共查询到20条相似文献，搜索用时 15 毫秒
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The SAURON project – III. Integral-field absorption-line kinematics of 48 elliptical and lenticular galaxies 总被引：1，自引：0，他引：1
Eric Emsellem Michele Cappellari Reynier F. Peletier Richard M. McDermid R. Bacon M. Bureau † Y. Copin Roger L. Davies Davor Krajnovi&#; Harald Kuntschner Bryan W. Miller P. Tim de Zeeuw 《Monthly notices of the Royal Astronomical Society》2004,352(3):721-743
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The velocity field of large‐scale non‐Hubble galaxy motion recovered from peculiar velocities of spiral galaxies is distorted due to measurement errors and deviations from Tully‐Fisher relationship. To figure out how this affects the multipole structure we use the Monte‐Carlo approach and simulate errors and deviations. We use the galaxies from the Revised Flat Galaxy Catalogue subsample and the generalized Tully‐Fisher relationship in the ‘H I line width–angular diameter’ version. The analysis of the multipole structure has shown that the dipole velocity component (bulk motion) is underestimated, and the characteristic values of the quadrupole component are overestimated. The directions of the quadrupole component's eigenvectors can be determined precisely enough. Typical deviation angles of bulk motion apices lie between 17 and 40.. The main input is caused by errors in the measurement of the angular diameter. The probability of the quadrupole component being incidental can be estimated at the 4 per cent level. For the octopole component, it can be estimated at the 7–10 per cent level. This is essentially higher than the estimations less than 1 per cent due to the Fisher test. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
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J. H. Knapen 《Astrophysics and Space Science》2005,295(1-2):85-94
There is considerable evidence that the circumnuclear regions of galaxies are intimately related to their host galaxies, most directly through their bars. There is also convincing evidence for relations between the properties of supermassive black holes in the nuclei of galaxies and those of their host galaxies. It is much less clear, however, how stellar (starburst) and non-stellar (AGN) activity in the nuclear regions can be initiated and fuelled. Here, we review the evidence for gas transport from the disk to the nuclear and circumnuclear regions of galaxies, as well as the statistical relationships between the occurrence of nuclear activity and mechanisms which can cause central gas concentration. In particular, I explore the roles played by bars and interactions, and conclude that in specific, mostly extreme, cases bars and interactions are indeed observed to be connected to nuclear activity. The overall lack of observational evidence for direct causal relationships between the presence of bars and interactions on the one hand, and starburst or Seyfert activity on the other could, however, easily be due to the possibility that we are not yet considering the correct spatial- or time-scales. 相似文献
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Cheng-Gang Shu Hou-Jun Mo Shu-De Mao Joint Center for Astrophysics Shanghai Normal University Shanghai cgshu@center. shao. ac. cn Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai Max-Planck-Institut fur Astrophysik Karl-Schwarzschild-Strasse Postfach D- Garching Germany Astronomy Department University of Massachusetts Amherst MA USA Jodrell Bank Observatory Univ. of Manchester Macclesfield Cheshire SK DL UK 《中国天文和天体物理学报》2005,5(4):327-346
Galactic winds and mass outflows are observed both in nearby starburst galaxies and in high-redshift star-forming galaxies. We develop a simple analytic model to understand the observed superwind phenomenon with a discussion of the model uncertainties. Our model is built upon the model of McKee & Ostriker for the interstellar medium. It allows one to predict how properties of a superwind, such as wind velocity and mass outflow rate, are related to properties of its starforming host galaxy, such as size, gas density and star formation rate. The model predicts a threshold of star formation rate density for the generation of observable galactic winds. Galaxies with more concentrated star formation activities produce superwinds with higher velocities. The predicted mass outflow rates are comparable to (or slightly larger than) the corresponding star formation rates. We apply our model to both local starburst galaxies and high-redshift Lyman break galaxies, and find its predictions to be in good agreement with current observations. Our model is simple and so can be easily incorporated into numerical simulations and semi-analytical models of galaxy formation. 相似文献
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E. Pignatelli E. M. Corsini J. C. Vega Beltrán C. Scarlata A. Pizzella J. G. Funes S. J. W. W. Zeilinger J. E. Beckman F. Bertola 《Monthly notices of the Royal Astronomical Society》2001,323(1):188-210
We present V -band surface photometry and major-axis kinematics of stars and ionized gas of three early-type spiral galaxies, namely NGC 772, 3898 and 7782. For each galaxy we present a self-consistent Jeans model for the stellar kinematics, adopting the light distribution of bulge and disc derived by means of a two-dimensional parametric photometric decomposition. This allows us to investigate the presence of non-circular gas motions, and derive the mass distribution of luminous and dark matter in these objects.
NGC 772 and 7782 have apparently normal kinematics with the ionized gas tracing the gravitational equilibrium circular speed. This is not true in the innermost region (| r |≲8 arcsec) of NGC 3898, where the ionized gas is rotating more slowly than the circular velocity predicted by dynamical modelling. This phenomenon is common in the bulge-dominated galaxies for which dynamical modelling enables us to make the direct comparison between the gas velocity and the circular speed, and it poses questions about the reliability of galaxy mass distributions derived by the direct decomposition of the observed ionized-gas rotation curve into the contributions of luminous and dark matter. 相似文献
NGC 772 and 7782 have apparently normal kinematics with the ionized gas tracing the gravitational equilibrium circular speed. This is not true in the innermost region (| r |≲8 arcsec) of NGC 3898, where the ionized gas is rotating more slowly than the circular velocity predicted by dynamical modelling. This phenomenon is common in the bulge-dominated galaxies for which dynamical modelling enables us to make the direct comparison between the gas velocity and the circular speed, and it poses questions about the reliability of galaxy mass distributions derived by the direct decomposition of the observed ionized-gas rotation curve into the contributions of luminous and dark matter. 相似文献
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Stellar velocity dispersion in narrow-line Seyfert 1 galaxies 总被引：1，自引：0，他引：1
V. Botte † S. Ciroi † F. Di Mille P. Rafanelli A. Romano 《Monthly notices of the Royal Astronomical Society》2005,356(2):789-793
Several authors have recently explored, for narrow-line Seyfert 1 galaxies (NLS1s), the relationship between black hole mass ( M BH ) and stellar velocity dispersion (σ* ). Their results are more or less in agreement and seem to indicate that NLS1s fill the region below the fit obtained by Tremaine et al., showing a range of σ* similar to that of Seyfert 1 galaxies, and a lower M BH . Until now, the [O iii ] width has been used in place of the stellar velocity dispersion, but some indications have begun to arise against the effectiveness of the gaseous kinematics in representing the bulge potential, at least in NLS1s. Bian & Zhao have stressed the urgency of producing true σ* measurements. Here, we present new stellar velocity dispersions obtained through direct measurements of the Ca ii absorption triplet (∼8550 Å) in the nuclei of eight NLS1 galaxies. The resulting σ* values and a comparison with σ[O III] confirm our suspicion that [O iii ] typically overestimates the stellar velocity dispersion. We demonstrate that NLS1s follow the M BH –σ* relation as Seyfert 1, quasars and non-active galaxies. 相似文献
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R. Auld W. J. G. de Blok E. Bell J. I. Davies 《Monthly notices of the Royal Astronomical Society》2006,366(4):1475-1492
We present observations ( B, R, K , Hα and H i ) of six nearby low surface brightness galaxies (LSBGs). They show an astonishing amount of variety; while some systems appear smooth and featureless, others resolve into loose assemblies of gas clouds. We have derived rotation curves, gas surface density profiles and star formation thresholds for three of the galaxies.
The results have been used to test two ideas describing their star formation: one in which star formation depends solely on the H i gas surface density, and one that depends on differential rotation. We find that a critical H i surface density criterion in the range 2.6–12.6 × 1020 cm−2 (2.1–10.1 M⊙ pc−2 ) best describes the star-forming ability of these galaxies on local and global scales. A critical gas surface density based on the rotation of the gas is also able to describe the results on a global scale for two of the three galaxies for which we were able to derive rotation curves. 相似文献
The results have been used to test two ideas describing their star formation: one in which star formation depends solely on the H i gas surface density, and one that depends on differential rotation. We find that a critical H i surface density criterion in the range 2.6–12.6 × 10
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T. Treu † M. Stiavelli P. Møller S. Casertano G. Bertin ‡ 《Monthly notices of the Royal Astronomical Society》2001,326(1):221-236
A sample of field early-type galaxies (E/S0) at intermediate redshift ( z ∼0.1–0.6) is selected, based on morphology and colours from HST -WFPC2 parallel images. Photometric structural parameters (effective radius R e and effective surface brightness SB e ) are derived through the F606W and F814W filters, using luminosity profile fitting and two-dimensional fitting techniques. The combined parameter that enters the Fundamental Plane (log R e − βSB e , with β ≈0.32) is shown to suffer from significantly smaller uncertainties (rms 0.03) than the individual structural parameters (e.g. ∼15 per cent rms on the effective radius).
High signal-to-noise ratio, intermediate-resolution spectra, taken at the ESO 3.6-m telescope, yield redshifts for 35 galaxies and central velocity dispersions for 22 galaxies. Central velocity dispersions are derived using a library of stellar templates covering a wide range of spectral types, in order to study the effects of template mismatches. The average random error on the central velocity dispersion is found to be 8 per cent, and the average systematic error caused by template mismatch is found to be 5 per cent. The errors in the velocity dispersion measurement and the effects of template mismatches are studied by means of extensive Monte Carlo simulations. In addition, we investigate whether the determination of the velocity dispersion is sensitive to the spectral range used, finding that the value of velocity dispersion is unchanged when the spectral regions that include the absorption features Ca H and K and NaD are masked out during the fit. 相似文献
High signal-to-noise ratio, intermediate-resolution spectra, taken at the ESO 3.6-m telescope, yield redshifts for 35 galaxies and central velocity dispersions for 22 galaxies. Central velocity dispersions are derived using a library of stellar templates covering a wide range of spectral types, in order to study the effects of template mismatches. The average random error on the central velocity dispersion is found to be 8 per cent, and the average systematic error caused by template mismatch is found to be 5 per cent. The errors in the velocity dispersion measurement and the effects of template mismatches are studied by means of extensive Monte Carlo simulations. In addition, we investigate whether the determination of the velocity dispersion is sensitive to the spectral range used, finding that the value of velocity dispersion is unchanged when the spectral regions that include the absorption features Ca H and K and NaD are masked out during the fit. 相似文献
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