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Post Info TOPIC: NGC1068, M77


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Messier 77
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Title: Herschel-PACS Observations of Far-IR CO Line Emission in NGC 1068: Highly Excited Molecular Gas in the Circumnuclear Disk
Authors: S. Hailey-Dunsheath, E. Sturm, J. Fischer, A. Sternberg, J. Graciá-Carpio, R. Davies, E. González-Alfonso, D. Mark, A. Poglitsch, A. Contursi, R. Genzel, D. Lutz, L. Tacconi, S. Veilleux, A. Verma, J. A. de Jong

We report the detection of far-IR CO rotational emission from the prototypical Seyfert 2 galaxy NGC 1068. Using Herschel-PACS, we have detected 10 transitions in the J_upper=14-24 (E_upper/k_B = 580-1656 K) range, all of which are consistent with arising from within the central 10" (700 pc). The detected transitions are modelled as arising from 2 different components: a moderate excitation (ME) component close to the galaxy systemic velocity, and a high excitation (HE) component that is blueshifted by ~70 km s^{-1}. We employ a large velocity gradient (LVG) model and derive n_H2~10^{5.7} cm^{-3}, T_kin~150 K, and M_H2~10^{6.9} M_sun for the ME component, and n_H2~10^{6.3} cm^{-3}, T_kin~440 K, and M_H2~10^{5.8} M_sun for the HE component, although for both components the uncertainties in the density and mass are ~plus/minus 1 dex. Both components arise from denser and possibly warmer gas than traced by low-J CO transitions, and the ME component likely makes a significant contribution to the mass budget in the nuclear region. We compare the CO line profiles with those of other molecular tracers observed at higher spatial and spectral resolution, and find that the ME transitions are consistent with these lines arising in the ~200 pc diameter ring of material traced by H_2 1-0 S(1) observations. The blueshift of the HE lines may also be consistent with the bluest regions of this H_2 ring, but a better kinematic match is found with a clump of infalling gas ~40 pc north of the AGN. We consider potential heating mechanisms, and conclude that X-ray or shock heating of both components is viable, while far-UV heating is unlikely. We also report sensitive upper limits extending up to J_upper=50, which place constraints on the emission from the X-ray obscuring medium.

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Posts: 130035
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NGC 1068
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Title: Chemical complexity in NGC1068
Authors: Rebeca Aladro, Serena Viti, Denise Riquelme, Sergio Martin, Rainer Mauersberger, Jesus Martin-Pintado, Estelle Bayet

We aimed to study the chemistry of the circumnuclear molecular gas of NGC1068, and to compare it with those of the starburst galaxies M82 and NGC253. Using the IRAM-30m telescope, we observed the inner 2 kpc of NGC1068 between 86.2 GHz and 115.6 GHz. We identified 35 spectral features, corresponding to 24 different molecular species. Among them, HC3N, SO, N2H+, CH3CN, NS, 13CN, and HN13C are detected for the first time in NGC1068. Assuming local thermodynamic equilibrium (LTE), we calculated the column densities of the detected molecules, as well as the upper limits to the column densities of some undetected species. The comparison among the chemistries of NGC1068, M82, and NGC253, suggests that, apart from X-rays, shocks also determine the chemistry of NGC1068. We propose the column density ratio between CH3CCH and HC3N as a prime indicator of the imprints of starburst and AGN environments in the circumnuclear interstellar medium. This ratio is, at least, 64 times larger in M82 than in NGC1068, and, at least, 4 times larger in NGC253 than in NGC1068. Finally, we used the UCL_CHEM and UCL_PDR chemical codes to constrain the origin of the species, as well as to test the influence of UV radiation fields and cosmic rays on the observed abundances.

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RE: NGC1068, M77
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Title: Interferometric CO(3-2) Observations toward the Central Region of NGC 1068
Authors: Mengchun Tsai (1), Chorng-Yuan Hwang (1), Satoki Matsu****a (2 and 3), Andrew J. Baker (4), Daniel Espada (5 and 6 and 2) ((1) Institute of Astronomy, National Central University, Taiwan, R.O.C., (2) Academia Sinica Institute of Astronomy and Astrophysics, Taipei, Taiwan, R.O.C., (3) Academia Sinica Institute of Astronomy and Astrophysics, Joint ALMA Office, Las Condes, Santiago, Chile, (4) Department of Physics and Astronomy, Rutgers, the State University of New Jersey, Piscataway, NJ, (5) Instituto de Astrofísica de Andalucía - CSIC, Granada, Spain, (6) Harvard-Smithsonian Centre for Astrophysics, Cambridge, MA)

We present CO(3-2) interferometric observations of the central region of the Seyfert 2 galaxy NGC 1068 using the Submillimeter Array, together with CO(1-0) data taken with the Owens Valley Radio Observatory Millimeter Array. Both the CO(3-2) and CO(1-0) emission lines are mainly distributed within ~5 arcsec of the nucleus and along the spiral arms, but the intensity distributions show differences; the CO(3-2) map peaks in the nucleus, while the CO(1-0) emission is mainly located along the spiral arms. The CO(3-2)/CO(1-0) ratio is about 3.1 in the nucleus, which is four times as large as the average line ratio in the spiral arms, suggesting that the molecular gas there must be affected by the radiation arising from the AGN. On the other hand, the line ratios in the spiral arms vary over a wide range from 0.24 to 2.34 with a average value around 0.75, which is similar to the line ratios of star-formation regions, indicating that the molecular gas is affected by star formation. Besides, we see a tight correlation between CO(3-2)/(1-0) ratios in the spiral arms and star formation rate surface densities derived from Spitzer 8 {\mu}m dust flux densities. We also compare the CO(3-2)/(1-0) ratio and the star formation rate at different positions within the spiral arms; both are found to decrease as the radius from the nucleus increases.

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NGC1068-1.jpg

This is a composite image of NGC 1068, one of the nearest and brightest galaxies containing a rapidly growing supermassive black hole. X-ray data from the Chandra X-ray Observatory are shown in red, optical data from the Hubble Space Telescope in green and radio data from the Very Large Array in blue. The spiral structure of NGC 1068 is shown by the X-ray and optical data, and a jet powered by the central supermassive black hole is shown by the radio data.
The X-ray images and spectra obtained using Chandra's High Energy Transmission Grating Spectrometer show that a strong wind is being driven away from the centre of NGC 1068 at a rate of about a million miles per hour. This wind is likely generated as surrounding gas is accelerated and heated as it swirls toward the black hole. A portion of the gas is pulled into the black hole, but some of it is blown away. High energy X-rays produced by the gas near the black hole heat the ouflowing gas, causing it to glow at lower X-ray energies.

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Astronomers from the University of Georgia have discovered a startling absence of hot gas being given off by the "disk" of the spiral galaxy NGC 1068. The galaxy is younger than the Milky Way and could thus offer insights into the formation of our own galaxy.

"In many ways, NGC 1068 is a window on our past. What we've found is that the process of heating gas in this galaxy is more complex that we had expected" - Robin Shelton, leader of the research.

The researchers used the FUSE satellite to plot out the emission of ionised oxygen-6 (O VI) and see how much hot gas was in the disk of 1068.

"Oxygen-6 is a tracer of hot gas, so examining it tells us a lot about how much gas is in these galaxies" - Robin Shelton.

The research was presented this week at the 208th Annual Meeting of the American Astronomical Society in Calgary, Alberta, Canada. Also assisting in the research, which was presented in a poster session, was UGA doctoral student Shinya Miyake.

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Title: Distribution of dust clouds around the central engine of NGC 1068
Authors: Daigo Tomono, Hiroshi Terada, Naoto Kobayashi

Researchers studied the distribution of dust clouds around the central engine of NGC 1068 based on shifted-and-added 8.8 - 12.3 micron (MIR) multi-filter images and 3.0 - 3.9-micron (L-band) spectra obtained with the Subaru Telescope.
In a region of 100 pc (1.4") around the central peak, they successfully constructed maps of colour temperatures and emissivities of the MIR and L-band continua as well as the 9.7 micron and 3.4 micron dust features with spatial resolutions of 26 pc (0.37") in the MIR and 22 pc (0.3") in the L-band. Their main results are:
1) colour temperature of the MIR continuum scatters around the thermal equilibrium temperature with the central engine as the heat source while that of the L-band continuum is higher and independent upon distance from the central engine;
2) the peak of the 9.7 micron silicate absorption feature is shifted to a longer wavelength at some locations;
3) the ratio of the optical depths of the dust features is different from the Galactic values and show complicated spatial distribution; and
4) there is a pie shaped warm dust cloud as an enhancement in the emissivity of the MIR continuum extending about 50 pc to the north from the central engine.
They speculate that material falls into the central engine through this cloud.

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Posts: 130035
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NGC1068
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The Seyfert galaxy NGC 1068 (M-77) is located about 60 million light years away in the constellation Cetus, making it the closest and best-studied example of an active galactic nucleus (AGN). An AGN emits copious amounts of energy from its nucleus, from very energetic x-rays to long wavelength radio waves. In addition to the intense radiation field, the nucleus of NGC 1068 contains a large amount of highly ionised and fast moving gas. In fact, some of the gas has been measured moving at up to several thousand kilometres per second.
The accepted view is that the high-energy photons and high speed of the gases are generated in the vicinity of a massive black hole at the very centre of the galaxy which is thought to have a mass of several million times that of the Sun. Studying the properties of gas and hot dust in such environment is a powerful approach to understanding the nature and evolution of massive black holes.


Position(2000): RA: 02h 42m 40.2s Dec: -00°00'48"

Two upcoming papers based on optical and mid-infrared data from the Gemini North telescope focus on the dynamic core of the magnitude 9.6 spiral galaxy NGC 1068. Described here are summaries of these papers.

Mid-infrared View of the Environment Surrounding NGC 1068’s Central Black Hole

Rachel Mason (Cerro Tololo Inter-American Observatory, NOAO) and her United States/Gemini staff team used MICHELLE, the mid-infrared imager and spectrometer at the 8-meter Gemini North telescope, to obtain deep 10 micron spectra of the nucleus and central ionisation cones of NGC 1068. The superb spatial resolution of the MICHELLE spectra, ~0.4 arcseconds or 30 parsecs at NGC 1068, let the team investigate the close environment of the central back hole on much finer scales than previous work. This allowed Mason et al. to discover that the mid-infrared emission from NGC 1068 originates in two distinct components:

1. Emission from the central region (within a diameter of 0.4 arcseconds) is dominated by the infrared-bright obscuring torus. This region is unresolved in the Gemini data, which is consistent with the compact (~3 parsec) size determined by mid-infrared interferometry.

2. At larger scales, the mid-infrared flux is dominated by diffuse emission from the AGN-heated dust within the ionisation cones. Since the areas within the ionisation cones are relatively devoid of material, they have a direct line of sight to the black hole itself. This means that the radiation emitted by the black hole can directly heat the dust present along the inner walls of the cones. The dust absorbs the high-energy photons from the central engine and then re-radiates them in the mid-infrared.

The most striking aspect of the mid-infrared data is the variation in the shape of the spectra (slope of the continuum and strength of the silicate feature and fine structure line fluxes) over small distances. There is significant structure in the dust in the circumnuclear regions even on subarcsecond scales. The 9.7-micron silicate feature appears to be present in the cone.

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Optical probing of the jet of gas and of stellar velocities

Joris Gerssen (University of Durham) and his United Kingdom/Gemini staff team used the GMOS-North integral field unit (IFU) to map the velocities of the ionised gas and stars in the central region of NGC 1068 at optical wavelengths. The resulting datacube is rich in complex features, particularly in the morphology of the (O III) doublet and the H-beta line. To interpret the observed structure in the lines the authors constructed an atlas of velocity components by Gaussian fitting of each line.


The top panels (each covering an area of 10.3 x 7.3 arcseconds) show a series of one-Angstrom wide wavelength slices through the data across the (OIII) 500.7-nanometer line of doubly ionised oxygen. Across this line the central morphology of NGC 1068 develops various subcomponents corresponding to different velocities. Lower panels show a similar “movie” across the H-beta 486.1 nanometer line of hydrogen.

The atlas contains many features that cannot be readily associated with physical structures in the nucleus; however, some components are likely associated with the expected biconic outflow. Both the H-beta 468.1 nanometer line of hydrogen and the (OIII) 500.7 nanometer line of ionised oxygen are very broad, indicative of velocities between 1000 to 2000 kilometres per second. Centroids of the radial velocity of the gas range from –1000 to 0 kilometres per second over the spatial extent of the jet . Both the gas and stellar data present a very rich and complex morphology. Indeed, a third set of distinct features found in the datacube are suggestive of distinct high-velocity gas flows and a large disk-like structure.


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Additionally the stellar kinematics of the nuclear region were mapped through the detection of the Mg b absorption line feature in the GMOS spectra. The resulting position angle and kinematic axis in the GMOS velocity map is consistent with previously published data on the motions of carbon monoxide in the same region.

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Posts: 130035
Date:
NGC1068, M77
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Title: Mid-infrared imaging of NGC1068 with VISIR at the VLT
Authors: E. Galliano, E. Pantin, D. Alloin, P.O. Lagage


High resolution mid-infrared (MIR) images of the central region of NGC1068 (M77) have been obtained with VISIR, the multi-mode MIR instrument recently installed at the ESO/VLT on Paranal.
A map of the emission at 12.8mic with increased sensitivity over the central 8"x 8" area is shown. It shows a central core (unresolved along the E-W direction) and an extended emission which draws a spiral pattern similar to that observed on near-infrared images.



Patches of MIR emission can be detected up to a distance of 4" from the core. The deconvolved 12.8mic map is fully consistent with previous high-resolution MIR observations.
It highlights the structure of the extended emission, already seen on the un-deconvolved image, and allows to identify a set of mid-infrared sources: 7 in the NE quadrant and 5 in the SW quadrant. The MIR emission map is compared with those obtained at comparable angular resolution in the near-infrared and in the (OIII) line emission.

The very good correlation between the VISIR map and the HST optical map supports the idea that the MIR emission not associated with the torus arises from dust associated with the narrow line region clouds.
The N-S extension of the MIR core (0.44") is then probably simply due to the mixing of the MIR emission from the dusty torus and the MIR emission from NLR cloud B, located only 0.1" to the North.

http://www.sc.eso.org/~egallian/VISIR/
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Pierre Méchain discovered this object on October 29, 1780, which he described as a nebula.
Charles Messier included it as No. 77 in his catalogue on December 17, 1780.
M77 can be easily found 0.7 degrees ESE from the 4-th mag star Delta Ceti.
M77 is the largest member of a small group of galaxies, which includes spiral galaxies NGCs 1055 and 1073, as well as five small irregular galaxies. NGCs 1087, 1090, and 1094 appear close to M-77, but they are background galaxies.
M77 is about 60 million light years distant, and is receding from us at about 1100 km/sec.


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An optical image (in red) shows the spiral structure across NGC 1068's inner 7 thousand light-years with an x-ray image overlaid in blue and green. A hot wind of gas streaming from the galaxy's core is seen as the broad swath of x-ray emission while material lit up by the hidden black hole source is within the central cloud of more intense x-rays.


• M-77, NGC 1068
• Magnitude: 9.6
• Constellation: Cetus
• RA: 02h 42m 40.2s
• Dec: -00°00'48" Epoch 2000
• Size (mins): 7.0' x 5.9'
• Distance: 60 million light years
• Classification: (R)SAB(rs)ab sy2
Outer Ring, Mixed Barred/Non-barred Spiral, Mixed Inner Ring - S-Shaped; Seyfert type II



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