W28-A possible association of supernova remnants and Hii regions

The nature of various components of the W28 complex region is investigated. The radio spectra of W28-A1 (G 6.4-0.2), M20 (G 7.0-0.2), W28-A2 (G 5.9-0.4), W28-A4 (G 5.3-1.1), KE59 (G 6.6-0.3) and G 6.4-0.5 are established over a wide range of frequencies. The W28-A1 (G 6.4-0.2) source is a SNR (sp. index –0.41), the M20, W28-A2 and KE59 seem to be thermal sources (sp. indexes –0.06, –0.15 and –0.04 respectively) whereas the W28-A4 and G 6.4-0.5 are possibly mixed sources containing thermal and non-thermal features. Certain physical parameters of the thermal components are derived by adopting a model. The physical properties of the W28-A1 SNR are investigated. The possibility of a SNR-Hii regions association in the W28 region is also discussed.     

The radio spectrum and physical parameters of the W80 Hii complex

The radio continuum spectrum of the W80 nebular complex (NGC 7000 and IC 5070 nebulae mainly) is established over a wide range of frequencies. The resultant spectrum shows a thermal shape and the spectral index established for the optically thin part of it is –0.04. Certain physical parameters of the complex (rms densities, mass, emission measure, excitation parameter) are derived for adopted models. The possible exciting star is located. Limitations of the models involved and uncertainties of the results are also discussed.     

New interstellar masers in nonmetastable ammonia

We report the astronomical detections of several ammonia inversion transitions involving nonmetastable levels with energies as high s 1090 K above the ground state. The (J, K) = (9, 6) inversion transition shows maser-like emission in the directions of W51, NGC 7538, W49, and DR 21(OH). The NH3 (6, 3) line exhibits similar characteristics in W51 but is seen in absorption in NGC 7538. These are the first definite detections of ammonia masers in space. The intensities and narrow line widths (0.5-1.5 km s-1) for the emission features are in contrast to the previously detected broad, weak, nonmetastable lines attributed to thermal emission in these sources. Temporal variability appears to be evident in the (9, 6) emission in W49 over a 4 month period. The highly excited (J, K) = (9, 6) and (6, 3) ammonia lines are found in regions containing compact H II regions and strong infrared sources with associated H2O and OH masers; i.e., in regions of active star formation.     

Integrated spectral properties of four previously unstudied small angular size galactic open clusters

We have derived fundamental parameters for the previously unstudied concentrated Galactic open clusters Berkeley 77, NGC2587, BH58 and ESO324‐SC15 by means of integrated spectroscopy in the range 3800–6800 Å. The cluster integrated spectra are compared with those of solar metallicity template spectra of Galactic open clusters with known parameters. The spectra were obtained at CASLEO (San Juan, Argentina) with a resolution of 14 Å.We estimated simultaneously age and foreground interstellar reddening by comparing the continuum distribution and line strengths of the cluster spectra with those of template spectra. Berkeley 77 was found to be an old cluster of 3–4 Gyr, while the remaining three clusters are between 400 and 1000 Myr old. The derived foreground reddening values range from E (B – V) = 0.0 in NGC2587 and ESO324‐SC15 to approximately 0.30 in Berkeley 77. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A classification of the available astrophysical data of particular Hii regions

A detailed classification of the available data on W3 is presented. Radio, optical and infrared maps of the object are shown in order of increasing angular resolution. The physical parameters and energy spectra of the various components of W3 and their sources are presented. A summary of the current theories on W3 is also included.     

BeppoSAX observations of the Seyfert 2 galaxies NGC 7172 and ESO 103-G35

We investigate the X-ray spectra of the type 2 Seyfert galaxies NGC 7172 and ESO 103-G35, using BeppoSAX observations, separated by approximately one year. We find that the X-ray spectra of both NGC 7172 and ESO 103-G35 can be well fitted using a power-law model with an Fe K α emission line at 6.4 keV. We did not find any statistically significant evidence for the existence of a reflection component in the X-ray spectra of these two galaxies. The continuum flux has decreased by a factor of approximately 2 during this period, in both objects. However, the spectral index as well as the absorption column have remained constant. We find weak evidence for the decrease of the normalization of the Fe K α emission line in a similar manner to the continuum in NGC 7172. We also report tentative evidence for a broad Fe K α line in agreement with previous ASCA observations. In contrast, in the case of ESO 103-G35 the line flux does not change while its width remains unresolved.     

The effects of a Comptonizing corona on the appearance of the reflection components in accreting black hole spectra

We discuss the effects of a Comptonizing corona on the appearance of the reflection components, and in particular of the reflection hump, in the X-ray spectra of accreting black holes. Indeed, in the framework of a thermal corona model, we expect that some (or even all, depending on the coronal covering factor) of the reflection features should cross the hot plasma, and thus suffer Compton scattering, before being observed. We have studied in detail the dependence of these effects on the physical (i.e. temperature and optical depth) and geometrical (i.e. inclination angle) parameters of the corona, concentrating on the slab geometry. Owing to the smoothing and shifting towards high energies of the Comptonized reflection hump, the main effects on the emerging spectra appear above 100 keV. We have also investigated the importance of such effects on the interpretation of the results obtained with the standard fitting procedures. We found that fitting Comptonization models, taking into account Comptonized reflection, by the usual cut-off power law + unComptonized reflection model may lead to an underestimation of the reflection normalization and an overestimation of the high-energy cut-off. We discuss and illustrate the importance of these effects by analysing recent observational results, such as those of the galaxy NGC 4258. We also find that the Comptonizing corona can produce and/or emphasize correlations between the reflection feature characteristics (like the iron line equivalent width or the covering fraction) and the X-ray spectral index, similar to those recently reported in the literature. We also underline the importance of these effects when dealing with accurate spectral fitting of the X-ray background.     

The radio spectra and physical parameters of some extended radio sources in monoceros

The radio spectra of the Rosette Nebula, the source S280 and the Monoceros Nebulosity are established over a wide range of frequencies. The radio spectra of the Rosette Nebula and S280, show a typical thermal shape. Physical parameters of both Hii regions are derived by adopting a spherical model.The radio spectrum of the Monoceros Nebulosity shows a non-thermal shape (sp. index –0.66) but the exact nature of the object is not clear. Assuming it is an SNR some of its physical characteristics are estimated.     

Low-temperature single crystal reflection spectra of forsterite

The infrared reflectivities of crystalline forsterite (Mg₂SiO₄) were measured for the temperature range 295–50 K for each crystal axis, between wavenumber 5000 and 100 cm⁻¹. The reflection spectra show clear dependence of temperature; most of the bands become more intense, sharper and their peak positions shift to higher wavenumber with decreasing temperature. Reflection spectra were fitted with dispersion formula of damped oscillator model of the dielectric constants and the oscillator parameters in the model were derived. The absorption spectra of forsterite particle are calculated with the derived dielectric constants to show that the forsterite features are good thermal indicator for cold temperature range below 295 K.     

Determination of physical parameters of NGC 2023 using the hyperfine NH3 spectrum

An improved approach is given for deriving the physical parameters of a molecular cloud by its NH₃ rotation-inversion hyperfine spectra. The optical depth τ₀(1, 1) of NH₃ (1,1) is obtained by considering the blending effect of the magnetic hyperfine spectral lines, the (1-1) excitation temperature T_ex (1, 1) is calculated by a two level model, the effect of different collision rate and the thermalization of the (1, 1) inversion lines are discussed, the rotation temperature T_R ( 2, 1) between the NH₃ levels (2, 2) and (1, 1) and the column density N( 1, 1) of the NH₃ (1, 1) inversion level are derived, the results of the total column density from different assumptions for the abundance ratio of ortho-NH₃ and para-NH₃ are also discussed.

This approach is used for the molecular cloud NGC 2023 by using the relevant observed data and its optical depth and other physical parameters are obtained.     

The Correlation between Optical Spectral Index and Continuum Luminosity Variation in the Seyfert 1 Galaxy NGC 5548

Using the archived optical spectra of NGC 5548 between 1989 and 2001, we derived the optical spectral index by fitting the spectra in wavelength windows unaffected by strong emission lines. We found that the index is anti-correlated with the continuum luminosity at 5100 A with a correlation coefficient of -0.8. Based on the standard thin accretion disk model, we investigated whether the correlation is related to the variations of the dimensionless accretion rate m (mass accretion rate in Eddington unit), or the inner radius of the accretion disk Rin, or both. The correlation can be modeled well using a co-variable mode of Rin/Rs = 12.5m-0.8 (Rs is Schwarzschild radius). As luminosity increases, m increases from 0.05 to 0.16 and at the same time Rin decreases from 133.9.RS to 55.5.RS, consistent with the prediction for a transition radius within which an ADAF structure exists. We concluded that the change of both inner accretion radius and the dimensionless accretion rate are key factors for the variation     

Revisiting the formation history of the minor-axis dust lane galaxy NGC 1947

In this paper, we present a detailed study of the peculiar early-type galaxy NGC 1947. The main goal of this work is to constrain the dynamical status and the formation history of NGC 1947 by comparing the observed properties with the predictions derived from different galaxy formation scenarios. To this aim, we derived the photometric and kinematical properties of NGC 1947. Due to the presence of an extended dust lane, which crosses the galaxy centre along the photometric minor axis, we used near-infrared (NIR) images ( J and K bands) to derive an accurate analysis of the stellar light distribution. Optical images (in the V and R bands) are used to derive the colour profiles and colour maps to study the structure of the dust lane. The observed kinematics confirm the presence of two components with decoupled angular momentum: gas and dust rotate along the minor axis, while the rotation velocities of the stars are observed along the major axis. The complex structure observed in NGC 1947 supports the hypothesis that some kind of interactions happened in the evolution of this object. We analysed two alternatives: a merging process and an accretion event. We discussed how the observed properties strongly suggest that the decoupled ring of gas and dust has been accreted from outside.     

Radio spectral changes in the haloes of galaxies seen edge-on

Results of a Monte-Carlo study of the one-dimensional propagation of cosmic-ray electrons in the galactic photon field are presented. The effect of a galactic wind on the change of the radio spectral index with height above the galactic plane is investigated in particular. The dependence of this relation on various physical quantities is also investigated. A comparison of the model results with the spectral index-height relation on NGC 4631 and NGC 891 strongly suggest that these two galaxies have dynamic haloes.     

Photometric study of the OB star clusters NGC 1502 and NGC 2169 and mass estimation of their members at the University Observatory Jena

In this work we present detailed photometric results of the trapezium like galactic nearby OB clusters NGC 1502 and NGC 2169 carried out at the University Observatory Jena. We determined absolute BVRI magnitudes of the mostly resolved components using Landolt standard stars. This multi colour photometry enables us to estimate spectral type and absorption as well as the masses of the components, which were not available for most of the cluster members in the literature so far, using models of stellar evolution. Furthermore, we investigated the optical spectrum of the components ADS 2984A and SZ Cam of the sextuple system in NGC 1502. Our spectra clearly confirm the multiplicity of these components, which is the first investigation of this kind at the University Observatory Jena (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Electron temperatures in W51 complex from high resolution,low frequency radio observations

W51 is a giant radio complex lying along the tangent to the Sagitarius arm at a distance of about 7 kpc from the Sun, with an extension of about 1° in the sky. It is divided into three components A, B, C where W51A and W51B consist of many compact HII regions while W51C is a supernova remnant. We have made continuum radio observations of these HII regions of the W51 complex at 240, 610, 1060 and 1400 MHz using GMRT with lower resolution (20″ × 15″) at the lowest frequency. The observed spectra of the prominent thermal subcomponents of W51 have been fitted to a free-free emission spectrum and their physical properties like electron temperatures and emission measures have been estimated. The electron temperatures from continuum spectra are found to be lower than the temperatures reported from radio recombination line (RRL) studies of these HII regions indicating the need for a filling factor even at this resolution. Also, the observed brightness at 240 MHz is found to be higher than expected from the best fits suggesting the need for a multicomponent model for the region.     

基于SDSS-DR8及2MASS数据的疏散星团NGC 6791的基本性质研究

利用斯隆数字巡天（SDSS）第8次释放数据（DR8）的恒星光谱数据及2MASS（Two Micro All Sky Survey）近红外点源测光数据研究著名的疏散星团NGC 6791,得到该星团的视向速度与金属丰度分别为V_r=-46.4±0.2 km·s^-1和[Fe/H]=0.32±0.11dex.利用星团中红团簇巨星作为理想"标准烛光",结合2MASS近红外点源测光数据计算了该星团的绝对距离模数为（m-M）₀=13.02±0.08 mag或4.02±0.15 kpc.与其他研究者给出的结果进行了比较,金属丰度、视向速度及绝对距离模数都符合得比较好.主要结论有3点:（1）NGC 6791是个极度富金属的星团;（2）在SDSS的光谱分辨能力以内,分离出的87颗团星之间不存在明显的金属丰度差异;（3）得到的距离模数对年龄、金属丰度及尘埃消光不敏感,是一种可靠的间接测量.     

Do LINER 2 galaxies harbour low-luminosity active galactic nuclei?

We use ROSAT HRI spatial data and ASCA spectral measurements for a sample of seven nearby, early-type spiral galaxies, to address the question of whether a low-luminosity active galactic nucleus (LLAGN) is present in galaxies that have a LINER 2 classification. The brightest discrete X-ray source in the ROSAT HRI observations is invariably found to be positionally coincident with the optical galactic nucleus, and in most cases its flux dominates the X-ray emission from the central region of the galaxy. All seven galaxies have X-ray spectra consistent with a two-component, soft thermal plus hard power-law, spectral form. If we exclude the two galaxies with relatively hard X-ray spectra, NGC 3628 and NGC 4594, for which there is supporting evidence for a LLAGN (or alternatively in the case of NGC 3628 a dominant ultraluminous X-ray binary), then the remaining galaxies show surprisingly similar X-ray spectral properties. Specifically the flux ratio F _X(0.5–1)/ F _X(2–5) , which measures the relative strengths of the thermal and non-thermal emission components, shows little scatter about a mean of 0.66, a value very similar to that measured in the classic starburst galaxy NGC 253. As there is no obvious reason why the luminosity of the hard power-law continuum emanating from a putative LLAGN should be very closely correlated with the thermal emission of the surrounding region, this suggests that that the broad-band (0.5–5 keV) X-ray emission from these LINER 2 galaxies may originate in a common set of processes probably associated with the starburst phenomenon. Conversely, it appears that in many LINER 2 galaxies and perhaps the majority, the nuclear X-ray luminosity does not derive directly from the presence of a LLAGN.     

NGC 3521: Stellar Counter-Rotation Induced by a Bar Component

The spiral galaxy NGC 3521 exhibits apparently normal kinematic properties of gas and stars along its major axis. However, the analysis of the LOSVD reveals strong asymmetries. A decomposition of the LOSVD data with a two-Gaussian component model shows two counter-rotating stellar components. The observed kinematic decoupling is interpreted as a projection effect induced by the presence of a bar component seen almost end on. The bar produces locally a greater concentration of retrograde stellar orbits but this does not relate to a specific counter-rotating population. The signatures of the bar are identified in the velocity field derived from long-slit spectra obtained along the major, minor and 45° intermediate axes and from R-band surface photometry. This revised version was published online in July 2006 with corrections to the Cover Date.     

The infrared emission of quasars

A model of two compact components (one contributes at radio and submillimeter wavelength and the other is very small and emits at the infrared region) is proposed to interpret the spectrum of quasi-stellar objects at radio and infrared wavelengths. The physical parameters are estimated from the observed data of 3C 273 for our model and for the model which is derived by assuming the infrared emission as an extrapolation of the synchrotron radio-source. It was proved that our model can explain the observational spectra, while the other model has some difficulties to interpret them completely.This work was partially supported by the Brasilian research agency CNPq     

Analysis of fundamental parameters for V477 Lyr

We analyze the photometric and spectroscopic observations of the young pre-cataclysmic variable (pre-CV) V477 Lyr. The masses of both binary components have been corrected by analyzing their radial velocity curves. We show that agreement between the theoretical and observed light curves of the object is possible for several sets of its physical parameters corresponding to the chosen temperature of the primary component. The final parameters of V477 Lyr have been established by comparing observational data with evolutionary tracks for planetary nebula nuclei. The derived effective temperature of the O subdwarf is higher than that estimated by analyzing the object’s ultraviolet spectra by more than 10000 K. This is in agreement with the analogous results obtained previously for the young pre-CVs V664 Cas and UU Sge. The secondary component of V477 Lyr has been proven to have a more than 25-fold luminosity excess compared to main-sequence stars of similar mass. Comparison of the physical parameters for the cool stars in young pre-CVs indicates that their luminosities do not correlate with the masses of the objects. The observed luminosity excesses in such stars show a close correlation with the post-common-envelope lifetime of the systems and should be investigated within the framework of the theory of their relaxation to the state of main-sequence stars.