Twists and turns in interacting galaxies

Oct 08, 2012
Twists and turns in interacting galaxies
A computer simulation of two colliding galaxies seen here at one early evolutionary stage, showing some of the twists and warps that typically develop and introduce misalignments between a host galaxy and its black hole nucleus. Credit: Hopkins 2012

(Phys.org)—Almost thirty years ago the Infrared Astronomy Satellite, IRAS, discovered that the universe contained many fabulously luminous galaxies, some of them more than a thousand times brighter than our own galaxy, but which are practically invisible at optical wavelengths. The reason for their optical dimness is that their bright light comes not from stars, which can be seen in the visible, but from dust that is warmed by bursts of star formation to temperatures of about 70 kelvin (about 200 degrees below zero Celsius) where infrared radiation predominates. Luminous galaxies not only shed light on how galaxies evolve and form stars, they act as lanterns that can be seen across cosmological distances, thereby helping scientists study the relatively early universe.

The IRAS galaxies are luminous because they contain so much of this warm dust. Astronomers suspect that most of them have been involved in collisional encounters that stimulated vigorous star formation, as gravitational effects induce interstellar gas to condense into stars. The issue for astronomers is how to confirm and refine these general conclusions. CfA astronomers have an active research effort that uses computer simulations of to calculate the luminosity of these systems, to uncover how their luminosity evolves with time, and to determine the specific contribution of starburst activity to the infrared emission.

A new paper by CfA astronomers Lars Hernquist and Chris Hayward and two of their colleagues looks carefully at the ways in which can distort the shapes of the galaxies involved, including the shapes and orientations of the regions around their central black holes. They compare the orientation of the nuclei (as measured by disks and outflowing jets) with the large-scale orientations of the . In their , they report finding only weak correlations between these alignments. It turns out that misalignments can easily be introduced as giant clumps of material fall into the region of the black hole and alter its spin, or more gradually as twists develop and evolve in the gas of the spinning galaxy. Their conclusion is in excellent agreement with the observational data, namely, that there is a poor correlation between the orientation of the spin axis of a host galaxy and of its black hole nucleus. The results will help shed light on a range of related issues, including how infalling gas in a galaxy can efficiently feed its black hole, and whether light from the nuclear region is likely to be obscured by viewing through the galaxy's disk of material.

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HannesAlfven
2.5 / 5 (8) Oct 08, 2012
Re: "The reason for their optical dimness is that their bright light comes not from stars, which can be seen in the visible, but from dust that is warmed by bursts of star formation to temperatures of about 70 kelvin (about 200 degrees below zero Celsius) where infrared radiation predominates."

It would be wise to think carefully about this inference. After all, Gerrit Verschuur has claimed to observe critical ionization velocities associated with "knots" within these interstellar filaments. CIV's are what one gets when charged particles are slammed into neutral gases. These are redshifts which can only result from electrical currents.

We know from Mr Wizard cooking a hot dog from an electrical outlet that passing an electric current can heat things up. In science, we call this electric joule heating. Electric joule heating is possibly an overlooked phenomenon in the space and Earth sciences. The phenomenon is not even included in our global warming models.
hemitite
not rated yet Oct 08, 2012
I wonder if perhaps there is a tendency for a central BH to re align with its galaxy's rotational plane where most of the mass falling into it would likely originate.
Shinobiwan Kenobi
1 / 5 (1) Oct 09, 2012
I wonder if perhaps there is a tendency for a central BH to re align with its galaxy's rotational plane where most of the mass falling into it would likely originate.


Too bad imaging BHs is so problematic; they could start looking for answers to your question by looking at galaxies that have merged, I imagine central BHs falling into one another would affect the rotational axis of the remaining BH, it would be interesting to see how they align with the plane of the galaxy in which they reside