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Mid-Infrared diversity in nearby AGN: New insights from JWST/MIRI

Type-2 quasars (QSO2s) are luminous active galactic nuclei characterized by narrow optical emission lines. They are the torus-obscured counterparts of type-1 quasars, although in some cases, part of the obscuration arises from galactic scales. Thanks to JWST , it is now possible to study the properties of nuclear gas and dust in local AGN with unprecedented spatial and spectral resolution and sensitivity. In this talk, I will present recent results from Cycle 2 JWST /MIRI observations of nearby QSO2s from the QSOFEED sample, which revealed a striking diversity of mid-infrared spectral shapes and features, and compare them with JWST /MIRI data of Seyfert galaxies from the Galactic Activity, Torus, and Outflow Survey (GATOS). Our findings highlight the complexity of these nuclear environments and underscore the need for larger JWST samples to disentangle the roles of obscuration, ionizing continuum, gas density, and other factors in shaping their mid-infrared spectra.

• Speaker: Cristina Ramos-Almeida (Astrofísica de Canarias)
• Tuesday 19 August 2025, 10:00-11:00
• Venue: Ryle Seminar Room, KICC + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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arXiv:2508.03888v1 Announce Type: new Abstract: We present Synthesizer, a fast, flexible, modular and extensible platform for modelling synthetic astrophysical observables. Synthesizer can be used for a number of applications, but is predominantly designed for generating mock observables from analytical and numerical galaxy formation simulations. These use cases include (but are not limited to) analytical modelling of the star formation and metal enrichment histories of galaxies, the creation of mock images and integral field unit observations from particle based simulations, detailed photoionisation modelling of the central regions of active galactic nuclei, and spectro-photometric fitting. We provide a number of stellar population synthesis models, photoionisation code configurations, dust models, and imaging configurations that can be used 'out-of-the-box' interactively. We invite and encourage the community to use, test and develop the code, and hope that the foundation developed will provide a flexible framework for a number of tasks in forward and inverse modelling of astrophysical observables.

arXiv:2508.04593v1 Announce Type: new Abstract: The sky-averaged Compton-$y$ distortion in the cosmic microwave background (CMB) energy spectrum, $\langle y \rangle$, provides information about energy injection in the Universe occurring at $z \lesssim 5\times10^{4}$. It is primarily sourced by the thermal Sunyaev-Zeldovich effect -- the up-scattering of CMB photons on free electrons in collapsed dark matter halos. In this work and our companion paper, Ref. [1], we perform a re-analysis of the archival COBE/FIRAS data to constrain $\langle y \rangle$. We utilize two analysis approaches: (i) fitting the sky-averaged intensity spectrum (frequency monopole) and (ii) fitting the sky spectrum in each pixel (pixel-by-pixel). We obtain the baseline upper limits $\langle y \rangle < 31\times 10^{-6}$ and $\langle y \rangle < 8.3\times 10^{-6}$ (both at $95\%$ C.L.) for these two approaches, respectively. We present the first detailed comparison of these analysis methods on both mock skies and real data. Our findings suggest that accounting for the spatial variability of foregrounds via pixel-by-pixel fitting allows for tighter constraints on $\langle y \rangle$ by a factor of $\approx 3-5$ as compared to the frequency monopole method. We show that our frequency monopole results agree well with predictions from Fisher forecast techniques based on the sky-averaged signal, which have been used for forecasting future spectral distortion experiments. Our results thus suggest that the scientific reach of future spectral distortion experiments can potentially be enhanced by a factor of a few via more optimal component separation methods, and we identify the pixel-by-pixel method as one such robust way to achieve this. We discuss the implications of our improved constraints on $\langle y \rangle$ from the pixel-by-pixel method in Ref. [1].

Title to be confirmed

Abstract not available

• Speaker: Cristina Ramos-Almeida (Astrofísica de Canarias)
• Tuesday 19 August 2025, 10:00-11:00
• Venue: Ryle Seminar Room, KICC + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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• Speaker: Karina Caputi (Groningen)
• Friday 21 November 2025, 11:30-12:30
• Venue: Ryle Seminar Room, KICC + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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arXiv:2508.01855v1 Announce Type: new Abstract: Primordial non-Gaussianity is predicted by various inflationary models, and N-body simulations are a crucial tool for studying its imprints on large-scale structure. In this work, we present \texttt{GENGARS} ( GEnerator of Non-Gaussian ARbitrary Shapes), a framework for generating accurate non-Gaussian initial conditions for N-body simulations. It builds upon the formulation introduced by Wagner \& Verde (2012), enabling to generate a primordial gravitational potential with a desired separable bispectrum $B_{\Phi}(k_1,k_2,k_3)$. For the local, equilateral and orthogonal non-Gaussian templates, we benchmark our method against the well-established \texttt{2LPT-PNG} code. We show that \texttt{GENGARS} achieves improved accuracy and lower noise by suppressing spurious contributions to the primordial power spectrum. This paper aims at presenting the method, quantifying its performance and illustrating the benefits and applicable use cases over existing approaches.

arXiv:2508.02577v1 Announce Type: new Abstract: EDGES-3 is the third iteration of the EDGES experiment, designed to measure the predicted global absorption feature in the radio spectrum produced by neutral hydrogen gas at cosmic dawn, a critical observation determining when and how the first stars populated the universe. The EDGES-3 instrument has been redesigned to include both the analog and digital electronics within the antenna, allowing for in-situ calibration and removal of the lossy balun found in EDGES-2. EDGES-3 has been on multiple deployments in the past 4 years; to Oregon, Devon Island, Adak Island, and is currently installed and taking data in the outback of Western Australia. This paper provides an accounting of the challenges inherent in the detection of the global, cosmological 21-cm signal, the strategies EDGES employs to mitigate each of these challenges, a description of the instrument, and a report on the Western Australia deployment along with observational data.

The Reionization of our Local Universe

The neighborhood in the immediate cosmological vicinity of our Milky Way is known as the Near-Field. Due to its proximity to us, it is the best-observed region of the Universe. As such it is the most interesting to study, to understand and to try and simulate, as there is a wealth of observational information available that could allow us to significantly advance our knowledge on e.g. large-scale structure and galaxy formation, feedback processes and the nature of dark matter in a range of different local environments. I will present the work we have been doing over the years to address this problem. This has been largely based on constrained simulations of the Near-Field from the CLUES project, which use our ever expanding knowledge of the local structures and their velocity fields to create numerical structure formation simulations that faithfully reproduce the local universe at present. The main focus of our work has been on understanding the potentially detectable local signatures of Cosmic Reionization, for example on the number and properties of satellites of the Local Group and locations where some of the First Stars may be located (cosmic archaeology), which I will both discuss.

• Speaker: Ilian Iliev (Sussex)
• Friday 08 August 2025, 11:30-12:30
• Venue: Ryle Seminar Room, KICC + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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arXiv:2507.22888v2 Announce Type: replace Abstract: The unexpectedly high abundance of galaxies at $z > 11$ revealed by JWST has sparked a debate on the nature of early galaxies and the physical mechanisms regulating their formation. The Atacama Large Millimeter/submillimeter Array (ALMA) has begun to provide vital insights on their gas and dust content, but so far only for extreme 'blue monsters'. Here we present new, deep ALMA observations of JADES-GS-z11-0, a more typical (sub-$L^*$) $z > 11$ galaxy that bridges the discovery space of JWST and the Hubble Space Telescope. These data confirm the presence of the [O III] 88 $\mu$m line at $4.5\sigma$ significance, precisely at the redshift of several faint emission lines previously seen with JWST/NIRSpec, while the underlying dust continuum remains undetected ($F_\nu < 9.0 \, \mathrm{\mu Jy}$), implying an obscured star formation rate (SFR) of $\text{SFR}_\text{IR} \lesssim 6 \, \mathrm{M_\odot \, yr^{-1}}$ and dust mass of $M_\text{dust} \lesssim 1.0 \times 10^{6} \, \mathrm{M_\odot}$ (all $3\sigma$). The accurate ALMA redshift of $z_\text{[O III]} = 11.1221 \pm 0.0006$ ($\gtrsim \! 5\times$ refined over NIRSpec) helps confirm that redshifts measured purely from the Lyman-$\alpha$ break, even spectroscopically, should properly take into account the effects of potential damped Lyman-$\alpha$ absorption (DLA) systems to avoid systematic overestimates of up to $\Delta z \approx 0.5$. The [O III] 88 $\mu$m luminosity of $L_\text{[O III]} = (1.0 \pm 0.3) \times 10^{8} \, \mathrm{L_\odot}$, meanwhile, agrees well with the scaling relation for local metal-poor dwarfs given the SFR measured by NIRCam, NIRSpec, and MIRI. The spatially resolved MIRI and ALMA emission also underscores that JADES-GS-z11-0 is likely to consist of two low-mass components that are undergoing strong bursts of star formation yet are already pre-enriched in oxygen (~30% solar), only 400 Myr after the Big Bang.

arXiv:2503.17342v3 Announce Type: replace Abstract: We present an updated reconstruction of the dark energy equation of state, $w(a)$, using the newly released DESI DR2 Baryon Acoustic Oscillation (BAO) data in combination with Pantheon+ and DES5Y Type Ia supernovae measurements, respectively. Building on our previous analysis in arXiv:2503.08658, which employed a nonparametric flexknot reconstruction approach, we examine whether the evidence for dynamical dark energy persists with the improved precision of the DESI DR2 dataset. We find that while the overall qualitative structure of $w(a)$ remains consistent with our earlier findings, the statistical support for dynamical dark energy is reduced when considering DESI DR2 data alone, particularly for more complex flexknot models with higher numbers of knots. However, the evidence for simpler dynamical models, such as $w$CDM and CPL (which correspond to $n=1$ and $n=2$ knots respectively), increases relative to $\Lambda$CDM with DESI DR2 alone, with CPL being the preferred dynamical model, consistent with previous DESI analyses. When combined with Pantheon+ data, the conclusions remain broadly consistent with our earlier work, but when instead combined with DES5Y supernovae data, there is an increased preference for flexknot models for all values of $n$ considered. This results in all such models being preferred over $\Lambda$CDM, with the CPL model being the most favoured by a Bayes factor of $\sim 2.3$ relative to $\Lambda$CDM.

arXiv:2508.00611v1 Announce Type: new Abstract: We compute the two-loop effective field theory (EFT) power spectrum of dark matter density fluctuations in $\Lambda$CDM using the recently proposed COBRA method (Bakx. et al, 2025). With COBRA, we are able to evaluate the two-loop matter power spectrum in $\sim 1$ millisecond at $ \sim 0.1 \%$ precision on one CPU for arbitrary redshifts and on scales where perturbation theory applies. As an application, we use the nonlinear matter power spectrum from the Dark Sky simulation to assess the performance of the two-loop EFT power spectrum compared to the one-loop EFT power spectrum at $z=0$. We find that, for volumes typical for Stage IV galaxy surveys, $V = 25 \,(\text{Gpc}/h)^3$, the two-loop EFT can provide unbiased cosmological constraints on $\Omega_m,H_0$ and $A_s$ using scales up to $k_\text{max}=0.26\, h/\text{Mpc}$, thereby outperforming the constraints from the one-loop EFT ($k_\text{max}=0.11\, h/\text{Mpc}$). The Figure of Merit on these three parameters increases by a factor $\sim 1.9$ and the one-dimensional marginalized constraints improve by $\sim35\%$ for $\Omega_m$, $\sim20\%$ for $H_0$ and $\sim 15\%$ for $A_s$.

Title to be confirmed

Abstract not available

• Speaker: Speaker to be confirmed
• Friday 08 August 2025, 11:30-12:30
• Venue: Ryle Seminar Room, KICC + online.
• Series: Galaxies Discussion Group; organiser: Sandro Tacchella.

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arXiv:2507.23774v1 Announce Type: new Abstract: Recent JWST observations have revealed a puzzling population of optically red and compact galaxies with peculiar "V"-shaped spectra at high redshift, known as "Little Red Dots" (LRDs). Until now, most spectroscopically confirmed LRDs are found at z > 4 and it has been speculated that LRDs are tracing the early stages of black hole evolution. We report an independent rediscovery of a broad-line active galactic nucleus (AGN), SDSS J102530.29+140207.3, at z = 0.1, which shows spectral features matching those of LRDs seen in the early Universe, including the V-shaped spectrum, broad Balmer lines (with widths of 1000-2000 km/s), and deep Balmer absorption. We present a new GTC observation of this LRD, which reveals an optical continuum similar to those of G-to-K giant stars including an unambiguous G-band absorption originating from the CH molecule. In addition, this local LRD shows a series of absorption lines potentially related to low-ionization ions or atoms but are deeper than what is observed in empirical stellar templates. We further identify a series of [FeII] emission lines indicative of low-ionization gas, which we find also present in an JWST-selected LRD at z = 2.26. We find small but statistically significant variability in H$\alpha$ consistent with previous findings. Finally, with the new X-ray observation from NuSTAR, we confirm the extreme X-ray weakness of this LRD, which might imply Compton-thick gas obscuration with $N_{\rm H}>10^{24}~{\rm cm^{-2}}$. All evidence suggests SDSS J102530.29+140207.3 has a complex gaseous environment and the strong ionic, atomic, and molecular absorptions are hard to explain with typical stellar and AGN models.

arXiv:2507.23212v1 Announce Type: new Abstract: The formation mechanisms of merging binary black holes (BBHs) observed by the LIGO-Virgo-KAGRA collaboration remain uncertain. Detectable eccentricity provides a powerful diagnostic for distinguishing between different formation channels, but resolving their eccentricity distributions requires the detection of a large number of eccentric mergers. Future gravitational wave detectors such as the Einstein Telescope and Cosmic Explorer will detect tens of thousands of BBH mergers out to redshifts $z \ge 10$, making it critical to understand the redshift-dependent evolution of eccentricity distributions. We simulate this evolution for two key channels: dynamical assembly in globular clusters (GCs), which leads to rapid, eccentric mergers; and hierarchical triples in the field, where three-body dynamics can induce eccentricity in the inner binary. When considering all BBH mergers, the GC channel dominates overall, consistent with previous studies. However, when focusing on mergers with detectable eccentricity in next-generation detectors, we find that hierarchical triples dominate the eccentric merger rate at $0\le z \le 4$, with GC mergers becoming competitive at higher redshifts. Across all model variations, eccentric mergers in the local Universe ($z\lesssim 1$) have significant contributions from field triples, challenging the common view that such systems primarily form in dense environments. We show that, regardless of cluster and stellar evolution uncertainties, hierarchical triples contribute at least 30 per cent of eccentric mergers across a large range of redshifts.

Science, Volume 389, Issue 6759, Page 438-439, July 2025.

arXiv:2507.09228v3 Announce Type: replace Abstract: Constraints on the cosmological parameters of Torsion Condensation (TorC) are investigated using Planck 2018 Cosmic Microwave Background data. TorC is a case of Poincar\'e gauge theory -- a formulation of gravity motivated by the gauge field theories underlying fundamental forces in the standard model of particle physics. Unlike general relativity, TorC incorporates intrinsic torsion degrees of freedom while maintaining second-order field equations. At specific parameter values, it reduces to the $\Lambda$CDM model, providing a natural extension to standard cosmology. The base model of TorC introduces two parameters beyond those in $\Lambda$CDM: the initial value of the torsion scalar field and its time derivative -- one can absorb the latter by allowing the dark energy density to float. To constrain these parameters, `PolyChord` nested sampling algorithm is employed, interfaced via `Cobaya` with a modified version of `CAMB`. Our results indicate that TorC allows for a larger inferred Hubble constant, offering a potential resolution to the Hubble tension. Tension analysis using the $R$-statistic shows that TorC alleviates the statistical tension between the Planck 2018 and SH0Es 2020 datasets, though this improvement is not sufficient to decisively favour TorC over $\Lambda$CDM in a Bayesian model comparison. This study highlights TorC as a compelling theory of gravity, demonstrating its potential to address cosmological tensions and motivating further investigations of extended theories of gravity within a cosmological context. As current and upcoming surveys -- including Euclid, Roman Space Telescope, Vera C. Rubin Observatory, LISA, and Simons Observatory -- deliver data on gravity across all scales, they will offer critical tests of gravity models like TorC, making the present a pivotal moment for exploring extended theories of gravity.

arXiv:2507.22888v1 Announce Type: new Abstract: The unexpectedly high abundance of galaxies at $z > 11$ revealed by JWST has sparked a debate on the nature of early galaxies and the physical mechanisms regulating their formation. The Atacama Large Millimeter/submillimeter Array (ALMA) has begun to provide vital insights on their gas and dust content, but so far only for extreme 'blue monsters'. Here we present new, deep ALMA observations of JADES-GS-z11-0, a more typical (sub-$L^*$) $z > 11$ galaxy that bridges the discovery space of JWST and the Hubble Space Telescope. These data confirm the presence of the [O III] 88 $\mu$m line at $4.5\sigma$ significance, precisely at the redshift of several faint emission lines previously seen with JWST/NIRSpec, while the underlying dust continuum remains undetected ($F_\nu < 9.0 \, \mathrm{\mu Jy}$), implying an obscured star formation rate (SFR) of $\text{SFR}_\text{IR} \lesssim 6 \, \mathrm{M_\odot \, yr^{-1}}$ and dust mass of $M_\text{dust} \lesssim 1.0 \times 10^{6} \, \mathrm{M_\odot}$ (all $3\sigma$). The accurate ALMA redshift of $z_\text{[O III]} = 11.1221 \pm 0.0006$ ($\gtrsim \! 5\times$ refined over NIRSpec) helps confirm that redshifts measured purely from the Lyman-$\alpha$ break, even spectroscopically, should properly take into account the effects of potential damped Lyman-$\alpha$ absorption (DLA) systems to avoid systematic overestimates of up to $\Delta z \approx 0.5$. The [O III] 88 $\mu$m luminosity of $L_\text{[O III]} = (1.0 \pm 0.3) \times 10^{8} \, \mathrm{L_\odot}$, meanwhile, agrees well with the scaling relation for local metal-poor dwarfs given the SFR measured by NIRCam, NIRSpec, and MIRI. The spatially resolved MIRI and ALMA emission also underscores that JADES-GS-z11-0 is likely to consist of two low-mass components that are undergoing strong bursts of star formation yet are already pre-enriched in oxygen (~30% solar), only 400 Myr after the Big Bang.

arXiv:2507.22858v1 Announce Type: new Abstract: JWST has shed light on galaxy formation and metal enrichment within 300 Myr of the Big Bang. While luminous galaxies at $z > 10$ often show significant [O III]$\lambda\lambda$4959, 5007 emission lines, it remains unclear whether such features are prevalent among fainter, more typical galaxies due to observational limits. We present deep imaging and spectroscopy of JADES-GS-z14-1 at $z_\mathrm{spec}=13.86^{+0.04}_{-0.05}$, currently the faintest spectroscopically confirmed galaxy at $z\approx 14$. It serendipitously received 70.7 hours of MIRI/F770W imaging in the JWST Advanced Deep Extragalactic Survey (JADES), the deepest MIRI exposure for any high-redshift galaxy to date. Nonetheless, we detect only tentative F770W emission of $7.9\pm2.8$ nJy at $2.8\sigma$ significance, constraining the total equivalent width of [O III]$\lambda\lambda$4959, 5007 + H$\beta$ to $520^{+400}_{-380}$ A, weaker than most $z > 10$ galaxies with MIRI detections. This source is unresolved across 16 NIRCam bands, implying a physical radius $\lesssim50$ pc. NIRSpec/PRISM spectroscopy totaling 56 hours reveals no rest-frame ultraviolet emission lines above $3 \sigma$. Stellar population synthesis suggests a stellar mass $\sim4\times 10^{7}$ $\mathrm{M_\odot}$ and a star formation rate $\sim 2$ $\mathrm{M_\odot yr^{-1}}$. The absence of strong metal emission lines despite intense star formation suggests a gas-phase metallicity below 10% solar and potentially a high escape fraction of ionizing photons. These deep observations provide rare constraints on faint, early galaxies, tracing the onset of chemical enrichment and ionization in the early Universe.

arXiv:2507.22110v1 Announce Type: new Abstract: We present an efficient and accurate pipeline for the analysis of the redshift-space galaxy bispectrum multipoles at one-loop order in effective field theory (EFT). We provide a systematic theory derivation based on power counting, which features the first comprehensive treatment of stochastic EFT contributions -- these are found to significantly improve the match to data. Our computational pipeline utilizes the COBRA technique that expands the linear matter power spectrum over a basis of principal components based on a singular value decomposition, allowing the cosmology dependence to be captured to sub-permille accuracy with just eight templates. This transforms the problem of computing the one-loop EFT bispectrum to a simple tensor multiplication, reducing the computation time to around a second per cosmology with negligible loss of accuracy. Using these tools, we study the cosmological information in the bispectrum by analyzing PTChallenge simulations, whose gigantic volume provides the most powerful test of the one-loop EFT bispectrum so far. We find that the one-loop prediction provides an excellent match to the bispectrum data up to $k_{\rm max}=0.15~h$ Mpc$^{-1}$, as evidenced by the precise recovery of the dark matter density $\omega_\text{cdm}$, Hubble constant $H_0$, and mass fluctuation amplitude $\sigma_8$ parameters, and the amplitude of equilateral primordial non-Gaussianity (PNG) $f_{\rm NL}^{\rm equil}$. Combined with the power spectrum, the COBRA-based one-loop bispectrum multipoles yield tighter constraints than the tree-level bispectrum monopole, with the posteriors on $\omega_{\text{cdm}}$, $H_0$, and $\sigma_8$ shrinking by 43\%, 31\%, and 4\%, respectively. This suggests that the COBRA-based bispectrum analysis will be an important tool in the interpretation of data from ongoing redshift surveys such as DESI and Euclid.

arXiv:2504.02829v3 Announce Type: replace-cross Abstract: The decay of metastable 'false vacuum' states via bubble nucleation plays a crucial role in many cosmological scenarios. Cold-atom analog experiments will soon provide the first empirical probes of this process, with potentially far-reaching implications for early-Universe cosmology and high-energy physics. However, an inevitable difference between these analog systems and the early Universe is that the former have a boundary. We show, using a combination of Euclidean calculations and real-time lattice simulations, that these boundaries generically cause rapid bubble nucleation on the edge of the experiment, obscuring the bulk nucleation that is relevant for cosmology. We demonstrate that implementing a high-density 'trench' region at the boundary completely eliminates this problem, and recovers the desired cosmological behavior. Our findings are relevant for ongoing efforts to probe vacuum decay in the laboratory, providing a practical solution to a key experimental obstacle.