First atomic hydrogen spectral line images of a nearby galaxy

Mar 15, 2012
Kat7 Spectral Line - The green contours in this image show the distribution of the atomic hydrogen gas overlaid on an optical image of the same galaxy - showing clearly that the emissions from the hydrogen gas come from a much larger region than that seen by the optical image. (The Digital Sky Survey was produced at the Space Telescope Science Institute under US Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope.)

South Africa’s KAT-7 telescope, a seven-dish array which is a precursor to the much larger MeerKAT telescope in the Karoo and to the Square Kilometre Array, has reached another major milestone by observing the radio emission from the neutral hydrogen gas (HI) in a nearby galaxy. Hydrogen gas emits radio emission in a spectral line at a very specific frequency of 1420 MHz.

The astronomers pointed the telescope towards a galaxy called NGC 3109 – a small spiral galaxy, about 4.3 million light-years away from Earth, located in the constellation of Hydra. The observation allowed them to see the HI radio emission of this galaxy, as well as to see how this galaxy is moving. Where the gas is moving towards us, the frequency of the spectral line is Doppler-shifted upwards; where the gas is moving away, the frequency is shifted down. In this way, astronomers can map the way in which all of the gas in the galaxy is moving.

“These exciting results achieved by KAT-7 have given us confidence that we know how to build a cutting-edge radio telescope in Africa to answer some of the fundamental questions in radio astronomy”, says Dr Bernie Fanaroff, director of SKA South Africa. “Our team in the SKA South Africa Project and universities has again shown that they can deliver cutting-edge technology and do excellent science on a very tight schedule.”

“A large proportion of the science planned for the SKA – and MeerKAT – involves mapping of the universe using neutral hydrogen. Because of the ongoing expansion of the universe, distant are moving away from us. Measuring the frequency of the spectral line from neutral hydrogen in those galaxies allows us to work out how far away they are. By finding billions of distant galaxies, astronomers will be able to map the structure of the universe and how it has changed over time. This cosmic census of the neutral hydrogen in galaxies – far and near – is essential in understanding the deeper physics of the universe, by answering fundamental questions such as the nature of dark matter and dark energy.”

Rotating Galaxy -This image shows that the galaxy is rotating with the blue towards the viewer and the red away. The rotation is not uniform and the structure can be used by astronomers to model the distribution of matter in the galaxy. Current thinking is that most of the matter is actually dark matter, which can’t be seen but whose presence can be confirmed by these kinds of observations.

“Observations of the neutral content of galaxies also help to form a picture of how galaxies have evolved over cosmic time and show how our own galaxy, the spiral galaxy called the Milky Way, has developed,” Fanaroff adds.

The radio waves which KAT-7 picks up from the galaxy were processed in the correlator, the first stage of computing. The correlator currently allows measurement of the gas velocity to an accuracy of 10 km/s. Further upgrades during 2012 will enable astronomers to study this galaxy with a velocity resolution of 1 km/s.

“Such a high velocity resolution will allow us to distinguish between the conventional models which suppose the presence of an important quantity of dark matter (matter that cannot be seen but that is detected by its gravitational influence) and the Modified Newtonian Dynamics (MOND) models which suppose that no dark matter is present but that it is instead the laws of gravity that change on galaxy scales,” explains Prof Claude Carignan, South African SKA Research Chair in Multi-Wavelength Astronomy at the University of Cape Town (UCT).

“We also speculate that an unusual warp in the disk of this galaxy could be caused by a tidal interaction with its dwarf companion galaxy known as Antlia,” Carignan adds. “Future KAT-7 observations should reveal more information on this possible interaction.”

“It is particularly exciting that we will soon be able to derive new scientific results with a relatively small precursor array,” says Bradley Frank, PhD student at UCT and lead researcher for the HI imaging of nearby galaxies with KAT-7.

Explore further: Gravitational waves according to Planck

More information: www.ska.ac.za/

Provided by South African Square Kilometre Array Telescope

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chuckscherl
not rated yet Mar 15, 2012
Sounds like this is a first. Meaning that is was dark. Will this put a dent in dark matter percentage. The spectral line in the photo resembles the pattern of perceived Dark Matter
Tuxford
1 / 5 (2) Mar 15, 2012
This galaxy does not appear spectacularly active. The existence of the gas halo is further support for my prediction that dark matter is a etheric state precondition to the nucleation of new matter in the halos surrounding galaxies. There is no god particle. And yesterdays news that dark matter distribution in a cluster is somewhat reduced near the massive center is also supportive for this model. I have predicted that such halos will be found around most galaxies.

http://www.physor...ive.html

Where does this gas come from? Is it all ejected from the core, and then smoothly distributed? Watch astronomers come up with still more convoluted explanations, when a simple one fits best. Is that intelligence??? Then universities should be called to account for breeding stupidity for lot's of money.
Callippo
1 / 5 (1) Mar 15, 2012
The observation of distant galaxies at the 21-cm hydrogen line could confirm or falsify the dense aether model of steady-state model, in which the Universe at the wavelengths longer than the CMBR should appear collapsing instead of expanding. Unfortunately the NGC 3109 galaxy is not very distant one and the observation of more distant ones is hindered with the fact, the intergalactic gas blocks the hydrogen radiation nearly completely.
Callippo
1 / 5 (1) Mar 15, 2012
is a etheric state precondition to the nucleation of new matter in the halos surrounding galaxies. There is no god particle
Dense aether model considers the condensation of intergalactic matter from photons and neutrinos, which are ejected in less or more invisible jets from central area of galaxy. The interpretation of god particle has nothing very much to do with it.
Is that intelligence?
It's the business model, providing the optimization of grants and jobs positions. Scientists aren't motivated in very fast progress of science, as R. Wilson, a former president of APS recognized and named already.
javjav
5 / 5 (1) Mar 15, 2012
The existence of the gas halo is further support for my prediction that dark matter is a etheric state precondition to the nucleation of new matter in the halos surrounding galaxies.


Not so fast my friend. Dark matter gravity account for 5 times the visible matter gravity. If there where 5 times more hydrogen in the halo than in the core it should be ridiculously evident. Hydrogen atoms radiate and interact a lot with light and with other hydrogen. It looks more like a much smaller amount of Hydrogen is trapped in the halo by the dark matter gravity. In fact, when having more resolution it could provide another clue about dark matter existence. Or maybe not, but in any case, your radical position is the opposite to what science needs.
Vendicar_Decarian
not rated yet Mar 16, 2012
"If there where 5 times more hydrogen in the halo than in the core it should be ridiculously evident." - javjav

A spherical distribution of DM in a halo around the galaxy would be many times less dense than the radiant matter observed in the galaxy.

Not only is the sphere much larger in volume than the thin plane of the galaxy, but the halo is thought to be larger.

Even if only double the radius, a dark matter halo's volume is at a minimum 8 times higher or 5/8 ths the density.

I am wondering if this DM is just not a very diffuse light "plasma", consisting of grains of solid hydrogen ice, singularly ionized and thousands/millions of hydrogen molecules in composition, in an equally diffuse sea of electrons left from the ionization.

Such matter would act gravitationally but be prevented from collapsing fast due to strong repulsive forces from the charge.

Without numbers I can imagine that the electron density is so low that radio emissions from this "plasma" are undetectable.
Tuxford
2 / 5 (4) Mar 16, 2012
Dark matter gravity account for 5 times the visible matter gravity.


Not if as LaViolette indicates, that this precondition etheric state of the 'vacuum' actually refracts light. And further if Doppler effect is not the sole component of red shift, which is used to infer galactic rotation. Then the whole notion of dark matter to matter ratios must be reconsidered. Beware of 'accepted' conclusions. I have concluded that physicists simply have not the tools to understand this systems theory-based physics model. Perhaps they should study EE, as I did.