e-MERLIN detects the anticipated radio-optical offsets in high redshift candidates of sub-kpc dual SMBHs

November 2023

Gaia astrometric jitter was used to select dual SMBH candidates and the method shows promise with e-MERLIN follow up observations

Dual super massive black holes (SMBH) may appear in the post-merger stage of galaxies, which could play a key role in galaxy formation and evolution. As time goes by, dual SMBHs would get closer to each other due to dynamical friction, form binary SMBHs with a compact orbit and finally coalesce. Searching for close (∼kpc or sub-kpc) dual SMBHs, the progenitors of coalescing SMBHs, thus are essential to probe their dynamical evolution as well as the process of galaxy merging, especially at high redshifts when galaxy mergers occur much more frequently. Such dual SMBHs may appear as a dual AGN (active galactic nuclei) if both SMBHs are accreting, or an off-nucleus AGN, if only one SMBH is active. However dual and off-nucleus AGN were previously found mostly at low redshifts or large separations (> 10 kpc).

In a recent work, Haochen Wang and his team obtained high resolution e-MERLIN images of 5 candidates of high redshift dual SMBHs. These candidate quasars (luminous AGN) were pre-selected with clear astrometric jitters in Gaia EDR3, as the stochastic flux variabilities of the dual or off-nucleus quasar could yield astrometric variation of the photocenter of the dual-SMBH system. e-MERLIN observations revealed a single compact radio source for each candidate. Remarkably, four of them exhibit significant radio-optical offsets, which represent for the anticipated separations between one radio loud nucleus and the optical photocenter of a dual-SMBH system. Such radio-optical offsets are hardly seen in normal quasars, thus strongly favor the scenario of dual or off-nucleus quasars. The team confirms the projected separations of the candidate dual SMBHs could be as small as sub-kpc, and highlights the unique capability of high-resolution radio images to investigate close dual SMBHs.

Read the full article here (Wang et al. 2023).

VLBI Observations of a sample of Palomar-Green quasars

October 2023

Combining e-MERLIN with other VLBI arrays provides insight into radio-quiet quasars radio emission mechanisms

Very long baseline interferometry can be a powerful tool for providing insights into the origins of the nuclear radio emission in quasars. In radio-quiet quasars (RQQs), it is especially important as the radio emission can be due to the presence of a radio jets from an accreting AGN, winds, star formation, coronae, or a combination of the above. In lower-resolution studies, it is hard to disentangle these processes, but at sub-arcsecond resolution, a high-brightness temperature core can be attributed to the presence of jets or coronae from an accreting AGN, rather than star formation or winds. The spectral index, morphology and flux densities of the source also give clues to the source of the emission too. By combining the information from multiple arrays, it is possible to get a statistical understanding of the contribution of these different processes to the observed radio emission.

In these works, published by Monthly Notices of the Royal Astronomical Society, Ailing Wang and her team observed 20 quasars, comprising 4 radio loud (RLQs) and 16 RQQs, from the Palomar Green sample, using the VLA, VLBA, and EVN+e-MERLIN measurements at different resolution scales. In 10/16 RQQ cases, radio emission was unequivocally detected in the VLBA data, with 8 of those exhibiting a compact core. They noticed a division in the RLQs and the RQQs at ~30mJy, with RQQs likely due a combination of star formation and AGN activity. Moreover, the RQQs in their study proved to be highly resolved, due to extended jets or relic emission. One source, PG 0050+124, which was observed with EVN+e-MERLIN demonstrates this well. The combination of longer exposure time, and use of intermediate and long baselines from the e-MERLIN/EVN antennas enabled a noise level of 9µJy/beam, about 2.5 times lower than the noise in the VLBA image at a comparable frequency. Thanks to its impressive sensitivity, the EVN+eMERLIN image of PG 0050+124 unveils a more intricate jet structure.

Read the first article here (Wang et al. 2023a).

Read the second article here (Wang et al. 2023b).

LeMMINGs VI: Investigating the influence of the bulge on AGN activity and host galaxy evolution with Hubble and e-MERLIN

September 2023

Hubble and e-MERLIN observations link AGN and bulge properties in the LeMMINGs survey

The active galactic nucleus (AGN) at the galaxy centre and star formation in the bulge play a crucial role in moderating the growth and evolution of galaxies. The relationship between the mass of the bulge and the mass of the central accreting supermassive black hole powering the AGN is firmly established, with the two growing together. For nearby galaxies, distinguishing between the AGN and the bulge is possible due to the AGN's much higher central surface brightness in the optical, but this is not true for low-luminosity AGN. Furthermore, other nuclear features, e.g., rings and bars can complicate matters, but using high resolution e-MERLIN radio data and Hubble optical data, it is possible to discriminate the AGN from other sources of emission. The resolution of Hubble is comparable to that of e-MERLIN at 1.5 GHz, making the two a perfect synergetic pair for exploring the effect that bulge properties have on AGN, which is one of the goals of the LeMMINGs survey.

The e-MERLIN legacy project (LeMMINGs) provides high sensitivity radio observations of 280 nearby galaxies at 1.5 and 5 GHz, with a milli-arcsecond resolution to detect nuclear radio emission, identifying low-luminosity AGN and supernova remnant shells which can trace star formation. As part of this project, the LeMMINGs team has recently published 1.5 GHz e-MERLIN radio data for the full sample of 280 nearby galaxies. In a subsequent study, the team used data from the Hubble Science Archive and performed multi-component decompositions of optical images for 173 out of 280 galaxies and quantify the impact of various galaxy components (bulge, disc, AGN, bar, ring, spiral arms, and star clusters) on the optical galaxy profile. This allowed them to accurately measure optical bulge properties. In this work, Bil Dullo and the LeMMINGs team investigated the link between the radio core luminosity and the properties of the host bulge as well as its surrounding environment. When compared to the radio data, bulge dominance is linked to brighter radio core luminosities, with the both AGN and radio detection fractions increasing with the bulge mass. Furthermore, the analysis reveals a transition from AGN-dominated radio emission in massive bulges to stellar-driven processes in low-mass bulges. Radio-loud hosts preferred early-type morphology, but no obvious dependence on environment was found for radio loudness, nuclear radio activity, and the AGN fraction at a fixed bulge mass. Radio-loud and radio-quiet hosts are indistinguishable in terms of the Sersic index and ellipticity of the bulge.

Read the full article here.

Read more LeMMINGs articles here.

e-MERLIN Data School announcement

September 2023

The 1st e-MERLIN data school has been announced, taking place in Manchester from 23-25 October 2023

e-MERLIN support staff, with funding support from the Opticon RadioNet Pilot, will be running a data school at the University of Manchester from 23-25 October 2023. The purpose of this school is to show participants how to reduce e-MERLIN data using the e-MERLIN CASA Pipeline. The school is designed for those with some radio astronomy knowledge. Priority will be given to PhD students and early career researchers. The three-day school will include calibration, imaging and self-calibration tutorials, with an opportunity to bring your own data (BYOD) to get expert help with your own e-MERLIN projects. We expect to be able to have space for up to 10 participants.

Find out more about the 1st e-MERLIN data school here.

e-MERLIN Cycle 16 results announcement

July 2023

The e-MERLIN Time Allocation Group met on 13th July 2023 to consider proposals for Cycle-16. Proposals were received for L-Band (1.3-1.7 GHz), C-Band (4.5-7.5GHz), and K-Band (19-25 GHz). The amount of time approved is set by existing Legacy programme observation requirements, scheduling and engineering constraints, and by EVN commitments within the Cycle-16 period.

The e-MERLIN Cycle 16 call for proposals list of accepted proposals is below (in no particular order). The next call for proposals is anticipated in Autumn 2023.

  • Precise calorimetry of large-scale jets from black hole X-ray binaries
  • The origin of the compact 50 mas emission in Radio Quiet Quasars
  • High fidelity mapping of the OH maser shell of OH55.0+0.7
  • The e-MERLIN view of the radio counterpart of GW events during O4
  • Cosmic telescopes: peering through dark matter to understand RQQ radio emission
  • Cosmic telescopes: witnessing the emission mechanism of radio quiet quasars
  • Using variability to deconstruct accretion in jet systems around forming massive stars
  • Spectral structure of the radio galaxy 3C 123
  • Tracing the Radio/X-ray Connection in the Enigmatic Changing-look AGN 1ES 1927+654
  • Does M82 Remnant 41.95+57.5 Harbour a Central Late-stage GRB Nebula?
  • NGC 4438: Unveiling the connection between the radio shell-like structure and the ionised outflow
  • A new window on radio AGN with e-MERLIN, EVN and LOFAR
  • High-resolution observations of short GRBs beyond the LIGO horizon
  • Continued eMERLIN monitoring of ZTF22aaajecp/AT2022cmc: the first jetted tidal disruption event in a decade
  • ToO observations of the nearest recurrent nova, T Corona Borealis, during its imminent outburst

Setting up for SETI with e-MERLIN

June 2023

Searching for SETI calibrator sources resulted in a neutral hydrogen detection but no technosignatures.

Over the course of the last decade, the Breakthrough Listen project has reinvigorated the search for extraterrestrial intelligence (SETI) to buy telescope time and develop new tools and techniques. Until recently, large single dishes have been used e.g. the Robert C. Byrd Green Bank Telescope (GBT) as well as beam-forming arrays e.g. the MeerKAT that forms pencil-shaped beams for targeted searches over a small area of the sky. The use of arrays with long baselines like the European VLBI Network (EVN) has not been fully explored despite the advantages such arrays offer over the other instruments. VLBI arrays are more robust to radio frequency interference since RFI must be present in a baseline to correlate. The increased sensitivity increases the robustness of the detection and VLBI has a high astrometric accuracy which could aid in the localisation of technosignatures in the solar system.

University of Manchester Phd student Kelvin Wandia and collaborators set up a VLBI experiment to search for secondary calibrator sources for future SETI surveys in the Kepler fields, which include Kepler-111b, an exoplanet orbiting a G-type star. While no secondary calibrators were found, a nearby primary calibrator, J1926+4441 was correlated at high temporal and spectral resolution in order to search for SETI-like signals. During the data analysis, a feature at 1420.4 MHz was found, though further follow-up observations with the EVN and e-MERLIN revealed that the feature was due to the rise in the system temperatures due to galactic hydrogen filling the beams of the antennas. However, this still demonstrated a new data analysis/interpretation scheme for SETI using VLBI. After flagging this feature from the data, it was possible to search for technosignatures from Kepler-111b, though no transmitters were detected.

Read the full article here.

YERAC's coming to Manchester

June 2023

The University of Manchester and e-MERLIN will host the 52nd Young European Radio Astronomers Conference from 12 - 15 September 2023.

The Young European Radio Astronomers Conference (YERAC) has been running since 1968, giving early career researchers from across Europe an opportunity to meet and present their research to their peers. The relaxed atmosphere provides a welcoming introduction to conferences. This will be the sixth time that the University of Manchester/Jodrell Bank has hosted YERAC. Up to 40 participants will be joining us from 12-15 September 2023.

Find out more about YERAC 2023 session here.

The first radio detection of a Type 1a supernova, thanks to e-MERLIN

May 2023

SN2020eyj was detected in the radio using e-MERLIN, over 500 days after the initial optical discovery

Supernovae are the result of the deaths of stars - a large explosion rips the star apart. They are responsible for some of the heavier elements we find in the Universe. One of the best studied types of supernova are the Type 1a, which is caused by a white dwarf accreting too much mass and exploding. Because Type 1a supernovae reach the same critical mass before exploding, they have been used for years as standardisable candles in cosmology. However, two competing mechanisms have been argued to be the progenitor systems of Type 1as, either the merger of two white dwarfs, or, one white dwarf accretes mass from a companion normal star. Detecting radio emission from a Type 1a supernova has long been sought after, as it is expected in the case of accretion from a companion star, but not if two white dwarfs merge.

The Type 1a supernova SN 2020eyj exploded in March 2020 and was followed by the optical community. It was realised from late-time optical spectra that SN 2020eyj was a sub-type of Type 1a supernova which showed signs of circumstellar medium interaction and was re-classified as a Type 1a-CSM supernova. Following this discovery, requests were made to e-MERLIN to observe this potentially interesting source, over 500 days from its initial discovery.

e-MERLIN's unique combination of sub-arcsecond resolution and micro Jansky sensitivity enabled the detection of SN 2020eyj, the first ever for any Type 1a supernova. The detection of the radio emission in this source effectively rules out the white dwarf merger scenario for SN 2020eyj. This discovery of late-time radio emission from a Type 1a supernova will guide and shape future studies with the next generation of instruments like the Square Kilometre Array.

Read the Manchester press release here.

Read the full article here.

LeMMINGs V: linking Hubble with e-MERLIN to explore AGN and galaxy evolution

April 2023

Hubble and e-MERLIN prove a matching synergistic pair linking AGN and galaxy evolution in the LeMMINGs survey

The growth and evolution of galaxies is moderated and shaped by the active galactic nucleus (AGN) in the center and star formation in the bulge. The relationship between the mass of the bulge and the central accreting super-massive black hole powering the AGN is well established, with the two growing together. In nearby galaxies it is possible to distinguish the AGN from the bulge as it is usually much brighter in the optical, but this isn't the case for the lowest-luminosity AGN. In addition, other nuclear features like rings and bars can complicate matters, but using high resolution e-MERLIN radio data and Hubble optical data, it is possible to discriminate the AGN from other sources of emission. The resolution of Hubble is comparable to that of e-MERLIN at 1.5 GHz, making the two a perfect match for exploring the effect the AGN has on the bulge and galaxy as a whole, which is one of the goals of the LeMMINGs survey.

The LeMMINGs is an e-MERLIN legacy project to survey 280 nearby galaxies at 1.5 and 5 GHz at milli-arcsecond resolution to isolate the nuclear emission to find low-luminosity AGN and detect supernova remnant shells which can trace star formation. The 1.5 GHz radio survey of the nuclear regions has already been published. In this work, Bil Dullo and the LeMMINGs team analysed data from the Hubble science archive finding data for 173/280 LeMMINGs galaxies. They performed multi-component decompositions of the optical images to measure the influence of the galaxy bulge, disc, AGN, bar, ring, spiral arms, and nuclear star clusters on the overall galaxy profile. This allowed them to accurately understand the contribution from the bulge to the optical galaxy profile, showing that the bulge becomes rounder, more prominent and larger the further along the Hubble sequence from irregulars to elliptical galaxies. When comparing to the radio information, bulge dominance is also linked to brighter radio core luminosities, with the detection fraction of the radio core increasing with the bulge mass too. A follow up work will look more closely at the radio core luminosity and host bulge properties.

Read the full article here.

Read more LeMMINGs articles here.

e-MERLIN goes to NAM 2023

April 2023

Join us in Cardiff for the National Astronomical Meeting 2023.

The e-MERLIN operations team will be going to Cardiff from 3-7 July 2023 for the National Astronomical Meeting. We have an accepted session entitled "e-MERLIN and SKA pathfinders: preparing UK early-career researchers for science with the SKA". Please submit an abstract before the deadline on the 24th April 2023 to be considered for a talk or poster for this session. We will also have a stand for you to meet the team alongside UK ALMA ARC node and UK SKA SRC members. We look forward to seeing you there!

Find out more about NAM 2023 session here.

Finding mini jets in the mini-halo of RXJ1720.1+2638

March 2023

The discovery of sub-kpc-scale jets in RXJ1720.1+2638 complicates the picture of how the diffuse radio emission is produced in this galaxy cluster.

Radio mini-halos are diffuse synchrotron emission found in the centres of some galaxy clusters. They are thought to arise from either aged relativistic electrons being re-accelerated to energies high enough to cause the synchrotron emission, or by relativistic protons interacting with thermal intra-cluster-medium electrons, producing relativistic electrons as part of a decay chain. In the case of RXJ1720.1+2638, there is competing evidence as to which one dominates. Complicating matters is the presence of an active central nucleus which can also cause energy injection into the system.

Using e-MERLIN Yvette Perrott and her team were able to show unequivocally that RXJ1720.1+2638 has sub-kpc-scale radio jets. The e-MERLIN data recover ~60% of the total flux of the central core when compared to lower resolution studies, indicating that the jet may extend out further. These data have further implications for correlations of the mini-halo luminosity and the brightest central galaxy luminosity.

Read the full article here.

Resolving the extra-galactic population of AGN from star formation with e-MERLIN and EVN

March 2023

Studies of the Northern SPARCS field at milli-arcsecond resolution have isolated compact AGN emission from star formation for the first time.

The SKA PAthfinder Radio Continuum Surveys (SPARCS) are a set of astronomical fields that SKA pathfinder telescopes are observing to make sensitive large-area reference surveys in order to decouple star formation (SF) from active galactic nuclei (AGN) in distant galaxies. Such large and deep surveys will enable the study of galaxy evolution and cosmology and will also determine the key science questions that the SKA will answer.

By using e-MERLIN and the EVN together as one instrument, Ann Njeri and her team observed the Northern SPARCS field with a multi-resolution (10-100 milliarcseconds) programme to resolve the compact emission of AGN from the diffuse star formation emission. The combined use of e-MERLIN with the EVN provides the sensitivity to detect the faintest emission, while the resolution detects compact high brightness temperature emission. Using these high spatial resolution (9 pc – 0.3 kpc at 𝑧 ∼ 1.25) data, 11 sources were detected from a targeted sample of 52 known radio sources from previous observations with the eMERLIN, giving a VLBI detection fraction of ∼ 21%. Isolating these high brightness temperature and compact sources improves the ability to isolate the AGN emission from star formation and hence reduce the uncertainties in star formation estimates using the radio band alone.

This SKA-2 like study is the first of its kind for any of the SPARCS reference fields, providing a high spatial dynamic range view (10–100mas) of the high redshift radio source population. These results will inform future SKA observations, in relation to survey/instrument biases, de-coupling AGN and star-formation and addressing key technical verification challenges for SKA pathfinders (and VLBI) such as data processing and source flux density scaling.

Read the full article here.

e-MERLIN witnesses power of SMBHs during rare tidal disruption event

February 2023

e-MERLIN has been involved in a multi-facility campaign to study the jet launched by a supermassive black hole after a wandering star passed too close and was ripped apart.

These events are known as jetted tidal disruption events (TDEs) and are rather rare: this is the fourth jetted TDE found to date. Since February 2022, observations have been made of the TDE AT2022cmc to understand the long term behaviour of this rare event. The e-MERLIN and multi-facility campaign is designed to understand both the jet and its surrounding environment as it propagates out through the host galaxy.

In a paper published in Monthly Notices of the Royal Astronomical Society, Lauren Rhodes (Oxford) and her team demonstrate the importance of high cadence monitoring for studying the evolving radio counterpart. In AT2022cmc, they find evidence of Doppler boosting, where the observed radiation is boosted as a result of the material moving at relativistic velocities. The observations show that the jet is pointed directly at Earth. The highly relativistic velocities of jets such as that associated with AT2022cmc, means that observers are only able to see those pointed at Earth, and therefore are rarely given such a perfect opportunity to study the jet over the coming years as it decelerates and interacts with the environment of their host galaxy.

Read the full article here.

e-MERLIN Cycle 15 results announcement

January 2023

The e-MERLIN Cycle 15 call for proposals list of accepted proposals is below. The next call for proposals is anticipated in Spring 2023.

PI Title
Engels High fidelity mapping of the OH maser shell of OH39.7+1.5
Giroletti The e-MERLIN view of the radio counterpart of GW events during O4
Johnston Using variability to deconstruct accretion in jet systems around forming massive stars
Kirsten Localising repeating FRBs with EVN-light -- including eMERLIN
Moldon Characterizing the physical properties of the first SN Ia CSM radio detection
Muxlow Does M82 Remnant 41.95+57.5 Harbour an Emerging Pulsar Wind Nebula?
Perez-Torres e-MERLIN radio follow-up of Tidal Disruption Events
Radcliffe A new window on radio AGN with e-MERLIN, EVN and LOFAR
Rhodes Late time observations of GRB 221009A: the brightest radio afterglow to date
Richards Investigating the fine details of dust-forming outflows from evolved stars with water masers
Sarbadhicary e-MERLIN observations of the first JWST-detected supernova remnants in M33
Shu Witnessing the fast jet ejections towards the end of an AGN state transition
Walker Honing in on the homes of repeating FRBs
Yang Detecting an early hint for neutron-star merger jets


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