arXiv subjects

Sergio Martínez-González

Publications and source records attributed to Sergio Martínez-González.

13 recordsLinked to original sources

arXiv2026

X-rays from shock-heated gas in recurrent-nova remnants: Nested nova shells in a structured circumstellar medium

Recurrent symbiotic novae such as RS Oph show extended X-ray emission associated with the interaction of nova ejecta with the circumstellar environment. We investigate how repeated eruptions over more than a century structure the circumstellar medium and govern the long-term X-ray evolution of a symbiotic recurrent nova. We perform three-dimensional hydrodynamical simulations for a fiducial nine-eruption sequence spanning 130 years, modeling each nova as a supersonic bipolar shell expanding into a wind-shaped circumstellar medium. We post-process the resulting density and temperature distributions to compute X-ray emission in the 0.5-2.0 and 2.0-10.0 keV bands. The eruption sequence excavates a bipolar cavity bounded by nested shells. Soft X-rays trace dense compressed interfaces, whereas hard X-rays arise from the hottest shocked gas, including shell rims and the excavated nova-remnant interior. As the remnant expands, the soft-band emission shows a gradual long-term decline associated with the decreasing emission measure. The hard band evolves episodically, with individual eruptions imprinting distinct flares whose timing and relative strength change as the shell system grows. The extended X-ray morphology becomes progressively smoother and more volume-filling as density contrasts between successive shells are reduced. Our simulations identify extended shell-shock emission as a natural consequence of nested-shell evolution in recurrent novae. Remnant expansion regulates the slow fading of the soft component, and renewed ejecta-shell encounters drive hard-band variability on decade-long timescales. For a fiducial recurrent nova, the predicted diffuse soft X-ray luminosities are broadly consistent with the order of magnitude inferred for RS Oph, indicating that shock-heated gas can contribute appreciably to the observed X-ray environment.

astro-ph.HE↗

arXiv2026

The first dusty galaxies across $6 \lesssim z \lesssim 14$: Blue monsters, red monsters, and the bimodality of dust content in early galaxies

JWST has revealed galaxies at $z>10$ with extremely blue UV-continuum slopes approaching $β_{\rm UV}\lesssim-2.4$, and low inferred dust contents. At similar redshifts, JWST and ALMA reveal dusty massive systems reaching $β_{\rm UV}\gtrsim-1$. We aim to explain blue monsters and red monsters at $z\gtrsim10$ as different outcomes of supernova dust retention in clustered star-forming systems and connect this bimodality to dusty massive galaxies at $z\simeq6$--7. We model dust removal in a cluster-dominated regime through cloud-scale mechanical blowout followed by breakout from stratified high-redshift disks. The shock-processed dust mass retained in the UV-attenuating layer is converted into a UV-continuum slope using absorption opacities derived from 3D hydrodynamical simulations of clustered supernovae in porous molecular clouds. In compact, gas-rich galaxies, efficient cloud blowout and disk breakout reduce the retained dust fraction to blue-monster levels, yielding $β_{\rm UV}\lesssim-2.4$. Larger stellar masses increase the retained dust column and produce red-monster-like systems with $β_{\rm UV}\gtrsim-1.5$, reaching $β_{\rm UV}\simeq-0.5$ when radiative losses weaken large-scale driving. The transition depends on whether clustered-supernova ejecta cross both the natal cloud and the galactic gas layer. Supernova dust production, shock processing, radiative losses, and mechanical venting can jointly explain UV-bright dust-poor galaxies and red dusty massive systems across $6\lesssim z\lesssim14$.

astro-ph.GA↗

arXiv2025

On the missing dust of super-early galaxies: Supernova blowout and gas-dust venting in Blue Monsters

A subset of very young, super-early galaxies at $z\gtrsim10$, often termed Blue Monsters, shows extremely blue UV continua and faint far-IR emission, which could imply much less dust than expected from standard enrichment scenarios. We seek to understand the possible reason behind the apparent absence of dust in the Blue Monsters. We show how clustered supernovae drive mechanical blowout in stratified, self-gravitating clouds by combining full 3-D hydrodynamical dust-survival yields with 3-D thin-shell scalings, and we predict the retained dust-to-stellar mass ratio at the cluster scale and the corresponding galaxy-integrated value. We take the net dust yield per unit stellar mass from existing 3-D hydrodynamical studies of young stellar clusters with sequential supernovae, and we set the blowout radius as a function of gas concentration using established 3-D thin-shell scalings. Assuming gas-dust coupling across the blowout boundary, the retained dust-to-stellar ratio accounts for the fraction of supernovae that remain confined versus those that vent mechanically. Across typical cluster masses, sizes, and cloud-scale star formation efficiencies, mechanical venting removes a large share of gas and dust. The retained dust-to-stellar mass ratio is lowered by about half to two orders of magnitude relative to the supernova net dust yield. The outcome depends mainly on gas concentration and only weakly on metallicity, so it remains effective at low $Z$. After weighting by a Schechter cluster mass function and a Weibull core-radius distribution, the galaxy-integrated value falls in the same range inferred for spectroscopically confirmed Blue Monsters. Thus, mechanical venting at the cluster scale can account for the very low dust fractions inferred for Blue Monsters without requiring extreme in situ destruction and without fine-tuning.

astro-ph.GA↗

arXiv2025

Dusty Clump Survival in Supernova Ejecta: Dust-Mediated Growth vs. Crushing by the Reverse Shock

Understanding the interaction of dense, cold ejecta clumps with a fast reverse shock, an instance of the "cloud-crushing" problem, is essential to assess whether core-collapse supernovae act as net dust factories or net dust destroyers. This work assesses whether dusty ejecta clumps are destroyed by the reverse shock or instead cool, condense, and grow in mass under realistic supernova-remnant conditions. Cloud-crushing timescales are computed and compared to radiative cooling timescales, including both gas-phase cooling and dust-induced cooling, for a large grid of clump densities, dust-to-gas mass ratios, and shock velocities. When the dust-to-gas mass ratio exceeds $10^{-3}$, gas-grain collisions become efficient enough that the cooling timescale $t_{\rm cool}$ falls below the cloud-crushing timescale $t_{\rm cc}$ over a broad span of clump densities and shock velocities, enabling dusty clumps to survive even fast reverse shocks. For example, at clump densities $\geq 2 \times 10^{4}$ cm$^{-3}$, dust-to-gas mass ratios $\sim 10^{-2}$, and shock velocities up to $2000$ km s$^{-1}$, enhanced gas-grain cooling drives the system into a regime where dusty clumps can gain additional cold mass and increase their dust masses. Strong radiative cooling can shield dust-rich clumps in supernova remnants, enabling a significant fraction of ejecta dust to be injected into the interstellar medium. These results mirror the "growth" regime found in studies of circumgalactic clouds and rapidly cooling shocked stellar winds, implying a larger dust survival in supernova remnants. Indeed, the dusty globules seen in the Crab Nebula occupy the predicted survival regime across a wide range of physical parameters.

astro-ph.GA↗

arXiv2025

Mechanical Torque Disruption of Dust Grains Induced by Supernova Shock Waves

The feedback from massive stars drives the evolution of interstellar dust grains by altering their physical properties via a number of radiative and mechanical processes. Through these interactions, interstellar grains can achieve high rotational velocities due to unbalanced torques, potentially leading to their disruption. Mechanical torque disruption occurs when gas-grain collisions, induced by the passage of shocks, spin grains to critical rotational velocities. This study aims to investigate the effects of stochastic mechanical torque disruption on both pre-existent and supernova-condensed dust grains located within wind-blown bubbles. The impact of mechanical torque disruption on supernova-condensed dust and dust grains in wind-blown bubbles is investigated through post-processing of three-dimensional hydrodynamical simulation outputs. The associated timescale is then compared to those of kinetic sputtering and grain shattering. Before the supernova explosion, dust grain disruption timescales within wind-driven bubbles are on the order of millions of years due to the low-density environment. The timescales for mechanical torque disruption (METD) are longer than those for kinetic sputtering and comparable to those of grain shattering, primarily due the high grain drift velocities typical of these regions.

astro-ph.GA↗

arXiv2025

The bright, dusty aftermath of giant eruptions & H-rich supernovae. Late interaction of supernova shocks & dusty circumstellar shells

The late-stage evolution of massive stars is marked by intense instability as they approach core-collapse. During these phases, giant stellar eruptions lead to exceptionally high mass-loss rates, forming significant amounts of dust. However, the survival of these dust grains is challenged by the powerful shock waves generated when the progenitor explodes as a supernova (SN). We explore the impact of hydrogen-rich SN explosions from 45, 50, and 60 M$_\odot$ progenitors on dust formed after these eruptions, focusing on interactions with circumstellar shells occurring from a few years to centuries after the event. Using 3D hydrodynamical simulations, we track the evolution of dust particles in a scenario that includes the progenitor's stellar wind, a giant eruption, and the subsequent SN explosion, following the mass budgets predicted by stellar evolution models. For a standard SN ejecta mass of 10 M$_\odot$ and kinetic energy of $10^{51}$ erg, only 25% of the dust mass survives 250 years post-explosion in a spherical circumstellar medium (CSM), while merely 2% remains a century after the explosion in a bipolar CSM. If the SN follows the eruption within a dozen years, 75% of the dust survives for a standard explosion, dropping to 20% for more massive ejecta (15-20 M$_\odot$) with kinetic energy of $5 \times 10^{51}$ erg. The geometry of the CSM and the early transition of the SN remnant into a radiative phase significantly influence dust survival. As the shock wave weakens and efficiently converts kinetic energy into thermal radiation (up to half of the injected kinetic energy) the likelihood of dust survival increases, affecting not only pre-existing dust in the CSM but also SN-condensed dust and ambient interstellar dust. Contrary to expectations, a larger fraction of the dust mass can survive if the SN occurs only a few years after the eruption.

astro-ph.SR↗

arXiv2023

Simulations of pre-supernova feedback in spherical clouds

We present a one-dimensional radiation-hydrodynamic model of a spherically symmetric cloud evolving under the influence of the self-gravity and the feedback from a star cluster forming in its centre. On one hand, the model is simple due to its 1D geometry, on the other hand, the feedback includes the ionising radiation, stellar winds and the radiation pressure acting on gas and dust. The star cluster is formed from the gas flowing into the cloud centre and the feedback parameters are determined from stellar evolution models and the cluster star forming history. The model is compared to the semi-analytic code WARPFIELD implementing similar physical processes and exploring the scenario that the young cluster R136 in the Large Magellanic Cloud was formed due to re-collapse of the shell formed by the previous generation star cluster. A good qualitative agreement is found, however, $3 - 4$ times higher stellar mass is needed to disrupt the cloud in our model, because it takes into account (contrary to WARPFIELD) self-gravity of the cloud surrounding the shell. We use the model to explore star formation in clouds with different mass, radius and density profile measuring their star formation efficiency (SFE), i.e. the fraction of the cloud mass converted to stars. We found that SFE is a function of a single parameter, $\mathrm{log(SFE)} \propto -n_{hm}^{-0.46}$, with $n_{hm}$ being the cloud mean particle density within its half-mass radius. Furthermore, we found that the feedback efficiency, i.e. a fraction of the feedback energy retained by gas, has a nearly constant value $\sim 10^{-3}$.

astro-ph.GA↗

arXiv2022

Dust Grain Growth & Dusty Supernovae in Low-Metallicity Molecular Clouds

We present 3-D hydrodynamical models of the evolution of superbubbles powered by stellar winds and supernovae from young coeval massive star clusters within low metallicity ($Z = 0.02$Z$_{\odot}$), clumpy molecular clouds. We explore the initial stages of the superbubble evolution, including the occurrence of pair-instability and core-collapse supernovae. Our aim is to study the occurrence of dust grain growth within orbiting dusty clumps, and in the superbubble's swept-up supershell. We also aim to address the survival of dust grains produced by sequential supernovae. The model accounts for the star cluster gravitational potential and self-gravity of the parent cloud. It also considers radiative cooling (including that induced by dust) and a state-of-the-art population synthesis model for the coeval cluster. As shown before, a superbubble embedded into a clumpy medium becomes highly distorted, expanding mostly due to the hot gas streaming through low density channels. Our results indicate that in the case of massive ($\sim10^7$M$_{\odot}$) molecular clouds, hosting a super star cluster ($\sim5.6\times10^5$M$_{\odot}$), grain growth increments the dust mass at a rate $\sim4.8\times10^{-5}$M$_{\odot}$ yr$^{-1}$ during the first $2.5$Myr of the superbubble's evolution, while the net contribution of pair-instability and core-collapse supernovae to the superbubble's dust budget is $\sim1200$M$_{\odot} (M_{SC}/5.6\times10^{5}$M$_{\odot})$, where $M_{SC}$ is the stellar mass of the starburst. Therefore, dust grain growth and dust injection by supernovae lead to create, without invoking a top-heavy initial mass function, massive amounts of dust within low-metallicity star-forming molecular clouds, in accordance with the large dust mass present in galaxies soon after the onset of cosmic reionization.

astro-ph.GA↗

arXiv2022

X-ray emission from star cluster winds in starburst galaxies

Inspired by the excess soft X-ray emission recently detected in Green Pea galaxies, we model the soft X-ray emission (0.5 - 2.0 keV) of hot gas from star cluster winds. By combining individual star clusters, we estimate the soft X-ray emission expected from the typically unresolved diffuse hot gas in starburst galaxies, devoid of competing emission from e.g., AGN or other unresolved point sources. We use stellar models of sub-solar metallicities (0.02 $Z_{\odot}$ and 0.4 $Z_{\odot}$), and take into account supernova explosions for massive stars. For lower metallicities, we find that stellar winds do not contribute significantly ($\lesssim 3$ % of the mechanical energy) to the observed soft X-ray emission of normal star forming galaxies. For higher metallicities and possibly also for larger proportions of massive star clusters in the simulated starburst galaxies, we reproduce well the observed correlation between star formation rate and X-ray luminosity previously reported in the literature. However, we find that no combination of model assumptions is capable of reproducing the substantial soft X-ray emission observed from Green Pea galaxies, indicating that other emission mechanisms (i.e. unusually large quantities of High-/Low-Mass X-ray Binaries, Ultra-Luminous X-ray sources, a modified initial mass function, Intermediate-Mass Black Holes, or AGN) are more likely to be responsible for the X-ray excess.

astro-ph.GA↗

arXiv2021

Dust Grain Growth at High Redshift: Starburst-driven CMB-Dark Supershells

We present a novel scenario for the growth of dust grains in galaxies at high-redshift ($z\sim 6$). In our model, the mechanical feedback from massive star clusters evolving within high-density pre-enriched media allows to pile-up a large amount of matter into massive supershells. If the gas metallicity ($\geq$ Z$_{\odot}$), number density ($\geq 10^6$ cm$^{-3}$) and dust-to-gas mass ratio ($\sim 1/150 \times Z$) within the supershell are sufficiently large, such supershells may become optically thick to the starlight emerging from their host star clusters and even to radiation from the Cosmic Microwave Background (CMB). Based on semi-analytic models, we argue that this mechanism, occurring in the case of massive ($\geq 10^7$ M$_{\odot}$) molecular clouds hosting $\geq 10^6$ M$_{\odot}$ star clusters, allows a large mass of gas and dust to acquire a temperature below that of the CMB, whereupon dust grain growth may occur with ease. In galaxies with total stellar mass $M_{*}$, grain growth within supershells may increase the dust mass by $\sim 10^6$ M$_{\odot}$ $(M_{*}/10^{8}$ M$_{\odot}$).

astro-ph.GA↗

arXiv2019

Dusty supernovae running the thermodynamics of the matter reinserted within young and massive super stellar clusters

Following the observational and theoretical evidence that points at core collapse supernovae as major producers of dust, here we calculate the hydrodynamics of the matter reinserted within young and massive super stellar clusters under the assumption of gas and dust radiative cooling. The large supernova rate expected in massive clusters allows for a continuous replenishment of dust immersed in the high temperature thermalized reinserted matter and warrants a stationary presence of dust within the cluster volume during the type II supernova era. We first show that such a balance determines the range of dust to gas mass ratio and this the dust cooling law. We then search for the critical line that separates stationary cluster winds from the bimodal cases in the cluster mechanical luminosity (or cluster mass) vs cluster size parameter space. In the latter, strong radiative cooling reduces considerably the cluster wind mechanical energy output and affects particularly the cluster central regions, leading to frequent thermal instabilities that diminish the pressure and inhibit the exit of the reinserted matter. Instead matter accumulates there and is expected to eventually lead to gravitational instabilities and to further stellar formation with the matter reinserted by former massive stars. The main outcome of the calculations is that the critical line is almost two orders of magnitude or more, depending on the assumed value of the adiabatic wind terminal speed, lower than when only gas radiative cooling is applied. And thus, many massive clusters are predicted to enter the bimodal regime.

astro-ph.GA↗

arXiv2019

Supernovae within Pre-existing Wind-Blown Bubbles: Dust Injection vs. Ambient Dust Destruction

By means of 3-D hydrodynamical simulations, here we evaluate the impact that supernova explosions occurring within wind-driven bubbles have on the survival or destruction of dust grains. We consider both, the dust generated within the ejecta and the dust initially present in the ambient gas and later locked-up in the surrounding wind-driven shell. The collision of the supernova blast wave with the wind-driven shell leads to a transmitted shock that moves into the shell and a reflected shock into the ejecta. The transmitted shock is capable of destroying large amounts of the dust locked in the shell, but only if the mass of the wind-driven shell is small, less than a few tens the ejected mass. Conversely, massive wind-driven shells, with several times the ejected mass, lead upon the interaction to strong radiative cooling, which inhibits the Sedov-Taylor phase and weakens the transmitted shock, making it unable to traverse the wind-driven shell. In such a case, the destruction/disruption of the ambient dust is largely inhibited. On the other hand, the SNRs grow rapidly in the very tenuous region excavated by the stellar winds, and thus a large fraction of the dust generated within the ejecta is not efficiently destroyed by the supernova reverse shock, nor by the reflected shock. Our calculations favor a scenario in which core-collapse supernovae within sufficiently massive wind-driven shells supply more dust to the ISM than what they are able to destroy.

astro-ph.GA↗

arXiv2018

Pyroclastic Blowout: Dust Survival in Isolated versus Clustered Supernovae

Following the current debate on the fate of SN-condensed dust grains, here we explore by means of three-dimensional hydrodynamical simulations the interaction of dusty supernova remnants (SNRs) with the shocked winds of neighboring massive stars within young massive stellar clusters (SSCs). As a comparison, we have also explored the evolution of supernova remnants in the diffuse ISM with constant density. Since the hydrodynamics of SNRs is intimately related to the properties of their immediate environment, the lifecycle of dust grains in SNRs within SSCs is radically different from that in the diffuse ISM. Moreover, off-centered SNRs evolving in the steep density gradient established due to a star cluster wind experience a blowout phase: shell fragmentation due to protruding Rayleigh-Taylor instabilities and the venting of SN ejecta. Our main finding is that clustered SN explosions will cause a net increase in the amount of dust in the surroundings of young massive stellar clusters. Our analysis considers the multiple dust processing resulting from the passage of the SN reverse shock, including its reflection at the SNR's center, the injection of shocked stellar winds within the respective remnant's volume and the effect of secondary forward shocks produced in sequential SN explosions. In the simulations, we have on-the-fly calculated the rates of thermal sputtering and dust-induced radiative cooling provided an initial distribution of grain sizes and dust content. Fast-moving elongated dusty SN ejecta resemble mushroom clouds violently ascending in a stratified atmosphere after volcanic super-eruptions, where the pyroclasts carried by the clouds are wind-driven and eventually accumulate into the vast surroundings.

astro-ph.GA↗