J/MNRAS/517/484 JWST NIRCam photometry of M 92 stars (Nardiello+, 2022)
Photometry and astrometry with JWST - I. NIRCam point spread functions and
the first JWST colour-magnitude diagrams of a globular cluster.
Nardiello D., Bedin L.R., Burgasser A., Salaris M., Cassisi S., Griggio M.,
Scalco M.
<Mon. Not. R. Astron. Soc. 517, 484-497 (2022)>
=2022MNRAS.517..484N 2022MNRAS.517..484N (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Photometry ; Optical ; Infrared
Keywords: techniques: image processing - techniques: photometric -
stars: Population II - white dwarfs -
globular clusters: individual: NGC 6341 (M 92)
Abstract:
As the James Webb Space Telescope (JWST) has become fully operational,
early release data are now available to begin building the tools and
calibrations for precision point-source photometry and astrometry in
crowded cluster environments. Here, we present our independent
reduction of NIRCam imaging of the metal-poor globular cluster M 92,
which were collected under Director's Discretionary Early Release
Science programme ERS-1334. We derived empirical models of the point
spread function (PSF) for filters F090W, F150W, F277W, and F444W, and
find that these PSFs: (i) are generally undersampled (FWHM ∼ 2 pixel)
in F150W and F444W and severely undersampled (FWHM ∼ 1 pixel) in F090W
and F277W; (ii) have significant variation across the field of view,
up to ∼15-20 per cent; and (iii) have temporal variations of ∼ 3-4 per
cent across multi-epoch exposures. We deployed our PSFs to determine
the photometric precision of NIRCam for stars in the crowded, central
regions of M 92, measured to be at the ∼0.01 mag level. We use these
data to construct the first JWST colour-magnitude diagrams of a
globular cluster. Employing existing stellar models, we find that the
data reach almost the bottom of the M 92 main sequence (∼0.1 M☉),
and reveal 24 white dwarf candidate members of M 92 in the brightest
portion of the white dwarf cooling sequence. The latter are confirmed
through a cross-match with archival HST UV and optical data. We also
detect the presence of multiple stellar populations along the low-mass
main sequence of M 92.
Description:
This paper shows globular cluster M 92 observations with NIRCam
imaging camera covering the red optical and near-IR wavelength range
0.6-5 µm. PSF modelling is done to extract positions and fluxes of
stars in each individual images in F090W, F150W, F277W, and F444W
filters (i.e see section 2 & 3). For the 4 filters, the A and B
modules, the 4 detectors, we present image pixel positions, vega
magnitudes and fit quality indicators in tables f090wa1-4.dat,
f090wb1-4.dat, f150wa1-4.dat, f150wb1-4.dat, f277wa-b.dat and
f444wa-b.dat.
Objects:
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RA (2000) DE Designation(s)
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17 17 07.38 +43 08 09.3 M 92 = NGC 6341 = BD+43 2711
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
f090wa1.dat 38 6417 Star sources NIRCam PSF photometry in F090W,
SW module A and channel 1 of the detector
f090wa2.dat 38 6831 Star sources NIRCam PSF photometry in F090W,
SW module A and channel 2 of the detector
f090wa3.dat 38 13955 Star sources NIRCam PSF photometry in F090W,
SW module A and channel 3 of the detector
f090wa4.dat 38 14785 Star sources NIRCam PSF photometry in F090W,
SW module A and channel 4 of the detector
f090wb1.dat 38 6898 Star sources NIRCam PSF photometry in F090W,
SW module B and channel 1 of the detector
f090wb2.dat 38 7476 Star sources NIRCam PSF photometry in F090W,
SW module B and channel 2 of the detector
f090wb3.dat 38 16229 Star sources NIRCam PSF photometry in F090W,
SW module B and channel 3 of the detector
f090wb4.dat 38 16321 Star sources NIRCam PSF photometry in F090W,
SW module B and channel 4 of the detector
f150wa1.dat 38 8322 Star sources NIRCam PSF photometry in F150W,
SW module A and channel 1 of the detector
f150wa2.dat 38 8743 Star sources NIRCam PSF photometry in F150W,
SW module A and channel 2 of the detector
f150wa3.dat 38 17210 Star sources NIRCam PSF photometry in F150W,
SW module A and channel 3 of the detector
f150wa4.dat 38 18325 Star sources NIRCam PSF photometry in F150W,
SW module A and channel 4 of the detector
f150wb1.dat 38 9463 Star sources NIRCam PSF photometry in F150W,
SW module B and channel 1 of the detector
f150wb2.dat 38 10052 Star sources NIRCam PSF photometry in F150W,
SW module B and channel 2 of the detector
f150wb3.dat 38 17822 Star sources NIRCam PSF photometry in F150W,
SW module B and channel 3 of the detector
f150wb4.dat 38 19753 Star sources NIRCam PSF photometry in F150W,
SW module B and channel 4 of the detector
f277wa.dat 38 19177 Star sources NIRCam PSF photometry in F277W,
LW module A
f277wb.dat 38 19277 Star sources NIRCam PSF photometry in F277W,
LW module B
f444wa.dat 38 21347 Star sources NIRCam PSF photometry in F444W,
LW module A
f444wb.dat 38 22333 Star sources NIRCam PSF photometry in F444W,
LW module B
list.dat 75 4 List of fits images
fits/* . 4 Individual fits images
img/* . 6 Individual images in .png and .jpeg
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See also:
J/AJ/149/153 : Abundances of red giants in 10 globular clusters
(Meszaros+, 2015)
J/ApJ/797/15 : HST/WFC3 observations in 4 metal-poor GCs of Fornax
(Larsen+, 2014)
VII/195 : Globular Clusters in the Milky Way (Harris, 1996)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
J/AJ/133/1658 : ACS survey of galactic globular clusters (Sarajedini+, 2007)
J/MNRAS/463/1780 : Exoplanet candidates in Praesepe (M 44) (Libralato+, 2016)
J/MNRAS/463/1831 : M67 Kepler/K2 variable stars (Nardiello+, 2016)
Byte-by-byte Description of file: f090???.dat f150???.dat f277w?.dat f444w?.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 pix X X stellar position in the reference system of the
detector
9- 15 F7.2 pix Y Y stellar position in the reference system of the
detector
17- 23 F7.4 mag Xmag Calibrated Vega magnitude of NIRCam JWST in filter
as the file's names indicate F090W, F150W, F277W
and F444W (MAG)
25- 30 F6.4 mag e_Xmag Photometric error of Xmag (SIGMA_MAG)
32- 38 F7.4 --- Qfit The quality of a PSF model fit to an individual
star where the smaller is the qfit the better the
PSF fit is (QFIT)
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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- 5 I5 --- Nx Number of pixels along X-axis
7- 11 I5 --- Ny Number of pixels along Y-axis
13- 18 I6 Kibyte size Size of FITS file
20- 42 A23 --- FileName Name of FITS file, in subdirectory fits
44- 75 A32 --- Title Title of the FITS file
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History:
From electronic version of the journal
(End) Luc Trabelsi [CDS] 09-Sep-2025