We present a refinement of the optical morphologies for galaxies in the Catalog of Isolated Galaxies that forms the basis of the AMIGA (Analysis of the interstellar Medium of Isolated GAlaxies) project. Uniform reclassification using the digitized POSS II data benefited from the high resolution and dynamic range of that sky survey. Comparison with independent classifications made for an SDSS overlap sample of more than 200 galaxies confirms the reliability of the early vs. late-type discrimination and the accuracy of spiral subtypes within ∆T = 1-2. CCD images taken at the Observatorio de Sierra Nevada were also used to solve ambiguities in early versus late-type classifications. A considerable number of galaxies in the catalog (n = 193) are flagged for the presence of nearby companions or signs of distortion likely due to interaction. This most isolated sample of galaxies in the local Universe is dominated by two populations: 1) 82% are spirals (Sa-Sd) with the bulk being luminous systems with small bulges (63% between types Sb-Sc) and 2) a significant population of early-type E-S0 galaxies (14%). Most of the types later than Sd are low luminosity galaxies concentrated in the local supercluster where isolation is difficult to evaluate. The late-type spiral majority of the sample spans a luminosity range M B−corr = −18 to −22 mag. Few of the E/S0 population are more luminous than −21.0 marking the absence of the often-sought super L * merger (e.g. fossil elliptical) population. The rarity of high luminosity systems results in a fainter derived M * for this population compared to the spiral optical luminosity function (OLF). The E-S0 population is from 0.2 to 0.6 mag fainter depending on how the sample is defined. This marks the AMIGA sample as unique among samples that compare early and late-type OLFs separately. In other samples, which always involve galaxies in higher density environments, M * E/S0 is almost always 0.3-0.5 mag brighter than M * S , presumably reflecting a stronger correlation between M * and environmental density for early-type galaxies.

We perform a detailed photometric analysis (bulge–disc–bar decomposition and Concentration‐Asymmetry‐Clumpiness – CAS parametrization) for a well‐defined sample of isolated galaxies, extracted from the Catalog of Isolated Galaxies and reevaluated morphologically in the context of the Analysis of the interstellar Medium of Isolated GAlaxies project. We focus on Sb–Sc morphological types, as they are the most representative population among the isolated spiral galaxies. Our analysis yields a large number of important galactic parameters and various correlation plots are used to seek relationships that might shed light on the processes involved in determining those parameters. Assuming that the bulge Sérsic index and/or bulge/total luminosity ratios are reasonable diagnostics for pseudo‐ versus classical bulges, we conclude that the majority of late‐type isolated disc galaxies likely host pseudo‐bulges rather than classical bulges. Our parametrization of galactic bulges and discs suggests that the properties of the pseudo‐bulges are strongly connected to those of the discs. This may indicate that pseudo‐bulges are formed through internal processes within the discs (i.e. secular evolution) and that bars may play an important role in their formation. Although the sample under investigation covers a narrow morphological range, a clear separation between Sb and Sbc–Sc types is observed in various measures, e.g. the former are redder, brighter, have larger discs and bars, more luminous bulges, are more concentrated, more symmetric and clumpier than the latter. A comparison with samples of spiral galaxies (within the same morphological range) selected without isolation criteria reveals that the isolated galaxies tend to host larger bars, are more symmetric, less concentrated and less clumpy.

We present here the results of a Fourier photometric decomposition of a representative sample of ∼100 isolated CIG galaxies (Catalog of Isolated Galaxies) in the morphological range Sb–Sc. This study is an integral part of the AMIGA (Analysis of the Interstellar Medium of Isolated Galaxies) project. It complements the photometric analysis presented in our previous paper for the same sample of disc galaxies by allowing a description of the spiral structure morphology. We also estimate dynamical measures like torque strength for bar and spiral, and also the total non‐axisymmetric torque by assuming a constant mass‐to‐light ratio, and explore the interplay between the spiral and bar components of galaxies. Both the length (lbar) and the contrast (e.g. A2b) of the Fourier bars decrease along the morphological sequence Sb–Sbc–Sc, with bars in earlier types being longer and showing higher contrast. The bars of Sb galaxies are ∼three times longer than the bars in Sc types, consistent with our previous study. We find that the longer bars are not necessarily stronger (as quantified by the torque Qb measure), but longer bars show a higher contrast A2b, in very good agreement with theoretical predictions. Our data suggest that bar and spiral components are rather independent in the sense that the torque strengths of the two components are not correlated. The total strength Qg is a very reliable tracer of the bar strength measure Qb, the two quantities showing a very tight linear correlation. Comparison with a similar sample of disc galaxies (same morphological range) extracted from the OSUBGS (Ohio State University Bright Galaxy Survey) indicates that the isolated CIG/AMIGA galaxies host significantly longer Fourier bars and possibly show a different distribution of spiral torque Qs. The Fourier analysis also revealed a potential case of counterwinding spiral structure (KIG 652/NGC 5768), which deserves further kinematic study. We find that m= 2 (i.e. dominating two‐armed pattern) is the most common spiral arm multiplicity among the sample of Sb–Sc CIG/AMIGA galaxies (∼40 per cent), m= 2 and 3 and m= 1 and 2 are found in ∼28 and ∼13 per cent of isolated galaxies, respectively.

Abstract. X-ray observations of extragalactic radiosources show strong evidences of interaction between the radio emitting plasma and the X-ray emitting ambient gas. In this paper we perform a detailed study of this interaction by numerical simulations. We study the propagation of an axisymmetric supersonic jet in an isothermal King atmosphere and we analyze the evolution of the resulting X-ray properties and their dependence on the jet physical parameters. We show the existence of two distinct and observationally subsequent different regimes of interaction, with strong and weak shocks. In the first case shells of enhanced X-ray emission are to be expected, while in the second case we expect deficit of X-ray emission coincident with the cocoon. By a comparison between analytical models and the results of our numerical simulations, we discuss the dependence of the transition between these two regimes on the jet parameters and we find that the mean controlling quantity results to be the jet kinetic power. We then discuss how the observed jets can be used to constrain the jet properties.