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Post Info TOPIC: NGC1068, M77


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Messier 77
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Dazzling Spiral with an Active Heart

ESO's Very Large Telescope (VLT) has captured a magnificent face-on view of the barred spiral galaxy Messier 77. The image does justice to the galaxy's beauty, showcasing its glittering arms criss-crossed with dust lanes - but it fails to betray Messier 77's turbulent nature.
This picturesque spiral galaxy appears to be tranquil, but there is more to it than meets the eye. Messier 77 (also known as NGC 1068) is one of the closest active galaxies, which are some of the most energetic and spectacular objects in the Universe. Their nuclei are often bright enough to outshine the whole of the rest of the galaxy. Active galaxies are among the brightest objects in the Universe and emit light at most, if not all, wavelengths, from gamma rays and X-rays all the way to microwaves and radiowaves. Messier 77 is further classified as a Type II Seyfert galaxy, characterised by being particularly bright at infrared wavelengths.
 
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Posts: 129912
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NGC 1068
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Title: Near-Infrared Polarimetric Adaptive Optics Observations of NGC 1068: A torus created by a hydromagnetic outflow wind
Author: E. Lopez-Rodriguez, C. Packham, T. J. Jones, R. Nikutta, L. McMaster, R. E. Mason, M. Elvis, D. Shenoy, A. Alonso-Herrero, E. Ramirez, O. Gonzalez Martin, S. F. Hoenig, N. A. Levenson, C. Ramos Almeida, E. Perlman

We present J' and K' imaging linear polarimetric adaptive optics observations of NGC 1068 using MMT-Pol on the 6.5-m MMT. These observations allow us to study the torus from a magnetohydrodynamical (MHD) framework. In a 0.5" (30 pc) aperture at K', we find that polarisation arising from the passage of radiation from the inner edge of the torus through magnetically aligned dust grains in the clumps is the dominant polarisation mechanism, with an intrinsic polarisation of 7.0%±2.2%. This result yields a torus magnetic field strength in the range of 4-82 mG through paramagnetic alignment, and 139^{+11}_{-20} mG through the Chandrasekhar-Fermi method. The measured position angle (P.A.) of polarisation at K' is found to be similar to the P.A. of the obscuring dusty component at few parsec scales using infrared interferometric techniques. We show that the constant component of the magnetic field is responsible for the alignment of the dust grains, and aligned with the torus axis onto the plane of the sky. Adopting this magnetic field configuration and the physical conditions of the clumps in the MHD outflow wind model, we estimate a mass outflow rate \le 0.17 solar masses yr-1 at 0.4 pc from the central engine for those clumps showing near-infrared dichroism. The models used were able to create the torus in a timescale of \geq 105 yr with a rotational velocity of \le 1228 km s-1 at 0.4 pc. We conclude that the evolution, morphology and kinematics of the torus in NGC 1068 can be explained within a MHD framework.

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Posts: 129912
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RE: NGC1068, M77
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Title: NuSTAR Spectroscopy of Multi-Component X-ray Reflection from NGC 1068
Author: Franz E. Bauer (1,2,3,4), Patricia Arevalo (5,3), Dominic J. Walton (6), Michael J. Koss (7,8), Simonetta Puccetti (9,10), Poshak Gandhi (11), Daniel Stern (6), David M. Alexander (12), Mislav Balokovic (12), Steve E. Boggs (14), William N. Brandt (15,16), Murray Brightman (12), Finn E. Christensen (17), Andrea Comastri (18), William W. Craig (14,19), Agnese Del Moro (12), Charles J. Hailey (20), Fiona A. Harrison (12), Ryan Hickox (21), Bin Luo (15), Craig B. Markwardt (22), Andrea Marinucci (23), Giorgio Matt (23) Jane R. Rigby (22), Elizabeth Rivers (12), Cristian Saez (24), Ezequiel Treister (25,3), C. Megan Urry (26), William W. Zhang (22) ((1) PUC-Chile, (2) MAS, (3) EMBIGGEN Anillo, (4) Space Science Institute, (5) Valparaiso, (6) JPL, (7) ETH Zurich, (8) SNSF Fellow, (9) ASDC-ASI, (10) INAF-Roma, (11) Southhampton, (12) Durham, (13) Caltech, (14) SSL-Berkeley, (15) Penn State, (16) IGC-Penn State, (17) DTU Space, (18) INAF-Bologna, (19) LLNL, (20) Columbia Univ., (21) Dartmouth, (22) GSFC, (23) Universita Roma Tre, (24) UMd, (25) Concepcion, (26) Yale)

We report on observations of NGC1068 with NuSTAR, which provide the best constraints to date on its >10~keV spectral shape. We find no strong variability over the past two decades, consistent with its Compton-thick AGN classification. The combined NuSTAR, Chandra, XMM-Newton, and Swift-BAT spectral dataset offers new insights into the complex reflected emission. The critical combination of the high signal-to-noise NuSTAR data and a spatial decomposition with Chandra allow us to break several model degeneracies and greatly aid physical interpretation. When modelled as a monolithic (i.e., a single N_H) reflector, none of the common Compton-reflection models are able to match the neutral fluorescence lines and broad spectral shape of the Compton reflection. A multi-component reflector with three distinct column densities (e.g., N_H~1.5e23, 5e24, and 1e25 cm^{-2}) provides a more reasonable fit to the spectral lines and Compton hump, with near-solar Fe abundances. In this model, the higher N_H components provide the bulk of the Compton hump flux while the lower N_H component produces much of the line emission, effectively decoupling two key features of Compton reflection. We note that ~30% of the neutral Fe Kalpha line flux arises from >2" (~140 pc), implying that a significant fraction of the <10 keV reflected component arises from regions well outside of a parsec-scale torus. These results likely have ramifications for the interpretation of poorer signal-to-noise observations and/or more distant objects [Abridged].

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Posts: 129912
Date:
Cetus A
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NGC 1068 (also M77, Cetus A, Arp 37, IRAS 02401-0013, UGC 2188 and PGC 10266) is a magnitude +9.6 barred spiral galaxy located 47 million light-years away in the constellation Cetus.

The galaxy was discovered by French astronomer Pierre François André Méchain using a 15.24 cm (6 inch) speculum Newtonian reflector on the 29th October 1780.

Charles Messier also observed the galaxy in December 1780.

Position (J2000): R.A. 02h 42m 40.7s  |  Dec. -00° 00' 48"



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Posts: 129912
Date:
Messier 77
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Hubble observes the hidden depths of Messier 77

heic1305a.jpg

The NASA/ESA Hubble Space Telescope has captured this vivid image of spiral galaxy Messier 77, one of the most famous and well-studied galaxies in the sky. The patches of red across this image highlight pockets of star formation along the pinwheeling arms, with dark dust lanes stretching across the galaxy's energetic centre.
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Title: Resolving the coronal line region of NGC1068 with near infrared integral field spectroscopy
Authors: X. Mazzalay (1), A. Rodríguez-Ardila (2), S. Komossa (3), Peter J. McGregor (4) ((1) Max-Planck-Institut für extraterrestrische Physik, Garching, Germany, (2) Laboratório Nacional de Astrofísica, Brazil, (3) Max-Planck-Institut für Radioastronomie, Bonn, Germany, (4) Research School of Astronomy & Astrophysics, Australian National University, Australia)

We present AO-assisted J- and K-band integral field spectroscopy of the inner 300 x 300 pc of the Seyfert 2 galaxy NGC1068. The data were obtained with the Gemini NIFS integral field unit spectrometer, which provided us with high-spatial and -spectral resolution sampling. The wavelength range covered by the observations allowed us to study the [CaVIII], [SiVI], [SiVII], [AlIX] and [SIX] coronal-line (CL) emission, covering ionisation potentials up to 328 eV. The observations reveal very rich and complex structures, both in terms of velocity fields and emission-line ratios. The CL emission is elongated along the NE-SW direction, with the stronger emission preferentially localized to the NE of the nucleus. CLs are emitted by gas covering a wide range of velocities, with maximum blueshifts/redshifts of ~ -1600/1000 km/s. There is a trend for the gas located on the NE side of the nucleus to be blueshifted while the gas located towards the SW is redshifted. The morphology and the kinematics of the near-infrared CLs are in very good agreement with the ones displayed by low-ionisation lines and optical CLs, suggesting a common origin. The line flux distributions, velocity maps, ionisation structure (traced by the [SiVII]/[SiVI] emission-line ratio) and low ionisation emission-line ratios (i.e., [FeII]/Pa\beta\ and [FeII]/[PII]) suggest that the radio jet plays an important role in the structure of the coronal line region of this object, and possibly in its kinematics.

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Posts: 129912
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RE: NGC1068, M77
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Title: A lambda=3 mm molecular line survey of NGC1068. Chemical signatures of an AGN environment
Authors: Rebeca Aladro, Serena Viti, Estelle Bayet, Denise Riquelme, Sergio Martin, Rainer Mauersberger, Jesus Martin-Pintado, Miguel Angel Requena Torres, Carsten Kramer, Axel Weiss

We aimed to study the molecular composition of the interstellar medium (ISM) surrounding an Active Galactic Nucleus (AGN), by making an inventory of molecular species and their abundances, as well as to establish a chemical differentiation between starburst galaxies and AGN. We used the IRAM-30 m telescope to observe the central 1.5-2 kpc region of NGC1068, covering the frequencies between 86.2 GHz and 115.6 GHz. Using Boltzmann diagrams, we calculated the column densities of the detected molecules. We used a chemical model to reproduce the abundances found in the AGN, to determine the origin of each detected species, and to test the influence of UV fields, cosmic rays, and shocks on the ISM. We identified 24 different molecular species and isotopologues, among which HC3N, SO, N2H+, CH3CN, NS, 13CN, and HN13C are detected for the first time in NGC1068. We obtained the upper limits to the isotopic ratios 12C/13C=49, 16O/18O=177 and 32S/34S=5. Our chemical models suggest that the chemistry in the nucleus of NGC1068 is strongly influenced by cosmic rays, although high values of both cosmic rays and far ultraviolet (FUV) radiation fields also explain well the observations. The gas in the nucleus of NGC1068 has a different chemical composition as compared to starburst galaxies. The distinct physical processes dominating galaxy nuclei (e.g. C-shocks, UV fields, X-rays, cosmic rays) leave clear imprints in the chemistry of the gas, which allow to characterise the nucleus activity by its molecular abundances.

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Posts: 129912
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NGC1068
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Title: Submillimetre line spectrum of the Seyfert galaxy NGC1068 from the Herschel-SPIRE Fourier Transform Spectrometer
Authors: Luigi Spinoglio, Miguel Pereira-Santaella, Gemma Busquet, Maximilien R. P. Schirm, Christine D. Wilson, Jason Glenn, Julia Kamenetzky, Naseem Rangwala, Philip R. Maloney, Tara J. Parkin, George J. Bendo, Suzanne C. Madden, Mark G. Wolfire, Alessandro Boselli, Asantha Cooray, Mathew J. Page

The first complete submillimetre spectrum (190-670um) of the Seyfert 2 galaxy NGC1068 has been observed with the SPIRE Fourier Transform Spectrometer onboard the Herschel Space Observatory. The sequence of CO lines (Jup=4-13), lines from water, the fundamental rotational transition of HF, two o-H_2O+ lines and one line each from CH+ and OH+ have been detected, together with the two [CI] lines and the [NII]205um line. The observations in both single pointing mode with sparse image sampling and in mapping mode with full image sampling allow us to disentangle two molecular emission components, one due to the compact circum-nuclear disk (CND) and one from the extended region encompassing the star forming ring (SF-ring). Radiative transfer models show that the two CO components are characterised by density of n(H_2)=10^4.5 and 10^2.9 cm^-3 and temperature of T=100K and 127K, respectively. The comparison of the CO line intensities with photodissociation region (PDR) and X-ray dominated region (XDR) models, together with other observational constraints, such as the observed CO surface brightness and the radiation field, indicate that the best explanation for the CO excitation of the CND is an XDR with density of n(H_2) 10^4 cm^-3 and X-ray flux of 9 erg s^-1 cm^-2, consistent with illumination by the active galactic nucleus, while the CO lines in the SF-ring are better modelled by a PDR. The detected water transitions, together with those observed with the \her \sim PACS Spectrometer, can be modelled by an LVG model with low temperature (T_kin \sim 40K) and high density (n(H_2) in the range 10^6.7-10^7.9 cm^-3).

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Posts: 129912
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NGC 1068
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Title: The Chandra HRC View of the Sub-arcsecond Structures in the Nuclear Region of NGC 1068
Authors: Junfeng Wang, Giuseppina Fabbiano, Margarita Karovska, Martin Elvis, Guido Risaliti

We have obtained a high spatial resolution X-ray image of the nucleus of NGC 1068 using the High Resolution Camera (HRC-I) on board the Chandra X-ray Observatory, which provides an unprecedented view of the innermost 1 arcsecond radius region of this galaxy. The HRC image resolves the narrow line region into X-ray emission clumps matching bright emission-line clouds in the HST [OIII]5007 images and allows comparison with sub-arcsecond scale radio jet for the first time. Two distinct X-ray knots are revealed at 1.3-1.4 arcsecond northeast and southwest of the nucleus. Based on the combined X-ray, [OIII], and radio continuum morphology, we identify the locations of intense radio jet-cloud interaction. The [OIII] to soft X-ray ratios show that some of these clouds are strongly affected by shock heating, whereas in other locations the jet simply thrusts through with no signs of strong interaction. This is further strengthened by the presence of a kT~1 keV collisionally ionised component in the ACIS spectrum of a shock heated cloud (HST-G). We estimate that the kinematic luminosity of the jet-driven shocks is 6x10^{38} erg/s, a negligible fraction (10^{-4}) of the estimated total jet power.

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Posts: 129912
Date:
RE: NGC1068, M77
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Title: 2D mapping of young stars in the inner 180 pc of NGC 1068: correlation with molecular gas ring and stellar kinematics
Authors: Thaisa Storchi-Bergmann, Rogemar A. Riffel, Rogerio Riffel, Marlon R. Diniz, Tiberio Borges Vale, Peter J. McGregor

We report the first two-dimensional mapping of the stellar population and non-stellar continua within the inner 180 pc (radius) of NGC 1068 at a spatial resolution of 8 pc, using integral field spectroscopy in the near-infrared. We have applied the technique of spectral synthesis to data obtained with the instrument NIFS and the adaptive optics module ALTAIR at the Gemini North Telescope. Two episodes of recent star formation are found to dominate the stellar population contribution: the first occurred 300 Myr ago, extending over most of the nuclear region; the second occurred just 30 Myr ago, in a ring-like structure at ~100 pc from the nucleus, where it is coincident with an expanding ring of H2 emission. Inside the ring, where a decrease in the stellar velocity dispersion is observed, the stellar population is dominated by the 300 Myr age component. In the inner 35 pc, the oldest age component (age > 2Gyr) dominates the mass, while the flux is dominated by black-body components with temperatures in the range 700 < T < 800 K which we attribute to the dusty torus. We also find some contribution from black-body and power-law components beyond the nucleus which we attribute to dust emission and scattered light.

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