstract:
Outflows in quasars during the early epochs of galaxy evolution are an
important part of the feedback mechanisms potentially affecting the
evolution of the host galaxy. However, systematic observations of
outflows are only now becoming possible with the advent of sensitive
mm telescopes. In this study we use spectral stacking methods to
search for faint high velocity outflow signal in a sample of [CII]
detected, z∼6 quasars. We search for broad emission line signatures
from high-velocity outflows for a sample of 26 z∼6 quasars observed
with ALMA, with a detection of the [CII] line. The observed emission
lines of the sources are dominated by the host galaxy, and outflow
emission is not detected for the individual sources. We use a spectral
line stacking analysis developed for interferometric data to search
for outflow emission. We stack both extracted spectra and the full
spectral cubes. We also investigate the possibility that only a
sub-set of our sample contributes to the stacked outflow emission. We
find only a tentative detection of a broad emission line component in
the stacked spectra. When taking a region of about 2 arcsec around the
source central position of the stacked cubes, the stacked line shows
an excess emission due to a broad component of 1.1-1.5 sigma, but the
significance drops to 0.4-0.7 sigma when stacking the extracted
spectra from a smaller region. The broad component can be
characterised by a line width of full width half max FWHM > 700 km/s.
Furthermore, we find a sub-sample of 12 sources the stack of which
maximises the broad component emission. The stack of this sub-sample
shows an excess emission due to a broad component of 1.2-2.5 sigma.
The stacked line of these sources has a broad component of
FWHM>775km/s. Deeper ALMA observations are necessary to confirm the
presence of a broad component in the individual spectra.
Description:
We provide the reduced and continuum subtracted image cubes for the
sources included in our stacking, with channel width of 30km/s, beam
size of 0.8arcsec and pixel size of 0.2 arcsec. For each cube the
central velocity is chosen according the best-fit redshift of the
bright emission line.
We also provide the stacked cubes for the 3 different weights used in
our analysis (the cubes have been calculated after rebinning along the
velocity axis of the cubes according to the methodology described in
the paper).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
sources.dat 119 26 List of studied sources
list.dat 210 35 List of fits datcubes
fits/* . 35 Individual fits datacubes
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Byte-by-byte Description of file: sources.dat
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Bytes Format Units Label Explanations
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1- 27 A27 --- Name Source name
29- 30 I2 h RAh Right ascension (J2000)
32- 33 I2 min RAm Right ascension (J2000)
35- 39 F5.2 s RAs Right ascension (J2000)
41 A1 --- DE- Declination sign (J2000)
42- 43 I2 deg DEd Declination (J2000)
45- 46 I2 arcmin DEm Declination (J2000)
48- 52 F5.2 arcsec DEs Declination (J2000)
54- 83 A30 --- FileName Name of the fits datacube in subdirectory fits
85-119 A35 --- SName Simbad name
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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 I3 --- Nx Number of pixels along X-axis
24- 26 I3 --- Ny Number of pixels along Y-axis
28- 30 I3 --- Nz Number of slices
32- 57 A26 "datime" Obs.date Observation date
59- 70 E12.6 m/s bVRAD Lower value of VRAD interval
72- 82 E11.6 m/s BVRAD Upper value of VRAD interval
84- 94 E11.6 m/s dVRAD VRAD resolution
96-100 I5 Kibyte size Size of FITS file
102-143 A42 --- FileName Name of FITS file, in subdirectory fits
145-210 A66 --- Title Title of the FITS file
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Acknowledgements:
Flora Stanley, flora.stanley(at)chalmers.se
(End) Patricia Vannier [CDS] 05-Sep-2019