Browse
this table...

MWSC - Milky Way Star Clusters Catalog

HEASARC
Archive

Overview

Although they are the main constituents of the Galactic disk population, for half of the open clusters in the Milky Way reported in the literature nothing is known except the raw position and an approximate size. The main goal of this study is to determine a full set of uniform spatial, structural, kinematic, and astrophysical parameters for as many known open clusters as possible. On the basis of stellar data from PPMXL and 2MASS, the authors used a dedicated data-processing pipeline to determine kinematic and photometric membership probabilities for stars in a cluster region. For an input list of 3,784 targets from the literature, they confirm that 3,006 are real objects, the vast majority of them are open clusters, but associations and globular clusters are also present. For each confirmed object, the authors determined the exact position of the cluster center, the apparent size, proper motion, distance, color excess, and age. For about 1,500 clusters, these basic astrophysical parameters have been determined for the first time. For the bulk of the clusters the authors also derived the tidal radii. In addition, they estimated average radial velocities for more than 30% of the confirmed clusters. The present sample (called MWSC) reaches both the central parts of the Milky Way and its outer regions. It is almost complete up to 1.8 kpc from the Sun and also covers the neighboring spiral arms. However, for a small subset of the oldest open clusters (ages more than ~ 1 Gyr), the authors found some evidence of incompleteness within about 1 kpc from the Sun.

This table contains the list of 3,006 Milky Way stellar clusters (MWSC) found in the 2MAst (2MASS with Astrometry) catalog presented in Paper II of this series (these clusters have source numbers below 4000), together with an additional 139 new open clusters (these clusters have source numbers between 5000 and 6000) found by the authors at high Galactic latitudes (|b_II_| > 18.5 degrees) which were presented in Paper III of the series . The target list in Paper II from which the 3,006 open clusters was contained was compiled on the basis of present-day lists of open, globular and candidate clusters. The list of new high-latitude open clusters in Paper III was obtained from a target list of 714 density enhancements found using the 2MASS Catalog. For confirmed clusters, the authors determined a homogeneous set of astrophysical parameters such as membership, angular radii of the main morphological parts, mean cluster proper motions, distances, reddenings, ages, tidal parameters, and sometimes radial velocities.


Catalog Bibcodes

2012A&A...543A.156K
2013A&A...558A..53K
2014A&A...568A..51S

References

Global survey of star clusters in the Milky Way.
I.  The Pipeline and fundamental parameters in the second quadrant.
    Kharchenko N.V., Piskunov A.E., Schilbach E., Roeser S., Scholz R.-D.
    <Astron. Astrophys. 543, A156 (2012)>
    =2012A&A...543A.156K        (SIMBAD/NED BibCode)

Global survey of star clusters in the Milky Way.
II. The catalogue of basic parameters.
    Kharchenko N.V., Piskunov A.E., Roeser S., Schilbach E., Scholz R.-D.
    <Astron. Astrophys. 558, A53 (2013)>
    =2013A&A...558A..53K        (SIMBAD/NED BibCode)

Global survey of star clusters in the Milky Way.
III. 139 new open clusters at high Galactic latitudes.
     Schmeja S., Kharchenko N.V., Piskunov A.E., Roeser S., Schilbach E.,
     Froebrich D., Scholz R.-D.
    <Astron. Astrophys. 568, A51 (2014)>
    =2014A&A...568A..51S        (SIMBAD/NED BibCode)

Provenance

This table was created by the HEASARC in February 2014 based on the list of open clusters given in CDS Catalog J/A+A/558/A53 files catalog.dat and notes.dat. It was updated in September 2014 with 139 additional star clusters from CDS Catalog J/A+A/568/A51 files catalog.dat and notes.dat. Note that this table does not include the information on candidates which turned out not to be open clusters which was also contained in these catalogs.

Data Products

The atlas files (one for each cluster) in the MWSC are stored at the CDS. Each file is in a gzipped encapsulated PostScript format. The atlas file names include the MWSC sequential number and a name of the cluster, e.g. "0001_Berkeley_58_map.eps.gz" for the 1st page with a map as a basic panel, and "0001_Berkeley_58_cmd.eps.gz" for the 2nd page with the color-magnitude diagrams (CMDs) as the basic panels. The stars files (one for each cluster) in the MWSC are stored at the CDS. Each file is a bzip2 compressed archive file containing the list of cluster member stars in the form specified in http://cdsarc.u-strasbg.fr/ftp/cats/J_A+A/558/A53/ReadMe. The stars file names include the MWSC sequential number and a name of the cluster, preceded by a prefix "2m_" e.g. "2m_0001_Berkeley_58.dat" for the cluster named Berkeley 58.

The CDS describes the atlas files as follows:

    For each cluster we prepared two EPS-pages with diagrams:
     Page 1 contains the cluster map as the basic panel
     (file MWSC_Name_map.eps.gz),
     Page 2 contains the Ks,(J-Ks) and Ks,(J-H) CMDs as basic panels
     (file MWSC_Name_cmd.eps.gz).

    The legend on each page gives the cluster name, MWSC number, (COCD
    number); equatorial RAJ2000, DecJ2000, and galactic l, b coordinates
    of the cluster center; apparent cluster sizes r0, r1, r2, [number of
    1sigma-members within the corresponding radius]; weighted average
    components PM_(X,Y) of proper motion with their rms errors, [number of
    stars used to compute the average]; the average radial velocity, RV
    with their rms error, [the number of stars used to compute the
    average]; distance to the cluster, d, distance modulus, (Ks-M_Ks);
    NIR color-excesses, E(J-H), E(J-Ks), interstellar extinction, A(Ks);
    cluster age, its rms error, [the number of stars used to compute the
    average age, or it is -1 if a manual isochrone fit was applied].
    Additionally we show in the 2nd pages: an empirical correction
    Delta_H for a better isochrone fit in the K_s,(J-H) diagram.

    Symbols and their colors have the same meaning in all plots. Stars
    are shown as colored circles or dots. Cyan symbols mark stars outside
    the cluster radius r2, green symbols are stars within r2. The most
    probable kinematic and photometric members (1sigma-members) are
    indicated in black, red, or blue. Black is for members located within
    r1 (the visible radius of the central part), red for members between
    r1 and r2, and blue for stars outside r2 (the probabilities are
    formal). Cyan bars show the uncertainty for 1sigma-members.

Description of files MWSC_Name_map.eps.gz (Page 1):

   Page 1 contains five diagrams with spatial information.
   The right panel is a map of the cluster neighborhood (MAP),
   the left panels show (from top to bottom) relations depending on the
   distance from the cluster center, r, for:
   -magnitude Ks (Ks vs. r),
   -proper motions (PM vs. r),
   -density profile diagram (DPD).

   MAP:
    Stars are displayed as small circles.
    The circle size corresponds to the stellar magnitude ranged in six
    Ks mag intervals:
    < 6.0, 6.0 - 8.0, 8.0 - 10.0, 10.0 - 12.0, 12.0 - 14.0, > 14.0.
    Blue cross : cluster center selected in this study;
    Blue plus : cluster center from the literature;
    Magenta pluses : centers of other clusters (from target list) visible
                      (if any) in the map;
    Dotted blue large circle : cluster core border (r0);
    Solid blue large circle : inner cluster border (r1);
    Dashed blue large circle : cluster corona border (r2).

   The left panels:
   Blue vertical dotted, solid, dashed lines  mark r0, r1, r2, respectively.

   PM vs. r: Magenta  horizontal lines correspond to the average proper
   motion of the cluster determined in this paper;

   DPD: Density profiles (Log of Number of stars per 1 sq.deg) are shown for
   all stars (green line), 3sigma-members (blue line), 2sigma-members (magenta
   line) and 1sigma-members (black line).

Description of files MWSC_Name_cmd.eps.gz (Page 2):

   Page 2 contains diagrams with kinematic and photometric information.
   The three left panels are:
    -two PM_(X,Y) vs. Ks relations, i.e. PM-magnitude equation diagrams (MEDs);
    -the vector point diagram of proper motions (VPD).
   The two upper right panels are:
    -relations (Ks,(J-H) and Ks,(J-Ks), i.e. the color-magnitude
      diagrams (CMDs).
   The bottom right panels:
    -color-color diagrams (CCDs);
    -reddening-independent parameter Q-color diagrams (QCDs).

   The CCDs and QCDs are separated into two sub-panels (as well as CMDs and
   MEDs are separated into two parts via a broken line). The division is
   made with respect to the Ks_mc magnitude: in the bottom sub-panels we
   place data for Ks > Ks_mc, in the upper ones - for Ks < Ks_mc, where
   Ks_mc is Ks-magnitude at the bluest color (J-Ks) of the isochrone
   closest to the determined cluster age.

  CMDs:
   Magenta curve: the apparent isochrone closest to the determined cluster age;
   Solid blue lines: left and right borders of a domain of 100% photometric
                      cluster members;
   Solid red lines: ZAMS and TAMS (shown only in the Ks,(J-Ks) diagram), the
                     borders of the evolved Main Sequence stars;
   Magenta dashed line: corresponds to the Ks_mc;
   Thick yellow circles: stars selected for age determination;
   Black arrows: increasing interstellar extinction vectors.

  MED:
   Magenta solid lines correspond to the average proper motion of the
    cluster; the magenta dashed line corresponds to the Ks_mc.

  CCD and QCD:
   The Magenta curve corresponds to the apparent isochrone (observed magnitudes
   and colors); the cyan curve corresponds to the intrinsic isochrone.

Description of Paper II Methodology

An all-sky target list of 3,784 entries with initial cluster parameters was compiled from sources available in the literature. As the primary source, the authors used the data from the Catalogue of Open Cluster Data (COCD, Kharchenko et al. 2005, A&A, 438, 1163; 2005, A&A, 440, 403, HEASARC Catalogs COCD and COCDEXT1, respectively). For further optical clusters the data were taken from the Dias et al. (2002, CDS Cat. B/ocl, HEASARC Catalog OPENCLUST) list (Version 3.1, 24/nov/2010). Known associations were retrieved from Melnik & Dambis (2009, MNRAS, 400, 518). For clusters detected in the NIR, the information came from Bica et al. (2003, A&A, 404, 223), Dutra et al. (2003, A&A, 400, 533), Froebrich et al. (2007, MNRAS, 374, 399). Globular clusters were selected from the catalog by Harris (1996, edition 2010, 2010arXiv1012.3224, HEASARC Catalog GLOBCLUST). Additionally, the authors incorporated supplementary data on embedded clusters from Bica et al. (2003, A&A, 397, 177), Lada & Lada (2003, ARA&A, 41, 57) and on stars in associations from Humphreys (1978, CDS Cat. V/44).

The basic stellar data were taken from the all-sky catalog 2MAst (2Mass with Astrometry), that was extracted from the all-sky catalogs PPMXL (Roeser et al. 2010, CDS Cat. I/317) and 2MASS (Cutri et al. 2003, CDS Cat. II/246). Additionally, the authors incorporated data on radial velocities from Kharchenko et al. (2007, CDS Cat. III/254) and spectral types from ASCC-2.5 (Kharchenko & Roeser 2009, CDS Cat. I/280).

Around each object from their target list, the authors defined a circular area with a radius of ra = r2 + radd where r2 is the cluster radius, and radd = 0.3 degrees. In these areas, they selected in 2MAst only those stars with flags Rflg (the second triple of the flags in 2MASS) set to 1, 2, or 3 in each band, i.e. the stars with the best quality detections in photometric and astrometric data.

Of the 3,784 targets in their object list, the authors confirmed 3,006 clusters and/or associations. These 3,006 sky areas contain about 63.5 million 2MAst stars with best quality detections in photometric and astrometric data. The authors selected about 0.14 million most probable members located in the central cluster regions and determined - with a homogeneous method/pipeline - the angular sizes of the main morphological parts, heliocentric distances, color-excesses, mean proper motions, ages, tidal parameters, sometimes radial velocities and metallicities.


Description of Paper III Methodology

The authors looked for stellar density enhancements using a star count algorithm in the 2MASS point source catalog (CDS Cat. II/246). In total, they discovered 714 density enhancements (regarded as cluster candidates). The candidates were cross-identified with known objects. Unidentified objects were passed through the standard MWSC pipeline for verification, cluster membership construction and structure, kinematic and astrophysical parameter determination. The basic stellar data were taken from the all-sky catalogue 2MAst (2MASS with Astrometry), that was extracted from the all-sky catalogs PPMXL (Roeser et al. 2010, CDS Cat. I/317) and 2MASS (Cutri et al. 2003, CDS Cat. II/246). The authors found that 359 candidates coincide with known objects, while the other 355 candidates were not identified, and 139 of them they classified as real star clusters and determined their basic cluster parameters.

Around each confirmed object from their target list they defined a circular area with a radius of ra = r2 + radd where r2 is initial estimate of cluster radius, and radd = 0.3 degrees. In these areas they selected in 2MAst only those stars with flags Rflg (the 2nd triple of the flags in 2MASS) set to 1, 2, or 3 in each band, i.e. the stars with the best quality detections in photometric and astrometric data.

The 139 sky areas with confirmed clusters contain about 0.52 million 2MAst stars with best quality detections in photometric and astrometric data. The authors selected the most probable members and determined - with a homogeneous method/pipeline - the angular sizes of the main morphological parts, their heliocentric distances, color excesses, mean proper motions, ages and tidal parameters.

Paper III extends the MWSC project's initial Paper II input list of 3784 targets by 714 new candidates. The authors have adopted for them an MWSC numbering starting with source number 5001. Since the search was performed for Northern and Southern hemispheres separately, the candidate numbering is discontinuous: the numbers 5001 <= MWSC < 5499 are assigned for b > +18.5 degrees, and 5500 <= MWSC < 5999 designate candidates for b < -18.5 degrees.


Parameters

Source_Number
A running identification number for each cluster or cluster candidate in order of increasing J2000.0 Right Ascension, from 1 to 3,784 for objects from Paper II, and from 5004 to 5963 for objects from Paper III. Some of the source numbers were assigned to candidates which turned out not to be clusters and are thus not contained in this present table, which lists only the 3,145 confirmed clusters.

Name
The NGC, IC or other common designation for the cluster. The new clusters from paper III have been given names using the 'MWSC' prefix and their source number, e.g., 'MWSC 5004'.

Broad_Type
This flag parameter indicates the object type as follows:

   (blank) = open cluster
         a = association
         g = globular cluster
         m = moving group
         n = nebulosity/presence of nebulosity
         r = remnant cluster
         s = asterism
  

Cluster_Status
This flag parameter is set only for 739 objects which are not open clusters (i.e., broad_type != ' '): 'c' means candidate and 'o' means object, according to the CDS documentation.

RA
The Right Ascension of the adopted cluster center in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.0001 hours (0.36 seconds of time) in the original table.

Dec
The Declination of the adopted cluster center in the selected equinox. This was given in J2000.0 coordinates to a precision of 0.001 degrees (3.6 arcseconds) in the original table.

LII
The Galactic Longitude of the adopted cluster center.

BII
The Galactic Latitude of the adopted cluster center.

Core_Radius
The angular radius of the core of the cluster, r0, in degrees. The authors assumed a centrally symmetric distribution of the cluster members and introduced three empirical structural parameters r0 < r1 < r2 describing the shape of the radial density profile (RDP), which were fitted by eye. The visible core radius r0 corresponds to the distance from the cluster center where the slope of the RDP becomes flatter, the visible radius of the central part r1 is the distance where the decrease of the stellar density stops abruptly, and the actual (total) visible radius of a cluster r2 is defined as the distance from the cluster center where the surface density of stars becomes equal to the average density of the surrounding field. r0 is a new feature considered here, while in their previous work with the COCD the authors determined only r1 and r2. Based on visual inspection of the corresponding data, r0, r1, and r2 give empirical descriptions of cluster sizes, without a direct association to e.g., King's parameters rc and rt (see Section. 3.4.4. of Paper I). However, the authors found that the relations r0 < rc < r1 and rt > r2 are generally obeyed.

Central_Radius
The angular radius of the central part of the cluster, r1, in degrees. (See the core_radius description above for more details).

Cluster_Radius
The angular radius of the cluster, r2, in degrees. (See the core_radius description above for more details).

PM_RA
The average cluster proper motion in the Right Ascension direction, muRA * cos(Dec), in milliarcseconds per year (mas/yr).

PM_Dec
The average cluster proper motion in the Declination direction, muDec, in milliarcseconds per year (mas/yr).

PM_Tot_Error
The standard error in the average cluster total proper motion, mu, in milliarcseconds per year (mas/yr).

Rad_Vel
The average radial velocity of the selected stars in the cluster, in km/s.

Rad_Vel_Error
The standard error in the average radial velocity of the selected stars in the cluster, in km/s.

Num_Rad_Vel_Stars
The number of cluster stars used for the radial velocity calculation.

Num_Core_Stars
The number of most probable (so-called 1-sigma) members stars within the core region radius, r0. The membership probabilities for the individual stars in the cluster are given in the associated stars file for the cluster at CDS (see Data Products section above for more details).

Num_Central_Stars
The number of most probable (so-called 1-sigma) members stars within the central region radius, r1. The membership probabilities for the individual stars in the cluster are given in the associated stars file for the cluster at CDS (see Data Products section above for more details).

Num_Cluster_Stars
The number of most probable (so-called 1-sigma) members stars within the cluster radius, r2. The membership probabilities for the individual stars in the cluster are given in the associated stars file for the cluster at CDS (see Data Products section above for more details).

Distance
The cluster distance, D, from the Sun, in parsecs (pc). The methodology used to estimate D is discussed in Section 3.4.3 of Paper I. The authors consider the distances to be accurate to within +/- 16%. For young clusters, which have almost vertical and poorly populated main sequences, the accuracy of this parameter is considerably lower.

E_BV
The reddening (color excess), E(B-V), towards the cluster, in magnitudes. The methodology used to estimate E(B-V) is discussed in Section 3.4.3 of Paper I. The authors consider the reddening values to be accurate to within +/- 0.06 magnitudes (+/- ~ 10%). For young clusters, which have almost vertical and poorly populated main sequences, the accuracy of this parameter is considerably lower.

Distance_Modulus
The apparent distance modulus of the cluster in the 2MASS Ks band, i.e., the quantity [(5 * log (D)) - 5.0 + A_Ks_], where D is the distance to the cluster, in parsecs, and AKs is the extinction in the 2MASS Ks band towards the cluster. A standard interstellar reddening law is assumed, e.g., AV = 3.1 * E(B-V), AK = 0.95 * AKs, and AKs = 0.670 * E(J-Ks) (Cardelli et al.1989, ApJ, 345, 245; Dutra & Bica 2001, A&A, 376, 434). The authors consider the distance moduli to be accurate to within +/- 0.35 magnitudes. For young clusters, which have almost vertical and poorly populated main sequences, the accuracy of this parameter is considerably lower.

E_JK
The reddening (color excess), E(J-Ks), towards the cluster, in magnitudes.

E_JH
The reddening (color excess), E(J-H), towards the cluster, in magnitudes.

Delta_H
The correction to the H magnitude of the fitted isochrone, Delta-H. The authors found that the theoretical isochrones usually fitted the observed sequences in the Ks,(J - Ks)-diagrams better than in the Ks, (J - H) one. They observed a (J - H) color shift that is typically of about a few hundreds of a magnitude but it varied from cluster to cluster. They attribute this effect to a lack of a global calibration of the H-band in 2MASS and, additionally, to spatial variations of the properties of the absorbing dust that affect the H-band. Therefore, they introduced this empirical correction Delta-H to provide a better isochrone fit in the Ks, (J - H) diagram.

Log_Age
The logarithm of the average age of the stars in the cluster, log t, in years. The methodology used to estimate cluster ages and their accuracy are discussed in Section 3.4.3 of Paper I.

Log_Age_Error
The standard error in the logarithm of the average age of the stars in the cluster, log t, in years.

Num_Log_Age_Stars
The number of cluster stars used for the average cluster age calculation. A value of -1 for this parameter indicates that the age of the cluster was set manually.

King_Core_Radius
The core radius, rc, of a King model fit to the cluster RDP, in parsecs. This was estimated using the same technique as was applied earlier to COCD clusters (see Piskunov et al. 2007, A&A, 468, 151 for more details). The method is based on a three-parameter fit (rc, rt and a normalization factor) of cumulative King profiles to the observed density distribution of the cluster members.

King_Core_Radius_Error
The standard error in the core radius, rc, of a King model fit to the cluster RDP, in parsecs.

King_Tidal_Radius
The tidal radius, rt. of a King model fit to the cluster RDP, in parsecs. This was estimated using the same technique as was applied earlier to COCD clusters (see Piskunov et al. 2007, A&A, 468, 151 for more details). The method is based on a three-parameter fit (rc, rt and a normalization factor) of cumulative King profiles to the observed density distribution of the cluster members.

King_Tidal_Radius_Error
The standard error in the tidal radius, rt, of a King model fit to the cluster RDP, in parsecs.

King_Norm_Factor
The normalization factor of a King model fit to the cluster RDP, in parsecs-2. This was estimated using the same technique as was applied earlier to COCD clusters (see Piskunov et al. 2007, A&A, 468, 151 for more details). The method is based on a three-parameter fit (rc, rt and a normalization factor) of cumulative King profiles to the observed density distribution of the cluster members.

King_Norm_Factor_Error
The standard error in the normalization factor of a King model fit to the cluster RDP, in parsecs-2.

Reference_Code
The reference source for the MWSC list and input parameters for the cluster coded as follows:

    COCD = Kharchenko et al. (2005, CDS Cats. J/A+A/438/1163, J/A+A/440/403)
    DIAS = Dias et al. (2002, CDS Cat. B/ocl), Version 3.1, 24/nov/2010
    DREM = Dias et al. (2002, CDS Cat. B/ocl), Version 3.1, 24/nov/2010, removed
    MELN = Melnik & Dambis (2009, CDS Cat. J/MNRAS/400/518), associations
    FPRO = Froebrich et al. (2007, J/MNRAS/374/399), probable
    FPOS = Froebrich et al. (2007, J/MNRAS/374/399), possible
    BOPN = Bica et al. (2003, CDS Cat. J/A+A/404/223), Dutra et al. (2003,
            CDS Cat. J/A+A/400/533), New objects in the area of optical nebulae
    BIRN = Bica et al. (2003, CDS Cat. J/A+A/404/223), Dutra et al. (2003,
           CDS Cat. J/A+A/400/533) 2003, New objects in the area of radio/IR
           nebulae
    LLEM = Lada & Lada (2003ARA&A..41...57L), Embedded clusters in Molecular
            Clouds
    BIEM = Bica et al. (2003, CDS Cat. J/A+A/404/223); IR star clusters and
            stellar groups catalog
    HARR = Harris (1996AJ....112.1487H, CDS Cat. VII/202), edition 2010,
            2010arXiv1012.3224H, www.physics.mcmaster.ca/~harris/mwgc.dat
    ARIn = Objects from Paper III with b > +18.5 degrees
    ARIs = Objects from Paper III with b < -18.5 degrees
  
Two Paper III objects, 'MWSC 5901' and 'MWSC 5963', had reference_code values of 'ARIa' in the CDS table which are undocumented, and the HEASARC believes them to be erroneous. Based on their Galactic latitudes, the HEASARC has corrected these values to 'ARIn' and 'ARIs', respectively.

Cluster_Type
The source object cluster type, coded as follows:

    ass = stellar association
    ast = Dias: possible asterism/dust hole/star cloud
    dub = Dias: dubious, objects considered doubtful by the DSS images inspection
    emb = embedded open cluster/cluster associated with nebulosity
    glo = globular cluster/possible globular cluster
    irc = infrared cluster
    irg = infrared stellar group
    mog = Dias: possible moving group
    non = Dias: "non-existent NGC"/ objects not found in DSS images inspection
    rem = Possible cluster remnant
    var = clusters with variable extinction
  

Metallicity
The metallicity of the cluster, [Fe/H]. These values were copied from Conrad et al. (2014, A&A, 562, A54) or Dias et al. (2002, A&A, 389, 871), Version 3.1, 24/nov/2010; for globular clusters, they are taken from the revised Harris (1996, AJ, 112.1487, CDS Cat. VII/202) Catalog, 2010 edition, or are newly determined.

Metallicity_Error
The standard error in the metallicity, [Fe/H].

Num_Metallicity_Stars
The number of cluster stars used for the derived metallicity.

Comments
This parameter contains notes for many (but not all) of the objects.

Class
The HEASARC Browse object classification, based on the value of the broad_type parameter.


Contact Person

Questions regarding the MWSC database table can be addressed to the HEASARC User Hotline.

Page Author: Browse Software Development Team
Last Modified: 17-Sep-2014