arXiv subjects

Aura Obreja

Publications and source records attributed to Aura Obreja.

At least 19 recordsLinked to original sources

arXiv2026

ALMA visits the QSO MUSEUM: Connecting molecular gas and the cool circumgalactic medium around 37 z~3 quasars

Extended Ly$α$ emission is ubiquitous around quasars and traces the cool circumgalactic medium, providing insights into halo gas dynamics and active galactic nucleus feedback. However, its connection to the cold molecular gas of the host galaxies remains largely unexplored. We characterize the molecular gas reservoirs of quasars at cosmic noon and investigate their connection to extended Ly$α$ emission using ALMA CO(4-3) observations of 37 quasars at $z\sim3$ from the QSO MUSEUM survey, previously mapped in Ly$α$ with VLT/MUSE. We derive molecular gas masses and gas fractions, explore correlations with Ly$α$ nebula and quasar properties, and search for CO-emitting companions. We detect 21/37 quasars in CO(4-3), with gas masses of $M_\mathrm{gas}\approx(3-40) \times10^9\,\mathrm{M_\odot}$. Quasars with the most massive molecular gas reservoirs are associated with the centrally dimmest Ly$α$ nebulae, while those hosting the centrally brightest Ly$α$ nebulae are generally not detected in CO. This suggests that gas and dust in the hosts regulate Ly$α$ escape and consequently affect the emission from halo gas. We find evidence that lower-Eddington-ratio quasars harbor more massive gas reservoirs, while strongly accreting quasars ($λ_\mathrm{Edd} \gtrapprox 0.9$) likely deplete their gas; for example, through powerful quasar-driven outflows. Despite their higher molecular gas masses within the sample, CO-detected low-Eddington quasars exhibit low gas fractions with a median $M_\mathrm{gas}/M_* \sim 0.10$, below what is typically found for inactive star-forming galaxies. Six quasars are marginally resolved in CO, with effective radii up to $\sim 8\,\mathrm{kpc}$. In addition, we detect 14 high-fidelity companion galaxies, indicating overdense quasar environments with a quasar-galaxy cross-correlation length of $9.81^{+2.22}_{-2.05}\,h^{-1}\mathrm{cMpc}$.

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arXiv2026

Constraining the nature of active galactic nuclei through circumgalactic Lya emission at z=2-3

We present a comprehensive analysis of circumgalactic Lya nebulae around 59 unobscured and 26 obscured quasars at z=2-3, observed with the Keck Cosmic Web Imager (KCWI), to constrain the nature of active galactic nuclei (AGN) at cosmic noon. We find that Lya nebulae around unobscured quasars are significantly less symmetric having a symmetry parameter of a_w=0.2-0.6 and more spatially extended having a scale length of r_h=10.7+/-0.5 kpc than those around obscured quasars (a_w=0.6-0.8; r_h=6.6-7.7 kpc).Unobscured quasars also exhibit steeply declining velocity dispersion profiles with the slope of -4.3+/-0.4 km s^-1 kpc^-1, indicative of large-scale outflows, whereas obscured quasars display flat profiles (-0.2+/-0.7 and -0.6+/-0.4 km s^-1 kpc^-1). The degree of quasar obscuration appears to be intrinsically linked to nebular asymmetry and extent, a relationship that could be in tension with the standard orientation-based AGN unified model, as it expects unobscured-quasar nebulae to be more symmetric and compact. These results naturally fit the evolutionary scenario, where AGN feedback drives a transition from an obscured to an unobscured phase-progressively redistributing gas to larger radii, introducing anisotropy, and driving turbulence. Taken together, our findings favor the evolutionary scenario over the purely orientation-based unified model for quasars at cosmic noon.

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arXiv2025

RUBIX: Differentiable forward modelling of galaxy spectral data cubes for gradient-based parameter estimation

Although integral-field spectroscopy enables spatially resolved spectral studies of galaxies, bridging particle-based simulations to observations remains slow and non-differentiable. We present RUBIX, a JAX-based pipeline that models mock integral-field unit (IFU) cubes for galaxies end-to-end and calculates gradients with respect to particle inputs. Our implementation is purely functional, sharded, and differentiable throughout. We validate the gradients against central finite differences and demonstrate gradient-based parameter estimation on controlled setups. While current experiments are limited to basic test cases, they demonstrate the feasibility of differentiable forward modelling of IFU data. This paves the way for future work scaling up to realistic galaxy cubes and enabling machine learning workflows for IFU-based inference. The source code for the RUBIX software is publicly available under https://github.com/AstroAI-Lab/rubix.

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arXiv2025

Testing the AGN unified model with simulated emission lines from the circumgalactic medium (CGM)

The CGM around unobscured AGN has received much attention in recent years. Comparatively, nebulae associated with obscured AGN are less studied. Here, we simulate the Ly$α$, H$α$, and HeII nebulae around the two types of AGN at $z=2-3$ with ten massive systems from the FIRE simulations based on the unified model to show their differences and to test if they can be used to constrain the AGN model. We post-process the data with the CLOUDY and the Ly$α$ radiative transfer code, RASCAS. Overall, we find that the Ly$α$ nebulae around the unobscured AGN (type-I nebulae) and obscured AGN (type-II nebulae) do not exhibit significant differences in the luminosity, area, and HeII/Ly$α$ when the simulated cutout is set to the halo virial radius. Whereas, the type-II nebulae exhibit less symmetric morphologies, flatter surface brightness profiles, and larger emission line widths (at $R\geq 10$ kpc) than those of the type-I nebulae. These nebulae properties exhibit complicated correlations with the AGN, indicating that nebulae observations can be applied to constrain the AGN engine. However, independent observations on nebulae in the mentioned emissions are insufficient to test the unified model as a priori in observations is not possible to know the direction and opening angle of the ionization cone. We prompt that the joint observations of Ly$α$ nebulae and radio jets can help to reveal the ionization cone to probe the unified model. Our calculations suggest that this method requires $\geq 75$ type-II Ly$α$ nebulae with current instruments to reach a confidence level of $\geq 95\%$.

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arXiv2025

QSO MUSEUM III: the circumgalactic medium in Ly$α$ emission around 120 $z\sim3$ quasars covering the SDSS parameter space. Witnessing the instantaneous AGN feedback on halo scales

Recent surveys show that $z>2$ quasars are surrounded by Hydrogen Lyman-$α$ (Ly$α$) glows with diverse emission levels and extents. These seem to depend on the activity of embedded quasars, the number of active galactic nucleus (AGN) photons able to reach the halo gas or circumgalactic medium (CGM) and the physical properties of the CGM. In this framework, we present VLT/MUSE snapshot observations (45 min/source) of 59 $z\sim3$ quasars extending the long-term QSO MUSEUM campaign to fainter SDSS sources. The whole survey now targets 120 quasars with a median redshift of $z$=3.13, and bolometric luminosities, black hole masses and Eddington ratios of $45.1<\log(L_{\rm bol}/[{\rm erg\,s^{-1}]})<48.7$, $7.9<\log(M_{\rm BH}/[{\rm M_{\odot}]})<10.3 $ and $0.01<λ_{\rm Edd}<1.8$, respectively. We detect extended Ly$α$ emission in 110/120 systems, with all non-detections in the new fainter sample. Stacking non-detections unveils emission below our individual detection limit. The Ly$α$ surface brightness (SB$_{\rm Lyα}$) of the CGM increases with quasar luminosity. Moreover, the Ly$α$ linewidth increases in the central regions (projected radius $R<40$ kpc or $\sim$40% $R_{\rm vir}$) of the CGM around brighter quasars. These trends indicate that we are witnessing the instantaneous AGN feedback in action on CGM scales. Assuming that all targeted quasars sit in halos of $M_{\rm DM}\sim10^{12.5}\,M_\odot$, as found in clustering studies, the trend in SB$_{\rm Lyα}$ can be explained by larger fractions of cool gas mass illuminated, implying that brighter quasars have larger ionization cone opening angles. Similarly, brighter AGNs seem to perturb the cool ($T\sim10^4$ K) gas more strongly. We show that QSO MUSEUM now has enough statistics to study the instantaneous AGN feedback while controlling for black hole properties, which are key to constraining AGN models.

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arXiv2025

Bridging Simulations and Observations: New Insights into Galaxy Formation Simulations via Out-of-Distribution Detection and Bayesian Model Comparison

Cosmological simulations are a powerful tool to advance our understanding of galaxy formation and many simulations model key properties of real galaxies. A question that naturally arises for such simulations in light of high-quality observational data is: How close are the models to reality? Due to the high-dimensionality of the problem, many previous studies evaluate galaxy simulations using simplified summary statistics of physical properties. In this work, we combine simulation-based Bayesian model comparison with a novel misspecification detection technique to compare simulated galaxy images of 6 hydrodynamical models observations. Since cosmological simulations are computationally costly, we address the problem of low simulation budgets by first training a $k$-sparse variational autoencoder (VAE) on the abundant dataset of SDSS images. The VAE learns to extract informative latent embeddings and delineates the typical set of real images. To reveal simulation gaps, we then perform out-of-distribution detection (OOD) based on the logits of classifiers trained on the embeddings of simulated images. Finally, we perform amortized Bayesian model comparison using probabilistic classification, identifying the relatively best-performing model along with partial explanations through SHAP values.

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arXiv2025

Submillimeter galaxy overdensities around physically associated quasar pairs

A commonly employed method to detect protoclusters in the young universe is the search for overdensities of massive star forming galaxies, such as submillimeter galaxies (SMGs), around high-mass halos, including those hosting quasars. In this work, we study the Megaparsec environment surrounding nine physically associated quasar pairs between $z=2.45$ and $z=3.82$ with JCMT/SCUBA-2 observations at 450 $μ$m and 850 $μ$m covering a field of view of roughly 13.7 arcmin in diameter (or 32 Mpc$^2$ at the median redshift) for each system. We identify a total of 170 SMG candidates and 26 non-SMG and interloper candidates. A comparison of the underlying 850 $μ$m source models recovered with Monte Carlo simulations to the blank field model reveals galaxy overdensities in all fields, with a weighted average overdensity factor of $δ_{\rm cumul} = 3.4 \pm 0.3$. From this excess emission at 850 $μ$m, we calculate a star formation rate density of $1700 \pm 100$ M$_{\odot}$ yr$^{-1}$ Mpc$^{-3}$, consistent with predictions from protocluster simulations and observations. Compared to fields around single quasars, those surrounding quasar pairs have higher excess counts and more centrally peaked star formation, further highlighting the co-evolution of SMGs and quasars. We do not find preferential alignment of the SMGs with the quasar pair direction or their associated Ly$α$ nebulae, indicating that cosmic web filaments on different scales might be traced by the different directions. Overall, this work substantiates the reliability of quasar pairs to detect overdensities of massive galaxies and likely sites of protocluster formation. Future spectroscopic follow-up observations are needed to confirm membership of the SMG candidates with the physically associated quasar pairs and definitively identify the targeted fields as protoclusters.

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arXiv2024

QSO MUSEUM II: Search for extended Ly$α$ emission around eight $z \sim 3$ quasar pairs

Extended Ly$α$ emission is routinely found around single quasars (QSO) across cosmic time. However, few studies have investigated how such emission changes in fields with physically associated QSO pairs, which should reside in dense environments and are predicted to be linked through intergalactic filaments. We present VLT/MUSE snapshot observations (45 min./source) to unveil extended Ly$α$ emission on scales of the circumgalactic medium (CGM) around the largest sample of physically associated QSO pairs to date, encompassing 8 pairs (14 observed QSOs) at $z$~3 with $i$-band magnitude between 18 and 22.75. The pairs are either at close (~50-100 kpc, 5 pairs) or wide (~450-500 kpc, 3 pairs) separation with velocity differences of $Δ$v < 2000 km s$^{-1}$. We detect extended emission around 12 of the 14 targeted QSOs and investigate the luminosity, size, kinematics and morphology of these Ly$α$ nebulae. On average, they span 90 kpc and are 2.8 $\times 10^{43}$ erg s$^{-1}$ bright. Irrespective of the QSOs' projected distance, the nebulae often (~45 %) extend toward the other QSO in the pair, leading to asymmetric emission whose flux-weighted centroid is at an offset position from any QSO location. We show that large nebulae are preferentially aligned with the large-scale structure as traced by the two QSOs, and conclude that the cool gas (10$^4$ K) in the CGM traces well the direction of cosmic web filaments. Additionally, the radial profile of the Ly$α$ surface brightness around QSO pairs can be described by a power law with a shallower slope (~$-1.6$) with respect to single QSOs (~$-2$), indicative of increased CGM densities out to large radii and/or enhanced contribution from the intergalactic medium (IGM). The sample presented in this study contains excellent targets for ultra-deep observations to directly study filamentary IGM structures in emission.

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arXiv2024

HELLO project: High-$z$ Evolution of Large and Luminous Objects

We present the High-$z$ Evolution of Large and Luminous Objects (HELLO) project, a set of $\sim\!30$ high-resolution cosmological simulations aimed to study Milky Way analogues ($M_\star\sim10^{10-11}$\,\Msun) at high redshift ($z\sim [2-4]$). Based on the Numerical Investigation of a Hundred Astrophysical Objects (NIHAO), HELLO features an updated scheme for chemical enrichment and the addition of local photoionization feedback. Independently of redshift and mass, our galaxies exhibit a smooth progression along the star formation main sequence until $M_\star \sim\!10^{10.5}$, around which our sample at $z \sim 4$ remains mostly unperturbed while the most massive galaxies at $z \sim 2$ reach their peak star formation rate (SFR) and its subsequent decline, due to a mix of gas consumption and stellar feedback. While AGN feedback remains subdominant with respect to stellar feedback for energy deposition, its localised nature likely adds to the physical processes leading to declining SFRs. The phase in which a galaxy in our mass range can be found at a given redshift is set by its gas reservoir and assembly history. Finally, our galaxies are in excellent agreement with various scaling relations observed with the \textit{Hubble Space Telescope} and the \textit{James Webb Space Telescope}, and hence can be used to provide the theoretical framework to interpret current and future observations from these facilities and shed light on the transition from star-forming to quiescent galaxies.

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arXiv2023

LMC Stars and Where to Find Them: Inferring Birth Radii for External Galaxies

It is well known that stars move away from their birth location over time via radial migration. This dynamical process makes computing the correct chemical evolution, e.g., metallicity gradients, of galaxies very difficult. This dynamical process makes inferring the chemical evolution of observed galaxies from their measured abundance gradients very difficult. One way to account for radial migration is to infer stellar birth radii for individual stars. Many attempts to do so have been performed over the last years, but are limited to the Milky Way as computing the birth position of stars requires precise measurements of stellar metallicity and age for individual stars that cover large Galactic radii. Fortunately, recent and future surveys will provide numerous opportunities for inferring birth radii for external galaxies such as the Large Magellanic Cloud (LMC). In this paper, we investigate the possibility of doing so using the NIHAO cosmological zoom-in simulations. We find that it is theoretically possible to infer birth radii with a ~ 25% median uncertainty for individual stars in galaxies with i) orderliness of the orbits, $\langle v_ϕ\rangle/σ_{v} >$ 2, ii) a dark matter halo mass greater or equal to approximately the LMC mass (~ 2 x 10$^{11} M_\odot$), and iii) after the average azimuthal velocity of the stellar disk reaches ~70% of its maximum. From our analysis, we conclude that it is possible and useful to infer birth radii for the LMC and other external galaxies that satisfy the above criteria.

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arXiv2023

AGN radiation imprints on the circumgalactic medium of massive galaxies

Active Galactic Nuclei (AGN) in cosmological simulations generate explosive feedback that regulates star formation in massive galaxies, modifying the gas phase structure out to large distances. Here, we explore the direct effects that AGN radiation has on gas heating and cooling within one high-resolution $z=3$ dark matter halo as massive as a quasar host ($M_{\rm h}=$10$^{\rm 12.5}$M$_{\rm\odot}$), run without AGN feedback. We assume AGN radiation to impact the circumgalactic medium (CGM) anisotropically, within a bi-cone of angle $α$. We find that even a relatively weak AGN (black hole mass $M_{\rm\bullet}=10^{\rm 8}$M$_{\rm\odot}$ with an Eddington ratio $λ=0.1$) can significantly lower the fraction of halo gas that is catastrophically cooling compared to the case of gas photoionized only by the ultraviolet background (UVB). Varying $M_{\rm\bullet}$, $λ$ and $α$, we study their effects on observables. A 10$^{\rm 9}$M$_{\rm\odot}$ AGN with $λ=0.1$ and $α\approxeq60^{^{\rm o}}$ reproduces the average surface brightness (SB) profiles of Ly$α$, HeII and CIV, and results in a covering fraction of optically thick absorbers within observational estimates. The simulated SB$_{\rm CIV}$ profile is steeper than observed, indicating that not enough metals are pushed beyond the very inner CGM. For this combination of parameters, the CGM mass catastrophically cooling is reduced by half with respect to the UVB-only case, with roughly same mass out of hydrostatic equilibrium heating up and cooling down, hinting to the importance of self-regulation around AGNs. This study showcases how CGM observations can constrain not only the properties of the CGM itself, but also those of the AGN engine.

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arXiv2023

Circumgalactic Ly$α$ emission around submillimeter-bright galaxies with different quasar contributions

We present VLT/MUSE observations targeting the extended Lyman-$α$ (Ly$α$) emission of five high-redshift ($z\sim$3-4) submillimeter galaxies (SMGs) with increasing quasar (QSO) radiation: two SMGs, two SMGs hosting a QSO, and one SMG hosting a QSO with a SMG companion (QSO+SMG). These sources should be located in dark matter halos of comparable masses (average mass of $M_{\rm DM}\sim10^{12.2}\,{\rm M}_\odot$). We quantify the luminosity and extent of the Ly$α$ emission, together with its kinematics, and examine four Ly$α$ powering mechanisms: photoionization from QSOs/star formation, shocks by galactic/QSO outflows, gravitational cooling radiation, and Ly$α$ photons resonant scattering. We find a variety of Ly$α$ luminosities and extents, with the QSO+SMG system displaying the most extended and bright nebula, followed by the SMGs hosting a QSO, and finally the undetected circumgalactic medium (CGM) of SMGs. This diversity implies that gravitational cooling is unlikely to be the main powering mechanism. We show that photoionization from the QSO and QSO outflows can contribute to power the emission for average densities $n_{\rm H}>0.5\,$cm$^{-3}$. Moreover, the observed Ly$α$ luminosities scale with the QSO's budget of Ly$α$ photons modulo the dust content in each galaxy, highlighting a possible contribution from resonant scattering of QSO's radiation in powering the nebulae. We find larger Ly$α$ linewidths (FWHM$\gtrsim 1200\,$km$\,$s$^{-1}$) than usually reported around radio-quiet systems, pointing to large-scale outflows. A statistical survey targeting similar high-redshift massive systems with known host properties is needed to confirm our findings.

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arXiv2023

The luminosity-area relation of $z>2$ quasars' Ly$α$ nebulae

Cool ($T\sim10^4$~K) gas is commonly observed around $z>2$ quasars as traced by extended Ly$α$ emission. These large-scale nebulae are usually studied using circularly averaged surface brightness profiles, which suppress information on morphological differences. Here, we revisit the Ly$α$ nebulae around 78 $z\sim2-3$ quasars to obtain a novel estimate of their area and asymmetry using a common redshift-corrected surface-brightness threshold. We find a luminosity-area relation of the form ${{\rm log}(L_{\rm Lyα}^{\rm Neb})=a_1 log({\rm Area^{Neb})+a_0}}$. Most nebulae are symmetric and bright, the most lopsided ones being the faintest and the less extended. The Enormous Lyman-Alpha Nebulae, asymmetric due to the presence of active companions, are the exceptions to this trend. By using simulations able to reproduce $z\sim6$ quasar's nebulae, we show that the observed relation should not vary with redshift. Finally, we discuss possible mechanisms that drive the relation and future work needed to constrain them.

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arXiv2023

The impact of early massive mergers on the chemical evolution of Milky Way-like galaxies: insights from NIHAO-UHD simulations

Recent observations of the Milky Way (MW) found an unexpected steepening of the star-forming gas metallicity gradient around the time of the Gaia-Sausage-Enceladus (GSE) merger event. Here we investigate the influence of early ($t_{\mathrm{merger}}\lesssim5$ Gyr) massive ($M_{\mathrm{gas}}^{\mathrm{merger}}/M_{\mathrm{gas}}^{\mathrm{main}}(t_{\mathrm{merger}})\gtrsim10\%$) merger events such as the Gaia-Sausage Enceladus merger in the MW on the evolution of the cold gas metallicity gradient. We use the NIHAO-UHD suite of cosmological hydrodynamical simulations of MW-mass galaxies to study the frequency of massive early mergers and their detailed impact on the morphology and chemistry of the gaseous disks. We find a strong steepening of the metallicity gradient at early times for all four galaxies in our sample which is caused by a sudden increase in the cold gas disk size (up to a factor of 2) in combination with the supply of un-enriched gas ($\sim0.75$ dex lower compared to the main galaxy) by the merging dwarf galaxies. The mergers mostly affect the galaxy outskirts and lead to an increase in cold gas surface density of up to 200% outside of $\sim8$ kpc. The addition of un-enriched gas breaks the self-similar enrichment of the inter-stellar-medium and causes a dilution of the cold gas in the outskirts of the galaxies. The accreted stars and the ones formed later out of the accreted gas inhabit distinct tracks offset to lower [$α$/Fe] and [Fe/H] values compared to the main galaxy's stars. We find that such mergers can contribute significantly to the formation of a second, low-$α$ sequence as is observed in the MW.

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arXiv2023

JCMT/SCUBA-2 uncovers an excess of $850μ$m counts on megaparsec scales around high-redshift quasars. Characterization of the overdensities and their alignment with the quasars' Ly$α$ nebulae

We conducted a systematic survey of the environment of high-z quasars at submillimeter wavelengths to unveil and characterize the surrounding distribution of dusty submillimeter galaxies (SMGs). We took sensitive JCMT/SCUBA-2 observations for 3 enormous Lyman-alpha nebulae (ELANe) and 17 quasar fields in the redshift range 2 4 or detected in both bands at S/N>3. We ran Monte Carlo simulations to construct 850$μ$m number counts and unveil an excess of sources in 75% of the targeted fields. Overall, regions around ELANe and quasars are overabundant with respect to blank fields by a factor of $3.4\pm0.4$ and $2.5\pm0.2$, respectively. Therefore, the excess of SMGs is likely part of the Mpc-scale environment around these systems. By combining all fields and repeating the count analysis in radial apertures, we find a decrease in the overdensity factor from >3 within $\sim 2$ cMpc to $\sim2$ at the edge of the surveyed field ($\sim10$ cMpc), suggesting that the physical extent of the overdensities is larger than our maps. We computed preferred directions for the overdensities of SMGs from the positions of the sources and used them to orient and create stacked maps of source densities for the quasars' environment. This stacking unveils an elongated structure reminiscent of a large-scale filament with a scale width of $\approx 3$ cMpc. Finally, the directions of the overdensities are roughly aligned with the major axis of the Ly$α$ nebulae, suggesting that the latter trace, on hundreds of kpc, the central regions of the projected large-scale structure described by the SMGs on Mpc scales. Confirming member associations of the SMGs is required to further characterize their spatial and kinematic distribution around ELANe and quasars.

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arXiv2022

Milky Way-like galaxies: stellar population properties of dynamically defined disks, bulges and stellar halos

The formation of galaxies can be understood in terms of the assembly patterns of each type of galactic component. To perform this kind of analysis, is necessary to define some criteria to separate those components. Decomposition methods based on dynamical properties are more physically motivated than photometry-based ones. We use the unsupervised Gaussian Mixture model of \texttt{galactic structure finder} to extract the components of a sub-sample of galaxies with Milky Way-like masses from the EAGLE simulations. A clustering in the space of first and second order dynamical moments of all identified substructures reveals five types of galaxy components: thin and thick disks, stellar halos, bulges and spheroids. We analyse the dynamical, morphological and stellar population properties of these five component types, exploring to what extent these properties correlate with each other, and how much they depend on the total galaxy stellar and dark matter halo masses. All galaxies contain a bulge, a stellar halo and a disk. 60% of objects host two disks (thin and thick), and 68% host also a spheroid. The dynamical disk-to-total ratio does not depend on stellar mass, but the median rotational velocities of the two disks do. Thin disks are well separated in stellar ages, [Fe/H] and $α$-enhancement from the three dispersion-dominated components, while thick disks are in between. Except for thin disks, all components show correlations among their stellar population properties: older ages mean lower metallicities and larger $α$-enhancement. Finally, we quantify the weak dependence of stellar population properties on each component's dynamics.

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arXiv2021

A Multiwavelength Study of ELAN Environments (AMUSE$^2$). Mass budget, satellites spin alignment and gas infall in a massive $z\sim3$ quasar host halo

The systematic targeting of extended Ly$α$ emission around high-redshift quasars resulted in the discovery of rare and bright Enormous Ly$α$ Nebulae (ELANe) associated with multiple active galactic nuclei (AGN). We here initiate "a multiwavelength study of ELAN environments" (AMUSE$^2$) focusing on the ELAN around the $z\sim3$ quasar SDSS J1040+1020, a.k.a. the Fabulous ELAN. We report on VLT/HAWK-I, APEX/LABOCA, JCMT/SCUBA-2, SMA/850$μ$m, ALMA/CO(5-4) and 2mm observations and compare them to previously published VLT/MUSE data. The continuum and line detections enable a first estimate of the star-formation rates, dust, stellar and molecular gas masses in four objects associated with the ELAN (three AGNs and one Ly$α$ emitter), confirming that the quasar host is the most star-forming (${\rm SFR}\sim500$ M$_\odot$ yr$^{-1}$) and massive galaxy ($M_{\rm star}\sim10^{11}$ M$_{\odot}$) in the system, and thus can be assumed as central. All four embedded objects have similar molecular gas reservoirs ($M_{\rm H_2}\sim10^{10}$ M$_{\odot}$), resulting in short depletion time scales. This fact together with the estimated total dark-matter halo mass, $M_{\rm DM}=(0.8-2)\times10^{13}$ M$_{\odot}$, implies that this ELAN will evolve into a giant elliptical galaxy. Consistently, the constraint on the baryonic mass budget for the whole system indicates that the majority of baryons should reside in a massive warm-hot reservoir (up to $10^{12}$ M$_{\odot}$), needed to complete the baryons count. Additionally, we discuss signatures of gas infall on the compact objects as traced by Ly$α$ radiative transfer effects and the evidence for the alignment between the satellites' spins and their directions to the central.

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arXiv2021

The challenge of simultaneously matching the observed diversity of chemical abundance patterns in cosmological hydrodynamical simulations

With the advent of large spectroscopic surveys the amount of high quality chemo-dynamical data in the Milky Way (MW) increased tremendously. Accurately and correctly capturing and explaining the detailed features in the high-quality observational data is notoriously difficult for state-of-the-art numerical models. In order to keep up with the quantity and quality of observational datasets, improved prescriptions for galactic chemical evolution need to be incorporated into the simulations. Here we present a new, flexible, time resolved chemical enrichment model for cosmological simulations. Our model allows to easily change a number of stellar physics parameters such as the shape of the initial mass function (IMF), stellar lifetimes, chemical yields or SN Ia delay times. We implement our model into the Gasoline2 code and perform a series of cosmological simulations varying a number of key parameters, foremost evaluating different stellar yield sets for massive stars from the literature. We find that total metallicity, total iron abundance and gas phase oxygen abundance are robust predictions from different yield sets and in agreement with observational relations. On the other hand, individual element abundances, especially $α$-elements show significant differences across different yield sets and none of our models can simultaneously match constraints on the dwarf and MW mass scale. This offers a unique way of observationally constraining model parameters. For MW mass galaxies we find for most yield tables tested in this work a bimodality in the $[α$/Fe] vs. [Fe/H] plane of rather low intrinsic scatter potentially in tension with the observed abundance scatter.

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