Open Cluster Stars for RAVE Observations in the Galactic Plane Ralf Scholz 1, Nina Kharchenko 1,2,...

Open Cluster Stars for RAVE Open Cluster Stars for RAVE Observations in the Galactic PlaneObservations in the Galactic Plane

Ralf Scholz1, Nina Kharchenko1,2, Anatoly Piskunov1,3, Elena Schilbach4 & Siegfried Röser4

1 AIP2 MAO, Kiev3 INASAN, Moscow4 ARI Heidelberg

Motivation: Out of ~1700 open clusters (OCL) there are only 326 (19%) with

available radial velocity (RV) measurements:229 OCL data taken from Dias et al. 2004 (http://www.astro.iag.usp.br/~wilton/)

plus first RV determinations of 97 further OCL (Kharchenko et al. 2004c, in prep.)

RV data quality for OCL very heterogeneous:~70% of available OCL RVs are determined from <4 stars.

Cluster membership of corresponding stars not well defined.

For ~30 OCL, the mean cluster RV errors are 10-30 km/s.

Uniform OCL memberships and reliable OCL RVs are needed forimproving membership statistics and physical parameter determination of OCL,determining accurate space velocities of OCL of various ages,investigating OCL vs. Galactic disk (spiral structure) kinematics.

OCL stars with accurate RV measurements can serve as RV standards, because a number of physical properties of the cluster are known.

Our previous work on open clusters: Proper motion and photometric studies of open clusters and associations

(Pleiades, NGC6611, IC348, PerOB2) (e.g. Belikov et al. 1999a,b, 2000; Scholz et al. 1999; Belikov et al. 2002a,b)

ASCC-2.5 = All-Sky Compiled Catalogue of 2.5 million stars (Kharchenko 2001, Kinematics & Physics of Celestial Bodies 17, 409 (CDS: Cat. I/280A)

Astrophysical supplements to the ASCC-2.5:

(0) Structural and kinematical parameters of 401 open clusters (Kharchenko, Pakulyak & Piskunov 2003, Astron.Reports 47, 263)

(1) CRVAD = Catalogue of Radial Velocities with accurate Astrometric Data (Kharchenko, Piskunov & Scholz 2004a, Astron.Nachr. 325, 439) - including ASRV sub-sample of proposed Astrometric Standards with Radial Velocities

(2) Cluster memberships in 520 open cluster areas (Kharchenko, Piskunov, Röser, Schilbach & Scholz 2004b, Astron.Nachr., submitted)

(3) Physical parameters of 520 open clusters (Kharchenko et al. 2004c, in prep)

All-Sky Compiled Catalogue of 2.5 Million Stars (ASCC-2.5)

Hipparcos family:Tycho 1/2, ACTRC, TRC, Mult.system annex

PPM, CMC11

Systems: Hipparcos coords and pm Johnson V,B-V

ASCC-2.5

Accurate positions and proper motions B-V,V for 2,501,304 stars + parallaxes, Sp, ids for many of them, + variability and multiplicity flags

X-Id. of ASCC-2.5 with GCRV (Barbier-Brossat & Figon 2000)

Basic constraint : Spatial proximityIdentification radii (ri) 1 arcmin 95 % objects 3 3 % 10 2 %Other constraints: Hipparcos, DM, HD, CCDM designationsDoubtful cases (checked manually): 17%

Additional constraints (if several objects found within ri): apparent magnitude color B-V Spectral Class

Results: ~93% of the 36145 GCRV entries could be identified

ASCC-2.5 GCRV Multiples unresolved in GCRV 34553 33509 1044

CRVAD completeness Vcompl ~ 5 mag

ASCC-2,5

CRVAD

ASRV ~4000 possible

standards

CRVAD: distribution over the sky

Galactic Equatorial

Astrometric Standards with Radial Velocities (ASRV sample)

3967 stars from CVRAD with:

no var/mult flags;RV < 2 km/sNRV > 3coo < 0.04 masPM < 4 mas/yrB,V < 0.05 magB-V < 0.07 mag

But only 446 stars with V>9 (RAVE)

Equatorial coordinates

ASCC-2.5ASCC-2.5(I/280A)

2,500,000 starspositions, PM, B,VSp

CRVADCRVAD

RV of 34,500 ASCC-2.5 stars

Galactic Open Cluster Lists

Lynga (1987) - 1150 Dias et al. (2002) - 1630 Ruprecht et al. (1981) - 87ass

Catalogue of166,000 stars in 520 sky areas supplied with membership probabilities Catalogue of data on 520 clusters (sizes, distances, ages, kinematics)Atlas of cluster diagrams (map,CMD,VPD,density profile for 520 clusters)

&&

&&

NGP

SGP

0° 360°

Member selection scheme

1-member: P >61%2-member: P =14-61%3-member: P >=1-14%

Coordinateselection

Photometricselection

Proper motionselection

1-member list changed ?

Final member list

NoNo

YesYes

Proper motion membership

Vector Point Diagram

Photometric membership

To filter out co-moving field starsinfluencing PM-selection

Used: sequences of Unresolved BinariesPost-MS isochronesPre-MS isochrones

Stars 1,3 P=100 %Stars 2,4,5 P>0 %Stars 6,7 P=0 %

Post-MS

Pre-MS

q=0.8

q=1

bars

Blanco-1: an example of the member-selection procedure

Quality check using SSS I-band finding charts and magnitudes

too bright (I<9)

neighbouring star with I<16 within 8 arcsec

bright star within 10 arcsec

Out of 4592 candidates:Rejected - 1871 stars OK - 2721 stars

target I>9

neighbours with I>16

next bright star outside of 10 arcsec

24 arcsec

RAVE targets in Galactic plane: open cluster stars/standards 1

RAVE targets in Galactic plane: open cluster stars/standards 2

RAVE targets in Galactic plane: open cluster stars/standards 3

RAVE targets in Galactic plane: open cluster stars/standards 4

01

020203

06

05

07

04

0809

10

11

Proposed RAVE field 01 (high priority)

Many stars, but fibre allocation problem due to clustering (observe twice?)

Proposed RAVE field 02 (high priority)

Better distribution with respect to fibre allocation

Small overlap with field 03

Proposed RAVE field 04 (high priority)

Good distribution for fibre allocation

Overlap with field 05

Proposed RAVE field 05 (high priority)

Many stars incl. 5 standards

Good distribution

Overlap with field 04

Proposed RAVE field 07 (high priority)

Field centre shifted in order to get maximum number of standards (8)

Total number of targets: 92

Proposed RAVE field 08 (lower priority)

8 clusters, but too few stars in field

Proposed RAVE field 11 (lower priority)

Only 75 cluster stars but good distribution and 4 standards

Additional stars could be selectedfrom UCAC2

Overlap with fields 02 and 03

Number of selected RAVE target stars per open cluster

Distribution of ages and distances of selected RAVE target OCL

Magnitudes of OCL stars selected from ASCC-2.5Only <10 of these stars have previous RV measurements.

Even fainter cluster members could be added from the study of UCAC2 and/or SSS proper motions,

in order to fill the RAVE fields with an optimum number of targets (~150/field).

Proper motions versus stellar magnitudes in selected areas

ASCC-2.5

UCAC2

USNO-B1.0 & SSS (black)

Summary of proposed RAVE observations:

7 high priority fields with 761 cluster stars + 20 RV standards

Only fields with >100 targets were considered to make effective use of RAVE observations

Field 01 proposed to be observed twice (~200 targets)

Total of 85 OCL = representative sub-sample with respect to age and distance distribution- some OCL and ass. are represented by >20 stars, RV can be used in membership study

- but many OCL are currently represented by <3 stars selected as RAVE targets

Possible extension of target lists:- special efforts to increase minimum number of stars per OCL to >2, e.g. add fainter cluster

stars (V>12) from UCAC2/SSS proper motion study- get more (non OCL) RV standards with less stringent criteria