Anomalous gas in ESO 149-G003 : a MeerKAT-16 view

ESO 149-G003 is a close-by, isolated dwarf irregular galaxy. Previous observations with the ATCA indicated the presence of anomalous neutral hydrogen (⁠HI⁠) deviating from the kinematics of a regularly rotating disc. We conducted follow-up observations with the MeerKAT radio telescope during the 16-dish Early Science programme as well as with the MeerLICHT optical telescope. Our more sensitive radio observations confirm the presence of anomalous gas in ESO 149-G003, and further confirm the formerly tentative detection of an extraplanar HI component in the galaxy. Employing a simple tilted-ring model, in which the kinematics is determined with only four parameters but including morphological asymmetries, we reproduce the galaxy’s morphology, which shows a high degree of asymmetry. By comparing our model with the observed HI⁠, we find that in our model, we cannot account for a significant (but not dominant) fraction of the gas. From the differences between our model and the observed data cube, we estimate that at least 7–8 per cent of the HI in the galaxy exhibits anomalous kinematics, while we estimate a minimum mass fraction of less than 1 per cent for the morphologically confirmed extraplanar component. We investigate a number of global scaling relations and find that, besides being gas-dominated with a neutral gas-to-stellar mass ratio of 1.7, the galaxy does not show any obvious global peculiarities. Given its isolation, as confirmed by optical observations, we conclude that the galaxy is likely currently acquiring neutral gas. It is either re-accreting gas expelled from the galaxy or accreting pristine intergalactic material.http://mnras.oxfordjournals.orghj2022Physic

Anomalous gas in ESO 149-G003: A MeerKAT-16 view

ESO 149-G003 is a close-by, isolated dwarf irregular galaxy. Previous observations with the ATCA indicated the presence of anomalous neutral hydrogen (H I) deviating from the kinematics of a regularly rotating disc. We conducted follow-up observations with the MeerKAT radio telescope during the 16-dish Early Science programme as well as with the MeerLICHT optical telescope. Our more sensitive radio observations confirm the presence of anomalous gas in ESO 149-G003, and further confirm the formerly tentative detection of an extraplanar H I component in the galaxy. Employing a simple tilted-ring model, in which the kinematics is determined with only four parameters but including morphological asymmetries, we reproduce the galaxy's morphology, which shows a high degree of asymmetry. By comparing our model with the observed H I, we find that in our model, we cannot account for a significant (but not dominant) fraction of the gas. From the differences between our model and the observed data cube, we estimate that at least 7-8 per cent of the H I in the galaxy exhibits anomalous kinematics, while we estimate a minimum mass fraction of less than 1 per cent for the morphologically confirmed extraplanar component

Recent updates on the Maser Monitoring Organisation

The Maser Monitoring Organisation (M2O) is a research community of telescope operators, astronomy researchers and maser theoreticians pursuing a joint goal of reaching a deeper understanding of maser emission and exploring its variety of uses as tracers of astrophysical events. These proceedings detail the origin, motivations and current status of the M2O, as was introduced at the 2021 EVN symposium

A radio and near-infrared study of 6.7 GHz methanol maser sources

Thesis (Ph.D. (Physics)--North-West University, Potchefstroom Campus, 2004.The 6.7 GHz 51 - 60 A+ methanol maser transition was discovered relatively recently, in 1991. The exact nature of these masers is not known to date, but it seems likely that they are closely associated with high mass stars (M ≥ 10 Mo) in their earliest stages of evolution. Since the molecular cloud is optically thin to emission at radio wavelengths, the methanol masers can provide information about conditions deep in the star formation region. Twelve southern 6.7 GHz methanol maser sources were imaged in the near infrared (NIR) at I, J, H and K bands using the 1.5-m telescope at the Cerro Tololo Interamerican Observatory (Chile). Astrometry accurate to 0.5 arcsec and photometry down to a limiting magnitude of 14 was obtained. The positions of known H 11 regions, water masers, hydroxyl masers and mid- and far-infrared objects in the region are examined in order to try to determine the nature of the methanol maser sources. Seven out of 14 methanol maser sites were found to be within 8 kAU of a NIR source with colours characteristic of a deeply embedded source. In three cases, no NIR source, H 11 region, water maser or hydroxyl maser could be found in likely association with the methanol masers, leaving the methanol maser as the only indication that star formation is taking place at these locations. An intensive programme was started in January 1999 to monitor a sample of 56 sources at 6.7 GHz using the Hartebeesthoek 26-m telescope. The observations were taken at 1-2 week intervals, with daily observations when possible if a maser was seen to be varying rapidly. It was found that the majority of the sources have a significant level of variability. In addition, nine sources were found to have periodic or quasi-periodic variations. The source G9.62+0.20E was the first such source detected in the dataset, and is the first reported instance of a periodic maser associated with a star formation region. High-resolution images were obtained of the source G9.62+0.20E during a flare in 2001 using the Very Long Baseline Array (VLBA). The maser spots increased in intensity, with no changes to their morphology or relative positions during the flare. This indicates that the flare originated in an increase in radiation beyond the maser regions.Doctora

KAT-7 science verification: Cold gas, star formation, and substructure in the nearby Antlia Cluster

The Antlia Cluster is a nearby, dynamically young structure, and its proximity provides a valuable opportunity for detailed study of galaxy and group accretion on to clusters. We present a deep H I mosaic completed as part of spectral line commissioning of the Karoo Array Telescope (KAT-7), and identify infrared counterparts from the Widefield Infrared Survey Explorer extended source catalogue to study neutral atomic gas content and star formation within the cluster. We detect 37 cluster members out to a radius of ˜0.9 Mpc with M_{H I}>5× 10^7 M⊙. Of these, 35 are new H I detections, 27 do not have previous spectroscopic redshift measurements, and one is the Compton thick Seyfert II, NGC 3281, which we detect in H I absorption. The H I galaxies lie beyond the X-ray-emitting region 200 kpc from the cluster centre and have experienced ram pressure stripping out to at least 600 kpc. At larger radii, they are distributed asymmetrically suggesting accretion from surrounding filaments. Combining H I with optical redshifts, we perform a detailed dynamical analysis of the internal substructure, identify large infalling groups, and present the first compilation of the large-scale distribution of H I and star-forming galaxies within the cluster. We find that elliptical galaxy NGC 3268 is at the centre of the oldest substructure and argue that NGC 3258 and its companion population are more recent arrivals. Through the presence of H I and ongoing star formation, we rank substructures with respect to their relative time since accretion on to Antlia

Variability, flaring and coherence -- the complementarity of the maser and superradiance regimes

We discuss the role that coherence phenomena can have on the intensity variability of spectral lines associated with maser radiation. We do so by introducing the fundamental cooperative radiation phenomenon of (Dicke's) superradiance and discuss its complementary nature to the maser action, as well as its role in the flaring behaviour of some maser sources. We will consider examples of observational diagnostics that can help discriminate between the two, and identify superradiance as the source of the latter. More precisely, we show how superradiance readily accounts for the different time-scales observed in the multi-wavelength monitoring of the periodic flaring in G9.62+0.20E.Comment: 15 pages, 11 figure