BEGIN:VCALENDAR VERSION:2.0 PRODID:-//CERN//INDICO//EN BEGIN:VEVENT SUMMARY:Modelling Variable Broad Absorption Line Quasar Outflows Using Sim BAL DTSTART;VALUE=DATE-TIME:20261028T182100Z DTEND;VALUE=DATE-TIME:20261028T182200Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3673@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Nicolas Frisella (Western University)\nActive galact ic nuclei (AGN) are supermassive black holes in the centers of massive gal axies with large inflows of gas and dust collisionally heating up and radi ating away energy. Quasars are a type of AGN that outshine their host gala xies by several magnitudes\, capable of releasing high velocity outflows ( or winds) of material due to the intense radiation being emitted. When the se outflows are directed along the observer's line of sight\, their ultrav iolet spectra will present with broad absorption lines (BALs). These types of objects are categorized as BAL quasars\, and these BALs in their spect ra have been observed to vary over time for select quasars. The origin of this variability is not yet fully understood\, though spectral fitting alg orithms such as SimBAL (Leighly et al.\, 2018) have proven successful in m odelling the physical properties of quasar winds using a forward-modelling and Markov Chain Monte Carlo approach. This software package fits synthet ic spectra to observed spectra for a given quasar\, producing detailed phy sical and kinematical descriptions of these outflows. The fits of these sp ectra constrain the values of parameters including the density integrated along the line of sight (column density)\, the ionization of the outflows (ionization parameter)\, and the obscuration of the quasar's radiation fro m intervening clouds (covering fraction). My quasar of choice for modellin g using SimBAL has three epochs of available data from the Sloan Digital S ky Survey\, each separated by six years. The earliest epoch has the widest and deepest absorption lines for Carbon IV\, Silicon IV\, and Lyman Alpha \, however for each later epoch the lines are becoming weaker and narrower . As of now\, the leading candidates for the source of the BAL variability appear to be the column density and the ionization parameter. The relativ e impacts of each parameter on the differing absorption structure are yet to be determined\, and that will be the next focus of my master's work.\n\ nhttps://nyx.physics.mcgill.ca/event/587/contributions/3673/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3673/ END:VEVENT BEGIN:VEVENT SUMMARY:Making Reconnection Cooler: Modelling bright emission around black holes DTSTART;VALUE=DATE-TIME:20261028T182000Z DTEND;VALUE=DATE-TIME:20261028T182100Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3702@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Alicia Savelli (University of Toronto)\nAccretion di sks around black holes\, such as those in active galactic nuclei and X-ray binaries\, are home to extreme plasma processes that produce bright emiss ion across the electromagnetic spectrum. One such process powering this e mission is thought to be magnetic reconnection\, the violent restructuring of the magnetic field topology in which magnetic field lines pinch apart and reconnect\, converting stored magnetic energy into kinetic energy of t he encompassing plasma. In particular\, magnetic reconnection may be resp onsible for high-energy X-ray emission from a hot “corona” near the ce ntral black hole. In this talk\, I will demonstrate how this emission is modelled computationally in relativistic magnetohydrodynamic simulations\, as a step towards unlocking the theory behind these fascinating astrophys ical environments.\n\nhttps://nyx.physics.mcgill.ca/event/587/contribution s/3702/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3702/ END:VEVENT BEGIN:VEVENT SUMMARY:Neural Network Classification of BL Lacs and FSRQs among X-ray/Gam ma-ray Blazars discovered in the Fermi 4FGL-DR4 Unassociated Catalog DTSTART;VALUE=DATE-TIME:20261028T181900Z DTEND;VALUE=DATE-TIME:20261028T182000Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3695@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Sierra Deppe (McGill University\, Penn State Univers ity)\nOf the 2423 unassociated sources in the fourth data release of the f ourth Fermi Large Area Telescope catalog (4FGL-DR4)\, 748 had also been ob served by the Neil Gehrels Swift Observatory's X-ray telescope for $>4$~ks . Neumann et al. (2026) recently used a neural network classifier to ident ify new local pulsars and high-energy blazars from these unassociated sour ces\, and they classified 173 likely blazars from $\\gamma$-ray sources wi th singular X-ray counterparts. We adopt these new likely blazar singlets\ , along with the 4FGL-DR4 blazar candidates of uncertain types\, to search for further classifications of 281 total sources into BL Lac (BLL) and fl at spectrum radio quasar (FSRQ) categories. From those 281 sources\, 218 of them had not been previously analyzed by an earlier attempt to classify blazars into these dominant sub-classifications (Kaur et al. 2023). Using infrared to $\\gamma$-ray parameters\, we identify 136 likely BL Lac obje cts (Probability of BLL\, $P_{\\text{bll}}>0.99$) and 29 likely FSRQs (wit h $P_{\\text{bll}}<0.01$) using a multilayer perceptron neural network cla ssifier\, while the remaining 116 sources remain ambiguous. A majority of these new sources are observationally much fainter than existing sources\, by one or two magnitudes\, enabling a direct probe into the lower-flux re gion of the existing blazar population. We propose further investigation i nto the optical spectra of these new\, faint FSRQs to obtain spectroscopic confirmation and redshift estimates. Confirming these new sources will te st how far into the observationally faint-source region the FSRQ populatio n extends\, and when coupled with redshifts\, have the potential to extend the low-luminosity end of the blazar sequence.\n\nhttps://nyx.physics.mcg ill.ca/event/587/contributions/3695/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3695/ END:VEVENT BEGIN:VEVENT SUMMARY:Dynamical Simulations of Self-Consistent Mass Accretion onto Black Holes in Ultralight Dark Matter DTSTART;VALUE=DATE-TIME:20261028T181800Z DTEND;VALUE=DATE-TIME:20261028T181900Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3706@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Yourong Frank Wang (University of Göttingen)\nDark matter may be made of ultra-light bosonic particles\, so light that it beh aves like a large-scale quantum wave rather than a swarm of individual par ticles ("ultralight" or "fuzzy" dark matter). This wave nature changes how massive objects like black holes move through it: the drag that normally causes objects to sink toward a galaxy's center can behave very differentl y.\n\nPrior work on a black hole moving through this kind of dark matter f ound strikingly different outcomes depending on the environment. Embedded in the dense\, wave-supported core at a galaxy's center\, the black hole d oesn't simply sink\; its orbit oscillates in a "stone-skipping" pattern as it repeatedly disturbs and rebounds off the vibrating core (Zhang\, Wang\ , Zagorac & Easther 2026). In a smoother\, more uniform environment\, our own preliminary work instead finds enhanced dynamical friction due to the formation of a dense gravitational wake.\n\nSuch prior work was based on d ynamical simulations where we held the black hole's mass fixed\, which whi le arguably a small effect\, still isn’t complete given the vast timesca les of a cosmological simulation. We add the missing piece: a black hole s hould also grow by swallowing the surrounding dark matter as it moves. We implement a physically calibrated accretion prescription\, matched to the classical accretion rate used throughout astrophysics for objects moving t hrough gas. The new tool also gives the black hole a physical momentum ki ck from the infalling matter\, not just added mass. We present early resul ts on how this self-consistent growth changes the dynamics in both environ ments considered before.\n\nhttps://nyx.physics.mcgill.ca/event/587/contri butions/3706/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3706/ END:VEVENT BEGIN:VEVENT SUMMARY:Catching Emission "Life-Lines" in Black Hole X-ray Binaries to Und erstand Relativistic Jets DTSTART;VALUE=DATE-TIME:20261028T181700Z DTEND;VALUE=DATE-TIME:20261028T181800Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3703@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Aadi Patel (University of Lethbridge)\nStars are rar ely born alone\, often existing in pairs. When one of these stars reaches the end of its life\, it can collapse into a black hole\, creating a black hole X-ray binary where it feeds off the matter of its companion star. Th is material spins rapidly\, creating a hot accretion disk (emitting X-rays ) while also launching powerful\, outflowing jets (emitting radio waves). To understand how these jets form\, this project uses data from the Atacam a Large Millimetre Array (ALMA) to identify spectral emission lines\, whic h trace where the jets slam into the interstellar medium. It was necessary to automate high-volume retrieval\, processing\, and production of calibr ated datasets through a custom pipeline to identify spectral emission line signatures utilizing Common Astronomy Software Application (CASA) package s. These lines are then mapped with radio astronomy imaging techniques to deconstruct jet formation and energy.\n\nhttps://nyx.physics.mcgill.ca/eve nt/587/contributions/3703/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3703/ END:VEVENT BEGIN:VEVENT SUMMARY:The Final Mass and Early Growth of the Intermediate-Mass Black Hol e in Omega Centauri DTSTART;VALUE=DATE-TIME:20261028T181600Z DTEND;VALUE=DATE-TIME:20261028T181700Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3700@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Mackenzie Hayduk (Saint Mary's University)\nIntermed iate-mass black holes (IMBHs)\, with masses between $10^2$ and $10^5$$M_\\ odot$\, may represent a missing link between stellar and supermassive blac k holes\, yet few compelling candidates are known. In the Milky Way globul ar cluster Omega Centauri ($\\omega$ Cen)\, Häberle et al. (2024) recentl y identified several stars near the cluster centre with projected velociti es exceeding the escape velocity\, implying the presence of a central comp act object with a mass $M_\\bullet$ ≳ $8\\times$ $10^3 M_\\odot$ and mak ing it a strong IMBH candidate. We follow up on previous work in which we jointly modelled the orbits of the five most reliably measured fast-moving stars. Simultaneously fitting Keplerian orbits to their sky positions\, p roper motions\, and line-of-sight velocities yielded an IMBH mass of $M_\\ bullet = (6.4^{+0.8}_{-0.7}) \\times 10^4$ $M_\\odot$. We predict that sky -plane accelerations for the three innermost stars will become detectable ($>3\\sigma$) by 2030\, which can confirm an IMBH and constrain its proper ties with greater precision. Our inferred mass agrees with Monte Carlo $N$ -body simulations of $\\omega$ Cen (González Prieto et al. 2025)\, which grow IMBHs to around ~ $50{\,}000$$M_\\odot$ over 12 Gyr from initial blac k hole seeds of $500$ - $5000$$M_\\odot$. However\, the formation mechanis ms for such massive seeds early in the cluster's evolution are an open que stion. Using rapid cluster-evolution models motivated by the initial condi tions of $\\omega$ Cen\, we identify viable seed-formation pathways throug h runaway stellar collisions and hierarchical black hole mergers.\n\nhttps ://nyx.physics.mcgill.ca/event/587/contributions/3700/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3700/ END:VEVENT BEGIN:VEVENT SUMMARY:Closing the AGN Feedback Loop Through Sub-kiloparsec Scale Gas Kin ematics With JWST DTSTART;VALUE=DATE-TIME:20261028T181500Z DTEND;VALUE=DATE-TIME:20261028T181600Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3689@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Mathieu Marquis (Université de Montréal)\nUndersta nding how supermassive black holes influence the galaxies they inhabit rem ains a central challenge in astrophysics. The most massive galaxies in the Universe—Brightest Cluster Galaxies at the centers of galaxy clusters —offer an exceptional laboratory to study this connection. Immersed in v ast reservoirs of hot gas\, their central black holes both accrete surroun ding material and release enormous amounts of energy\, profoundly shaping the galaxy and its environment. The nearby Centaurus cluster\, whose centr al galaxy is NGC 4696\, provides a unique opportunity to observe this inte rplay in action thanks to its proximity and its spectacular network of col d gas filaments.\n\nIn this talk\, I will present new JWST/NIRSpec IFU obs ervations that\, for the first time\, allow us to follow the entire feedba ck cycle linking black holes and galaxies—from gas cooling and condensat ion to accretion onto the black hole—across scales ranging from kpc down to pc. These observations reveal a rotating circumnuclear disk in NGC 469 6 that is directly connected to the surrounding cold filament network. Thi s structure provides the long-sought missing link that channels gas from k pc scales down to ~100 pc and ultimately into the central black hole\, eff ectively closing the feedback loop. Comparisons with stellar kinematics fu rther show that gas and stars respond very differently to the central grav itational potential and to feedback processes. \n\nThese results provide n ew insight into how supermassive black holes shape their host galaxies and illustrate the transformative power of JWST for resolving the physical pr ocesses driving galaxy evolution.\n\nhttps://nyx.physics.mcgill.ca/event/5 87/contributions/3689/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3689/ END:VEVENT BEGIN:VEVENT SUMMARY:Tangled $τ$ and Flash Reionization DTSTART;VALUE=DATE-TIME:20261028T180500Z DTEND;VALUE=DATE-TIME:20261028T181500Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3631@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Param Upadhyay (UManitoba)\nRecent cosmological tens ions have renewed interest in the role of reionization in cosmological par ameter inference. In particular\, “flash reionization” has been propos ed as a transient episode of ionization at high redshift that could increa se the Thomson optical depth\, $\\tau$\, while remaining compatible with C MB polarization measurements.\n\nIn this work\, we present the first Marko v Chain Monte Carlo analysis of flash reionization using Planck CMB temper ature\, polarization\, and lensing data. Using Planck PR4\, we find that t he CMB permits a wide range of flash redshifts\, with the allowed redshift strongly correlated with the peak ionization fraction. For benchmark scen arios at $z_{\\rm flash}=20$ and $25$\, we obtain $x_{\\rm flash}=0.24^{+0 .13}_{-0.07}$ and $0.15^{+0.07}_{-0.05}$\, respectively.\n\nDespite this a dditional freedom in the ionization history\, the standard $\\Lambda$CDM p arameters remain largely unchanged. In particular\, we find $\\tau = 0.061 \\pm0.007$ \ncompared with $\\tau=0.059\\pm0.006$ for standard tanh reioni zation. Interestingly\, repeating the analysis with Planck PR3 removes the mild preference for a flash and instead yields upper limits on its amplit ude. I will discuss what these results tell us about how much non-standard reionization history can be hidden within current CMB data and the implic ations for cosmological inference.\n\nhttps://nyx.physics.mcgill.ca/event/ 587/contributions/3631/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3631/ END:VEVENT BEGIN:VEVENT SUMMARY:Model Predictive Scoring shows specific BAO points (not Supernovae ) drive the dynamic dark energy tension DTSTART;VALUE=DATE-TIME:20261028T175500Z DTEND;VALUE=DATE-TIME:20261028T180500Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3630@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Tanveer Karim (University of Toronto)\nThe recent an alyses of DESI DR2 BAO\, Planck CMB and various Supernovae datasets have s hown preferences for dynamic dark energy (DDE) over cosmological constant at various levels of significance\, under frequentist model comparison tes ts. However\, the same analysis done with a pure Bayesian model comparison test can lead to the opposite conclusions. In contrast to these tradition al model comparison metrics\, we approach the problem along a third axis - - which model better predicts unseen data. We use the Expected Log Predict ive Density (ELPD) metric to score the predictiveness of cosmological cons tant and DDE models\, using the leave-one-redshift-block-out cross-validat ion estimator. Aggregated\, we find modest preferences for DDE\, primarily driven by the BAO. Decomposing the ΔELPD score by redshift we find that a single BAO tracer\, LRG2 (z=0.706)\, supplies the entire DDE preference. Interestingly\, the biggest outlier point\, LRG1\, contributes little to the model predictive scoring because both models fail to predict the obser vation by equal amount. On the other hand\, all SNIa datasets' ΔELPD scor es are consistent with 0\, indicating that at an out-of-distribution predi ctive level\, the DDE tension is entirely driven by one BAO point\, not SN Ia.\n\nhttps://nyx.physics.mcgill.ca/event/587/contributions/3630/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3630/ END:VEVENT BEGIN:VEVENT SUMMARY:An Exposure Time Calculator for CASTOR's UV Multi-Object Spectrogr aph DTSTART;VALUE=DATE-TIME:20261028T174500Z DTEND;VALUE=DATE-TIME:20261028T175500Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3626@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Jade Yeung (University of Manitoba)\nThe Cosmologica l Advanced Survey Telescope for Optical and UV Research (CASTOR) is a prop osed 1 meter space telescope under development by the National Research Co uncil of Canada\, the Canadian Space Agency\, and partner institutions aro und the world. It will serve as a successor to the Hubble Space Telescope (HST) at short wavelengths\, providing continued access to the ultra-viol et (UV) and blue-optical at high spatial resolution (~0.15”) over a fie ld of view ~100x larger than HST. The UV Multi-Object Spectrograph (UVMOS ) is a medium resolution (R~1500) spectrograph based on the BATMAN spectro meter that is proposed as a parallel instrument onboard CASTOR. A UVMOS h as been identified as one of the possible Canadian contributions towards N ASA’s Habitable Worlds Observatory. Here we present a pixel-based\, use r-friendly\, extensible exposure time calculator (ETC) for the CASTOR UVMO S instrument\, adaptable for other space-borne MOS missions\, as well as i llustrative science cases outlining the unique capabilities offered by CAS TOR UVMOS in the next decade.\n\nhttps://nyx.physics.mcgill.ca/event/587/c ontributions/3626/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3626/ END:VEVENT BEGIN:VEVENT SUMMARY:In-band spectral index techniques for extended radio sources DTSTART;VALUE=DATE-TIME:20261028T173500Z DTEND;VALUE=DATE-TIME:20261028T174500Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3643@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Brianna Ball (University of Alberta)\nSpectral indic es are an effective technique for differentiating between thermal and non- thermal sources of radio emission. Most often\, spectral indices are deter mined using flux measurements taken from multiple observations with differ ent instruments. Since this data is not always available\, finding indices from a single telescope observation is desirable. The reliability of thes e in-band spectral indices has not been well studied\, particularly for ex tended sources. I will discuss three different techniques for finding in-b and spectral indices using EMU (Evolutionary Map of the Universe) data fro m ASKAP (the Australian Square Kilometre Array Pathfinder). These techniqu es include: integrating fluxes in sub-bands\, temperature-temperature plot s\, and utilizing the Taylor terms produced in the imaging process. I appl y these techniques to a selection of extended sources of radio emission\, primarily supernova remnants (SNRs) and HII regions\, and assess if the in dices produced by the different techniques agree with the expected values. I examine how well the in-band techniques can differentiate between the t hermal (HII regions) and non-thermal (SNRs) source.\n\nhttps://nyx.physics .mcgill.ca/event/587/contributions/3643/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3643/ END:VEVENT BEGIN:VEVENT SUMMARY:A Synchronisation Gate for Adapting MKID Photon-Counting Data to F ourier-Transform Spectral Reduction DTSTART;VALUE=DATE-TIME:20261028T172500Z DTEND;VALUE=DATE-TIME:20261028T173500Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3648@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Irmak Aytekin (University of Toronto)\nImaging Fouri er-transform spectrographs (IFTS) such as SITELLE record spectral informat ion by scanning a Michelson interferometer mirror and are reduced with the ORBS pipeline\, which assumes conventional camera-style\, frame-based exp osures. We are developing a laboratory prototype IFTS built around Microwa ve Kinetic Inductance Detectors (MKIDs): energy-resolving\, photon-countin g sensors that read out continuously rather than in discrete frames. This mismatch between MKID's continuous photon stream and ORBS's frame-based in put format is the central obstacle to reusing existing SITELLE-heritage re duction software for the new instrument.\n\nWe present the Synchronisation Gate\, a software module that reconciles the two data formats by binning the continuous MKID photon stream along two axes simultaneously: mirror po sition\, using timestamps from the interferometer's actuator log to isolat e stable-alignment windows\, and photon energy\, using each photon's intri nsic energy resolution. An efficient binary-search-based algorithm convert s the raw photon table into a (step\, energy bin\, y\, x) frame array that ORBS can ingest directly. Because MKIDs resolve photon energy natively\, this also enables an "N-cube" strategy: splitting one photon stream into N independent energy-sliced datacubes\, each reduced in parallel through a modified ORBS roadmap that bypasses SITELLE's two-camera-specific calibrat ion steps.\n\nThe gate has been implemented and integrated into the lab's MKID data pipeline and validated against synthetic photon-stream data. Rem aining work includes full end-to-end validation on real detector data and flux calibration without on-sky standards. This work demonstrates a practi cal path for extending mature astronomical spectral-reduction software to a fundamentally different detector technology.\n\nhttps://nyx.physics.mcgi ll.ca/event/587/contributions/3648/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3648/ END:VEVENT BEGIN:VEVENT SUMMARY:Can Gravitational Lensing Explain the Extreme Mass Inference of GW 231123? DTSTART;VALUE=DATE-TIME:20261028T171500Z DTEND;VALUE=DATE-TIME:20261028T172500Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3660@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Mariah Zeroug (CITA\, University of Toronto\, Dunlap Institute)\nGW231123 is an exceptional binary black hole merger whose unu sually large component masses challenge standard expectations for stellar origins. Additionally\, its secondary mass (the less massive one) is in te nsion with the observed gravitational-wave population. Strong gravitationa l lensing provides a potential explanation\, as magnification biases the i nferred source parameters\, making a high-redshift\, lower-mass system app ear much closer and more massive.\n\nIn this talk\, I will present the res ults of an investigation into whether or not gravitational lensing can pla usibly account for the observed properties of GW231123. We find that recon ciling its secondary mass with the observed population would require an ex treme magnification. The probability of observing such a magnification is extremely low given current gravitational wave observations\, strongly dis favoring the lensing hypothesis. This work reflects Canada's growing role in gravitational-wave astrophysics\, contributing to the global effort to understand the origins of black holes and the reliability of parameter inf erence\, a field in which Canadian institutions are increasingly shaping t he scientific conversation.\n\nhttps://nyx.physics.mcgill.ca/event/587/con tributions/3660/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3660/ END:VEVENT BEGIN:VEVENT SUMMARY:Inferring the Black Hole and Accretion Parameters of Sagittarius A * from EHT Observations Using a Semianalytic Model DTSTART;VALUE=DATE-TIME:20261028T170500Z DTEND;VALUE=DATE-TIME:20261028T171500Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3637@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Braden J. Marazzo-Nowicki (McGill University Departm ent of Physics)\nThe Event Horizon Telescope (EHT) Collaboration produced the first image of the apparent shadow of the central black hole of Sagitt arius A$^*$ (Sgr A$^*$). Sgr A$^*$ source structure varies significantly o n timescales shorter than the duration of an observation\, preventing impr oved data coverage through Earth rotation aperture synthesis. This rapid v ariability provides the opportunity to quantify intrinsic variability and separate time-variable emission features from stable signatures of strong gravity and the accretion environment. To infer unknown properties of Sgr A$^*$ and its surrounding accretion flow\, we perform Bayesian inference o n a series of EHT data segments ("snapshots"). We directly fit parameters of a semianalytic emission model jointly with complex station gains to sna pshot visibilities\, then extract estimates of the time-averaged\, persist ent source structure and temporal variability by stacking snapshots in a B ayesian hierarchical model. This approach successfully reproduces paramete rs of general relativistic magnetohydrodynamic simulations using synthetic EHT observations. Even with physically motivated assumptions about the Sg r A$^*$ environment\, black hole spin and magnetic field parameters are po orly constrained by 2017 EHT observations. Our inference constrains other parameters\, favoring a nearly face-on observer inclination ($\\theta_{\\r m o} = 9.2^\\circ \\pm 3.6 ^\\circ \\pm_{\\rm v} 11.6^\\circ$)\, an emissi on peak near the horizon ($R_{\\rm peak} = 4.9 \\pm 0.1 \\pm_{\\rm v} 0.5\ \\,GM/c^2$)\, near-northern projected spin position angle ($p.a. = 7.3^\\c irc \\pm 7.08 ^\\circ \\pm_{\\rm v} 43.5^\\circ$ counterclockwise from ver tical)\, and dominant emission $43.4^\\circ \\pm 2.0^\\circ \\pm_{\\rm v} 5.9^\\circ$ above the equatorial plane\, where we separate average structu re uncertainty ($\\pm$) from the impacts of temporal variability and model misspecification ($\\pm_{\\rm v}$).\n\nhttps://nyx.physics.mcgill.ca/even t/587/contributions/3637/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3637/ END:VEVENT BEGIN:VEVENT SUMMARY:Little Red Dots from Primordial Black Holes DTSTART;VALUE=DATE-TIME:20261028T165500Z DTEND;VALUE=DATE-TIME:20261028T170500Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3661@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Dario Lorenzoni (University of Manitoba)\nRecent JWS T observations of distant luminous galaxies and compact "little red dots" suggest the existence of early supermassive black holes (SMBHs) with masse s $> 10^5\\\,M_\\odot$. Their rapid emergence challenges conventional seed ing and growth scenarios\, motivating the question: could these SMBHs be s eeded by primordial black holes (PBHs) formed from inflationary perturbati ons? \nExplaining such massive seeds requires primordial power spectrum en hancements that are stringently constrained by cosmic microwave background (CMB) spectral distortions. In this work\, we perform the first comprehen sive exploration of the parameter space capable of producing SMBH-mass PBH seeds while remaining consistent with CMB $\\mu$-distortion constraints. We adopt a model-independent approach\, and allow for an arbitrary amount of local-type non-Gaussianity. \nOur results delineate the viable region o f early Universe parameter space that can reconcile the JWST high-redshift SMBH population with inflationary theory\, and highlight that next-genera tion CMB spectral distortion telescopes will be capable of testing much of this space in the near future.\n\nhttps://nyx.physics.mcgill.ca/event/587 /contributions/3661/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3661/ END:VEVENT BEGIN:VEVENT SUMMARY:Early Black-Hole Growth Constraints from JWST DTSTART;VALUE=DATE-TIME:20261028T164500Z DTEND;VALUE=DATE-TIME:20261028T165500Z DTSTAMP;VALUE=DATE-TIME:20261023T010736Z UID:indico-contribution-52-3649@nyx.physics.mcgill.ca DESCRIPTION:Speakers: Nicole Jiang (University of Toronto)\n**Aims.** Mass ive black holes in the early Universe had limited time to assemble. We ide ntify which JWST black-hole candidates place the strongest constraints on early growth models and assess how these constraints depend on mass estima tes and growth assumptions. **Methods.** We compile 350 published measurem ents at $z\\geq4$ and analyse a primary sample of 220 objects with broad B almer-line masses. An expanded sample adds 13 tentative or conditional Bal mer-line candidates and GN-z11\, whose mass is inferred from ultraviolet l ines. We propagate reported mass uncertainties and test mass-scale shifts and alternative growth assumptions. **Results.** For $100\\\,M_\\odot$ see ds formed at $z=30$\, radiative efficiency $\\epsilon=0.1$\, and no merger boost\, 8 of the 220 objects require a lifetime-average Eddington ratio $ \\overline{f}_{\\mathrm{Edd\,req}}>1$. Five exceed unity in at least 95% o f Monte Carlo draws using the reported mass uncertainties. For UNCOVER-204 66\, COSMOS3D-13852\, and RUBIES-EGS-55604\, at least 95% of draws still r equire an average Eddington ratio above 1 after reducing each mass by $0.5 $ dex (a factor of approximately 3.2). Delaying seeding to $z=20$ gives GN -z11 the highest required average Eddington ratio. At $\\epsilon=0.05719$\ , the ideal thin-disc efficiency for a non-spinning black hole\, all 234 c entral mass estimates are reachable from $100\\\,M_\\odot$ seeds formed at $z=30$ without lifetime-average accretion above the Eddington limit.\n\nh ttps://nyx.physics.mcgill.ca/event/587/contributions/3649/ LOCATION:Online URL:https://nyx.physics.mcgill.ca/event/587/contributions/3649/ END:VEVENT END:VCALENDAR