J/ApJ/758/11 Bayesian distances to M31 satellites (Conn+, 2012)
A Bayesian approach to locating the red giant branch tip magnitude.
II. Distances to the satellites of M31.
Conn A.R., Ibata R.A., Lewis G.F., Parker Q.A., Zucker D.B., Martin N.F.,
McConnachie A.W., Irwin M.J., Tanvir N., Fardal M.A., Ferguson A.M.N.,
Chapman S.C., Valls-Gabaud D.
<Astrophys. J., 758, 11 (2012)>
=2012ApJ...758...11C 2012ApJ...758...11C
ADC_Keywords: Galaxies, nearby ; Stars, distances ; Stars, giant
Keywords: galaxies: general; galaxies: stellar content; Local Group
Abstract:
In "A Bayesian Approach to Locating the Red Giant Branch Tip Magnitude
(Part I)," a new technique was introduced for obtaining distances
using the tip of the red giant branch (TRGB) standard candle. Here we
describe a useful complement to the technique with the potential to
further reduce the uncertainty in our distance measurements by
incorporating a matched-filter weighting scheme into the model
likelihood calculations. In this scheme, stars are weighted according
to their probability of being true object members. We then re-test our
modified algorithm using random-realization artificial data to verify
the validity of the generated posterior probability distributions
(PPDs) and proceed to apply the algorithm to the satellite system of
M31, culminating in a three-dimensional view of the system. Further to
the distributions thus obtained, we apply a satellite-specific prior
on the satellite distances to weight the resulting distance posterior
distributions, based on the halo density profile. Thus in a single
publication, using a single method, a comprehensive coverage of the
distances to the companion galaxies of M31 is presented, encompassing
the dwarf spheroidals Andromedas I-III, V, IX-XXVII, and XXX along
with NGC 147, NGC 185, M33, and M31 itself. Of these, the distances to
Andromedas XXIV-XXVII and Andromeda XXX have never before been derived
using the TRGB. Object distances are determined from high-resolution
tip magnitude posterior distributions generated using the Markov Chain
Monte Carlo technique and associated sampling of these distributions
to take into account uncertainties in foreground extinction and the
absolute magnitude of the TRGB as well as photometric errors. The
distance PPDs obtained for each object both with and without the
aforementioned prior are made available to the reader in tabular form.
The large object coverage takes advantage of the unprecedented size
and photometric depth of the Pan-Andromeda Archaeological Survey.
Description:
We utilize the data of the Pan-Andromeda Archaeological Survey
(PAndAS; McConnachie et al. 2009Natur.461...66M 2009Natur.461...66M), a two-color
(i'=770nm, g'=487nm) panoramic survey of the entire region around M31
and M33 undertaken using the Canada-France-Hawaii Telescope (CFHT).
The tip is measured in the i' band where dependence on metallicity is
minimal.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 28 2800 Tabulated distance posterior distributions
table2.dat 169 40 M31 satellite parameters: distance and associated
parameters of M31 and its companions
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See also:
VII/233 : The 2MASS Extended sources (IPAC/UMass, 2003-2006)
J/ApJ/752/45 : SPLASH: Stellar spectro. of M31 satellites (Tollerud+, 2012)
J/ApJ/711/361 : Local Group dE galaxies. II. (Geha+, 2010)
J/A+A/509/A70 : Study of an eclipsing binary in M31 (Vilardell+, 2010)
J/AJ/138/332 : LEDA CMD/tip of the red giant branch (Jacobs+, 2009)
J/ApJ/703/L72 : Hipparcos calibration of the TRGB (Tabur+, 2009)
J/other/A+ARV/15.289 : Distances of local galaxies (Tammann+, 2008)
J/ApJ/652/313 : A detached eclipsing binary phot. in M 33 (Bonanos+, 2006)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Source name
16- 18 I3 % Perc [1/100] Probability percentage (1)
20- 23 I4 kpc Dist1 [384/1543] Distance; no halo density prior (1)
25- 28 I4 kpc Dist2 [0/1543] Distance; angle-specific prior (1)
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Note (1): Distance posterior probability distributions given at 1%
intervals for the case of no halo density prior (Dist1) and with the
angle-specific prior outlined in Section 3.3 applied (Dist2).
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 9 A9 --- AName Abbreviated name
11- 16 A6 --- OName Alternative name (1)
18- 22 F5.2 mag DM [23.3/25.5]? Distance modulus (2)
24- 27 F4.2 mag E_DM [0.05/0.6]? Positive error on DM
29- 32 F4.2 mag e_DM [0.05/1.1]? Negative error on DM
34- 38 F5.3 mag E(B-V) [0.04/0.2]? Extinction (3)
40- 43 I4 kpc Dist [476/1255]? Distance (4)
45- 47 I3 kpc E_Dist [15/218]? Positive error on Dist
49- 51 I3 kpc e_Dist [15/474]? Negative error on Dist
53- 55 I3 kpc M31D [67/482]? M31 distance
57- 59 I3 kpc E_M31D [0/234]? Positive error on M31D (5)
61- 63 I3 kpc e_M31D [1/425]? Negative error on M31D (5)
65- 68 I4 kpc Distl [525/1355] Alternative literature distance
70- 72 I3 kpc B_Distl [738/955]? Upper range value for Distl
74- 76 I3 kpc E_Distl [15/360]? Positive error on Distl
78- 80 I3 kpc e_Distl [0/361]? Negative error on Distl
82- 92 A11 --- Meth Distance method (6)
94 A1 --- f_Meth [m] m: MCMC (Markov Chain Monte Carlo) without
MF (mean-field approximation)
96-113 A18 --- Auth Author's name(s)
115-133 A19 --- BibCode Bibcode
135-154 A20 --- Comm Comment on reference
156-169 A14 --- Name Source name as in table 1 (column added by CDS)
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Note (1):
a = Andromeda XXX is a new discovery, and will also be known as Cassiopeia II,
being the second dwarf spheroidal satellite of M31 to be discovered in
the constellation of Cassiopeia (M.J. Irwin 2012, in preparation).
Note (2): The distance modulus µ is (Eq.1):
µ(K)=miTRGB(K)-Aλ(K)-MiTRGB(K),
where each of mTRGBi(K), Aλ(K), and MTRGBi(K) is the
values drawn from the uncertainty distributions in the tip position,
foreground extinction, and absolute magnitude of the tip, respectively.
See section 2.
Note (3): Values for the extinction in MegaCam i band have been adopted as
Aλ=2.086xE(B-V), with uncertainties taken as ±10%. The
extinction values quoted are for the object centers, though the actual
calculations apply individual corrections to each member star according to
their coordinates. See section 4.3.
Note (4): All distance measurements utilize the data from the Pan-Andromeda
Archaeological Survey (McConnachie et al. 2009Natur.461...66M 2009Natur.461...66M) and
have been obtained using the method presented in this paper. A value
of MTRGBi=-3.44±0.05 is assumed for the absolute magnitude of
the RGB tip in CFHT MegaCam i band, based on the value identified for
the SDSS i band (Bellazzini 2008MmSAI..79..440B 2008MmSAI..79..440B) and justified for use
here by the color equations applicable to the new MegaCam i-band
filter (Gwyn 2010, http://cadcwww.dao.nrc.ca/megapipe/docs/filters.html).
TRGB-derived distances are quoted wherever possible.
Note (5): Note that the uncertainties in the M31 distance are based on the
sampled distributions while the quoted value is that derived directly
from the Earth distance as per Equation (7).
Note (6): Distance derivation methods as follows:
TRGB = tip of the red giant branch;
Ceph = Cepheid period-luminosity relation;
RR Ly = RR Lyrae period-luminosity relation;
RC = red clump;
HB = horizontal branch;
DEB = detached eclipsing binary.
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History:
From electronic version of the journal
References:
Conn et al. Paper I. 2011ApJ...740...69C 2011ApJ...740...69C
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 27-Jun-2014