J/ApJ/986/80 NGC 2808 astro-photometric catalog (Griggio+, 2025)
The internal kinematics of NGC 2808 and its multiple populations.
Griggio M., Bellini A., Aros F.I., Vesperini E., Libralato M., Anderson J.,
Baumgardt H., Ferraro F.R., van der Marel R.P., Raso S., Renzini A.,
Rest A., Ryan R.E.Jr
<Astrophys. J. 986, 80 (2025)>
=2025ApJ...986...80G 2025ApJ...986...80G (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Photometry ; Proper motions
Keywords: globular clusters: individual (NGC 2808) -
stars: kinematics and dynamics -
Hertzsprung-Russell and C-M diagrams - proper motions
Abstract:
We use new HST observations coupled with archival data spanning a
total temporal baseline of 17 years to study the internal kinematics
of the multiple populations in the globular cluster NGC 2808 from its
center out to ∼8 half-light radii (rh). We detect different
kinematical behaviors between the first- and second-generation
populations. This is especially evident towards the external regions
of the cluster, where second-generation stars are increasingly more
radially anisotropic. Our results are in agreement with theoretical
simulations that predict that second-generation stars, initially more
concentrated in the inner regions, gradually diffuse outward and
develop a stronger radially anisotropic velocity distribution with
respect to the first-generation stars. We find the central regions of
the cluster to exhibit a higher degree of energy equipartition than
the outskirts; our analysis reveals similar levels of energy
equipartition in the radial and tangential components of the motion
within about 4rh , while outside 4rh the data suggest that the
equipartition level of the radial component of the velocity dispersion
is slightly higher than that of the tangential component. Finally, we
measured the dispersion of the angular momentum Lz for the three main
subpopulations along the main sequence, which provides further
evidence of the differences in the velocity anisotropy of 1G and 2G
stars and shows marginal evidence for the most extreme
second-generation subpopulation being slightly more radially
anisotropic than the other second-generation subpopulation.
Description:
Astro-photometric catalog of NGC 2808 based on HST data.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
ngc2808.dat 132 202482 Astrometric catalog
f275w4ph.dat 52 202482 *Photometric catalog for filter F275W and epoch 4
f275w5ph.dat 52 202482 *Photometric catalog for filter F275W and epoch 5
f475w1ph.dat 52 202482 *Photometric catalog for filter F475W and epoch 1
f475w2ph.dat 52 202482 *Photometric catalog for filter F475W and epoch 2
f475w4ph.dat 52 202482 *Photometric catalog for filter F475W and epoch 4
f475w5ph.dat 52 202482 *Photometric catalog for filter F475W and epoch 5
f814w2ph.dat 52 202482 *Photometric catalog for filter F814W and epoch 2
f814w4ph.dat 52 202482 *Photometric catalog for filter F814W and epoch 4
f814w5ph.dat 52 202482 *Photometric catalog for filter F814W and epoch 5
f275-814.dat 45 202482 Photometric catalogs in the F275W and F814W
filters as used in the paper,
corrected for differential reddening
f475-814.dat 45 202482 Photometric catalogs in the F475W and F814W
filters as used in the paper,
corrected for differential reddening
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Note on f???w?ph.dat : Zero-points:
Epoch 1 : F475W: 32.399
Epoch 2 : F475W: 32.395, F814W: 31.802
Epoch 4 : F475W: 33.423, F814W: 31.835, F275W: 29.918
Epoch 5 : F475W: 33.422, F814W: 31.813, F275W: 29.828
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Byte-by-byte Description of file: ngc2808.dat
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Bytes Format Units Label Explanations
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1- 20 F20.15 deg RAdeg Right ascension (ICRS) at Ep=2016.0
22- 41 F20.15 deg DEdeg Declination (ICRS) at Ep=2016.0
43- 50 F8.3 mas/yr pmRA Proper motion along right ascension (1)
52- 59 F8.3 mas/yr e_pmRA Error on pmRA
61- 68 F8.3 mas/yr pmDE Proper motion along declination (1)
70- 77 F8.3 mas/yr e_pmDE Error on pmDE
79- 85 F7.3 --- cx chi2 of the pmRA fit
87- 93 F7.3 --- cy chi2 of the pmDE fit
95- 96 I2 --- ls Number of epochs where the source was measured
98- 99 I2 --- u Number of epochs used in the fit
101-106 F6.3 yr dt Temporal baseline of the data used in the fit
111 I1 --- good Flag equal to one if the source passed our
cuts, zero otherwise
117 I1 --- popID [0/3] Population tagging
(1 = bMS, 2 = mMS, 3 = rMS)
125 I1 --- goodHRC [0/1] Flag equal to one if the source passed
our cuts, zero otherwise
(only applies to stars measured in HRC data)
127-132 I6 --- nStar Star number
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Note (1): Proper motions include all the corrections described in the paper.
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Byte-by-byte Description of file: f275w4ph.dat f275w5ph.dat
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Bytes Format Units Label Explanations
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1- 7 F7.3 mag mF275W ?=999 Magnitude in F275W band (Vega)
9- 15 F7.3 mag e_mF275W ?=999 Error on magnitude
17- 21 F5.3 --- qfit Quality of fit
23- 29 F7.3 --- radxs Radxs parameter
31- 39 F9.3 --- o Fraction of flux contamination due to neighbors
41- 42 I2 --- f Number of images where the source was found
44- 45 I2 --- g Number of images used to measure the source
47- 52 I6 --- nStar Star number
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Byte-by-byte Description of file: f475w?ph.dat
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Bytes Format Units Label Explanations
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1- 7 F7.3 mag mF475W ?=999 Magnitude in F475W band (Vega)
9- 15 F7.3 mag e_mF475W ?=999 Error on magnitude
17- 21 F5.3 --- qfit Quality of fit
23- 29 F7.3 --- radxs Radxs parameter
31- 39 F9.3 --- o Fraction of flux contamination due to neighbors
41- 42 I2 --- f Number of images where the source was found
44- 45 I2 --- g Number of images used to measure the source
47- 52 I6 --- nStar Star number
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Byte-by-byte Description of file: f814w2ph.dat f814w4ph.dat f814w5ph.dat
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Bytes Format Units Label Explanations
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1- 7 F7.3 mag mF814W ?=999 Magnitude in F814W band (Vega)
9- 15 F7.3 mag e_mF814W ?=999 Error on magnitude
17- 21 F5.3 --- qfit Quality of fit
23- 29 F7.3 --- radxs Radxs parameter
31- 39 F9.3 --- o Fraction of flux contamination due to neighbors
41- 42 I2 --- f Number of images where the source was found
44- 45 I2 --- g Number of images used to measure the source
47- 52 I6 --- nStar Star number
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Byte-by-byte Description of file: f275-814.dat
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Bytes Format Units Label Explanations
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1- 7 F7.3 mag mF275W ?=999 Magnitude in F275W band (Vega) (1)
9- 15 F7.3 mag mF814W ?=999 Magnitude in F814W band (Vega) (1)
17- 22 F6.3 --- DRc Differential reddening correction along the
reddening vector
24- 28 F5.3 --- e_DRc Error on DRc
30- 31 I2 --- nu Number of stars used to compute DRc
33- 36 I4 pix ru Maximun distance of the stars used to compute
DRc [UVIS pixels]
38 I1 --- use [0/1] Flag equal to one if the star was
measured in both filters, zero otherwise
40- 45 I6 --- nStar Star number
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Note (1): Sources that did not pass our quality cuts in mF275W and mF814W have
both magnitude columns set to 999.
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Byte-by-byte Description of file: f475-814.dat
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Bytes Format Units Label Explanations
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1- 7 F7.3 mag mF475W ?=999 Magnitude in F475W band (Vega) (1)
9- 15 F7.3 mag mF814W ?=999 Magnitude in F814W band (Vega) (1)
17- 22 F6.3 --- DRc Differential reddening correction along
the reddening vector (2)
24- 28 F5.3 --- e_DRc Error on DRc
30- 31 I2 --- nu Number of stars used to compute DRc
33- 36 I4 pix ru Maximum distance of the stars used to compute
DRc [UVIS pixels]
38 I1 --- use [0/1] Flag equal to one if the star was
measured in both filters, zero otherwise
40- 45 I6 --- nStar Star number
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Note (1): Sources that did not pass our quality cuts in mF475W and mF814W have
both magnitude columns set to 999.
Note (2): Extinction coefficients:
ACS/WFC : A_F475W = 1.21179, A_F814W = 0.59696
WFC3/UVIS : A_F275W = 2.02499
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Acknowledgements:
Massimo Griggio, mgriggio(at)stsci.edu
(End) Massimo Griggio [STScI], Patricia Vannier [CDS] 16-May-2025