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Title: A Measurement of the Black-Hole Mass in NGC 1097 using ALMA
Author: Kyoko Onishi (1, 2), Satoru Iguchi, Kartik Sheth, Kotaro Kohno ((1) SOKENDAI (The Graduate University for Advanced Studies), (2) National Astronomical Observatory of Japan)

We present an estimate of the mass of the supermassive black hole (SMBH) in the nearby type-1 Seyfert galaxy NGC 1097 using Atacamma Large Millimeter/Submillimeter Array (ALMA) observations of dense gas kinematics. Dense molecular gas dynamics are traced with HCN(J=1-0) and HCO+(J=1-0) emission lines. Assuming a host galaxy inclination of 46°, we derive a SMBH mass, M_BH=1.40^{+0.27}_{-0.32} x 10^8 solar masses, and an I-band mass to light ratio to be 5.14^{+0.03}_{-0.04}, using HCN(J=1-0). The estimated parameters are consistent between the two emission lines. The measured SMBH mass is in good agreement with the SMBH mass and bulge velocity dispersion relationship. Our result showcases ALMA's potential for deriving accurate SMBH masses, especially for nearby late-type galaxies. Larger samples and accurate SMBH masses will further elucidate the relationship between the black hole (BH) and host galaxy properties and constrain the coevolutionary growth of galaxies and BHs.

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Title: Multi-molecule ALMA observations towards the Seyfert 1 galaxy NGC 1097
Author: S.Martin, K. Kohno, T. Izumi, M. Krips, D. S. Meier, R. Aladro, S. Matsushíta, S. Takano, J. L. Turner, D. Espada, T. Nakajima, Y. Terashima, K. Fathi, P.-Y. Hsieh, M. Imanishi, A. Lundgren, N. Nakai, E. Schinnerer, K. Sheth, T. Wiklind

The nearby Sy 1 galaxy NGC 1097 represents an ideal laboratory to explore the molecular chemistry in the presence and surroundings of an active galactic nucleus. Exploring the distribution of different molecular species allows us to understand the physical processes affecting the ISM both in the AGN vicinity as well as in the outer star forming molecular ring. We carried out 3 mm ALMA observations of HCN, HCO+, CCH, CS, HNCO, SiO, HC3N, and SO as well as the 13C isotopologues. All species were imaged over the central 2 kpc (~30") of the galaxy at a resolution of ~2.2"x1.5 (150 pc x 100 pc). HCO+ and CS appear to be slightly enhanced in the star forming ring. CCH, showing the largest variations across NGC 1097, is suggested to be a good tracer of both obscured and early stage star formation. HNCO, SiO and HC3N are significantly enhanced in the inner circumnuclear disk surrounding the AGN. Differences in the molecular abundances are observed between the star forming ring and the inner circumnuclear disk. We conclude that the HCN/HCO+ and HCN/CS differences observed between AGN dominated and starburst galaxies are not due to a HCN enhancement due to X-rays, but rather this enhancement is produced by shocked material at distances of 200 pc from the AGN. Additionally we claim the lower HCN/CS to be a combination of a small under-abundance of CS in AGNs together with excitation effects, where a high dense gas component (~10^6 cm^-3) may be more prominent in SB galaxies. However the most promising are the differences found among the dense gas tracers which, at our modest spatial resolution, seem to outline the physical structure of the molecular disk around the AGN. In this picture, HNCO probes the well shielded gas in the disk, surrounding the dense material moderately exposed to X-ray radiation traced by HC3N. Finally SiO might be the innermost molecule in the disk structure.

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NGC 1097 (also Arp 77, Caldwell 67, ESO 416-20, IRAS 02441-3029, MCG -5-7-24, UGCA 41 and PGC 10488) is a magnitude +10.2 barred spiral galaxy located 45 million light-years away in the constellation Fornax.

The galaxy was discovered by German-British astronomer William Herschel using a 47.5 cm (18.7 inch) f/13 speculum reflector at Windsor Road in Slough, Berkshire on the 9th October 1790.

The galaxy was rediscovered by the Irish astronomer William Parsons 3rd Earl of Rosse, using the 'Parsonstown Leviathan' 182.88 cm (72 inch) reflector at Birr Castle on the 29th October 1851. 

Right Ascension 02h 46m 19.0s, Declination -30° 16' 30"

Three supernovae (SN 1992bd, SN 1999eu, and SN 2003B) have been observed in NGC 1097.
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Title: Hydrodynamical Simulations of the Barred Spiral Galaxy NGC 1097
Authors: Lien-Hsuan Lin, Hsiang-Hsu Wang, Pei-Ying Hsieh, Ronald E. Taam, Chao-Chin Yang, David C. C. Yen

NGC 1097 is a nearby barred spiral galaxy believed to be interacting with the elliptical galaxy NGC 1097A located to its northwest. It hosts a Seyfert 1 nucleus surrounded by a circumnuclear starburst ring. Two straight dust lanes connected to the ring extend almost continuously out to the bar. The other ends of the dust lanes attach to two main spiral arms. To provide a physical understanding of its structural and kinematical properties, two-dimensional hydrodynamical simulations have been carried out. Numerical calculations reveal that many features of the gas morphology and kinematics can be reproduced provided that the gas flow is governed by a gravitational potential associated with a slowly rotating strong bar. By including the self-gravity of the gas disk in our calculation, we have found the starburst ring to be gravitationally unstable which is consistent with the observation in Hsieh et al. (2011). Our simulations show that the gas inflow rate is 0.17 solar masses yr^{-1} into the region within the starburst ring even after its formation, leading to the coexistence of both a nuclear ring and a circumnuclear disk.

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Title: ALMA follows streaming of dense gas down to 40 pc from the supermassive black hole in NGC1097
Authors: Kambiz Fathi, Andreas A. Lundgren, Kotaro Kohno, Nuria Piñol-Ferrer, Sergio Martín, Daniel Espada, Evanthia Hatziminaoglou, Masatoshi Imanishi, Takuma Izumi, Melanie Krips, Satoki Matsushíta, David S. Meier, Naomasa Nakai, Kartik Sheth, Jean Turner, Glenn van de Ven, Tommy Wiklind

We present a kinematic analysis of the dense molecular gas in the central 200 parsecs of the nearby galaxy NGC1097, based on Cycle 0 observations with the Atacama Large Millimetre/sub-millimetre Array (ALMA). We use the HCN(4-3) line to trace the densest interstellar molecular gas, and quantify its kinematics, and estimate an inflow rate for the molecular gas. We find a striking similarity between the ALMA kinematic data and the analytic spiral inflow model that we have previously constructed based on ionised gas velocity fields on larger scales. We are able to follow dense gas streaming down to 40 pc distance from the supermassive black hole in this Seyfert 1 galaxy. In order to fulfil marginal stability, we deduce that the dense gas is confined to a very thin disc, and we derive a dense gas inflow rate of 0.09 solar masses/yr at 40 pc radius. Combined with previous values from the Ha and CO gas, we calculate a combined molecular and ionised gas inflow rate of 0.2 solar masses/yr at 40 pc distance from the central supermassive black hole of NGC1097.

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Hubble Eyes a Wanderer Dancing the Dance of Stars and Space

716517main1_ngc1097-673.JPG

The NASA/ESA Hubble Space Telescope provides us this week with a spectacular image of the bright star-forming ring that surrounds the heart of the barred spiral galaxy NGC 1097. In this image, the larger-scale structure of the galaxy is barely visible: its comparatively dim spiral arms, which surround its heart in a loose embrace, reach out beyond the edges of this frame.
This face-on galaxy, lying 45 million light-years away from Earth in the southern constellation of Fornax (The Furnace), is particularly attractive for astronomers. NGC 1097 is a Seyfert galaxy. Lurking at the very center of the galaxy, a supermassive black hole 100 million times the mass of our sun is gradually sucking in the matter around it. The area immediately around the black hole shines powerfully with radiation coming from the material falling in.

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Title: The Central Region of the Barred Spiral Galaxy NGC1097 Probed by AKARI Near-Infrared Spectroscopy
Authors: Toru Kondo, Hidehiro Kaneda, Shinki Oyabu, Daisuke Ishihara, Tatsuya Mori, Mitsuyoshi Yamagishi, Takashi Onaka, Itsuki Sakon, Toyoaki Suzuki

With the Infrared Camera on board AKARI, we carried out near-infrared (2.5-5.0 micron) spectroscopy of the central kiloparsec region of the barred spiral galaxy, NGC1097, categorised as Seyfert 1 with a circumnuclear starburst ring. Our observations mapped the area of ~50"*10" with the resolution of ~5", covering about a half of the ring and the galactic center. As a result, we spatially resolve the starburst ring in the polycyclic aromatic hydrocarbon 3.3 micron, the aliphatic hydrocarbon 3.4-3.6 micron features, and the hydrogen Br alpha 4.05 micron emission. They exhibit spatial distributions significantly different from each other, indicating that the environments vary considerably around the ring. In particular, the aliphatic features are enhanced near the bar connecting the ring with the nucleus, where the structure of hydrocarbon grains seems to be relatively disordered. Near the center, the continuum emission and the CO/SiO absorption features are strong, which indicates that the environments inside the ring are dominated by old stellar populations. The near-infrared spectra do not show any evidence for the presence of nuclear activity.

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Title: A Study of Heating and Cooling of the ISM in NGC 1097 with Herschel-PACS and Spitzer-IRS
Authors: P. Beirao, L. Armus, G. Helou, P. N. Appleton, J.-D. T. Smith, K. V. Croxall, E. J. Murphy, D. A. Dale, B. T. Draine, M. G. Wolfire, K. M. Sandstrom, G. Aniano, A. D. Bolatto, B. Groves, B. R. Brandl, E. Schinnerer, A. F. Crocker, J. L. Hinz, H.-W. Rix, R. C. Kennicutt, D. Calzetti, A. Gil de Paz, G. Dumas, M. Galametz, K. D. Gordon, C.-N. Hao, B. Johnson, J. Koda, O. Krause, T. van der Laan, A. K. Leroy, Y. Li, S. E. Meidt, J. D. Meyer, N. Rahman, H. Roussel, M. Sauvage, S. Srinivasan, L. Vigroux, F. Walter, B. E. Warren

NGC 1097 is a nearby Seyfert 1 galaxy with a bright circumnuclear starburst ring, a strong large-scale bar and an active nucleus. We present a detailed study of the spatial variation of the far infrared (FIR) [CII]158um and [OI]63um lines and mid-infrared H2 emission lines as tracers of gas cooling, and of the polycyclic aromatic hydrocarbon (PAH) bands as tracers of the photoelectric heating, using Herschel-PACS, and Spitzer-IRS infrared spectral maps. We focus on the nucleus and the ring, and two star forming regions (Enuc N and Enuc S). We estimated a photoelectric gas heating efficiency ([CII]158um+[OI]63um)/PAH in the ring about 50% lower than in Enuc N and S. The average 11.3/7.7um PAH ratio is also lower in the ring, which may suggest a larger fraction of ionised PAHs, but no clear correlation with [CII]158{\mu}m/PAH(5.5 - 14um) is found. PAHs in the ring are responsible for a factor of two more [CII]158um and [OI]63um emission per unit mass than PAHs in the Enuc S. SED modelling indicates that at most 25% of the FIR power in the ring and Enuc S can come from high intensity photodissociation regions (PDRs), in which case G0 ~ 10^2.3 and nH ~ 10^3.5 cm^-3 in the ring. For these values of G0 and nH PDR models cannot reproduce the observed H2 emission. Much of the the H2 emission in the starburst ring could come from warm regions in the diffuse ISM that are heated by turbulent dissipation or shocks.

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Title: VLT Observations of NGC 1097's "dog-leg" tidal stream
Authors: Pasquale Galianni, Ferdinando Patat, James L. Higdon, Steffen Mieske, Pavel Kroupa

CONTEXT: Dwarf Spheroidal Galaxies and tidal streams. AIMS: We investigate the structure and stellar population of two large stellar condensations (knots A & B) along one of the faint optical "jet-like" tidal streams associated with the spiral NGC 1097, with the goal of establishing their physical association with the galaxy and their origin.
METHODS: We use the VLT/FORS2 to get deep V-band imaging and low-resolution optical spectra of two knots along NGC 1097's northeast "dog-leg" tidal stream. With this data, we explore their morphology and stellar populations.
RESULTS: The FORS2 spectra show that the redshift of knot A (and perhaps of knot B) is consistent with that of NGC 1097. The FORS2 photometry shows that the two knots match very well the photometric scaling relations of canonical dwarf spheroidal galaxies (dSph). From the spectral analysis we find that knot A is mainly composed of stars near G-type, with no signs of ongoing star formation. Comparing its spectrum to a library of Galactic GC spectra, we find that the stellar population of this dSph-like object is most similar to intermediate to metal rich GCs. We find moreover, that the tidal stream shows an "S" shaped inflection as well as a pronounced stellar overdensity at knot A's position. This suggests that knot A is being tidally stripped, and populates the stellar stream with its stars.
CONCLUSIONS: We have discovered that two knots along NGC 1097's northeast tidal stream share most of their spectral and photometric properties with ordinary dwarf spheroidal galaxies (dSph). Moreover, we find strong indications that the "dog-leg" tidal stream arise from the tidal disruption of knot A. Since it has been demonstrated that tidally stripping dSph galaxies need to loose most of their dark matter before starting to loose stars, we suggest that knot A is at present a CDM-poor object.

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NASA's amazing infrared image of galaxy
This image provided by NASA this July 23, 2009 is a photo made by the Spitzer Space Telescope of the galaxy, called NGC-1097, is located 50 million light-years away.
It is spiral-shaped like our Milky Way, with long, spindly arms of stars.

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