J/ApJ/966/159 NGVS. XXXVII. RR Lyrae stars out to 300kpc (Feng+, 2024)
The Next Generation Virgo Cluster Survey.
XXXVII. Distant RR Lyrae stars and the Milky Way stellar halo out to 300 kpc.
Feng Y., Guhathakurta P., Peng E.W., Gwyn S.D.J., Ferrarese L., Cote P.,
Cuillandre J.-C., Munsell J., Talukdar M.
<Astrophys. J., 966, 159 (2024)>
=2024ApJ...966..159F 2024ApJ...966..159F
ADC_Keywords: Stars, variable; Photometry, ugriz; Stars, distances; Stars, halo
Keywords: Milky Way stellar halo ; RR Lyrae variable stars
Abstract:
RR Lyrae stars are standard candles with characteristic photometric
variability and serve as powerful tracers of Galactic structure,
substructure, accretion history, and dark matter content. Here we
report the discovery of distant RR Lyrae stars, including some of the
most distant stars known in the Milky Way halo, with Galactocentric
distances of ∼300kpc. We use time-series u*g'i'z' Canada-France-Hawaii
Telescope/MegaCam photometry from the Next Generation Virgo Cluster
Survey (NGVS). We use a template light-curve fitting method based on
empirical Sloan Digital Sky Survey Stripe 82 RR Lyrae data to identify
RR Lyrae candidates in the NGVS data set. We eliminate several hundred
suspected quasars and identify 180 RR Lyrae candidates with
heliocentric distances of ∼20-300kpc. The halo stellar density
distribution is consistent with an r-4.09±0.10 power-law radial
profile over most of this distance range with no signs of a break. The
distribution of ab-type RR Lyrae in a period-amplitude plot (Bailey
diagram) suggests that the mean metallicity of the halo decreases
outward. Compared to other recent RR Lyrae surveys, like Pan-STARRS1,
the High Cadence Transient Survey, and the Dark Energy Survey, our
NGVS study has better single-epoch photometric precision and a
comparable number of epochs but smaller sky coverage. At large
distances, our RR Lyrae sample appears to be relatively pure and
complete, with well-measured periods and amplitudes. These newly
discovered distant RR Lyrae stars are important additions to the few
secure stellar tracers beyond 150 kpc in the Milky Way halo.
Description:
The Next Generation Virgo Cluster Survey (NGVS) is a deep optical
imaging survey of the Virgo cluster of galaxies, carried out with the
1deg2 MegaCam instrument on the 3.6m Canada-France-Hawaii Telescope
(CFHT) in the u*, g', i', and z' bands. The survey consists of 117
pointings (not including four background pointings), with a slight
overlap between adjacent pointings. The resulting NGVS footprint
covers a contiguous area of 104deg2 of the nearby Virgo cluster, out
to the virial radii for both the Virgo A and B subclusters.
This paper is based on all NGVS single-exposure images obtained during
the period of 2009 March through 2013 May. The total number of epochs
across the four bands is roughly the same (∼38) for each MegaCam
pointing (tile in the survey mosaic), with the exception of small
overlap regions between adjacent pointings, which have twice as many
epochs or more. The single-exposure integration times (and approximate
number of exposures per band) are 582s (x13) in u*, 634s (x7) in g',
411s (x8) in i', and 550s (x10) in z'.
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 119 180 Catalog of NGVS RR Lyrae stars
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See also:
B/cfht : Log of CFHT Exposures (CADC, 1979-)
J/AJ/115/193 : RR Lyrae V light curves (Layden, 1998)
J/ApJ/708/717 : Light curve templates of RR Lyrae stars (Sesar+, 2010)
J/ApJ/781/22 : Region I of La Silla QUEST RR Lyrae survey (Zinn+, 2014)
J/ApJ/812/34 : UCD candidates in M87/M49/M60 regions (Liu+, 2015)
J/AJ/153/204 : RR Lyrae stars from the PS1 3π survey (Sesar+, 2017)
J/ApJ/855/43 : Distant RR Lyrae stars discovered with HiTS (Medina+, 2018)
J/A+A/618/A185 : VI magnitudes of NGC 4535 stars (Spetsieri+, 2018)
J/ApJ/911/109 : RR Lyrae variable stars in DES Y6 (Stringer+, 2021)
J/MNRAS/503/5263 : 4XMM-DR9 sources with machine learning (Zhang+, 2021)
J/A+A/660/A35 : VVV survey. Long-period variable stars (Nikzat+, 2022)
http://www.cfht.hawaii.edu/Science/NGVS/ : NGVS homepage on CFHT
Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 5 A5 --- --- [NGVS-]
6- 24 A19 --- NGVS NGVS identifier (JHHMMSS.ss+DDMMSS.s)
26- 36 F11.7 deg RAdeg [181.99/193.4] Right Ascension (J2000)
38- 47 F10.7 deg DEdeg [5.49/17.8] Declination (J2000)
49- 53 F5.2 mag umag [18/24.01] Mean CFHT/MegaCam u*-band apparent
magnitude
55- 59 F5.2 mag gmag [17.85/23.31] Mean CFHT/MegaCam g'-band
apparent magnitude
61- 65 F5.2 mag imag [17.63/22.67] Mean CFHT/MegaCam i'-band
apparent magnitude
67- 71 F5.2 mag zmag [17.62/22.46] Mean CFHT/MegaCam z'-band
apparent magnitude
73- 78 F6.2 kpc DHelio [26.8/296.3] Heliocentric distance
80- 83 F4.2 mag uAmp [0.19/1.6] Amplitude in u*-band
85- 88 F4.2 mag gAmp [0.18/1.56] Amplitude in g'-band
90- 93 F4.2 mag iAmp [0.08/1.33] Amplitude in i'-band
95- 98 F4.2 mag zAmp [0.12/0.84] Amplitude in z'-band
100- 110 F11.9 d Period [0.2/0.93] Pulsation period
112- 113 A2 --- Type RR Lyra type ("ab": 141 occurrences" or
"c": 39 occurrences)
115- 119 F5.3 --- Phase [0.002/1] Phase
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History:
From electronic version of the journal
License: CC-BY-4.0
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(End) Prepared by [AAS], Emmanuelle Perret [CDS] 05-Aug-2026