共查询到20条相似文献，搜索用时 31 毫秒
1.
2.
We present an analysis of the orientations of 1433 galaxies found in the region 15h 48m ≤α(2000) ≤ 19h 28m , −68°≤δ(2000) ≤−62° . In this region we investigated three Abell clusters (S0794, S0797, S0805) of richness Class 0 and the Triangulum Australis cluster. Our aim is to examine non-random effects in galaxy orientations in clusters. In addition, we classified the investigated galaxies into subsamples on the basis of their axial ratio, major diameter and morphology. The spin vector orientations of total galaxies in the investigated region is found to be random. No preferred orientation is found in the clusters. We could not note any morphological dependence of the galaxy orientations in our samples. No preferred orientations can be seen for the spiral galaxies. The morphologically unidentified galaxies, galaxies having major diameters of <47 arcsec, and the nearly edge-on galaxies ( b / a < 0.5, 0.4 < b / a ≤ 0.5) show anisotropy: spin vectors of galaxies tend to be oriented perpendicular to the Local Supercluster plane and spin vector projections tend to point radially with respect to the Virgo cluster centre. 相似文献
3.
I. Trujillo A. Asensio Ramos J. A. Rubiño-Martín Alister W. Graham J. A. L. Aguerri J. Cepa C. M. Gutiérrez 《Monthly notices of the Royal Astronomical Society》2002,333(3):510-516
We have investigated the structural and dynamical properties of triaxial stellar systems whose surface brightness profiles follow the r 1/ n luminosity law – extending the analysis by Ciotti, who explored the properties of spherical r 1/ n systems. A new analytical expression that accurately reproduces the spatial (i.e., deprojected) luminosity density profiles (error less than 0.1 per cent) is presented for detailed modelling of the Sérsic family of luminosity profiles. We evaluate both the symmetric and the non-axisymmetric components of the gravitational potential and force, and compute the torques as a function of position. For a given triaxiality, stellar systems with smaller values of n have a greater non-axisymmetric gravitational field component . We also explore the strength of the non-axisymmetric forces produced by bulges with differing n and triaxiality on systems having a range of bulge-to-disc ratios. The increasing disc-to-bulge ratio with increasing galaxy type (decreasing n ) is found to greatly reduce the amplitude of the non-axisymmetric terms, and therefore reduce the possibility that triaxial bulges in late-type systems may be the mechanism or perturbation for non-symmetric structures in the disc.
Using seeing-convolved r1/ n -bulge plus exponential-disc fits to the K -band data from a sample of 80 nearby disc galaxies, we probe the relations between galaxy type, Sérsic index n and the bulge-to-disc luminosity ratio. These relations are shown to be primarily a consequence of the relation between n and the total bulge luminosity. In the K band, the trend of decreasing bulge-to-disc luminosity ratio along the spiral Hubble sequence is predominantly, though not entirely, a consequence of the change in the total bulge luminosity; the trend between the total disc luminosity and Hubble type is much weaker. 相似文献
Using seeing-convolved r
4.
5.
Roland Jesseit Michele Cappellari Thorsten Naab Eric Emsellem Andreas Burkert 《Monthly notices of the Royal Astronomical Society》2009,397(3):1202-1214
We use two-dimensional kinematic maps of simulated binary disc mergers to investigate the λR -parameter, which is a luminosity-weighted measure of projected angular momentum per unit mass. This parameter was introduced to subdivide the SAURON sample of early-type galaxies in so-called fast λR > 0.1 and slow rotators λR < 0.1 . Tests on merger remnants reveal that λR is a robust indicator of the true angular momentum content in elliptical galaxies. We find the same range of λR values in our merger remnants as in the SAURON galaxies. The merger mass ratio is decisive in transforming fast rotators into slow rotators in a single binary merger, the latter being created mostly in an equal-mass merger. Slow rotators have a λR which does not vary with projection. The confusion rate with face-on fast rotators is very small. Mergers with a gas component form slow rotators with smaller ellipticities than collisionless merger remnants have, and are in much better agreement with the SAURON slow rotators. Remergers of merger remnants are slow rotators, but tend to have too high ellipticities. Fast rotators maintain the angular momentum content from the progenitor disc galaxy if merger mass ratio is high. Some SAURON galaxies have values of λ R as high as our progenitor disc galaxies. 相似文献
6.
Russell J. Smith John R. Lucey Michael J. Hudson David J. Schlegel Roger L. Davies 《Monthly notices of the Royal Astronomical Society》2000,313(3):469-490
We present new spectroscopic data for 532 early-type galaxies, predominantly Abell cluster members with cz <12 000 km s−1 . We tabulate 919 individual measurements, from six observing runs, for recession velocity, cz , central velocity dispersion, σ , and magnesium line-strength indices, Mg2 and Mg b . The median estimated error, per measurement, in σ is 5 per cent. The Mg2 line-strength data have median errors of 0.009 mag. The observed scatter between repeat measurements is largely accounted for by photon-counting errors. These data will be employed in forthcoming papers, where they will form part of a merged and standardized catalogue of Fundamental Plane data for use in cluster distance estimates and peculiar velocity analyses. 相似文献
7.
H. Sugai R. I. Davies M. Ishii M. J. Ward 《Monthly notices of the Royal Astronomical Society》2000,317(2):447-452
We have obtained an H2 v =1–0 S(1) image of a merging galaxy system, NGC 6090, by using a Fabry–Perot imager. The H2 emission originates between the double nuclei of pre-merger galaxies, and exhibits an arc-like or ring-like structure almost connecting the double nuclei. This structure is similar to that suggested for Arp 220 from the velocity field measured by CO radio emission. The separation of the double nuclei in NGC 6090 is 5–6 arcsec, corresponding to a projected distance of 3–4 kpc. This is much larger than that of Arp 220 and suggests that the molecular gas distribution can form an organized shape between the nuclei, such as a ring, in a rather early phase of merging. 相似文献
8.
Nicholas Scott Michele Cappellari Roger L. Davies R. Bacon P. T. de Zeeuw Eric Emsellem Jésus Falcón-Barroso Davor Krajnovi&#; Harald Kuntschner Richard M. McDermid Reynier F. Peletier Antonio Pipino Marc Sarzi Remco C. E. van den Bosch Glenn van de Ven † Eveline van Scherpenzeel 《Monthly notices of the Royal Astronomical Society》2009,398(4):1835-1857
9.
10.
Michele Cappellari Eric Emsellem R. Bacon M. Bureau Roger L. Davies P. T. de Zeeuw Jesús Falcón-Barroso Davor Krajnovi&#; Harald Kuntschner Richard M. McDermid Reynier F. Peletier Marc Sarzi Remco C. E. van den Bosch Glenn van de Ven † 《Monthly notices of the Royal Astronomical Society》2007,379(2):418-444
11.
Igor V. Chilingarian 《Monthly notices of the Royal Astronomical Society》2009,394(3):1229-1248
Understanding the origin and evolution of dwarf early-type galaxies remains an important open issue in modern astrophysics. Internal kinematics of a galaxy contains signatures of violent phenomena which may have occurred, e.g. mergers or tidal interactions, while stellar population keeps a fossil record of the star formation history; therefore studying connection between them becomes crucial for understanding galaxy evolution. Here, in the first paper of the series, we present the data on spatially resolved stellar populations and internal kinematics for a large sample of dwarf elliptical (dE) and lenticular (dS0) galaxies in the Virgo cluster. We obtained radial velocities, velocity dispersions, stellar ages and metallicities out to 1–2 half-light radii by reanalysing already published long-slit and integral-field spectroscopic data sets using the nbursts full spectral fitting technique. Surprisingly, bright representatives of the dE/dS0 class ( MB =−18.0 to −16.0 mag) look very similar to intermediate-mass and giant lenticulars and ellipticals: (1) their nuclear regions often harbour young metal-rich stellar populations always associated with the drops in the velocity dispersion profiles; (2) metallicity gradients in the main discs/spheroids vary significantly from nearly flat profiles to −0.9 dex r −1 e , i.e. somewhat three times steeper than for typical bulges; (3) kinematically decoupled cores were discovered in four galaxies, including two with very little, if any, large-scale rotation. These results suggest similarities in the evolutionary paths of dwarf and giant early-type galaxies and call for reconsidering the role of major mergers in the dE/dS0 evolution. 相似文献
12.
13.
K. K. Knudsen P. P. van der Werf J.-P. Kneib 《Monthly notices of the Royal Astronomical Society》2008,384(4):1611-1626
We have conducted a submillimetre mapping survey of faint, gravitationally lensed sources, where we have targeted 12 galaxy clusters and additionally the New Technology Telescope (NTT) Deep Field. The total area surveyed is 71.5 arcmin2 in the image plane; correcting for gravitational lensing, the total area surveyed is 40 arcmin2 in the source plane for a typical source redshift z ≈ 2.5. In the deepest maps, an image plane depth of 1σ rms ∼0.8 mJy is reached. This survey is the largest survey to date to reach such depths. In total 59 sources were detected, including three multiply imaged sources. The gravitational lensing makes it possible to detect sources with flux density below the blank field confusion limit. The lensing-corrected fluxes range from 0.11 to 19 mJy. After correcting for multiplicity, there are 10 sources with fluxes <2 mJy of which seven have submJy fluxes, doubling the number of such sources known. Number counts are determined below the confusion limit. At 1 mJy, the integrated number count is ∼104 deg−2 , and at 0.5 mJy it is ∼2 × 104 deg−2 . Based on the number counts, at a source plan flux limit of 0.1 mJy, essentially all of the 850-μm background emission has been resolved. The dominant contribution (>50 per cent) to the integrated background arises from sources with fluxes S 850 between 0.4 and 2.5 mJy, while the bright sources S 850 > 6 mJy contribute only 10 per cent. 相似文献
14.
M. Trichas A. Georgakakis M. Rowan-Robinson K. Nandra D. Clements M. Vaccari 《Monthly notices of the Royal Astronomical Society》2009,399(2):663-670
We explore the nature of X-ray sources with 70 μm counterparts selected in the Spitzer Wide-Area Infrared Extragalactic Survey (SWIRE) fields: ELAIS-N1, Lockman Hole and Chandra Deep Field South, for which Chandra X-ray data are available. A total of 28 X-ray/ 70 μm sources in the redshift interval 0.5 < z < 1.3 are selected. The X-ray luminosities and the shape of the X-ray spectra show that these sources are active galactic nuclei (AGN). Modelling of the optical to far-infrared (IR) spectral energy distribution indicates that most of them (27/28) have a strong starburst component (>50 M⊙ yr−1 ) that dominates in the IR. It is found that the X-ray and IR luminosities of the sample sources are broadly correlated, consistent with a link between AGN activity and star formation. Contrary to the predictions of some models for the co-evolution of AGN and galaxies, the X-ray/ 70 μm sources in the sample are not more obscured at X-ray wavelengths compared to the overall X-ray population. It is also found that the X-ray/ 70 μm sources have lower specific star formation rates compared to the general 70 μm population, consistent with AGN feedback moderating the star formation in the host galaxies. 相似文献
15.
16.
17.
L. Cortese A. Boselli P. Franzetti R. Decarli G. Gavazzi S. Boissier V. Buat 《Monthly notices of the Royal Astronomical Society》2008,386(2):1157-1168
We investigate the dependence of the total-IR (TIR) to ultraviolet (UV) luminosity ratio method for calculating the UV dust attenuation A (UV) from the age of the underlying stellar populations by using a library of spectral energy distributions for galaxies with different star formation histories. Our analysis confirms that the TIR/UV versus A (UV) relation varies significantly with the age of the underlying stellar population: that is, for the same TIR/UV ratio, systems with low specific star formation rate (SSFR) suffer a lower UV attenuation than starbursts. Using a sample of nearby field and cluster spiral galaxies, we show that the use of a standard (i.e. age-independent) TIR/UV versus A (UV) relation leads to a systematic overestimate up to 2 mag of the amount of UV dust attenuation suffered by objects with low SSFR and in particular H i -deficient star-forming cluster galaxies. This result points out that the age-independent TIR/UV versus A (UV) relation cannot be used to study the UV properties of large samples of galaxies including low star-forming systems and passive spirals. Therefore, we give some simple empirical relations from which the UV attenuation can be estimated taking into account its dependence on the age of the stellar populations, providing a less biased view of UV properties of galaxies. 相似文献
18.
Russell J. Smith † J.R. Lucey D.J. Schlegel ‡ Michael J. Hudson § Glenn Baggley Roger L. Davies 《Monthly notices of the Royal Astronomical Society》2001,327(1):249-264
We present new R -band photometric data for 447 galaxies, gathered for the 'Streaming Motions of Abell Clusters' (SMAC) project. The data comprise 629 individual measurements of the Fundamental Plane (FP) parameters effective radius ( R e ) and surface brightness (〈 μ 〉e ), derived from r 1/4 -law profile fitting. More than a third of the galaxies were observed more than once. The photometric precision is ∼0.02 mag as judged from comparisons of aperture photometry between repeat observations of galaxies. The combination which enters into the Fundamental Plane relation, has internal uncertainties of ∼0.008, corresponding to < 2 per cent in estimated distance. Taken individually, the (correlated) internal errors in R e and 〈 μ 〉e are ∼8 per cent and ∼0.12 mag respectively. Comparisons with literature data constrain the external random errors to ≲5 per cent in distance (per observation), which is small in comparison to the ∼20 per cent scatter in the FP. The data will form part of a merged catalogue of FP parameters, presented in a companion paper. 相似文献
19.
M. S. Westmoquette L. J. Smith J. S. Gallagher III K. M. Exter † 《Monthly notices of the Royal Astronomical Society》2007,381(3):913-931
We present a set of four Gemini-North Multi-Object Spectrograph/integral field unit (IFU) observations of the central disturbed regions of the dwarf irregular starburst galaxy NGC 1569, surrounding the well-known superstar clusters A and B. This continues on directly from a companion paper, in which we describe the data reduction and analysis techniques employed and present the analysis of one of the IFU pointings. By decomposing the emission-line profiles across the IFU fields, we map out the properties of each individual component identified and identify a number of relationships and correlations that allow us to investigate in detail the state of the ionized interstellar medium (ISM). Our observations support and expand on the main findings from the analysis of the first IFU position, where we conclude that a broad (≲400 km s−1 ) component underlying the bright nebular emission lines is produced in a turbulent mixing layer on the surface of cool gas knots, set up by the impact of the fast-flowing cluster winds. We discuss the kinematic, electron-density and excitation maps of each region in detail and compare our results to previous studies. Our analysis reveals a very complex environment with many overlapping and superimposed components, including dissolving gas knots, rapidly expanding shocked shells and embedded ionizing sources, but no evidence for organized bulk motions. We conclude that the four IFU positions presented here lie well within the starburst region where energy is injected, and, from the lack of substantial ordered gas flows, within the quasi-hydrostatic zone of the wind interior to the sonic point. The net outflow occurs at radii beyond 100–200 pc, but our data imply that mass-loading of the hot ISM is active even at the roots of the wind. 相似文献
20.
Jonathan Irwin Suzanne Aigrain Simon Hodgkin Keivan G. Stassun Leslie Hebb Mike Irwin Estelle Moraux Jerome Bouvier Aude Alapini Richard Alexander D. M. Bramich Jon Holtzman Eduardo L. Martín Mark J. McCaughrean Frédéric Pont P. E. Verrier María Rosa Zapatero Osorio 《Monthly notices of the Royal Astronomical Society》2007,380(2):541-550
We present a general recipe for constructing N -body realizations of galaxies comprising near spherical and disc components. First, an exact spherical distribution function for the spheroids (halo and bulge) is determined, such that it is in equilibrium with the gravitational monopole of the disc components. Second, an N -body realization of this model is adapted to the full disc potential by growing the latter adiabatically from its monopole. Finally, the disc is sampled with particles drawn from an appropriate distribution function, avoiding local-Maxwellian approximations. We performed test simulations and find that the halo and bulge radial density profile very closely match their target model, while they become slightly oblate due to the added disc gravity. Our findings suggest that vertical thickening of the initially thin disc is caused predominantly by spiral and bar instabilities, which also result in a radial re-distribution of matter, rather than scattering off interloping massive halo particles. 相似文献