Abstract. We present K-band imaging observations of ten Gamma-Ray Burst (GRB) host galaxies for which an optical and/or radio afterglow associated with the GRB event was clearly identified. Data were obtained with the Very Large Telescope and New Technology Telescope at ESO (Chile), and with the Gemini-North telescope at Mauna Kea (Hawaii). Adding to our sample nine other GRB hosts with K-band photometry and determined redshifts published in the literature, we compare their observed and absolute K magnitudes as well as their R − K colours with those of other distant sources detected in various optical, near-infrared, mid-infrared and submillimeter deep surveys. We find that the GRB host galaxies, most of them lying at 0.5 < ∼ z < ∼ 1.5, exhibit very blue colours, comparable to those of the faint blue star-forming sources at high redshift. They are sub-luminous in the K-band, suggesting a low stellar mass content. We do not find any GRB hosts harbouring R-and Kband properties similar to those characterizing the luminous infrared/submillimeter sources and the extremely red starbursts. Should GRBs be regarded as an unbiased probe of star-forming activity, this lack of luminous and/or reddened objects among the GRB host sample might reveal that the detection of GRB optical afterglows is likely biased toward unobscured galaxies. It would moreover support the idea that a large fraction of the optically-dark GRBs occur within dust-enshrouded regions of star formation. On the other hand, our result might also simply reflect intrinsic properties of GRB host galaxies experiencing a first episode of very massive star formation and characterized by a rather weak underlying stellar population. Finally, we compute the absolute B magnitudes for the whole sample of GRB host galaxies with known redshifts and detected at optical wavelengths. We find that the latter appear statistically even less luminous than the faint blue sources which mostly contributed to the B-band light emitted at high redshift. This indicates that the formation of GRBs could be favoured in particular systems with very low luminosities and, therefore, low metallicities. Such an intrinsic bias toward metal-poor environments would be actually consistent with what can be expected from the currently-favoured scenario of the "collapsar". The forthcoming launch of the SWIFT mission at the end of 2003 will provide a dramatic increase of the number of GRB-selected sources. A detailed study of the chemical composition of the gas within this sample of galaxies will thus allow us to further analyse the potential effect of metallicity in the formation of GRB events.

We report, as a part of a long-term study of infrared (IR) mergers and IR quasi-stellar objects (QSOs), detailed spectroscopic evidence for outflow (OF) and Wolf-Rayet (WR) features in the nearby mergers NGC 4038/39 and IRAS 23128−5919 (with low-velocity OF); and the nearby QSOs IRAS 01003−2238 and 13218+0552 (with extreme velocity OF, EVOF). We also study the presence of EVOF in a complete sample of ultraluminous IR galaxies and QSOs ('The IRAS 1-Jy Survey', 118 objects). We found EVOF in IRAS 11119+3257, 14394+5332, 15130−1958 and 15462−0450.The low-velocity OF components were detected mainly in objects with starburst processes, i.e. OF associated with galactic winds generated in multiple type II supernova (SN) explosions and massive stars. Meanwhile the EVOF were detected mainly in objects with strong starburst plus obscured IR QSOs; which suggests that the coexistence of both processes could generate EVOF.Hubble Space Telescope (HST) images of IR+BAL+Fe II QSOs show in practically all of these objects 'arc or shell' features probably associated with galactic winds [i.e. with multiple type II SN explosions or with starburst+active galactic nuclei (AGN)] or merger processes.In addition, we analyse the presence of Wolf-Rayet features in part of the large sample of bright PG-QSOs. We found possible WR features in the Fe II PG-QSOs PG 1244+026, 1444+407, 1448+273 and 1535+547.The results are discussed mainly within the framework of the composite scenario: starburst+AGN. We analyse the presence of extreme starburst and galactic winds as a possible link between IR mergers and IR QSOs. Finally, we discuss the probable role of mergers, extreme starburst and galactic winds processes in BAL-QSOs and galaxies in formation.

We report detailed evidence for: multiple merger, extended massive star formation, galactic-wind and circular/non-circular motions in the luminous infrared galaxy NGC 3256. Based on observation of high resolution imaging (obtained at HST and ESO-NTT), and extensive kinematical/spectroscopic data (more than 1000 spectra, collected at Bosque Alegre, CASLEO, CTIO and IUE Observatories).We find in a detailed morphological study (at ∼15 pc resolution) that the extended massive star formation process, detected previously in NGC 3256shows: (i) extended triple asymmetrical spiral arms structure (r ∼ 5 kpc); and (ii) the spiral arms emanate from three different nuclei. The main optical nucleus shows a small spiral-disk (r ∼ 500 pc) which is a continuation of the external one and reach the very nucleus. And this very nucleus shows blue elongate structure (63 pc × 30 pc), and luminous blue star cluster properties.We discuss this complex morphology, in the framework of an extended massive star formation driven by multiple merger process (Hernquist et al., Taniguchi et al.'s models).We study the kinematics of this system and present a detailed Hα velocity field for the central region (40 ′′ ×40 ′′ ; r max ∼30 ′′ ∼5 kpc); with a spatial resolution of 1 ′′ , and errors of ±15 km s −1 . The color and isovelocity maps show mainly: (i) a clear kinematical center of circular motion with "spider" shape and located between the main optical nucleus and the close (5 ′′ ) mid-IR knot/nucleus; (ii) non-circular motions in the external parts. In the main optical nucleus we found a clear "outflow component" associated to galactic-winds and a "inflow radial motion" (in the spiral-disk nuclear structure, r ∼700 pc). In addition, we detected the outflow component in the central and external regions

We report the discovery of Seyfert-2 galaxies in SDSS-DR8 with galaxy-wide, ultra-luminous narrow-line regions (NLRs) at redshifts z = 0.2 − 0.6. With a space density of 4.4 Gpc −3 at z ∼ 0.3, these "Green Beans" (GBs) are amongst the rarest objects in the Universe. We are witnessing an exceptional and/or short-lived phenomenon in the life cycle of AGN. The main focus of this paper is on a detailed analysis of the GB prototype galaxy J2240-0927 (z = 0.326). Its NLR extends over 26×44 kpc and is surrounded by an extended narrow-line region (ENLR). With a total [O iii]λ5008 luminosity of (5.7 ± 0.9) × 10 43 erg s −1 , this is one of the most luminous NLR known around any type-2 galaxy. Using VLT/XSHOOTER we show that the NLR is powered by an AGN, and we derive resolved extinction, density and ionization maps. Gas kinematics is disturbed on a global scale, and high velocity outflows are absent or faint. This NLR is unlike any other NLR or extended emission line region (EELR) known. Spectroscopy with Gemini/GMOS reveals extended, high luminosity [O iii] emission also in other GBs. WISE 24µm luminosities are 5 − 50 times lower than predicted by the [O iii] fluxes, suggesting that the NLRs reflect earlier, very active quasar states that have strongly subsided in less than a galaxies' light crossing time. These light echos, or ionization echos, are about 100 times more luminous than any other such echo known to date. X-ray data are needed for photo-ionization modeling and to verify the light echos.