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Context. The spiral structure of our Milky Way Galaxy is not yet known. HII regions and giant molecular clouds are the most prominent spiral tracers. Models with 2-4 arms have been proposed to outline the structure of our Galaxy.

Aims. Our purpose is to place firm observational constraints on the three most widely used theoretical models for the spatial configuration of the large-scale interstellar magnetic field in the Galactic disk, namely, the ring, the axisymmetric, and the bisymmetric field models.

Context. Evidence for a spectral flattening of the supernova remnant (SNR) HB3 (G132.7+1.3) was recently claimed in the literature based on previously published total flux density data, and the flattening was further interpreted as the discovery of thermal bremsstrahlung emission in the shell of HB3.

Context. S147 is a large faint shell-type supernova remnant (SNR) known for its remarkable spectral break at cm-wavelength, which is an important physical property to characterize SNR evolution. However, the spectral break is based on radio observations with limited precision.

Context.G156.2+5.7 is a large supernova remnant (SNR) first discovered in the ROSAT X-ray survey due to its exceptional high X-ray brightness. Subsequently detailed X-ray, optical and Hαstudies of this SNR were made, but radio observations are rare because of its low surface brightness and large size.

Context.Short time-scale radio variations of compact extragalactic radio sources, known as IntraDay Variability (IDV), can be explained in at least some sources by a source-extrinsic effect, in which the variations are interpreted as scintillation of radio waves caused by the turbulent interstellar medium of the Milky Way. One of the most convincing observational arguments in favour of propagation-induced variability is the so-called “annual modulation” of the characteristic variability time-scale, which is due to the orbital motion of the Earth. So far there are only two sources known which show such a well-defined seasonal cycle, a few more sources with fewer data can be regarded as possible candidates for this effect. However, source-intrinsic effects, such as structural variations, can also cause the observed changes of the variability time-scale. Data for the new, recently discovered, and highly variable IDV source J 1128+5925 are presented.

The region in which pulsars radiate is very important to constrain pulsar emission mechanisms. A three-dimensional (3D) method to calculate emission heights is developed in this paper. As an example, radiation regions for different components at different frequencies have been calculated for PSR B2111+46. Emission components at seven frequencies are fitted with Gaussian components, then the radiation heights for emission components are calculated. We found that different emission components, even if at the same radio frequency, are radiated from different heights. This is probably a common phenomena and challenges any emission mechanisms. The inverse Compton scattering emission model for pulsar radio emission can explain these results well.

Aims.Magnetic fields exist on all scales in our Galaxy. There is a controversy about whether the magnetic fields in molecular clouds are preserved from the permeated magnetic fields in the interstellar medium (ISM) during cloud formation. We investigate this controversy using available data in the light of the newly revealed magnetic field structure of the Galactic disk obtained from pulsar rotation measures (RMs).

Aims.Polarization measurements of the Galactic plane at λ6 cm probe the interstellar medium (ISM) to larger distances compared to measurements at longer wavelengths, enabling us to investigate properties of the Galactic magnetic fields and electron density.

Context.The relationship between the emission-line equivalent width and the continuum luminosity, called the Baldwin effect, is important for studies of the physics of the broad-line region of AGNs. Some recent studies have revealed the non-constant slope of the intrinsic Baldwin effect for several Seyfert 1 galaxies.

Radio continuum and polarization observations of the entire Cygnus Loop at λ6 cm wavelength were made with the Urumqi 25 m telescope. The λ6 cm map is analysed together with recently published maps from the Effelsberg 100 m telescope at λ21 cm and λ11 cm. The integrated flux density of the Cygnus Loop at λ6 cm is 90 ±9 Jy, which implies a spectral index of $\alpha=-0.40$±0.06. This rules out any global spectral steepening up to λ6 cm. However, small spectral index variations in some regions of the source are possible, but there are no indications for any spectral curvature. The linear polarization data at λ6 cm show percentage polarizations up to 35% in some areas of the Cygnus Loop, exceeding those observed at λ11 cm. The Rotation Measure is around -21 rad m-2in the southern area, which agrees with previous observations. However, the distribution of Rotation Measures is rather complex in the northern part of the Cygnus Loop, where the λ21 cm emission is totally depolarized. Rotation Measures based on λ11 cm and λ6 cm data are significantly larger than in the southern part. The difference in the polarization characteristics between the northern and southern part supports previous ideas that the Cygnus Loop consists of two supernova remnants.

An empirical relation between the broad line region (BLR) size and optical continuum luminosity is often adopted to estimate the BLR size and then the black hole mass of AGNs. However, optical luminosity may not be a good indicator of photoionizing luminosity for extremely radio-loud AGNs because the jets usually contribute significantly to the optical continuum. Therefore, the black hole masses derived for blazar-type AGNs with this method are probably overestimated. Here we first derived a tight empirical relation between the BLR size and the Hβemission line luminosity, $R({\rm light-days})= 24.05(L_{{\rm H}_\beta}/10^{42}$ergs s$^{-1})^{0.68}$, from a sample of 34 AGNs with the BLR size estimated with the reverberation mapping technique. Then we applied this relation to estimate the black hole masses of some AGNs and found that for many extremely radio-loud AGNs the black hole masses obtained with the $R-L_{\rm H_\beta}$relation are systematically lower than those derived previously with the $R-L_{5100~{\rm \AA}}$relation, while for radio-quiet and slightly radio-loud AGNs the results obtained with these two methods are almost the same. The difference of black hole masses estimated with these two relations increases with the radio-loudness for extremely radio-loud AGNs, which is consistent with the fact that their equivalent widths of the H$_{\beta}$emission line become smaller at greater radio-loudness. If the small H$_{\beta}$equivalent widths of extremely radio-loud  AGNs are indeed caused by the beaming effect, we argue that the optical emission line luminosity may be a better tracer of ionizing luminosity for blazar-type AGNs and the black hole masses derived with the $R-L_{{\rm H}_\beta}$relation are probably more accurate.

The low-frequency profiles of some pulsars manifest temporal broadening due to scattering, usually accompanied by flat polarization position angle (PA) curves. Assuming that the scattering works on the 4 Stokes parameters in the same way, we have simulated the effect of scattering on polarization profiles and find that the scattering can indeed flatten the PA curves. Since the higher-frequency profiles suffer less from scattering, they are convolved with scattering models to fit the observed low-frequency profiles. The calculated flat PA curves exactly reproduce the corresponding observations.

We estimated black hole masses for 9 Seyfert 1 and 13 Seyfert 2 galaxies in the Palomar and CfA bright Seyfert samples using the tight correlation between black hole mass and bulge velocity dispersion. Combining other 13 Seyfert 1s and 2 Seyfert 2s in these samples but with black hole masses measured recently by reverberation mapping and stellar/gas dynamics, we studied the correlations of black hole masses with radio-loudness and bulge luminosities for a sample of 37 Seyfert galaxies. We found that if radio-loudness is measured using the optical and radio luminosities of the nuclear components, the black hole masses of radio-loud Seyfert 1s tend to increase with the radio-loudness. The black hole masses of all Seyfert galaxies increase with the radio power, but Seyfert galaxies have larger radio powers than nearby galaxies with the same black hole masses. In addition, the correlation between black hole masses and bulge V-band luminosities for Seyfert galaxies is consistent with that found for quasars and normal galaxies. The combined sample of 37 Seyfert galaxies, 15 quasars and 30 normal galaxies suggests a possible universal nonlinear relation between black hole and bulge masses, ${M_{\rm BH} \propto M}_{\rm bulge}^{1.74 \pm 0.14}$, which is slightly steeper than that found recently by Laor ([CITE]) for a smaller sample. This nonlinear relation is supported by a larger sample including 65 Seyfert galaxies. The different ${M_{\rm BH}/ M}_{\rm bulge}$ratio for galaxies with different bulge luminosities or different black hole masses may be explained by this relation. These results are consistent with some theoretical implications and are important for understanding the nature of radio emissions and the formation and evolution of supermassive black holes and galaxies.

The shapes of pulse profiles, especially their variations with respect to observing frequencies, are very important to understand emission mechanisms of pulsars. However, no previous attempt has been made to interpret their complicated phenomenology. In this paper, we present theoretical simulations for the integrated pulse profiles and their frequency evolution within the framework of the inverse Compton scattering (ICS) model proposed by Qiao ([CITE]) and Qiao & Lin ([CITE]). Using the phase positions of the pulse components predicted by the "beam-frequency figure" of the ICS model, we present Gaussian fits to the multi-frequency pulse profiles for some pulsars. It is shown that the model can reproduce various types of the frequency evolution behaviors of pulse profiles observed.

Aims.We study the spectral and polarization properties of supernova remnants (SNRs) using our λ6 cm survey data.

Aims.We attempt to study spatial variations in the spectrum and rotation measures (RMs) of the large-diameter, high-latitude supernova remnant (SNR) CTA 1.

Context.Supernova remnants (SNRs) were often discovered in radio surveys of the Galactic plane. Because of the surface-brightness limit of previous surveys, more faint or confused SNRs await discovery. The Sino-German λ6 cm Galactic plane survey is a sensitive survey with the potential to detect new low-surface-brightness SNRs.

Context.Linear polarization of diffuse Galactic emission is a signature of magnetic fields in the interstellar medium of our Galaxy. Observations at high frequencies are less affected by Faraday depolarization than those at lower frequencies and are able to detect polarized emission from more distant Galactic regions.

Context. Linearly polarized Galactic synchrotron emission provides valuable information about the properties of the Galactic magnetic field and the interstellar magneto-ionic medium, when Faraday rotation along the line of sight is properly taken into account.Aims. We aim to survey the Galactic plane at λ6 cm including linear polarization. At such a short wavelength Faraday rotation effects are in general small and the Galactic magnetic field properties can be probed to larger distances than at long wavelengths.Methods. The Urumqi 25-m telescope is used for a sensitive λ6 cm survey in total and polarized intensities. WMAP K-band (22.8 GHz) polarization data are used to restore the absolute zero-level of the Urumqi Uand Qmaps by extrapolation.Results. Total intensity and polarization maps are presented for a Galactic plane region of $129\degr$≤$\ell$≤$230\degr$and |b| ≤$5\degr$in the anti-centre with an angular resolution of $9\farcm5$and an average sensitivity of 0.6 mK and 0.4 mK TBin total and polarized intensity, respectively. We briefly discuss the properties of some extended Faraday Screens detected in the λ6 cm polarization maps.Conclusions. The Sino-German λ6 cm polarization survey provides new information about the properties of the magnetic ISM. The survey also adds valuable information for discrete Galactic objects and is in particular suited to detect extended Faraday Screens with large rotation measures hosting strong regular magnetic fields.

Context. Linearly polarized Galactic synchrotron emission provides valuable information about the properties of the Galactic magnetic field and the interstellar magneto-ionic medium, when Faraday rotation along the line of sight is properly taken into account.Aims. We aim to survey the Galactic plane at λ6 cm including linear polarization. At such a short wavelength Faraday rotation effects are in general small and the Galactic magnetic field properties can be probed to larger distances than at long wavelengths.Methods. The Urumqi 25-m telescope is used for a sensitive λ6 cm survey in total and polarized intensities. WMAP K-band (22.8 GHz) polarization data are used to restore the absolute zero-level of the Urumqi Uand Qmaps by extrapolation.Results. Total intensity and polarization maps are presented for a Galactic plane region of 129° ≤$\ell$≤230° and |b| ≤5° in the anti-centre with an angular resolution of $9\farcm5$and an average sensitivity of 0.6 mK and 0.4 mK TBin total and polarized intensity, respectively. We briefly discuss the properties of some extended Faraday Screens detected in the λ6 cm polarization maps.Conclusions. The Sino-German λ6 cm polarization survey provides new information about the properties of the magnetic ISM. The survey also adds valuable information for discrete Galactic objects and is in particular suited to detect extended Faraday Screens with large rotation measures hosting strong regular magnetic fields.