Narrow-line Seyfert 1 galaxies (NLS1s) are a class of active galactic nuclei that are known to be one of the few sources of gamma-rays, which originate in a relativistic beamed jet. Because of their relatively large distance, a poorly investigated aspect of these jetted NLS1s is their environment, and in particular, their host galaxy. In this work, we present the results of a morphological analysis of the host galaxy of the jetted NLS1 IRAS 20181-2244 observed with the 6.5 m Baade Telescope of the Las Campanas Observatory. The GALFIT analysis run on the Ks image, along with additional spectroscopic observations performed with the Nordic Optical Telescope, clearly revealed the presence of an interacting system of two galaxies. The data suggest that this NLS1 is hosted by a late-type galaxy, although the result is not conclusive. This analysis, along with other results in the literature, might suggest that two populations of jetted NLS1 exist. Further morphological studies are needed to confirm or disprove this hypothesis.

We report observations of the hydrogen-deficient supernova (SN) 2019bkc/ATLAS19dqr. With B- and r-band decline between peak and 10 days post peak of Dm10 (B) = 5.24. 0.07 mag and Dm10 (r) = 3.85. 0.10 mag, respectively, SN.2019bkc is the most rapidly declining SN I discovered so far. While its closest matches are the rapidly declining SN.2005ek and SN. 2010X, the light curves and spectra of SN.2019bkc show some unprecedented characteristics. SN.2019bkc appears "hostless," with no identifiable host galaxy near its location, although it may be associated with the galaxy cluster MKW1 at z.=.0.02. We evaluate a number of existing models of fast-evolving SNe, and we find that none of them can satisfactorily explain all aspects of SN.2019bkc observations.

It has been often suggested that a tangible relation exists between relativistic jets in active galactic nuclei (AGN) and the morphology of their host galaxies. In particular, relativistic jets may commonly be related to merging events. Here we present for the first time a detailed spectroscopic and morphological analysis of a Seyfert galaxy, SDSS J211852.96-073227.5, at z=0.26. This source has previously been classified as a gamma-ray emitting narrow-line Seyfert 1 galaxy. We re-observed it with the 6.5 m Clay Telescope and these new, high-quality spectroscopic data have revealed that it is actually an intermediate-type Seyfert galaxy. Furthermore, the results of modelling the Ks-band near-infrared images obtained with the 6.5 m Baade Telescope indicate that the AGN is hosted by a late-type galaxy in an interacting system, strengthening the suggested connection between galaxy interactions and relativistic jets.

In this paper, we present the analysis of new radio and optical observations of the narrow-line Seyfert 1 galaxy Mrk 783. 1.6 GHz observations performed with the e-MERLIN interferometer confirm the presence of the diffuse emission previously observed. The Very Long Baseline Array (VLBA) also detects the nuclear source both at 1.6 GHz (L band) and 5 GHz (C band). While the L-band image shows only an unresolved core, the C-band image shows the presence of a partially resolved structure at a position angle of 60 degrees. The brightness temperature of the emission in both bands (>10(6) K) suggests that it is a pc-scale jet produced by the active galactic nucleus. The relatively steep VLBA spectral index (alpha(VLBA) = 0.63 +/- 0.03) is consistent with the presence of optically thin emission on milliarcsecond scales. Finally, we investigated two possible scenarios that can result in the misalignment between the kpc and pc-scale radio structure detected in the galaxy. We also analysed the optical morphology of the galaxy, which suggests that Mrk 783 underwent a merging in relatively recent times.

Context. Dorado is a nearby, rich and clumpy galaxy group that extends for several degrees in the southern hemisphere. Although several studies have been dedicated to defining its members, their kinematics, and the hot and cold gas content, in particular HI, their present star formation activity remains unknown.Aims. For the first time, we map the H alpha distribution as a possible indicator of the star formation activity of Dorado members, a large fraction of which show interaction and merging signatures independently of their morphological type.Methods. With the 2.5 m du Pont and the 1m Swope telescopes, we obtained narrow-band calibrated images of 14 galaxies that form the backbone of the group, mapping H alpha+[N II] down to a few 10(-17) erg cm(-2) s(-1) arcsec(-2). We estimated the galaxy star formation rate from the H alpha fluxes and corrected for Galaxy foreground extinction and [N II] contamination.Results. We detected H alpha+[N II] emission in all galaxies. HII regions clearly emerge in late-type galaxies, while in early-type galaxies the H alpha+[N II] emission is dominated by [N II], especially in the central regions. However, HII complexes are revealed in four early-type galaxies. Even in the compact group SGC 0414-5559, in the projected centre of Dorado, HII regions are found both throughout the late-type galaxies and in the very outskirts of early-type members. Considering the Dorado group as a whole, we notice that the H alpha+[N II] equivalent width, a measure of the specific star formation, increases with morphological type from early- to late-type members, although it remains lower than that observed in similar surveys of spiral galaxies. The star formation rate of the spiral members is in the range of what is observed in similar galaxies surveys (James et al., 2004). However, in three spiral galaxies, NGC 1536, PGC 75125, and IC 2058, the star formation rate is well below the median for their morphological classes. Conversely, the star formation rate of some early-type members tends to be higher than the average derived from H alpha+[N II] surveys of this morphological family.Conclusions. We detected H alpha+[N II] in all the early-type galaxies observed and half of them show HII regions in well-shaped rings as well as in their outskirts. These findings suggest that early-type galaxies in this group are not dead galaxies: their star formation has not yet shut down. Mechanisms such as gas stripping and gas accretion through galaxy-galaxy interaction seem relevant in modifying star formation in this evolutionary phase of Dorado.

Narrow-line Seyfert 1 (NLS1) galaxies are a peculiar sub-class of active galactic nuclei (AGNe). They have demonstrated that the presence of relativistic jets in an AGN is not strictly related to its radio-loudness, the black hole mass, or their host galaxy type. Here, we present a remarkable example of a radio-quiet NLS1, 6dFGS gJ035432.8-134008 (J0354-1340). In our Karl G. Jansky Very Large Array observations at 5.5 GHz, the source shows a bright core with a flat spectral index and extended emission corresponding to very elongated jets. These are the largest double-sided radio jets found to date in an NLS1, with a de-projected linear size of almost 250 kpc. We also analysed near-infrared and optical images obtained by the Magellan Baade and the European Southern Observatory New Technology Telescope. By means of photometric decomposition and colour maps, we determined that J0354-1340 is hosted by a spiral or disc-like galaxy. Fully evolved relativistic jets have traditionally been associated with high-mass elliptical galaxies hosting the most massive black holes. Instead, our results confirm that powerful jets can also be launched and sustained by less massive black holes in spiral galaxies, implying that the launching of the jets is governed by factors other than those previously believed to be at play.

We present radial velocities for 14 stars on the California and Carnegie Planet Search target list that reveal new companions. One star, HD 167665, was fit with a definitive Keplerian orbit leading to a minimum mass for the companion of 50.3 M-Jup at a separation from its host of similar to 5.5 AU. Incomplete or limited phase coverage for the remaining 13 stars prevents us from assigning to them unique orbital parameters. Instead, we fit their radial velocities with Keplerian orbits across a grid of fixed values for M sin i and period P, and use the resulting chi(2)(v) surface to place constraints on M sin i, P, and semimajor axis a. This technique allowed us to restrict M sin i below the brown dwarf- stellar mass boundary for an additional four companions ( HD 150554, HD 8765, HD 72780, HD 74014). If the combined five companions are confirmed as brown dwarfs, these results would comprise the first major catch of such objects from our survey beyond similar to 3 AU.

We study the structural evolution of massive galaxies by linking progenitors and descendants at a constant cumulative number density of n(c) = 1.4 x 10(-4) Mpc(-3) to z similar to 3. Structural parameters were measured by fitting Sersic profiles to high-resolution CANDELS HST WFC3 J(125) and H-160 imaging in the UKIDSS-UDS at 1 < z < 3 and ACS I-814 imaging in COSMOS at 0.25 < z < 1. At a given redshift, we selected the HST band that most closely samples a common rest-frame wavelength so as to minimize systematics from color gradients in galaxies. At fixed n(c), galaxies grow in stellar mass by a factor of similar to 3 from z similar to 3 to z similar to 0. The size evolution is complex: galaxies appear roughly constant in size from z similar to 3 to z similar to 2 and then grow rapidly to lower redshifts. The evolution in the surface mass density profiles indicates that most of the mass at r < 2 kpc was in place by z similar to 2, and that most of the new mass growth occurred at larger radii. This inside-out mass growth is therefore responsible for the larger sizes and higher Sersic indices of the descendants toward low redshift. At z < 2, the effective radius evolves with the stellar mass as r(e) proportional to M-2.0, consistent with scenarios that find dissipationless minor mergers to be a key driver of size evolution. The progenitors at z similar to 3 were likely star-forming disks with r(e) similar to 2 kpc, based on their low Sersic index of n similar to 1, low median axis ratio of b/a similar to 0.52, and typical location in the star-forming region of the U-V versus V-J diagram. By z similar to 1.5, many of these star-forming disks disappeared, giving rise to compact quiescent galaxies. Toward lower redshifts, these galaxies continued to assemble mass at larger radii and became the local ellipticals that dominate the high-mass end of the mass function at the present epoch.