Observed Spectrum of M57

Observed Spectral profiles of M57

Upper: Profile of ring part of M57, Lower: Profile of hollow part

Date & Time:	Jan 28 2012 from 28:42 to 28:47 JST(+0900)
	Composed 2 shots with 5 minutes exposed
Optical:	Meade 25cm(10") Schmidt Cassegrain (f=2500mm, F10.0)
	with SBIG DSS7 Spectrometer
	Auto-guided with Meade LX200 Equatorial & Pictor 201 XT
Cooled CCD Camera:	SBIG ST-402ME (Temp.: -25°C)
Location:	Ooizumi, Hokuto city, Yamanashi pref.

Upper strip pasted in each profile is taken spectrogram,
lower one is stretched 3-pixel-width & pseudo-colored image of individual parts.

Magnified profiles around Hα line
(Upper: Ring part, Lower: Hollow part)

Solid circle: Observed intensities
Megenta: Gaussian curves of Hα & N II lines
Yellow: Overlay of the Gaussians

This page shows you the observed spectral profile of M57 with a spectrometer.
The spectrometer has a slit length covering the diameter of M57, the spectrum image has recorded a "section" of the nebula. Individual emission lines have knots in both ends which correspond to both "ring" parts of M57, and the "hollow" part of the nebula is equivalent to squeezed part between the knots of observed lines. Two sets of spectrum profiles displayed in upper and lower of this page indicate the ring and hollow parts of M57, respectively.
Clear differences cannot be recognized between two parts in characteristics of emission lines of ionized oxygen, O III, Hβ, and so on, but we can detect a striking difference around Hα line. There are two neighboring emission lines from ionized nitrogen atoms of N II (at 6548Å and 6583Å). The N II lines are predominant in the ring part of M57, while the profile of the hollow part shows that the intensity of Hα line looks being far superior to those of N II lines.
The magnified spectral profiles around the wavelength of Hα line are shown in the right hand sides of individual full-ranged profiles. The profiles show calculated intensities as solid curves fitted to observed ones under an assumption that individual emission lines have the Gaussian distribution with a standard deviation, σ = 8Å. In case that the intensity of Hα line takes 100%, the relative intensities of two N II lines at 6548Å and 6583Å in the ring and hollow parts of M57 have 81%-181% and 18%-29%, respectively. It's considered that the differences in spectral profiles reflect the uneven distribution of gaseous matters in the nebula.

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