Calendar

Taking over the Dark Side of Early SFRD through Radio Selected NIR-dark Galaxies

Charting the Back-in-Time Evolution of the Stellar Mass–Velocity Dispersion Relation for Early-Type Galaxies

Massive early-type galaxies (ETGs) are “red and dead” systems mainly composed of old and metal-rich stellar populations. In a cosmological context, present-day ETGs are believed to be the remnants of a complex stellar mass assembly history marked by several mergers, which are the consequence of the underlying hierarchical assembly of their host dark matter halos. In this talk, I will deal with the merger-driven evolution of ETGs, describing how the scaling relation between stellar mass and stellar velocity dispersion evolves across cosmic time, and how the stellar populations of progenitor galaxies settled into the final remnants. Specifically, by extending the results of Cannnarozzo, Sonnenfeld & Nipoti (2020), I have been modelling the aforementioned relation through a Bayesian hierarchical approach, considering ETGs with log(M∗/M⊙) ≳ 9 over the redshift range 0 ≲ z ≲ 4. Together with a new characterisation of the relation, I have been reconstructing the back-in-time evolutionary pathways of individual ETGs to answer the question “how did high-redshift ETGs assemble through cosmic time to reach the functional form of the relation in the present-day Universe?“.

Convergence of the simulated Lyman alpha forest at z>5

The Lyman alpha forest at very high z (>5), arising from gas in the intergalactic medium (IGM), can serve as a probe of the thermal history of the IGM, the metagalactic ionizing background, dark matter characteristics, and reionization. Depending on the degree of pre-reionization X-ray heating, the IGM could potentially cool to temperatures on the order of <10 K by z=10, allowing for the formation of sub-kpc structure, far smaller than the spatial resolutions of typical cosmological simulations used in investigations of IGM structure. With evidence mounting for an extremely late end to reionization (z<6), which limits the time available for thermodynamic relaxation after photoheating, the pre-reionization small scale structure may survive longer than anticipated, tightening the resolution requirements to accurately model the post-reionization IGM. To characterize the impact of reionization’s timing on convergence, we perform a set of simulations using the Nyx code, exploring the interaction with box size and spatial resolution on the properties of the matter distribution and the simulated Lyman alpha forest. We find that the measured pressure smoothing scale and Lyman alpha power at small physical scales (log k/(s/km) > -1.0) still differ by ~20 percent when increasing the grid resolution from 10 kpc to 5 kpc. Further, while the mean flux is converged for <10 kpc for a given reionization history, the value can differ by tens of percent between an early (z=9) and a late (z=5.5) reionization timing. We conclude that the 10-20 kpc resolution commonly used in cosmological simulations of the IGM may be inadequate for predicting the impact of reionization on small scale Lyman alpha power, especially in the case of late reionization.

Inclusive Pedagogy and curricula

Educators have an important role in ensuring that all of their students feel included and empowered to do well with their studies. However, higher education is often not designed to support those with diverse needs and this can be exacerbated at doctoral level. In this talk, we will discuss some of the ways that physics higher education can better support students through inclusive pedagogy. In particular, we will explore the concept of universal design for learning and how peer support networks can empower doctoral students in physics.

Extracting Properties of the Galactic Environment via Lyα Radiative Transfer Modeling in a Multiphase, Clumpy Medium

The Lyα emission line encodes abundant physical information about its surrounding gaseous medium in a galactic environment. Nevertheless, the resonant nature of Lyα complicates the modeling and interpretation of the line profile. In this talk, I will present the recent developments of Lyα radiative transfer (RT) modeling in a multiphase, clumpy medium and how the model helps us interpret observed Lyα spectra in a more physically realistic context. I will then present a new application of the model, which is to fit the KCWI-observed radially-varying Lyα profiles of a sample of z ~ 2 extreme emission line galaxies in a spatially-resolved manner. Our model successfully reproduces the radial trends of several Lyα spectral properties, including the peak flux ratio, peak separation and flux at the line center, and we reveal the physical reasons for such spatial variations from an RT perspective. Finally, we show that when combined with down-the-barrel UV absorption line observations, our modeling suggests a self-consistent picture of the circumgalactic medium and the galactic fountain.

TITLE: Tracing the inception of the cluster era

ABSTRACT:

Until now, direct observations of the intracluster medium (ICM) have been limited only to mature clusters in the latter three-quarters of the history of the Universe, and we have been lacking a direct view of the hot, thermalised  cluster atmosphere beyond z~2, the epoch when the first massive clusters formed. Probing the thermal evolution of cosmic structures through z~2 — the epoch when intracluster gas starts to assemble and virialise, and cosmic star formation and the activity of active galactic nuclei (AGN) manifest a concurrent peak — is however crucial for exploring the link between galaxy clusters and their over-dense progenitors, as well as finding the observational fingerprint of feedback effects that regulate the later coevolution of the galaxy and intracluster/circumgalactic medium ecosystems.

In my talk, I will present our recent detection of the thermal Sunyaev-Zeldovich (SZ) effect in the direction of the protocluster complex surrounding the famous Spiderweb Galaxy (z~2.16), made possible only thanks to the superior capabilities of the Atacama Large Millimeter/Submillimeter Array (ALMA). Such identification of a nascent intracluster halo represents the unambiguous proof that we are witnessing the transition through which a sparse overdensity of galaxies turns into a massive galaxy cluster, providing a statistically meaningful confirmation of long-standing predictions from cosmological simulations, and cluster and galaxy evolution models.

Title: AGN Feedback in and around galaxies

Abstract: Cosmological simulations predict that AGN feedback is responsible for suppressing the growth of massive galaxies and is believed to be a key process in reproducing basic properties of galaxies (such as luminosity function, the black hole–spheroid relationships, galaxy sizes, galaxy colour bi-modality). There have been a number of studies that have suggested an anti-correlation between ionised outflows (traced with [O III]) and star formation (traced using H-alpha) in the host galaxies of high-luminosity AGN. However, the H-alpha line is susceptible to obscuration by dust, therefore this anti-correlation between star-formation and outflows might be caused by dust obscuration, rather than star-formation suppression.

I will present results of the two largest AGN IFU survey at Cosmic Noon, mapping [OIII], Halpha using VLT/KMOS and VLT/SINFONI IFU instrument in combination with dust emission using ALMA. This combination enables us to map both the obscured and unobscured star-formation as well as any AGN-driven outflows in the host galaxies of these AGN. I will also show the importance of resolution and depth of the observations by showing our analysis of the JWST/NIRSPEC ERS.

Finally, I will present our latest result of stacking ALMA observations of CO, [CI] and dust continuum observations of z~2.5 extremely red quasars showing evidence of cold gas and dust halos around these hyper luminous QSOs.

Title: Gotta Catch ’Em All! – modelling I 12 star-forming galaxies from JWST

Abstract: We are studying ten recently discovered JWST candidates at z>~12, two of which have spectroscopic confirmation, using the Meraxes semi-analytic galaxy formation model. We applied the model to a cosmological simulation with effectively a trillion particles to resolve every atomic-cooling galaxy at z<=20 in a volume of >300cMpc side length. We varied model parameters to reproduce the observed UV luminosity function up to z~13 in our fiducial outputs, aiming for a statistically representative, modelled, high-redshift galaxy catalogue.

Using the forward-modelled JWST photometry, we identified hundreds of galaxies in our fiducial model that resemble the confirmed JWST galaxies and I will present summary of their properties in this talk. For the remaining bright candidates, although challenging, we still successfully identified high-redshift analogues for candidates at z ~13 and I will present some of their possible evolutionary paths during this talk. To reproduce the z>~16 JWST candidates, I will show that the model requires maximized efficiencies to form stars with no feedback regulation, suggesting galaxy formation in these first galaxies could differ significantly from their lower-redshift counterparts. I will also present dusty or quiescent galaxies at z~5 that share similar SEDs as these JWST candidates and compare their formation histories against the high-redshift analogues.

Title: Full of Orions? Dissecting dusty galaxies in the early Universe

Abstract:

The first few Gyr after the Big Bang are the most dramatic chapters of the cosmic history. Half of all stars formed in this epoch, mainly in dust-enshrouded, sub-mm bright galaxies. However, these dusty giants are often invisible to optical telescopes and have to be studied at sub-mm wavelengths, with limited spatial resolution, sensitivity, and bandwidth. Thus, despite two decades of effort, key characteristics of high-redshift dusty galaxies – how is their star formation distributed? how does it relate to their diffuse and dense gas content? – remain uncertain.

Thankfully, rapid advances in mm-wave technology are helping dissect galaxies in the early Universe in unprecedented detail and complexity. I will show recent results from high-resolution studies of the obscured star formation and gas content of dusty galaxies, achieved using ALMA, NOEMA, and VLA. These provide first views of the complex morphologies and extreme conditions in these distant galaxies. Finally, I will outline the challenge for the 2030’s: scaling these studies up to hundreds of galaxies via a massive, SDSS-like surveys at sub-mm wavelengths using ultra-wideband spectroscopy.