Observed Spectral profile of M20

Date & Time: Sep 28 2013, 19:06 JST(+0900), 1min. exposed
Optical: TAKAHASHI 12.5cm(4.9") fluorite refractor, stopped D=100mm (f=1000mm, F10.0)
with SBIG DSS7 Spectrometer
Auto-guided with VIXEN ATLUX Equatorial
Cooled CCD Camera: SBIG ST-402ME (Temp.: -10°C)
Location: Ooizumi, Hokuto city, Yamanashi pref.

Upper strip: taken spectrogram, Lower strip: stretched 3-pixel-width & pseudo-colored image
Magnified profile around Hα line
Solid circle: Observed intensities
Megenta: Gaussian curves of Hα & N II lines
Yellow: Overlay of the Gaussians


This page shows a spectrogram and a profile provided from the image of the central region of M20 (Trifid nebula). The spectrogram shows a shadow corresponding to a dark lane of the nebula. The profile has been provided from a central part, positioning at an emitting part of M20, of the slit of spectrometer. Although the spectral image has lower S/N in shorter wavelength region due to lower surface brightness of the nebula, the profile includes various emission lines of the Balmer series from H-alpha to H-gamma, the ionized oxygen of O III, and weak signals of the ionized nitrogen (N II), sulfur (S II), neutral helium (He I) atoms, and so on.
A magnified spectral profile around the wavelength of H-alpha and N II lines is shown in the right hand side of full-ranged profile. The profile shows calculated intensities as solid curves fitted to measured ones under an assumption that individual emission lines have the Gaussian distribution with a standard deviation, σ =8Å. The relative intensity of N II line to that of H-alpha line can be estimated as about 26%.

Slit position at M20 (north in up)

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