We present H i synthesis imaging of the giant elliptical galaxy IC 1459 and its surroundings with the Australia Telescope Compact Array (ATCA). Our search for extended H i emission revealed a large complex of H i clouds near IC 1459, likely the debris from tidal interactions with neighbouring galaxies. The total H i mass (∼ 10 9 M ) in the detected clouds spans 250 kpc from the north-east of the gas-rich spiral NGC 7418A to the south-east of IC 1459. The extent and mass of the H i debris, which shows rather irregular morphology and kinematics, are similar to those in other nearby groups. Together with H i clouds recently detected near two other IC 1459 group members, namely IC 5270 and NGC 7418, using Phased-Array Feeds (PAFs) on the Australian Square Kilometer Array Pathfinder (ASKAP), the detected debris make up a significant fraction of the group's intergalactic medium.

The massive binary system WR 11 (γ 2 -Velorum) has been recently proposed as the counterpart of a Fermi source. If this association is correct, this system would be the second colliding wind binary detected in GeV γ-rays. However, the reported flux measurements from 1.4 to 8.64 GHz fail to establish the presence of non-thermal (synchrotron) emission from this source. Moreover, WR 11 is not the only radio source within the Fermi detection box. Other possible counterparts have been identified in archival data, some of which present strong non-thermal radio emission. We conducted arcsec-resolution observations towards WR 11 at very low frequencies (150 to 1400 MHz) where the non-thermal emission -if existent and not absorbed-is expected to dominate, and present a catalog of more than 400 radio-emitters, among which a significant part is detected at more than one frequency, including limited spectral index information. Twenty-one of them are located within the Fermi significant emission. A search for counterparts for this last group pointed at MOST 0808-471, a source 2' away from WR 11, as a promising candidate for high-energy emission, with resolved structure along 325 -1390 MHz. For it, we reprocessed archive interferometric data up to 22.3 GHz and obtained a non-thermal radio spectral index of −0.97 ± 0.09. However, multiwavelength observations of this source are required to establish its nature and to assess whether it can produce (part of) the observed γ-rays. WR 11 spectrum follows a spectral index of 0.74±0.03 from 150 MHz to 230 GHz, consistent with thermal emission. We interpret that any putative synchrotron radiation from the colliding-wind region of this relatively short-period system is absorbed in the photospheres of the individual components. Notwithstanding, the new radio data allowed to derive a mass loss rate of 2.5 × 10 −5 M yr −1 , which, according to the latest models for γ-ray emission in WR 11, would suffice to provide the required kinetic power to feed non-thermal radiation processes.

We present new H i data of the dwarf galaxy KK 69, obtained with the Giant Metrewave Radio Telescope (GMRT) with a signal-to-noise ratio that almost double previous observations. We carried out a Gaussian spectral decomposition and stacking methods to identify the cold neutral medium (CNM) and the warm neutral medium (WNM) of the H i gas. We found that 30% of the total H i gas, which corresponds to a mass of ∼10 7 M , is in the CNM phase. The distribution of the H i in KK 69 is not symmetric. Our GMRT H i intensity map of KK 69 overlaid onto a Hubble Space Telescope image reveals an offset of ∼4 kpc between the H i high-density region and the stellar body, indicating it may be a dwarf transitional galaxy. The offset, along with the potential truncation of the H i body, are evidence of interaction with the central group spiral galaxy NGC 2683, indicating the H i gas is being stripped from KK 69. Additionally, we detected extended H i emission of a dwarf galaxy member of the group as well as a possible new galaxy located near the north-eastern part of the NGC 2683 H i disk.

We present a collection of double-lobed sources towards a $20\,\mathrm{deg}^2$ area of the Cygnus region at the northern sky, observed at 325 and 610 MHz with the Giant Metrewave Radio Telescope. The 10 $^{\prime\prime}$ resolution achieved at 325 MHz is 5.5 times better than previous studies, while at 610 MHz, these are the first results ever of such a large area, mapped with 6 $^{\prime\prime}$ angular resolution. After a thorough visual inspection of the images at the two bands, we found 43 double-lobed source candidates, proposed as such due to the presence of 2 bright peaks, within a few arcminutes apart, joined by a bridge or a central nucleus. All but two are presented here as a double-lobed candidates for the first time. Thirty nine of the candidates were covered at both bands, and we provide the spectral index information for them. We have searched for positional coincidences between the detected sources/components and other objects from the literature, along the electromagnetic spectrum. Twenty-three candidates possess radio counterpart(s), 12 present infrared counterparts, and 1 showed an overlapping X-ray source. We analysed each candidate considering morphology, counterparts, and spectral indices. Out of the 43 candidates, 37 show characteristics compatible with an extragalactic nature, 2 of probably Galactic origin, 3 remain as dubious cases, though with feature(s) compatible with an extragalactic nature, and the remaining one, evidence of physically unrelated components. The median spectral index of the 40 putative extragalactic sources is $-1.0$ . Their celestial surface density at 610 MHz resulted in $1.9\,\mathrm{per\ deg}^2$ , across a region lying at the Galactic plane.

Context. Studies of the stellar and the H I gas kinematics in dwarf and low surface brightness (LSB) galaxies are essential for deriving constraints on their dark matter distribution. Moreover, a key component to unveil in the evolution of LSBs is to determine why some of them can be classified as superthin. Aims. We aim to investigate the nature of the proto-typical superthin galaxy Fourcade-Figueroa (FF) to understand the role played by the dark matter halo in forming its superthin shape and to investigate the mechanism that explains the observed disruption in the approaching side of the galaxy. Methods. Combining new H I 21 cm observations obtained with the Giant Metrewave Radio Telescope with archival data from the Australia Telescope Compact Array we were able to obtain sensitive H I observations of the FF galaxy. These data were modelled with a 3D tilted ring model in order to derive the rotation curve and surface brightness density of the neutral hydrogen. We subsequently used this model, combined with a stellar profile from the literature, to derive the radial distribution of the dark matter in the FF galaxy. Additionally, we used a more direct measurement of the vertical H I gas distribution as a function of the galactocentric radius to determine the flaring of the gas disk. Results. For the FF galaxy, the Navarro-Frenk-White dark matter distribution provides the best fit to the observed rotation curve. However, the differences with a pseudo-isothermal halo are small. Both models indicate that the core of the dark matter halo is compact. Even though the FF galaxy classifies as superthin, the gas thickness about the galactic centre exhibits a steep flaring of the gas that agrees with the edge of the stellar disk. In addition, FF is clearly disrupted towards its north-west side, clearly observed at optical and H I wavelengths. As suggested previously in the literature, the compact dark matter halo might be the main cause for the superthin structure of the stellar disk in FF. This idea is strengthened through the detection of the disruption; the fact that the galaxy is disturbed also appears to support the idea that it is not isolation that causes its superthin structure.

En general, los procesos que conducen a la evolución de las galaxias se pueden dividir en: internos, por ejemplo, eventos de formación estelar, supernovas y externos, por ejemplo, interacciónes de marea, barrido por presión cinética, fusiones. Las observaciones de hidrógeno neutro (HI) son una excelente herramienta para estudiar las interacciones entre galaxias o entre galaxias y su entorno. La línea de 21cm (HI) proporciona información espacial y cinemática del gas. Nos permite derivar la masa total del HI gas en una galaxia, estudiar las fases fría y tibia del medio interestelar y, además, señalar las ubicaciones de posibles regiones de formación estelar. Usando las observaciones de archivo del Autralia Telescope Compact Array y nuevas obtenidas con el Giant Metrewave Radio Telescope, analizamos galaxias que pertenecen a diferentes entornos. Estudiamos, en primer lugar, la región central del grupo de galaxias IC 1459. El grupo contiene alrededor de diez galaxias; la mayoría de ellas son galaxias de tipo tardío, pero la central, la cual da nombre al grupo, es una galaxia elíptica de tipo temprano. Nuestra búsqueda de emisión extendida de HI utilizando datos de archivo de ATCA reveló la presencia de un complejo de nubes cerca de la galaxia IC 1459. También, se observa en este grupo la distribución de morfología-densidad, siendo las galaxias NGC 5264 y NGC 7418A deficientes en HI. Proponemos entonces, que el complejo de nubes de HI se originó principalmente por las interacciones de mareas entre las galaxias IC 1459, NGC 5264 y NGC 7418A. Continuamos nuestra investigación estudiando la galaxia enana KK 69. Esta galaxia es parte de un pequeño grupo ubicado cerca de la región de baja densidad, Gemini-Leo. Encontramos un desplazamiento entre la región de alta densidad estelar observada en las imágenes ópticas, y la región de alta densidad del gas HI detectada con el GMRT. Propusimos que KK 69 es una galaxia enana de transición, que evoluciona de una galaxia enana rica en gas (enana irregular) a una enana pobre en gas (enana esferoidal). Por primera vez, en esta galaxia, se pudo llevar a cabo la descomposición del medio interestelar en las fases fría y tibia del gas neutro. Aproximadamente el 19% de la masa total del HI se encontró en la fase de fría; este valor excepcional es una característica común con la galaxia enana Leo T perteneciente al Grupo Local. Aunque la componente fría del gas es el combustible principal para el proceso de formación de estrellas, la galaxia no está formando estrellas en la actualidad. Terminamos nuestro proyecto estudiando la galaxia Fourcade-Figueroa, una galaxia espiral vista de canto, situada detrás del lóbulo sur de la galaxia Cen A. Combinamos los datos ATCA disponibles con las nuevas observaciones dedicadas en GMRT en el plano de visibilidades, definidas por las proyecciones de las líneas de conexión entre pares de antenas. El disco de la galaxia está deformado en la región noroeste de la galaxia. Modelamos la distribución de masa de la galaxia a partir de la curva de rotación obtenida con nuestros datos y encontramos que el halo de materia oscura que mejor ajusta es el de Navarro, Frenk y White.

Context. The γ-ray emitting source WISE J141046.00+740511.2 has been associated with a Fermi-LAT detection by crossmatching with Swift/XRT data. It has shown all the canonical observational characteristics of a BL Lac source, including a power-law, featureless optical spectrum. However, it was only recently detected at radio frequencies and its radio flux is significantly low. Aims. Given that a radio detection is fundamental to associate lower-energy counterparts to Fermi-LAT sources, we aim to unambiguously classify this source by performing a multiwavelength analysis based on contemporaneous data. Methods. By using multifrequency observations at the Jansky Very Large Array, Giant Metrewave Radio Telescope, Gran Telescopio Canarias, Gemini, William Herschel Telescope and Liverpool observatories, together with Fermi-LAT and Swift data, we carried out two kinds of analyses. On one hand, we studied several known parameters that account for the radio loudness or weakness characterization and their application to blazars (in general) and to our source (in particular). And, on the other hand, we built and analyzed the observed spectral energy distribution (SED) of this source to try to explain its peculiar characteristics. Results. The multiwavelength analysis indicates that WISE J141046.00+740511.2 is a blazar of the high-frequency peaked (HBL) type that emits highly polarized light and that is likely located at a low redshift. In addition, the one-zone model parameters that best fit its SED are those of an extreme HBL (EHBL); this blazar type has been extensively predicted in theory to be lacking in the radio emission that is otherwise typical of canonical γ-ray blazars. Conclusions. We confirm that WISE J141046.00+740511.2 is indeed a highly polarized BL Lac of the HBL type. Further studies will be conducted to explain the atypical low radio flux detected for this source.