1999A&AS..135....5C


C.D.S. - SIMBAD4 rel 1.7 - 2020.02.17CET01:50:31

1999A&AS..135....5C - Astron. Astrophys., Suppl. Ser., 135, 5-28 (1999/February-2)

The distribution of nearby stars in phase space mapped by Hipparcos. III. Clustering and streaming among A-F type stars.

CHEREUL E., CREZE M. and BIENAYME O.

Abstract (from CDS):

This paper presents the detailed results obtained in the search of density-velocity inhomogeneities in a volume limited and absolute magnitude limited sample of A-F type dwarfs within 125 parsecs of the Sun. A 3-D wavelet analysis is used to extract inhomogeneities, both in the density and velocity distributions. Thus, a real picture of the phase space is produced. Not only are some clusters and streams detected, but the fraction of clumped stars can be measured. By estimating individual stellar ages one can relate the streams and clusters to the state of the interstellar medium (ISM) at star formation time and provide a quantitative view of cluster evaporation and stream mixing. Having established this picture without assumption we come back to previously known observational facts regarding clusters and associations, moving groups or so-called superclusters. In the 3-D position space, well known open clusters (Hyades, Coma Berenices and Ursa Major), associations (parts of the Scorpio-Centaurus association) as well as the Hyades evaporation track are retrieved. Three new probably loose clusters are identified (Bootes, Pegasus 1 and 2). The sample is relatively well mixed in the position space since less than 7 per cent of the stars belong to structures with coherent kinematics, most likely gravitationally bound. The wavelet analysis exhibits strong velocity structuring at typical scales of velocity dispersion <σ>stream∼6.3, 3.8 and 2.4km/s. The majority of large scale velocity structures (<σ>stream∼6.3km/s) are Eggen's superclusters (Pleiades SCl, Hyades SCl and Sirius SCl) with the whole Centaurus association. A new supercluster-like structure is found with a mean velocity between the Sun and Sirius SCl velocities. These structures are all characterized by a large age range which reflects the overall sample age distribution. Moreover, a few old streams of ∼2Gyr are also extracted at this scale with high U components. We show that all these large velocity dispersion structures represent 63% of the sample. This percentage drops to 46% if we remove the velocity background created by a smooth velocity ellipsoid in each structure. Smaller scales (<σ>stream∼3.8 and 2.4km/s) reveal that superclusters are always substructured by 2 or more streams which generally exhibit a coherent age distribution. At these scales, background stars are negligible and percentages of stars in streams are 38% and 18% respectively.

Abstract Copyright:

Journal keyword(s): methods: data analysis, Galaxy: solar neighbourhood - galaxies open clusters and associations - galaxies: kinematics and dynamics

Nomenclature: Table 1: [CCB99] NN (Nos 1-17), [CCB99] Pegasus N (Nos 1-2).

Simbad objects: 28

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Number of rows : 28

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2020
#notes
1 Cl Melotte 22 OpC 03 47 00 +24 07.0           ~ 2935 0
2 Cl Melotte 25 OpC 04 26 54.00 +15 52 00.0           ~ 2613 0
3 Cl Melotte 111 OpC 12 25 06.00 +26 06 00.0           ~ 398 0
4 NAME Ursa Major Moving Group MGr 12 32 +57.0           ~ 373 2
5 NAME BOO SUPERCL SCG 14 01.5 +25 09           ~ 22 1
6 [CCB99] 1 Cl* 14 29 04 +55 23.5           ~ 3 0
7 NAME ASSOC II SCO As* 16 15 -24.2           ~ 1091 1
8 [CCB99] 5 Cl* ~ ~           ~ 1 0
9 [CCB99] 6 Cl* ~ ~           ~ 1 0
10 [CCB99] 7 Cl* ~ ~           ~ 1 0
11 [CCB99] 8 Cl* ~ ~           ~ 1 0
12 [CCB99] 9 Cl* ~ ~           ~ 1 0
13 [CCB99] 10 Cl* ~ ~           ~ 1 0
14 NAME LYN-UMA SUPERCL reg ~ ~           ~ 4 0
15 [CCB99] 12 Cl* ~ ~           ~ 1 0
16 [CCB99] 13 Cl* ~ ~           ~ 1 0
17 [CCB99] 14 Cl* ~ ~           ~ 1 0
18 [CCB99] 15 Cl* ~ ~           ~ 1 1
19 [CCB99] 16 Cl* ~ ~           ~ 1 0
20 [CCB99] 17 Cl* ~ ~           ~ 1 0
21 NAME Hyades Moving Group MGr ~ ~           ~ 232 1
22 [CCB99] 11 Cl* ~ ~           ~ 1 0
23 NAME PLEIADES SUPERCL Cl* ~ ~           ~ 17 0
24 [CCB99] Pegasus 1 Cl* ~ ~           ~ 1 0
25 [CCB99] Pegasus 2 Cl* ~ ~           ~ 1 0
26 [CCB99] 2 Cl* ~ ~           ~ 3 0
27 [CCB99] 3 Cl* ~ ~           ~ 3 0
28 [CCB99] 4 Cl* ~ ~           ~ 1 0

    Equat.    Gal    SGal    Ecl

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2020.02.17-01:50:31

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