J/AJ/166/3 DECam observations of NGC 2808 (Johnson+, 2023)
A Wide View of the Galactic Globular Cluster NGC 2808; Red Giant and Horizontal
Branch Star Spatial Distributions.
Johnson C.I., Calamida A., Kader J.A., Ferraro I., Pilachowski C.A.,
Bono G., Mastrobuono-Battisti A., Rest A., Zenteno A., Zocchi A.
<Astron. J., 166, 3 (2023)>
=2023AJ....166....3J 2023AJ....166....3J
ADC_Keywords: Clusters, open; Photometry, ugriz; Stars, giant;
Stars, horizontal branch
Keywords: Globular star clusters
Abstract:
Wide-field and deep DECam multiband photometry, combined with HST data
for the core of the Galactic globular cluster NGC2808, allowed us to
study the distribution of various stellar subpopulations and stars in
different evolutionary phases out to the cluster tidal radius. We used
the Cugi=(u-g)-(g-i) index to identify three chemically distinct
subpopulations along the red giant branch and compared their spatial
distributions. The most light-element-enriched subpopulation (P3) is
more centrally concentrated; however, it shows a more extended
distribution in the external regions of the cluster compared to the
primordial (P1) and intermediate (P2) composition populations.
Furthermore, the P3 subpopulation centroid is off-center relative to
those of the P1 and P2 groups. We also analyzed the spatial
distribution of horizontal branch stars and found that the relative
fraction of red horizontal branch stars increases for radial distances
larger than ∼1.5', while that of the blue and hotter stars decreases.
These new observations, combined with literature spectroscopic
measurements, suggest that the red horizontal branch stars are the
progeny of all the stellar subpopulations in NGC 2808, i.e.,
primordial and light-element enhanced, while the blue stars are
possibly the result of a combination of the "hot-flasher" and the
"helium-enhanced" scenarios. A similar distribution of different red
giant branch subpopulations and horizontal branch stars was also found
for the most massive Galactic globular cluster, ω Cen, based on
combined DECam and HST data, which suggests that the two may share a
similar origin.
Description:
We collected a set of 207 ugri DECam images for NGC2808 with National
Optical Astronomy Observatory (NOAO) proposals. A set of standard
fields from SDSS Stripe 82 were also observed each night utilizing 15s
exposures for the gri bands and 30s exposures for the u band. A total
of 36 Stripe 82 images were obtained at varying air masses for each
filter. A small number of additional, deep DECam exposures of NGC 2808
were also downloaded from the NOIRLab Astro Data Archive 9 to
supplement the data described above.
Objects:
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RA (2000) DE Designation(s)
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09 12 03.09 -64 51 48.6 NGC 2808 = AKARI-IRC-V1
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 105 267 Log of NGC 2808 DECam observations
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See also:
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/AJ/109/218 : Catalogue of globular cluster profiles (Trager+ 1995)
J/ApJ/562/368 : UV photometry in NGC 2808 (Brown+, 2001)
J/ApJS/161/304 : Star clusters in Milky Way and satellites (McLaughlin+, 2005)
J/ApJ/663/1021 : Log of ω Cen scientific images (Castellani+, 2007)
J/AJ/133/1658 : ACS survey of galactic globular clusters (Sarajedini+, 2007)
J/A+A/505/117 : Abundances redgiants in 15 globular clusters (Carretta+, 2009)
J/A+A/517/A81 : 2 & 3d parameters of HB of globular clusters (Gratton+, 2010)
J/A+A/534/A123 : Horizontal branch stars in NGC 2808 (Gratton+, 2011)
J/A+A/526/A136 : Hot HB stars in ω Cen (Moehler+, 2011)
J/A+A/528/A127 : Radial velocities in the globular NGC 2808 (Moni Bidin+, 2011)
J/ApJ/754/L38 : Abundances & radial velocities of M13 giants (Johnson+, 2012)
J/ApJ/810/148 : Red giant abundances in NGC 2808 (Carretta, 2015)
J/A+A/616/A12 : Gaia DR2 sources in GC and dSph (Gaia Collaboration+, 2018)
J/A+A/618/A15 : Parameters of EHB stars in ω Cen (Latour+, 2018)
J/MNRAS/485/4906 : GC number density profiles using Gaia DR2 (de Boer+, 2019)
J/MNRAS/485/4311 : Light element discontinuities in NGC 6402 (Johnson+, 2019)
J/A+A/631/A14 : NGC 2808 stellar population spectra (Latour+, 2019)
J/MNRAS/505/5978 : Gaia EDR3 view Galactic globular clusters (Vasiliev+, 2021)
http://astroarchive.noirlab.edu/ : NOIRLab data archive
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 26 A26 --- File File identifier
28- 31 I4 yr Obs.Y [2014/2018] Observation year
33- 34 I2 "month" Obs.M Observation month
36- 37 I2 d Obs.D Observation day
39- 48 A10 --- ID Proposal identifier
50- 63 A14 --- PI Principle Investigator name
65- 65 A1 --- Filt Filter used
67- 69 I3 s Texp [10/600] Exposure time
71- 72 I2 h RAh [8/14] Hour of Right Ascension (J2000)
74- 75 I2 min RAm Minute of Right Ascension (J2000)
77- 81 F5.2 s RAs Second of Right Ascension (J2000)
83- 83 A1 --- DE- Sign of the Declination (J2000)
84- 85 I2 deg DEd Degree of Declination (J2000)
87- 88 I2 arcmin DEm Arcminute of Declination (J2000)
90- 93 F4.1 arcsec DEs Arcsecond of Declination (J2000)
95- 99 F5.3 arcsec Seeing [0.76/2.22] Seeing
101-105 F5.3 --- Air [1.15/1.99] Airmass
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History:
From electronic version of the journal
(End) Prepared by [AAS], Coralie Fix [CDS], 26-Jan-2024