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TOPIC: NGC1275
Blobrana


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Posts: 131433
Date:
PGC 12429
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ATel 9931: VERITAS detection of the radio galaxy NGC 1275 with elevated very-high-energy gamma-ray emission



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Blobrana


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Posts: 131433
Date:
NGC 1275
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ATel 9791: The high radio fluxes from NGC1275



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Blobrana


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Posts: 131433
Date:
Caldwell 24
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ATel 9690: VERITAS detection of the radio galaxy NGC 1275 with elevated very-high-energy gamma-ray emission



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Blobrana


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Posts: 131433
Date:
Perseus A
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NGC 1275 (also Perseus A, Caldwell 24, IRAS 03164+4119, MCG 7-7-63, UGC 2669 and PGC 12429) is a magnitude +12.6 peculiar galaxy located 237 million light-years away in the constellation Perseus. 

The galaxy was discovered by British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Windsor Road, Slough on the 17th October 1786.

Position (J2000): R.A. 03h 19m 48.1s  |  Dec. +41° 30' 42"

NGC 1275 corresponds to the radio galaxy Perseus A and is situated near the center of the large Perseus Cluster of galaxies.
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Blobrana


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Posts: 131433
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RE: NGC1275
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Title: A Non-thermal Study of the Brightest Cluster Galaxy NGC 1275 - The Gamma-Radio Connection Over Four Decades
Author: K. L. Dutson, A. C. Edge, J. A. Hinton, M. T. Hogan, M. A. Gurwell, W. N. Alston

Emission from the active nucleus in the core of the brightest cluster galaxy of the Perseus cluster, NGC 1275, has varied dramatically over the past four decades. Prompted by the Fermi detection of flaring in the gamma-ray band, we present the recent increased activity of this source in the context of its past radio and gamma-ray output. The broad correspondence between the high-frequency radio data and the high-energy (HE) emission is striking. However, on short timescales this correlation breaks down and the 1.3 mm Submillimeter Array flux is apparently unaffected during Fermi-detected flaring activity. The fact that NGC 1275 is also detected at TeV energies during the periods of HE gamma-ray flaring suggests that the short-timescale variation might be primarily related to changes in the inverse Compton scattering of photons by the electron population in the jet. The longer-timescale changes suggest a 30--40 year variation in the fuelling of the black hole, that affects the power of the inner jet. NCG 1275 is a laboratory for the class of brightest cluster galaxies, and its variability on these timescales has implications for our understanding of massive galaxies in cooling-core clusters. The case of NGC 1275 highlights the need for wide coverage across the radio band to correctly account for the contribution to emission from a synchrotron self-absorbed core (for example when considering contamination of Sunyaev-Zel'dovich effect observations), and the danger of variability biases in radio surveys of galaxies.

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Blobrana


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Title: Kinematics and Excitation of the Molecular Hydrogen Accretion Disc in NGC 1275
Authors: J. Scharwaechter, P. J. McGregor, M. A. Dopita, T. L. Beck

We report the results of high spatial and spectral resolution integral-field spectroscopy of the central ~3 x 3 arcsec^2 of the active galaxy NGC 1275 (Perseus A), based on observations with the Near-infrared Integral Field Spectrograph (NIFS) and the ALTAIR adaptive-optics system on the Gemini North telescope. The circum-nuclear disc in the inner R~50 pc of NGC 1275 is seen in both the H2 and [FeII] lines. The disc is interpreted as the outer part of a collisionally-excited turbulent accretion disc. The kinematic major axis of the disc at a position angle of 68 deg is oriented perpendicular to the radio jet. A streamer-like feature to the south-west of the disc, detected in H2 but not in [FeII], is discussed as one of possibly several molecular streamers, presumably falling into the nuclear region. Indications of an ionisation structure within the disc are deduced from the HeI and Br gamma emission lines, which may partially originate from the inner portions of the accretion disc. The kinematics of these two lines agrees with the signature of the circum-nuclear disc, but both lines display a larger central velocity dispersion than the H2 line. The rovibrational H2 transitions from the core of NGC 1275 are indicative of thermal excitation caused by shocks and agree with excitation temperatures of ~1360 and ~4290 K for the lower- and higher-energy H2 transitions, respectively. The data suggest X-ray heating as the dominant excitation mechanism of [FeII] emission in the core, while fast shocks are a possible alternative. The [FeII] lines indicate an electron density of ~4000 cm^{-3}. The H2 disc is modelled using simulated NIFS data cubes of H2 emission from inclined discs in Keplerian rotation around a central mass. Assuming a disc inclination of 45 deg ± 10 deg, the best-fitting models imply a central mass of (8^{+7}_{-2}) x 10^8 solar masses.

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Blobrana


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Posts: 131433
Date:
NGC 1275
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Title: Hydrogen Two-Photon Continuum Emission from the Horseshoe Filament in NGC 1275
Authors: R. M. Johnstone, R. E. A. Canning, A. C. Fabian, G. J. Ferland, M. Lykins, R. L. Porter, P. A. M. van Hoof, R. J. R. Williams

Far ultraviolet emission has been detected from a knot of Halpha emission in the Horseshoe filament, far out in the NGC 1275 nebula. The flux detected relative to the brightness of the Halpha line in the same spatial region is very close to that expected from Hydrogen two-photon continuum emission in the particle heating model of Ferland et al. (2009) if reddening internal to the filaments is taken into account. We find no need to invoke other sources of far ultraviolet emission such as hot stars or emission lines from CIV in intermediate temperature gas to explain these data.

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Blobrana


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Posts: 131433
Date:
3C 84
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Title: VLBI and Single Dish Monitoring of 3C84 in the Period of 2009-2011
Authors: Hiroshi Nagai, Monica Orienti, Motoki Kino, Kenta Suzuki, Gabriele Giovannini, Akihiro Doi, Keiichi Asada, Marcello Giroletti, Jun Kataoka, Filippo D'Ammando, Makoto Inoue, Anne Lahteenmaki, Merja Tornikoski, Jonathan Leon-Tavares, Seiji Kameno, Uwe Bach

The radio galaxy 3C 84 is a representative of gamma-ray-bright misaligned active galactic nuclei (AGNs) and one of the best laboratories to study the radio properties of the sub-pc jet in connection with the gamma-ray emission. In order to identify possible radio counterparts of the gamma-ray emissions in 3C 84, we study the change in structure within the central 1 pc and the light curve of sub-pc-size components C1, C2, and C3. We search for any correlation between changes in the radio components and the gamma-ray flares by making use of VLBI and single dish data. Throughout the radio monitoring spanning over two GeV gamma-ray flares detected by the Fermi-LAT and the MAGIC Cherenkov Telescope in the periods of 2009 April to May and 2010 June to August, total flux density in radio band increases on average. This flux increase mostly originates in C3. Although the gamma-ray flares span on the timescale of days to weeks, no clear correlation with the radio light curve on this timescale is found. Any new prominent components and change in morphology associated with the gamma-ray flares are not found on the VLBI images.

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Blobrana


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Posts: 131433
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NGC 1275
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Title: A very extended molecular web around NGC 1275
Authors: P. Salomé, F. Combes, Y. Revaz, D. Downes, A.C. Edge, A.C. Fabian

We present the first detection of CO emission lines in the Halpha filaments at distances as far as 50 kpc from the centre of the galaxy NGC 1275. This gas is probably dense (>=10E3 cm^-3). However, it is not possible to accurately determine the density and the kinetic temperature of this relatively warm gas (Tkin~20-500K) with the current data only. The amount of molecular gas in the filaments is large 10E9 Msun (assuming a Galactic N(H2)/Ico ratio). This is 10% of the total mass of molecular gas detected in this cD galaxy. This gas has large-scale velocities comparable to those seen in Halpha. The origin of the filaments is still unclear, but their formation is very likely linked to the AGN positive feedback (Revaz et al., 2008) that regulates the cooling of the surrounding X-ray-emitting gas as suggested by numerical simulations. We also present high-resolution spectra of the galaxy core. The spatial characteristics of the double-peaked profile suggest that the molecular web of filaments and streamers penetrates down to radii of less than 2 kpc from the central AGN and eventually feed the galaxy nucleus. The mass of gas inside the very central region is ~10E^9 Msun, and is similar to the mass of molecular gas found in the filaments.

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Blobrana


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Title: A wide Chandra view of the core of the Perseus cluster
Authors: A.C. Fabian, J.S. Sanders, S.W. Allen, R.E.A. Canning, E. Churazov, C.S. Crawford, W. Forman, J. GaBany, J. Hlavacek-Larrondo, R.M. Johnstone, H.R. Russell, C.S. Reynolds, P. Salome, G.B. Taylor, A.J. Young

We present new Chandra images of the X-ray emission from the core of the Perseus cluster of galaxies. The total observation time is now 1.4 Ms. New depressions in X-ray surface brightness are discovered to the north of NGC1275, which we interpret as old rising bubbles. They imply that bubbles are long-lived and do not readily breakup when rising in the hot cluster atmosphere. The existence of a 300 kpc long NNW-SSW bubble axis means there cannot be significant transverse large scale flows exceeding 100 km/s. Interesting spatial correlations are seen along that axis in early deep radio maps. A semi-circular cold front about 100 kpc west of the nucleus is seen. It separates an inner disturbed region dominated by the activity of the active nucleus of NGC1275 from the outer region where a subcluster merger dominates.

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