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Post Info TOPIC: M106


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Messier 106
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Black Hole Fireworks in Nearby Galaxy

Celebrants this Fourth of July will enjoy the dazzling lights and booming shock waves from the explosions of fireworks. A similarly styled event is taking place in the galaxy Messier 106, as seen by NASA's Spitzer Space Telescope, Chandra X-ray Observatory and the Herschel Space Observatory. Herschel is a European Space Agency mission with important NASA contributions.
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Hungry Black Hole Spawns Bizarre Four-Armed Galaxy

Where most spiral galaxies have two twisting arms, a neighbour of the Milky Way is a four-armed monster. A new photo snapped by the Hubble Space Telescope, combined with observations by amateur astronomers, reveals these arms in stunning detail.
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RE: M106
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Title: Estimating masses of Keplerian disk systems: the case of AGN in NGC 4258
Authors: Patryk Mach, Michal Pirog, Edward Malec

The Keplerian motion of accretion disks in Active Galactic Nuclei (AGN) is usually believed to be generated by a heavy central mass. We investigate accreting disk systems with polytropic gas in Keplerian rotation and obtain a phenomenological formula that relates the Keplerian angular frequency to the ratio of disk and central masses. Central mass approaches the Keplerian value, if the inner boundary of a disk is close to the minimal stable orbit of a black hole. These results are applied to NGC 4258, the unique AGN with a finely measured Keplerian rotation curve of the central disk, with the conclusion that its rotation curve is, in fact, determined by the central black hole. The mass of the accretion disk exceeds 100 solar masses.

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NGC 4258
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Title: A Stellar Dynamical Measurement of the Black Hole Mass in the Maser Galaxy NGC 4258
Authors: Christos Siopis, Karl Gebhardt, Tod R. Lauer, John Kormendy, Jason Pinkney, Douglas Richstone, S. M. Faber, Scott Tremaine, M. C. Aller, Ralf Bender, Gary Bower, Alan Dressler, Alexei V. Filippenko, Richard Green, Luis C. Ho, John Magorrian

We determine the mass of the black hole at the centre of the spiral galaxy NGC 4258 by constructing axisymmetric dynamical models of the galaxy. These models are constrained by high spatial resolution imaging and long-slit spectroscopy of the nuclear region obtained with the Hubble Space Telescope, complemented by ground-based observations extending to larger radii. Our best mass estimate is MBH = (3.3 0.2) x 10^7 \MSun for a distance of 7.28 Mpc (statistical errors only). This is within 15% of (3.82 0.01) x 10^7 \MSun, the mass determined from the kinematics of water masers (rescaled to the same distance) assuming they are in Keplerian rotation in a warped disk. The construction of accurate dynamical models of NGC 4258 is somewhat compromised by an unresolved active nucleus and colour gradients, the latter caused by variations in the stellar population and/or obscuring dust. These problems are not present in the ~ 30 other black hole mass determinations from stellar dynamics that have been published by us and other groups; thus, the relatively close agreement between the stellar dynamical mass and the maser mass in NGC 4258 enhances our confidence in the black hole masses determined in other galaxies from stellar dynamics using similar methods and data of comparable quality.

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Title: The structure of the accretion disk in NGC 4258 derived from observations of its water vapour masers
Authors: Jim Moran, Liz Humphreys, Lincoln Greenhill, Mark Reid, Alice Argon

A wealth of new information about the structure of the maser disk in NGC 4258 has been obtained from a series of 18 VLBA observations spanning three years, as well as from 32 additional epochs of spectral monitoring data from 1994 to the present, acquired with the VLA, Effelsberg, and GBT. The warp of the disk has been defined precisely. The thickness of the maser disk has been measured to be 12 microarcseconds (FWHM), which is slightly smaller than previously quoted upper limits. Under the assumption that the masers trace the true vertical distribution of material in the disk, from the condition of hydrostatic equilibrium the sound speed is 1.5 km/s, corresponding to a thermal temperature of 600K. The accelerations of the high velocity maser components have been accurately measured for many features on both the blue and red side of the spectrum. The azimuthal offsets of these masers from the midline (the line through the disk in the plane of the sky) and derived projected offsets from the midline based on the warp model correspond well with the measured offsets. This result suggests that the masers are well described as discrete clumps of masing gas, which accurately trace the Keplerian motion of the disk. However, we have continued to search for evidence of apparent motions caused by ''phase effects.'' This work provides the foundation for refining the estimate of the distance to NGC 4258 through measurements of feature acceleration and proper motion. The refined estimate of this distance is expected to be announced in the near future.

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Chandra X-ray Image of NGC 4258
NGC 4258 is a spiral galaxy about 25 million light years from Earth, also known as M106. The Chandra image of NGC 4258 reveals the so-called anomalous arms. These mysterious structures are due to shock waves generated by the supermassive black hole in the nucleus of the galaxy.

ngc4258_x
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Credit: NASA/CXC/Univ. of Maryland/A.S. Wilson et al.

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Mystery Spiral Arms Explained?
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Using a quartet of space observatories, University of Maryland astronomers may have cracked a 45-year mystery surrounding two ghostly spiral arms in the galaxy M106.
The Maryland team, led by Yuxuan Yang, took advantage of the unique capabilities of NASA's Chandra X-ray Observatory, NASA's Spitzer Space Telescope, the European Space Agency's XMM-Newton X-ray observatory, and data obtained almost a decade ago with NASA's Hubble Space Telescope.

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Posts: 131433
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Messier 106
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Using a trio of space observatories, astronomers may have cracked a 45-year old mystery surrounding two ghostly spiral arms in the galaxy M106 (NGC 4258).
The results, obtained by a team from the University of Maryland (USA), took advantage of the unique capabilities of the European Space Agencys XMM-Newton X-ray observatory, NASAs Chandra X-ray Observatory, and NASAs Spitzer Space Telescope.
M106 (also known as NGC 4258) is a spiral galaxy 23.5 million light-years away, in the constellation Canes Venatici. In visible-light images, two prominent arms emanate from the bright nucleus and spiral outward. These arms are dominated by young, bright stars, which light up the gas within the arms.

"But in radio and X-ray images, two additional spiral arms dominate the picture, appearing as ghostly apparitions between the main arms" - team member Andrew Wilson of the University of Maryland.
These so-called "anomalous arms" consist mostly of gas.

"The nature of these anomalous arms is a long-standing puzzle in astronomy. They have been a mystery since they were first discovered in the early 1960s" - Yuxuan Yang, lead author of the team.

M106
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Credits: NASA/CXC/Univ. of Maryland/A.S. Wilson et al. Optical: Pal.Obs. DSS; IR: NASA/JPL-Caltech; VLA & NRAO/AUI/NSF

By analysing data from XMM-Newton, Spitzer, and Chandra, the team in Maryland have confirmed earlier suspicions that the ghostly arms represent regions of gas that are being violently heated by shock waves.
It has been previously suggested that the anomalous arms are jets of particles being ejected by a supermassive black hole in M106s nucleus. But radio observations at the Very Large Array in New Mexico later identified another pair of jets originating in the core.

"It is highly unlikely that an active galactic nucleus could have more than one pair of jets" - Yuxuan Yang.

In 2001, another team of astronomers at the University of North Carolina (USA), noted that the two jets are tipped 30 degrees with respect to the disk. But if one could vertically project the jets onto the disk, they would line up almost perfectly with the anomalous arms. Figuring that this alignment was not strictly a matter of chance, the team proposed that the jets heat the gas in their line of travel, forming an expanding cocoon. Because the jets lie close to M106s disk, the cocoon heats gas in the disk and generates shock waves, heating the gas to millions of degrees and causing it to radiate brightly in X-rays and other wavelengths.
To test this idea, Yang and his colleagues looked at archival spectral observations from XMM-Newton. With XMM-Newtons superb sensitivity, the team could measure the gas temperature in the anomalous arms and also see how X-rays from the gas are absorbed en route by intervening material.

"One of the predictions of this scenario is that the anomalous arms will gradually be pushed out of the galactic disk plane by jet-heated gas" - Yuxuan Yang.

The XMM-Newton spectra show that X-rays are absorbed more strongly in the direction of the northwest arm than in the southeast arm. The results strongly suggest that the southeast arm is partly on the near side of M106s disk, and the northwest arm is partly on the far side.
The scientists noted that these observations show clear consistency with their scenario. Confirmation of this interpretation has recently come from archival observations from NASAs Spitzer Space Telescope, whose infrared view shows clear signs that X-ray emission from the northwest arm is being absorbed by warm gas and dust in the galaxys disk. Moreover, Chandras superior imaging resolution gives clear indications of gas shocked by interactions with the two jets.
Besides addressing the mystery of the anomalous arms, these observations allowed the team to estimate the energy in the jets and gauge their relationship to M106s central black hole.

Source ESA

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Posts: 131433
Date:
M106
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Close to Ursa Major (the Great Bear) and surrounded by the stars of Canes Venatici (the Hunting Dogs), this celestial nebula was discovered in 1781 by the French astronomer Pierre Mechain.
Later, it was added to the catalogue of his friend and colleague Charles Messier as M106.


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Modern deep telescopic views reveal it to be a spiral galaxy around 30 thousand light-years across located about 21 million light-years from the Milky Way.
Young blue star clusters and reddish stellar nurseries trace the striking spiral arms of M106.
Seen clearly in this image, the galaxy's bright core is also visible in the radio and x-rays spectrum, making M106 a nearby example of the Seyfert class of active galaxies. The bright core of a Seyfert galaxy is believed to be powered by matter falling into a massive central black hole.

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