The hidden galaxy in the zone of avoidance

Aug 11, 2011 By Jon Voisey, Universe Today
The Fornax dwarf galaxy is one of our Milky Way’s neighbouring dwarf galaxies, similar to the one discovered. Credit: ESO

There are some places astronomers dare not tread. One of the prime places is beyond the disk of our own galaxy where the numerous stars and clouds of dust along the line of sight make observations messy to say the least. This obscured portion of the sky is known as the Zone of Avoidance. But despite the challenges, one team of astronomers has searched through it and found a previously undiscovered galaxy lurking not too far from our own.

To discover this galaxy, the team, lead by graduate student Travis McIntyre at the University of New Mexico, used the gigantic Arecibo radio telescope. This telescope is adept at finding emission at the 21 centimeter wavelength emitted by cool, atomic hydrogen. This long wavelength is relatively immune to the diminishing effects of gas and dust within our galaxy.

After the initial discovery, the team followed up with further observation using the Expanded Very Large Array, which also operates in the radio, as well as the 0.9 meter Southeastern Association for Research in Astronomy telescope, which is an , in hopes of peering through some of the muck.

While the galaxy was easily recovered in the second radio search, and the showed a faint clump, the centers of the two did not appear to line up. The visual and radio components seemed not to overlap almost at all. A portion of the reason for this is that the team was unable to image the faint galaxy out to its full extent before the contamination from our own galaxy overwhelmed the signal. As such, the two likely overlap more than is indicated by the study, but this would still indicate that the distribution of within it is severely lopsided.

Another possibility is that the object detected isn’t really a galaxy at all and is a coincidence of an alignment between a high velocity cloud and an independent cluster of stars. However, such clouds of gas tend to travel in packs and no others are known in the area, making this possibility unlikely.

If the object is a galaxy, it is likely a blue dwarf galaxy with some 10 million solar masses. The team expects that, while the galaxy is relatively nearby, this galaxy is not likely to bea member of the local group because, were it that close, it would be unprecedentedly small. As such, they applied Hubble’s Law to give a rough distance of 22 million light years but caution that at such distances, there is a large velocity dispersion and this estimate may be unreliable.

Searching for like this one in the Zone of Avoidance are important to astronomers because the mass of such undiscovered galaxies may help to resolve the unexpected “discrepancy between the cosmic microwave background dipole and what is expected from gravitational acceleration imparted on the Local Group by matter in the local universe.”

Explore further: Astronomers find 'cousin' planets around twin stars

add to favorites email to friend print save as pdf

Related Stories

Dwarf galaxy has giant surprise

Jan 12, 2005

Huge gas disk may be similar to stuff of early universe An astronomer studying small irregular galaxies has discovered a remarkable feature in one of them that may provide key clues to understanding how galaxies form and ...

'Big baby' galaxy found in newborn Universe

Sep 28, 2005

The NASA/ESA Hubble Space Telescope and NASA’s Spitzer Space Telescope have teamed up to 'weigh' the stars in distant galaxies. One of these galaxies is not only one of the most distant ever seen, but it appears to be unusually ...

No stars in the clouds

Jan 10, 2006

A team of astronomers from the University of Pittsburgh and the Universitäts-Sternwarte München in Munich, Germany, announced today in a paper presented at the meeting of the American Astronomical Society in Washington, ...

New Hydrogen Clouds in the M81 Group of Galaxies

Jan 10, 2008

A composite radio-optical image shows five new clouds of hydrogen gas discovered using the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT). The spiral galaxy M81 and its satellite, ...

Spitzer sees spider web of stars

Jul 21, 2011

(PhysOrg.com) -- Those aren't insects trapped in a spider's web -- they're stars in our own Milky Way galaxy, lying between us and another spiral galaxy called IC 342. NASA's Spitzer Space Telescope captured ...

Recommended for you

How small can galaxies be?

Sep 29, 2014

Yesterday I talked about just how small a star can be, so today let's explore just how small a galaxy can be. Our Milky Way galaxy is about 100,000 light years across, and contains about 200 billion stars. Th ...

The coolest stars

Sep 29, 2014

One way that stars are categorized is by temperature. Since the temperature of a star can determine its visual color, this category scheme is known as spectral type. The main categories of spectral type are ...

Simulations reveal an unusual death for ancient stars

Sep 29, 2014

(Phys.org) —Certain primordial stars—those 55,000 and 56,000 times the mass of our Sun, or solar masses—may have died unusually. In death, these objects—among the Universe's first-generation of stars—would ...

User comments : 4

Adjust slider to filter visible comments by rank

Display comments: newest first

that_guy
not rated yet Aug 11, 2011
but this would still indicate that the distribution of hydrogen gas within it is severely lopsided.


well, wouldn't that be expected of a small galaxy interacting with a much larger one??? We've seen plenty of pictures of colliding galaxies, and the stretched out forms of the magellanic clouds...
DavidMcC
5 / 5 (1) Aug 12, 2011
That guy, the Large Magellanic cloud is only ~160Klyr from the Milky Way. This object is at ~22Mlyr, about 100 times the distance, so the gravitational interactions are much weaker.
yyz
not rated yet Aug 15, 2011
There are several notable (and nearby) galaxies hidden behind the dusty veils of the Northern Milky. IC 10, IC 342, NGC 6946 and Maffei I & II come to mind. Some would be fine naked-eye objects for fortuitously situated naked-eye observers.

Well worth the time to locates these faint, *nearby* galaxies. Many even fainter samples of obscured nearby dwarf galaxies are found all along the Milky Way. Quite a dynamic space around the MWG over long timescales.
yyz
not rated yet Aug 16, 2011
"well, wouldn't that be expected of a small galaxy interacting with a much larger one??? We've seen plenty of pictures of colliding galaxies, and the stretched out forms of the magellanic clouds..."

As DavidMcC pointed out, this dwarf galaxy, ALFA ZOA J1952 1428, appears to be an isolated system. According to the discovery paper, this is likely a small Blue Compact Dwarf galaxy lying approx. 7Mpc from us and is apparently unconnected with the Local Group or any other known nearby galaxy group.

It appears to be 1300 x 1400pc across and contains a paltry 10E7 solar masses of HI.

The McIntyre et al paper with additional details here: http://arxiv.org/...43v1.pdf