We report the detection of the 1.3 mm continuum and the molecular emission of the disks of the young triple system SR24 by analyzing ALMA (The Atacama Large Millimeter/Submillimter Array) subarcsecond archival observations. We estimate the mass of the disks (0.025 M _☉ and 4 × 10⁻⁵ M _⊕ for SR24S and SR24N, respectively) and the dynamical mass of the protostars (1.5 M _☉ and 1.1 M _☉). A kinematic model of the SR24S disk to fit its C¹⁸O (2-1) emission allows us to develop an observational method to determine the tilt of a rotating and accreting disk. We derive the size, inclination, position angle, and sense of rotation of each disk, finding that they are strongly misaligned ( ) and possibly rotate in opposite directions as seen from Earth, in projection. We compare the ALMA observations with ¹²CO SMA archival observations, which are more sensitive to extended structures. We find three extended structures and estimate their masses: a molecular bridge joining the disks of the system, a molecular gas reservoir associated with SR24N, and a gas streamer associated with SR24S. Finally, we discuss the possible origin of the misaligned SR24 system, concluding that a closer inspection of the northern gas reservoir is needed to better understand it.

This paper is the second of a series of papers in which we are exploring the coevolution of galaxies and groups in the local Universe, by adopting a multiwavelength approach. Here, we present the photometric and kinematic characterization of two groups, USGC U268 and USGC U376 (U268 and U376 hereafter), which are located in different regions of the Leo cloud. We revisit the group membership, using results from recent redshift surveys, and we investigate their substructures. U268, which is composed of 10 catalogued members and 11 new added members, has a small fraction (≈24 per cent) of early-type galaxies (ETGs). U376 has 16 catalogued members plus eight new added members, with ≈38 per cent of ETGs. We find that there are significant substructures in both groups, which suggests that they are likely to be accreting galaxies. U268 is located in a more loose environment than U376. For each member galaxy, broad-band integrated and surface photometry have been obtained in far-ultraviolet (FUV) and near-ultraviolet (NUV) with the Galaxy Evolution Explorer (GALEX), and in the u, g, r, i and z (Sloan Digital Sky Survey) bands. Hα imaging and two-dimensional high-resolution kinematical data have been obtained using the scanning Fabry–Pérot interferometer (PUMA) at the 2.12-m telescope at San Pedro Mártir (Baja California, Mexico). We have improved the galaxy classification and we have detected morphological and kinematical distortions that might be connected either to ongoing and/or past interaction/accretion events or to environmental-induced secular evolution. U268 appears to be more active than U376, with a large fraction of galaxies showing interaction signatures (60 per cent versus 13 per cent). The presence of bars among late-type galaxies is ≈10 per cent in U268 and ≈29 per cent in U376. The cumulative distribution of the FUV–NUV colours of galaxies in U268 is significantly different from that in U376, with galaxies in U268 being bluer than those in U376. In the (FUV–r versus M_r) and (NUV–r versus M_r) planes, no members of U268 are found in the red sequence; even ETGs lie in the blue sequence, or in the ‘green valley’. Most (i.e. 80 per cent) of the early-type members in U376 inhabit the red sequence. A large fraction of galaxies, of different morphological types, are located in the green valley, while the blue sequence is underpopulated compared with U268.

We study the consistency and convergence of smoothed particle hydrodynamics (SPH) as a function of the interpolation parameters, namely the number of particles N, the number of neighbors n, and the smoothing length h, using simulations of the collapse and fragmentation of protostellar rotating cores. The calculations are made using a modified version of the GADGET-2 code that employs an improved scheme for the artificial viscosity and power-law dependences of n and h on N, as was recently proposed by Zhu et al., which comply with the combined limit , , and with for full SPH consistency as the domain resolution is increased. We apply this realization to the “standard isothermal test case” in the variant calculated by Burkert & Bodenheimer and the Gaussian cloud model of Boss to investigate the response of the method to adaptive smoothing lengths in the presence of large density and pressure gradients. The degree of consistency is measured by tracking how well the estimates of the consistency integral relations reproduce their continuous counterparts. In particular, C ⁰ and C ¹ particle consistency is demonstrated, meaning that the calculations are close to second-order accuracy. As long as n is increased with N, mass resolution also improves as the minimum resolvable mass . This aspect allows proper calculation of small-scale structures in the flow associated with the formation and instability of protostellar disks around the growing fragments, which are seen to develop a spiral structure and fragment into close binary/multiple systems as supported by recent observations.

Astronomy & Astrophysics (A&A) is an international journal which publishes papers on all aspects of astronomy and astrophysics

In this work we present scanning Fabry-Perot H$alpha$ observations of the isolated interacting galaxy pair NGC 5278/79 obtained with the PUMA Fabry-Perot interferometer. We derived velocity fields and rotation curves for both galaxies. For NGC 5278 we also obtained the residual velocity map to investigate the non-circular motions, and estimated its mass by fitting the rotation curve with a disk+halo components. We test three different types of halo (pseudo-isothermal, Hernquist and Navarro Frenk White) and obtain satisfactory fits to the rotation curve for all profiles. The amount of dark matter required by pseudo-isothermal profile is about ten times smaller than, that for the other two halo distributions. Finally, our kinematical results together with the analysis of dust lanes distribution and of surface brightness profiles along the minor axis allowed us to determine univocally that both components of the interacting pair are trailing spirals.