J/AJ/144/4 Properties of dwarf galaxies in the Local Group (McConnachie+, 2012)
The observed properties of dwarf galaxies in and around the Local Group.
McConnachie A.W.
<Astron. J., 144, 4 (2012)>
=2012AJ....144....4M 2012AJ....144....4M
ADC_Keywords: Galaxies, nearby ; Positional data ; Radial velocities ;
Rotational velocities ; Abundances, [Fe/H] ; Extinction ;
Velocity dispersion ; Photometry, UBV
Keywords: catalogs - galaxies: dwarf - galaxies: fundamental parameters -
galaxies: general - galaxies: structure - Local Group
Abstract:
Positional, structural, and dynamical parameters for all dwarf
galaxies in and around the Local Group are presented, and various
aspects of our observational understanding of this volume-limited
sample are discussed. Over 100 nearby galaxies that have distance
estimates reliably placing them within 3Mpc of the Sun are
identified. This distance threshold samples dwarfs in a large range of
environments, from the satellite systems of the MW and M31, to the
quasi-isolated dwarfs in the outer regions of the Local Group, to the
numerous isolated galaxies that are found in its surroundings. It
extends to, but does not include, the galaxies associated with the
next nearest groups, such as Maffei, Sculptor, and IC 342. Our basic
knowledge of this important galactic subset and their resolved stellar
populations will continue to improve dramatically over the coming
years with existing and future observational capabilities, and they
will continue to provide the most detailed information available on
numerous aspects of dwarf galaxy formation and evolution. Basic
observational parameters, such as distances, velocities, magnitudes,
mean metallicities, as well as structural and dynamical
characteristics, are collated, homogenized (as far as possible), and
presented in tables that will be continually updated to provide a
convenient and current online resource. As well as discussing the
provenance of the tabulated values and possible uncertainties
affecting their usage, the membership and spatial extent of the MW
sub-group, M31 sub-group, and the Local Group are explored. The
morphological diversity of the entire sample and notable sub-groups is
discussed, and timescales are derived for the Local Group members in
the context of their orbital/interaction histories. The scaling
relations and mean stellar metallicity trends defined by the dwarfs
are presented, and the origin of a possible "floor" in central surface
brightness (and, more speculatively, stellar mean metallicity) at
faint magnitudes is considered.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 167 102 Basic information
table2.dat 136 102 Positions and velocities
table3.dat 199 102 Luminosity and structural parameters
table4.dat 304 102 Masses and kinematics
table5.dat 139 102 Mean stellar metallicities
refs.dat 320 319 References
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See also:
VII/34 : ESO/Uppsala Survey of the ESO(B) Atlas (Lauberts 1982)
J/MNRAS/411/1013 : CaII triplet in Sextans dSph galaxy (Battaglia+, 2011)
J/ApJ/733/46 : Velocity measurements in Segue 1 (Simon+, 2011)
J/AJ/139/1168 : CaII spectroscopy of SMC fields stars (Parisi+, 2010)
J/ApJ/710/1664 : BV photometry in Leo IV and Leo V dSphs (de Jong+, 2010)
J/ApJ/711/361 : Local Group dE galaxies. II. (Geha+, 2010)
J/ApJ/723/1632 : Abundance spreads in Bootes I and Segue 1 (Norris+, 2010)
J/PAZh/35/829 : Star clusters in IC 10 (Tikhonov+, 2009)
J/ApJ/705/328 : Abundance measurements in Sculptor dSph (Kirby+, 2009)
J/MNRAS/397/1748 : Spectroscopic study of Segue 2 (Belokurov+, 2009)
J/A+A/485/41 : VLT spectroscopy of blue massive stars in NGC55
(Castro+, 2008)
J/MNRAS/384/1544 : Surface photometry of local dwarf galaxies (Sharina+, 2008)
J/AJ/135/836 : Calcium triplet index in LMC stars (Carrera+, 2008)
J/AJ/133/715 : Dwarf galaxies of the Local Group (Whiting+, 2007)
J/AJ/133/270 : Metallicities and ages in Leo II dSph (Koch+, 2007)
J/ApJ/670/346 : M giant stars in Sagittarius dwarf galaxy. V. (Chou+, 2007)
J/A+A/459/423 : VI and [Fe/H] of Fornax dSph RGB stars (Battaglia+, 2006)
J/AJ/131/332 : Velocities of individual stars in NGC 205 (Geha+, 2006)
J/AJ/131/895 : Stars in the Carina dwarf spheroidal galaxy (Koch+, 2006)
J/AJ/129/1465 : Spectroscopy of red giants in the LMC bar (Cole+, 2005)
J/AJ/128/16 : HIPASS Bright Galaxy Catalog (Koribalski+, 2004)
J/AJ/124/3222 : VI photometry of Draco and UMi galaxies (Bellazzini+, 2002)
J/MNRAS/327/918 : CaII in extragalactic red giants (Tolstoy+, 2001)
J/A+A/366/428 : HI observations of nearby dwarf galaxies
(Karachentsev+, 2001)
J/A+AS/147/187 : Second list of the Karachentsev catalog (Huchtmeier+, 2000)
J/A+AS/127/409 : New nearby dwarf galaxy candidates list
(Karachentseva+ 1998)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 4 A4 --- SubG The galactic subgroup (MW, M31 or Rest) (1)
6- 34 A29 --- Name Galaxy name
36- 67 A32 --- OName Common alternative name
69 A1 --- f_OName [*] Flag for NGC 4167 (2)
71- 73 A3 --- n_Name Indicates whether the galaxy is associated
with Milky Way (G), M31 (A), the Local Group
(L), or is nearby neighbors (N)
75- 83 A9 --- MType Morphological (Hubble) type (3)
85- 86 I2 h RAh ? Hour of Right Ascension (J2000)
88- 89 I2 min RAm ? Minute of Right Ascension (J2000)
91- 94 F4.1 s RAs ? Second of Right Ascension (J2000)
96 A1 --- DE- Sign of the Declination
98- 99 I2 deg DEd ? Degree of Declination (J2000)
101-102 I2 arcmin DEm ? Arcminute of Declination (J2000)
104-105 I2 arcsec DEs ? Arcsecond of Declination (J2000)
107-113 A7 --- Ref1 Original publication, in refs.dat file
115 A1 --- f_Ref1 [abe] Notes about discovery (4)
117-167 A51 --- Com1 Comments about basic information
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Note (1): Galactic subgroup as follows:
MW = The Milky Way sub-group (in order of distance from the Milky Way);
M31 = The M31 sub-group (in order of distance from M31);
Rest = The rest of the Local Group and its neighbors (in order of distance from
the barycenter of the Local Group).
Note (2): * = The original coordinates of NGC 4167 are coincident with the
coordinates of NGC 4163, but Sulentic & Tifft
(1973rncn.book.....S 1973rncn.book.....S) note that NGC 4167 is "non-existent".
Note (3): The distinction between dwarf elliptical (dE) and dwarf spheroidal
(dSph) is based solely on luminosity and is therefore somewhat
arbitrary. Objects fainter than MV∼18 are given a "d" (dwarf) prefix
and are again somewhat arbitrary.
Note (4): For more details relating to the discoveries of the NGC/IC galaxies,
the reader is referred to Steinicke (2010ocns.book.....S 2010ocns.book.....S).
(see also http://www.klima-luft.de/steinicke/index_e.htm)
The flag has the following meaning:
a = Discovery credited to G.B. Hodierna (see Steinicke, 2010ocns.book.....S 2010ocns.book.....S)
b = A.G. Wilson. Reported in Holmberg (1950MeLu2.128....1H 1950MeLu2.128....1H);
e = Holmberg (1950MeLu2.128....1H 1950MeLu2.128....1H) credits Wilson (1955PASP...67...27W 1955PASP...67...27W)
with discovery, but this object is not listed in this manuscript.
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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- 29 A29 --- Name Galaxy name
31 A1 --- f_Name [bk] Flag on Name (5)
33- 37 F5.1 deg GLON ? Galactic longitude l
39- 43 F5.1 deg GLAT ? Galactic latitude b
45- 49 F5.3 mag E(B-V) ? Foreground extinction (6)
51- 55 F5.2 mag (m-M) ? Distance modulus (m-M)0 (7)
57- 58 A2 --- u_(m-M) [:lbk ] Uncertain or fixed distance (5)
61- 64 F4.2 mag E_(m-M) ? Positive error in (m-M)
66- 69 F4.2 mag e_(m-M) ? Negative error in (m-M)
71- 74 I4 kpc D ? Heliocentric distance (7)
76 A1 --- u_D [:] Uncertainty flag on D
78- 80 I3 kpc E_D ? Positive error in D
82- 84 I3 kpc e_D ? Negative error in D
86- 91 F6.1 km/s HRV ? Heliocentric radial velocity (9)
93 A1 --- f_HRV [cdfmpr] Flag on HRV (10)
95- 98 F4.1 km/s e_HRV ? Error in HRV
100-103 I4 kpc D(MW) ? Distance for the Galactocentric (MW) frame
of reference (10)
105-108 I4 km/s V(MW) ? Velocity for the Galactocentric (MW) frame
of reference (10)
110-113 I4 kpc D(M31) ? Distance for the M31 frame of reference (10)
115-118 I4 km/s V(M31) ? Velocity for the M31 frame of reference (10)
120-123 I4 kpc D(LG) ? Distance for the Local Group frame of
reference (10)
125-128 I4 km/s V(LG) ? Velocity for the Local Group frame of
reference (10)
130-134 A5 --- Ref2 Reference, in refs.dat file
136 A1 --- f_Ref2 Details on Ref2 (8)
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Note (5): Peculiarities on distance/velocity, as follows:
: = uncertainty flag:
b = Significant distance/velocity gradients;
c = Corresponding to RC stars at 6<D<7kpc;
d = Carbon stars;
f = Red giant branch stars;
k = Range in distance estimates from 750≲D≲950.
l = Assumed to be at M31-M33 distance.
m = Alternative value in Gallart et al. (2001AJ....121.2572G 2001AJ....121.2572G);
p = Optical velocity suggests that Tucana is not associated with
nearby HI cloud;
r = Optical spectroscopy suggests that HRV~-70km/s; however, HI analysis
by Bellazzini et al. (2011A&A...527A..58B 2011A&A...527A..58B) gives HRV~-25km/s.
No clear reason for the discrepancy currently exists.
Note (6): These correspond to values derived by
Schlegel et al. (1998ApJ...500..525S 1998ApJ...500..525S) from an all-sky COBE/DIRBE and
IRAS/ISSA 100µm map, at the coordinates of the centroid of each
galaxy (see Section 3 for further explanations).
Note (7): All distance moduli are based on resolved stellar population
analysis (generally Cepheid, RR Lyrae, or TRGB (tip of the red giant
branch) measurements, but also horizontal branch level and
main-sequence fitting). Note that many TRGB estimates do not include
the formal uncertainty in the absolute magnitude of the TRGB
(Bellazzini et al., 2001ApJ...556..635B 2001ApJ...556..635B, 2004A&A...424..199B 2004A&A...424..199B;
Rizzi et al., 2007ApJ...661..815R 2007ApJ...661..815R).
Note (8): Flag on reference as follows:
e = For reference (16), see their Figure 8 for an excellent summary;
g = For reference (18), distance calculated using their LMC-SMC offset of
0.51±0.03 for the adopted LMC distance modulus;
h = For reference (23), also Bellazzini et al. (2002, Cat. J/AJ/124/3222),
but note that these estimates are ∼0.2 mag larger than some previous
values;
i = For reference (27), cf. Dolphin (2002MNRAS.332...91D 2002MNRAS.332...91D), which also
estimates distances by comparing real and model CMDs;
j = For reference (37), note this estimate is ∼0.2mag larger than some
previous values;
n = For reference (67), see Demers et al. (2006ApJ...636L..85D 2006ApJ...636L..85D) for
velocities of 110 C-stars;
o = For reference (69), uncertainty due to intrinsic asymmetries is gas
distribution, L. Young (2010, private communication);
q = For reference (60), see also Begum et al. (2006MNRAS.365.1220B 2006MNRAS.365.1220B);
s = For reference (81), distance calculated prior to realization that
HIZSS 3 was two systems, and will most likely correspond more closely
to the more massive A system.
Note (9): For most Local Group galaxies, the velocity corresponds to the
optical velocity of the galaxy. For some of the more distant galaxies,
velocities are measured from HI.
Note (10): These are calculated by first assuming that the barycenter of
the Local Group is located at the mid point of the vector connecting
the MW and M31 (for an adopted M31 distance modulus of (m-M)0=24.47;
McConnachie et al., 2005MNRAS.356..979M 2005MNRAS.356..979M). See Section 3 for further
explanations.
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 29 A29 --- Name Galaxy name
31 A1 --- S [h] Presence of surrounding stream (11)
33- 36 F4.1 mag Vmag ? Apparent magnitude in V; VEGA system (12)
38- 39 A2 --- u_Vmag [:kl ] Uncertain or derived Vmag (13)
42- 44 F3.1 mag E_Vmag ? Positive error in Vmag
46- 48 F3.1 mag e_Vmag ? Negative error in Vmag
50- 55 F6.2 arcmin R1 ? Radius containing half the light of the
galaxy, measured on the semimajor axis
(see Section 4 for further details)
57 A1 --- u_R1 [:] Uncertainty flag on R1
59- 63 F5.2 arcmin E_R1 ? Positive error in R1
65- 69 F5.2 arcmin e_R1 ? Negative error in R1
71- 74 F4.1 mag/arcsec2 muV ? Central surface brightness µV (14)
76- 77 A2 --- f_muV [:befg ] Note on muV (13)
80- 82 F3.1 mag/arcsec2 E_muV ? Positive error in muV
84- 86 F3.1 mag/arcsec2 e_muV ? Negative error in muV
88- 90 I3 deg PA [-69-330]? Position angle of major axis,
measured in degrees east from north (16)
92- 93 A2 --- f_PA [:ci ] Note on PA (13)
96- 97 I2 deg e_PA ? Error in PA
99-102 F4.2 --- Ell ? Ellipticity ε=1-b/a, where a and b
are the semimajor and semiminor axes (16)
104 A1 --- f_Ell [:j] Note on Ell (13)
106-109 F4.2 --- e_Ell ? Uncertainty in Ell
111-115 F5.1 mag VMag ? Absolute visual magnitude MV (15)
117 A1 --- f_VMag [:d] Flag on VMag (13)
119-121 F3.1 mag E_VMag ? Positive error in VMag
123-125 F3.1 mag e_VMag ? Negative error in VMag
127-130 I4 pc R2 ? Half-light radius (17)
132 A1 --- u_R2 [:] Uncertainty flag on R2
134-136 I3 pc E_R2 ? Positive error on R2
138-140 I3 pc e_R2 ? Negative error on R2
142-145 F4.1 mag/arcsec2 muEff ? The mean surface brightness within the
isophote defined by the half-light
radius (18)
147-153 A7 --- Ref3 Reference, in refs.dat file
155-199 A45 --- Com3 Comments about luminosity ans structure
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Note (11):
h = Measurement of structural parameters complicated by presence of
surrounding stream.
Note (12): In general, these have been corrected for foreground extinction
(1but not internal extinction). See Section 4 for further explanations.
Note (13): Flags on magnitudes, ellipticities, as follows:
: = Uncertainty flag;
b = surface brightness measured within central 2*2deg;
c = PA broadly aligned with the Galactic Plane;
d = Distance-independent absolute magnitude estimate.
e = surface brightness measured within projected radius of 0.8deg;
f = B magnitude, corresponding to "standard fit" in Table 1 of
Choi et al. (2002AJ....124..310C 2002AJ....124..310C);
g = B magnitude; see Table 1 of Geha et al. (2006, Cat. J/AJ/131/332).
i = PA corresponds to "outer component"; θinner=95°.
j = ellipticity corresponds to "outer component"; εinner=0.4.
k = magnitude converted from g, r;
l = B magnitude.
Note (14): Where possible, I cite directly measured values, although in many
cases (including in the original papers) this parameter is derived by
normalizing the measured profile to the apparent magnitude.
Note (15): Derived from Column Vmag of this table by subtraction of the
distance modulus given in Table 2 (Column (m-M)).
Note (16): For systems that show a change in this quantity as a function of
radius, a mean value has been estimated.
Note (17): Derived from Column Rad1 of this table assuming the distance
modulus given in Table 2 (Column (m-M)).
Note (18): Derived using values from columns Vmag, Rad1, and Ell. In cases
where no ellipticity is measured, I have assumed circular isophotes.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 29 A29 --- Name Galaxy name
31- 40 F10.5 10+6Msun Mass ? Mass of the galaxy in stellar masses (19)
42- 43 A2 --- l_sigma* [≤] Upper limit on sigma
45- 48 F4.1 km/s sigma* ? The observed velocity dispersion of the
stellar component σ* (20)
50 A1 --- f_sigma* [cj] Flag on sigma* (21)
52- 54 F3.1 km/s E_sigma* ? Positive error in sigma*
56- 58 F3.1 km/s e_sigma* ? Negative error in sigma*
60- 63 F4.1 km/s vsini* ? The observed rotational velocity of the
stellar component (22)
64 A1 --- f_vsini* [N] No rotational signature observed (22)
65- 68 F4.1 km/s e_vsini* ? Error in vsini*
70- 73 E4.2 10+6Msun M.HI ? Mass of HI in each galaxy (23)
75 A1 --- f_M.HI [:befk] Ambiguous HI detection (24)
77 A1 --- l_sigHI Upper limit on sigmaHI
79- 82 F4.1 km/s sigHI ? The observed velocity dispersion of the HI
component (25)
84 A1 --- u_sigHI [:dg] Uncertainty flag on sigHI (26)
86- 88 F3.1 km/s e_sigHI ? Error in sigHI
90- 91 A2 --- l_v.HI [≤] Upper limit on v.HI
93- 97 F5.1 km/s v.HI ? The observed rotational velocity of the HI
component (22)
99 A1 --- u_v.HI [:iN] Uncertainty flag on v.HI (26)
101-103 F3.1 km/s e_v.HI ? Error in v.HI
105-110 F6.2 10+6Msun Mdyn ? Dynamical mass within the observed
half-light radius Mdyn(≤rh)
(see Section 5 for further explanations)
112-126 A15 --- Ref4 Reference, in refs.dat file
128 A1 --- f_Ref4 [h] Flag on Ref (h = In the reference (234),
see their Note added in proof.
130-304 A175 --- Com4 Comments about masses and kinematics
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Note (19): Assuming a stellar mass-to-light ratio of 1.
Note (20): Generally based on multiple velocity measurements of individual
(giant) stars, otherwise commented on in Column Com (last Column of
this table). Note that a single value for the velocity dispersion is
often insufficient to describe the dynamics of the galaxy (e.g.,
multiple components and/or radial trends).
Note (21): Flag on sigma* as follows:
c = Upper limit (uncorrected for binaries) and with a possible member star
removed that otherwise boosts the dispersion to ∼5.5km/s;
j = Uncorrected for possible rotational signature.
Note (22): Where available, I quote the peak (observed) rotational velocity,
otherwise the maximum observed rotational velocity. In general, I try
to give the rotational velocity uncorrected for inclination or
asymmetric drift, although it is sometimes unclear in the original
papers whether these corrections have been applied. "N" ("N/A" in the
original paper) indicates that a rotational signature has been looked
for and none has been observed. Where only weak gradients in velocity
are detected and/or the rotational signature is ambiguous, I comment
on this in Column Com (last Column of the table). In most cases, it is
probably safest to interpret the absence of a rotational signature as
the absence of any rotation with a magnitude equal to or greater than
the magnitude of the velocity dispersion.
Note (23): Here, I have scaled the values cited in the relevant papers to
the distance given in Column Dist of Table 2. Where only an upper
limit from a non-detection is available and that upper limit is small
in comparison to the stellar mass, I give the HI mass as zero.
Note (24): Flag on Mass as follows:
b = See Putman et al. (2004ApJ...603L..77P 2004ApJ...603L..77P) for possible detection of gas
in the Sagittarius stream;
e = Ambiguous detection of two HI clouds offset from optical center that
could belong to the Magellanic Stream or Sculptor Group;
f = Ambiguous HI detection of cloud offset from optical center that could be
Galactic HI emission.
k = Calculated following Huchtmeier & Richter (1988A&A...203..237H 1988A&A...203..237H)
Note (25): Note that the HI velocity dispersion is affected by local
processes, such as heating due to star formation, and so caution is
urged in interpreting these numbers. Note also that many galaxies are
observed to contain multiple HI components.
Note (26): Flag on velocities as follows:
: = uncertainty flag;
d = sig.HI aries from 5 to 40km/s across face of SMC.
g = Estimated from mean velocities of seven prominent HI clumps.
i = v.HI shows an apparent north-south gradient of 20km/s
due to two distinct HI clumps.
N = a rotational signature has been looked for and none has been observed
(value is "N/A" in the published table)
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1- 29 A29 --- Name Galaxy name
31 A1 --- u_[Fe/H] [:] Uncertainty flag on [Fe/H]
33- 37 F5.2 [Sun] [Fe/H] ? Mean stellar metallicity (27)
39- 42 F4.2 [Sun] e_[Fe/H] ? Error in [Fe/H]
44- 63 A20 --- Meth Technique used to estimate stellar
metallicity (28)
65- 71 A7 --- Ref5 Reference, in refs.dat file
73-139 A67 --- Com5 Comment on metallicity estimations
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Note (27): Generally derived from observations of mostly evolved giants,
otherwise commented on in Column Com (last Column of this table).
See Section 6 for more details.
Note (28): Technique as follows:
HRS = Direct high-resolution spectroscopy. This is the most
well-accepted method of determining [Fe/H] for a given
star (the strengths of iron lines can be measured directly).
RGB color = Red giant branch color.
Da Costa & Armandroff (1990AJ....100..162D 1990AJ....100..162D) derive a
relation between the mean color of RGB stars in globular
clusters measured at MV=-3 and the mean stellar
metallicity of the cluster.
See Section 6 for more details.
Isochrones = See Section 6 for more details.
CMD fitting = The reader is referred to the many excellent papers on SFH
analysis using resolved stellar populations for more
details (e.g., Gallart et al., 2005ARA&A..43..387G 2005ARA&A..43..387G;
Tolstoy et al., 2009ARA&A..47..371T 2009ARA&A..47..371T, and references
therein). Here, age degeneracies will likely be much
reduced since age information is available from elsewhere
in the CMD (in particular the main-sequence turnoff region).
Co-added LRS (CaT) = Calcium II triplet equivalent widths (low resolution
spectroscopy). See Section 6 for more details.
LRS (CaT) = Calcium II triplet equivalent widths (low resolution
spectroscopy). See Section 6 for more details.
Co-added MRS (CaT) = Calcium II triplet equivalent widths (moderate resolution
spectroscopy). See Section 6 for more details.
MRS (CaT) = Calcium II triplet equivalent widths (moderate resolution
spectroscopy). See Section 6 for more details.
MRS = Spectral synthesis (moderate resolution spectroscopy).
See Section 6 for more details.
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Byte-by-byte Description of file: refs.dat
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Bytes Format Units Label Explanations
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1- 3 A3 --- Ref Reference code
5- 23 A19 --- BibCode Bibliographic code
25- 62 A38 --- Aut Author's name
64-320 A257 --- Com Comments
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History:
From electronic version of the journal
(End) Sylvain Guehenneux [CDS] 24-Jul-2013