J/MNRAS/398/1757 RR Lyraes in SDSS stripe 82 (Watkins+, 2009)
Substructure revealed by RR Lyraes in SDSS stripe 82.
Watkins L.L., Evans N.W., Belokurov V., Smith M.C., Hewett P.C.,
Bramich D.M., Gilmore G.F., Irwin M.J., Vidrih S., Wyrzykowski L.,
Zucker D.B.
<Mon. Not. R. Astron. Soc., 398, 1757-1770 (2009)>
=2009MNRAS.398.1757W 2009MNRAS.398.1757W
ADC_Keywords: Stars, variable ; Photometry, SDSS
Keywords: catalogues - astrometry - stars: variables: other - Galaxy: halo -
Galaxy: stellar content - Galaxy: structure
Abstract:
We present an analysis of the substructure revealed by RR Lyraes in
Sloan Digital Sky Survey Stripe 82, which covers 2.5° in
declination on the celestial equator over the right ascension range
α=20.7h to 3.3h. We use the new public archive of light-motion
curves in Stripe 82, published by Bramich et al. in 2008 (Cat. V/141),
to identify a set of high-quality RR Lyrae candidates. Period
estimates are determined to high accuracy using a string-length
method. A subset of 178 RR Lyraes with spectrally derived
metallicities are employed to derive metallicity-period-amplitude
relations, which are then used, together with archive magnitude data
and light-curve Fourier decomposition, to estimate metallicities and
hence distances for the entire sample. The RR Lyraes lie 5-115kpc from
the Galactic Centre, with distance estimates accurate to ∼8%. The RR
Lyraes are further divided into subsets of 316 RRab types and 91 RRc
types based on their period, colour and metallicity.
We fit a smooth density law to the distribution as a simple
representation of the data. For Galactocentric radii 5-25kpc the
number density of RR Lyraes falls as r-2.4, but beyond 25kpc,
the number density falls much more steeply, as r-4.5. However,
we stress that in practice the density distribution is not smooth, but
dominated by clumps and substructure. Samples of 55 and 237 RR Lyraes
associated with the Sagittarius Stream and the Hercules-Aquila Cloud,
respectively, are identified. Hence, ∼70% of the RR Lyraes in Stripe
82 belong to known substructure, and the sharp break in the density
law reflects the fact that the dominant substructure in Stripe 82 -
the Hercules-Aquila Cloud and the Sagittarius Stream - lie within
40kpc. In fact, almost 60% of all the RR Lyraes in Stripe 82 are
associated with the Hercules-Aquila Cloud alone, which emphasizes the
cloud's pre-eminence. Additionally, evidence of a new and distant
substructure - the Pisces Overdensity - is found, consisting of 28
faint RR Lyraes centred on Galactic coordinates (l∼80°,
b~-55°), with distances of ∼80kpc. The total stellar mass in the
Pisces Overdensity is ∼104M☉ and its metallicity is
[Fe/H]~-1.5.
Description:
In this paper, we select first the variable objects in Stripe 82 and
then the subset of RR Lyraes, using the Bramich et al.
(2008MNRAS.386..887B 2008MNRAS.386..887B, Cat. V/141) light-motion curve catalogue (LMCC)
and HLC. We make a selection of the variable objects and an
identification of RR Lyrae stars.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
vars.dat 137 21939 Variable star-like objects in SDSS Stripe 82
lyraes.dat 228 407 RR Lyraes in SDSS Stripe 82
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See also:
V/141 : Light-Motion Curve Catalogue (LMCC) in Stripe 82 (Bramich+ 2008)
Byte-by-byte Description of file: vars.dat
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Bytes Format Units Label Explanations
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1- 31 A31 --- LC Lightcurve name (in the LMCC and HLC from
Bramich et al. 2008MNRAS.386..887B 2008MNRAS.386..887B, Cat. V/141)
34- 35 I2 h RAh Right ascension (J2000)
37- 38 I2 min RAm Right ascension (J2000)
40- 43 F4.1 s RAs Right ascension (J2000)
46 A1 --- DE- Declination sign (J2000)
47- 48 I2 deg DEd Declination (J2000)
50- 51 I2 arcmin DEm Declination (J2000)
53- 54 I2 arcsec DEs Declination (J2000)
57- 62 F6.3 mag umag Apparent u band magnitude
65- 69 F5.3 mag e_umag Uncertainty in umag
72- 77 F6.3 mag gmag Apparent g band magnitude
80- 84 F5.3 mag e_gmag Uncertainty in gmag
87- 92 F6.3 mag rmag Apparent r band magnitude
95- 99 F5.3 mag e_rmag Uncertainty in rmag
102-107 F6.3 mag imag Apparent i band magnitude
110-114 F5.3 mag e_imag Uncertainty in imag
117-122 F6.3 mag zmag Apparent z band magnitude
125-129 F5.3 mag e_zmag Uncertainty in zmag
132-137 F6.4 d Per [0.21/0.82]?=0 Period of variability (1)
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Note (1): Periods are given for objects determined to be RR Lyraes.
For all other objects, periods are given as 0.
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Byte-by-byte Description of file: lyraes.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 31 A31 --- LC Lightcurve name (in the LMCC and HLC from
Bramich et al. 2008MNRAS.386..887B 2008MNRAS.386..887B, Cat. V/141)
34- 35 I2 h RAh Right ascension (J2000)
37- 38 I2 min RAm Right ascension (J2000)
40- 43 F4.1 s RAs Right ascension (J2000)
46 A1 --- DE- Declination sign (J2000)
47- 48 I2 deg DEd Declination (J2000)
50- 51 I2 arcmin DEm Declination (J2000)
53- 54 I2 arcsec DEs Declination (J2000)
57- 62 F6.3 mag umag Apparent u-band magnitude
65- 69 F5.3 mag e_umag Uncertainty in umag
72- 77 F6.3 mag gmag Apparent g-band magnitude
80- 84 F5.3 mag e_gmag Uncertainty in gmag
87- 92 F6.3 mag rmag Apparent r-band magnitude
95- 99 F5.3 mag e_rmag Uncertainty in rmag
102-107 F6.3 mag imag Apparent i-band magnitude
110-114 F5.3 mag e_imag Uncertainty in imag
117-122 F6.3 mag zmag Apparent z-band magnitude
125-129 F5.3 mag e_zmag Uncertainty in zmag
132-137 F6.4 d Per [0.21/0.82] Period of variability
140-141 A2 --- RR RR Lyrae type (ab or c)
144-147 F4.2 mag gAmp [0.1/0.8] g-band amplitude
150-153 F4.2 mag rAmp [0.1/0.6] r-band amplitude
156-160 F5.2 [Sun] [Fe/H] [-3.1/-0.8] Metallicity
163-166 F4.2 [Sun] e_[Fe/H] [0.2/0.9] Uncertainty in [Fe/H]
169-172 F4.2 mag zMAG [0.11/1.1] z-band absolute magnitude
175-180 F6.2 kpc Dist [4/108] Heliocentric distance
183-187 F5.2 kpc e_Dist [0.1/58] Uncertainty in Dist
190-196 F7.2 --- gcsq [19/2006] g-band χ-squared
199-205 F7.2 --- rcsq [8.67/1494.85] r-band χ-squared
208-211 F4.2 mag grms [0.1/0.56] g-band RMS
214-217 F4.2 mag rrms [0.07/0.41] r-band RMS
220-224 F5.2 --- Lg [2.56/33.92] g-band Stetson index
227-228 A2 --- Assoc Association (1)
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Note (1): Associations are:
HA = associated with Hercules-Aquila Cloud
SS = Sagittarius Stream
PI = Pisces Overdensity
-- = no association
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Acknowledgements:
Dan Bramich, dan.bramich(at)hotmail.co.uk
(End) Patricia Vannier [CDS] 05-Oct-2015