J/A+A/366/498       VI photometry of M33 star clusters          (Chandar+, 2001)
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Star clusters in M33. IV. A new survey from deep HST images.
     Chandar R., Bianchi L., Ford H. C.
    <Astron. Astrophys. 366, 498 (2001)>
    =2001A&A...366..498C
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ADC_Keywords: Clusters, globular ; Photometry, VRI
Mission_Name: HST
Keywords: galaxies: individual (M33) - galaxies: star clusters -
          galaxies: evolution

Abstract:
    We have detected 102 star clusters in M 33, from 35 deep Hubble Space
    Telescope (HST) WFPC2 fields taken from our program and from the HST
    archive. Twenty-eight fields have V and I band imaging, and an
    additional seven fields are imaged in a single V filter. Eighty-two of
    the clusters were previously unknown. Integrated photometry reveals
    that 25 clusters have (V-I) colors typical of those found in Galactic
    globular clusters (only ten of these objects were previously known).
    Our discovery of 15 new globular cluster candidates increases previous
    estimates of the old cluster population in M 33 by ~60%. An additional
    eleven objects (only two were previously known) have colors expected
    for intermediate age clusters. The new clusters have a range of ages
    from 6 million years to >15Gyrs, and masses between
    10^2^M_{sun}_-10^6^M_{sun}_, although these parameters are estimated
    from only one color.

Description:
    File table2 contains coordinates and photometric properties of compact
    M33 clusters discovered in Hubble Space Telescope WFPC2 V and I band
    images. The columns contain: identification, RA (J2000), DEC (J2000),
    galactocentric distance (kpc), apparent V magnitude, radius used to
    measure color, Johnson-Cousins (V-I) color, cross identification of
    objects with Christian & Schommer (1988AJ.....95..704C) and Mochejska
    et al. (1998AcA....48..455M), previously published V magnitude if
    available, previously published (V-I) color if available, and
    estimated core radius.

File Summary:
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  FileName   Lrecl  Records   Explanations
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ReadMe          80        .   This file
table2.dat      96      102   M33 clusters detected in deep HST WFPC2 fields
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See also:
  J/ApJS/122/431 : Star Clusters in M33. I. (Chandar+, 1999)
  J/AJ/121/861   : BVI photometry of central part of M33 (Macri+, 2001)
  J/AJ/121/870   : Variables in the central part of M33 BVI phot. (Macri+, 2001)
  J/AJ/110/1649  : HST VI photometry near the M33 nucleus (Mighell+ 1995)
  J/AJ/110/2715  : UBV photometry in NGC 6822, M31 and M33 (Massey+ 1995)

Byte-by-byte Description of file: table2.dat
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   Bytes Format Units   Label     Explanations
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   1- 3    I3    ---     ID       Identification Number (1)
   5       I1    h       RAh      Right ascension (J2000)
   7- 8    I2    min     RAm      Right ascension (J2000)
   10- 14  F5.2  s       RAs      Right ascension (J2000)
   16- 17  I2    deg     DEd      Declination (J2000)
   19- 20  I2    arcmin  DEm      Declination (J2000)
   22- 26  F5.2  arcsec  DEs      Declination (J2000)
   28- 30  F3.1  kpc     Dist     Deprojected galactocentric distance
   32- 37  F6.3  mag     Vmag     Apparent V magnitude (measured in 2.2" radius)
   38- 39  A2    ---   u_Vmag     [: ] Uncertainty flag on Vmag (2)
   41- 45  F5.3  mag   e_Vmag     ? Formal uncertainty in V magnitude (3)
   47- 49  F3.1  arcsec  Crad     ? Color radius (4)
   51- 55  F5.3  mag     V-I      ? Johnson-Cousins  (V-I) color
   57- 61  F5.3  mag   e_V-I      ? Uncertainty in (V-I) color (3)
   63- 79  A17   ---     Com      Comments and Cross- identification (5)
   81- 85  F5.2  mag     Vmagp    ? Previously published V magnitude
   87- 90  F4.2  mag     V-Ip     ? Previously published (V-I) color
   92- 95  F4.2  pc      Radc     ? Core radius
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Note (1): Cluster numbering begins at 61, since this catalog is a continuation
           of our previous survey of M33 clusters (Chandar, Bianchi & Ford,
           1999, Cat. <J/ApJS/122/431>).
Note (2): The V magnitude is measured in a 2.2 arcsecond radius unless otherwise
           noted. A colon (:) after the V magnitude indicates that the total V
           magnitude was measured in a 2.7 arcsecond aperture to include most of
           the cluster extent. A double colon (::) indicates that the cluster
           is located near the edge of a CCD, resulting in the use of a smaller
           aperture for the V magnitude (typically 0.8 arcseconds).
Note (3): The quoted errors are 1{sigma} formal errors from the PHOT task in
           IRAF, and include counting statistics, gain, and background
           variations. Given that the objects are extended, the uncertainties
           are not significant for absolute comparison with different sets of
           data.
Note (4): Radius for (V-I) color measurement given in Core radius.
Note (5): COmparison photometry:
             CS: taken from Christian & Schommer (1988AJ.....95..704C)
          MKKSS: taken from Mochejska et al. (1998AcA....48..455M)
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References:
    Chandar et al.,   Paper I     1999ApJS..122..431C = Cat. <J/ApJS/122/431>
    Chandar et al.,   Paper II    1999ApJ...517..668C
    Chandar et al.,   Paper III   1999PASP..111..794C
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(End)    Rupali Chandar [Johns Hopkins Univ.], Patricia Bauer [CDS]  28-Nov-2000
