WLM Wolf-Lundmark-Melotte I

Local Group Galaxy in Cetus

Uploaded 12/15/07

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This Local Group Galaxy outlier is extremely difficult to image due to its low surface brightness, extended size and low declination. Located on the border of Cetus and Aquarius, this 11th magnitude object is 12 x 4 arcminutes in size and was first discovered in 1909 by Max Wolf. Its nature as a galaxy was only established in 1926 by Knut Lundmark and Philibert Jacques Melotte (1880-1961). Not only is WLM at the frontier of the Local Group, but it is also very isolated – its nearest neighbor, the dwarf galaxy IC 1613, a full million light-years away. Quite elongated, with a largest extension of more than 8,000 light years, WLM is about 12 times smaller than the Milky Way. Yet the discovery around it of many outlying red stars suggests that even such galactic minnows may have haloes and that WLM may be similar to our own galaxy in age.

Imaging this object is a challenge to say the least. Because it is very low on the horizon, the seeing dominates the quality. Here, stars have been resolved across the face of the galaxy, most dimmer than magnitude 20. A lack of obvious HII regions in the RGB data shows the galaxy to be rather gas poor, however I do plan on some deep hydrogen exposures to be certain.

Instrument: 12.5" f/5 Home made Newtonian Mount: Astrophysics 1200 QMD CCD Camera: SBIG 10XME NABG with Enhanced Water Cooling Guider: Meade DSI Pro w/Lumicon Newt Easy Guider Exposure: LRGB = 80:20:20:20 (RGB Binned 2x2) AstroDon RGB Combine Ratio: 1: 1.05: 1.11 Location: Payson, Arizona, Elevation: 5150 ft. Sky: Seeing FWHM = 4.5 arcsec (Maxim DL - 10min subframe), Transparency 8/10 Outside Temperature: 30 F CCD Temperature: -30 C Image Processing Tools: Maxim DL: Calibration, deblooming (Starizona Debloomer), aligning, stacking PixInsight: Curves, Deconvolution, noise reduction Photoshop CS2: Curves, Color Correction, Gradient removal (Grad Xterminator), Cleanup HOME GALAXIES EMISSION NEBS REFLECTION NEBS COMETS GLOBULARS OPEN CLUST PLANETARIES LINKS