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The relation between nuclear star clusters (NSCs) and the growth of the central SMBHs, as well as their connection to the properties of the host galaxies, is crucial for understanding the evolution of galaxies. Recent observations have revealed that about 10 per cent of nucleated galaxies host hybrid nuclei, consisting of both NSCs and accreting SMBHs that power active galactic nuclei (AGN). Motivated by the potential of the recently published multi-wavelength data sets from LeMMINGs survey, here we present the most thorough investigation to date of the incidence of hybrid nuclei in a large sample of 100 nearby nucleated galaxies (10 E, 25 S0, 63 S, and 2 Irr), covering a wide range in stellar mass (M∗,gal∼108.7−1012 Msun). We identify the nuclei and derive their properties by performing detailed 1D and 2D multi-component decompositions of the optical and near-infrared HST stellar light distributions of the galaxies using Sérsic and core-Sérsic models. Our AGN diagnostics are based on homogeneously derived nuclear 1.5 GHz e-MERLIN radio, Chandra X-ray (0.3--10 keV) and optical emission-line data. We determine the nucleation fraction (fnuc) as the relative incidence of nuclei across the LeMMINGs HST sample and find fnuc= 100/149 (= 67 ± 7 per cent), confirming previous work, with a peak value of 49/56~(= 88±13 per cent) at bulge masses M∗,bulge∼109.4- 1010.8 Msun. We identify 30 nucleated LeMMINGs galaxies that are optically active, radio-detected and X-ray luminous (LX>1039 erg s−1). This indicates that our nucleated sample has a lower limit ∼ 30 per cent occupancy of hybrid nuclei, which is a function of M∗,bulge and M∗,gal. We find that hybrid nuclei have a number density of (1.5±0.4)×10−5 Mpc−3.

Multiwavelength studies indicate that nuclear activity and bulge properties are closely related, but the details remain unclear. To study this further, we combine Hubble Space Telescope bulge structural and photometric properties with 1.5 GHz, e-MERLIN nuclear radio continuum data from the LeMMINGs survey for a large sample of 173 `active' galaxies (LINERs and Seyferts) and `inactive' galaxies (H IIs and absorption line galaxies, ALGs). Dividing our sample into active and inactive, they define distinct (radio core luminosity)−(bulge mass), L_R,core-M_*,bulge, relations, with a mass turnover at M_*, bulge ~ 10^(9.8 +- 0.3) M_sun (supermassive black hole mass M_BH ~ 10^(6.8 +- 0.3) M_sun), which marks the transition from AGN-dominated nuclear radio emission in more massive bulges to that mainly driven by stellar processes in low-mass bulges. None of our 10/173 bulgeless galaxies host an AGN. The AGN fraction increases with increasing M_*, bulge such that f_optical_AGN ∝ M_*,bulge^(0.24 +- 0.06) and f_radio_AGN ∝ M_*,bulge^(0.24 +- 0.05). Between M_*,bulge ~ 10^8.5 and 10^11.3 M_sun, f_optical_AGN steadily rises from 15 +- 4 to 80 +- 5 per cent. We find that at fixed bulge mass, the radio loudness, nuclear radio activity and the (optical and radio) AGN fraction exhibit no dependence on environment. Radio-loud hosts preferentially possess an early-type morphology than radio-quiet hosts, the two types are however indistinguishable in terms of bulge Sérsic index and ellipticity, while results on the bulge inner logarithmic profile slope are inconclusive. We finally discuss the importance of bulge mass in determining the AGN triggering processes, including potential implications for the nuclear radio emission in nearby galaxies.

The latest entry in the jetted active galactic nuclei (AGN) family is the Fanaroff-Riley type 0 (FR0) radio galaxies. They share several observational characteristics, e.g., nuclear emission and host galaxy morphology, with FR I sources; however, they lack extended, kiloparsec-scale radio structures, which are the defining features of canonical FR I and II sources. Here we report the identification of 7 gamma-ray emitting AGN as FR0 radio sources by utilizing the high-quality observations delivered by ongoing multi-wavelength wide-field sky surveys, e.g., Very Large Array Sky Survey. The broadband observational properties of these objects are found to be similar to their gamma-ray undetected counterparts. In the gamma-ray band, FR0 radio galaxies exhibit spectral features similar to more common FR I and II radio galaxies, indicating a common gamma-ray production mechanism and the presence of misaligned jets. Although the parsec-scale radio structure of FR0s generally exhibits a wide range, with about half having emission on opposite sides of the core, the gamma-ray detected FR0s tend to have dominant cores with core-jet structures. We conclude that dedicated, high-resolution observations are needed to unravel the origin of relativistic jets in this enigmatic class of faint yet numerous population of compact radio sources., Comment: ApJ, in press

Black hole driven outflows in galaxies hosting active galactic nuclei (AGN) may interact with their interstellar medium (ISM) affecting star formation. Such feedback processes, reminiscent of those seen in massive galaxies, have been reported recently in some dwarf galaxies. However, such studies have usually been on kiloparsec and larger scales and our knowledge on the smallest spatial scales to which these feedback processes can operate is unclear. Here we demonstrate radio jet$-$ISM interaction on the scale of an asymmetric triple radio structure of $\sim$ 10 parsec size in NGC 4395. This triple radio structure is seen in the 15 GHz continuum image and the two asymmetric jet-like structures are situated on either side of the radio core that coincides with the optical {\it Gaia} position. The high resolution radio image and the extended [OIII]$\lambda$5007 emission, indicative of an outflow, are spatially coincident and are consistent with the interpretation of a low power radio jet interacting with the ISM. Modelling of the spectral lines using {\tt MAPPINGS}, and estimation of temperature using optical integral field spectroscopic data suggest shock ionization of the gas. The continuum emission at 237 GHz, though weak, was found to spatially coincide with the AGN. However, the CO(2$-$1) line emission was found to be displaced by around 20 parsec northward of the AGN core. The spatial coincidence of molecular H$_2$$\lambda$2.4085 along the jet direction, the morphology of ionised [OIII]$\lambda$5007 and displacement of the CO(2$-$1) emission argues for conditions less favourable for star formation in the central $\sim$ 10 parsec region., Comment: 20 pages, 18 figures, accepted for the publication of The Astrophysical Journal

The excellent sensitivity and optimum resolution of LoTSS DR2 at 144 MHz has enabled us to discover a giant radio galaxy (J1225+4011) with three distinct episodes of jet activity, making it a member of a class of objects called triple-double radio galaxies (TDRGs). The source extends overall up to 1.35 Mpc in projected size, with the second episode extending to 572 kpc, and the inner episode to 118 kpc. J1225+4011 is only the fourth radio source showing a triple-double radio structure. All four sources have overall sizes greater than 700 kpc, making them giants. We also present the LoTSS 144 MHz map of the TDRG J0929+4146 and report its updated size. Lastly, we have summarised and discussed the radio properties of all TDRGs for the first time to understand their growth and evolution. Our observations suggest that the power of their jets may decrease with time., Comment: Accepted for publication in MNRAS Letters. 2 tables and 5 figures. Comments are welcome

We present a detailed multi-wavelength study of star formation in the dwarf galaxy NGC 4395 which hosts an active galactic nucleus (AGN). From our observations with the Ultra-Violet Imaging Telescope, we have compiled a catalogue of 284 star forming (SF) regions, out of which we could detect 120 SF regions in H$\alpha$ observations. Across the entire galaxy, we found the extinction corrected star formation rate (SFR) in the far ultra-violet (FUV) to range from 2.0 $\times$ 10$^{-5}$ M$_\odot$yr$^{-1}$ to 1.5 $\times$ 10$^{-2}$ M$_\odot$yr$^{-1}$ with a median of 3.0 $\times$ 10$^{-4}$ M$_\odot$yr$^{-1}$ and age to lie in the range of $\sim$ 1 to 98 Myr with a median of 14 Myr. In H$\alpha$ we found the SFR to range from 7.2 $\times$ 10$^{-6}$ M$_\odot$yr$^{-1}$ to 2.7 $\times$ 10$^{-2}$ M$_\odot$yr$^{-1}$ with a median of 1.7 $\times$ 10$^{-4}$ M$_\odot$yr$^{-1}$ and age to lie between 3 to 6 Myr with a median of 5 Myr. The stellar ages derived from H$\alpha$ show a gradual decline with galactocentric distance. We found three SF regions close to the center of NGC~4395 with high SFR both from H$\alpha$ and UV which could be attributed to feedback effects from the AGN. We also found six other SF regions in one of the spiral arms having higher SFR. These are very close to supernovae remnants which could have enhanced the SFR locally. We obtained a specific SFR (SFR per unit mass) for the whole galaxy 4.64 $\times$ 10$^{-10}$ yr$^{-1}$., Comment: 10 pages, 11 figures, Accepted for publication in ApJ

Multiwavelength studies indicate that nuclear activity and bulge properties are closely related, but the details remain unclear. To study this further, we combine $Hubble~Space~Telescope$ bulge structural and photometric properties with 1.5 GHz, $e$-MERLIN nuclear radio continuum data from the LeMMINGs survey for a large sample of 173 `active' galaxies (LINERs and Seyferts) and `inactive' galaxies (H IIs and absorption line galaxies, ALGs). Dividing our sample into active and inactive, they define distinct (radio core luminosity)$-$(bulge mass), L_R,core-M_*,bulge, relations, with a mass turnover at M_*, bulge ~ 10^(9.8 +- 0.3) M_sun (supermassive black hole mass M_BH ~ 10^(6.8 +- 0.3) M_sun), which marks the transition from AGN-dominated nuclear radio emission in more massive bulges to that mainly driven by stellar processes in low-mass bulges. None of our 10/173 bulgeless galaxies host an AGN. The AGN fraction increases with increasing M_*, bulge such that f_optical_AGN $\propto$ M_*,bulge^(0.24 +- 0.06) and f_radio_AGN $\propto$ M_*,bulge^(0.24 +- 0.05). Between M_*,bulge ~ 10^8.5 and 10^11.3 M_sun, f_optical_AGN steadily rises from 15 +- 4 to 80 +- 5 per cent. We find that at fixed bulge mass, the radio loudness, nuclear radio activity and the (optical and radio) AGN fraction exhibit no dependence on environment. Radio-loud hosts preferentially possess an early-type morphology than radio-quiet hosts, the two types are however indistinguishable in terms of bulge S\'ersic index and ellipticity, while results on the bulge inner logarithmic profile slope are inconclusive. We finally discuss the importance of bulge mass in determining the AGN triggering processes, including potential implications for the nuclear radio emission in nearby galaxies., Comment: 27 pages, 15 figures, 4 tables, accepted for publication in MNRAS

Multiwavelength studies indicate that nuclear activity and bulge properties are closely related, but the details remain unclear. To study this further, we combine Hubble Space Telescope bulge structural and photometric properties with 1.5 GHz, e-MERLIN nuclear radio continuum data from the LeMMINGs survey for a large sample of 173 `active' galaxies (LINERs and Seyferts) and `inactive' galaxies (H IIs and absorption line galaxies, ALGs). Dividing our sample into active and inactive, they define distinct (radio core luminosity)−(bulge mass), L_R,core-M_*,bulge, relations, with a mass turnover at M_*, bulge ~ 10^(9.8 +- 0.3) M_sun (supermassive black hole mass M_BH ~ 10^(6.8 +- 0.3) M_sun), which marks the transition from AGN-dominated nuclear radio emission in more massive bulges to that mainly driven by stellar processes in low-mass bulges. None of our 10/173 bulgeless galaxies host an AGN. The AGN fraction increases with increasing M_*, bulge such that f_optical_AGN ∝ M_*,bulge^(0.24 +- 0.06) and f_radio_AGN ∝ M_*,bulge^(0.24 +- 0.05). Between M_*,bulge ~ 10^8.5 and 10^11.3 M_sun, f_optical_AGN steadily rises from 15 +- 4 to 80 +- 5 per cent. We find that at fixed bulge mass, the radio loudness, nuclear radio activity and the (optical and radio) AGN fraction exhibit no dependence on environment. Radio-loud hosts preferentially possess an early-type morphology than radio-quiet hosts, the two types are however indistinguishable in terms of bulge Sérsic index and ellipticity, while results on the bulge inner logarithmic profile slope are inconclusive. We finally discuss the importance of bulge mass in determining the AGN triggering processes, including potential implications for the nuclear radio emission in nearby galaxies.

Multiwavelength studies indicate that nuclear activity and bulge properties are closely related, but the details remain unclear. To study this further, we combine Hubble Space Telescope bulge structural and photometric properties with 1.5 GHz, e-MERLIN nuclear radio continuum data from the LeMMINGs survey for a large sample of 173 ‘active’ galaxies (LINERs and Seyferts) and ‘inactive’ galaxies (H IIs and absorption line galaxies, ALGs). Dividing our sample into active and inactive, they define distinct (radio core luminosity)–(bulge mass), LR,core−M∗,bulge , relations, with a mass turnover at M∗,bulge∼109.8±0.3M⊙ (supermassive blackhole mass MBH∼106.8±0.3M⊙), which marks the transition from AGN-dominated nuclear radio emission in more massive bulges to that mainly driven by stellar processes in low-mass bulges. None of our 10/173 bulge-less galaxies host an AGN. The AGN fraction increases with increasing M∗,bulge such that foptical_AGN∝M0.24±0.06∗,bulge and fradio_AGN∝M0.24±0.05∗,bulge. Between M∗,bulge∼108.5 and 1011.3M⊙, foptical_AGN steadily rises from 15 ± 4 to 80 ± 5 per cent. We find that at fixed bulge mass, the radio loudness, nuclear radio activity, and the (optical and radio) AGN fraction exhibit no dependence on environment. Radio-loud hosts preferentially possess an early-type morphology than radio-quiet hosts, the two types are however indistinguishable in terms of bulge Sérsic index and ellipticity, while results on the bulge inner logarithmic profile slope are inconclusive. We finally discuss the importance of bulge mass in determining the AGN triggering processes, including potential implications for the nuclear radio emission in nearby galaxies. © 2023 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.

Multiwavelength studies indicate that nuclear activity and bulge properties are closely related, but the details remain unclear. To study this further, we combine Hubble Space Telescope bulge structural and photometric properties with 1.5 GHz, e-MERLIN nuclear radio continuum data from the LeMMINGs survey for a large sample of 173 `active' galaxies (LINERs and Seyferts) and `inactive' galaxies (H IIs and absorption line galaxies, ALGs). Dividing our sample into active and inactive, they define distinct (radio core luminosity)−(bulge mass), L_R,core-M_*,bulge, relations, with a mass turnover at M_*, bulge ~ 10^(9.8 +- 0.3) M_sun (supermassive black hole mass M_BH ~ 10^(6.8 +- 0.3) M_sun), which marks the transition from AGN-dominated nuclear radio emission in more massive bulges to that mainly driven by stellar processes in low-mass bulges. None of our 10/173 bulgeless galaxies host an AGN. The AGN fraction increases with increasing M_*, bulge such that f_optical_AGN ∝ M_*,bulge^(0.24 +- 0.06) and f_radio_AGN ∝ M_*,bulge^(0.24 +- 0.05). Between M_*,bulge ~ 10^8.5 and 10^11.3 M_sun, f_optical_AGN steadily rises from 15 +- 4 to 80 +- 5 per cent. We find that at fixed bulge mass, the radio loudness, nuclear radio activity and the (optical and radio) AGN fraction exhibit no dependence on environment. Radio-loud hosts preferentially possess an early-type morphology than radio-quiet hosts, the two types are however indistinguishable in terms of bulge Sérsic index and ellipticity, while results on the bulge inner logarithmic profile slope are inconclusive. We finally discuss the importance of bulge mass in determining the AGN triggering processes, including potential implications for the nuclear radio emission in nearby galaxies.

Narrow-line Seyfert 1 (NLSy1) galaxies are an enigmatic class of active galactic nuclei (AGN) that exhibit peculiar multiwavelength properties across the electromagnetic spectrum. For example, these sources have allowed us to explore the innermost regions of the central engine of AGN using X-ray observations and have also provided clues about the origin of relativistic jets considering radio and gamma-ray bands. Keeping in mind the ongoing and upcoming wide-field, multi-frequency sky surveys, we present a new catalogue of NLSy1 galaxies. This was done by carrying out a detailed decomposition of >2 million optical spectra of quasars and galaxies from the Sloan Digital Sky Survey Data Release 17 (SDSS-DR17) using the publicly available software "Bayesian AGN Decomposition Analysis for SDSS Spectra". The catalogue contains 22656 NLSy1 galaxies which is more than twice the size of the previously identified NLSy1s based on SDSS-DR12. As a corollary, we also release a new catalogue of 52273 broad-line Seyfert 1 (BLSy1) galaxies. The estimated optical spectral parameters and derived quantities confirm the previously known finding of NLSy1 galaxies being AGN powered by highly accreting, low-mass black holes. We conclude that this enlarged sample of NLSy1 and BLSy1 galaxies will enable us to explore the low-luminosity end of the AGN population by effectively utilizing the sensitive, high-quality observations delivered by ongoing/upcoming wide-field sky surveys. The catalogue has been made public at https://www.ucm.es/blazars/seyfert, Comment: MNRAS, in press

The orientation of the jet axis to the line of sight of the observer plays a major role in explaining the phenomena observed from blazars and radio galaxies. In the gamma-ray band, only a handful of radio galaxies have been identified, all being located in the nearby Universe (z<0.5). Here we report the identification of 4FGL J1435.5+2021, associated with TXS 1433+205, as a Fanaroff-Riley type II (FR II) radio galaxy at a considerably higher redshift of z=0.748, thereby making it the most distant gamma-ray detected radio galaxy known as of now. The Very Large Array Sky Survey data at 3 GHz resolves the source morphology into a bright core, a jet and two hotspots, with a total end-to-end projected length between lobe extremities of ~170 kpc. The optical and radio properties of this enigmatic object suggest it to be a high-excitation FR II radio galaxy. The multi-wavelength behaviour of TXS 1433+205 is found to be similar to other gamma-ray detected FR II sources but is at the high luminosity end. We suggest that the ongoing and upcoming high-resolution radio surveys will lead to the identification of many more high-redshift radio galaxies in the gamma-ray sky, thus allowing comprehensive studies of misaligned relativistic jets., Comment: MNRAS Letters, in press

We present for the first time a study of peculiar giant radio galaxy (GRG) J223301+131502 using deep multi-frequency radio observations from GMRT (323, 612, and 1300 MHz) and LOFAR (144 MHz) along with optical spectroscopic observations with the WHT~4.2m optical telescope. Our observations have firmly established its redshift of 0.09956 and unveiled its exceptional jet structure extending more than $\sim$ 200 kpc leading to a peculiar kink structure of $\sim$ 100 kpc. We measure the overall size of this GRG to be $\sim$ 1.83 Mpc; it exhibits lobes without any prominent hotspots and closely resembles a barbell. Our deep low-frequency radio maps clearly reveal the steep-spectrum diffuse emission from the lobes of the GRG. The magnetic field strength of $\sim$ 5 $\mu$G and spectral ages between about 110 to 200 mega years for the radio lobes were estimated using radio data from LOFAR 144 MHz observations and GMRT 323 and 612 MHz observations. We discuss the possible causes leading to the formation of the observed kink feature for the GRG, which includes precession of the jet axis, development of instabilities and magnetic reconnection. Despite its enormous size, the Barbell GRG is found to be residing in a low-mass (M$_{200} \sim 10^{14}$ $\rm M_{\odot}$) galaxy cluster. This GRG with two-sided large-scale jets with a kink and diffuse outer lobes residing in a cluster environment provides an opportunity to explore the structure and growth of GRGs in different environments., Comment: Accepted for publication in A&A. 17 Pages, 7 figures and 6 tables. Comments are welcome

Giant radio sources (GRSs) defined to be > 0.7 Mpc are the largest single objects in the Universe and can be associated with both galaxies (GRGs) and quasars (GRQs). They are important for understanding the evolution of radio galaxies and quasars whose sizes range from pc to Mpc scales and are also valuable probes of their environment. These radio-loud active galactic nuclei (RLAGN) interact with the interstellar medium of the host galaxy on small scales and the large-scale intracluster or intergalactic medium for the GRSs. With several new and sensitive surveys over the last few years, the number of known GRSs has increased many fold which has led a resurgence of interest in the field. This review article summarises our current understanding of these sources based on nearly five decades of research and discusses the importance of the Square Kilometer Array (SKA) in addressing some of the outstanding questions., Comment: Accepted for publication in the Journal of Astrophysics and Astronomy for Special Issue on Indian Participation in the SKA. Guest Editors: Abhirup Datta, Nirupam Roy, Preeti Kharb and Tirthankar Roy Choudhury). 31 pages, 8 figures, and 4 tables. Comments are welcome

This article gives a brief historical introduction and reviews our current understanding of jets in radio galaxies and quasars from an observational perspective, with an emphasis on observations at radio wavelengths. Recent results on the Fanaroff-Riley classification scheme, and the nature of radio structures and jets in the FR classes as well as in high-excitation and low-excitation radio galaxies are summarized. The collimation and propagation of jets from nuclear sub-pc to hundreds of kpc scales from both observatinoal and theoretical work have been discussed. The jets exhibit evidence of interaction with a clumpy interstellar medium, especially in young radio sources, and could trigger both star formation as well as suppress star formation depending on the physical conditions. Observational evidence for such interactions and jet feedback which have profound implications in our understanding of galaxy evolution have been presented. Recurrent jet activity which has been seen over a wide range of projected linear size and time scales has been discussed. This review article concludes with a brief discussion of unresolved questions on jets which new telescopes should help address., Comment: 30 pages, 14 figures, accepted for publication in the Journal of Astrophysics and Astronomy, Proceedings of the ARIES, Nainital, India conference on jets titled Astrophysical jets and observational facilities: National perspective; guest editors Shashi Pandey, Alok Gupta and Sachindra Naik

Giant radio quasars (GRQs) are radio-loud active galactic nuclei (AGNs), propelling megaparsec-scale jets. In order to understand GRQs and their properties, we have compiled all known GRQs ("the GRQ catalogue"), and a subset of small (size <700 kpc) radio quasars (SRQs) from the literature. In this process, we have found 10 new FR-II GRQs, in the redshift range of 0.66 < z < 1.72, which we include in the GRQ catalogue. Using the above samples, we have carried out a systematic comparative study of GRQs and SRQs, using optical and radio data. Our results show that the GRQs and SRQs statistically have similar spectral index and black hole mass distributions. However, SRQs have higher radio core power, core dominance factor, total radio power, jet kinetic power and Eddington ratio compared to GRQs. On the other hand, when compared to giant radio galaxies (GRGs), GRQs have higher black hole mass and Eddington ratio. The high core dominance factor of SRQs is an indicator of them lying closer to the line of sight than GRQs. We also find a correlation of the accretion disc luminosity with the radio core and jet power of GRQs, which provides evidence for disc-jet coupling. Lastly, we find the distributions of Eddington ratios of GRGs and GRQs to be bi-modal, similar to that found in small radio galaxies (SRGs) and SRQs, which indicate that size is not strongly dependent on the accretion state. Using all of these, we provide a basic model for the growth of SRQs to GRQs., Comment: Accepted for publication in Astronomy & Astrophysics. 9 figures, and 2 tables. This is the third paper in the series. Comments are welcome. "SAGAN Project website this http https://sites.google.com/site/anantasakyatta/sagan"

What determines the nuclear radio emission in local galaxies? We combine optical [O III] line emission, robust black hole (BH) mass estimates, and high-resolution e-MERLIN 1.5-GHz data, from the LeMMINGs survey, of a statistically-complete sample of 280 nearby, optically active (LINER and Seyfert) and inactive HII and Absorption line galaxies [ALG]) galaxies. Using [O III] luminosity ($L_{\rm [O~III]}$) as a proxy for the accretion power, local galaxies follow distinct sequences in the optical-radio planes of BH activity, which suggest different origins of the nuclear radio emission for the optical classes. The 1.5-GHz radio luminosity of their parsec-scale cores ($L_{\rm core}$) is found to scale with BH mass ($M_{\rm BH}$) and [O~III] luminosity. Below $M_{\rm BH} \sim$10$^{6.5}$ M$_{\odot}$, stellar processes from non-jetted HII galaxies dominate with $L_{\rm core} \propto M_{\rm BH}^{0.61\pm0.33}$ and $L_{\rm core} \propto L_{\rm [O~III]}^{0.79\pm0.30}$. Above $M_{\rm BH} \sim$10$^{6.5}$ M$_{\odot}$, accretion-driven processes dominate with $L_{\rm core} \propto M_{\rm BH}^{1.5-1.65}$ and $L_{\rm core} \propto L_{\rm [O~III]}^{0.99-1.31}$ for active galaxies: radio-quiet/loud LINERs, Seyferts and jetted HII galaxies always display (although low) signatures of radio-emitting BH activity, with $L_{\rm 1.5\, GHz}\gtrsim$10$^{19.8}$ W Hz$^{-1}$ and $M_{\rm BH}\gtrsim10^{7}$ M$_{\odot}$, on a broad range of Eddington-scaled accretion rates ($\dot{m}$). Radio-quiet and radio-loud LINERs are powered by low-$\dot{m}$ discs launching sub-relativistic and relativistic jets, respectively. Low-power slow jets and disc/corona winds from moderately high to high-$\dot{m}$ discs account for the compact and edge-brightened jets of Seyferts, respectively. Jetted HII galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties. [abridged], Comment: Accpeted for publication on MNRAS (27 pages, 9 Figures, 3 Tables, Appendix A)

What determines the nuclear radio emission in local galaxies? To address this question, we combine optical [O iii] line emission, robust black hole (BH) mass estimates, and high-resolution e-MERLIN 1.5-GHz data, from the LeMMINGs survey, of a statistically complete sample of 280 nearby optically active (LINER and Seyfert) and inactive [H ii and absorption line galaxies (ALGs)] galaxies. Using [O iii] luminosity ($L_{\rm [O\, \small {III}]}$) as a proxy for the accretion power, local galaxies follow distinct sequences in the optical–radio planes of BH activity, which suggest different origins of the nuclear radio emission for the optical classes. The 1.5-GHz radio luminosity of their parsec-scale cores (Lcore) is found to scale with BH mass (MBH) and [O iii] luminosity. Below MBH ∼ 106.5 M⊙, stellar processes from non-jetted H ii galaxies dominate with $L_{\rm core} \propto M_{\rm BH}^{0.61\pm 0.33}$ and $L_{\rm core} \propto L_{\rm [O\, \small {III}]}^{0.79\pm 0.30}$. Above MBH ∼ 106.5 M⊙, accretion-driven processes dominate with $L_{\rm core} \propto M_{\rm BH}^{1.5-1.65}$ and $L_{\rm core} \propto L_{\rm [O\, \small {III}]}^{0.99-1.31}$ for active galaxies: radio-quiet/loud LINERs, Seyferts, and jetted H ii galaxies always display (although low) signatures of radio-emitting BH activity, with $L_{\rm 1.5\, GHz}\gtrsim 10^{19.8}$ W Hz−1 and MBH ≳ 107 M⊙, on a broad range of Eddington-scaled accretion rates ($\dot{m}$). Radio-quiet and radio-loud LINERs are powered by low-$\dot{m}$ discs launching sub-relativistic and relativistic jets, respectively. Low-power slow jets and disc/corona winds from moderately high to high-$\dot{m}$ discs account for the compact and edge-brightened jets of Seyferts, respectively. Jetted H ii galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties. In conclusion, specific accretion–ejection states of active BHs determine the radio production and the optical classification of local

What determines the nuclear radio emission in local galaxies? To address this question, we combine optical [O iii] line emission, robust black hole (BH) mass estimates, and high-resolution e-MERLIN 1.5-GHz data, from the LeMMINGs survey, of a statistically complete sample of 280 nearby optically active (LINER and Seyfert) and inactive [H ii and absorption line galaxies (ALGs)] galaxies. Using [O iii] luminosity ($L_{\rm [O\, \small {III}]}$) as a proxy for the accretion power, local galaxies follow distinct sequences in the optical–radio planes of BH activity, which suggest different origins of the nuclear radio emission for the optical classes. The 1.5-GHz radio luminosity of their parsec-scale cores (Lcore) is found to scale with BH mass (MBH) and [O iii] luminosity. Below MBH ∼ 106.5 M⊙, stellar processes from non-jetted H ii galaxies dominate with $L_{\rm core} \propto M_{\rm BH}^{0.61\pm 0.33}$ and $L_{\rm core} \propto L_{\rm [O\, \small {III}]}^{0.79\pm 0.30}$. Above MBH ∼ 106.5 M⊙, accretion-driven processes dominate with $L_{\rm core} \propto M_{\rm BH}^{1.5-1.65}$ and $L_{\rm core} \propto L_{\rm [O\, \small {III}]}^{0.99-1.31}$ for active galaxies: radio-quiet/loud LINERs, Seyferts, and jetted H ii galaxies always display (although low) signatures of radio-emitting BH activity, with $L_{\rm 1.5\, GHz}\gtrsim 10^{19.8}$ W Hz−1 and MBH ≳ 107 M⊙, on a broad range of Eddington-scaled accretion rates ($\dot{m}$). Radio-quiet and radio-loud LINERs are powered by low-$\dot{m}$ discs launching sub-relativistic and relativistic jets, respectively. Low-power slow jets and disc/corona winds from moderately high to high-$\dot{m}$ discs account for the compact and edge-brightened jets of Seyferts, respectively. Jetted H ii galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties. In conclusion, specific accretion–ejection states of active BHs determine the radio production and the optical classification of local

What determines the nuclear radio emission in local galaxies? To address this question, we combine optical [O iii] line emission, robust black hole (BH) mass estimates, and high-resolution e-MERLIN 1.5-GHz data, from the LeMMINGs survey, of a statistically complete sample of 280 nearby optically active (LINER and Seyfert) and inactive [H ii and absorption line galaxies (ALGs)] galaxies. Using [O iii] luminosity ($L_{\rm [O\, \small {III}]}$) as a proxy for the accretion power, local galaxies follow distinct sequences in the optical–radio planes of BH activity, which suggest different origins of the nuclear radio emission for the optical classes. The 1.5-GHz radio luminosity of their parsec-scale cores (Lcore) is found to scale with BH mass (MBH) and [O iii] luminosity. Below MBH ∼ 106.5 M⊙, stellar processes from non-jetted H ii galaxies dominate with $L_{\rm core} \propto M_{\rm BH}^{0.61\pm 0.33}$ and $L_{\rm core} \propto L_{\rm [O\, \small {III}]}^{0.79\pm 0.30}$. Above MBH ∼ 106.5 M⊙, accretion-driven processes dominate with $L_{\rm core} \propto M_{\rm BH}^{1.5-1.65}$ and $L_{\rm core} \propto L_{\rm [O\, \small {III}]}^{0.99-1.31}$ for active galaxies: radio-quiet/loud LINERs, Seyferts, and jetted H ii galaxies always display (although low) signatures of radio-emitting BH activity, with $L_{\rm 1.5\, GHz}\gtrsim 10^{19.8}$ W Hz−1 and MBH ≳ 107 M⊙, on a broad range of Eddington-scaled accretion rates ($\dot{m}$). Radio-quiet and radio-loud LINERs are powered by low-$\dot{m}$ discs launching sub-relativistic and relativistic jets, respectively. Low-power slow jets and disc/corona winds from moderately high to high-$\dot{m}$ discs account for the compact and edge-brightened jets of Seyferts, respectively. Jetted H ii galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties. In conclusion, specific accretion–ejection states of active BHs determine the radio production and the optical classification of local

Giant radio quasars (GRQs) are radio-loud active galactic nuclei (AGNs), propelling megaparsec-scale jets. In order to understand GRQs and their properties, we have compiled all known GRQs ("the GRQ catalogue"), and a subset of small (size <700 kpc) radio quasars (SRQs) from the literature. In this process, we have found 10 new FR-II GRQs, in the redshift range of 0.66 < z < 1.72, which we include in the GRQ catalogue. Using the above samples, we have carried out a systematic comparative study of GRQs and SRQs, using optical and radio data. Our results show that the GRQs and SRQs statistically have similar spectral index and black hole mass distributions. However, SRQs have higher radio core power, core dominance factor, total radio power, jet kinetic power and Eddington ratio compared to GRQs. On the other hand, when compared to giant radio galaxies (GRGs), GRQs have higher black hole mass and Eddington ratio. The high core dominance factor of SRQs is an indicator of them lying closer to the line of sight than GRQs. We also find a correlation of the accretion disc luminosity with the radio core and jet power of GRQs, which provides evidence for disc-jet coupling. Lastly, we find the distributions of Eddington ratios of GRGs and GRQs to be bi-modal, similar to that found in small radio galaxies (SRGs) and SRQs, which indicate that size is not strongly dependent on the accretion state. Using all of these, we provide a basic model for the growth of SRQs to GRQs., Comment: Accepted for publication in Astronomy & Astrophysics. 9 figures, and 2 tables. This is the third paper in the series. Comments are welcome. "SAGAN Project website this http https://sites.google.com/site/anantasakyatta/sagan"

What determines the nuclear radio emission in local galaxies? We combine optical [O III] line emission, robust black hole (BH) mass estimates, and high-resolution e-MERLIN 1.5-GHz data, from the LeMMINGs survey, of a statistically-complete sample of 280 nearby, optically active (LINER and Seyfert) and inactive HII and Absorption line galaxies [ALG]) galaxies. Using [O III] luminosity ($L_{\rm [O~III]}$) as a proxy for the accretion power, local galaxies follow distinct sequences in the optical-radio planes of BH activity, which suggest different origins of the nuclear radio emission for the optical classes. The 1.5-GHz radio luminosity of their parsec-scale cores ($L_{\rm core}$) is found to scale with BH mass ($M_{\rm BH}$) and [O~III] luminosity. Below $M_{\rm BH} \sim$10$^{6.5}$ M$_{\odot}$, stellar processes from non-jetted HII galaxies dominate with $L_{\rm core} \propto M_{\rm BH}^{0.61\pm0.33}$ and $L_{\rm core} \propto L_{\rm [O~III]}^{0.79\pm0.30}$. Above $M_{\rm BH} \sim$10$^{6.5}$ M$_{\odot}$, accretion-driven processes dominate with $L_{\rm core} \propto M_{\rm BH}^{1.5-1.65}$ and $L_{\rm core} \propto L_{\rm [O~III]}^{0.99-1.31}$ for active galaxies: radio-quiet/loud LINERs, Seyferts and jetted HII galaxies always display (although low) signatures of radio-emitting BH activity, with $L_{\rm 1.5\, GHz}\gtrsim$10$^{19.8}$ W Hz$^{-1}$ and $M_{\rm BH}\gtrsim10^{7}$ M$_{\odot}$, on a broad range of Eddington-scaled accretion rates ($\dot{m}$). Radio-quiet and radio-loud LINERs are powered by low-$\dot{m}$ discs launching sub-relativistic and relativistic jets, respectively. Low-power slow jets and disc/corona winds from moderately high to high-$\dot{m}$ discs account for the compact and edge-brightened jets of Seyferts, respectively. Jetted HII galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties. [abridged], Comment: Accpeted for publication on MNRAS (27 pages, 9 Figures, 3 Tables, Appendix A)

What determines the nuclear radio emission in local galaxies? To address this question, we combine optical [O iii] line emission, robust black hole (BH) mass estimates, and high-resolution e-MERLIN 1.5-GHz data, from the LeMMINGs survey, of a statistically complete sample of 280 nearby optically active (LINER and Seyfert) and inactive [H ii and absorption line galaxies (ALGs)] galaxies. Using [O iii] luminosity ($L_{\rm [O\, \small {III}]}$) as a proxy for the accretion power, local galaxies follow distinct sequences in the optical–radio planes of BH activity, which suggest different origins of the nuclear radio emission for the optical classes. The 1.5-GHz radio luminosity of their parsec-scale cores (Lcore) is found to scale with BH mass (MBH) and [O iii] luminosity. Below MBH ∼ 106.5 M⊙, stellar processes from non-jetted H ii galaxies dominate with $L_{\rm core} \propto M_{\rm BH}^{0.61\pm 0.33}$ and $L_{\rm core} \propto L_{\rm [O\, \small {III}]}^{0.79\pm 0.30}$. Above MBH ∼ 106.5 M⊙, accretion-driven processes dominate with $L_{\rm core} \propto M_{\rm BH}^{1.5-1.65}$ and $L_{\rm core} \propto L_{\rm [O\, \small {III}]}^{0.99-1.31}$ for active galaxies: radio-quiet/loud LINERs, Seyferts, and jetted H ii galaxies always display (although low) signatures of radio-emitting BH activity, with $L_{\rm 1.5\, GHz}\gtrsim 10^{19.8}$ W Hz−1 and MBH ≳ 107 M⊙, on a broad range of Eddington-scaled accretion rates ($\dot{m}$). Radio-quiet and radio-loud LINERs are powered by low-$\dot{m}$ discs launching sub-relativistic and relativistic jets, respectively. Low-power slow jets and disc/corona winds from moderately high to high-$\dot{m}$ discs account for the compact and edge-brightened jets of Seyferts, respectively. Jetted H ii galaxies may host weakly active BHs. Fuel-starved BHs and recurrent activity account for ALG properties. In conclusion, specific accretion–ejection states of active BHs determine the radio production and the optical classification of local

We present the first results of a project called SAGAN, which is dedicated solely to the studies of relatively rare megaparsec-scale radio galaxies in the Universe, called giant radio galaxies (GRGs). We have identified 162 new GRGs primarily from the NVSS with sizes ranging from ~0.71 Mpc to 2.82 Mpc in the redshift range of ~0.03 - 0.95, of which 23 are hosted by quasars (giant radio quasars, GRQs). As part of the project SAGAN, we have created a database of all known GRGs, the GRG catalogue, from the literature (including our new sample); it includes 820 sources. For the first time, we present the multi-wavelength properties of the largest sample of GRGs. Our results establish that the distributions of the radio spectral index and the black hole mass of GRGs do not differ from the corresponding distributions of normal-sized radio galaxies (RGs). However, GRGs have a lower Eddington ratio (ER) than RGs. Using the mid-infrared data, we classified GRGs in terms of their accretion mode: either a high-power radiatively efficient high-excitation state, or a radiatively inefficient low-excitation state. We find that GRGs in high-excitation state statistically have larger sizes, stronger radio power, jet kinetic power, and higher ER than those in low-excitation state. Our analysis reveals a strong correlation between the ER and the scaled jet kinetic power, which suggests a disc-jet coupling. Our environmental study reveals that ~10% of all GRGs may reside at the centres of galaxy clusters, in a denser galactic environment, while the majority appears to reside in a sparse environment. We find that the probability of BCG as a GRG is quite low. We present new results for GRGs that range from black hole mass to large-scale environment properties. We discuss their formation and growth scenarios, highlighting the key physical factors that cause them to reach their gigantic size. Abridged., Comment: Accepted for publication in Astronomy & Astrophysics. 14 figures, 7 tables and 7 montages. Comments are welcome. "SAGAN Project website https://sites.google.com/site/anantasakyatta/sagan"

We present results of H I absorption experiment done using the Giant Metrewave Radio Telescope (GMRT) towards 27 low- and intermediate-luminosity ($P_{\rm 1.4 GHz}$ $\sim$10$^{23}$-10$^{26}$ W Hz$^{-1}$) radio active galactic nuclei (AGN), classified as either low excitation radio galaxies (LERGs) or high excitation radio galaxies (HERGs) and with WISE colour W2[4.6 $\mu$m]$-$W3[12 $\mu$m]$>$ 2. We report H I absorption detection towards seven radio AGNs, six of which are new. Combined with other sources from literature classified as LERGs or HERGs, we confirm our earlier result that compact radio AGNs with WISE colour W2$-$W3 $>$2 have higher detection rates compared to those with W2$-$W3 $<$2. We find that H I absorption detection rate is higher for HERGs (37.0$^{+15.8}_{-11.5}$ per cent) compared to LERGs (22.0$^{+3.9}_{-3.4}$ per cent), mainly due to a larger fraction of HERGs being gas and dust rich with a younger stellar population compared to LERGs. However, for similar compact radio structures and host galaxies with WISE colours W2$-$W3$>$2, we don't find any significant difference in detection rates of two types of AGNs implying detection of H I gas may not necessarily mean high excitation mode AGN. We further analysed the kinematics towards these sources. We find that while LERGs show a wide range in the shift of centroid velocities ($\sim$ $-$479 to $+$356 km s$^{-1}$) relative to the optical systemic velocity, most of the HERGs have centroid velocity shift less than 200 km s$^{-1}$, possibly due to differences in jet-interstellar medium interaction., Comment: 19 (16+3) pages, 9 figures, accepted for publication in MNRAS

Compact steep-spectrum (CSS) and peaked spectrum (PS) radio sources are compact, powerful radio sources. The multi-frequency observational properties and current theories are reviewed with emphasis on developments since the earlier review of O'Dea (1998). There are three main hypotheses for the nature of PS and CSS sources. (1) The PS sources might be very young radio galaxies which will evolve into CSS sources on their way to becoming large radio galaxies. (2) The PS and CSS sources might be compact because they are confined (and enhanced in radio power) by interaction with dense gas in their environments. (3) Alternately, the PS sources might be transient or intermittent sources. Each of these hypotheses may apply to individual objects. The relative number in each population will have significant implications for the radio galaxy paradigm. Proper motion studies over long time baselines have helped determine hotspot speeds for over three dozen sources and establish that these are young objects. Multifrequency polarization observations have demonstrated that many CSS/PS sources are embedded in a dense interstellar medium and vigorously interacting with it. The detection of emission line gas aligned with the radio source, and blue-shifted HI absorption and [OIII] emission lines indicates that AGN feedback is present in these objects -- possibly driven by the radio source. CSS/PS sources with evidence of episodic AGN over a large range of time-scales have been discussed. The review closes with a discussion of open questions and prospects for the future., Comment: 131 pages, 17 figures; accepted for publication in The Astronomy and Astrophysics Review

We present the first results of a project called SAGAN, which is dedicated solely to the studies of relatively rare megaparsec-scale radio galaxies in the Universe, called giant radio galaxies (GRGs). We have identified 162 new GRGs primarily from the NVSS with sizes ranging from ~0.71 Mpc to 2.82 Mpc in the redshift range of ~0.03 - 0.95, of which 23 are hosted by quasars (giant radio quasars, GRQs). As part of the project SAGAN, we have created a database of all known GRGs, the GRG catalogue, from the literature (including our new sample); it includes 820 sources. For the first time, we present the multi-wavelength properties of the largest sample of GRGs. Our results establish that the distributions of the radio spectral index and the black hole mass of GRGs do not differ from the corresponding distributions of normal-sized radio galaxies (RGs). However, GRGs have a lower Eddington ratio (ER) than RGs. Using the mid-infrared data, we classified GRGs in terms of their accretion mode: either a high-power radiatively efficient high-excitation state, or a radiatively inefficient low-excitation state. We find that GRGs in high-excitation state statistically have larger sizes, stronger radio power, jet kinetic power, and higher ER than those in low-excitation state. Our analysis reveals a strong correlation between the ER and the scaled jet kinetic power, which suggests a disc-jet coupling. Our environmental study reveals that ~10% of all GRGs may reside at the centres of galaxy clusters, in a denser galactic environment, while the majority appears to reside in a sparse environment. We find that the probability of BCG as a GRG is quite low. We present new results for GRGs that range from black hole mass to large-scale environment properties. We discuss their formation and growth scenarios, highlighting the key physical factors that cause them to reach their gigantic size. Abridged., Comment: Accepted for publication in Astronomy & Astrophysics. 14 figures, 7 tables and 7 montages. Comments are welcome. "SAGAN Project website https://sites.google.com/site/anantasakyatta/sagan"

We present results of H I absorption experiment done using the Giant Metrewave Radio Telescope (GMRT) towards 27 low- and intermediate-luminosity ($P_{\rm 1.4 GHz}$ $\sim$10$^{23}$-10$^{26}$ W Hz$^{-1}$) radio active galactic nuclei (AGN), classified as either low excitation radio galaxies (LERGs) or high excitation radio galaxies (HERGs) and with WISE colour W2[4.6 $\mu$m]$-$W3[12 $\mu$m]$>$ 2. We report H I absorption detection towards seven radio AGNs, six of which are new. Combined with other sources from literature classified as LERGs or HERGs, we confirm our earlier result that compact radio AGNs with WISE colour W2$-$W3 $>$2 have higher detection rates compared to those with W2$-$W3 $<$2. We find that H I absorption detection rate is higher for HERGs (37.0$^{+15.8}_{-11.5}$ per cent) compared to LERGs (22.0$^{+3.9}_{-3.4}$ per cent), mainly due to a larger fraction of HERGs being gas and dust rich with a younger stellar population compared to LERGs. However, for similar compact radio structures and host galaxies with WISE colours W2$-$W3$>$2, we don't find any significant difference in detection rates of two types of AGNs implying detection of H I gas may not necessarily mean high excitation mode AGN. We further analysed the kinematics towards these sources. We find that while LERGs show a wide range in the shift of centroid velocities ($\sim$ $-$479 to $+$356 km s$^{-1}$) relative to the optical systemic velocity, most of the HERGs have centroid velocity shift less than 200 km s$^{-1}$, possibly due to differences in jet-interstellar medium interaction., Comment: 19 (16+3) pages, 9 figures, accepted for publication in MNRAS

In order to understand the possible mechanisms of recurrent jet activity in radio galaxies and quasars, which are still unclear, we have identified such sources with a large range of linear sizes (220-917 kpc), and hence timescales of episodic activity. Here we present high-sensitivity 607-MHz Giant Metrewave Radio Telescope (GMRT) images of 21 possible double-double radio galaxies (DDRGs) identified from the FIRST survey to confirm their episodic nature. These GMRT observations show that none of the inner compact components suspected to be hotspots of the inner doubles are cores having a flat radio spectrum, confirming the episodic nature of these radio sources, We have identified a new DDRG with a candidate quasar, and have estimated the upper spectral age limits for eight sources which showed marginal evidence of steepening at higher frequencies. The estimated age limits (11-52 Myr) are smaller than those of the large-sized (similar to 1 Mpc) DDRGs., QC 20190802

The CHANG-ES galaxy sample consists of 35 nearby edge-on galaxies that have been observed using the VLA at 1.6 GHz and 6.0 GHz. Here we present the 3rd data release of our sample, namely the B-configuration 1.6 GHz sample. In addition, we make available the {\it band-to-band} spectral index maps between 1.6 GHz and 6.0 GHz, the latter taken in the matching resolution C-configuration. The images can be downloaded from https://www.queensu.ca/changes. These are our highest resolution images ($\approx$ 3 arcsec) and we examine the possible presence of low luminosity active galactic nuclei in the sample as well as some in-disk structure. New features can be seen in the spectral index maps that are masked in the total intensity emission, including hidden spiral arms in NGC~3448 and two previously unknown radio lobes on either side of the nucleus of NGC~3628. Our AGN detection rate, using only radio criteria, is 55\% which we take as a lower limit because some weaker embedded AGNs are likely present which could be revealed at higher resolution. Archival XMM-Newton data were used to search for further fingerprints of the AGNs in the studied sample. In galaxy disks, discrete regions of flat spectral index are seen, likely due to a thermal emission fraction that is higher than the global average., Comment: 36 pages, 7 figures plus a series of Panel images for Appendix B. Accepted to AJ, May 3, 2019 Version 2 changes the reference to previous observations of N4438 on p. 19

In order to understand the possible mechanisms of recurrent jet activity in radio galaxies and quasars, which are still unclear, we have identified such sources with a large range of linear sizes (220 $-$ 917 kpc), and hence time scales of episodic activity. Here we present high-sensitivity 607-MHz Giant Metrewave Radio Telescope (GMRT) images of 21 possible double-double radio galaxies (DDRGs) identified from the FIRST survey to confirm their episodic nature. These GMRT observations show that none of the inner compact components suspected to be hot-spots of the inner doubles are cores having a flat radio spectrum, confirming the episodic nature of these radio sources. We have indentified a new DDRG with a candidate quasar, and have estimated the upper spectral age limits for eight sources which showed marginal evidence of steepening at higher frequencies. The estimated age limits (11 $-$ 52 Myr) are smaller than those of the large-sized ($\sim$ 1 Mpc) DDRGs., Comment: Accepted for publication in MNRAS. 14 pages, 7 figures

The CHANG-ES galaxy sample consists of 35 nearby edge-on galaxies that have been observed using the VLA at 1.6 GHz and 6.0 GHz. Here we present the 3rd data release of our sample, namely the B-configuration 1.6 GHz sample. In addition, we make available the {\it band-to-band} spectral index maps between 1.6 GHz and 6.0 GHz, the latter taken in the matching resolution C-configuration. The images can be downloaded from https://www.queensu.ca/changes. These are our highest resolution images ($\approx$ 3 arcsec) and we examine the possible presence of low luminosity active galactic nuclei in the sample as well as some in-disk structure. New features can be seen in the spectral index maps that are masked in the total intensity emission, including hidden spiral arms in NGC~3448 and two previously unknown radio lobes on either side of the nucleus of NGC~3628. Our AGN detection rate, using only radio criteria, is 55\% which we take as a lower limit because some weaker embedded AGNs are likely present which could be revealed at higher resolution. Archival XMM-Newton data were used to search for further fingerprints of the AGNs in the studied sample. In galaxy disks, discrete regions of flat spectral index are seen, likely due to a thermal emission fraction that is higher than the global average., Comment: 36 pages, 7 figures plus a series of Panel images for Appendix B. Accepted to AJ, May 3, 2019 Version 2 changes the reference to previous observations of N4438 on p. 19

In order to understand the possible mechanisms of recurrent jet activity in radio galaxies and quasars, which are still unclear, we have identified such sources with a large range of linear sizes (220 $-$ 917 kpc), and hence time scales of episodic activity. Here we present high-sensitivity 607-MHz Giant Metrewave Radio Telescope (GMRT) images of 21 possible double-double radio galaxies (DDRGs) identified from the FIRST survey to confirm their episodic nature. These GMRT observations show that none of the inner compact components suspected to be hot-spots of the inner doubles are cores having a flat radio spectrum, confirming the episodic nature of these radio sources. We have indentified a new DDRG with a candidate quasar, and have estimated the upper spectral age limits for eight sources which showed marginal evidence of steepening at higher frequencies. The estimated age limits (11 $-$ 52 Myr) are smaller than those of the large-sized ($\sim$ 1 Mpc) DDRGs., Comment: Accepted for publication in MNRAS. 14 pages, 7 figures

We present a catalogue of 349 giant radio sources (GRSs including both galaxies and quasars). The database contains all giants known to date from the literature. These GRSs cover the redshift range of 0.016$<$z$<$3.22 and include radio sources of projected linear sizes larger than 0.7~Mpc which extend up to 4.7~Mpc. We provide the principal parameters (i.e. exact position of the host in the sky, redshift, angular and projected linear size, red optical magnitude, radio morphology type, total radio flux density and luminosity) for all the sources as well as characteristics of the sample. Based on the distribution of GRSs in the sky we identify regions where there is a paucity of giants, so that future surveys for this type of objects could concentrate primarily in these fields. From the analysis presented here, we estimate a lower limit for the expected number of GRSs as about 2000, for the resolution and sensitivity limits of FIRST, NRAO VLA Sky Survey and Sloan Digital Sky Survey surveys. Compared with earlier compilations, there is a significant increase in the number of large giants with sizes $>$ 2 Mpc as well as those at high redshifts with z$>$1. We discuss aspects of their evolution and suggest that these are consistent with evolutionary models., Comment: 20 pages, 7 figures, 1 table. Accepted to publish in ApJS

We present the first data release of high-resolution ($\leq0.2$ arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (LINER and Seyfert) and quiescent (HII galaxies and Absorption line galaxies, ALG), which are reclassified based upon revised emission-line diagrams. We detect radio emission $\gtrsim$ 0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for HII galaxies and 5/14 for ALGs) with radio sizes typically of $\lesssim$100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 10$^{32}$ to 10$^{40}$ erg s$^{-1}$: LINERs and HII galaxies show the highest and the lowest radio powers respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to $\sim$10$^{7}$ M$_{\odot}$, but a break emerges at lower masses. Using [O III] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted HII galaxies follow an optical fundamental plane of BH activity, suggesting a common disc-jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; HII galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties., Comment: accepted for publication on MNRAS (45 pages, 10 figures with reduced image quality)

We detect 5 galaxies in the CHANG-ES (Continuum Halos in Nearby Galaxies -- an EVLA Survey) sample that show circular polarization (CP) at L-band in our high resolution data sets. Two of the galaxies (NGC~4388 and NGC~4845) show strong Stokes $V/I\,\equiv\,m_C\,\sim\,2$\%, two (NGC~660 and NGC~3628) have values of $m_C\sim \,0.3$\%, and NGC~3079 is a marginal detection at $m_C\sim \,0.2$\%. The two strongest $m_C$ galaxies also have the most luminous X-ray cores and the strongest internal absorption in X-rays. We have expanded on our previous Faraday conversion interpretation and analysis and provide analytical expressions for the expected $V$ signal for a general case in which the cosmic ray electron energy spectral index can take on any value. We provide examples as to how such expressions could be used to estimate magnetic field strengths and the lower energy cutoff for CR electrons. Four out of our detections are {\it resolved}, showing unique structures, including a {\it jet} in NGC~4388 and a CP `conversion disk' in NGC~4845. The conversion disk is inclined to the galactic disk but is perpendicular to a possible outflow direction. Such CP structures have never before been seen in any galaxy to our knowledge. None of the galaxy cores show linear polarization at L-band. Thus CP may provide a unique probe of physical conditions deep into radio AGNs., Comment: 30 pages, 4 figures, accepted to MNRAS

We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H ii galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams. We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for H ii galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 1032 to 1040 erg s−1: LINERs and H ii galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ∼107 M⊙, but a break emerges at lower masses. Using [O iii] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted H ii galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc–jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; H ii galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H ii galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams. We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for H ii galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 1032 to 1040 erg s−1: LINERs and H ii galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ∼107 M⊙, but a break emerges at lower masses. Using [O iii] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted H ii galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc–jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; H ii galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H ii galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams. We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for H ii galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 1032 to 1040 erg s−1: LINERs and H ii galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ∼107 M⊙, but a break emerges at lower masses. Using [O iii] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted H ii galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc–jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; H ii galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H ii galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams. We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for H ii galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 1032 to 1040 erg s−1: LINERs and H ii galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ∼107 M⊙, but a break emerges at lower masses. Using [O iii] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted H ii galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc–jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; H ii galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

We present a catalogue of 349 giant radio sources (GRSs including both galaxies and quasars). The database contains all giants known to date from the literature. These GRSs cover the redshift range of 0.016$<$z$<$3.22 and include radio sources of projected linear sizes larger than 0.7~Mpc which extend up to 4.7~Mpc. We provide the principal parameters (i.e. exact position of the host in the sky, redshift, angular and projected linear size, red optical magnitude, radio morphology type, total radio flux density and luminosity) for all the sources as well as characteristics of the sample. Based on the distribution of GRSs in the sky we identify regions where there is a paucity of giants, so that future surveys for this type of objects could concentrate primarily in these fields. From the analysis presented here, we estimate a lower limit for the expected number of GRSs as about 2000, for the resolution and sensitivity limits of FIRST, NRAO VLA Sky Survey and Sloan Digital Sky Survey surveys. Compared with earlier compilations, there is a significant increase in the number of large giants with sizes $>$ 2 Mpc as well as those at high redshifts with z$>$1. We discuss aspects of their evolution and suggest that these are consistent with evolutionary models., Comment: 20 pages, 7 figures, 1 table. Accepted to publish in ApJS

We detect 5 galaxies in the CHANG-ES (Continuum Halos in Nearby Galaxies -- an EVLA Survey) sample that show circular polarization (CP) at L-band in our high resolution data sets. Two of the galaxies (NGC~4388 and NGC~4845) show strong Stokes $V/I\,\equiv\,m_C\,\sim\,2$\%, two (NGC~660 and NGC~3628) have values of $m_C\sim \,0.3$\%, and NGC~3079 is a marginal detection at $m_C\sim \,0.2$\%. The two strongest $m_C$ galaxies also have the most luminous X-ray cores and the strongest internal absorption in X-rays. We have expanded on our previous Faraday conversion interpretation and analysis and provide analytical expressions for the expected $V$ signal for a general case in which the cosmic ray electron energy spectral index can take on any value. We provide examples as to how such expressions could be used to estimate magnetic field strengths and the lower energy cutoff for CR electrons. Four out of our detections are {\it resolved}, showing unique structures, including a {\it jet} in NGC~4388 and a CP `conversion disk' in NGC~4845. The conversion disk is inclined to the galactic disk but is perpendicular to a possible outflow direction. Such CP structures have never before been seen in any galaxy to our knowledge. None of the galaxy cores show linear polarization at L-band. Thus CP may provide a unique probe of physical conditions deep into radio AGNs., Comment: 30 pages, 4 figures, accepted to MNRAS

We present the first data release of high-resolution ($\leq0.2$ arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (LINER and Seyfert) and quiescent (HII galaxies and Absorption line galaxies, ALG), which are reclassified based upon revised emission-line diagrams. We detect radio emission $\gtrsim$ 0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for HII galaxies and 5/14 for ALGs) with radio sizes typically of $\lesssim$100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 10$^{32}$ to 10$^{40}$ erg s$^{-1}$: LINERs and HII galaxies show the highest and the lowest radio powers respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to $\sim$10$^{7}$ M$_{\odot}$, but a break emerges at lower masses. Using [O III] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted HII galaxies follow an optical fundamental plane of BH activity, suggesting a common disc-jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; HII galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties., Comment: accepted for publication on MNRAS (45 pages, 10 figures with reduced image quality)

We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H ii galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams. We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for H ii galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 1032 to 1040 erg s−1: LINERs and H ii galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ∼107 M⊙, but a break emerges at lower masses. Using [O iii] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted H ii galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc–jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; H ii galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H II galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams.We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for HII galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 10 to 10 erg s: LINERs and HII galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ~10 M, but a break emerges at lower masses. Using [OIII] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted HII galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc-jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; HII galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.© 2018 The Author(s).

We present a radio and optical study of the double-double radio galaxy J1328+2752 based on new low-frequency Giant Metrewave Radio Telescope observations and Sloan Digital Sky Survey (SDSS) data. The radio data were used to investigate the morphology and to perform a spectral index analysis. In this source, we find that the inner double is misaligned by similar to 30 degrees from the axis of the outer diffuse structure. The SDSS spectrum shows that the central component has double-peaked line profiles with different emission strengths. The average velocity offset of the two components is 235 +/- 10.5 kms(-1). The misaligned radio morphology along with the double-peaked emission lines indicate that this source is a potential candidate binary supermassive black hole. This study further supports mergers as a possible explanation for repeated jet activity in radio sources., QC 20171013

We present a radio and optical study of the double-double radio galaxy J1328+2752 based on new low-frequency Giant Metrewave Radio Telescope observations and Sloan Digital Sky Survey (SDSS) data. The radio data were used to investigate the morphology and to perform a spectral index analysis. In this source, we find that the inner double is misaligned by similar to 30 degrees from the axis of the outer diffuse structure. The SDSS spectrum shows that the central component has double-peaked line profiles with different emission strengths. The average velocity offset of the two components is 235 +/- 10.5 kms(-1). The misaligned radio morphology along with the double-peaked emission lines indicate that this source is a potential candidate binary supermassive black hole. This study further supports mergers as a possible explanation for repeated jet activity in radio sources.

We present results from our Giant Metrewave Radio Telescope (GMRT) HI observations of the Arp 305 system. The system consists of two interacting spiral galaxies NGC 4016 and NGC 4017, a large amount of resultant tidal debris and a prominent tidal dwarf galaxy (TDG) candidate projected within the tidal bridge between the two principal galaxies. Our higher resolution GMRT HI mapping, compared to previous observations, allowed detailed study of smaller scale features. Our HI analysis supports the conclusion in Hancock et al. (2009) that the most recent encounter between the pair occurred $\sim$ 4 $\times$ 10$^8$ yrs ago. The GMRT observations also show HI features near NGC 4017 which may be remnants of an earlier encounter between the two galaxies. The HI properties of the Bridge TDG candidate include: M(HI) $\sim$ 6.6 $\times$ 10$^8$ msolar and V(HI) = 3500$\pm$ 7 km/s, which is in good agreement with the velocities of the parent galaxies. Additionally the TDG's HI linewidth of 30 km/s and a modest velocity gradient together with its SFR of 0.2 msolar/yr add to the evidence favouring the bridge candidate being a genuine TDG. The Bridge TDG's \textit{Spitzer} 3.6 $\mu$m and 4.5 $\mu$m counterparts with a [3.6]--[4.5] colour $\sim$ -0.2 mag suggests stellar debris may have seeded its formation. Future spectroscopic observations could confirm this formation scenario and provide the metallicity which is a key criteria for the validation for TDG candidates., Comment: 14 pages, 9 figures, Accepted in MNRAS

We present results from our Giant Metrewave Radio Telescope (GMRT) HI observations of the Arp 305 system. The system consists of two interacting spiral galaxies NGC 4016 and NGC 4017, a large amount of resultant tidal debris and a prominent tidal dwarf galaxy (TDG) candidate projected within the tidal bridge between the two principal galaxies. Our higher resolution GMRT HI mapping, compared to previous observations, allowed detailed study of smaller scale features. Our HI analysis supports the conclusion in Hancock et al. (2009) that the most recent encounter between the pair occurred $\sim$ 4 $\times$ 10$^8$ yrs ago. The GMRT observations also show HI features near NGC 4017 which may be remnants of an earlier encounter between the two galaxies. The HI properties of the Bridge TDG candidate include: M(HI) $\sim$ 6.6 $\times$ 10$^8$ msolar and V(HI) = 3500$\pm$ 7 km/s, which is in good agreement with the velocities of the parent galaxies. Additionally the TDG's HI linewidth of 30 km/s and a modest velocity gradient together with its SFR of 0.2 msolar/yr add to the evidence favouring the bridge candidate being a genuine TDG. The Bridge TDG's \textit{Spitzer} 3.6 $\mu$m and 4.5 $\mu$m counterparts with a [3.6]--[4.5] colour $\sim$ -0.2 mag suggests stellar debris may have seeded its formation. Future spectroscopic observations could confirm this formation scenario and provide the metallicity which is a key criteria for the validation for TDG candidates., Comment: 14 pages, 9 figures, Accepted in MNRAS

We present an overview of the Space Telescope A901/2 Galaxy Evolution Survey (STAGES). STAGES is a multiwavelength project designed to probe physical drivers of galaxy evolution across a wide range of environments and luminosity. A complex multicluster system at z∼ 0.165 has been the subject of an 80-orbit F606W Hubble Space Telescope (HST)/Advanced Camera for Surveys (ACS) mosaic covering the full span of the supercluster. Extensive multiwavelength observations with XMM-Newton, GALEX, Spitzer, 2dF, Giant Metrewave Radio Telescope and the 17-band COMBO-17 photometric redshift survey complement the HST imaging. Our survey goals include simultaneously linking galaxy morphology with other observables such as age, star formation rate, nuclear activity and stellar mass. In addition, with the multiwavelength data set and new high-resolution mass maps from gravitational lensing, we are able to disentangle the large-scale structure of the system. By examining all aspects of an environment we will be able to evaluate the relative importance of the dark matter haloes, the local galaxy density and the hot X-ray gas in driving galaxy transformation. This paper describes the HST imaging, data reduction and creation of a master catalogue. We perform the Sérsic fitting on the HST images and conduct associated simulations to quantify completeness. In addition, we present the COMBO-17 photometric redshift catalogue and estimates of stellar masses and star formation rates for this field. We define galaxy and cluster sample selection criteria, which will be the basis for forthcoming science analyses, and present a compilation of notable objects in the field. Finally, we describe the further multiwavelength observations and announce public access to the data and catalogues