LIST OF PARTICIPANTS
Participants
The provisional list of the participants on YERAC 2024 can be found here.
| Participant | Institution | Country |
|---|---|---|
| Aleksandra Krauze | Nicolaus Copernicus University in Toruń | Poland |
| Andrés Megías Toledano | Centro de Astrobiología (CSIC-INTA) | Spain |
| Ann Njeri | Newcastle University | United Kingdom |
| Antonio Martínez-Henares | Centro de Astrobiología (CAB), CSIC-INTA | Spain |
| Candela Chico Herrera | Universidad Complutense de Madrid | Spain |
| Cosima Eibensteine | NRAO Charlottesville | United States |
| David Alonso López | Universidad Complutense de Madrid | Spain |
| David Fernández Gil | CEFCA | Spain |
| David Haasler García | Centro de Astrobiología (CAB, INTA-CSIC) | Spain |
| David San Andrés de Pedro | Centro de Astrobiología (CAB), CSIC-INTA | Spain |
| Davide Belfiori | University of Bologna (INAF - IRA) | Italy |
| Denisha Shanice Pillay | Max Planck Institute for Radio Astronomy | Germany |
| Elisa Masa Andrés | Observatorio Astronómico Nacional (OAN-IGN) | Spain |
| Emanuele De Rubeis | Istituto di Radioastronomia (INAF-IRA) | Italy |
| Erwan Rouillé | LESIA, Paris Observatory | France |
| Fengwei Xu | I. Physikalisches Institut, Universität zu Köln | Germany |
| Hannah Walker | University of Leeds | United Kingdom |
| Jaime Alonso Hernández | Centro de Astrobiología (CSIC-INTA) | Spain |
| Jort Boxelaar | INAF - IRA, Bologna | Italy |
| Juliette Robuschi | Institut de Planétologie et d'Astrophysique de Grenoble | France |
| Léontine Ségal | Institut de RadioAstronomie Millimétrique (IRAM) | France |
| Lucy Clews | The Open University | United Kingdom |
| Luis Peña-Moñino | IAA-CSIC | Spain |
| Marina Ruiz García | Observatorio Astronómico Nacional (OAN-IGN) | Spain |
| Miguel Montero Vega | Universidad Complutense de Madrid | Spain |
| Miren Muñoz Echeverría | Institut de Recherche en Astrophysique et Planétologie (Toulouse) | France |
| Mousumi Mahato | Tartu Observatory, University of Tartu | Estonia |
| Nina Kessler | Laboratoire d'Astrophysique de Bordeaux | France |
| Patricia Fernández-Ruiz | Centro de Astrobiología | Spain |
| Pedro Kurmi Humire Rodríguez | Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo | Brazil |
| Pedro M. Martins | Institute of Astrophysics, University of Lisbon & RAEGE-Az | Portugal |
| Raquel Nohemy Mejia Espinoza | Universidad de Guanajuato | Mexico |
| Raúl Fuentetaja Álvarez | Instituto de Física Fundamental | Spain |
| Samantha Scibelli | National Radio Astronomy Observatory | United States |
| Simranpreet Kaur | Institute of Space Sciences (ICE- CSIC) | Spain |
| Sofia Kankkunen | Aalto University, Metsähovi Radio Observatory | Finland |
| Teresa Huertas-Roldán | Instituto de Astrofísica de Canarias | Spain |
| Veena Vadamattom Shaji | Max Planck Institute for Radio Astronomy | Germany |
| Weronika Puchalska | Institute of Astronomy, Nicolaus Copernicus University | Poland |
Abstracts
The provisional list of the abstracts presented on YERAC 2024 can be found here.
Aleksandra Krauze
Nicolaus Copernicus University in Toruń, Poland
Studies of compact AGNs at low frequencies with LOFAR
There are still many questions and uncertainties when it comes to the evolution of radio galaxies. Compact AGNs, such as Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS), are believed to be precursors to classical double radio galaxies. Some hypothesise that this evolution is much more complicated than previously assumed - those sources can be temporarily frustrated by their host environments or even transient on short timescales. The low-frequency radio observations allow us to observe the oldest plasma and study the earliest history and dynamics in young AGNs.
In this work, I will present the results of the LOFAR study of a sample of 90 CSS sources. We modelled the synchrotron spectra using LoTSS and LoLSS measurements and looked for halos around GPS/CSS sources as a probe of past cycles of radio activity. We will provide an update on our project as we are currently working on imaging the data with the LOFAR-VLBI pipeline for a subset of the 25 most suitable sources.
Andrés Megías Toledano
Centro de Astrobiología (CSIC-INTA), Spain
Chemical complexity in starless and pre-stellar cores
Observations carried out toward starless and pre-stellar cores have revealed that complex organic molecules are prevalent in these objects, but it is unclear what chemical processes are involved in their formation. In 2016, Jiménez-Serra et al. observed the L1544 pre-stellar core and found that complex organic molecules are preferentially produced at an intermediate-density shell at radial distances of several thousands astronomical units with respect to the core center. Later, in 2021, Jiménez-Serra et al. performed similar observations toward the L1498 starless core, believed to be at an earlier stage of evolution than L1544.
In this contribution, I will present a related study (Megías et al., 2023) toward another starless core, L1517B, which seems even younger than L1498 and L1544. We carried out observations of L1517B at 3 mm using IRAM 30 m radio telescope at Pico Veleta, Spain. We observed a lower level of chemical complexity than in L1498 and L1544, and we suggest that the differences between these three cores are due to their evolutionary stage. We propose that nitrogen-bearing organics are formed first followed by the oxygen-bearing ones, once the catastrophic depletion of CO sets in.
Additionally, we performed simulations of L1517B with the astrochemical code MONACO (Vasyunin et al., 2017), comparing the predictions with the observed abundances. Another young core, L1521E, is also compared with L1517B, although its observations are not completely equivalent to ours (Nagy et al., 2019; Scibelli et al., 2021). Lastly, we tested the use of the ratio HC3N / CH3CN as a proxy for the evolutionary stage in a set of 25 sources with different ages.
Ann Njeri
Newcastle University, United Kingdom
Exploring the extragalactic radio source population at high resolution with wide-field VLBI surveys and paving the way for SKA.
Deep radio surveys of extragalactic fields trace a large range of spatial and brightness temperature sensitivity scales. Therefore, have differing biases to radio-emitting physical components within galaxies (star formation, radio jets, AGN cores…). A combination of sensitivity and high angular resolution imaging over a range of spatial scales (arcsec to mas) is required to sucessfully characterize the relative contribution of radio emission associated with these processes. To isolate AGN contribution from star formation, we hypothesise that there exists a brightness temperature cut-off point separating pure AGN from star formation, for which very long baseline interferometry (VLBI) is crucial to establish. I will present a multi-resolution (a few pc to kpc scales) view of the transition between compact AGN and diffuse star formation through deep wide-field radio imaging (using EVN, e-MERLIN, VLBA, VLA of two extragalactic deep fields). I will show how the different spatial scale reveal a range of different structures, including showing a potential transition between star formation and pure AGN. I will also discuss how these results can inform future SKA observations, in relation to survey biases, de-coupling AGN and star-formation and addressing key technical challenges for processing the data.
Antonio Martínez-Henares
Centro de Astrobiología (CAB), CSIC-INTA, Spain
Modeling of the High-velocity Jet Powered by the Massive Star MWC 349A
Jets and disk winds arise from materials with excess angular momentum ejected from the accretion disk in forming stars. How these components are launched and how they impact the gas within the innermost regions of these objects remains vastly unknown. MWC349A is a massive star that presents a circumstellar disk which rotates following a Keplerian law, and an ionized wind that is launched from the disk surface. ALMA observations of the strong, maser emission of hydrogen radio recombination lines (RRLs) obtained toward this system provide a detailed picture of its ionized environment with a position accuracy down to a few AU scales. The analysis of the unresolved H30α and H26α RRL emission in conjunction with the 3D non-LTE radiative transfer model MORELI reveals the existence of a high velocity ionized jet with a velocity of 250 km/s launched from the disk and engulfed within the ionized wind. Our model shows that the bipolar jet is poorly collimated and slightly misaligned with respect to the disk rotation axis. We present additional ALMA observations of the H26α maser in the most extended configuration of the array with a resolution of 0.02” that resolves the RRL emission for the first time. The resolved emission allows to identify the disk, wind and jet components, and is in agreement with the model developed to fit the unresolved emission. Our results show the huge potential of RRL masers as powerful probes of the innermost ionized regions and of the high-velocity jets from massive stars.
Candela Chico Herrera
Universidad Complutense de Madrid, Spain
Simulations for the inclusion of the next generation SKA radio telescopes in the global VLBI networks
The calibration and imaging of Very Long Baseline Interferometry (VLBI) observations is challenging and the optimisation of calibration, imaging and scientific analysis requires significant human interaction. This makes the process dependent on subjective experience and knowledge. Recent developments to automate and improve the simulation, processing and analysis of VLBI observations have been applied to Event Horizon Telescope (EHT) observations.
The aim of this work has been to perform simulations using the EHT Imaging Package to inform how a VLBI network will operate, including the future SKA1 telescopes under construction in South Africa and Australia (known as the SKA-VLBI capability). To make the most of the new telescopes, it will be necessary to promote the development of VLBI networks in the southern hemisphere, both in Africa and in South America. The simulations provide information on the most optimal network configurations.
Cosima Eibensteiner
NRAO Charlottesville, United States
PHANGS-MeerKAT and MHONGOOSE HI observations of nearby spiral galaxies: physical drivers of the molecular gas fraction, Rmol
The molecular-to-atomic gas ratio is of crucial relevance to our understanding of the evolution of the interstellar medium in galaxies. In my talk, I show where the atomic gas balances the molecular ( Σatom ≈ Σmol) in nearby galaxies using new high-quality observations from MeerKAT and ALMA, for HI and CO, respectively, and how it depends on global galaxy properties. We define the transition from atomic to molecular dominated phase similar to other studies as Rmol = Σmol / Σatom = 1 and measure how Rmol depends on local conditions in the galaxy disks supported by multi-wavelength observations (from MUSE, GALEX, SPITZER, and WISE). For this we use a compiled dataset containing new observations from the MeerKAT telescope targeting the galaxies NGC 1512, NGC 4535, and, NGC 7496, from the first results of the PHANGS-MeerKAT survey (PI: D. Utomo, and in the future including 10 more galaxies; PI: D.J. Pisano) and together with the galaxies IC1954, NGC 1566, NGC 1672, NGC 3511, and NGC 5068 from the MHONGOOSE survey (deBlok+2024) form a sample of eight nearby (D = 5.2 - 19.4 Mpc) spiral galaxies that have the required multi-wavelength observations available. With upcoming high-sensitive and high-resolution observations with MeerKAT, the analysis I present forms a first step towards the investigation of how global galaxy properties (stellar mass, star formation rate, or morphology) impact the conversion from atomic to molecular gas in nearby galaxies (D < 20 Mpc or z < 0.005).
David Alonso López
Universidad Complutense de Madrid, Spain
Mapping the diffuse magnetised gas in the Shapley supercluster
Most of the ‘missing’ baryons in the local Universe are expected to reside in some diffuse gas phase of the intergalactic medium. In fact, recent results from X-ray absorption studies and Fast Radio Bursts indicate that all the baryons are essentially accounted for, but it remains to be determined exactly where they lie. Studies that cross-correlate galaxies with the thermal Sunyaev-Zel’dovich (tSZ) maps from Planck indicate that up to 50% of the baryons may be spread throughout filamentary structures in superclusters at low redshift. A wide-area rotation measure (RM) Grid is able to reveal ionised and magnetised gas in the outskirts of a galaxy cluster beyond that typically probed by X-rays. We will use the RM catalog from the POSSUM Pilot 2 survey of the Shapley supercluster, from both Band 1 and 2, in an attempt to map the diffuse magneto-ionic material extending from the individual galaxy clusters and into the connecting filamentary structures. The Shapley supercluster (z ~ 0.05) contains the largest concentration of Abell clusters (~25) in the local Universe, spread over 100’s of Mpc and 10’s of degrees on the sky. The distribution of clusters displays a complex morphology, with walls and filaments of galaxies extending from the three main interacting Abell clusters (A3556-A3558-A3562). It provides an ideal laboratory to study the diffuse gas expected to permeate these structures. In particular, we expect that we will be able to map the magnetised gas on scales of >~0.4 Mpc.
Where this study will excel in particular is in mapping the distribution of the magnetised gas in the outskirts of the Abell clusters and in the connecting filaments between the Abell clusters within the supercluster.
David Fernández Gil
CEFCA, Spain
J-HERTZ: a radio counterpart catalogue for J-PLUS
We present J-HERTZ (J-Plus Heritage Exploration of Radio Targets at Z < 5) a new value-added catalogue associated with the J-PLUS DR3 release, including sources with counterparts at low radio frequencies detected by the LOFAR LoTSS DR2 survey. The catalogue comprises about 470k objects within a common area of approximately 2100 deg².
J-HERTZ includes a machine-learning classification of the galaxies, QSOs and stars in the survey, based on Bayesian neural networks (BANNJO S, del Pino et al. 2024, submitted). Additionally, BANNJOS provides new photometric redshifts for sources without previous spectroscopic observations. The complete catalogue includes 370k galaxies, 30k QSOs and 20k stars detected with high confidence (r < 20 mag).
In this work we describe the main properties of these three populations, including the galaxy stellar masses derived from CIGALE fitting to the J-PLUS photospectra (Arizo et al. in prep.), the AGN luminosity and radio-loudness distribution, and the presence of stars with activity at radio frequencies. J-HERTZ is publicly available through the J-PLUS DR3 online repository.
David Haasler García
Centro de Astrobiología (CAB, INTA-CSIC), Spain
First extragalactic detection of a phosphorus-bearing molecule with ALCHEMI: Phosphorus nitride (PN)
Phosphorus (P) is a crucial element for life given its central role in several biomolecules. P-bearing molecules have been discovered in different regions of the Milky Way, but not yet towards an extragalactic environment. We searched for P-bearing molecules outside the Milky Way towards the nearby starburst Galaxy NGC 253.
Using observations from the ALMA Comprehensive High-resolution Extragalactic Molecular Inventory (ALCHEMI) project, we used the MAdrid Data CUBe Analysis package to model the emission of P-bearing molecules assuming local thermodynamic equilibrium (LTE) conditions. We also performed a non-LTE analysis using SpectralRadex.
We report the detection of a P-bearing molecule, phosphorus nitride (PN), for the first time in an extragalactic environment, towards two giant molecular clouds (GMCs) of NGC 253. The LTE analysis yields total PN beam-averaged column densities N = (1.20 ± 0.09) × 10^13 cm−2 and N = (6.5 ± 1.6) × 10^12 cm−2, which translate into abundances with respect to H2 of χ = (8.0 ± 1.0) × 10^−12 and χ = (4.4 ± 1.2) × 10^−12. We derived a low excitation temperature of Tex = (4.4 ± 1.3) K towards the GMC with the brightest PN emission, which indicates that PN is sub-thermally excited. The non-LTE analysis results in column densities consistent with the LTE values. We also searched for other P-bearing molecules (PO, PH3, CP, and CCP), and upper limits were derived. The derived PO/PN ratios are < 1.3 and < 1.7. The abundance ratio between PN and the shock-tracer SiO derived towards NGC 253 follows the same trend previously found towards Galactic sources.
Comparison of the observations with chemical models indicates that the derived molecular abundances of PN in NGC 253 can be explained by shock-driven chemistry followed by cosmic-ray-driven photochemistry.
David San Andrés de Pedro
Centro de Astrobiología (CAB, INTA-CSIC), Spain
First detection in the interstellar medium of the high-energy isomer of cyanomethanimine: H2CNCN
We present the first detection in the interstellar medium of N-cyanomethanimine (H2CNCN), the stable dimer of HCN of highest energy and the most complex organic molecule identified in space containing the prebiotically relevant NCN backbone, a fundamental structure of RNA and DNA purine nucleobases. We have identified a plethora of rotational transitions of H2CNCN towards the Galactic Center G+0.693-0.027 molecular cloud, through its recently improved ultra-high-sensitivity spectral survey using the Yebes 40 m and IRAM 30 m radio telescopes. This cloud is the only interstellar source showing the three cyanomethanimine isomers so far (including the Z- and E- isomers of C-cyanomethanimine, HNCHCN). We have performed a LTE fit to the observed data, deriving a total molecular abundance with respect to H2 of (2.1±0.3)e-11. This sets N-cyanomethanimine as one of the least abundant species detected thus far in this region, which demonstrates how the growing efforts in achieving a greater sensitivity on the observational data are pushing the limits of molecular species detectability in space. We have also revisited the previous detection of E- and Z-HNCHCN, and found a total C/N-cyanomethanimine abundance ratio of 31.8±1.8 and a Z/E-HNCHCN ratio of 4.5±0.2. While the latter can be explained on the basis of thermodynamic equilibrium, chemical kinetics are more likely responsible for the observed C/N-cyanomethanimine abundance ratio, where the gas-phase reaction between methanimine (CH2NH) and the cyanogen radical (CN) arises as the primary formation route.
Davide Belfiori
University of Bologna (INAF - IRA), Italy
The magnetic field structure of the central region of the starburst galaxy NGC253
Observations of polarized light at far-IR and sub-millimeter emitted by magnetically-aligned dust grains can be used to map the orientation of the magnetic fields in the plane of the sky in the cold regions of the interstellar medium such as molecular clouds, where the star formation takes place. We present the analysis of ALMA polarization observations in band 4 (~140 GHz) and 7 (~350 GHz) of the central regions of the galaxy NGC253, a very well studied nearby starburst galaxy. This galaxy's central area exhibits a complex structure characterized by 14 dense clumps of molecular gas, likely hosting young super starclusters. The intense feedback from the starburst region manifests as various structures in the molecular gas, including bubbles, streams, and a prominent multiphase outflow at scales exceeding kiloparsecs.
We obtained a detailed parsec-scale map of magnetic field structures in the galaxy, exploring their relationship with the outflow and super starclusters. The findings suggest a significant role of magnetic fields in the collimation of the outflow, and highlight a correlation between polarization structures and the presence of super starclusters.
This investigation contributes valuable insights into the interplay between magnetic fields, molecular outflows and star formation in nearby galaxies.
Denisha Shanice Pillay
Max Planck Institute for Radio Astronomy, Germany
MPIfR-MeerKAT Galactic Plane Survey (MMGPS) I: System setup and early results
Pulsars are highly magnetised, rapidly rotating neutron stars that emit beams of electromagnetic radiation from their magnetic poles and are remarkable laboratories for testing theories of gravity, studying neutron star interiors, and constraining equations of state. Previous surveys searching for such intriguing objects have provided high-impact science results, and new-generation radio telescope sensitivities enable more exciting discoveries.
The Max-Planck-Institut fur Radioastronomie (MPIfR) MeerKAT galactic plane survey (MMGPS) is an ongoing commensal survey that aims to maximise the scientific return by covering multiple science cases (pulsars, fast transients, Galactic and extragalactic magnetism and Galactic star formation) simultaneously. The primary pulsar science objective of the MMGPS is to find previously undetected compact relativistic binary pulsars along the Galactic plane and use such systems to probe general relativity in the strong field regime. The MMGPS has been partitioned into three parts: the MMGPS-L band (1.4 GHz observations of the Galactic plane), MMGPS-S band (~2.4 GHz observations close to the Galactic plane) and MMGPS-SgrA* (high-frequency end of S-Band (~3 GHz) observations centred on Sagittarius A*). The L-band portion of the survey has been completed, yielding 74 pulsar discoveries (16 binary systems, 2 double neutron star systems and a few nulling pulsars) and the S-band portion of the survey is currently underway.
Elisa Masa Andrés
Observatorio Astronómico Nacional (OAN-IGN), Spain
M1-92: multi-species modelling and the death of a star
Ongoing improvements in the sensitivity of sub-mm- and mm-range interferometers and single-dish radiotelescopes allow the more and more detailed study of pre-planetary nebulae in molecular species other than $^{12}$CO and $^{13}$CO. With a new update introduced in the modelling tool SHAPE+shapemol, we can now create morpho-kinematical models to reproduce observations of these shells in up to 10 different molecular species, allowing an accurate description of their physical features as well as their molecular abundances and isotopic ratios.
The pre-planetary nebula M1-92 (Minkowski's Footprint) is one of the most complex objects of this kind, with a wide range of physical conditions and more than 20 molecular species detected. We model this nebula, reproducing the observational data from IRAM-30m spectra and NOEMA interferometric maps, trying to understand the unusual evolution of its central star in the last phases of its life.
The results show interesting features that tell us the story of its death. The low-density and high-temperature areas of turbulent gas found across the nebula's symmetry axis suggest a periodic mass ejection that could still be happening. A $^{17}$O/$^{18}$O isotopic ratio of 1.6 indicates that the central star should have turned C-rich by the end of the AGB, as opposed to its O-rich nebula. The most plausible way of reconciling this discrepancy is that M1-92 resulted from a sudden massive ejection event, which also interrupted the AGB evolution of the central source, preventing its transformation into a C-rich star. We also detect different ratios of $^{12}$C/$^{13}$C across the nebula, which is particularly relevant in the inner equatorial region traced by HCO$^+$ and H$^{13}$CO$^+$, indicating an isotopic ratio variation taking place at some point during the last 1200 yr.
Emanuele De Rubeis
Istituto di Radioastronomia (INAF-IRA), Italy
Revealing the sub-arcsecond nature of radio galaxies in Abell 2255
The LOw Frequency Array (LOFAR) is an interferometer that operates at frequencies between 10 and 240 MHz. The facility consists of 52 stations. 14 “international” stations are spread throughout Europe: they provide baselines of up to 1989 km, which yields an angular resolution of 0.27” at 150 MHz. Using the full International LOFAR Telescope (ILT) is however technically challenging in terms of both calibration and data volumes: these difficulties caused the ILT to be not intensively used in the previous years, and so just a small number of publications was produced. The turning point is represented by the development of a pipeline by Morabito et al. (2022) which allows the calibration and imaging of targets within LOFAR’s field of view at sub-arcsecond resolution.
I will show the results from the ILT observations of the galaxy cluster Abell 2255. In particular, the main focus is on the “tails” of the four main radio galaxies that characterize the cluster environment, namely the “Original Tailed Radio Galaxy (Original TRG)”, the “Goldfish”, the “Beaver”, and the “Embryo”. These head-tails show extended synchrotron radio emission on 100s kpc-Mpc scales at 144 MHz up to resolutions of 5.0” x 3.8” (Botteon et al., 2020). But, at this moment, no LOFAR-VLBI observations at sub-arcsecond resolution have been performed for these radio galaxies to study their interplay with the merging cluster environment and try to reveal the nature of their filamentary structure. Particular attention is given on the data handling, that represent a crucial point for the correct exploitation of the “international stations” (IS), as well as an important testing ground for the future SKA infrastructure.
The goal of this work is then to use LOFAR long-baselines data to study the structure of the main tails observed in A2255. These preliminary results have been obtained with just a small number of observations (64 hours at the moment) with respect to the huge amount of data that will be available and will be put together (around 250h of observations) in the following months, with the aim to show a unique view of these sources at arc-second and sub-arcsecond resolution.
Erwan Rouillé
LESIA, Paris Observatory, France
An Instrumental Simulation tool for radio interferometric swarm of satellites
The sky has been observed through a large panel of wavelengths but the low frequency sky (<10MHz) remains mostly unknown. Innovative science concepts have emerged to measure it. One of them, NOIRE (Nanosatellite for a Radio Interferometric Observatory in Space)[1], aims to deploy a swarm of about 50 nanosatellites in lunar orbit to perform interferometric measurements. Designing such an instrument requires an intensive study on the system specifications which can be tested with a simulation. However, NOIRE presents unique constraints and specifications that cannot be reproduced by current simulation tools for radio interferometers. In this talk I will present NOIRE concept and its objectives before explaining the challenge it represents for its simulation. Then, I will give an overview of how I designed my simulation tools and show some results produced thanks to it. [1] B. Cecconi et al 2018
Fengwei Xu
I. Physikalisches Institut, Universität zu Köln, Germany
From ASHES to ASSEMBLE: A Dynamic View of Massive Protocluster Formation and Evolution
The ALMA Survey of Star Formation and Evolution in Massive Protoclusters with Blue Profiles (ASSEMBLE) aims to investigate the process of mass assembly and its connection to high-mass star formation theories in protoclusters in a dynamic view. We observed 11 massive (Mclump>1000 Msun), luminous (Lbol>10,000 Lsun), and blue-profile (infall signature) clumps by ALMA with a resolution of 2200-5500 au at 350 GHz (870 um) in continuum and line emission. 248 dense cores were identified, including 142 prestellar core candidates and 106 cores showing protostellar signatures. Compared to early-stage infrared dark clouds (IRDCs), the core mass and surface density within the ASSEMBLE clumps exhibited significant enhancement, suggesting concurrent core accretion during the evolution of the clumps. The maximum mass of prestellar cores was 2 times larger than that in IRDCs, indicating evolved protoclusters have the potential to harbor massive prestellar cores. The mass relation between clumps and their most massive core (MMCs) is observed in ASSEMBLE but not in ASHES, which is suggested to be regulated by continuous mass accretion. The mass correlation between core clusters and their MMCs has a steeper slope compared to that observed in stellar clusters, which can be due to the fragmentation of the MMC and stellar multiplicity. We observed a decrease in core separation and an increase in central concentration as protoclusters evolve, which can be explained by gravitational contraction. We confirm primordial mass segregation in the ASSEMBLE protoclusters, possibly resulting from gravitational concentration and/or gas accretion.
Hannah Walker
University of Leeds, United Kingdom
Radio Emission in Massive Protostars: Characterising the Properties of Jets
Recent surveys have shown that massive protostars display signs of radio emission similar to that seen in lower mass stars. Based on the alignment of this emission, and considering the molecular gas distribution, it can be reasonably assumed to arise from jets, as opposed to other radio sources such as HII regions. Although a limited number of observations have been taken to confirm the nature of this emission, the aim of the research here is to further characterise the properties of radio jets in massive protostars. A limited number of protostars have been chosen with clear jet structures, as seen in existing VLA data. Both C and K band VLA data will be analysed to determine the morphology and velocity of these jets, including any variability. Variability within the jets may suggest towards episodic accretion in the formation process, a mechanism which overcomes the ‘luminosity problem’ associated with high mass star formation. An in-depth study into the velocity, spatial and collimation changes of the radio jets will hopefully provide some extra insight into the formation process of massive stars.
Jaime Alonso Hernández
Centro de Astrobiología (CSIC-INTA), Spain
Effects of (internal) UV and X-ray emission in AGB's envelopes
In this presentation, I will show the results from our current project to study AGB stars with ultraviolet and X-ray emission. This recently discovered, yet poorly characterized class of uv/xAGB stars could represent a hidden group in the population of symbiotic stars with AGB donors.
I will report on our CO emission survey of a sample of uv/xAGB stars carried out with the IRAM 30m milimmeter radio telescope (MRT). This CO-based study has enabled us to characterize for the first time the properties of the molecular envelopes of these uv/xAGB stars (binary candidates) as class (Alonso-Hernandez, in press). Using the rotational diagram technique we estimate the main circumstellar envelope (CSE) physical parameters. From our analysis, we find that the gas/dust ratio is lower in our sample than in previous surveys of standard AGB stars with similar mass-loss rates.
I will also show preliminary results from our ongoing study to characterize the dust properties of xxx, based on SED modelling and infrared spectroscopy, and the chemical composition of the CSEs of a subsample of 2 xAGB and 2 uvAGB stars, based on a sensitive line search for HCO+ emission with the IRAM 30m MRT. Our analysis indicates that HCO+ is an X-ray sensitive specie and its abundance is enhanced by the internal X-ray emission in xAGBs.
Jort Boxelaar
INAF - IRA, Bologna, Italy
LOFAR Legacy 58 MHz Survey of the 3CRR Catalogue
The Low Frequency Array (LOFAR) is currently the only instrument capable of deep, high-resolution imaging at frequencies below 100 MHz. Sources selected from the 3C catalogue are some of the best studied powerful radio galaxies, with the largest number of available sensitive and high (kpc-scale) resolution images at GHz frequencies, (still) driving our current understanding of their dynamics and energetics. However, a lack of instruments with sufficiently long baselines (combined with short baselines) at frequencies below 1 GHz, or a lack of robust calibration strategies, has prohibited any highly-resolved radio galaxy studies in the MHz regime. Observing at these low frequencies using the Low Band Antenna (LBA) system has proven challenging. However, over the past few years, our team has developed tools and strategies to solve both instrumental and ionospheric systematic errors, producing thermal noise limited images. With this work we calibrate and image the observations of the entire 3C(RR) catalogue. The final goal is to obtain a flux-limited legacy catalogue of radio images with the following unique combination of characteristics: (I) an observing frequency of 60 MHz, (II) a high resolution (< 10′′), and (III) good sensitivity to large scale emission.
Juliette Robuschi
Institut de Planétologie et d'Astrophysique de Grenoble, France
Protostellar outflow shocked regions: astrochemical laboratories at our disposal : The case of L1157
Chemical compounds, and notably organic molecules, are observed and thought to be formed during all star formation stages. Among all the molecules detected in the interstellar medium, we are particularly interested in the so-called interstellar Complex Organic Molecules (iCOMs), which are carbon bearing molecules containing at least 6 atoms, containing at least one atom other than carbon or hydrogen. Ever since the 70’s, when the first iCOM was observed, we are trying to explain their presence and their formation routes in the harsh conditions of the interstellar medium. In this study, we focus on two iCOMs: glycolaldehyde (CH2OHCHO) and ethanol (C2H5OH).
At present, we denote two possible ways of formation for these iCOMs: on the surface of dust grains, or in the gas phase, the latter being the one we are interested in here. In order to probe the evolution of gas phase organic chemistry, we are targeting the protostellar stage, during which ejection processes ( km/s) from the central object cause the formation of shocked regions. These shocks are the siege of a very specific chemistry, as radicals and species that were previously trapped on dust grains frozen mantles or in their core are released into the gas phase, where we observe them, and where they can react to form new molecules.
We focus on the study of the molecular outflow driven by the protostar L1157-mm, which displays three shocked-regions of different and well-constrained ages. Observations of these three regions, made with the help of the NOEMA interferometer, coupled with the knowledge of the ages of these shocks, allow us to probe the evolution of gas phase chemistry with time. Lastly, gas-phase chemical modelling of the source paired with the observations provides us additional understanding of how the detected iCOMs form.
Léontine Ségal
Institut de RadioAstronomie Millimétrique (IRAM), France
A statistical approach to infer molecular cloud conditions from multi-molecular lines analysis of Horsehead nebula observations
Stars form in the dense (≳ 10^5 cm-3 ) and cold (≲ 10K) cores of Giant Molecular clouds (GMC). Because the most abundant species H2 is invisible under these conditions, the gas properties are indirectly probed by the lines emitted from minor tracers as other molecular species. Estimates derived from a multi-species analysis necessarily rely on injected constraints (e.g., the cloud geometry), and can be significatively biased when this a priori knowledge is incorrect (Roueff et al., 2024). Developing analyzing tools adapted to multi-species observations is thus required to progress on our understanding of processes involve in star formation in GMC.
The survey of the Orion B cloud with the IRAM-30m telescope in the ORION-B Large Program (P.I.: J. Pety, M. Gerin) acquired a dataset of ~10^6 spatial pixels times 200 000 frequencies from 86 to 115 GHz, which allows us to detect signatures of numerous molecular species. To model heterogeneous properties of the gas along any line of sight towards a filament or a dense core, we introduce a radiative transfer multi-layer cloud model and we calibrated it on a portion of this dataset, the Horsehead nebula. Towards the low-J transitions of the CO and HCO+ isotopologues, this region exhibits diverse physical regimes, such as filaments and starless dense cores.
During this talk, I will present the results obtained during my Ph.D., namely the robust kinematics estimation of the H2 volume density (nH2) and the kinetic temperature (Tkin) and the gas.
Lucy Clews
The Open University, United Kingdom
The structure and evolution of radio jets in the nearby Universe
LOFAR’s Two Metre Sky Survey (LoTSS) is a wide-area survey that eventually will cover the entire northern sky at 6 arcsecond resolution between 120-168MHz. The recent second data release (DR2) contains approximately 4 million radio sources, 58% of which have good optical ID’s and spectroscopic redshift measurements, this is an exciting time for radio astronomers. The relationship between the structural evolution of jets and host galaxy environment is important in understanding galaxy formation, but less is known about the production of more unusual jet morphologies such as wide and narrow-angle tails and transitional sources. Ridgelines are a tool used to outline the path of a jet by connecting points of highest radio flux intensity. By fitting a parametric spline to these ridgelines, we have developed a model to quantify the variation of curvature with distance from the host galaxy. We have implemented curvature, along with surface brightness information, into a clustering algorithm to group jets based on their structure alone. We haven’t restricted the algorithm with conditions based on pre-existing classifications. I will present the results of using this method on an AGN catalogue of 56,000 sources from LoTSS DR2, examining relationships between structural groupings, environment and host galaxy properties such as luminosity and physical size. I will compare these results to known morphological classes.
Luis Peña-Moñino
IAA-CSIC, Spain
Looking for star-planet interaction in the CARMENES M-dwarf sample with radio observations
The interaction between an exoplanet and the incoming stellar wind is expected to induce auroral radio emission on the host star via the electron cyclotron maser mechanism, if the planet is located inside the Alfvén surface.
This auroral emission has some distinct features: it varies rapidly with time, shows a high degree of circular polarization and periodic enhancements that depend on the orbital period of the planet. Detecting this particular emission would make radio observations a new and independent method for detecting exoplanets.
The most common type of stars are M-dwarfs, which often host planetary systems. In many of these stars, their planets orbit so close to the star that they are well within the Alfvén surface, making them ideal candidates for detecting radio emission from star-planet interaction.
Here, we present results from a series of radio campaigns with the VLA and the uGMRT, aimed at detecting star-planet interaction in nearby (less than 16 pc) stars from the CARMENES sample that host short-period (less than 7 days) planets. We will discuss the implications of our results within models of star-planet interaction, which constraints relevant physical parameters of those planetary systems.
Marina Ruiz García
Observatorio Astronómico Nacional, Spain
Revealing dynamical resonances of bars in PHANGS galaxies
Bars are remarkable stellar structures which transport gas towards centers and drive secular evolution in galaxies. In this study we use NIR images and ALMA CO(2-1) maps from the PHANGS survey, tracing the stellar potential and the molecular gas distribution, to determine the position of the main dynamical resonances of the bars in our targets. We present here a useful catalogue of dozens of corotations (CR) in nearby galaxies, calculated through the gravitational torque method from García-Burillo et al. (2005). We measured the ratio of the CR to bar radius, and found a mean R_CR/R_bar = 1.16, with a standard deviation 0.39, consistent with the average value expected from theory. This catalogue also contains an extensive comparison with other bar corotation measurements from the literature, together with estimations of other relevant resonances such as the Lindblad Resonances, often associated with rings, emphasising the connection between bar dynamics and morphology.
Miguel Montero Vega
Universidad Complutense de Madrid, Spain
A molecular look at the local starburst galaxy M82
M82 (NGC 3034) is a nearby starburst galaxy with a high star formation rate caused by an interaction with its neighbour, M81. This object presents several emission lines which can trace the molecular gas in the galaxy. We study some of these at different scales, such as CO, HCO+, HCN, SiO, CS and CH+, with radio observations taken from Herschel, IRAM, Yebes 40m and NOEMA. In particular, the study of the emission and absorption of CH+ allows us to describe the properties of the regions of turbulent gas in the object, which have not yet been studied in detail for galaxies as close to us as M82. By being able to spatially resolve where these gas features are distributed in a nearby object, we can hope to compare them to the data available for other galaxies at higher redshifts and understand them in a deeper way.
Miren Muñoz Echeverría
Institut de Recherche en Astrophysique et Planétologie (Toulouse), France
NOEMA resolves the core of CL J1226.9+3332
We present the first detection and detailed mapping at high angular resolution (~ 4 arcsec) of the thermal Sunyaev Zel'dovich (tSZ) effect on a distant cluster with the NOrthern Extended Millimeter Array (NOEMA). We demonstrate the power of NOEMA to resolve the hot gas content at the core of high redshift clusters (z = 0.89). Furthermore, its precise interferometric spectral measurements allow us to untangle sources contaminating the tSZ signal from the thermal emission of the cluster, CL J1226.9+3332. We model the tSZ observed by NOEMA together with previous consistent single dish measurements and reconstruct the gas pressure profile from the very core to the outskirts of the cluster. With these results, we confirm the hot and disturbed nature of CL J1226.9+3332. We further discuss how the precise determination of the pressure profile slope at the different angular scales is key to reduce the current uncertainties on the hydrostatic mass estimates.
Mousumi Mahato
Tartu Observatory, University of Tartu, Estonia
Spectral ageing analysis of megaparsec-scale DDRGs: Dynamics of inner and outer lobes
One of the most outstanding issues regarding active galactic nuclei (AGN) is the recurrent activity in AGN. Notable evidence of intermittent nuclear activity in AGN is found in the form of double-double radio galaxies (DDRGs), characterised by the presence of two pairs of radio lobes, typically aligned along the same jet axis, indicating two distinct cycles of activity. Investigating the properties of DDRGs is of utmost importance to refine our understanding of the duty cycle of AGN activity and feedback processes in AGN. This study allows the reconstruction of episodic activity history through the analysis of radio spectra and the information of source morphology. The study of megaparsec-scale DDRGs (size > 0.7 Mpc) holds particular significance as their vast dimensions aid a clearer distinction between two episodes of activity, unlike smaller DDRGs (~300 kpc). This larger volume coverage and reduced likelihood of emission overlap from different epochs make them relatively easier to analyse.
In our ongoing research, we have selected a sample of 14 megaparsec-scale (or giant) DDRGs from the LOFAR Two-metre Sky Survey (LoTSS) sample. These DDRGs, with their high-quality LOFAR 144 MHz maps, form the cornerstone of our investigation. Crucially, low-frequency observations are key in accurately determining injection indices. Our objectives include determining the injection spectral indices of the newer and older activity represented by inner and outer doubles and scrutinising potential differences. We aim to estimate their spectral ages and constrain the duty cycle of AGN activity. In addition, our study focuses on examining the propagation of jets within the cocoon formed during the initial cycle, along with exploring the physical conditions and re-acceleration processes within the lobes. To achieve this, we have harnessed a wealth of multifrequency data, systematically acquired through our dedicated uGMRT band 4 (550-900 MHz) and JVLA S (2-4 GHz), C (4-8 GHz), and X (8-12 GHz) band observations. The strategic use of JVLA arrays across all frequencies has been pivotal, enabling us to obtain high-resolution arcsecond maps. These detailed maps are essential for our comprehensive analysis, allowing us to scrutinise the overall spectral characteristics, precisely identifying spectral breaks and accurately estimate spectral indices, injection indices for two cycles of activity, spectral ages and magnetic fields of various components. This study stands out as the pioneering exploration into the mapping and analysis of giant DDRGs across such a wide range of frequencies. Previous studies on spectral ageing in DDRGs were conducted, but they were limited to a handful of sources and lacked the extensive frequency coverage that our sample study offers.. Through our observations from the C & D arrays of JVLA, we have successfully captured most of the diffuse emissions associated with the DDRGs.
In the presentation at YERAC (2024), we will highlight a segment of our work specifically featuring a subset of 10 sources from our sample and the outcomes of modelling the source evolution, employing the JP and KP models facilitated by Broadband Radio Astronomy Tools (BRATS). We will also present our examination of asymmetries in the inner and outer doubles. Additionally, our findings delve into understanding the effects of the surrounding environment on these asymmetries and their potential connections to spectral age variations.
Nina Kessler
Laboratoire d'Astrophysique de Bordeaux, France
Complex organic molecules detected in hot cores with machine learning
Complex organic molecules (COMs) are abundant in regions surrounding massive protostars, also known as hot cores. These chemical species are detected in the gaseous phase with radiotelescopes that deliver instantaneous large bandwidth at high spectral resolution. An in depth analysis of (sub)millimetre spectra requires the iterative adjustment of models at local thermodynamic equilibrium (LTE). However, this method can be time consuming for complex cases in chemically rich environments, particularly with the exponential increase of observed data in the past decade. We develop a method based on machine learning to facilitate the analysis of complex (sub)millimetre spectra of COMs in wide band spectroscopic data. The resulting artificial neural network is able to learn the signature of chemical species in order to detect them within synthetic and observational data. Using this model to analyse data from large observational programs would benefit our understanding of physical and chemical processes by increasing the statistics on molecular differentiation in star forming regions. My intervention during the YERAC would be an opportunity to present this new method and our latest results.
Patricia Fernández-Ruiz
Centro de Astrobiología, Spain
Multi-scale study of sulphur chemistry in hot corinos
Hot corinos are compact (<100 au), hot (>100K) and dense (>1e7 cm-3) regions that arise during the formation process of solar-like Class 0 protostars. These objects are characterized for presenting a rich chemistry, with dozens of complex organic molecules (COMs) detected, some of them precursors of prebiotic molecules. As the protostellar system develops, these molecules will either be destroyed or incorporate onto the dust grains as ice. Therefore, to probe the initial conditions of planet formation, it is essential to study the abundances of molecules in the early stages of star formation.
Our study is mainly focused on the sulphur bearing species. Sulphur is one of the elements that play a key role in biological systems and it has been proposed as a necessary catalyst to form amino acids in the interstellar medium. Unfortunately, from all the observed sulphur bearing molecules, we only find 5% of the cosmic abundance of sulphur atoms and do not yet know where the rest of it might be found. A possibility is that this element could be locked as a semi-refractory material that cannot be detected with our instruments, but this mystery remains unsolved.
By exploring the sulphur chemistry of the hot corinos observed in the ECHOS project, in which we have protostars along different evolutionary stages, we will be able to understand the process that this element undergoes in its evolution. Moreover, the detailed comparison of the abundances of the detected sulfur species with complex chemical models can provide hints on the nature (volatiles, refractories) of the main sulphur reservoir in proto-planetary disks. Tracing the sulphur content from the molecular clouds to the protoplanetary disks will allow us to know where this missing element might be and how it was delivered to our planet.
Pedro Kurmi Humire Rodríguez
Instituto de Astronomia, Geofísica e Ciências Atmosféricas, Universidade de São Paulo, Brazil
Spectral Energy Distribution of NGC253, a multi-wavelength high resolution approach
Context. Studying the physical characteristics of nearby galaxies such as the pure-starburst galaxy NGC 253 observed at high resolution is essential for gaining insights into interstellar medium (ISM) conditions at high redshift and understanding their formation and evolution over cosmic epochs. The advancements in ground-based and space-based instruments in recent decades have provided unparalleled multi-wavelength information. To fully leverage this wealth of information, extracting insights from the Spectral Energy Distribution (SED) is imperative.
Aims. The main scope of this work is to produce the first high-resolution (3′′) multiwavelength SED, covering optical to sub-mm/cm regimes, of an extragalactic source. We have chosen the well-studied Central Molecular Zone (CMZ) of the nuclear starburst NGC 253 and focused on its nuclear giant molecular clouds (GMCs, ∼30 pc size) that account for half of its star formation.
Methods. To compute the SEDs, we use the recently published Python/C++ code Galapy, particularly designed to study local and high-redshift galaxies. Galapy offers a user-friendly interface with state-of-the-art models such as the physically motivated in-situ Star Formation History model, capable of managing the infrared excess without sacrificing performance or experiencing prohibitive execution times.
Results. We retrieved optical to centimeter archival data for the inner regions of the CMZ of NGC 253 and were able to extract physical information from them, such as the star formation rate, in agreement with previous results. The present study also allows a direct comparison among ISM conditions between extragalactic and Galactic systems (e.g., the mini-starburst Sgr. B2 cloud).
Conclusions. This work has facilitated a direct comparison with mini-starbursting GMCs in our Milky Way's CMZ. Future prospects for this study involve utilizing public James Webb Space Telescope and high-resolution ALCHEMI (0′′.4) observations.
Pedro M. Martins
Institute of Astrophysics, University of Lisbon & RAEGE-Az, Portugal
Exploration of radio powerful AGN
One of the fundamental questions in astronomy is how galaxies form and evolve through cosmic time. For the past few decades, various teams have tried to answer this question by constructing computational models for simulated galaxies and their associated active galactic nuclei (AGN). With the next generation of telescopes currently developing survey strategies with a strong emphasis on exploring the early Universe (e.g., Athena in the X-ray and SKA in the radio regime), it is of the utmost importance to explore the predictions from state-of-the-art galaxy formation and evolution models, in particular at the Epoch of Re-ionization (EoR).
This project looks to implement improved recipes for radio emission, taking into account the most recent advances in our understanding of black hole accretion physics, together with current models for SMBH and galaxy evolution (e.g., EAGLE, GALFORM, Millennium). With these recipes, we will define new, more efficient criteria for the selection of AGN from radio observations, out to very high redshifts, allowing us to identify and analyze robust candidates for high redshift radio AGN in very sensitive surveys currently being performed (e.g., SKA Pathfinder and MeerKAT). This will allow us to optimize the design of the upcoming generation of whole-sky radio surveys, currently being developed for the future Square Kilometre Array telescope.
In parallel, this project is implementing a monitoring campaign of nearby AGN, using the Santa Maria radio telescope, part of the RAEGE network. This will complement the above approach by setting the framework to further explore the physical mechanisms behind AGN radio emission, as revealed by AGN variability. Here, the project will aim to perform a census of AGN monitoring efforts being made worldwide, in order to identify the best strategy for this program. We will also identify the impact of variability studies in the AGN accretion physics and evaluate how this can lead to improved recipes for radio emission.
Raquel Nohemy Mejia Espinoza
Universidad de Guanajuato, Mexico
The nature of the extremely high-velocity sources towards the HH80/81 region
The mechanism responsible for the formation of massive stars is one of the problems to solve in astrophysics nowadays. To understand the physical processes related to the formation of these objects, in recent decades studies in the millimeter wavelength range have focused on the detection of bipolar jets and molecular outflows present in the earliest stages of star formation, since this mechanism is the most commonly proposed candidate for dissipating angular momentum, thus facilitating the accretion of matter into the forming protostar.
In this work, we analyze the kinematics and excitation conditions with some transitions of CO and other molecular species (SiO, SO, etc.) of the molecular outflow driven by the largest and most well-collimated protostellar jet known in our Galaxy (∼10 pc of length in projection). This jet is associated with the massive protostar IRAS 18162-2048, located in the HH80/81 region at 1.4 kpc of distance. Additionally, associated with the driving source, there exists a compact, massive disk (r∼100au and 15-20 M⊙), surrounded by a larger, disk-like molecular envelope, where recently, the presence of accreting streamers has been detected. Furthermore, SMA observations have identified extremely high-velocity components (>100 km/s) near IRAS 18162-2048, denoted as molecular bullets of SiO, SO, and CO, which are likely direct ejections from the vicinity of the central protostar.
Our analysis reveals six molecular sources that exhibit extremely high velocities (EHV) in the southern part of the region with projected radial velocities of 20-40 km/s. These EHV sources present some very peculiar features that differ from the molecular bullets found in the vicinity of the central protostar: Our EHV sources show larger sizes and masses, misalignment and lack of symmetry with respect to the main axis of the outflow, and low collimation factors. The physical parameters derived from an LTE analysis suggest that the EHV sources are composed of cold gas implying that they are ”fossil” ejecta from the dense region near IRAS18162-2048, possibly due to radiative cooling and expansion in a low-density environment. Alternatively, using the RADEX under non-LTE assumption and considering that EHV sources might contain internal structure, we obtain higher temperatures (∼90 K) for possible small unresolved condensations (∼0.016 pc), potentially ejected by other embedded YSOs in the region, which remain undetected. Nevertheless, the peculiarities of EHV sources posses interesting scenarios to explain massive stars such as IRAS18162-2048. One scenario could involve episodic matter ejection scenario due to disk accretion bursts accompanied by a gradual change in the direction of molecular outflow, such as precession. Another possibility is that these EHV sources result from explosive outflows, similar to those observed in other high-mass star-forming regions, potentially linked to a protostellar merger or collision, as seen in G5.89-0.39 and Orion-KL.
Raúl Fuentetaja Álvarez
Instituto de Física Fundamental, Spain
The chemistry of the dark cloud TMC-1
The Taurus molecular cloud (TMC-1) is a dark cold cloud with a density of about 4x10^4 molecules/cm³ and a kinetic temperature of 10K, which has a carbon-rich chemistry.
The QUIJOTE survey in the Q-band frequency range (31-50GHz), carried out with 40m Yebes radio telescope, has allowed the detection of a large number of molecules, including those with low abundances and low dipole moments, thanks to high spectral resolution and long observing times.Recent sensitive radio astronomical observations such as TMC-1 has discovered a variety of previously unknown molecules, such as multideuterated molecules and protonated forms. Among the most remarkable discoveries are large hydrocarbons and aromatic molecules such as indene, the first polycyclic aromatic hydrocarbon detected in space.
The line identification process is based on several catalogues, such as MADEX, CDMS and JPL, which provide essential spectral data. However, despite the progress made, there are still a large number of unidentified lines, indicating that there is still much chemistry to be discovered in the interstellar medium.
Chemical models have proven to be incomplete in predicting the observed molecular composition, highlighting the need for updates based on new data. The observations demonstrated that TMC-1 has a crucial role to understand the chemistry of the interstellar medium and the formation pathways of large organic molecules.
Samantha Scibelli
National Radio Astronomy Observatory, United States
Complex Chemistry at the Earliest Stage of Low-mass Star Formation
Before low-mass (M ≤ few solar masses) stars like our Sun are formed, they are conceived inside cold (~10 K) and dense (> 10^5 cm-3) regions of gas and dust known as starless or dynamically evolved prestellar cores. It is essential to study the chemical complexity and evolution of prestellar cores because they set the initial conditions of star and planet formation. In recent years, it has been the detection of interstellar complex organic molecules (or COMs; any molecule with at least one carbon atom and six total atoms) in prestellar cores that has sparked interest in the star formation and astrochemistry communities, as COMs are believed to be important precursors to more biologically relevant species such as amino acids, DNA and RNA. And, it is with the use of single-dish submillimeter radio observing facilities, including the Arizona Radio Observatory (ARO) 12m, Yebes Observatory 40m, and Green Bank Observatory 100m Telescope (GBT), that we are able to systematically observe faint molecular lines at prestellar core scales (~ a few thousand AU). Here we present results from several surveys targeting a large (> 60) sample of starless and prestellar cores across three molecular clouds – Taurus, Ophiuchus, and Perseus. New COM detections are reported, including for methanol, CH3OH, methyl cyanide, CH3CN, acetaldehyde, CH3CHO, vinyl cyanide CH2CHCN, methyl formate, HCOOCH3, and dimethyl ether, CH3OCH3, which has more than doubled COM detection statistics in cold cores. Our results reveal COMs are prevalent earlier than previously thought and seeded early on before the formation of stars and planets.
Simranpreet Kaur
Institute of Space Sciences (ICE- CSIC), Spain
Circularly polarized modulated radio emission from a low-mass dipper star system: 2M0508-21
2M0508-21 is a young (<25 Myr old) M-dwarf binary system with a 6.7- hours photometrically observed period. It is known to exhibit IR excess emission, along with NUV and X-ray excess emissions and flares, in addition to a 10% dip seen in optical light curves. We observed this unique system at radio frequencies with the uGMRT band 4 (550-950MHz), covering twice 90% of the rotation period in two observations scheduled a month apart in 2023. We detected emission in both Stokes I and Stokes V with an S/N ∼ 25. The emission showed significant circular polarization ((about 40-60%), suggestive of being plasma emission or electron cyclotron maser emission, and carrying information about the magnetic fields present in the system. It also displayed peculiar variability in the circularly polarized signal when phase-folded. I will present our results of the radio observations in detail, along with shedding some light on the possible interpretations of the observed circularly polarized signal and its behavior in the context of the magnetic activity of the stars.
Sofia Kankkunen
Aalto University, Metsähovi Radio Observatory, Finland
Long-term radio variability of AGNs at 37 GHz
Active Galactic Nuclei (AGNs) are highly luminous sources at the centers of some galaxies. Their central supermassive black hole drives the variability of the sources causing changes in their observed light curves in different frequency domains. This variability is a common subject of studies as it may help in understanding the physical conditions governing AGN behavior.
The variability of AGNs has been observed to be slower in radio frequencies than other frequency domains. However, the timescales of radio variability have been difficult to characterize due to short monitoring periods which limits our ability to obtain reliable power spectral density estimates for the sources.
In order to understand the long-term behavior of AGNs, we analyzed 123 sources with up to 42 years of monitoring observed by the Metsähovi Radio Observatory 14-meter telescope in the 37 GHz band. We estimated the power spectra of the sources in order to probe for characteristic timescales. Characteristic timescales vary between sources and they should be connected to their physical properties.
We were only able to constrain the characteristic timescale for a small number of sources. This suggests that even up to 42 years of observations may sometimes not be enough to reliably identify low-frequency features in the AGN power spectra in the radio domain. Another limitation is the uneven observing cadence which sometimes reduces the resolution of the power spectrum significantly. For the few sources that we were able to constrain the timescale for, we found a preliminary connection between the time jet knots are visible in the 43 GHz VLBI images and the timescales derived from the power spectra.
Teresa Huertas-Roldán
Instituto de Astrofísica de Canarias, Spain
New molecular and deep RRL detections towards PNe
Planetary Nebulae (PNe) are known to host an extreme radiation environment that does not avoid the simultaneous presence of different types of molecules and single atoms. For this reason, PNe appear to be a unique laboratory where simple and complex molecules coexist. We will present our recent very deep (and high-resolution) radio observations of PNe IC 418 and NGC 7027, which have provided us a nice radio database of the molecular content of these objects. In our aim to study the complex organic molecules in the radio domain, we have found also very deep radio recombination lines (RRLs) of several neutral and ionized atoms never observed before. These new detected RRLs together with the molecular content give useful information about their circumstellar envelopes as well as the complex organic chemistry taking place in this kind of astrophysical environments.
Veena Vadamattom Shaji
Max Planck Institute for Radio Astronomy, Germany
A chemical Inventory of Molecular Gas in the Milky Way's Nuclear Chimney
The Galactic Centre (GC) is the most extreme environment in the Milky Way hosting high energy feedback processes and containing the central molecular zone (CMZ), the largest reservoir of molecular gas in the Galaxy. Due to its proximity, the GC is the best template to investigate gas dynamics and star formation in galactic nuclei to sub-pc scales. Recent studies reveal the existence of a multi-phase nuclear chimney extending hundreds of parsecs, which represent the channel connecting the quasi-continuous, intermittent activity at the GC. In order to understand the kinematics and chemistry of the cold molecular gas associated with this nuclear chimney we carried out a multiwavelength spectral line study of the chimney. Our studies reveal a funnel-shaped molecular structure in 13CO emission extending over a degree above the GC. This feature correlates well with the northern lobe of the 430 pc radio bubble, believed to be the radio counterpart of the multiwavelength GC chimney. Spectral line observations in the frequency range of 85–240 GHz reveal the rich chemistry of the cloud. The mean 12C/13C isotope ratio (30.6 ± 2.9) within the cloud is consistent with the structure located within or close to the GC. Our ongoing APEX survey of the molecular funnel also reveals molecular signatures of a large scale shock in the region, shedding light on the intricate processes and structures within this extreme galactic environment.
Weronika Puchalska
Institute of Astronomy, Nicolaus Copernicus University, Poland
The bursting activity of the magnetar XTE J1810-197
One of the most popular hypotheses to explain the origin of the Fast Radio Burst (FRB) is the rapid activity of magnetars combined with a spatial reconfiguration of their magnetic field. Magnetar XTE J1810-197 is one of the few known objects in the Milky Way that produces millisecond radio bursts but with a fluence much lower than known extragalactic FRB sources.
For over two years, the Nicolaus Copernicus University radio telescope in Piwnice has been regularly observing the object XTE J1810-197 in the 18cm (L-band) and 6cm (C-band) radio bands. A large observational sample has thus been collected, allowing for monitoring changes in the activity of XTE J1810-197 over a long period of time.
The talk will present the first preliminary results describing the statistical properties of the observed bursts and compare them with the existing FRB database to test the fast radio burst formation hypothesis.
