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Far away in the constellation of Aries, in a 14th magnitude barred spiral galaxy designated as NGC 918… a star exploded with enough candlepower to briefly outshine its home. Discovered independently by Lick Observatory Supernova Search (LOSS) and Koichi Itagaki (Japan) on October 11, 2009, this Type II supernova might be hiding in the intergalactic dust, but it isn’t hiding from Joe Brimacombe.
So who is to blame for this poor intergalactic housekeeping condition, eh? Just exactly where did this film of dust come from that dims distant galaxies and cloaks supernova events? Try our own Milky Way. We’ve known since the first Palomar Sky Surveys that we’re looking through clouds and filaments of dust at high galactic latitudes. But it isn’t just our galaxy either… It’s our whole family! Chances are the entire local group is puffing out enough hydrogen to send up a smoke screen – possibly even with higher redshift extragalactic objects. And just who is the smoker of our group?
The Andromeda Galaxy – M31…
“Finally we come to the aspect which could most shake conventional beliefs about the Local Group and the nature of near space. Deep prints of a red sensitive Schmidt plate (Arp and Sulentic 1991) show unmistakable filamentary dust features reaching back along the minor axis direction toward M31.This filament is repeated in the blue photographs and 100 the hundred micron infra red scans. They have to be real. Although no one has cared to take a spectrum there is no hint of gaseous emission.” says Halton Arp.
“The ejection path across the whole Local Group sky from M31 to 3C120 must have carried material either dusty or capable of forming dust from the ejecting M 31. But that means dust and obscuration within the Local group of galaxies – a point which has never before been seriously advanced. But how can one escape the mult-iwavelength evidence? The most provocative object in the M31 minor axis line is NGC 918. The nebulous dust is most concentrated at the position of the galaxy but a region has been cleared on either side of the minor axis of the galaxy. Higher resolution images would give invaluable information on the process whereby ejections come out along the minor axis of galaxies. In addition the nebulosity is of such long extent across the sky and so coincident with the alignment along the M31 minor axis that it must be in the Local Group. Therefore interaction with the dust filament would represent direct evidence for a distance much smaller than NGC 918’s conventional redshift distance.”
“The filamentary features surrounding NGC 918 are well shown in this image. The outer features appear to be dust illuminated by the galaxy. Immediately around the galaxy the dust appears to cleared away. By either outflow of matter or radiation pressure from the galaxy.” explains Arp, “If the galaxy is not interacting with the nebulosity but just shining through a serendipitous hole we still have the remarkable inference that material has been ejected along the minor axis of M31 into the middle of the Local Group of galaxies. The question then arises as to how many other nearby galaxy groups contain intergalactic material and what this would do to our view of purportedly more distant galaxies.”
If dust is to blame for a clouded view here, is it possible that NGC 918 could be just as guilty of ignoring the Swiffer? Darn right it could. According to research done by E. E. Martinez-Garcia (et al), NGC 918 has its share of spiral density waves that present azimuthal color gradients that even an infrared passband won’t fully penetrate. “We believe that this effect may be due to the position of the dust lanes and stars with respect to the observer.” says Garcia, “More research needs to be done to understand the origin of this effect.”
In the meantime, we’ll thank Joe Brimacombe of Northern Galactic for being on watch and capturing this distant supernova within 24 hours of its discovery. Cuz’ another one bites the dust!
Although NGG 918 is located not too distant from the galactic equator, the diffuse nebulosity visible in the image in the article is likely due to Integrated Flux Nebula or High Velocity Clouds that surround the Milky Way’s thick galactic disk. Perhaps sub-millimeter or radio observations may help nail down the true composition of these diffuse nebula.
Great image, Nancy, of a distant supernova in a distant galaxy framed by nebulosity (& stars) in or near our Milky Way Galaxy ! Holy cosmic distance scales 🙂
Athough ‘faint’ and far away, the energy of this SN is awesome!!!!!. I wish to see a SN about 1k LY away in my lifetime, but, our closest most ‘promising’ old massive stars may explode tonight or in a million years. Human lifespans means nothing in the lifespan of any star!!!!!
@ Jon Hanford,
That’s not Nancy, that’s Tammy.
Is this the same dust Lyra & Will were looking for?
Also big thanks to Joe Brimacombe for sponsoring so many of the 365 Days of Astronomy podcasts.
“direct evidence for a distance much smaller than NGC 918’s conventional redshift distance”
When I read this kind of proposition, I’d like to have more context and details. When and where was that paper published? The 1991 date within the quote is a lower limit.
“no one has cared to take a spectrum”: maybe they have by now?
This article seems to me to take a blurry half-step in favor of Arp’s unconventional cosmology. If so, please state it clearly, I’d sure like to hear how the related questions have evolved over the last years, one way or another. Particularly regarding redshift / distance relationship.
Err, Sorry, Tammy, thanks for the great article (must drink coffee BEFORE posting 🙂
Concerning the post by Manu, I, too, was puzzled by the inference that this galaxy may be in some way connected to M 31 by this ‘dust trail’ or that even if not connected to M 31, this galaxy illuminates gas or dust ejected along the minor axis of M 31. But then, I realized this was a quote from a 1991 paper by Arp and Sulentic (and another unsubstantiated claim from Arp) hinting at his galaxy ejection ‘hypothesis’. The 1991 paper (w-poor reproductions of black and white photographic plates) can be found here: http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?1991Ap%26SS.185..249A&data_type=PDF_HIGH&whole_paper=YES&type=PRINTER&filetype=.pdf .
I think Arp’s statement “there is no hint of gaseous emission” actually supports the theory that this is a Integrated Flux Nebula in our galaxys’ outer halo, illuminated faintly (in both red and blue light) by the luminous disk of our own Milky Way galaxy. A check of the galactic absorption maps by Schlegel, Finkbeiner, and Davis should help to confirm this interpretation. Arp points out in his paper that extragalactic dust clouds are known to exist, and he references M 81 as a prime example. In this particular case, Arp is correct to a point (clusters embedded in some of the tidal debris and gas near M 81 are spectroscopically proven to lie at the distance of the M 81 Group). But the area around M 81 is also chock full of IFN from our own galaxy (remember, M 81, M31 and NGC 918 all lie close to the galactic plane of the Milky Way).
Joe Brimacombe may want to consider submitting his image to the Mandel-Wilson Unexplored Nebula Project that has several pages of photos, information and descriptions of Integrated Flux Nebula here: http://www.galaxyimages.com/UNP_IFNebula.html . The above link contains beautiful deep images of these ghostly, extremely faint and rarely imaged nebulae, especially near the M 81 group and the North Celestial Pole. Congrats to Joe for getting a supernova, a galaxy and a IFN all in one (deep) image!
Thanks Jon!
I’ll look at that paper in a little while.
Btw, while looking for the 1991 Arp paper on NED (the NASA/IPAC Extragalactic Database), I found the redshift given for NGC 918 as z=0.005027 while the BLUEshift given for M 31 (yes, its approaching us) as z=+0.001001, so they don’t appear to be close to each other. I also forgot to mention that M 31 does have a (invisible to our eyes) neutral hydrogen bridge and a sparse number of stars between itself and M 33 from a past encounter. And no, I don’t think M 33 was ‘ejected’ from the nucleus of M 31 🙂
While I found many links to Integrated Field Nebulosity (through Google) I came across the deep 12 hour LRGB color image of the M 81 Group and its’ surrounding IFN taken by Jordi Gallego and featured on the APOD site. Enjoy: http://astrosurf.com/jordigallego/index.html .