J/AJ/110/2131 M/L for Draco and UMi. I. (Armandroff+ 1995)
The mass-to-light ratios of the Draco and Ursa Minor dwarf spheroidal galaxies.
I. Radial velocities from multifiber spectroscopy.
Armandroff T.E., Olszewski E.W., Pryor C.
<Astron. J. 110, 2131 (1995)>
=1995AJ....110.2131A 1995AJ....110.2131A
ADC_Keywords: Radial velocities ; Clusters, galaxy
Abstract:
We have measured 206 radial velocities for 94 probable members in the
Ursa Minor dwarf spheroidal galaxy and 167 velocities for 91 probable
members in the Draco dwarf spheroidal galaxy. These velocities were
obtained using the KPNO 4m telescope with the Hydra multifiber
positioner and bench spectrograph in 1992, 1993, and 1994. Both
simulations and repeated measurements show that the median uncertainty
in these velocities is 4.0km/s.
Our velocities are compared with the other major datasets for Draco
and Ursa Minor. Aside from a small zero-point difference, there is
excellent agreement between the Hydra velocities and the Olszewski et
al. MMT echelle velocities. Comparison with the Hargreaves et al. Ursa
Minor velocities reveals inconsistencies which we ascribe to
underestimated errors in the Hargreaves et al. data. After correcting
for zero-point differences, we combine the three major sets of
velocities. Our spectra recovered all of the known Carbon (C) stars in
Draco and Ursa Minor and revealed one new C star in Draco and two in
Ursa Minor. In addition, one star whose velocity is consistent with
membership in Ursa Minor has a deep and wide HBeta absorption line in
its spectrum. An initial discussion of the kinematics of the two
galaxies is presented. The systemic velocities of Draco and Ursa Minor
are -293.3±1.0 and -274±1.0km/s, respectively. Ursa Minor shows
apparent rotation about a position angle of 75deg with an amplitude of
about 3km/s; the morphological major axis is 53±5deg. No such
rotation is found in Draco. We find a velocity dispersion of
10.4±0.9km/s for Ursa Minor including all stars and 8.8±0.8km/s
excluding the star with the most extreme velocity. In Draco we find
10.7±0.9km/s including all stars and 8.5±0.7km/s excluding the
three stars with the most extreme velocities. These dispersions are
consistent with the dispersions measured in the other two studies and
confirm that Draco and Ursa Minor have the largest mass-to-light
ratios of any of the dwarf spheroidals.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2s 78 94 Data for UMi stars
table2v 38 312 Velocities for UMi stars
table3s 78 91 Data for Draco stars
table3v 38 236 Velocities for Draco stars
table4s 69 58 Data for UMi non-member stars
table4v 35 74 Velocities for UMi non-member stars
table5s 69 68 Data for Draco non-member stars
table5v 35 92 Velocities for Draco non-member stars
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See also:
J/MNRAS/330/792 : Radial velocity in Draco (Kleyna+, 2002)
J/AJ/121/841 : Draco dwarf spheroidal galaxy RV photometry (Piatek+, 2001)
J/AJ/123/2511 : Draco dwarf spheroidal galaxy RV photometry (Piatek+, 2002)
Byte-by-byte Description of file: table2s table3s table4s table5s
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Primary star name (1)
9- 11 I3 --- Num Number of velocities following header
12- 14 I3 h RAh Right ascension, 1950
15- 17 I3 min RAm Right ascension, 1950
18- 23 F6.2 s RAs Right ascension, 1950
24 A1 --- DE- Declination sign, always blank
25- 26 I2 deg DEd Declination, 1950
27- 29 I3 arcmin DEm Declination, 1950
30- 34 F5.1 arcsec DEs Declination, 1950
35- 42 F8.2 km/s <Vel> Average radial velocity
43- 47 F5.2 km/s e_<Vel> Uncertainty in <Vel>
48- 54 F7.1 --- Chi2 []? Chi-square of scatter about <Vel>
55- 63 E9.2 --- Prob []? Probability of larger Chi2 (2)
65- 76 A12 --- Other Other names for the star
78 A1 --- Note Note (3)
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Note (1):
In tables 2 and 4:
Numbers without prefix are Irwin UMi.
Names starting by "N" are from Olsz, names with "q" are SOK
COS### names are from the proper motion survey of Cudworth et al.
(1986AJ.....92..766C 1986AJ.....92..766C)
Names of the form ##q# are from the original iris photometry of
Schommer, Olszewski, & Kunkel. Some of these have Van Agt
(1967BAN....19..275V 1967BAN....19..275V) numbers embedded in them.
Although the ##q# designations are unpublished, they have been used in
some previous studies. Most are cross-referenced in Cudworth et al.
(1986AJ.....92..766C 1986AJ.....92..766C) and we give them only if there is no COS number.
JI## names are from the work of H94. H94 also observed stars noted by
Olszewski to be velocity members and stars from the COS list. Their
designations seem to be mixed and matched; they called these stars
CUD### and EDO###. We provide cross references to these names.
Stars labelled N## are from an unpublished study by Olszewski. We
suppress these names unless MMT velocities had been obtained using
those names or unless the star was in our master list because of that
unpublished study and because of the existence of MX spectra.
Finally, almost every star has a 5-digit number. This number can be
considered a running number; it is from a large body of APM
photometry of the Ursa Minor region provided to us by M. Irwin.
Although this photometry is unpublished, that is how we referred
to the stars throughout the reduction.
In table 3 and 5:
Three-digit numbers and single letters are from Stetson
(1979AJ.....84.1149S 1979AJ.....84.1149S) photometry and proper motions. The star
names are those of Baade and Swope (1961AJ.....66..300B 1961AJ.....66..300B), where
a finding chart can be found.
Four digit numbers are from the outer annulus of Stetson
(private communication). He was able to derive good photometry,
but could not derive proper motions.
Roman numerals followed by a number are from the photographic
photometry of McClure (private communication).
Five digit numbers can be considered a running number; they are
from a large body of APM photometry of the Draco region provided
to us by M. Irwin. Although this photometry is unpublished,
that is how we referred to the stars throughout the reduction.
We remind readers that some mistakes may have crept into the
cross-identifications; the coordinates are the ultimate way
to settle any dispute.
Note (2): The probability of obtaining a chi-square as large or larger
than is observed if the star has a constant radial velocity.
Note (3): 1. C star
2. Identified as a giant candidate by MX spectroscopy
3. Observed by H94, but with low S/N.
4. H-beta in emission
5. Listed as EDOH and EDOE in Table 1 of H94 and as EDONH and
EDONE in their Table 3
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Individual note on COS390 (table3s):
H94 claimed that the star COS390 (called CUD390 in H94) was a potential
member of UMi based on a low-S/N spectrum. We report here a precise
velocity showing that this star is not a member.
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Byte-by-byte Description of file: table2v table3v table4v table5v
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Bytes Format Units Label Explanations
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1- 8 A8 --- Name Primary star name
9- 18 D10.2 d JD Julian date of the velocity
19- 26 F8.1 km/s Vel Measured radial velocity
27- 30 F4.1 km/s e_Vel Uncertainty in Vel
31- 36 F6.2 --- R(Vel) R value for the velocity (1)
38 A1 --- Src [ MH] Source of the velocity (2)
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Note (1): R is the ratio between the height of the peak of the
correlation function and the rms noise in the correlation function.
Note (2): The source of the velocity, where a blank indicates a velocity
measured with Hydra and reported in this paper, an M indicates
an MMT echelle velocity from Olszewski et al. (1995, AJ, 110, 2120),
and an H indicates a velocity from Hargreaves et al.
(1994, MNRAS, 271, 693).
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Nomenclature notes:
The stars in tables 2 and 4 are:
<Irwin UMi NNNNN>, <Olsz ANN> (letter A = N), ,
The stars in tables 3 and 5 are:
<Irwin Dra NNNNN>, <McClure R-NN> and <McClure CN> (Nos C1-C4),
<Stetson NNNN>
History:
The AAS CD-ROM original tables contained a mixture of data related
to stars and velocity measurements; these were divided in two sets
of files. In the course of this modification, a few errors
were detected and corrected in the e_<Vel> column:
table2s : N33
table5s: stars 14562 and 18411 e_<Vel> misaligned
References:
Baade W. and Swope H., 1961, AJ, 66, 300 =1961AJ.....66..300B 1961AJ.....66..300B
Cudworth K.M. et al., 1986, AJ, 92, 766 =1986AJ.....92..766C 1986AJ.....92..766C
Stetson P.B., 1979, AJ, 84, 1149 =1979AJ.....84.1149S 1979AJ.....84.1149S
van Agt S.L.Th.J., 1967, BAN, 19, 275 =1967BAN....19..275V 1967BAN....19..275V
(End) Lee Brotzman [ADS], James Marcout [CDS] 26-Jan-1996