A DWT Power Spectrum Analysis of PSCz Galaxies

The power spectrum estimator based on the Discrete Wavelet Transformation (DWT) is applied to detect the clustering power in the IRAS Point Source Catalog Redshift Survey(PSCz). Comparison with mock samples extracted from N-body simulation shows that the DWT power spectrum estimator could provide a robust measurement of banded fluctuation power over a range of wavenumbers 0.1-2.0h Mpc^-1. We have fitted three typical CDM models (SCDM, TCDM and ACDM) using the Peacock-Dodds formula including non-linear evolution and redshift distortion. We find that, our results are in good agreement with other statistical measurements of the PSCz.     

Feeding Monsters – A Study of Active Galaxies

We present new interferometric observations of the molecular gas distribution and kinematics in the nuclei of different active galaxies at high angular resolution and high sensitivity carried out with the IRAM Plateau de Bure interferometer (PdBI). The observations cover galaxies in a redshift range of 0.03–1.4. We have so far observed five different active galaxies: NGC3718, NGC1068, HE1029–1831, 3C48 and Q0957+561. The first two objects belong to the NUGA (NUclei of GAlaxies) project – an international collaboration mainly between Spain, France and Germany – containing about 30 Seyfert and LINER galaxies. Both are at the same distance of 14Mpc and show a warped gas and dust disk. The new mosaic map of NGC3718 corrected for short-spacing effects with IRAM 30 m observations well demonstrates the existence of the warped gas disk with several secondary maxima in the projected gas distribution caused by orbit crowding effects. Based on these new data we have improved recent simulations of the warped disk in NGC3718. HE1029–1831 and 3C48 are nearby QSOs. HE1029–1831 is taken out of the Cologne nearby QSO sample. The maps of the integrated CO(1–0) and CO(2–1) emission clearly show that the molecular gas is mostly related to the central bulge with a non-negligible fraction distributed along the bar known from optical observations. Our new CO data of 3C48 unveil new information about the kinematics of its molecular gas complementing and improving further studies based on previous infrared observations and detailed multi-particle simulations. Finally, new measurements of the CO(1–0) line in Q0957+561 – a highly-red-shifted, gravitationally lensed quasar – will be presented as a link to earlier evolutionary stages of active galaxies and their hosts.     

Diagnostics of Ionized Gas in Galaxies with the “BPT–Radial Velocity Dispersion” Relation

In order to study the state of gas in galaxies, diagrams of the relation of optical emission line fluxes are used allowing one to separate main ionization sources: young stars in the HII regions, active galactic nuclei, and shock waves. In the intermediate cases, for example, when the contributions of radiation from OB stars and from shock waves mix, identification becomes uncertain, and the issue remains unresolved on what determines the observed state of the diffuse ionized gas (DIG) including the one on large distances fromthe galactic plane. Adding of an extra parameter—the gas velocity dispersion in the line-of-sight—to classical diagnostic diagrams helps to find a solution. In the present paper, we analyze the observed data for several nearby galaxies: for UGC10043 with the galactic wind, for the dwarf galaxies VIIZw403 andMrk 35 with star formation, for the galaxy Arp 212 with a polar ring. The data on the velocity dispersion are obtained at the 6-m SAO RAS telescope with the Fabry-Perot scanning interferometer, the information on the relation of main emission-line fluxes–from the published results of the integral-field spectroscopy (the CALIFA survey and the MPFS spectrograph). A positive correlation between the radial velocity dispersion and the contribution of shock excitation to gas ionization are observed. In particular, in studying Arp 212, our approach allowed us to confirm the assumption on a direct collision of gaseous clouds on the inclined orbits with the main disk of the galaxy.     

Elliptical Galaxies with Emission Lines from the Sloan Digital Sky Survey

As part of a study of star formation history along the Hubble sequence, we present here the results for 11 elliptical galaxies with strong nebular emission lines.After removing the dilution from the underlying old stellar populations by use of stellar population synthesis model,we derive the accurate fluxes of all the emission lines in these objects,which are then classified,using emission line ratios, into one Seyfert 2,six LINERs and four HII galaxies.We also identify one HII galaxy (A1216 04)as a hitherto unknown Wolf-Rayet galaxy from the presence of the Wolf- Rayet broad bump at 4650 (?).We propose that the star-forming activities in elliptical galaxies are triggered by either galaxy-galaxy interaction or the merging of a small satellite/a massive star cluster,as has been suggested by recent numerical simulations.     

Concordance of Kinematics and Lensing of Elliptical Galaxies with WMAP Cosmology

We explore degeneracies in strong lensing model so to make time delay data consistent with the WMAP (Wilkinson Microwave Anisotropy Probe) cosmology. Previous models using a singular isothermal lens often yield a time delay between the observed multiple images too small than the observed value if we "hardwire" the now widely quoted post-WMAP "high" value of the Hubble constant (H0 - 71 ± 4km s-1 Mpc-1). Alternatively, the lens density profile (star plus dark matter) is required to be locally steeper than r-2 (isothermal) profile near the Einstein radius (of the order 3 kpc) to fit the time delays; a naive extrapolation of a very steep profile to large radius would imply a lens halo with a scale length of the order only 3 kpc, too compact to be consistent with CDM. We explore more sophisticated, mathematically smooth, positive lens mass density profiles which are consistent with a large halo and the post-WMAP H0. Thanks to the spherical monopole degeneracy, the "reshuffling" of the mass in a lens model does not affect the quality of the fit to the image positions, amplifications, and image time delays. Even better, unlike the better-known mass sheet degeneracy, the stellar mass-to-light and the HO value are not affected either. We apply this monopole degeneracy to the quadruple imaged time-delay system PG1115 080. Finally we discuss the implications of the time delay data on the newly proposed relativistic MOND theory.     

A Study of Binary Stellar Population Synthesis of Elliptical Galaxies

We determined the relative stellar ages and metallicities of about 80 elliptical galaxies in both low and high density environments using the latest binary stellar population (BSP) synthesis model and tested the predictions of a recent hierarchical formation model that adopted the new ACDM cosmology. The stellar ages and metallicities were estimated from two high-quality published spectra line indices, the Hβand [MgFe] indices. The results show that the stellar populations of elliptical galaxies are older than 3.9 Gyr and more metal rich than 0.02. Most of our results are in agreement with the model predictions: (1) elliptical galaxies in denser environment are redder and have older populations than field galaxies; (2) elliptical galaxies with more massive stellar components are redder and have older and more metal rich populations than less massive ones; (3) the most massive galaxies have the oldest and most metal rich stars. However, some of our results differ from the model predictions on the metallicity distributions of low- and high-density elliptical galaxies and the dependence on the distance to the cluster center.     

Evidence for Stellar Streaming in the Cores of Elliptical Galaxies: A Kinematic Signature of Mergers?

We present evidence for non-Gaussian velocity fields within the cores of luminous elliptical galaxies. This evidence is based on high signal-to-noise ratio, medium-resolution spectroscopy of the cores of early-type members of the Virgo and Coma Clusters obtained with the Wisconsin-Indiana-Yale-NOAO 3.5 m telescope. The Virgo data were acquired using an integral-field unit (DensePak), which allows the velocity field to be sampled over a variety of spatial scales. The Coma data were obtained through single 2&arcsec; diameter fibers. The cross-correlation profiles of luminous elliptical galaxies show considerable structure, often having several features with amplitudes as high as 10% that of the cross-correlation peak itself. This structure is most obvious within a radius of 1&farcs;5 (at Virgo), or 相似文献   

An Infrared Photometric Study of Galaxies with Extragalactic H2O Maser Sources

All galaxies with extragalactic H_2O maser sources observed so far are collected. With the 2MASS and the IRAS photometric data an infrared study is performed on those galaxies.By a comparison between the H_2O maser detected sources and non-detected sources in the infrared it is indicated that infrared properties in the IRAS 12-25μm and 60-100μm are important for producing H_2O masers in galaxies.It is also found that the H_2O maser galaxies with different nuclear activity types have rather different infrared properties mainly in the IRAS 12-60μm region.     

Titan’s global crater population: A new assessment

We report a revised crater population for Titan using Cassini RADAR data through January 2010 (flyby T65), and make a size-dependent correction for the incomplete coverage (～33%) using a Monte-Carlo model. Qualitatively, Titan’s landscape is more heavily cratered than Earth, but much less than Mars or Ganymede: the area fraction covered by craters is in fact comparable with that of Venus. Quantitative efforts to interpret crater densities for Titan as surface age have been confounded by widely divergent crater production rates proposed in the literature. We elucidate the specific model assumptions that lead to these differences (assumed projectile density, scaling function for simple crater diameter, and complex crater size exponent) and suggest these are reasonable bounding models, with the Korycansky and Zahnle (2005) model representing a crater retention age of ～1 Ga, and the Artemieva and Lunine (2005) model representing a crater retention age of ～200 Ma. These estimates are consistent with models of Titan’s evolution that predict a thickening of its crust 0.3–1.2 Gyr ago.     

A catalog of early-type emission-line stars and Hα line profiles from LAMOST DR2

We present a catalog including 11 204 spectra of 10 436 early-type emission-line stars from LAMOST DR2, among which 9752 early-type emission-line spectra are newly discovered. For these earlytype emission-line stars, we discuss the morphological and physical properties of their low-resolution spectra. In this spectral sample, the Hα emission profiles display a wide variety of shapes. Based on the Hα line profiles, these spectra are categorized into five distinct classes: single-peak emission, single-peak emission in absorption, double-peak emission, double-peak emission in absorption, and P-Cygni profiles. To better understand what causes the Hα line profiles, we divide these objects into four types from the perspective of physical classification, which include classical Be stars, Herbig Ae/Be stars, close binaries and spectra contaminated by H II regions. The majority of Herbig Ae/Be stars and classical Be stars are identified and separated using a(H-K, K-W1) color-color diagram. We also discuss 31 binary systems that are listed in the SIMBAD on-line catalog and identify 3600 spectra contaminated by H II regions after cross-matching with positions in the Dubout-Crillon catalog. A statistical analysis of line profiles versus classifications is then conducted in order to understand the distribution of Hα profiles for each type in our sample. Finally, we also provide a table of 172 spectra with Fe II emission lines and roughly calculate stellar wind velocities for seven spectra with P-Cygni profiles.     

Interstellar colonization: A new parameter for the Drake equation?

M.H. Hart (1975, Quart. J. Roy. Astron. Soc.16, 128–135) has argued that the absence of evidence for extraterrestrial visits to Earth indicates that there are no other advanced civilizations in our galaxy capable of interstellar colonization. If so, the possible success of any SETI program must be questioned. The authors propose that limited interstellar colonization may occur and an attempt is made to show the effects of such a journey on the Drake equation.     

A catalog of cosmic gamma-ray bursts detected by the PHEBUS instrument on the Granat observatory: October 1994–December 1996

We present the final part of the catalog of cosmic gamma-ray bursts (GRBs) observed in the PHEBUS experiment on the Granat orbiting astrophysical observatory. The first three parts of the catalog were published by Terekhov et al. (1994, 1995a) and Tkachenko et al. (1998). The fourth part contains information on 32 events recorded from October 1994 until December 1996. We give burst light curves in the energy range 100 keV to 1.6 MeV, integrated energy spectra, and information on the fluence and energy flux at the luminosity peak for energies above 100 keV. Over the entire period of its operation, the PHEBUS instrument detected 206 cosmic GRBs. The mean ?V/V_max? was 0.336±0.007. The mean hardness corresponding to the ratio of count numbers in the energy ranges 400–1000 and 100–400 keV is 0.428±0.018 for events with a duration shorter than 2 s and 0.231±0.004 for events with a duration longer than 2 s.     

A new look at the Martian “violet haze” problem II. “Blue clearing” in 1969

The 1969 apparition of Mars has been extensively observed by the International Planetary Patrol Program. Using this material, the distribution of “blue clearing” in phase angle has been examined for four Martian bright area-dark area pairs. Arabia-Syrtis Major showed a smooth variation with a maximum at opposition. Zephyria-Mare Cimmerium showed a similar behavior except for a period around 20° before opposition. Memnonia-Mare Sirenum showed a rather steady decline from 20° before opposition to 30δ after opposition, except for an increase around 11° after opposition. Xanthe-Nilokeras showed a rather erratic behavior.Arabia-Syrtis Major underwent a strong diurnal variation in blue clearing near opposition. Xanthe-Nilokeras showed a diurnal variation throughout the apparition nearly identical to that of Arabia-Syrtis Major near opposition. Mare Cimmerium and Mare Sirenum are not well suited for showing a diurnal variation.The systematic error in these data due to the effects of astronomical “seeing” is discussed quantitatively.     

A Machine Learning Made Catalog of FR-Ⅱ Radio Galaxies from the FIRST Survey

We present an independent catalog (FRIIRGcat) of 45,241 Fanaroff–Riley Type Ⅱ (FR-Ⅱ) radio galaxies compiled from the Very Large Array Faint Images of the Radio Sky at Twenty-centimeters (FIRST) survey and employed the deep learning method.Among them,optical and/or infrared counterparts are identified for 41,425 FR-Ⅱs.This catalog spans luminosities 2.63×10²²≤L_rad≤6.76×10²⁹W Hz^-1and redshifts up to z=5.01.The spectroscopic classification indicates that...     

Prospects of the “WSO-UV” Project for Star Formation Study in Nearby Dwarf Galaxies

In the present work we consider the questions of star formation and evolution of nearby dwarf galaxies. We describe the method of star formation history determination based on multicolor photometry of resolved stars and models of color-magnitude diagrams of the galaxies. We present the results of star formation rate determination and its dependence on age and metallicity for dwarf irregular and dwarf spheroidal galaxies in the two nearby galaxy groups M81 and Cen A. Similar age of the last episode of star formation in the central part of the M81 group and also unusually high level of metal enrichment in the several galaxies of the Cen A group are mentioned. We pay special attention to the consideration of perspectives of star formation study in nearby dwarf galaxies with he new WSO-UV observatory.     

A new component of cosmic rays?

Recent direct measurements of the energy spectra of the major mass components of cosmic rays have indicated the presence of a ‘kink’ in the region of 200 GeV per nucleon. The kink, which varies in magnitude from one element to another, is much sharper than predicted by our cosmic ray origin model in which supernova remnants are responsible for cosmic ray acceleration and it appears as though a new, steeper component is responsible.The component amounts to about 20 percent of the total at 30 GeV/nucleon for protons and helium nuclei and its magnitude varies with nuclear charge; the unweighted fraction for all cosmic rays being 36%.The origin of the new component is subject to doubt but the contenders include O, B, A, supergiant and Wolf-Rayet stars, by way of their intense stellar winds. Another explanation is also in terms of these particles as the sources but then being trapped, and even further accelerated, in the Local Bubble.     

Automated Separation of Stars and Normal Galaxies Based on Statistical Mixture Modeling with RBF Neural Networks

For LAMOST, the largest sky survey program in China, the solution of the problem of automatic discrimination of stars from galaxies by spectra has shown that the results of the PSF test can be significantly refined. However, the problem is made worse when the redshifts of galaxies are not available. We present a new automatic method of star/(normal) galaxy separation, which is based on Statistical Mixture Modeling with Radial Basis Function Neural Networks (SMM-RBFNN). This work is a continuation of our previous one, where active and non-active celestial objects were successfully segregated. By combining the method in this paper and the previous one, stars can now be effectively separated from galaxies and AGNs by their spectra-a major goal of LAMOST, and an indispensable step in any automatic spectrum classification system. In our work, the training set includes standard stellar spectra from Jacoby's spectrum library and simulated galaxy spectra of EO, SO, Sa, Sb types with redshift ranging from 0 to 1     

Vorontsov-Vel’yaminov’s rows in giant spiral galaxies: Geometrical properties and physical interpretation

A phenomenon discovered by Vorontsov-Vel’yaminov — straight segments in the spiral structure of giant galaxies — is studied. The main geometrical and physical characteristics of these structures are demonstrated using the example of the galaxies M101 and especially M51. It is shown that rows alternate with regular spiral arms over almost their entire extent in M101, M51, and a number of other galaxies. The relationship between rows and straight warm dust lanes at the inner edges of spiral arms is traced. Assuming these dust lanes to be gas layers compressed by a spiral shock wave, the possibility that rows are formed in local segments of the spiral shock front that are being flattened is discussed. New observational facts about rows support the quantitative consequences of this gasdynamical picture. Translated from Astrofizika, Vol. 41. No. 4, pp. 609–622, October–December, 1998.     

Tidal gravitational forces: The infall of “new” comets and comet showers

The tidal gravitational field of the Galaxy directed into the galactic plane changes the angular momentum of comets in the Oort cloud. For comet orbits with semimajor axis greater than 2 × 10⁴ AU, the change of angular momentum in one orbit is sufficient to bring comets from the Oort cloud into the visible region, causing the infall of “new” comets. The limiting size orbit is weakly dependent on the angle between the major axis of the comet orbit and the galactic plane. The flux of comets into the inner Solar System caused by the galactic tidal field will be continuous and nearly isotropic. This effect appears to exclude any determination of the trajectories of passing stars by analysis of the angular distribution of new comets. The production of intense comet showers by the tidal field of a solar companion or of an interstellar cloud is considered. We show that the direction of a solar companion cannot be found from the present distribution of observable comets. The frequency of comet showers induced by encounters with interstellar clouds is found to be much lower than that from passing stars, and the tidal fields of interstellar clouds are not strong enough to cause comet showers of sufficient intensity to result in Earth impacts.