Fabry-Perot Observations

Observations of M82 were obtained in February, 1986 at the 3.6-meter Canada-France-Hawaii telescope (CFHT) on Mauna Kea, in the emission lines of H$\alpha$ $\lambda$6563 and [NII] $\lambda$6583. The Hawaii Imaging Fabry-Perot Interferometer (HIFI; [Bland & Tully 1989]) was used with an ET-50 etalon from Queensgate Instruments. The etalon coatings were formulated to provide a free spectral range of 85Å and a finesse of 60, for a spectral resolution of 1.4Å (65 km s^-1, at H$\alpha$). The 512$\times$512 pixels of the Texas Instruments CCD, after 2$\times$2 on-chip binning, each subtend 0.''86 ($\sim$13 pc at the distance of M82). This scale undersampled the estimated 1'' seeing disk but was necessary due to the low flux levels of the outflow emission. The 3.'5 field covers almost the entire region of minor-axis optical filaments. Other characteristics of the observing system are provided in Table 2, along with their experimentally determined values.

A second set of Fabry-Perot observations were obtained in March, 1992 at the University of Hawaii 88-inch telescope on Mauna Kea, in the emission line of [OIII] $\lambda$5007. Again the HIFI system was used, with an ET-70 etalon owned by Dr. Sylvain Veilleux. Although the free spectral range of this etalon (61Å) was smaller than that used for the H$\alpha$ and [NII] observations, the finesse was essentially identical, as were the effective spatial and velocity resolutions (0.''85 pix^-1 and 60 km s^-1 at [OIII], respectively) and the field of view. The characteristics of the observing system are provided in more detail in Table 2. In both cases, the etalon was tilted to remove internal reflections and paired with wide (50Å FWHM) interference filters to eliminate interorder confusion problems.

 

$$\alpha$$ [OIII] Observations

Constant theoretical experimental theoretical experimental

Telescope/Instrument: CFHT + HIFI UH88 + HIFI

D_tel telescope diameter 3.6 m 2.24 m

f_cam camera focal length 90 mm 50 mm

Detector: IfA CCD + VISACOM ^a CCD

$$p_\mu$$ pixel size 30 micron 24 micron

$$p^{\prime\prime}$$ plate scale 0.''86 pix^-1 0.''846 pix^-1

$$\times \times$$ n_p CCD size

t exposure time 450 sec 480 sec

Etalon: CFHT3 SV1

$$\Delta\lambda$$ free spectral range (FSR) 85 Å 87.9 Å 61 Å 55 Å

N_R reflective finesse 60 45-50 60

n order of interference 75 72 91 91

$$\Lambda_v$$ velocity resolution 65 km s^-1 60 km s^-1 Observations

$$\delta\lambda$$ sampling increment 0.96 Å 0.99 Å 0.67 Å

$$\delta v$$ sampling increment 44 km s^-1 45 km s^-1 40.5 km s^-1

^a Values include 2$\times$2 binning.