Clearing the 'cosmic fog' of the early universe: Massive stars may be responsible

ScienceDaily (Oct. 13, 2011) — The space between the galaxies wasn't always transparent. In the earliest times, it was an opaque, dense fog. How it cleared is an important question in astronomy. New observational evidence from the University of Michigan shows how high energy light from massive stars could have been responsible.

Astronomers believed that early star-forming galaxies could have provided enough of the right kind of radiation to evaporate the fog, or turn the neutral hydrogen intergalactic medium into the charged hydrogen plasma that remains today. But they couldn't figure out how that radiation could escape a galaxy. Until now.

Jordan Zastrow, a doctoral astronomy student, and Sally Oey, a U-M astronomy professor, observed and imaged the relatively nearby NGC 5253, a dwarf starburst galaxy in the southern constellation Centaurus. Starburst galaxies, as their name implies, are undergoing a burst of intense star formation. While rare today, scientists believe they were very common in the early universe.

The researchers used special filters to see where and how the galaxy's extreme ultraviolet radiation, or UV light, was interacting with nearby gas. They found that the UV light is, indeed, evaporating gas in the interstellar medium. And it is doing so along a narrow cone emanating from the galaxy.

A paper on their work is published Oct. 12 in Astrophysical Journal Letters.

"We are not directly seeing the ultraviolet light. We are seeing its signature in the gas around the galaxy," Zastrow said.

In starburst galaxies, a superwind from these massive stars can clear a passageway through the gas in the galaxy, allowing the radiation to escape, the researchers said.

The shape of the cone they observed could help explain why similar processes in other galaxies have been difficult to detect.

"This feature is relatively narrow. The opening that is letting the UV light out is small, which makes this light challenging to detect. We can think of it as a lighthouse. If the lamp is pointed toward you, you can see the light. If it's pointed away from you, you can't see it," Zastrow said. "We believe the orientation of the galaxy is important as to whether we can detect escaping UV radiation."

The findings could help astronomers understand how the earliest galaxies affected the universe around them.

Also contributing were researchers from the University of Maryland, MIT's Kavli Institute for Astrophysics and Space Research, and the University of California, Berkeley. The research is funded by the National Science Foundation. Observations were conducted with the Magellan Telescopes at Las Campanas Observatory in Chile.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Michigan.

Journal Reference:

Jordan Zastrow, M. S. Oey, Sylvain Veilleux, Michael McDonald, Crystal L. Martin. An ionization cone in the dwarf starburst galaxy NGC 5253. The Astrophysical Journal, 2011; 741 (1): L17 DOI: 10.1088/2041-8205/741/1/L17

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Cosmic weight watching reveals black hole-galaxy history

ScienceDaily (Sep. 29, 2011) — Using state-of-the-art technology and sophisticated data analysis tools, a team of astronomers from the Max Planck Institute for Astronomy has developed a new and powerful technique to directly determine the mass of an active galaxy at a distance of nearly 9 billion light-years from Earth. This pioneering method promises a new approach for studying the co-evolution of galaxies and their central black holes. First results indicate that for galaxies, the best part of cosmic history was not a time of sweeping changes.

One of the most intriguing developments in astronomy over the last few decades is the realization that not only do most galaxies contain central black holes of gigantic size, but also that the mass of these central black holes are directly related to the mass of their host galaxies. This correlation is predicted by the current standard model of galaxy evolution, the so-called hierarchical model, as astronomers from the Max Planck Institute for Astronomy have recently shown.

When astronomers look out to greater and greater distances, they look further and further into the past. Investigating this black hole-galaxy mass correlation at different distances, and thus at different times in cosmic history, allows astronomers to study galaxy and black hole evolution in action.

For galaxies further away than 5 billion light-years (corresponding to a redshift of z > 0.5), such studies face considerable difficulties. The typical objects of study are so-called active galaxies, and there are well-established methods to estimate the mass of such a galaxy's central black hole. It is the galaxy's mass itself that is the challenge: At such distances, standard methods of estimating a galaxy's mass become exceedingly uncertain or fail altogether.

Now, a team of astronomers from the Max Planck Institute for Astronomy, led by Dr Katherine Inskip, has, for the first time, succeeded in directly "weighing" both a galaxy and its central black hole at such a great distance using a sophisticated and novel method. The galaxy, known to astronomers by the number J090543.56+043347.3 (which encodes the galaxy's position in the sky) has a distance of 8.8 billion light-years from Earth (redshift z = 1.3).

The astronomers succeeded in measuring directly the so-called dynamical mass of this active galaxy. The key idea is the following: A galaxy's stars and gas clouds orbit the galactic centre; for instance, our Sun orbits the centre of the Milky Way galaxy once every 250 million years. The stars' different orbital speeds are a direct function of the galaxy's mass distribution. Determine orbital speeds and you can determine the galaxy's total mass.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Max-Planck-Gesellschaft.

Journal Reference:

K. J. Inskip, K. Jahnke, H.-W. Rix, G. van de Ven. Resolving the Dynamical Mass of a z ~ 1.3 Quasi-stellar Object Host Galaxy Using SINFONI and Laser Guide Star Assisted Adaptive Optics. The Astrophysical Journal, 2011; 739 (2): 90 DOI: 10.1088/0004-637X/739/2/90

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Cosmic weight watching reveals black hole-galaxy history

ScienceDaily (Sep. 29, 2011) — Using state-of-the-art technology and sophisticated data analysis tools, a team of astronomers from the Max Planck Institute for Astronomy has developed a new and powerful technique to directly determine the mass of an active galaxy at a distance of nearly 9 billion light-years from Earth. This pioneering method promises a new approach for studying the co-evolution of galaxies and their central black holes. First results indicate that for galaxies, the best part of cosmic history was not a time of sweeping changes.

One of the most intriguing developments in astronomy over the last few decades is the realization that not only do most galaxies contain central black holes of gigantic size, but also that the mass of these central black holes are directly related to the mass of their host galaxies. This correlation is predicted by the current standard model of galaxy evolution, the so-called hierarchical model, as astronomers from the Max Planck Institute for Astronomy have recently shown.

When astronomers look out to greater and greater distances, they look further and further into the past. Investigating this black hole-galaxy mass correlation at different distances, and thus at different times in cosmic history, allows astronomers to study galaxy and black hole evolution in action.

For galaxies further away than 5 billion light-years (corresponding to a redshift of z > 0.5), such studies face considerable difficulties. The typical objects of study are so-called active galaxies, and there are well-established methods to estimate the mass of such a galaxy's central black hole. It is the galaxy's mass itself that is the challenge: At such distances, standard methods of estimating a galaxy's mass become exceedingly uncertain or fail altogether.

Now, a team of astronomers from the Max Planck Institute for Astronomy, led by Dr Katherine Inskip, has, for the first time, succeeded in directly "weighing" both a galaxy and its central black hole at such a great distance using a sophisticated and novel method. The galaxy, known to astronomers by the number J090543.56+043347.3 (which encodes the galaxy's position in the sky) has a distance of 8.8 billion light-years from Earth (redshift z = 1.3).

The astronomers succeeded in measuring directly the so-called dynamical mass of this active galaxy. The key idea is the following: A galaxy's stars and gas clouds orbit the galactic centre; for instance, our Sun orbits the centre of the Milky Way galaxy once every 250 million years. The stars' different orbital speeds are a direct function of the galaxy's mass distribution. Determine orbital speeds and you can determine the galaxy's total mass.

Recommend this story on Facebook, Twitter,
and Google +1:

Other bookmarking and sharing tools:

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Max-Planck-Gesellschaft.

Journal Reference:

K. J. Inskip, K. Jahnke, H.-W. Rix, G. van de Ven. Resolving the Dynamical Mass of a z ~ 1.3 Quasi-stellar Object Host Galaxy Using SINFONI and Laser Guide Star Assisted Adaptive Optics. The Astrophysical Journal, 2011; 739 (2): 90 DOI: 10.1088/0004-637X/739/2/90

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

Astronomers reveal a cosmic 'axis of evil'

ScienceDaily (June 30, 2011) — Astronomers are puzzled by the announcement that the masses of the largest objects in the universe appear to depend on which method is used to weigh them. The new work was presented at a specialist discussion meeting on 'Scaling Relations of Galaxy Clusters' organised by the Astrophysics Research Institute (ARI) at Liverpool John Moores University and supported by the Royal Astronomical Society.

Clusters of galaxies are the largest gravitationally bound objects in the universe containing thousands of galaxies like the Milky Way and their weight is an important probe of their dark matter content and evolution through cosmic time. Measurements used to weigh these systems carried out in three different regions of the electromagnetic spectrum: X-ray, optical and millimetre wavelengths, give rise to significantly different results.

Eduardo Rozo, from the University of Chicago, explained that any two of the measurements can be made to fit easily enough but that always leaves the estimate using the third technique out of line. Dubbed the 'Axis of Evil', it is as if the universe is being difficult by keeping back one or two pieces of the jigsaw and so deliberately preventing us from calibrating our weighing scales properly.

More than 40 of the leading cluster astronomers from UK, Europe and the US attended the meeting to discuss the early results from the Planck satellite, currently scanning the heavens at millimetre wavelengths, looking for the smallest signals from clusters of galaxies and the cosmic background radiation in order to understand the birth of the universe. The Planck measurements were compared with optical images of clusters from the Sloan Digitised Sky Survey and new X-ray observations from the XMM-Newton satellite.

ARI astronomers are taking a leading role in this research through participation in the X-ray cluster work and observations of the constituent galaxies using the largest ground-based optical telescopes.

One possible resolution to the 'Axis of Evil' problem discussed at the meeting is a new population of clusters which is optically bright but also X-ray faint. Dr Jim Bartlett (Univ. Paris), who is one of the astronomers who presented the Planck results, argued that the prospect of a new cluster population which responds differently was a 'frightening prospect' because it overturns age old ideas about the gravitational physics being the same from cluster to cluster.

Chris Collins, LJMU Professor of Cosmology, who organised the meeting said: 'I saw this meeting as an opportunity to bring together experts who study clusters at only one wavelength and don't always talk to their colleagues working at other wavelengths. The results presented are unexpected and all three communities (optical, X-ray and millimetre) will need to work together in the future to figure out what is going on.'

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Royal Astronomical Society (RAS).

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

An Alice-in-Wonderland universe? Physicist discovers an apparent cosmic parity violation

ScienceDaily (June 10, 2011) — Does our universe have mirror symmetry? That is the question Prof. Michael Longo of the University of Michigan's Physics Department asked. The answer could perhaps be found by studying the rotation directions of spiral galaxies.

Physicists and astronomers have always assumed that the Universe has this symmetry. To test this, Longo and his team of five undergraduates used data from the Sloan Digital Sky Survey to study the rotation directions of spiral galaxies. The mirror image of a counter-clockwise rotating galaxy, like the example, would have clockwise rotation. An excess of one type over the other would be evidence for a breakdown of mirror symmetry, or, in physics speak, a "parity violation" on cosmic scales.

Longo and his team, after studying tens of thousands of spiral galaxies, found an excess of left-handed spirals in the part of the sky toward the north pole of our galaxy, the Milky Way. The excess is small, about 7%. However, Longo estimates the chance that the excess could be a cosmic accident is something like one in a million. The effect extended out to distances over 600 million light years. Our galaxy also rotates in the same sense.

"If verified, this data would be extremely important because it is almost universally accepted that on sufficiently large scales the universe is isotropic (no special direction)," he said.

If spiral galaxies tend to have their rotation axes aligned in one direction, it means that there is also a preferred direction in the universe. This violates another tenet of astrophysics that assumes the universe has no special direction or is "isotropic."

Because the Sloan telescope is in the northern hemisphere, the data that was analyzed came mostly from the northern hemisphere of the sky. An important test of this result will be to see if there is an excess of right-handed spiral galaxies in the southern hemisphere. Longo looked at the limited sample that is available now, and found that there does seem to be more right-handed ones there. More data from the southern hemisphere will provide an important test of this result.

Longo's paper has recently been published in Physics Letters B. An anonymous referee who reviewed the paper for the journal said: "In the paper the author claims that there is a preferred handedness of spiral galaxies indicating a preferred direction in the universe. Such [a] claim, if proven true, would have a profound impact on cosmology and would very likely result in a Nobel prize."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Michigan, Physics Department.

Journal Reference:

Michael J. Longo. Detection of a dipole in the handedness of spiral galaxies with redshifts z~0.04. Physics Letters B, 2011; 699 (4): 224 DOI: 10.1016/j.physletb.2011.04.008

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here

An Alice-in-Wonderland universe? Physicist discovers an apparent cosmic parity violation

ScienceDaily (June 10, 2011) — Does our universe have mirror symmetry? That is the question Prof. Michael Longo of the University of Michigan's Physics Department asked. The answer could perhaps be found by studying the rotation directions of spiral galaxies.

Physicists and astronomers have always assumed that the Universe has this symmetry. To test this, Longo and his team of five undergraduates used data from the Sloan Digital Sky Survey to study the rotation directions of spiral galaxies. The mirror image of a counter-clockwise rotating galaxy, like the example, would have clockwise rotation. An excess of one type over the other would be evidence for a breakdown of mirror symmetry, or, in physics speak, a "parity violation" on cosmic scales.

Longo and his team, after studying tens of thousands of spiral galaxies, found an excess of left-handed spirals in the part of the sky toward the north pole of our galaxy, the Milky Way. The excess is small, about 7%. However, Longo estimates the chance that the excess could be a cosmic accident is something like one in a million. The effect extended out to distances over 600 million light years. Our galaxy also rotates in the same sense.

"If verified, this data would be extremely important because it is almost universally accepted that on sufficiently large scales the universe is isotropic (no special direction)," he said.

If spiral galaxies tend to have their rotation axes aligned in one direction, it means that there is also a preferred direction in the universe. This violates another tenet of astrophysics that assumes the universe has no special direction or is "isotropic."

Because the Sloan telescope is in the northern hemisphere, the data that was analyzed came mostly from the northern hemisphere of the sky. An important test of this result will be to see if there is an excess of right-handed spiral galaxies in the southern hemisphere. Longo looked at the limited sample that is available now, and found that there does seem to be more right-handed ones there. More data from the southern hemisphere will provide an important test of this result.

Longo's paper has recently been published in Physics Letters B. An anonymous referee who reviewed the paper for the journal said: "In the paper the author claims that there is a preferred handedness of spiral galaxies indicating a preferred direction in the universe. Such [a] claim, if proven true, would have a profound impact on cosmology and would very likely result in a Nobel prize."

Story Source:

The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Michigan, Physics Department.

Journal Reference:

Michael J. Longo. Detection of a dipole in the handedness of spiral galaxies with redshifts z~0.04. Physics Letters B, 2011; 699 (4): 224 DOI: 10.1016/j.physletb.2011.04.008

Note: If no author is given, the source is cited instead.

Disclaimer: Views expressed in this article do not necessarily reflect those of ScienceDaily or its staff.

View the original article here