Hunting for Ha (Part1) : Markarian’s Chain within the Virgo Cluster
Askar 151phq; AP Mach2 GTO; ASI6200MM, - Baader 6.5nm NB CMOS opt. filters
H: (73 x 550s Bin 1, Gain 200); R,G,B: (63,66,66 x 120s, Bin 1, Gain 100); L: (61x120s, Bin 1, Gain 100)
Total integration time = 20.0 hrs (Feb 4,12,13; Mar 13,15,16)
I was inspired by
the amazing IOD winner (Jan 6, 2023 by Jakob Sahner) of this subject matter to “see for myself”, the Ha signal that seems to bridge the distance between the irregular “eyes” galaxy “NGC4438” and the elliptical galaxy “NGC4406”.
I remember reading that there was essentially no Ha signal in the Virgo cluster – only small signals in the spiral and irregular galaxies where star formation was taking place. The elliptical galaxies contained older stars and there wasn’t any star formation taking place here, so one would not expect Ha signal – generally representative of star forming regions. So much so that rarely are Ha narrowband filters used to image the Chain at all.
The explanation for presence of a Ha signal “bridge” between and within the two galaxies is that these galaxies had collided in the past, and the elliptical galaxy stole hydrogen from the once spiral NGC4438. Star formation has likely recommenced in both galaxies due to the disruption of the Ha from the spiral arms. Seeing an elliptical galaxy with any Ha signal within is a real rarity.
My initial integration time of 20 hours shown here, is enough to convince me that the signal in
@Jakob 's image is real but falls far short of the 76 hours that produced the strong signal in his image. The bridge isn’t really visible, but the signal within the elliptical galaxy definitely is. While I won’t be able to produce something as stunning, my intent is to spend at least a few more nights getting some more hydrogen alpha and luminance data.
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