Access to Astronomical Catalogues

← Click to display the menu
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
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:
FileName Lrecl Records Explanations
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 78 58 Data for UMi non-member stars table4v 38 74 Velocities for UMi non-member stars table5s 78 68 Data for Draco non-member stars table5v 38 92 Velocities for Draco non-member stars
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
Bytes Format Units Label Explanations
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)
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) Names of the form ##q# are from the original iris photometry of Schommer, Olszewski, & Kunkel. Some of these have Van Agt (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) 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) photometry and proper motions. The star names are those of Baade and Swope (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
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. Byte-by-byte Description of file: table2v table3v table4v table5v
Bytes Format Units Label Explanations
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)
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).
Nomenclature notes: The stars in tables 2 and 4 are: <Irwin UMi NNNNN>, <Olsz ANN> (letter A = N), <SOK NNNqN>, 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 Cudworth K.M. et al., 1986, AJ, 92, 766 =1986AJ.....92..766C Stetson P.B., 1979, AJ, 84, 1149 =1979AJ.....84.1149S van Agt S.L.Th.J., 1967, BAN, 19, 275 =1967BAN....19..275V
(End) Lee Brotzman [ADS], James Marcout [CDS] 26-Jan-1996
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

catalogue service

© UDS/CNRS

Contact