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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
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:
FileName Lrecl Records Explanations
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
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.
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
Bytes Format Units Label Explanations
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)
Byte-by-byte Description of file: table2.dat
Bytes Format Units Label Explanations
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
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 *
Byte-by-byte Description of file: table3.dat
Bytes Format Units Label Explanations
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
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.
Byte-by-byte Description of file: table4.dat
Bytes Format Units Label Explanations
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
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
History: From electronic version of the journal
(End) Patricia Vannier [CDS] 02-Jul-2005
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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