J/A+A/687/A16 New QSOs behind the Magellanic Clouds. II. (Ivanov+, 2024)
New quasars behind the Magellanic Clouds.
II. Spectroscopic confirmation of 136 near-infrared selected candidates.
Ivanov V.D., Cioni M.-R.L., Dennefeld M., de Grijs R., Craig J.E.M.,
van Loon J.T., Pennock C.M., Maitra C., Haberl F.
<Astron. Astrophys. 687, A16 (2024)>
=2024A&A...687A..16I 2024A&A...687A..16I (SIMBAD/NED BibCode)
ADC_Keywords: Surveys ; Active gal. nuclei ; Magellanic Clouds ; QSOs ;
Galaxies, photometry ; Photometry, infrared ; Redshifts
Spectra, ultraviolet ; Spectroscopy
Keywords: surveys - Magellanic Clouds - quasars: general
Abstract:
Quasi-stellar objects (QSOs) are a basis for an absolute reference
system for astrometric studies. There is a need for creating such
system behind nearby galaxies, to facilitate the measuring of the
proper motions of these galaxies. However, the foreground
contamination from the galaxies themselves is a problem for the QSO
identification.
We search for new QSOs behind both Magellanic Clouds, the Magellanic
Bridge, and the Magellanic Stream.
We identify QSO candidates with a combination of near-infrared colors
and variability criteria from the public ESO Visual and Infrared
Survey Telescope for Astronomy (VISTA) Magellanic Clouds (VMC) survey.
We confirm their nature from broad emission lines with low-resolution
optical spectroscopy.
We confirmed the QSO nature of 136 objects. They are distributed as
follows: 12 behind the LMC, 37 behind the SMC, 63 behind the Bridge,
and 24 behind the Stream. The QSOs span a redshift range from z∼0.1 to
z∼2.9. A comparison of our quasar selection with the Quaia quasar
catalog, based on Gaia low-resolution spectra, yields a selection and
confirmation success rate of 6-19%, depending on whether the quality
of the photometry, the magnitude ranges and the colors are considered.
Our candidate list is rather incomplete, but the objects in it are
likely to be confirmed as quasars with ∼90% probability. Finally, we
report a list of 3609 objects across the entire VMC survey that match
our color and variability selection criteria; only 1249 of them have
Gaia counterparts.
Our combined infrared color and variability criteria for QSO selection
prove to be efficient - ∼90% of the observed candidates are bona fide
QSOs and allow to generate a list of new high-probability quasar
candidates.
Description:
VMC coordinates and photometry of QSO candidates, log of the VLT
spectroscopic observations, derived parameters for the objects in this
paper and a complete list of quasar candidates in the VMC survey.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 152 151 VMC coordinates and photometry of QSO candidates
table2.dat 70 670 log of the VLT spectroscopic observations
table4.dat 146 443 Derived parameters for the objects
tableb1.dat 145 3609 Complete list of quasar candidates
in the VMC survey
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 23 A23 --- VMC VMC identifier (VMC HH:MM:SS.ss-DD:MM:SS.s)
28- 29 I2 h RAh Right ascension (J2000)
31- 32 I2 min RAm Right ascension (J2000)
34- 38 F5.2 s RAs Right ascension (J2000)
43 A1 --- DE- Declination sign (J2000)
44- 45 I2 deg DEd Declination (J2000)
47- 48 I2 arcmin DEm Declination (J2000)
50- 53 F4.1 arcsec DEs Declination (J2000)
58- 63 F6.3 mag Ymag VMC Y band magnitude
68- 72 F5.3 mag e_Ymag VMC Y band magnitude error
77- 82 F6.3 mag Jmag VMC J band magnitude
87- 91 F5.3 mag e_Jmag VMC J band magnitude error
96-101 F6.3 mag Ksmag VMC Ks band magnitude
106-110 F5.3 mag e_Ksmag VMC Ks band magnitude error
115-116 I2 --- Class [-1/1] Morphology (1)
121-133 A13 --- Object Object name
135-152 A18 --- OName Other name
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Note (1): Morphology code as follows:
-1 = point-like
1 = extended
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 12 A12 --- Object Object name
16- 39 A24 "datime" ObsTime UT data and time at start
42- 46 F5.1 s ExpTime Exposure time
50- 54 F5.3 --- AirmassS Airmass at start of observing
56- 60 F5.3 --- AirmassE Airmass at end of observing
64- 70 F7.3 deg PA [] Position angle of the slit
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 13 A13 --- Object Object name
20- 43 A24 --- Line ?=-9 Quasar line or comment
56- 62 F7.2 0.1nm lambda ?=-9 Observed wavelength (1)
69- 73 F5.2 0.1nm e_lambda ?=-9 Observed wavelength error (1)
81- 83 I3 --- S/N SNR at ±20 Ang around the line
89- 95 F7.4 --- zQSO ?=-9 Quasar redshift, averaged (1)
99-105 F7.4 --- e_zQSO ?=-9 Quasar redshift, error (1)
110 I1 --- f_zQSO Redshift quality flag (2)
115-119 F5.2 --- zQuaia ?=-9 Quaia (Gaia-unWISE Quasar Catalog)
redshift, averaged (1)
124-128 F5.2 --- e_zQuaia ?=-9 Quaia redshift, error (1)
138-146 A9 --- Class Object classification
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Note (1): -9 marks lack of data
Note (2): Redshift quality flag as follows:
0 = reliable redshift
1 = redshift based on a single line or low S/N
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Byte-by-byte Description of file: tableb1.dat
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Bytes Format Units Label Explanations
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1- 26 A26 --- VMC VMC identifier (VMC HH:MM:SS.ss-DD:MM:SS.s)
30- 31 I2 h RAh Right ascension (J2000)
33- 34 I2 min RAm Right ascension (J2000)
36- 40 F5.2 s RAs Right ascension (J2000)
42 A1 --- DE- Declination sign (J2000)
43- 44 I2 deg DEd Declination (J2000)
46- 47 I2 arcmin DEm Declination (J2000)
49- 52 F4.1 arcsec DEs Declination (J2000)
56- 62 F7.4 mag Gmag ?=-9 Gaia G band magnitude (1)
64- 70 F7.4 mag e_Gmag ?=-9 Gaia G band magnitude error (1)
74- 79 F6.3 mag Ymag VMC Y band magnitude
81- 85 F5.3 mag e_Ymag VMC Y band magnitude error
88- 93 F6.3 mag Jmag VMC J band magnitude
95- 99 F5.3 mag e_Jmag VMC J band magnitude error
102-107 F6.3 mag Ksmag VMC Ks band magnitude
109-113 F5.3 mag e_Ksmag VMC Ks band magnitude error
117-124 F8.5 --- Slope Fitted slope to the VMC Ks light curve
126-132 F7.5 --- e_Slope Error of the slope
136-138 I3 --- Npts Number of VMC Ks epochs
142-145 F4.2 yr DeltaT Time span covered by the VMC Ks light curve
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Note (1): -9 marks lack of data
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Acknowledgements:
Valentin D. Ivanov, vivanov(at)eso.org
(End) Valentin D. Ivanov [ESO, Germany], Patricia Vannier [CDS] 29-Apr-2024