Galaxy And Mass Assembly (GAMA): 'No Smoking' zone for giant elliptical galaxies?

We study the radio emission of the most massive galaxies in a sample of dynamically relaxed and un-relaxed galaxy groups from Galaxy and Mass Assembly (GAMA). The dynamical state of the group is defined by the stellar dominance of the brightest group galaxy, e.g. the luminosity gap between the two most luminous members, and the offset between the position of the brightest group galaxy and the luminosity centroid of the group. We find that the radio luminosity of the most massive galaxy in the group strongly depends on its environment, such that the brightest group galaxies in dynamically young (evolving) groups are an order of magnitude more luminous in the radio than those with a similar stellar mass but residing in dynamically old (relaxed) groups. This observation has been successfully reproduced by a newly developed semi-analytic model which allows us to explore the various causes of these findings. We find that the fraction of radio loud brightest group galaxies in the observed dynamically young groups is ~2 times that in the dynamically old groups. We discuss the implications of this observational constraint on the central galaxy properties in the context of galaxy mergers and the super-massive blackhole accretion rate

Fossil Systems; a Multi-wavelength Approach towards Understanding Galaxy Formation

Fossil systems are understood to be the end product of galaxy mergers within groups and clusters. Their halo morphology points to their relaxed/virialised nature, thus allowing them to be employed as observational probes for the evolution of cosmic structures, their thermodynamics and dark matter distribution. Cosmological simulations, and their underlying models, are broadly consistent with the early formation epoch for fossils. In a series of studies we have looked into galaxy properties and intergalactic medium (IGM) in fossils, across a wide range of wavelengths, from X-ray through optical to the radio, to have a better understanding of their nature, the attributed halo age, IGM heating and their AGNs and use them as laboratories to constrain galaxy formation models. Adhering to one of less attended properties of fossils, using the the Millennium Simulation, we combine luminosity gap with luminosity segregation (the brightest galaxy offset from the group luminosity centroid) to identify the most dynamically relaxed galaxy groups which allows us to reveal brand new observational connections between galaxies and their environments

Morphological-based Analyses for Parameterizing Symmetry in Radio Galaxies

The morphology of radio galaxies can provide significant clues to describe the formation and evolution of galaxies in the Universe. Here, we aim to extract the morphological parameters of radio galaxies and define symmetry criteria as some of the essential factors of their shape explanations. We employed 67 radio galaxies, which include Fanaroff–Riley type 1 and type 2 galaxies, and their radio images from the FIRST and LoTSS surveys. We developed an automatic segmentation process to extract morphological properties such as the size of objects, eccentricity, and orientation of segmented regions from data sets. Using a maximum likelihood estimator, we show that the distributions of sizes follow a power-law function with exponents of −0.39 ± 0.06 and −0.55 ± 0.05 for the FIRST and LoTSS data, respectively. We found that type 2 radio galaxies have slightly lower eccentricities than type 1. We studied the relationships between size, eccentricity, and redshift in scatter plots. The size of galaxies (kpc ^2 ) demonstrates gently growing trends with increasing eccentricity in their scatter plots. We discussed the possible effect of the redshifts of the galaxies on this result. Depending on the number of segmented regions, we defined symmetry criteria based on proximity to the center of a galaxy in the optical band, eccentricity, orientation, and the quarter ( q ) of appearance in the image. We found that the mean symmetry obtained for two segmented regions that mainly emerged in two quarters via the condition of $| {q}^{{\prime} }-q^{\prime\prime} | =2$ has a higher value than those obtained for other cases

Exploring the Fundamental Mechanism in Driving Highest-Velocity Ionized Outflows in Radio AGNs

We investigate the ionized gas kinematics relationship with X-ray, radio and accreting properties using a sample of 348 nearby (z<0.4) SDSS-FIRST-X-ray detected AGNs. X-ray properties of our sample are obtained from XMM-Newton, Swift and Chandra observations. We unveil the ionized gas outflows in our sample manifested by the non-gravitational broad component in [O III]lambda 5007 angstrom emission line profiles. From the comparison of the correlation of non-parametric outflow velocities (i.e., the velocity width, the maximal velocity of outflow and line dispersion) with X-ray luminosity and radio luminosity, we find that outflow velocities have similarly positive correlations with both X-ray and radio luminosity. After correcting for the gravitational component, we find that the [O III] velocity dispersion normalized by stellar mass also increases with both X-ray luminosity and radio luminosity. We also find that, for a given X-ray (radio) luminosity, radio (X-ray) luminous AGNs have higher outflow velocities than non-radio (non-X-ray) luminous AGNs. Therefore, we find no clear preference between X-ray luminosity and radio luminosity in driving high-velocity ionized outflows and conclude that both AGN activity and small-scale jets contribute comparably. Moreover, there is no evidence that our obscured AGNs are preferentially associated with higher velocity outflows. Finally, we find a turning point around log(lambda(Edd)) similar or equal to -1.3 when we explore the dependency of outflow velocity on Eddington ratio. It can be interpreted considering the role of high radiation pressure (log(lambda(Edd)) greater than or similar to -1.3) in causing drastic reduction in the covering factor of the circumnuclear materials.Y

Exploring the Fundamental Mechanism in Driving Highest-Velocity Ionized Outflows in Radio AGNs

We investigate the ionized gas kinematics relationship with X-ray, radio and accreting properties using a sample of 348 nearby (z<0.4) SDSS-FIRST-X-ray detected AGNs. X-ray properties of our sample are obtained from XMM-Newton, Swift and Chandra observations. We unveil the ionized gas outflows in our sample manifested by the non-gravitational broad component in [O iii]λ5007Å emission line profiles. From the comparison of the correlation of non-parametric outflow velocities (i.e., the velocity width, the maximal velocity of outflow and line dispersion) with X-ray luminosity and radio luminosity, we find that outflow velocities have similarly positive correlations with both X-ray and radio luminosity. After correcting for the gravitational component, we find that the [O iii] velocity dispersion normalized by stellar mass also increases with both X-ray luminosity and radio luminosity. We also find that, for a given X-ray (radio) luminosity, radio (X-ray) luminous AGNs have higher outflow velocities than non-radio (non-X-ray) luminous AGNs. Therefore, we find no clear preference between X-ray luminosity and radio luminosity in driving high-velocity ionized outflows and conclude that both AGN activity and small-scale jets contribute comparably. Moreover, there is no evidence that our obscured AGNs are preferentially associated with higher velocity outflows. Finally, we find a turning point around log(λEdd)≃−1.3 when we explore the dependency of outflow velocity on Eddington ratio. It can be interpreted considering the role of high radiation pressure (log(λEdd)≳−1.3) in causing drastic reduction in the covering factor of the circumnuclear materials

LOFAR: Recent Imaging Results and Future Prospects

The Low-Frequency Array (LOFAR) is under construction in the Netherlands and in several surrounding European countries. In this contribution, we describe the layout and design of the telescope, with particular emphasis on the imaging characteristics of the array when used in its 'standard imaging' mode. After briefly reviewing the calibration and imaging software used for LOFAR image processing, we show some recent results from the ongoing imaging commissioning efforts. We conclude by summarizing future prospects for the use of LOFAR in observing the little-explored low-frequency Universe