Adding abstracts

workshop.html

@@ -81,7 +81,7 @@
 		    <td>10:40 - 11:00</td>		  
 		    <td><strong>Radhika Achikanath Chirakkara</strong><br>Magnetic field amplification in galaxy clusters with hybrid particle-in-cell simulations</td>
 		    <td><strong><a href="#Panther">Fiona Panther</a></strong><br>More than the sum of their parts: Resolving the boundary between black holes and neutron stars with post-merger gravitational waves</td>
-		    <td><strong>Mark Walker</strong><br>A simple framework for understanding the R Coronae Borealils stars</td>
+		    <td><strong><a href="#Walker">Mark Walker</a></strong><br>A simple framework for understanding the R Coronae Borealils stars</td>
 		  </tr>
 		  <tr style="vertical-align:top">
 		    <td>11:00 - 11:40</td>
@@ -93,13 +93,13 @@
 		    <td>11:40 - 12:00</td>
 		    <td><strong><a href="#Banerjee">Amrita Banerjee</a></strong><br>Does assembly bias have a role in AGN activity?</td>
 		    <td><strong><a href="#Hu">Fitz Hu</a></strong><br>How do tidal disruption events shine in optical and radio?</td>
-		    <td><strong>Claudia Reyes</strong><br>Acoustic Oscillations in the Open Cluster M67 Probe Deep Stellar Envelopes</td>
+		    <td><strong><a href="#Reyes">Claudia Reyes</a></strong><br>Acoustic modes in M67 cluster stars trace deepening convective envelopes</td>
 		  </tr>
 		  <tr style="vertical-align:top">
 		    <td>12:00 - 12:20</td>
 		    <td><strong><a href="#Croton">Darren Croton</a></strong><br>Cosmic dust as a dark matter discriminator</td>
 		    <td><strong>Aswathi Nair</strong><br>Discovering the origins of Gravitational wave sources - Double Neutron star edition</td>
-		    <td><strong>Evgeni Grishin</strong><br>Triple systems on the edge of chaos</td>
+		    <td><strong><a href="#Grishin">Evgeni Grishin</a></strong><br>Triple systems on the edge of chaos</td>
 		  </tr>
 		  <tr style="vertical-align:top">
 		    <td>12:20 - 12:40</td>
@@ -116,7 +116,7 @@
 		  <tr style="vertical-align:top">
 		    <td>13:40 - 14:00</td>
 		    <td><strong><a href="#Tapia">Truman Tapia</a></strong><br>Formation of ultra-diffuse galaxies and their globular cluster systems through mergers</td>
-		    <td><strong>Ryosuke Hirai</strong><br>Influence of companion stars on supernovae: the tale of SN2022jli</td>
+		    <td><strong><a href="#Hirai">Ryosuke Hirai</a></strong><br>Influence of companion stars on supernovae: the tale of SN2022jli</td>
 		    <td><strong>Discussion: stars and planets</strong></td>
 		  </tr>
 		  <tr style="vertical-align:top">
@@ -144,7 +144,7 @@
 		  </tr>
 		  <tr style="vertical-align:top">
 		    <td>15:40 - 16:00</td>
-		    <td><strong>Geoff Bicknell</strong><br>Jet-mediated AGN feedback in galaxy evolution</td>
+		    <td><strong><a href="#Bicknell">Geoff Bicknell</a></strong><br>Jet-mediated AGN feedback in galaxy evolution</td>
 		    <td><strong><a href="#Krumholz">Mark Krumholz</a></strong><br>Displaced gamma-rays from Terzan 5 as a probe of cosmic ray transport</td>
 		  </tr>
 		  <tr style="vertical-align:top">
@@ -490,6 +490,10 @@
 		  <strong><a id="Banerjee">Amrita Banerjee</a></strong><br>
 		  <em>Does assembly bias have a role in AGN activity?</em><br>
 		  We compare the spatial clustering and physical properties of the active galactic nuclei (AGN) and star-forming galaxies (SFG) at fixed stellar mass using a volume-limited sample from the Sloan Digital Sky Survey (SDSS). The analysis of the two-point correlation function shows that the AGN are more strongly clustered than the SFG. The closer proximity to the 5th nearest neighbour for the AGN than that for the SFG indicates that AGN prefers the denser regions. We compare the distributions of the (u−r) colour, star formation rate (SFR), D4000 and concentration index of the AGN and SFG after matching their stellar mass distributions. The null hypothesis can be rejected at >99.99% confidence level in each case. The comparisons are also carried out at different densities. The differences persist at the same significance level in both the high and low-density regions, implying that such differences do not originate from the variations in the density. Alternatively stated, the AGN activity can be triggered in both the high and low-density regions. An analysis of the correlations between the different physical properties at fixed stellar mass reveals that the anticorrelations of SFR with morphology, colour and recent star formation history are 2−3 times stronger for the AGN than for the SFG. It suggests that the presence of a bulge and the availability of gas are the two most crucial requirements for AGN activity. We propose a picture where the galaxies at fixed stellar mass may have widely different assembly histories, leading to significant variations in bulge properties and cold gas content. Whether a galaxy of a given stellar mass can acquire the suitable conditions for AGN activity remains uncertain due to a broad diversity of assembly history. We conclude that AGN are stochastic phenomena owing to an underlying role of the assembly bias.<br><br>
+
+		  <strong><a id="Bicknell">Geoff Bicknell</strong><br>
+		  <em>Jet-mediated AGN feedback in galaxy evolution</em><br>
+		  In this talk I shall review simulations of jets interacting with an inhomogeneous interstellar medium and the implications for the quenching of star formation through turbulence and related outflows.<br><br>
 
 		  <strong><a id="Chan">Kenny Chan</a></strong><br>
 		  <em>Investigating Hierarchical Star Formation in the 30 Doradus Region and Orion Cluster</em><br>
@@ -507,10 +511,18 @@
 		  <em>HI Terminal Velocities in hydrodynamic N-body "surrogate" models of the Milky Way</em><br>
 		  The development of an N-body/hydrodynamic “surrogate'' model of the Milky Way (MW) - a model that closely resembles the MW after many Gyrs of evolution - would be extremely beneficial for Galactic Archaeology. We examined two new MW “surrogate” models, built with the Nexus framework. These new models include gas and hence are more advanced compared to the previous Nexus MW surrogate model. The most sophisticated simulation allows gas to evolve thermodynamically, and includes star formation, metal production, and stellar feedback. In this talk, I will discuss results obtained from these simulations with a focus on the so-called “HI terminal velocity curve'' -  a heliocentric measurement of the maximum Vlos as a function of Galactic longitude (l). It is a powerful approach to indirectly estimating the gas dynamics, because it does not require knowledge about the distance to individual gas clouds, which is difficult to estimate. A comparison of the terminal velocities and recovered rotation curve values in the simulations against observations suggests that the models are in need of further refinement. I close my presentation by discussing possible ways forward for future models. <br><br>
 
+		  <strong><a id="Grishin">Evgeni Grishin</a></strong><br>
+		  <em>Triple systems on the edge of chaos</em><br>
+		  I'll describe the pivotal role of triple systems in shaping the formation, observed properties and stability of various systems, from planetary satellites to merging black holes. In particular, I'll also show recent results on the stability of retrograde exoplanets in eccentric binaries and the effects of tertiaries on close chemically homogeneous massive binary exolution. <br><br>
+
 		  <strong><a id="Hansen">Samuel Hansen</a></strong><br>
 		  <em>Constraining radio AGN energetics and environments with the semi-analytic model RAiSE</em><br>
 		  The energy released by powerful radio AGNs – termed kinetic-mode feedback – is an important process in the evolution of galaxies. A wealth of radio-frequency observations of these objects are being collected in large-sky surveys (e.g., ASKAP EMU, MWA GLEAM, MeerKAT MIGHTEE) encoding constraints on the energetics of AGN feedback – if only these observations can be interpreted. We present a publicly available package capable of extracting key attributes from observed radio AGN images and performing a parameter inversion to constrain their energetics. The Radio AGN in Semi-analytic Environments (RAiSE) code is used as a forward model to produce synthetic surface brightness images of radio AGN lobes, enabling a range of model parameters to be extracted from an observed source, including jet power, source age and properties of the large-scale cluster environment. We demonstrate the ability of this technique to constrain the shape of ambient density profile using only radio images, previously limited to a small number of clusters with extensive X-ray observations. This work uniquely takes advantage of RAiSE’s ability to simulate AGN lobes at different spatial resolutions to dramatically increase the speed of the MCMC-based parameter inversion. This modified MCMC algorithm will have applications in a range of disciplines enabling a step-change in the run time of parameter inversions in the right circumstances.<br><br>
 
+		  <strong><a id="Hirai">Ryosuke Hirai</a></strong><br>
+		  <em>Influence of companion stars on supernovae: the tale of SN2022jli</em><br>
+		  Massive stars that cause core-collapse supernova explosions are known to be primarily born in binary and multiple systems. The supernova event(s) is one of the most transformative epochs of the binary's life, radically altering the course of evolution then on. The importance of this phase of evolution has been long recognized, but little attention has been made to the possible interactions immediately following the supernova. In this talk, I will report results from our work on the immediate consequences of supernovae in binaries such as the interaction between the supernova ejecta and companion star and new-born neutron stars colliding with companions. As a result of ejecta-companion interaction, we found that the companion envelope can inflate for a few years to decades, significantly altering its appearance. As for neutron star-companion collisions, we found that the neutron star can sometimes penetrate the star multiple times, accreting part of the star upon each penetration. By combining the findings of these two studies, we predicted that the neutron star may penetrate the inflated part of the companion envelope multiple times, possibly making observable features. Such a case was finally observed last year, where the supernova SN2022jli displayed periodic undulations in its light curve (Moore et al. 2023, Chen et al. 2024). We also report on our detailed modelling of SN2022jli, which should provide us with more insight into how massive binaries evolve towards forming stripped-envelope supernova progenitors.<br><br>
+
 		  <strong><a id="Hu">Fitz Hu</a></strong><br>
 		  <em>How do tidal disruption events shine in optical and radio?</em><br>
 		  Tidal disruption events happen when stars getting too close to supermassive black holes. Radiations in all of X-ray, optical, IR and radio bands are observed from TDEs, whereas we still lack a universal model to explain all the observations. In this talk, I present our self-consistent hydrodynamic simulations of TDEs from a 1 solar mass star with real stellar profile disrupted around a 10^6 solar mass SMBH. We post-processed the hydrodynamic simulations and found that both optical (from thermal emissions) and radio (from synchrotron emissions) emissions produced that are consistent with the observations. Our work paves the first step towards a universal model for TDEs.<br><br>
@@ -540,6 +552,10 @@
 		  <em>More than the sum of their parts: Resolving the boundary between black holes and neutron stars with post-merger gravitational waves</em><br>
 		  Determining the maximum possible neutron star mass is an open problem in astrophysics, and remains so due to the uncertainties in how matter behaves at supranuclear densities. Neutron stars close to this maximum mass limit will form through the merger of binary neutron stars (BNS), which can be readily detected via their gravitational wave emission. We describe a Bayesian method to combine signals from many BNS mergers to search for kHz frequency gravitational waves emitted by BNS post-merger remnants, and formulate an optimal statistic for post-merger GW detection. From our analysis, we can leverage the power of hierarchical inference to determine the maximum neutron star mass through the population properties of the remnants that are left behind: a mixture of the most massive neutron stars, and the lowest mass astrophysical black holes. <br><br>
 
+		  <strong><a id="Reyes">Claudia Reyes</a></strong><br>
+		  <em>Acoustic modes in M67 cluster stars trace deepening convective envelopes</em><br>
+		  Acoustic oscillations in stars are sensitive to stellar interiors. Frequency differences between overtone modes –large separations– probe stellar density, while differences between low-degree modes –small separations– probe the sound speed gradient in the energy-generating core of main sequence Sun-like stars. At later phases of stellar evolution, characterised by inert cores, the small separations are believed to become proportional to the large separations. Here, we present clear evidence of a rapidly evolving convective zone as stars evolve from the subgiant phase into red giants. By measuring acoustic oscillations in 27 stars from the open cluster M67, we observe deviations of proportionality between small and large separations, which are caused by the influence of the bottom of the convective envelope. These deviations become apparent as the convective envelope penetrates deep into the star during subgiant and red giant evolution, eventually entering an ultra-deep regime that leads to the red giant branch luminosity bump. The tight sequence of the cluster stars, free of large spreads in ages and fundamental properties, is essential for revealing the connection between observables –small separations– and the chemical discontinuities occurring in deep stellar interiors. We use this sequence to show that combining large and small separations can improve estimations of mass and age well after the main sequence.<br><br>
+
 		  <strong><a id="Seta">Amit Seta</a></strong><br>
 		  <em>Magnetic field scale in the interstellar medium of the Milky Way</em><br>
 		  Magnetic fields play a crucial role in the dynamics of the interstellar medium of spiral galaxies and are often divided into large-scale, regular and small-scale, random components. Estimating random magnetic field properties from observations, even for our own Milky Way, has long been a challenge.  This talk addresses the challenge by utilising pulsars in the Milky Way. Using an extensive dataset of over 1300 pulsars from the Australia Telescope National Facility Pulsar Catalogue, we combine pulsar dispersion and rotation measures with theoretical models to estimate the correlation scale of random magnetic fields to be 20-30 pc. This study enhances our understanding of the magnetic field length scales, which would be useful for the interpretation of rotation measures from extragalactic radio sources and can also help us further understand the role of magnetic fields in the dynamics and evolution of galaxies.<br><br>
@@ -552,6 +568,10 @@
 		  <em>A search for dark matter annihilation from the Sagittarius Dwarf and Stream</em><br>
 		  While Dwarf Spheroidal galaxies are amongst the most promising targets for indirect dark matter (DM) detection experiments, extensive past searches have not found convincing evidence for DM annihilation in these objects. However, in Crocker et al. (2022) a gamma-ray signal was detected from the core of the Sagittarius Dwarf Galaxy (Sgr) at 8.1 sigma statistical confidence. In subsequent works we assess whether this emission could be a DM signal (Venville et al. 2024), then undertake a comprehensive re-analysis of Fermi LAT gamma-ray data to search for significant gamma-ray emission in the Sagittarius Stream. We overcome the difficulty of modelling the tidally disrupted Sgr and Sagittarius Stream DM distributions by computing the expected J-factor distribution utilising a hydrodynamic simulation of the formation of the Sgr and the Sagittarius Stream. We find the predicted J-factor value for Sgr, J_Sgr = 1.48 × 10^10 M_⊙^2 kpc^-5  (6.46 × 10^16 GeV cm^-5), would require a DM annihilation cross section incompatible with existing constraints in order for DM annihilation to explain the observed gamma-ray emission. The analysis of the Sagittarius Stream also failed to detect any significant gamma-ray emission attributable to DM annihilation. The fitted Sagittarius Stream gamma-ray emission is either degenerate with background sources or not detected in a given energy bin. This suggests significantly better characterisation of background sources is required for future analyses.<br><br>
 
+		  <strong><a id="Walker">Mark Walker</a></strong><br>
+		  <em>A simple framework for understanding the R Coronae Borealils stars</em><br>
+		  R Coronae Borealis stars are remarkable stars doing remarkable things: they are hydrogen-deficient, carbon-rich supergiants that exhibit deep declines - sometimes fading by orders of magnitude as sprays of dust block the light. I'll describe a simple model for the dust extinction events, and describe how that model also accounts for the nature of the eclipsed star as a result of helium accretion onto a white dwarf.<br><br>
+
 		  <strong><a id="Wallace">Alex Wallace</a></strong><br>
 		  <em>Characterisation of Hidden Companions to Wobbling Stars</em><br>
 		  Since its first data release, the Gaia mission has provided a wealth of knowledge about the precise positions and motions of nearby stars.  From this, we can measure parallax and proper motion to high degrees of accuracy.  However, if a star is orbited by an unseen companion, the companion’s gravitational pull causes the position measured by Gaia to be slightly distorted.  This causes a discrepancy between the measured position and the expected position of a single star which is quantified by the renormalised unit weight error (RUWE).  In this talk, I present a method of identifying and characterising stellar companions based on a star’s RUWE value and other data, with a focus on exoplanets.  I also identify how the next data release from Gaia will contain necessary information to significantly improve these results.<br><br>