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J/AJ/111/1128       UV-UBV photometry in NGC 595 (Malumuth+ 1996)
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The stellar initial mass function in the giant H II region NGC 595
     Malumuth E.M., Waller W.H., Parker J.W.
    <Astron. J. 111, 1128 (1996)>
    =1996AJ....111.1128M
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ADC_Keywords: H II regions ; Photometry, UBV ; Photometry, ultraviolet

Abstract:
    As part of a larger effort to study the resolved and composite
    properties of the giant H II regions in Messier 33, we have analyzed
    multiband HST/WFPC-2 images of NGC 595 in terms of the ionizing
    cluster's resolved stellar population. Photometric reductions of the
    PC images yield 100 stars in the UV image, 272 stars on the U image,
    345 stars on the B image, and 561 stars on the V image. A total of 267
    stars are common to the U, B, and V images while 86 stars are detected
    on all 4 images. Although some clustering is evident, the degree of
    central concentration is less than that seen in 30 Doradus. The
    resulting U-B vs B-V diagram of the resolved stars is used to
    determine the reddening of each star. The average reddening derived
    from this diagram is E(B-V)=0.36+/-0.28mag. The dereddened color-M_V
    diagram is best fit by a model cluster having an age of 4.5+/-1.0Myr,
    and hence initial masses no greater than 51M_{sun}_. A total of 13
    supergiant stars and 10 candidate WR stars
    [Drissen et al. (1993AJ....105.1400D), and references therein] are
    identified with M_V=-5 to -8mag. The remainder are main-sequence
    O-type (98) and early B-type (>145) stars with M_V=-1 to -6mag. The
    ratio of WR to O stars is WR/O=0.11+/-0.01, roughly the same as found
    in the core of 30 Doradus. The resulting luminosity function has a
    slope of alpha=-0.71. The derived IMF has a slope of
    Gamma=-1.32+/-0.02 before subtracting a background component, and
    Gamma=-1.00+/-0.05 after subtracting a background based on photometry
    of the surrounding WF images. Integration of the derived IMF down to a
    lower mass limit of 4M_{sun}_ yields a total mass of 7350M_{sun}_,
    while integration down to 0.1_{Msun}_ yields a total mass of
    18000M_{sun}_. The total estimated ionizing luminosity is
    5.0x10^50photon/s, roughly half that which is inferred from the Halpha
    luminosity in this region. This shortfall of ionizing photons can be
    reconciled by allowing for a spread in the stellar ages, and/or
    increasing the modeled EUV luminosity of the stars at the inferred
    cluster age.

File Summary:
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 FileName    Lrecl    Records   Explanations
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ReadMe          80          .   This file
table1.dat      62        573   NGC 595 photometry
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Byte-by-byte Description of file: table1.dat
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   Bytes Format  Units   Label    Explanations
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   1-  3  I3     ---     ID       Identification number
   5-  8  I4     ---     DMS      []? Star number from table 1 of Drissen et al.
                                       (1993AJ....105.1400D)
  11- 12  I2     h       RAh      Right ascension, J2000
  14- 15  I2     min     RAm      Right ascension, J2000
  17- 21  F5.2   s       RAs      Right ascension, J2000
      24  A1     ---     DE-      Declination sign
  25- 26  I2     deg     DEd      Declination, J2000
  28- 29  I2     arcmin  DEm      Declination, J2000
  31- 34  F4.1   arcsec  DEs      Declination, J2000
  36- 41  F6.2   mag     UVmag    []? Ultraviolet magnitude (F170W HST filter)
  43- 48  F6.2   mag     Umag     []? U magnitude
  50- 55  F6.2   mag     Bmag     []? B magnitude
  57- 62  F6.2   mag     Vmag     []? V magnitude
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Origin: AAS CD-ROM series, Volume 6, 1996         Lee Brotzman [ADS] 02-May-1996
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(End)                                                         [CDS]  05-Sep-1996