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 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 1988A&AS...74..475P)
63- 67 F5.1 --- S/N Signal-to-noise ratio
--------------------------------------------------------------------------------
Note (1): PSK (Petit et al., 1988A&AS...74..475P 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 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