arXiv subjects

Santiago Jiménez

Publications and source records attributed to Santiago Jiménez.

6 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

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↗

arXiv2022

On the formation of globular clusters: comparison with observations

The paper deals with the conditions required to form at least two stellar generations in globular clusters under the constraints generated by feedback from massive stars as well as radiative cooling and the metallicity of the primordial clouds. Our calculations are based on two main constraints to the star formation efficiency of the first stellar generation (1G) $ε_{1G}$. First, $ε_{1G}$ is restricted to warrant that stellar winds and supernovae do not disrupt the leftover gas out of which a second generation (2G) would form. Second, $ε_{1G}$ is also limited such that the metallicity enhancement caused by trapped supernovae is, in agreement with the observations, not larger than $\sim$ 0.1 dex. Several central parameters define the globular clusters end result: the mass and radius of the primordial clouds, their metallicity and $ε_{1G}$. The parameter space composed by models which fulfilled all constraints, is here shown to coincide remarkably well with the scattered observed anti-correlation between the fraction of first generation stars ($f_{\textrm{1G}}$) and total cluster mass. Our models also discern, in agreement with the data, between single and multiple population clusters in a metallicity versus mass (or radius) plane. Hence, our results suggest that the presence of multiple stellar populations is closely linked to the ability of proto-globular clusters to retain a fraction of leftover gas.

astro-ph.GA↗

arXiv2021

SNe and their impact during the early evolution of Type I Globular Clusters

The iron composition of globular clusters (GCs) is homogeneous in all but a few massive clusters, despite the presence of multiple stellar populations. Hence, most if not all the supernovae (SN) ejecta was not used to form stars. Here by means of semi-analytic and numerical studies we address this issue considering both stellar winds and supernovae feedback during the early evolution of proto-globular clusters. We calculate the ability of stellar winds to form a global wind that removes the gas left over from star formation. The innermost radius from which such a global wind can be formed, the superwind radius $R_{SW}$, is a function of the cloud parameters and the star formation efficiency. In the case of complete gas expulsion ($R_{\textrm{SW}}=0$), the SN ejecta merge with shock-heated winds and exit the cluster. On the other hand, when $R_{\textrm{SW}}>0$, supernova remnants (SNRs) become pressure-confined if evolving within a critical radius $R_{\textrm{blow}}$, and mix their products with the residual gas. However, outside of this central zone the SNRs experience blowout. In such cases, the thermalized ejecta escapes the cluster, making the SN products unavailable for the formation of new stars. We estimated the metallicity enhancement ($Δ\textrm{[Fe/H]}$) of the leftover gas and discuss the conditions required to produce secondary stellar populations with $Δ\textrm{[Fe/H]}$ in the range observed in the majority of GCs.

astro-ph.GA↗