J/ApJ/752/42 BV time series in Ursa Major II (Dall'Ora+, 2012)
Stellar archaeology in the Galactic halo with the ultra-faint dwarfs.
VI. Ursa Major II.
Dall'Ora M., Kinemuchi K., Ripepi V., Rodgers C.T., Clementini G.,
Di Fabrizio L., Smith H.A., Marconi M., Musella I., Greco C., Kuehn C.A.,
Catelan M., Pritzl B.J., Beers T.C.
<Astrophys. J., 752, 42 (2012)>
=2012ApJ...752...42D 2012ApJ...752...42D
ADC_Keywords: Photometry, UBV ; Galaxies, optical
Keywords: galaxies: dwarf - galaxies: individual: Ursa Major II -
stars: distances - stars: variables: RR Lyrae -
techniques: photometric
Abstract:
We present a B, V color-magnitude diagram (CMD) of the Milky Way dwarf
satellite Ursa Major II (UMa II), spanning the magnitude range from
V∼15 to V∼23.5mag and extending over an 18x18 arcmin2 area centered
on the Galaxy. Our photometry goes down to about 2 mag below the
Galaxy's main-sequence turnoff that we detected at V∼21.5 mag. We have
discovered a bona fide RR Lyrae variable star in UMa II, which we use
to estimate a conservative dereddened distance modulus for the galaxy
of (m-M)0=17.70±0.04±0.12mag, where the first error accounts for
the uncertainties of the calibrated photometry, and the second
reflects our lack of information on the metallicity of the star. The
corresponding distance to UMa II is 34.7+0.6-0.7(+2.0-1.9)kpc.
Our photometry shows evidence of a spread in the Galaxy's subgiant
branch, compatible with a spread in metal abundance in the range
between Z=0.0001 and Z=0.001. Based on our estimate of the
distance, a comparison of the fiducial lines of the Galactic globular
clusters M68 and M5 ([Fe/H]=-2.27±0.04 dex and -1.33±0.02 dex,
respectively), with the position on the CMD of spectroscopically
confirmed Galaxy members, may suggest the existence of stellar
populations of different metal abundance/age in the central region of
UMa II.
Description:
Time-series observations of UMa II were obtained between 2007 January
and March with three different telescopes. At the Wyoming Infrared
Observatory (WIRO) 2.3m telescope, using the WIRO Prime Focus Camera,
we obtained 40 images in Johnson V, 12 images in Johnson B, and 22
images in Cousins I. At the 1.8m Perkins telescope of the Lowell
Observatory, we used the Perkins Re-Imaging SysteM (PRISM) instrument
in photometry mode to obtain 12 V, 4 B, and 4 I images of UMa II. Five
nights at the Loiano Observatory 1.5m telescope provided 14 B and 15 V
images using the Bologna Faint Object Spectrograph and Camera (BFOSC).
Objects:
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RA (2000) DE Designation(s)
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08:50:37.43 +63:10:10.0 RR Lyr in UMa II = [DKR2012] 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 31 50 B, V Photometry of the RR Lyrae stars detected
in UMa II
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See also:
J/AJ/144/4 : Dwarf galaxies in the Local Group (McConnachie+, 2012)
J/ApJ/708/560 : Spectroscopy of UMa II and Coma Ber (Frebel+, 2010)
J/ApJ/674/L81 : Paper II. Variable stars in dwarf galaxy CVn I (Kuehn+, 2008)
J/MNRAS/380/281 : Faint Galactic satellites spectrosc. survey (Martin+, 2007)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 F9.6 d B-HJD ? Heliocentric Julian Date of B band
observation; HJD-2454116 (1)
11- 15 F5.2 mag Bmag [17.9/19.3]? The B band magnitude (Johnson system)
17- 25 F9.6 d V-HJD Heliocentric Julian Date of V band
observation; HJD-2454116
27- 31 F5.2 mag Vmag [17.8/19] The V band magnitude (Johnson system)
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Note (1): B-HJD was originally defined as HJD-2454116 -- a day was added
at CDS to use an identical offset for both colors.
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History:
From electronic version of the journal
References:
Dall'Ora et al. Paper I : Bootes I 2006ApJ...653L.109D 2006ApJ...653L.109D
Kuehn et al. Paper II : CVn I 2008ApJ...674L..81K 2008ApJ...674L..81K Cat. J/ApJ/674/L81
Greco et al. Paper III: CVn II 2008ApJ...675L..73G 2008ApJ...675L..73G
Musella et al. Paper IV : Coma 2009ApJ...695L..83M 2009ApJ...695L..83M
Moretti et al. Paper V : Leo IV 2009ApJ...699L.125M 2009ApJ...699L.125M
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 21-Jan-2014