J/ApJ/853/86 HST large programme on ω Centauri. II. (Bellini+, 2018)
The HST large programme on ω Centauri.
II. Internal kinematics.
Bellini A., Libralato M., Bedin L.R., Milone A.P., van der Marel R.P.,
Anderson J., Apai D., Burgasser A.J., Marino A.F., Rees J.M.
<Astrophys. J., 853, 86 (2018)>
=2018ApJ...853...86B 2018ApJ...853...86B
ADC_Keywords: Clusters, globular; Photometry, HST; Proper motions
Keywords: Galaxy: kinematics and dynamics;
globular clusters: individual (NGC 5139); proper motions
Abstract:
In this second installment of the series, we look at the internal
kinematics of the multiple stellar populations of the globular cluster
ω Centauri in one of the parallel Hubble Space Telescope (HST)
fields, located at about 3.5 half-light radii from the center of the
cluster. Thanks to the over 15yr long baseline and the exquisite
astrometric precision of the HST cameras, well-measured stars in our
proper-motion catalog have errors as low as ∼10µas/yr, and the
catalog itself extends to near the hydrogen-burning limit of the
cluster. We show that second-generation (2G) stars are significantly
more radially anisotropic than first-generation (1G) stars. The latter
are instead consistent with an isotropic velocity distribution. In
addition, 1G stars have excess systemic rotation in the plane of the
sky with respect to 2G stars. We show that the six populations below
the main-sequence (MS) knee identified in our first paper are
associated with the five main population groups recently isolated on
the upper MS in the core of cluster. Furthermore, we find both 1G and
2G stars in the field to be far from being in energy equipartition,
with η1G=-0.007±0.026 for the former and η2G=0.074±0.029
for the latter, where η is defined so that the velocity dispersion
σµ scales with stellar mass as σµ∝m-η.
The kinematical differences reported here can help constrain the
formation mechanisms for the multiple stellar populations in ω
Centauri and other globular clusters.
Description:
ω Cen is the most massive globular cluster of the Galaxy, with
an estimated mass of ∼4x106M☉, and our field F1 is located at
∼3xrh from the center. This paper focuses on field F1, which is the
only field for which all exposures have already been acquired.
Field F1 has been observed a total of four times by HST. Long ACS/WFC
observations in F606W and F814W were taken during the first two
visits, in 2002 July (GO-9444) and in 2005 December (GO-10101). More
recently, as part of our HST large program, the field was reobserved
in 2015 August (GO-14118) and 2017 August (GO-14662), using both
channels of the WFC3. In each of these two recent epochs, UVIS filters
F275W, F336W, F438W, F606W, and F814W and IR filters F110W and F160W
were utilized. The complete list of HST observations of field F1 is
reported in Table 1.
The astro-photometric catalogs obtained in Milone+ (Paper I;
2017MNRAS.469..800M 2017MNRAS.469..800M) for field F1 were constructed from the onset with
the goal of detecting fine substructures on the color-magnitude
diagram (CMD). Here our goal is to measure fine substructures on the
proper motion (PM) diagram.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 80 18 List of HST observations of field F1
table4.dat 241 5155 Photometric catalog
table6.dat 159 5155 Astrometric catalog of field F1
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See also:
B/hst : HST Archived Exposures Catalog (STScI, 2007)
VII/202 : Globular Clusters in the Milky Way (Harris, 1997)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
J/A+A/360/472 : Proper motions in omega Centauri (van Leeuwen+, 2000)
J/ApJ/654/915 : Deep FORS1 BR photometry of omega Cen (Sollima+, 2007)
J/ApJ/681/1505 : Abundances of red giants in ω Cen (Johnson+, 2008)
J/A+A/493/959 : UBV(RI)cHalpha photometry in omega Cen (Bellini+, 2009)
J/ApJ/698/2048 : Abundances of red giants in ω Cen (Johnson+, 2009)
J/ApJ/710/1032 : Proper motions in ω Cen (Anderson+, 2010)
J/AJ/140/631 : HST WFC3/UVIS photometry of omega Cen core (Bellini+, 2010)
J/ApJ/731/64 : Spectroscopy of 300 RGBs in ω Cen (Marino+, 2011)
J/ApJ/797/115 : HSTPROMO I. Observations and NGC7078 results (Bellini+, 2014)
J/ApJ/842/6 : Astro-photometric catalog of NGC 5139's core (Bellini+, 2017)
J/ApJ/844/164 : NGC5139 HST astro-photometric analysis. III. (Bellini+, 2017)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Inst HST instrument (ACS/WFC or WFC3/IR, WFC3/UVIS)
11- 17 A7 --- Epoch Epoch number
19- 23 A5 --- Filt Filter (F110W to F814W)
25- 46 A22 --- Exp Exposure(s) time
48- 52 I5 --- PID [9444/14662] Program identifier
54- 65 A12 --- PI PI name
67- 80 A14 --- Date Observation date(s)
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 7 F7.4 mag F606Wmag [15.6/29.9] F606W filter VEGA magnitude (1)
9- 15 F7.4 mag F606Wrms [0/99.99] F606W filter RMS magnitude (1)
17- 21 F5.3 --- F606WQFIT [0/1] F606W filter QFIT value
23- 32 F10.5 --- F606Wo [0/9999.99] F606W filter initial ratio (2)
34- 40 F7.4 --- F606WRADXS [-9.999/9] F606W filter RADXS parameter (3)
42 I1 --- F606Wnf [0/8] Number of single exposures star is
in F606W filter
44 I1 --- F606Wnu [0/8] Number of single measurements used to
compute photometric quantities in F606W filter
46- 51 F6.1 e F606Wsky [0/9999.9] Local sky value at star in
F606W filter (4)
53- 58 F6.1 e F606Wrmssky [0/9999.9] F606W filter RMS of the sky (4)
60- 66 F7.4 mag F814Wmag [14.8/28.9] F814W filter VEGA magnitude (1)
68- 74 F7.4 mag F814Wrms [0/99.99] F814W filter RMS magnitude (1)
76- 80 F5.3 --- F814WQFIT [0/1] F814W filter QFIT value
82- 89 F8.5 --- F814Wo [0/46.8] F814W filter initial ratio (2)
91- 97 F7.4 --- F814WRADXS [-0.7/2.5] F814W filter RADXS parameter (3)
99 I1 --- F814Wnf [0/8] Number of single exposures star is
in F814W filter
101 I1 --- F814Wnu [0/8] Number of single measurements used to
compute photometric quantities in F814W filter
103-108 F6.1 e F814Wsky [0/9999.9] Local sky value at star in F814W
filter (4)
110-115 F6.1 e F814Wrmssky [0/9999.9] F814W filter RMS of the sky (4)
117-123 F7.4 mag F110Wmag [14.5/28.8]?=99.0 HST/WFC3 IR F110W filter
VEGA magnitude (1)
125-131 F7.4 mag F110Wrms [0/99.99] F110W filter RMS magnitude (1)
133-137 F5.3 --- F110WQFIT [0/1] F110W filter QFIT value
139-148 F10.5 --- F110Wo [0/9999.9] F110W filter initial ratio (2)
150-156 F7.4 --- F110WRADXS [-9.999/9.999] F110W filter RADXS
parameter (3)
158-159 I2 --- F110Wnf [0/28] Number of single exposures star is
in F110W filter
161-162 I2 --- F110Wnu [0/28] Number of single measurements used to
compute photometric quantities in F110W filter
164-169 F6.1 e/s F110Wsky [0/1748.2] Local sky value at star in F110W
filter (5)
171-176 F6.1 e/s F110Wrmssky [0/2865] F110W filter RMS of the sky (5)
178-184 F7.4 mag F160Wmag [13.9/29.7]?=99.0 HST/WFC3 IR F160W filter
VEGA magnitude (1)
186-192 F7.4 mag F160Wrms [0/99.99] F160W filter RMS magnitude (1)
194-198 F5.3 --- F160WQFIT [0/1] F160W filter QFIT value
200-209 F10.5 --- F160Wo [0/9999.9] F160W filter initial ratio (2)
211-217 F7.4 --- F160WRADXS [-9.999/9.999] F160W filter RADXS
parameter (3)
219-220 I2 --- F160Wnf [0/28] Number of single exposures star is
in F160W filter
222-223 I2 --- F160Wnu [0/28] Number of single measurements used to
compute photometric quantities in F160W filter
225-229 F5.1 e/s F160Wsky [0/797.7] Local sky value at star in F160W
filter (5)
231-236 F6.1 e/s F160Wrmssky [0/1237.5] F160W filter RMS of the sky (5)
238-241 I4 --- ID [48/5745] Internal identifier
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Note (1): A flag value of 99.99 is used for the magnitude rms when photometry
is based on only one measurement. A flag value of zero is used for all
the other quantities when a star is not measured in a particular
filter. Undetermined local sky values are flagged with a value of 0.0,
together with the associated sky rms.
Note (2): Between light within fitting radius due to nearby neighbors
and the star's light.
Note (3): RADXS (Bedin+ 2008ApJ...678.1279B 2008ApJ...678.1279B) tells us how much flux a source has
with respect to the PSF predictions just outside the PSF core.
Galaxies and blends have large positive values of RADXS, while objects
sharper than the PSF, e.g., cosmic rays or hot pixels, have large
negative values of RADXS.
Note (4): In units of electrons.
Note (5): In units of electrons per second.
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Byte-by-byte Description of file: table6.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 F15.11 deg RAdeg [201.36/201.45] Right Ascension (J2000)
17- 31 F15.11 deg DEdeg [-47.7/-47.6] Declination (J2000)
33- 41 F9.4 pix Xpix X pixel coordinate; 0.04"/pix
43- 51 F9.4 pix Ypix Y pixel coordinate; 0.04"/pix
53- 61 F9.5 mas/yr pmRAr [-38.6/12.4] Raw proper motion along RA
times cos(DE)
63- 69 F7.5 mas/yr e_pmRAr [0.006/6] Uncertainty in pmRAr
71- 79 F9.5 mas/yr pmDEr [-26/18.2] Raw proper motion along DE
81- 87 F7.5 mas/yr e_pmDEr [0.005/7] Uncertainty in pmDEr
89- 95 F7.4 --- chi2X [0.08/55.2] Reduced χ2 of X pixel fit
97-103 F7.4 --- chi2Y [0.04/54.7] Reduced χ2 of Y pixel fit
105-106 I2 --- nf [5/55] Number of single exposures star
found in
108-109 I2 --- nu [4/55] Number of single measurements used to
compute astrometric quantities
111-118 F8.5 yr DelTime [1.9/15.2] Temporal baseline used
for proper motions
120-128 F9.5 mas/yr pmRAc [-38.5/12.4] Corrected proper motion along RA
times cos(DE)
130-136 F7.5 mas/yr e_pmRAc [0.02/6] Uncertainty in pmRAc
138-146 F9.5 mas/yr pmDEc [-26/18.1] Corrected proper motion along DE
148-154 F7.5 mas/yr e_pmDEc [0.03/7] Uncertainty in pmDEc
156-159 I4 --- ID [48/5745] Internal identifier
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History:
From electronic version of the journal
References:
Milone et al. Paper I. 2017MNRAS.469..800M 2017MNRAS.469..800M
Bellini et al. Paper II. 2018ApJ...853...86B 2018ApJ...853...86B This catalog
Libralato et al. Paper III. 2018ApJ...854...45L 2018ApJ...854...45L
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 15-Oct-2018