J/PASP/120/1128 Calibrated griz magnitudes of Tycho stars (Ofek, 2008)
Calibrated griz magnitudes of Tycho stars: All-sky photometric calibration
using bright stars
Ofek E.O.
<Publ. Astron. Soc. Pac. 120, 1128 (2008)>
=2008PASP..120.1128O 2008PASP..120.1128O
ADC_Keywords: Infrared sources; Photometry, infrared ; Photometry, SDSS
Abstract:
Photometric calibration at an accuracy of ∼5% in an arbitrary
celestial location is frequently needed. However, existing all-sky
astronomical catalogue do not reach this accuracy, and time consuming
photometric calibration procedures are required. I fitted the
Hipparcos BT, and VT magnitudes, along with the 2MASS J, H, and K
magnitudes of Tycho-2 catalog-stars with stellar spectral templates.
From the best fit spectral template derived for each star, I
calculated its synthetic SDSS griz magnitudes, and constructed an
all-sky catalog of griz magnitudes of bright stars (V<12). Testing
this method on SDSS photometric telescope observations, I find that
the photometric accuracy, for a single star, is usually about 0.12,
0.12, 0.10 and 0.08 mag (1sigma), for the g, r, i, and z-bands,
respectively. However, by using ∼10 such stars, the typical errors per
calibrated field (systematic + statistical) can be reduced to about
0.04, 0.03, 0.02, and 0.02 mag, in the g, r, i, and z-bands,
respectively. Therefore, in cases for which several calibration stars
can be observed in the field of view of an instrument, it is possible
to photometrically calibrate the image.
Description:
The catalog was constructed from the stars with BT<13mag and
VT<12mag in the Tycho-2 catalog (Hog et al. 2000, Cat. I/259),
cross-correlated with the 2MASS catalog (Cutri et al. 2003,
Cat. II/246). The BTVTJHK magnitudes were fitted with the
131 spectral templates of Pickles 1998 (Cat. J/PASP/110/863).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
catalog.dat 175 1560980 Catalog of griz magnitudes for Tycho-2 stars with
BT<13mag and VT<12mag
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See also:
I/259 : The Tycho-2 Catalogue (Hog+ 2000)
II/246 : 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)
J/PASP/110/863 : A Stellar Spectral Flux Library: 1150 - 25000 A (Pickles 1998)
Byte-by-byte Description of file: catalog.dat
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Bytes Format Units Label Explanations
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2- 12 F11.7 deg RAdeg Right Ascension J2000.0
15- 25 F11.7 deg DEdeg Declination J2000.0
29 I1 --- ok [0,1] Flag indicating a good standard (1)
33- 37 F5.2 mag BTmag BT magnitude
39- 42 F4.2 mag e_BTmag BT magnitude error
44- 48 F5.2 mag VTmag VT magnitude
50- 53 F4.2 mag e_VTmag VT magnitude error
56- 60 F5.2 mag Jmag ?=- J magnitude
61- 65 F5.2 mag e_Jmag ?=- J magnitude error (2)
67- 71 F5.2 mag Hmag ?=- H magnitude
72- 76 F5.2 mag e_Hmag ?=- H magnitude error (2)
78- 82 F5.2 mag Kmag ?=- K magnitude
83- 87 F5.2 mag e_Kmag ?=- K magnitude error (2)
93-100 A8 --- rmsTem Best rms-fit spectral template (3)
102-106 F5.2 mag minRMS [0/11]?=- the rms for the best rms-fit template
108-112 F5.2 mag gmag ?=- rms-fit g-band magnitude
(0.06 magnitude already added)
114-118 F5.2 mag rmag ?=- rms-fit r-band magnitude
(0.04 magnitude already added)
120-124 F5.2 mag imag ?=- rms-fit i-band magnitude
(0.03 magnitude already added)
126-130 F5.2 mag zmag ?=- rms-fit z-band magnitude
(0.03 magnitude already added)
136-143 A8 --- chiTem Best χ2-fit spectral template (3)
144-151 F8.2 --- minChi ?=- the χ2 for the best
χ2-fit template (dof=4)
153-157 F5.2 mag 2gmag ?=- χ2-fit g-band magnitude
(0.07 magnitude already added)
159-163 F5.2 mag 2rmag ?=- χ2-fit r-band magnitude
(0.04 magnitude already added)
165-169 F5.2 mag 2imag ?=- χ2-fit i-band magnitude
(0.04 magnitude already added)
171-175 F5.2 mag 2zmag ?=- χ2-fit z-band magnitude
(0.03 magnitude already added)
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Note (1): Value 1 for a good standard, i.e.,
J>6 & H>6 & K>6 & err(BT)<0.15 & err(VT)<0.15 & minRMS<0.15.
Note (2): 10.00 indicates no error value.
Note (3): Template names adopted from the stellar spectra catalog of
Pickles (1998PASP..110..863P 1998PASP..110..863P, Cat. J/PASP/110/863)
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Acknowledgements:
Eran O. Ofek, eran(at)astro.caltech.edu
(End) Patricia Vannier [CDS] 19-Aug-2008