J/A+A/657/A113 QSO J1721+8842 spectra (Lemon+, 2022)
J1721+8842: a gravitationally lensed binary quasar with a proximate damped
Lyman-alpha absorber.
Lemon C., Millon M., Sluse D., Courbin F., Auger M., Chan J., Paic E.,
Agnello A.
<Astron. Astrophys. 657, A113 (2022)>
=2022A&A...657A.113L 2022A&A...657A.113L (SIMBAD/NED BibCode)
ADC_Keywords: Gravitational lensing ; QSOs ; Galaxies, spectra
Keywords: gravitational lensing: strong - galaxy: general -
quasars: individual: J1721+8842
Abstract:
High-redshift binary quasars provide key insights into mergers and
quasar activity, and are useful tools for probing the spatial
kinematics and chemistry of galaxies along the line-of-sight. However,
only three sub-10-kpc binaries have been confirmed above z=1.
Gravitational lensing would provide a way to easily resolve such
binaries, study them in higher resolution, and provide more
sightlines, though the required alignment with a massive foreground
galaxy is rare. Through image deconvolution of StanCam Nordic Optical
Telescope (NOT) monitoring data, we reveal two further point sources
in the known, z∼2.38, quadruply lensed quasar (quad), J1721+8842. An
ALFOSC/NOT long-slit spectrum shows that the brighter of these two
sources is a quasar with z=2.369±0.007 based on the CIII] line,
while the CIII] redshift of the quad is z=2.364±0.003. Lens
modelling using point source positions rules out a single source
model, favouring an isothermal lens mass profile with two quasar
sources separated by ∼6.0kpc (0.73") in projection. Given the
resolving ability from lensing and current lensed quasar statistics,
this discovery suggests a large population of undiscovered, unlensed
sub-10-kpc binaries. We also analyse spectra of two images of the
quad, showing narrow Lyα emission within the trough of a
proximate damped Lyman-α absorber (PDLA). An apparent mismatch
between the continuum and narrow line flux ratios provides a new
potential tool for simultaneously studying microlensing and the quasar
host galaxy. Signs of the PDLA are also seen in the second source,
however a deeper spectrum is still required to confirm this. Thanks to
the multiple lines-of-sight from lensing and two quasar sources, this
system offers simultaneous sub-parsec and kpc-scale probes of a PDLA.
Description:
Reduced two-dimensional spectra taken in long-slit spectroscopy mode
for J1721+8842, bias- and sky-subtracted, and masked of cosmic rays.
Two spectra are included taken at the same position angle as described
in the text of the paper.
Objects:
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RA (2000) DE Designation(s)
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17 21 49.01 +88 42 22.4 J1721+8842 = [LAM2018] J1721+8842
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
list.dat 115 2 List of fits spectra
fits/* . 2 Individual fits files
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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- 3 I3 --- Nx Number of pixels along X-axis
5- 8 I4 --- Ny Number of pixels along Y-axis
10- 32 A23 "datime" Obs.date Observation date
34- 37 I4 Kibyte size Size of FITS file
39- 53 A15 --- FileName Name of FITS file, in subdirectory fits
55-115 A61 --- Title Title of the FITS file
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Acknowledgements:
Cameron Lemon, cameron.lemon(at)epfl.ch
(End) Patricia Vannier [CDS] 02-Nov-2021