J/A+A/437/1135 Near-IR astrometry of Southern ICRF quasars (Camargo+, 2005)
Near-infrared astrometry and photometry of Southern ICRF quasars.
Camargo I.B., Daigne G., Ducourant C., Charlot P.
<Astron. Astrophys. 437, 1135 (2005)>
=2005A&A...437.1135C 2005A&A...437.1135C
ADC_Keywords: QSOs ; Infrared sources ; Positional data
Keywords: astrometry - infrared: general - methods: numerical -
reference systems
Abstract:
We present high quality astrometry, along with J, H, and Ks
photometry, for 30 southern International Celestial Reference Frame
(ICRF) quasars observed with the ESO NTT/SOFI at La Silla. Our main
purpose is to document the optical counterpart of ICRF quasars, by
reporting their position in a stellar reference frame and their
near-infrared photometry. Our investigation lies within the scope of
extending the (radio) extragalactic reference frame into the optical
range. An internal precision generally better than 10mas was obtained
in positioning the near-infrared counterpart of these quasars within
their stellar surroundings. The actual astrometric accuracy is
estimated from the departure between the observed and the radio (VLBI)
positions of quasars, and is about 35mas, mainly due to the
statistical uncertainties of the stellar reference catalogue (UCAC2,
Cat. I/289). The positional accuracy was improved to 25mas for a
subset of 14 quasars observed with extended fields of view, as
obtained from mosaics of overlapping images. The 3-band photometry was
achieved with a precision most often better than 0.04mag, based on
calibration with the 2MASS magnitudes.
Description:
Our near-IR observations were carried out with the 3.5m ESO NTT SOFI
located at La Silla, 70°43'54.272"W 29°15'18.440"S, during a
3-night run from 8 to 11 January 2003.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
position.dat 65 30 Positions, from Ma et al., Cat. I/251
table2.dat 115 32 Photometric data
table3.dat 53 32 *Astrometric data
table4.dat 76 16 *Astrometric data, Results in the F filter
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Note on table3.dat and table4.dat: All ICRF positions are taken from Ma et al.
(1998, Cat. I/251). Near-IR positions are taken as the mean of those
obtained from the J, H, and Ks bands.
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See also:
I/251 : VLBI International Celestial Reference Frame (ICRF) (Ma+, 1997)
J/A+A/375/308 : Extension of ICRF for SA down to V=15 (Camargo+ 2001)
J/A+A/409/361 : Extension of ICRF for SA down to V=16 (Camargo+, 2003)
J/AJ/127/3587 : VLBI ICRF. II (Fey+, 2004)
J/AJ/125/2728 : Optical positions of ICRF sources (Assafin+, 2003)
I/289 : UCAC2 Catalogue (Zacharias+ 2004)
VII/235 : Quasars and Active Galactic Nuclei (11th Ed.) (Veron+, 2003)
I/284 : The USNO-B1.0 Catalog (Monet+ 2003)
Byte-by-byte Description of file: position.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- IERS IERS designation
10- 13 A4 --- --- [ICRF]
15- 30 A16 --- ICRF ICRF designation
34- 35 I2 h RAh Right ascension (J2000.0)
37- 38 I2 min RAm Right ascension (J2000.0)
40- 48 F9.6 s RAs Right ascension (J2000.0)
51 A1 --- DE- Declination sign (J2000.0)
52- 53 I2 deg DEd Declination (J2000.0)
55- 56 I2 arcmin DEm Declination (J2000.0)
58- 65 F8.5 arcsec DEs Declination (J2000.0)
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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- 8 A8 --- IERS IERS designation
10 A1 --- c [CDO] Defining/Candidate/Other category
of source
12 A1 --- l_z Limit flag on z
13- 17 F5.3 --- z ? Redshift (1)
18 A1 --- n_z [*] *: Redshift from Cat. VII/235
19- 22 F4.2 Jy S6cm ? Flux density at 6cm, from literature
23 A1 --- n_S6cm [*] *: 6cm flux density from Cat. VII/235
24- 27 F4.1 --- alphaR ? Radio spectral index (1)
29- 34 A6 --- Type Object type (1)
36- 40 F5.1 mag BMAG ? Absolute B magnitude, from Cat. VII/235
42- 46 F5.2 mag Bmag ? B magnitude, from USNO-B1, Cat. I/284
48- 51 F4.1 mag Vmag ? V magnitude, from literature (1)
52 A1 --- n_Vmag [*] *: Vmag from Cat. VII/235
53- 56 F4.1 mag Rmag ? R magnitude, from USNO-B1, Cat. I/284
58- 60 A3 --- IntId Internal identification
(p: photometry mode, a: astrometry mode)
62- 69 F8.2 d MJD Modified Julian date of the observation
71- 75 F5.2 mag Jmag Observed J magnitude
77- 81 F5.2 mag Hmag Observed H magnitude
83- 87 F5.2 mag Ksmag Observed Ks magnitude
89- 92 F4.2 mJy JFlux Observed J-band flux
94- 98 F5.2 mJy HFlux Observed H-band flux
100-104 F5.2 mJy KsFlux Observed Ks-band flux
106-110 F5.2 --- Sp+Index Near-IR spectral index
112-115 F4.2 --- e_Sp+Index rms uncertainty on Sp+Index
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Note (1): Data from Archinal et al. (1997, in Definition and Realization
of the International Celestial Reference System by VLBI Astrometry of
Extragalactic Objects, IERS Tech. Note 23, Paris: Obs. Paris, ed. C.
Ma, & M. Feissel, III 11), or from Veron-Cetty & Veron, 2003, Cat.
VII/235, if *
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 8 A8 --- IERS IERS quasar identification
10- 17 F8.2 d MJD Modified Julian Date of the observation
19- 22 I4 mas ORA* Offset in RAcosDE, in the sense
near-IR minus ICRF (1)
24- 26 I3 mas e_ORA* Precision of the observed near-IR position,
in RAcosDE (2)
28- 31 I4 mas ODE Offset in declination, in the sense
near-IR minus ICRF (1)
33- 35 I3 mas e_ODE Precision of the observed near-IR position,
in declination (2)
37- 38 I2 mas dRA* Standard deviations of the positional measurements
in the J, H, and Ks filters in RAcosDE
40- 41 I2 mas dDE Standard deviations of the positional measurements
in the J, H, and Ks filters in declination
43- 45 I3 mas eRA* Mean of the standard deviation, in RAcosDE (3)
47- 49 I3 mas eDE Mean of the standard deviation, in declination (3)
51- 52 I2 --- N Number of reference (UCAC2) stars used in the
astrometric analysis of the observations made
in the photometry mode
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Note (1): Positional differences from the astrometric analysis of the
observations made in the photometry mode, in the sense near-IR minus
ICRF, in right ascension and declination, respectively.
Note (2): Precisions of the observed near-IR positions of the ICRF quasars,
as derived from the astrometric analysis of the observations made in
the photometry mode. These precisions are the combined errors from
each of the photometric filters
Note (3): Mean of the standard deviation, as obtained from each of the
photometric filters, of the differences observed minus calculated to
the reference (UCAC2) stars in the photometry mode at the epoch of the
observations.
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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- 8 A8 --- IERS IERS quasar identification
10- 17 F8.2 d MJD Modified Julian Date of the observation
19- 22 I4 mas ORA*S Offset in RAcosDE, in the sense
near-IR minus ICRF (1)
24- 25 I2 mas e_ORA*S Precision of the observed near-IR position,
in RAcosDE (2)
27- 29 I3 mas ODES Offset in declination, in the sense
near-IR minus ICRF (1)
31- 32 I2 mas e_ODES Precision of the observed near-IR position,
in declination (2)
34- 35 I2 --- NS Number of reference (UCAC2) stars used in the
astrometric analysis of the single central image
38- 40 I3 mas ORA*M Offset in RAcosDE, in the sense
near-IR minus ICRF (3)
42- 43 I2 mas e_ORA*M Precision of the observed near-IR position,
in RAcosDE (4)
45- 47 I3 mas ODEM Offset in declination, in the sense
near-IR minus ICRF (3)
49- 50 I2 mas e_ODEM Precision of the observed near-IR position,
in declination (4)
52- 54 I3 --- NM Number of reference (UCAC2) stars used in
the astrometry mode
56- 57 I2 mas cRA* Internal precision as obtained from the positions
of stars in overlapping regions, in RAcosDE
59- 60 I2 mas cDE* Internal precision as obtained from the positions
of stars in overlapping regions, in declination
62- 63 I2 mas RA* rms of the differences observed minus calculated,
in RAcosDE (5)
65- 66 I2 mas DE rms of the differences observed minus calculated,
in declination (5)
68- 71 F4.2 --- rRA Ratio between the values and the respective
nominal for right ascension
73- 76 F4.2 --- rDE Ratio between the values and the respective
nominal for declination
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Note (1): Positional differences from the astrometric analysis of the
single central image, in the sense near- IR minus ICRF.
Note (2): Precisions from the astrometric analysis of the single central
image, of the observed near-IR positions of the ICRF quasars.
Note (3): Positional differences from the reduction in astrometry mode,
in the sense near-IR minus ICRF.
Note (4): Precisions of the observed near-IR positions in the astrometry
mode of the ICRF quasars.
Note (5): rms of the differences observed minus calculated to the reference
(UCAC2) stars in the astrometry mode at the epoch of the observations
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History:
From electronic version of the journal
(End) Patricia Vannier [CDS] 02-Jul-2005