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J/AJ/126/1286    Hα+[NII] observations of M81 HII regions     (Lin+, 2003)
Hα+[N II] observations of the H II regions in M81.
    Lin W., Zhou X., Burstein D., Windhorst R.A., Chen J., Chen W.-P., Jiang Z.,
    Kong X., Ma J., Sun W.-H., Wu H., Xue S., Zhu J.
   <Astron. J. 126, 1286 (2003)>
   =2003AJ....126.1286L
ADC_Keywords: H II regions ; Spectroscopy

Keywords: galaxies: individual (M81) - galaxies: photometry - H II regions


Abstract:
    In a first of a series of studies of the Hα+[NII] emission from
    nearby spiral galaxies, we present measurements of Hα+[NII]
    emission from HII regions in M81. Our method uses large-field CCD
    images and long-slit spectra and is part of the ongoing
    Beijing-Arizona-Taipei-Connecticut Sky Survey (the BATC survey). The
    CCD images are taken with the National Astronomical Observatories of
    China (NAOC) 0.6/0.9m f/3 Schmidt telescope at the Xinglong Observing
    Station, using a multicolor filter set. The observations reported here
    were taken on 30 individual nights over the time period 1995 February
    5 to 1997 February 19. Spectra of 10 of the brightest HII regions are
    obtained using the NAOC 2.16m telescope with a Tek 1024x1024 CCD,
    between 1997 April 9 and 11. The continua of the spectra are
    calibrated by flux-calibrated images taken from the Schmidt
    observations. We determine the continuum component of our
    Hα+[NII] image via interpolation from the more accurately
    measured backgrounds (M81 starlight) obtained from the two neighboring
    (in wavelength) BATC filter images. We use the calibrated fluxes of
    Hα+[NII] emission from the spectra to normalize this
    interpolated, continuum-subtracted Hα+[NII] image. We estimate
    the zero-point uncertainty of the measured Hα+[NII] emission
    flux to be 8%. A catalog of Hα+[NII] fluxes for 456 HII
    regions is provided, with those fluxes being on a more consistent
    linear scale than previously available. The logarithmically binned
    Hα+[NII] luminosity function of HII regions is found to have
    slope α=-0.70, consistent with previous results (which allowed
    α=-0.5 to -0.8). From the overall Hα+[NII] luminosity of
    the HII regions, the star formation rate of M81 is found to be
    ∼0.68M☉/yr, modulo uncertainty with extinction corrections.

File Summary:

       FileName      Lrecl  Records   Explanations

ReadMe            80        .   This file
table4.dat        67      493   Catalog of Optically Bright H II Regions
                             with Hα Flux


See also:
   J/ApJ/438/181 : Observations of H II Regions in M81 (Hill+ 1995)


Byte-by-byte Description of file: table4.dat

   Bytes Format Units     Label    Explanations

   1-  5  A5    ---       Num      H II region PSK index number (1)
   7-  8  I2    h         RAh      Hour of right ascension (J2000)
  10- 11  I2    min       RAm      Minute of right ascension (J2000)
  13- 17  F5.2  s         RAs      Second of right ascension (J2000)
      18  A1    ---       DE-      Sign of declination (J2000)
  19- 20  I2    deg       DEd      Degree of declination (J2000)
  22- 23  I2    arcmin    DEm      Arcminute of declination (J2000)
  25- 28  F4.1  arcsec    DEs      Arcsecond of declination (J2000)
  30- 35  F6.1  arcsec    Xoff     X offset distance from the galaxy center (2)
  37- 42  F6.1  arcsec    Yoff     Y offset distance from the galaxy center (2)
  44- 47  I4    10-19W/m2 Flux     Hα+[NII] flux
  49- 51  I3    10-19W/m2 e_Flux   The 1 σ error in Flux
  53- 56  F4.1  arcsec    Diam     Aperture diameter used to measure Flux
  58- 61  I4   10-16mW/m2 PFlux    ? Flux measured by Petit et al.
                                     (1988A&AS...74..475P)
  63- 67  F5.1  ---       S/N      Signal-to-noise ratio

Note (1): PSK (Petit et al., 1988A&AS...74..475P) numbers.
          The last entry, 1993J, gives the measure of SN 1993J.
Note (2): The galaxy center of M81 is located at
           RA=09:55:33.2, DE=+69:03:55 (J2000.0).
    The Xoff and Yoff values are slightly different from those of PSK
    (1988A&AS...74..475P) because our astrometry puts the center of M81 in
    a different location, with an additional rotation of the field of view.


History:
    From electronic version of the journal
(End)                    Greg Schwarz [AAS], Patricia Bauer [CDS]    16-Oct-2003