Detailed Program

November 11, 2024

Welcome

Tony Beasley

ngVLA: International Project Status

NRAO

Eduardo Ros

Charting new territories: high-resolution radio interferometry in the ngVLA era

MPI für Radioastronomie

The highest resolution in radio interferometry is achieved through the  utilisation of very-long-baseline interferometry at millimetre  wavelengths (mm-VLBI) or the deployment of antennas in space.  The most  recent findings from the Event Horizon Telescope and the Global mm-VLBI  Array have led to significant advances in our understanding of the  nature of supermassive black holes at the centres of active galaxies.   Presently, enhancements in digital back-ends, calibration procedures,  and imaging methods, in conjunction with the advent of multi-band  options, are significantly expanding the capabilities of VLBI at the  highest resolution.  This is in alignment with the objectives of an  advanced array operating at mm-wavelengths, as envisaged by the ngVLA.   In particular, the introduction of frequency phase transfer will result  in a significant enhancement in the sensitivity and positional accuracy  of radio interferometry at frequencies above 22 GHz, with an improvement  of more than an order of magnitude.  My presentation will discuss how  the ngVLA, which is equipped for intercontinental baselines, will bring a  new era of sensitivity and accuracy for the study of the most compact  and powerful objects in the universe. These include active galactic  nuclei, as well as galactic objects. Furthermore, observations of very  high-energy gamma-ray and neutrino interactions will be complementary to  radio data at the forthcoming era of multi-messenger astronomy.

Tirupati Kumara Sridharan

The ngVLA Calibration Concept

National Radio Astronomy Observatory 

The ngVLA opens up new discovery space impacting nearly every area of  astrophysics by combining two orders of magnitude in frequency coverage  with unprecedented sensitivity, spatial resolution and spatial frequency  coverage. In order to maximize science time, the science and system  requirements set a high observing system calibration efficiency goal of  90%. We present the calibration concept developed to meet these  requirements.    A driving highlight of the requirements is the high image dynamic range –  45 dB and 35 dB in continuum, in bands 2 & 4 (8 & 27 GHz). The  high sensitivity and the large array size which enable the pathbreaking  science goals also allow the wider use of self-calibration techniques,  only available in limited circumstances to previous generation  instruments. The ngVLA leverages these strengths for calibration. For  the higher frequency bands 5 & 6 (30 -116 GHz) while fast switching  is feasible, water vapor radiometry (WVR) is being assessed and  developed to lower the calibration overheads. Much of the calibration  information will be obtained and maintained by the observatory,  employing a high degree of automation and provided to individual  observations during execution and pipeline data processing to generate  high level data products (HLDP). Besides these strategies, the core of  the calibration concept follows well-known general principles and  approaches in practice at existing aperture synthesis interferometers.

Viral Parekh

Enable high-dynamic range imaging for ngVLA

National Radio Astronomy Observatory

The ngVLA is a next-generation radio astronomy observatory designed to explore planetary formation, star evolution, and galaxy formation with unprecedented sensitivity and resolution. It is expected to image low-surface brightness and complex emissions, such as those from the galactic plane, over a wide bandwidth and angular scales spanning from a few arcminutes to a few milliarcseconds. However, imaging these features is challenging in the presence of strong sources (a few Jy) in the field, which can corrupt the point spread function (PSF) and introduce artifacts that severely affect the science targets. Additionally, direction-dependent effects originating from the antennas in an interferometer, such as pointing errors, time and frequency-dependent primary beam variations, atmospheric effects, and imperfect mounts, further complicate calibration and imaging. High-dynamic range imaging is particularly important at low-frequency observations (< 3 GHz) where there are many sources in a given field-of-view, and some may be significantly brighter than the target of interest. To address these challenges, we are conducting ngVLA simulations of complex extended radio sources, incorporating strong radio sources in the visibility data alongside phase errors, primary beam variations, thermal noise, and delay offsets. Our primary goal is to remove these calibration errors from the simulated observations and image the target source with high fidelity and the expected dynamic range, considering ngVLA configurations and imaging parameters. In these simulations, we employ different extended and broadband models derived from recent high-quality MeerKAT data (L-band), such as the galactic plane and other diffuse radio sources (extended radio galaxies). We also utilize third-generation calibration software, including CubiCAL and QuartiCal, in addition to CASA, to perform advanced calibration for ngVLA.

Alfonso Trejo Cruz

Array performance at high angular resolution with ngVLA antennas in Mexico

Instituto de Radioastronomía y Astrofísica (IRyA-UNAM)

The Next Generation Very Large Array (ngVLA) will be the largest and most sensitive radio interferometer in the northern hemisphere. With its hundreds of antennas distributed across the US, Canada, and Mexico, the ngVLA will enable ultra-sensitive imaging of spectral line and continuum emission at milliarcsecond resolutions. Critical to these abilities, and therefore to the key science goals, is the MID array, a key component of the ngVLA that will provide some of the longest baselines of the new observatory. This translates into a high angular resolution that will in particular be enabled by the projected antennas in Northern Mexico. We will show that in general the array performance, including beam ellipticity and its artefacts, deteriorate when the antennas in Northern Mexico are not included in the MID array. Through a robust parameter space, including the configurations MID and MID+Spiral+Core, positional, and imaging-specific parameters, we discuss how more affected observations towards the Galactic center/plane would be, compared to those in the Northern hemisphere. While the beam properties vary for any specific parameter space combination, we find ellipticity increments of up to 1.4x when the antennas in Mexico are excluded from the configurations tested. In this work we also note the (high) angular resolution ranges more impacted by a hypothetical loss of antennas in Mexico. Finally, we discuss beam performance differences when using relatively short and long observations.

Lucas Hunt

Reference Frames in the ngVLA Era

NRAO

Sanjay Bhatnagar

ngVLA Data Processing Challenges: Algorithms, TeraBytes, & PetaFLOPS

National Radio Astronomy Observatory

The ngVLA offers over 10x or more improvement in overall imaging  performance compared, but at the cost of orders of magnitude increase in  the data rates and the size of computing.  Straight up, to take full advantage of these improvements necessitates similar improvements  in the calibration and imaging algorithms to also reliably deliver both,  high imaging and high runtime performance.  The estimated size of computing to process 100s of TeraBytes of data is  estimated to be in the 10s of PetaFLOPs range. To harvest the available  computing power, efficient parallelization at multiple scales, and a  different approach to algorithms design, hardware and software  development -- called the "Top of the compute stack" -- is necessary.  Deep engagement with the High Performance Computing (HPC) and High  Throughput Computing (HTC) communities is therefore necessary.  With the  rapidly evolving computing technology, substantive engagement with the  industry partners is also critical.  At the "New Eyes on the Sky" conference in 2023 we discussed initiatives  launched at NRAO to tackle these challenges, and develop new algorithms  to both, match the improvements in the imaging performance, and harvest  the available computing power. In this talk, we will present the status  and the progress made in these areas since then, discuss the scientific  and technical results, the lessons learned and the work in progress to  mitigate the issues encountered. In collaboration with HPC/HTC groups,  super-computing centers, and hardware vendors, these algorithms were  recently deployed on a network of 100s of GPUs to process data sets  which had remained un-processed till now.  These engagements have led to  awareness among the industry and external HPC/HTC groups of the RA  domain problems, and a better understanding in the RA groups of the  software and hardware technology roadmaps.  We will discuss these  results and the implications on the scientific usability of   next-generation telescopes.

László Viktor Tóth

Optimizing the Ecological Impact of Major Ground-Based Astronomical Facilities; a look at the ngVLA

ELTE

The ngVLA antennae with coupled devices and buildings are planned to be installed at various locations into various environments. Our ecological and social responsibility encourages us to minimize our local and global footprint and on the other hand to disseminate knowledge for all generations. A holistic approach to optimize the ecological impact requires a multidisciplinary evaluation including several scientific and technological areas such as material science, civil engineering, architecture, information technology, RF engineering, mechanical engineering, thermal engineering, electrical engineering, fire protection engineering, meteorology and climatology, earth observation, biology, physics, environmental science, sociology, education, project management, etc. We will flesh up ways to handle the issues, mentioning also best practices to be considered.

Nina Gusinskaia

Multiwavelength studies of neutron stars

University of Toronto

Astrophysical accretion occurs in a variety of contexts, and thus understanding the underlying processes can have broad application. In the case of accreting neutron stars, the deep gravitational well, ultra-strong magnetic field and rapid rotation are all ingredients that make them unique laboratories. The challenge is then to understand how these properties affect what we observe and, where possible, to compare and contrast with other astrophysical systems. In this talk I will present our multiwavelength studies of neutron star X-ray binaries and what such studies can teach us about accretion onto magnetized compact objects, stellar evolution and fundamental physics in the ngVLA era.

Alexander van der Horst

Radio breakthroughs in gamma-ray burst studies and the ngVLA potential

The George Washington University

Gamma-ray bursts are the most extreme cosmic explosions and emit across  the entire electromagnetic spectrum, detected from TeV gamma rays down  to sub-GHz radio frequencies. Their multi-wavelength emission allows for  studies of ultra-relativistic jets, extreme particle acceleration, the  final stages of life for the most massive stars, and the counterparts to  gravitational wave events. Radio observations play a crucial role in  probing gamma-ray burst physics, tracking the evolution of the broadband  spectrum for much longer than any other spectral regime, catching  phenomena that often go undetected in other parts of the spectrum, and  allowing for source size measurements of the nearest and brightest  gamma-ray bursts. We will discuss the physical insights we can get in  the radio regime, focusing on the progress that the ngVLA will bring  given its sensitivity and angular resolution. We will illustrate this by  presenting recent results on the Brightest Of All Time, GRB 221009A,  for which we will show radio light curves and spectral energy  distributions of unprecedented quality, allowing for the most detailed  study of a gamma-ray burst reverse shock; and also size measurement with  VLBI of the relativistic shock causing the emission of GRB 221009A. The  ngVLA has the potential to revolutionize the field by making the  quality of measurements we have for GRB 221009A, and a handful of other  gamma-ray burst with good spectral and temporal coverage, a common  occurrence for gamma-ray bursts of a typical radio brightness. We will  also show exciting initial results from an automated radio follow-up  campaign of many gamma-ray bursts, showcasing the scientific potential  of such a capability on the ngVLA. This program is detecting gamma-ray  bursts within 2 hours after the gamma-ray trigger, leading to the  earliest radio detections to date and unique insights into gamma-ray  burst physics.

Laila Vleeschower Calas

Using pulsars for testing gravity with the next generation telescope MeerKAT

University of Wisconsin - Milwaukee

Denis Leahy

Properties of radio pulsars in the ASKAP/ EMU and POSSUM surveys

University of Calgary

The Australia Square Kilometer Array Pathfinder (ASKAP) is a synthesis  radio telescope with 36 antennae equipped Phased Array Feeds, which is  currently carrying out a survey of the southern sky. The survey has high  sensitivity (rms ~20 microJy/beam) and good spatial resolution (~15  arcseconds) and will significantly expand radio measurements of  different (and new) classes of astrophysical objects. Current  information on ASKAP is given at the website  https://www.atnf.csiro.au/projects/askap/index.html. EMU is a radio  continuum survey and POSSUM is a polarization survey, incorporating  rotation measure (RM) synthesis, carried out with ASKAP. The work  reported here utilizes data from the first part of these surveys to  study radio pulsars using data from the EMU and POSSUM surveys,  including determination of spectra and RMs of pulsars.

Hao Ding

Pinpointing faint steep-spectrum sources with wideband ngVLA astrometry

National Astronomical Observatory of Japan

Michael Martinez

Gravitational Lensing constraints of Dark Matter in the ngVLA era

University of Wisconsin - Madison

Shami Chatterjee

Pulsars, Nanohertz Gravitational Waves, and the ngVLA

Cornell University 

Recent evidence for a nanohertz gravitational wave background from  NANOGrav and other pulsar timing arrays has once again highlighted the  role of pulsars as laboratories for extreme astrophysics. With its  combination of extraordinary sensitivity at higher radio frequencies and  high resolution from longer baselines, the ngVLA can play a significant  role in enhancing the scientific return from pulsar observations.  Higher frequency observations reduce the impact of pulse dispersion and  scattering, allowing meaningful constraints on the interstellar medium  along the lines of sight and discrimination of magnetospheric effects  from propagation effects. Further, very high precision astrometry may  enable the distance to specific pulsars to be measured to a small  fraction of the wavelength of nHz gravitational waves, enabling unique  constraints on individual GW sources and source populations from  observations of the most stable millisecond pulsars in the coming era of  nHz gravitational wave astronomy. I will briefly review these and other  applications of high sensitivity, high resolution observations of  pulsars with the ngVLA.

Joseph Lazio

Finding and Resolving Supermassive Black Hole Binaries

Jet Propulsion Laboratory, California Institute of Technology 

Galaxies merge, and a long-standing prediction has been that the  supermassive black holes (SMBHs) at their centers would sink to the  center of the merger product and form a binary.  Evidence for a  population of SMBH binaries is provided by a stochastic gravitational  wave (GW) background reported by the North American Nanohertz  Observatory for Gravitational Waves (NANOGrav) and other international  pulsar timing array (PTA) collaborations.  The data used by NANOGrav  were precise pulse times of arrival from a set of radio pulsars  distributed about the sky, with data collected by the Arecibo  Observatory, the Green Bank Telescope (GBT), and, most recently, the  Very Large Array (VLA).  Looking to the future, the next frontier is to find individual SMBH  binaries.  We identify four ways in which the VLA, the Very Long  Baseline Array (VLBA), and ultimately the ngVLA will be key elements of  identifying such individual SMBH binaries. First, NANOGrav continues to conduct precise pulsar timing observations,  and the VLA remains one of the North American telescopes from which  these data are obtained, particularly in light of the loss of the  Arecibo Observatory. Second, the VLBA has been used to determine geometric (parallax)  distances to millisecond pulars, which both improves the modeling of the  pulse timing observations for gravitational wave studies and may enable  direct studies of GWs emitted by individual SMBH binaries. Third, the VLBA has been used to search for pairs of SMBHs, prior to  forming a binary.  The ngVLA will continue this work, and, particularly  in the context of potential future space very long baseline  interferometry (VLBI) possibilities, the ngVLA could be a key element of  a ground-based array in combination with one or more space-based  antennas. Finally, the NANOGrav data are being used to search for specific GW  signatures. We shall provide an overview of this work.

Chris Carilli

Imaging the Supermassive Black Hole Region in M87

NRAO

The Global mm-VLBI Array (GMVA) has recently demonstrated the ability to  resolved what may be evidence for the relativistic shadow of the  super-massive black hole in M87 at 86 GHz, as well as to delineate the  inner jet to ∼ 1 mas distance (Lu et al. 2023, Nature, 616, 686). We  investigate the ability of the planned ngVLA and ngEHT, including  possible extra stations in south-central Mexico, such as at the LMT  site, to image such a nuclear ’ring’ on tens of microarcsecond scales,  and the associated jet to larger scales. We adopt a source model based  on the GMVA estimate of the nuclear 'ring' size, and a scaled version of  the best VLBA image of the M87 jet at 43 GHz. While the longest  baseline, and hence highest resolution fringe, does not improve relative  to the GMVA due to the limit set by the diameter of the Earth, the  ngEHT alone should provide both a higher fidelity image of the nuclear  source on scales ≤ 0.1 mas, and a good image of a more extended jet to ∼  1 mas. Adding the ngVLA improves substantially the dynamic range (by a  factor 3.5), as well as adds the ability to image structures on larger  scales, in this case out to at least 5 mas, and potentially to much  larger scales given the ∼ 3e5 range in spatial scales covered by the  combined array. Both arrays provide good image fidelity (≤ 0.1), in the  inner ∼ 1 mas,  but the ngEHT-only image does not reproduce the outer  jet well, or at all, with fidelity values greater than unity. The  combined array reproduces much of the outer jet with good fidelity (≤  0.3). Adding the ngVLA also decreases the susceptibility to  antenna-based phase errors by a similar factor, and improves the ability  for fringe fitting and subsequent phase and amplitude self-calibration.

Sridharan T.K.

The Black Hole Explorer (BHEX) - Mission Overview and ngVLA Synergies

National Radio Astronomy Observatory

The Black Hole Explorer (BHEX) is a mm/sub-mm space-VLBI mission under  development, targeting the study of super massive black holes (SMBH) at  the sharpest ever resolution of ~ 6 uas. In the 240-320 GHz band,  BHEX  pierces synchrotron opacity and interstellar scattering to detect the  “photon ring”  image feature around SMBHs, arising from light orbiting  them before escaping to the observer,  with Sgr A* and M87* as primary  targets. Through this detection BHEX will obtain the first direct  measurements of the block hole spin.  In the 80-106 GHz band it will  reveal extended emission in relativistic jets and binary supermassive  black holes that are prime targets for pulsar timing arrays. These  observations will elucidate both the growth of SMBHs and how they  launch, collimate, and power the most efficient engines in the universe.  BHEX is designed to conduct simultaneous dual polarization observations  in these two bands, with a 3.5-meter antenna, transmitting data through  a high rate (64 gbps) laser link.   The BHEX mission has strong synergies with future and current NRAO  telescopes ngVLA, ALMA and GBT among other ground facilities. Leveraging  the large ground collecting areas as anchors and large bandwidths allow  the 3.5-m space antenna to attain high VLBI sensitivities. The  unprecedented ngVLA collecting area and 3-mm operation enable two key  paths. (1) stand-alone 3-mm science with ~ 20 uas spatial resolution,  extending ngVLA’s ground based capabilities to study SMBH jets and the  black hole-jet connection, and (2) fringe finding and tracking at 3-mm  to increase coherent integration times at 1-mm, substantially increasing  1-mm sensitivity through frequency phase transfer. Thus, the  combination of ngVLA and BHEX in a hybrid observatory configuration with  other global facilities delivers science reach otherwise not feasible:  expansion of ngVLA Key Science Goal 5 (understanding the formation and  evolution of SMBHs) and opening new opportunities in fundamental  physics.

Flash Posters Monday

1. Amador Portes, Alfredo Mapping the Gamma-Ray Origins: Linking VLBA Jet Features to Fermi Activity in Blazars
2. Guerrero González, Jonhatan Uriel Reclassifying FSRQs: Insights from Radio Observations and Light Curve Analysis
3. Roman-Zuniga, Carlos VOLS Counterparts, from the Optical to the Infrared
4. Girart, Josep Miquel Variable, Circularly polarized radio emission from the Young Stellar Object BHB2007-1
5. Salinas, Javiera N2H+ evidence of filament rotation and evolution in the G012.80 protocluster Universidad de Concepción
6. Uscanga, Lucero Polarization observations with the ngVLA in low-mass evolved stars University of Guanajuato
7. Masqué, Josep María New perspectives on the study of massive star forming regions Universidad de Guanajuato
8. Ocegueda Sambrano, Erik y Enríquez, Paola The Relevance of Placing ngVLA Antennas at Tecnológico de Monterrey Campuses
9. Yanza Lopez, Vanessa The bow shock at the center of NGC 6334A with deep VLA observations.
10. Sandoval Garrido, Nicolás Protocluster evolution at the onset of massive star formation: contraction and rotation
11. Ordonez-Toro, Jazmin Dynamical Masses of Young Stellar Multiple Systems with the VLBA (DYNAMO-VLBA)
12. Durán, Aurora Inner structure of L1551 IRS5 binary system and its implication on the morphology at molecular outfl
13. Alquicira Peláez, Molecular emission from a protostellar jet-disk wind interaction
14. Rivera-Ortiz, Pedro Ruben Interaction of protostellar outflows

November 12, 2024

Andrei Lobanov

“Long baseline” science with the ngVLA and its potential transoceanic extensions

MPIfR - Bonn 

The unprecedented sensitivity and superb frequency coverage offered by the ngVLA are going to bring transformational opportunities to a broad range of astrophysical fields, in particular those relying on measurements made at the highest angular resolution. It will also offer numerous opportunities for worldwide synergies with existing and planned instruments operating in the same range of frequencies. One of such potential synergies is presented by the LEVERAGE initiative which envisages building up to three 15-m class antennas in Germany and operating them both in standalone mode and as outriggers of ngVLA. This and other potential similar initiatives may effectively extend the longest baselines of ngVLA to about 12,000 km, thereby providing about a factor of ~1.3 improvement of angular resolution. In addition to that, the effective image resolution achieved by ngVLA will be remarkably improved by the unprecedented sensitivity of the array, reaching, and perhaps even surpassing, the performance of the EHT and ngEHT at 230 GHz. Deriving from these aspects, some of the prospects of “high resolution” science which will arise with the ngVLA, also reaching out to transoceanic baselines, will be discussed in this talk.

Evan Sheldahl

Compact Symmetric Objects: Our Key to Understanding the Birth of Radio Jets

University of New Mexico 

Compact symmetric objects (CSOs) are a special class of radio-loud  active galactic nuclei (AGN) smaller than 1 kpc with their radio jets  oriented near the plane of the sky. For years after their discovery,  they fell by the wayside despite being morphologically distinct from  beamed AGN, which constitute the vast majority of known AGN. Recent  publications by members of my research team have revitalized the CSO  discussion and have shown that studying these sources may shed light  onto how radio AGN operate at early stages in their lives. Discovering  and verifying new CSOs necessitates resolving their morphologies as  accurately as possible, which requires the highest fidelity imaging  using Very Long Baseline Interferometry (VLBI). ngVLA will improve our  ability to definitively identify CSOs with its heightened uv-coverage,  allowing us to confidently image even fainter sources. In the meantime,  we need to compile observations of as many CSOs as possible to improve  our statistics and witness all stages of CSO development. To this end,  we have been expanding the list of known CSOs with Very Long Baseline  Array (VLBA) observations. I will detail my efforts discovering new CSOs  using the VLBA, present some analysis and curious cases along the way,  and explain how ngVLA will revolutionize this field.

Emilia Järvelä

Rapid high-amplitude radio variability in early-stage active galactic nuclei

Texas Tech University 

I report on the discovery of extreme 37 GHz radio variability originating from early-stage active galactic nuclei (AGN). Most of these AGN are narrow-line Seyfert 1 (NLS1) galaxies, harbouring fast-growing, low-mass supermassive black holes, accreting at high Eddington ratios as indicated by [O III] outflows and high R4570 values. These AGN exhibit amplitude variability of three-to-four orders of magnitude over e-folding timescales of a few days. However, despite our relentless attempts, we have not detected relativistic jets in these sources, and thus they might be displaying a totally new kind of variability phenomenon in AGN. Recently, one of these sources exhibited several 37 GHz flares and was followed up by the JVLA, Owens Valley Radio Telescope, Effelsberg Radio Telescope, and Swift XRT/UVOT. Based on these observations, we estimated an e-folding timescale of some hours, leading to variability brightness temperatures and variability Doppler factors that are extremely hard to explain by an incoherent emitter, suggesting a possible detection of coherent emission from an AGN. In this talk, I will present our multiwavelength investigation into this subset of AGN and discuss the importance of the ngVLA - especially its rapid trigger response, coupled with mas-scale resolution - for our efforts to understand and explain the nature of these extraordinary sources.

Takuma Izumi

Sub/parsec scale dynamic pictures of AGNs probed by long-wavelength observations

National Astronomical Observatory of Japan 

Since its advent, ALMA has dramatically improved our understanding on  the circumnuclear structures around AGNs from ~100 parsec down to,  finally, ~1 parsec. I first introduce our recent work on the sub-parsec  scale gas feeding and feedback observed in the Circinus galaxy (Izumi et  al. 2023, Science, 382, 554): we successfully identified, for example,  dense gas inflow toward, and ionized outflow from, the active  supermassive black hole. I will then discuss the current limitations of  ALMA, on angular resolution and sensitivity, to further expand our study  toward more distant AGNs with various characteristics (e.g., BH mass,  AGN luminosity, Eddington ratio). ngVLA will overcome these limitations,  hence will provide us a comprehensive view of multiphase, dynamic gas  properties of AGNs.   I will also introduce sub/mm time variability, or a minute-scale flare  in the Circinus galaxy. The time-scale of this flare is approximately 3  minutes, corresponding to a source size (radius) of about 12  Schwarzschild radii, indicative of the characteristic spatial scale of  the hot corona that emits strong hard X-ray. The high angular resolution  of the data (~1 parsec) and the spectral index analysis enabled the  identification of the underlying physical mechanism behind this  variability as coronal synchrotron radiation. The estimated magnetic  field strength is about 66-465 Gauss, which is thousands to millions of  times greater than the typical magnetic field strength in star-forming  regions of our Galaxy. We discuss how this variability provides the key  physical parameters of AGN, and how ngVLA will allow a systematic search  of this variability for a more representative sample of AGNs.

Víctor Manuel Patiño Álvarez

Blazar Multiwavelength Variability and the VLBI Connection

Instituto Nacional de Astrofísica, Óptica y Electrónica (INAOE)

I present some of the results obtained during the last few years by myself and the INAOE AGN Group / Max Planck Partner Group, including the work of the Master and PhD students. Regarding the multiwavelength variability studies. We find that sources like 3C 279 and 3C 454.3 have activity periods in which the gamma-rays can be dominated by either synchrotron self-Compton (which was previously though not possible for this type of blazars), or external inverse Compton. In the sources 3C 279, 3C 454.3, CTA 102, and B2 1633+382 we discovered the location of at least one gamma-ray emission region within the jet, at 42 pc, 9 pc, 25 pc and 41 pc, respectively, from the central engine. For 3C 279 and 3C 454.3 we find evidence of there being multiple gamma-ray emission regions, and in the case of the former, we can even pinpoint one of them to a moving VLBI component. We also found evidence of the existence of broad line emitting material that is being ionized by the jet in the sources 3C 454.3 and CTA 102; this has important implications on the calculation of black hole masses. Also, preliminary results from our research show that over half of the blazar population presents this additional broad line region.

Eva M Palafox

Dissecting Blazar Gamma-Ray Emission: Multi-Zone Production in 3C 454.3

INAOE 

We investigate the connection between radio variability in the jet of  blazar 3C 454.3 and its gamma-ray emission. We utilize 12 years of  gamma-ray data and multi-epoch Very Long Baseline Array (VLBA)  observations at 15 and 43 GHz, we aim to identify specific jet  components linked to the blazar gamma-ray activity. Our findings reveal a significant correlation between gamma-ray flux and  core emissions at both 43 GHz and 15 GHz, suggesting these central  regions contribute substantially to the overall gamma-ray production,  with contributions of 37% and 30%, respectively. Additionally, a  quasi-stationary feature emitting at 43 GHz, located at a projected  distance of 4.6 pc downstream the core, and a mobile 43 GHz component  that travels from 0.8 to 2.3 pc projected distance from the core, with  an apparent speed of βapp = 9.9 ± 1.1c, both exhibit strong correlations  with gamma-ray variations. These regions are estimated to contribute  18% and 26% to the high-energy emission, respectively. The observed simultaneous variability across these spatially distinct  emission regions within the jet strongly supports Synchrotron  Self-Compton (SSC) as the primary mechanism responsible for gamma-ray  production in these emission regions in 3C 454.3. The presence of  multiple, potentially non-stationary gamma-ray emitting zones challenges  existing theoretical models. This discovery offers crucial insights for  a more comprehensive understanding of blazar complexity and gamma-ray  emission processes.

Ryota Ikeda

Formation Of Sub-Structure In Luminous Sub-millimeter galaxies (FOSSILS)

NAOJ/SOKENDAI 

The brightest sub-millimeter galaxies (SMGs) are the most probable ancestors of the massive galaxies that dominate the central potential of clusters we see today. Mergers or large-scale gas inflow in isolated disks are possible scenarios explaining the observed large star formation rate, but the exact triggering mechanism is under debate, mainly due to insufficient high-resolution observational data to draw a general conclusion. We are conducting an ALMA survey to obtain a statistical sample (N>30) of unlensed luminous SMGs at 0.06"-resolution in 870um FIR continuum emission. Up to a total of 40 galaxy images taken at 300-400 pc resolution allows us to analyze the spatial distribution of the extended dust and star formation statistically for the first time. We present the preliminary results of morphological analysis and the results of the spatially-resolved SED modeling for some of the samples that are also observed by JWST. Finally, we present the promising science cases using both ngVLA and ALMA for our sample, where spatially resolved low-J CO lines become accessible even at z>4.

Chandana Hegde

Multi-wavelength Morphological Analysis of SMGs in the NEP Field: VLA and JWST Insights.

DAWN/DTU 

Submillimeter galaxies (SMGs), defined by their excess of sub-millimeter wavelengths, have high star-formation rates of 100-1000 M⊙/yr, contribute 30% to the cosmic star-formation rate density at Cosmic Noon (z ≈ 1 − 3), and are considered to be the progenitors of the most massive galaxies in the local Universe. However, the mechanism driving the high star-formation rates in these starburst galaxies remain poorly understood. Previous optical observations have been hindered by dust that obscures key star-forming regions. To better understand these dusty galaxies, our study employs a multi-wavelength approach, utilizing radio observations from the VLA and near-infrared data from JWST NIRCam. The VLA’s low-frequency emissions trace supernova explosions, marking sites of recent star-formation over ∼ 100 Myr timescales. In contrast, NIRCam provides insights into the underlying stellar morphologies. In this work, I will showcase our methodology and initial findings from the Northern Ecliptic Pole (NEP) field. Our analysis focuses on comparing the morphological features visible across radio and infrared wavelengths. By mapping the extended radio emissions alongside detailed, high-resolution NIRCam images, we aim to correlate the young star-forming regions with the more established, dusty structures that define the broader morphological framework of these galaxies.

Eric Koch

Galactic ecosystems in the nearby Universe with the ngVLA

Center for Astrophysics | Harvard & Smithsonian 

Galaxies form intricate ecosystems where the complex interplay of many  processes controls the matter cycle onto and within galaxies and the  star formation they contain, ultimately shaping the nearby galaxy  population. Because of this complex interplay and the vast spatial and  timescales on which these processes act, there remain many fundamental  questions that we lack strong observational constraints for, including  the accretion and transportation of gas in galaxies, the formation of  molecular clouds and subsequent build-up of density driving the star  formation process, and the dominant modes of feedback from this star  formation that reshapes the galactic environment. Nearby galaxies are  ideal laboratories for studying these processes over galactic  environments and spatial scales, spanning from detailed Milky Way  studies to large galaxy populations at higher redshifts. In this talk, I  will present on the current state-of-the-art within our Local Group and  nearby galaxy populations, drawing on recent results from the PHANGS  (phangs.org) and LGLBS (lglbs.org) collaborations, which long-standing  questions current surveys have sharpened yet leave unanswered, and how  the ngVLA promises to deliver breakthroughs for our understanding of  galactic ecosystems.

Alberto Bolatto

Embedded Massive Clusters in the z=0 Universe with the ngVLA

University of Maryland, College Park

Massive, very young clusters have been found to power starbursts in local galaxies (Tsai et al. 2009, Turner et al. 2017, Leroy et al. 2018, Emig et al. 2020). This may represent the main mode of star formation in starbursts, and a window into the formation of globular clusters (Portegies Zwart et al. 2010, Ginsburg & Kruijssen 2018). The formation, evolution, and survival of these dense, tightly bound clusters is poorly understood due to the limitations of the observations (Krumholz et al. 2019). With its sensitivity and resolution, the ngVLA is poised to revolutionize this field of study. Its sensitivity will allow us to measure the free-free radiation from young clusters with stellar masses larger than ~1000 solar masses within 60 Mpc, irrespective of extinction. And its resolution will allow us to isolate pc-size structures over the same distances. Moreover, access to radio-recombination lines such as H40-alpha provides a direct measurement of the kinematics of the ionized gas phase, as its temperature and metallicity (Emig et al. 2020, Mills et al. 2021). Local individual molecular outflows, detectable as P-Cygni profiles in molecular transitions, reveal the local feedback terminating cluster formation (Lervy et al. 2021), something that the ngVLA will be able to get powerful statistics on. 

Nicholas Ferraro

The Massive Embedded Star Cluster Atlas: 22 GHz Imaging of Young Super Star Cluster Candidates in Lo

University of California Los Angeles 

We present results from the Massive Embedded Star Cluster Atlas  (MESCAL), including the Local Wolf-Rayet Galaxy Survey (LWRGS), a 22 GHz  survey of 30 local galaxies (D ≲ 20 Mpc) showing spectral features of  Wolf-Rayet (WR) stars using the Karl G. Jansky Very Large Array (VLA),  from Ferraro et al. 2024 (in review). WR features are an indicator of  very massive (M ≳ 25 M_☉) stars, which we suspected are associated with  young (~3-4 Myr) super star clusters (SSCs). We present a census of 89  individually-identified regions of likely free-free emission in 26  galaxies, associated with potential young SSCs. The free-free fluxes  from these maps allow extinction-free estimates of their Lyman continuum  rates (N_Lyc), masses and luminosities of the emission regions. Of  these regions, 55 can be classified as potential HII regions associated  with young SSCs with NLyc ≳ 10^52 s^-1, and 25 of these regions are  likely massive enough (M ≳ 5 ✕ 105 M☉) to test specific theories on star  formation and feedback inhibition in SSCs. The resulting catalog  provides sources for molecular line and infrared studies of super star  cluster formation well-suited for contemporary telescopes such as JWST.  We also present ongoing results from in-depth examinations of individual  galaxies within the sample. Finally, we discuss future possibilities  for research into SSC formation that will be enabled by the ngVLA’s  superior sensitivity and angular resolution.

Flash Posters Tuesday

1. Vilchis, Omar Unveiling the Magneto-Ionic Structures of the Radio Relic of MACS0717+3745
2. Ramirez Lopez, Andrea Polarization and Depolarization Analysis in Giant Radio Galaxy Jets Using ATCA Observations
3. Aguilar, Emmaly SPIRE dropouts: a missing high-z DSFG population
4. Pandey, Rakesh Testing Bloated star hypothesis in IRAS 19520+2759
5. Zazueta, Yesenia Exploring the expected precision of astrometric and orbital parameters for the ngVLA with MC
6. Cordiner, Martin Atmospheric Dynamics in the Solar System
7. Gomez Miller, Brissa PKS 1335-127 EHT Observations for multi-wavelength analysis
8. Ramirez-Arellano, Johanan YSOs evolution seen through their centimeter continuum emission: Corona Australis
9. Momose, Munetake Revealing asymmetry on midplane of protoplanetary disk through modelling of axisymmetric emission: methodology
10. Cuazosón, Jetzael Progress on designing a K-band radiometer for atmospheric site testing at potential ngVLA stations.
11. Guerrero Gamboa, Rubén The Role of Magnetic Fields in Turbulence Ampification and Gravitational Collapse
12. Bruzewski, Seth Parallax, Proper Motion, and Prospects for J0002+6216
13. Burridge, Roman ngVLA contribution towards a VLBI Mission to Resolve Black Hole Shadow of NGC 4258 and other Maser Objects
14. Lazio, Joseph The Transition to the next-generation Very Large Array

Chenoa Tremblay

The Cosmic Dance of Andromeda & The Milky Way

SETI Institute 

The milky way is part of a local group of galaxies where M31 or the Andromeda galaxy, Andromeda's satellite galaxy M33, and the Milky Way make up the bulk of the dynamical forces in the group. To solve for one of the biggest unknowns regarding M31 - its transverse motion with respect to the Milky Way- we rely on the angular resolving power of long baseline interferometry. By deriving this value we can accomplish a number of goals which will impact the expected future of the Milky Way and goes a long way in understanding its past. By knowing the transverse motion we can test different gravitational models for the Local Group and compare this with our understanding of galaxy formations. Currently, our observations suggest that either the Local Group is unique or we have a gap in our knowledge of how galaxy formation works. This could give insight into whether the Milky Way and M31 have brushed in the past and whether they will collide in the future. If so, on what time scales exactly. I will talk about our search for methanol masers as point sources throughout M31 to track its transverse motion, search for point-like methanol masers throughout and track and disentangle its transverse motion from M31s galactic rotation. I will also discuss how long-baselines ngVLA provide the necessary resolution to track this motion with remarkable precision.

David Wilner

The Formation of the O-type Stars: New Views of the W49A Hypercompact HII Regions

Center for Astrophysics | Harvard & Smithsonian 

O-type stars represent a tiny fraction of star formation outcomes by  number,  but their feedback is a key driver of the evolution of the  interstellar medium. A distinguishing feature of these high-mass stars  is production of Lyman continuum photons that ionize their natal  environments. Detailed numerical simulations of O-type stars in  formation implicate accretion through circumstellar disks, with polar  outflows to overcome radiation pressure. Because these sources are  intrinsically rare and typically far away, observational constraints are  sparse at scales relevant to confront these predictions. We present  centimeter and subcentimeter continuum and recombination line  observations of the remarkable population of hypercompact HII regions in  the W49A region from the VLA and ALMA. These observations, with beam  sizes as small as 35 mas (400 au), start to resolve the ionized gas  morphologies and kinematics of these sources and offer intriguing  evidence for ionized disks and outflows, as well as time variability  associated with unsteady accretion. We discuss how the ngVLA, with high  fidelity imaging at more than 10x higher resolution, will provide a new  window into the early evolution of the most massive stars, constraining  models of how they build up mass and impact their environments.

Álvaro Sánchez-Monge

Understanding the mix of thermal and non-thermal emission in HII regions

ICE-CSIC, Barcelona 

The giant molecular cloud Sagittarius B2 (hereafter SgrB2) is the most massive region with ongoing high-mass star formation in the Galaxy. In the southern region of the 20-pc large envelope of SgrB2, we encounter the SgrB2(DS) region which hosts more than 60 high-mass proto-stellar cores distributed in an arc shape around an extended HII region. We use the Very Large Array in its CnB and D configurations, and in the frequency bands C (4-8 GHz) and X (8-12 GHz) to observe the whole SgrB2 complex. Continuum and radio recombination line maps are obtained. We detect radio continuum emission in SgrB2(DS) in a bubble-shaped structure. Using data from 4 to 12 GHz, we derive a spectral index between -1.2 and -0.4, indicating the presence of non-thermal emission. The radio recombination lines in the region are found to be not in local thermodynamic equilibrium (LTE) but stimulated by the non-thermal emission. The thermal free-free emission is likely tracing the HII region ionized by an O7 star, while the non-thermal emission can be generated by the relativistic electrons created through first-order Fermi acceleration. Is SgrB2(DS) a peculiar case, or are there other similar HII regions in the Galaxy? Future observations with the ngVLA could reveal new insights into the properties of HII regions, and their interaction with the surrounding medium.

Discussion & Kids Outreach

Outreach with Luis Rodríguez

Luis Rodríguez, Instituto de Radioastronomía y Astrofísica (IRyA-UNAM)

November 13, 2024

Rachel Osten

TBD

STScI 

Behzad Bojnordi Arbab

Unveiling the structure of evolved stars’ extended atmospheres: Opportunities with ngVLA

Chalmers University of Technology 

The heavy mass-loss experienced by evolved asymptotic giant branch (AGB)  stars provides metals and dust to the interstellar medium (ISM). In our  current understanding, mass loss occurs through dust-driven winds  originating from the extended atmospheres of these stars.  State-of-the-art simulations show that large convective cells play an  important role. Still, recent observations at milliarcsecond resolution  with ALMA have shown that the conditions in the extended atmospheres  might be different than predicted by the models.  Low-frequency observations of evolved stars with the Square Kilometer  Array (SKA) and the next-generation Very Large Array (ngVLA) will make  it possible to study the critical outer regions of the extended  atmospheres where dust forms and is accelerated in a novel way. With the  high resolution and sensitivity of ngVLA, we can use the continuum  emission to constrain atmospheric density and temperature structures of  stars at larger distances.  I present our recent results on the observed  structures of the extended atmospheres of AGB stars at the limits of  the current instruments, demonstrating the intricate dynamics at play in  the layers leading to the dust-formation region. Furthermore, I show  the level of detail expected in the observation of AGB stars with the  ngVLA and present the upcoming leap in the resolved observation of the  extended atmospheres in frequencies not currently available and  distances not reachable.  Furthermore, simultaneous observations of SKA, ngVLA, and ALMA will  produce wide-range multi-wavelength data for various radii of the  extended atmosphere, enabling us to test and constrain theoretical  models in a previously impossible way. With the large field of view of  ngVLA and SKA, we can study the temporal evolution of evolved star  atmospheres and dust-forming regions. In this presentation, I will  discuss these opportunities for ngVLA to revolutionize detailed  observations in this field.

Sergio Dzib

Advancing YSO Studies with VLA and VLBA: Insights and Future Prospects with ngVLA

Max Planck Institut für Radioastronomie 

The recent sensitivity upgrades of the NRAO Very Large Array (VLA) and the Very Long Baseline Array (VLBA) have significantly advanced our understanding of stellar centimeter radio emission, particularly in young stellar objects (YSOs), setting the stage for groundbreaking science with the next-generation Very Large Array (ngVLA). This presentation will first provide a brief overview of the results obtained from VLA and VLBA observations by our team. Then, it will present our current projects. First, the Orion Radio All-Stars project, which targets the star-forming Orion Nebula Cluster (ONC). Our VLBA campaign has discovered over 100 magnetically active YSOs with nonthermal radio emitters with brightness temperatures exceeding 10**6 K --the largest population identified to date. I will discuss the astrometric and photometric properties of these stars, initial constraints on YSO radio flares and their correlation with X-ray flares, and the resulting high-energy irradiation of their surroundings. Second, the Dynamical Masses of Young Stellar Multiple Systems with the VLBA (DYNAMO-VLBA) aims to determine the dynamical masses of about two dozen systems. The first results of DYNAMO-VLBA will be presented, and they indicate a discrepancy between the mass determined from dynamical methods and those expected from evolutionary models. Finally, I will explore the use of the VLBA for precision stellar astrometry in the Gaia era, discuss the importance of Gaia-VLBI stellar astrometry comparisons, and present recent results of a VLBA survey of nearby (<100 pc) young stars in the Gaia DR3 catalog which could be used to constrain systematic errors from Gaia. This comprehensive approach underscores the transformative potential of high angular resolution observations in unveiling the dynamic and energetic processes in young stars, paving the way for future discoveries with the ngVLA and beyond.

Gemma Busquet

The VLA Orion A Large Survey

Universitat de Barcelona, España 

The early stages of star and planet formation involve a balance between  accretion and ejection of material during the gravitational collapse.  This balance and the consequent protostellar evolution are crucial in  determining the final properties of stars and their planetary systems.  Orion A is the nearest star-forming complex containing a broad range of  environments populated by protostars and Young Stellar Objects with  different masses and evolutionary stages, representing a tested for star  formation theories.  The VLA Orion A Large Survey (VOLS) is an international effort to image  the Orion A complex in the C (~6 cm) and Ku (~2 cm) radio continuum  bands, as well as in a selected number of spectral lines. VOLS  represents the first radio survey to cover a large area of Orion A at  subarcsecond resolution.  In this work, we present the results obtained at 6 cm during 26 epochs  of observations. We will present the physical properties of the stellar  population in Orion A, including the variability of the radio continuum  and CH3OH maser emission in the Orion Nebula Cluster.

Elena Díaz-Márquez

Characterizing the stellar population in the infrared dark cloud G14.225-0.506

Institute of Space Sciences (ICE-CSIC) 

Radio continuum emission at centimeter wavelengths is associated with  young stellar objects (YSOs) throughout all stages of star formation,  from Class 0 to Class III. Previous studies in massive star-forming  regions and infrared dark clouds (IRDCs) were limited by sensitivity,  missing the low-mass stellar populatio. However, with the sensitivity of  the Very Large Array (VLA), it is possible to study more distant  regions, gaining insights into massive star and star cluster formation  and their effects on the surrounding medium.  We present deep radio continuum observations (~1.5–3 μJy) at 6 and 3.6  cm towards the IRDC G14.225-0506 using the VLA in its most extended  configuration (~0.3′′) to characterize its stellar population and study  the evolutionary sequence across the cloud.  We detected 66 sources, ten of which are variables. The thermal emission  is consistent with radio jets, while nonthermal emission in less  evolved objects, primarily in the northern region, suggests more massive  YSOs and a more advanced evolutionary stage. Our findings align with  the “filament-halo” gradient in age and mass and confirm an evolutionary  sequence from the southwest to northeast of IRDC G14.225-0506, ending  with the most evolved region M17.  Future radio interferometers like the Next Generation Very Large Array  (ngVLA) will greatly enhance the study of young stellar clusters. These  advanced telescopes will achieve current sensitivity levels in just one  hour, allowing for extensive Milky Way surveys. This will enable  detailed studies of radio emission variability and coronal-type magnetic  activity when combined with X-ray observations.

Melodie Kao

TBD

Lowell 

In the mass sequence spanning very low mass stars through brown dwarfs, also known as ultracool dwarfs, magnetic activity appears to undergo a transition from stellar-like flaring activity to planet-like phenomena, including aurorae and radiation belts. These overlapping magnetic activity regimes position ultracool dwarfs as unique, powerful, and accessible laboratories that probe star-planet interaction and exoplanet magnetospheric physics. The advent of JWST will yield new insights into auroral physics, while maturing low frequency radio arrays and a highly anticipated ngVLA will provide new means for detecting and characterizing substellar magnetospheres. I will synthesize the state of the art for star-planet interaction and ultracool dwarf magnetospheric studies; discuss implications for exoplanet magnetism and star-planet interactions; and highlight opportunities for the next generation of ground- and space-based radio facilities.

Gisela Ortiz-León

Astrometric companions with the ngVLA: low-mass stars, brown-dwarfs and planets

Instituto Nacional de Astrofisica, Optica y Electronica 

The longest baselines of the ngVLA will allow 1-μas astrometric  accuracy, which represents an increase by a factor of 10 with respect to  that of current instruments (e.g. VLBA and Gaia). It is expected that  this unprecedented astrometric accuracy could open new, previously  inaccessible lines of research, for instance, the astrometric detection  of very low-mass unseen companions (Super-Earths and Sub-Neptunes)  around nearby (~10 pc) M-dwarfs.   To investigate the expected performance of the ngVLA on the  characterization of astrometric companions, we are performing Monte  Carlo simulations, where the precision of astrometric and orbital  parameters is investigated by fitting stellar positions from simulated  ngVLA observations. The characterization of compact binaries (< 1 au)  and of sub-stellar companions will certainly benefit from the improved  capabilities brought by the longest baselines on the ngVLA. However, it  is still unclear how many companions (in particular planetary  companions) can be discovered and our work could help to determine the  expected number of astrometric planetary detections, as well as the  precision on parameter determination that will be achieved with  multi-epoch ngVLA observations.

Salvador Curiel

Radio astrometric search for planetary companions associated with low-mass stars

Instituto de Astronomía, UNAM 

More than 5,600 exoplanets have been found and confirmed using mainly radial velocity and transit techniques. Other techniques, such as direct imaging, have also given good results, but to a lesser extent. Although astrometry was the first technique to be used in the search for exoplanets, until recently it had not given good results. The Gaia satellite is expected to change this. It is expected that, in the coming years, several thousand exoplanets will be found with Gaia observations. It is also possible to search for exoplanets with precise radio observations using Very Long Baseline Interferometry. During the past several years, we have search for sub-stellar companions associated with TTauri stars and close by stars, using astrometric observations with the VLBA. In recent years we have found some exoplanets using this radio astrometry technique. In this talk, I will present the most recent results of this long-term project. In particular, I will show that it is possible to find exoplanets using the new radio astrometry technique, and that future telescopes, such as ngVLA and SKA, will have the angular resolution, sensitivity, and performance necessary to search for and detect a wide variety of planetary companions, including, possibly, even super-earth planets.

Kei Tanaka

The Hot and Dynamic Birth of Massive Stars from the ngVLA Perspective

Tokyo Institute of Technology 

The Next Generation Very Large Array (ngVLA) has exceptional capabilities to unveil various dynamical and chemical processes in massive star formation at the unexplored innermost disk scale of less than 100 au. Recent observations from ALMA/VLA and theoretical studies suggest that observing these innermost disks could open up qualitatively novel avenues for star formation research, as temperatures exceed several hundred K and dynamical timescales are shorter than 100 years. In massive protostellar disks, dust grains are expected to be destroyed or sublimated due to the intense conditions of temperature, shocks, and radiation, which are far more extreme than those in the envelopes typically observed as “hot cores.” The high sensitivity and resolution of the ngVLA will enable the detection of gaseous refractories in these “hot disks,” such as NaCl and AlO, which trace disk kinematics and provide new insights into the metallic elements in star-forming regions, i.e., astromineralogy. A multi-epoch survey by the ngVLA will offer demographics of forming massive multiples with separations of less than 10 au through their proper motion. By combining observations of refractory molecular lines and hydrogen recombination lines, we can reconstruct the three-dimensional orbital motions of massive proto-binaries. Moreover, the 1-mas resolution of the ngVLA could potentially capture the first-ever image of the photospheric surface of an accreting protostar if it is bloated to the au scale by high accretion rates of mass and thermal energy.

Jesús Miguel Jáquez-Domínguez

ngVLA Synthetic Observations of Ionized Gas in Massive Protostars

IRyA-UNAM 

During the formation of massive stars, the innermost parts closer to the central object can present significant ionization in the form of gravitationally trapped \textsc{H ii} regions, jets, and ionized disks or winds. A complete theoretical scenario for the early evolution of ionization feedback in massive star formation is still in the making but resolved observations of the continuum emission and kinematical structure of this type of object will be very important to guide theory. With the resolution and sensitivity that the ngVLA will offer, a new window will be opened to study massive star formation at angular resolutions of $\sim 1$ mas, or a few astronomical units at kiloparsec distances. This work presents synthetic ngVLA observations of the free-free continuum and recombination line emission from ionized jets and disks around massive protostars. Using the \texttt{sf3dmodels} python package, we create geometrical distributions of the gas following analytical prescriptions, which are then passed through the \texttt{RADMC-3D} radiative transfer code. Finally, we create synthetic images under simplifying assumptions, and also with the full ngVLA instrument response using the \texttt{CASA} tools. Exploiting these synthetic images, we will quantify the capabilities of the ngVLA to observe and resolve these massive stars in formation.

Bryan Butler

Observations of Icy Bodies in the Solar System with ngVLA

NRAO 

The next generation Very Large Array (ngVLA) will provide the next steps forward for high sensitivity, high resolution observations of solar system bodies at long wavelengths. Here we will focus on observations of bodies with icy surfaces in the solar system. The icy bodies in the solar system are of various types (giant planet satellites, dwarf planets, centaurs, Trans-Neptunian Objects (TNOs), comets, etc.). All of these kinds of objects are sure to be observed with ngVLA, but we will further focus on giant planet satellites, dwarf planets (specifically Pluto), and TNOs. While the VLA has made important observations of these icy bodies, it is really ALMA that has demonstrated the power of long wavelength observations in providing unique information about them. From TNOs to Pluto to the Galilean satellites, ALMA has provided fantastic images of these bodies and their satellites. An especially important body for research has been Titan, where ALMA wavelengths (prior to Band 1) do not probe to the surface, but the rich spectrum of molecular species in its atmosphere have yielded important results on abundances, temperature, chemistry, and winds and their spatial and time variability. Results from ngVLA will be similarly revolutionary, but at longer wavelengths. With ~few K sensitivity at linear resolutions as good as ~15 km for the Galilean satellites, ~100 km for Pluto and Charon, and even being able to resolve Eris (~350 km resolution at 95 AU distance), surface features of those sizes and larger on these bodies will be able to have information on their depth and composition constrained with such observations. We will discuss the specific importance of observations of these icy bodies with ngVLA, and present some simulations based on current state-of-the-art thermal models.

Yoko Oya

Revealing Physics and Chemistry in Disk/Planetary-System Forming Regions of Protostellar Sources wit

Kyoto University 

To understand the origin of the Solar system, the physical/chemical evolution along the star/planet formation is a key issue. Extensive observational studies have recently revealed that both the physical structure and the chemical composition drastically change during the disk formation around protostars. Furthermore, it has been found that molecular distributions are sensitive to changes in the physical conditions. Some kinds of molecular lines are therefore prospected to ward as ‘molecular markers’ to selectively highlight particular structures of disk forming regions. Conversely, detailed physical characterization is essential for elucidating the chemical evolution occurring there. It has recently been recognized that some molecular lines tend to trace the mid-plane of a disk/envelope system and others trace its surface. The traced kinematic structure may differ among these molecular emissions, and thus, their careful analyses are essential for further observational studies in disk forming regions. Machine learnings may help us to disentangle the observed structures. Specifically, sulfur-bearing species have empirically been good tracers for disk/envelope/outflow structures in young low-mass protostellar sources. Their emissions at mm wavelength are useful to characterize the angular momentum of the gas, which is the essential topic to understand the structure formation. Such a chemical diagnostics at cm wavelength is thus worth establishing to investigate the structures at the scale for planetary formation and outflow launching point; moreover, it can be realized with various large/complex organic molecules. ngVLA is an ideal equipment for this purpose, which will progress our understandings for structure formation and material evolution simultaneously by supporting each other.

November 14, 2024

Marta De Simone

The origin of chemical complexity from cm to mm wavelengths: in the earth of young forming planetary

ESO-Garching 

The earliest phases of planetary system formation are marked by a fascinating and intricate chemistry, with a high abundance of prebiotic molecules detected in protostellar environments. This chemical complexity serves as a crucial diagnostic tool to understand the underlying physical processes shaping these nascent systems, and to probe the chemical evolution from prestellar core to more evolved disks. Indeed, part of the chemical processing happening during the prestellar and protostellar phase may affect later stages of evolution. For example, the observed diversity in the large variety of exoplanets detected so far, can be the result of a diversity already present at the early stages of their formation. One of the striking results of the past years is the chemical diversity revealed in Sun-like protostars. Indeed, from a chemical point of view protostars differs from each other: some of them show millimetric molecular spectra rich in interstellar organic complex molecules (the so called hot corinos), and some others are enriched of unsaturated small carbon chains (the so called WCCC sources). The origin of this diversity is still unclear, as well as its impact on the chemical composition of future forming planets. In this talk, I will review the observational efforts carried out in the past years to chemically characterize the inner regions of Solar-system analogs. I will summarize the current understanding of the molecular complexity from large prestellar cores to compact protoplanetary disks, with emphasis on the origin of the molecular differentiation observed in protostars. Finally, I will stress the relevant role of high angular resolution cm-to-mm wavelength observations, particularly with the forthcoming ngVLA, to investigate the chemical complexity and nature of planet forming regions.

Timea Csengeri

ALMA-IMF and NASCENT-stars large programs: hunting down emerging molecular complexity

Laboratoire d'astrophysique de Bordeaux 

The formation conditions of high-mass stars and clusters is still a poorly understood process. The physical evolution of the collapsing gas is governed by an interplay of various physical processes, while simultaneously, a characteristic chemical complexification of the star-forming gas also takes place. Using the unparalleled sensitivity and imaging capabilities of ALMA, the ALMA-IMF large program performs a comprehensive study of the physical and chemical conditions down to the scale of individual star-forming cores by imaging 15 of the most prominent Galactic protoclusters including young, intermediate and evolved stages of star formation. We systematically identified an extremely rich population of star-forming cores embedded within these well-characterized protoclusters, providing firm statistical grounds to study the core mass function and its variation in these environments. I will present a synthetic overview of key ALMA-IMF findings, covering the properties of the core population and the emergence of chemically rich regions. ALMA-IMF also provides insight into the statistics of the molecular composition of chemically rich cores, and our findings suggest that the most massive cores are all associated with methyl formate emission, demonstrating that all massive cores undergo a chemically active phase. We identified a sample of hot core candidates, many of which exhibit emission in a variety of COMs underlying the complex chemistry associated with sites where hot cores emerge. Furthermore, I will also introduce the recently started NASCENT-stars large program, which offers a more complete view on the molecular composition of the star-forming gas using the NOEMA interferometer. I will put in context these results with our understanding of the global molecular diversity of emerging hot cores, and highlight how our current projects can prepare us for ngVLA.

Andrés Izquierdo

Kinematic structures in planet-forming discs: Results from the ALMA large program exoALMA

University of Florida 

Interferometric observations have allowed us to resolve a wealth of gas and dust substructures in the outer regions of large protoplanetary discs. This has opened a unique window to investigate the physical and chemical environment in which giant planets form and, more specifically, has enabled detailed modelling of the impact of planet-disc interactions on the evolution of the host disc. I will present results from the large program exoALMA, a planet-hunting campaign aimed at unveiling the dynamical structure of 15 planet-forming discs in unprecedented detail with ALMA. I will discuss the connection between outer and inner disc dynamics and the missing pieces of the planet formation puzzle that the upcoming ngVLA will help us unlock.

Paul Ho

Carlos Carrasco-González

Dust and polarization in protoplanetary disks at high resolution

IRyA-UNAM 

Elena Viscardi

Characterizing the building blocks of planets with unprecedent resolution with the ngVLA

European Southern Observatory 

The dust content of protoplanetary discs plays a crucial role in our theories on planet formation. The dust mass represents the budget available to form rocky planets and cores of giant planets. The dust particle size distribution offers insights into the preferred locations for planetesimal formation: the “dust traps”, gas pressure maxima where grains pile up. ALMA has enabled us to partially resolve these substructures. To probe their properties, particularly the dust surface density and particle size distribution, continuum observations at various (sub-)mm wavelengths are needed. However, recent ALMA observations have shown that these regions are largely optically thick at wavelengths shorter than 3 mm, highlighting the need for high resolution observations at longer wavelengths. Currently, long-wavelength observations of discs have limited resolution (0.1” for ALMA at 7mm, 0.06” for VLA at 9mm), preventing us from resolving most substructures. Achieving good sensitivity and resolution requires long observing times (>50 h), making this dust characterization technique feasible only for a small sample of bright discs. In my talk, I will demonstrate how critical observations at wavelengths >7 mm are. With the help of simulated observations, I will show how beam smearing from the current resolution of both ALMA and VLA impacts our determination of the dust content of disc substructures. As a science demonstration case, I will then present new high-resolution (0.07”) high-sentitivity 9mm VLA observations of GM Aurigae (from the V-SHARDS large program) and discuss how they improve our constraints of the dust properties in this very famous disc. Lastly, I will illustrate how the high-quality, milliarcsecond-resolution observations from the ngVLA will transform our ability to characterize the dust content of disc substructures in the finest details.

Takahiro Ueda

Multi-wavelength characterization of protoplanetary dust with ngVLA

Harvard-Smithsonian Center for Astrophysics 

Characterizing dust in protoplanetary disks through observations is crucial for understanding the initial steps of planet formation. Dust properties, such as size and mass density, in disks have been evaluated by analyzing the spectral behavior of dust thermal emission at (sub-)millimeter to centimeter wavelengths (e.g., Beckwith et al. 1990). However, dust thermal emission depends not only on dust size and mass density but also on dust composition and aggregate structure, making it challenging to deduce actual dust properties from a limited number of observations (e.g., Guidi et al. 2022). We develop a Markov Chain Monte Carlo (MCMC) method to deduce dust properties from the spectral behavior of dust thermal emission and examine its accuracy by applying it to multi-wavelength mock images generated with dust evolution models. The MCMC analysis correctly reproduces the input dust size and mass density as long as the observing wavelength sufficiently covers the optically thin to thick regimes and parameters other than size and mass density are given. The lack of observing wavelengths at which the disk is optically thin induces large uncertainty in the derived dust properties. The fact that the dust composition and internal structure are unknown beforehand also introduces orders of magnitude of uncertainty to the dust size and mass density. We show that observational data at (sub-)centimeter wavelengths with sufficient angular resolution improve these uncertainties and provide us with more robust predictions for the dust size and mass density as well as the dust composition and internal structure. The ngVLA, along with ALMA, will be key to unveiling the dynamical and chemical evolution of solid materials in protoplanetary disks.

Anibal Sierra

Why do we need ngVLA to understand protoplanetary disks?

University College London 

It is well known that planet formation takes place in protoplanetary disks, where planets form from the raw dust material within these objects. However, the total amount of dust in protoplanetary disks remains unknown because current observations with ALMA can only constrain the lower limits due to their optical thickness. The ngVLA represents a unique opportunity to accurately estimate dust disk masses and resolve the distribution of solids in protoplanetary disks at long radio wavelengths, where disks have been poorly studied. In this talk, I will review the radiative processes occurring in protoplanetary disks at millimeter wavelengths and discuss how the capabilities of the ngVLA will help us finally understand the total raw dust material capable of forming planets in these disks. The results could potentially help to alleviate the mass discrepancy between the dust mass in Class II disks and the mass of most exoplanets detected around known planetary systems.

Brenda Matthews

Resolving the Birth of Debris Disks

Herzberg Astronomy & Astrophysics, National Research Council of Canada 

ALMA has revealed a dichotomy in the protoplanetary disk population, with 20% of disks exhibiting significant ringed substructures to large radii and the remaining 80% of disks being relatively faint and compact. The substructure present suggests that planet formation may be well underway by the Class II phase, prompting exploration of the younger disk stages. This dichotomy has been noted to have a parallel expression in debris disks, the collisionally-generated second generation disks around main sequence stars, detected around ~ 20% of main sequence stars. Connecting the dots between the protoplanetary and debris disk phases goes through the Class III disk phase, and the role of dust evolution, trapping and transport needs to be understood to understand this transition. Some studies have suggested that the ringed bright Class II disks are the precursors to the observed debris disk population, and so these objects should retain their substructure to later phases. The ngVLA will have several advantages over ALMA in the study of this transitional population, including sensitivity to gas associated with these disks, and the ability to take complete censes of most nearby star-forming regions. Understanding what the connection between these phases has to do with the diversity of planetary system outcomes is a key question that can be addressed by the ngVLA.

Osmar Guerra

ALMA reaches its limit in observations of ultra-compact protoplanetary disks: High-resolution observ

Leiden observatory 

In recent years, significant efforts have been dedicated to studying the demographics of protoplanetary disks using ALMA. This has enabled direct comparisons and statistical analyses of exoplanets alongside protoplanetary disks. Despite advancements in high-resolution studies, much progress remains to be made. While identifying substructures is important, accurately measuring and constraining disk sizes is crucial for understanding planet formation, dust evolution, and exoplanet demographics. In this talk, we will discuss high-resolution observations (~20-50 milliarcseconds) of previously unresolved disks in Lupus. We determined that most disks in the Lupus sample are compact (<30 au). These compact disks constitute more than 65% of the sampled disks in this region and seem to be very optically thick due to their small sizes. This raises questions about whether they are genuinely dominated by radial drift or if something might be obstructing this process. Understanding this could reveal the true dust masses in these disks and, more importantly, provide answers about Super-Earth and giant planet formation. However, investigating the impact of dust evolution (e.g., radial drift) requires higher-resolution and higher-sensitivity observations than ALMA can provide. Longer wavelengths are necessary to observe through the dense disks (cm regime), where ALMA Band 1 cannot achieve the same high resolution as it does in Band 6, complicating the study of the dust emission. Moreover, ALMA's sensitivity limits result in high integration times, making it unfeasible to study the demographics of disks. This highlights the necessity for a new telescope. The Next Generation Very Large Array (ngVLA), with approximately 10 times better sensitivity and baselines around 60 times longer than ALMA, will enable the study of very small disks (~1 au) with a higher SNR (>5) without requiring excessive telescope time, increasing our understanding of planet formation in the galaxy.

Alessia A. Rota

A correlation between accretion rate and free-free emission in protoplanetary disks

Leiden Observatory 

The inner regions of protoplanetary disks are the primary locations of planet formation and the processes that influence the global evolution of the disk, such as magnetohydrodynamic winds and photoevaporation. Transition disks with large dust cavities are ideal targets to study such regions as the central emission can be fully disentangled from the outer disk emission. We used spatially resolved, multi-wavelength ALMA observations of the millimeter continuum emission in combination with literature centimeter data to derive the spectral indices of the inner and outer disks in a sample of transition disks. Surprisingly, we found that, in most of the disks, the central emission close to the star is dominated by free-free emission, possibly associated with an ionized jet or wind. Based on a physical jet model based on protostellar jets, the free-free emission can be converted into an ionized mass-loss rate. We observe a strong correlation between the ionized mass loss rate and the accretion rate, which suggests the outflow is strictly connected with the stellar accretion and that accretion in these disks is mainly driven by a jet. Preliminary results of a study of multi-wavelength data with ALMA, VLA, and ATCA of a larger sample of regular protoplanetary disks without inner cavities show a similar trend, indicating that this is a general phenomenon that is not limited to transition disks only.

Ryan Boyden

The first detection of radio recombination lines in externally ionized protoplanetary disks

University of Virginia 

Radio recombination lines are powerful tools for studying ionized gas in galaxies, HII regions, and protostars. In this talk, I will present new ALMA observations that, for the first time, have detected hydrogen and helium radio recombination lines in a protoplanetary disk. We have imaged the Orion Nebula Cluster (ONC) at Band 3 with the combination of sensitivity and angular resolution needed to search for radio recombination line emission from the region’s protoplanetary disks. We detect hydrogen n = 41 to n = 40 (H41a) radio recombination line emission towards 16 externally ionized protoplanetary disks (i.e., “proplyds”) in the ONC. The detections are spatially coincident with the locations of the HST-identified proplyd ionization fronts, suggesting that proplyd H41a emission is produced by photoionizing radiation from the ONC’s massive OB stars. We measure the line fluxes and line widths of the H41a emission by fitting Gaussian line profiles to the observed spectra. The derived line widths are ~40-50 km/s across the sample, indicating that bulk gas motions are dominating the broadening of the H41a line. The line-to-continuum ratios are similar for each detected proplyd, suggesting that proplyds have similar ionized gas temperatures over a range of disk and stellar properties. Finally, we detect helium n = 41 to n = 40 (He41a) radio recombination line emission in one protoplanetary disk and place the first constraints on the global helium abundance in a protoplanetary disk. Our study demonstrates that radio recombination lines are readily detectable in externally ionized protoplanetary disks and provide a new way to study planet formation in clustered (i.e., typical) star forming regions. Our study also demonstrates how ngVLA, with its improved sensitivity and angular resolution at long radio wavelengths, will be uniquely capable of detecting radio recombination line emission towards large samples of disks in nearby and more distant stellar clusters.

Nagayoshi Ohashi

Exploring the earliest stages of planet formation

ASIAA 

Although planets are believed to form in disks around young stellar objects (YSOs) during the process of star formation, the precise stage at which planets are formed remains uncertain. Recent studies suggest that planet formation may occur even when young stars are still embedded protostars. In order to investigate this possibility, we conducted the ALMA large program "Early Planet Formation in Embedded Disks (eDisk)" with the objective of observing embedded disks around 12 Class 0 and 7 Class I protostars in nearby (d < 200 pc) star-forming regions at a resolution of ~0.04" in 1.3 mm continuum emission. The observations revealed that, in sharp contrast to Class II disks, embedded disks around protostars have fewer distinctive substructures, such as gaps and rings, and are more flared in their vertical directions. This suggests that planet formation may rapidly proceed when protostars evolve into Class II sources. The eDisk program observed molecular lines, such as CO isotopologues, in addition to 1.3 mm continuum emission, allowing us to investigate various phenomena in star and planet formation. These include Keplerian rotation, infalling motions, streamers, and outflows. In particular, identifying Keplerian motions allows us to estimate the dynamical mass of the central protostar, which represents the most reliable method to estimate the masses of embedded protostars. In this presentation, I will summarize the principal findings of the eDisk program and then discuss the potential role of the ngVLA in investigating the earliest stages of planet formation.

Héctor Arce

Infall and dense gas kinematics during the early stages of star formation

Yale University 

Stars form in dense condensations inside molecular clouds, typically referred to as cores, about 0.1 pc in size. Protostellar systems acquire most of their mass via gravitational infall of core material into the circumstellar disk. Consequently, understanding the origin of stellar masses requires characterizing the infall process at various evolutionary stages. Recent millimeter interferometric observations have hinted at the presence of infall streamers (i.e., narrow, curved structures that show kinematics consistent with gravitational infall) around young protostars. Yet, the frequency of these infall streamers among protostars of different evolutionary stages is not well constrained. Moreover, the significance of these streamers to the mass-assembling process of young stars remains largely unknown. We recently conducted ALMA observations of a sample of protostars with the goal of studying the outflow-envelope interaction at different evolutionary stages. We detect candidate infall streamers in more than half the Class 0 sources in our sample, using N2D+(3-2) -- a line that probes cold, dense and deeply embedded regions. In this presentation, we show how this deuterated species can be used to study the gas intimately involved in the star formation process. The ngVLA will be able to conduct high-sensitivity observations of the ground-level rotational transitions of this important species, as well as other high density tracers (at frequencies between about 60 and 110 GHz) at scales of a few to tens of au. This will allow us to trace how cloud material flows from the outskirts to the central parts of pre-stellar and protostellar cores (and into the protostellar system), at different evolutionary stages --essential for understanding how protostars gather their mass.

Tao-Chung Ching

Determine Plane-of-sky Magnetic Field Direction via Molecular Line Polarization

NRAO

Spectral-line polarization observations of the Goldreich-Kylafis effect can trace interstellar magnetic fields with the velocity information that is not available for continuum polarization observations such as dust thermal emission or synchrotron emission. The linear polarization arising from the Goldreich-Kylafis effect reveals the magnetic field structure on the plane of sky, and the total emission of the molecular line reveals the amount of gas moving along the line of sight. The curl of the magnetic field strength inferred from molecular line polarization and the electronic current inferred from molecular line total emission thus satisfy Ampère's law in Maxwell's equations. Here we report the ALMA observations of the CO (2-1) Goldreich-Kylafis effect toward the outflows of the Class 0 source NGC1333 IRAS 4A. The CO polarization shows a helical magnetic field structure of the outflow which is different from the hourglass-like magnetic field structure of the dense core inferred from dust polarization. The curl of the magnetic field strength is linearly correlated with the current of the outflow with a unit-less slope at an order of magnitude about -11, in agreement with the multiplier of the unit-less ionization fraction at an order of magnitude about -8 times the unit-less ratio of the ion-neutral drift velocity with respect to the outflow velocity at an order of magnitude about -3. This linear correlation for the first time provides a method to determine the magnetic field direction of the outflow, revealing the magnetic field from local south pole to local north pole, more than the dust polarization or synchrotron polarization which can only provide the orientation of magnetic field. With the possible expansion of the ngVLA frequency coverage to the common tracers of Goldreich-Kylafis effect such as CO and CS lines, ngVLA offers a great potential to reveal the magnetic field structure of planetary systems at unprecedented angular resolution and sensitivity.

Flash Posters Tuesday

Final Discussion and Farewell