arXiv subjects

María José Colmenares

Publications and source records attributed to María José Colmenares.

10 recordsLinked to original sources

arXiv2026

The JDISC Survey: Inner Disk Chemistry of Class I/FS Disks and Tentative Evidence for Early Pebble Drift

We present the first chemical survey of Class I and Flat-Spectrum (I/FS) disks using JWST MIRI/MRS, targeting sixteen sources in the Ophiuchus star-forming region. Through empirical line luminosity measurements and multi-component slab modeling, we characterize the molecular reservoir of these young systems and compare them to twelve Class II disks of similar stellar mass. Water, HCN, C$_2$H$_2$, and CO$_2$ are frequently detected in I/FS sources with inclinations $i < 70^{\circ}$, whereas edge-on systems show significantly suppressed emission. Compared to Class II disks, I/FS sources show suggestive---though not yet statistically significant---evidence for elevated cold water ($\sim$200\,K) mass and lower CO$_2$ excitation temperatures. Statistical analyses identify accretion luminosity as the primary correlate of molecular mass across both evolutionary stages. Once this dependence is removed, cold water and CO$_2$ masses anti-correlate with mm-dust disk radius, while hot water remains insensitive to disk size. These patterns are qualitatively consistent with pebble drift models that predict early water enrichment followed by delayed CO$_2$ delivery, suggesting an evolutionary progression from molecular-poor Class 0 sources, through water-rich Class I/FS disks, to Class II disks with reduced cold water excess. This work provides an initial evolutionary framework for disk chemistry that requires larger, multi-region samples to confirm.

astro-ph.EP↗

arXiv2026

Chemical Divergence and Water Depletion: Gas Properties of Evolved Upper Scorpius Disks Revealed by JWST/MIRI

Tracing the chemical evolution of protoplanetary disks over time requires observations of disks at different ages. However, most JWST/MIRI surveys published to date have targeted younger ($\sim$1-3 Myr) rather than older systems. We present the results of a JWST/MIRI MRS survey of the inner regions of 10 protoplanetary disks (ages $\sim$2-6 Myr, spectral types M0-M4.5) in the Upper Scorpius region previously characterized by the ALMA AGE-PRO large program. Using MCMC slab modeling, we fit to a wide variety of detected molecules, including H$_2$O, CO, C$_2$H$_2$, $^{13}$CCH$_2$, HCN, HC$_3$N, CO$_2$, $^{13}$CO$_2$, C$_2$H$_6$, C$_4$H$_2$, and OH, as well as C$_6$H$_6$, CH$_3$, and H$_2$ visually. We classify each disk along two independent axes-a Water Classification based on H$_2$O line luminosity (Water-Rich, Water-Poor, or Water-Absent) and a Chemotype based on the dominant non-water chemistry (Organic-Rich, CO$_2$-Dominated, or Molecule-Absent)-and find an unexpectedly high diversity of distinct chemical compositions within our population. We leverage the heterogeneity of detected molecules in our sample to present new characteristic "diagnostic" wavelength regions for most species. We find that carbon-based molecules consistently exhibit markedly lower excitation temperatures ($\lesssim$300 K) compared to younger ($\sim$1-3 Myr) star-forming regions ($\sim$600-1000 K), hinting at relatively colder molecular reservoirs. We also determine that Upper Scorpius disks show systematically lower water luminosities by factors of 10-1000. In particular, disks with strong carbon-based molecular features but no observed H$_2$O defy expectations of an inner-disk dust cavity or a low ($\lesssim3$) $R_{\rm gas}/R_{\rm dust}$ ratio, instead suggesting that the presence of a strong outer-disk dust trap largely controls the chemical outcome of the terrestrial planet-forming region.

astro-ph.EP↗

arXiv2026

JWST-DECO: The Impact of Accretion on Mid-Infrared Observable Water in Planet-forming Disks

The inner few au of a protoplanetary disk hosts the majority of observed exoplanets and is the primary planet-forming zone of the disk. The mid-IR spectra of disks, with its rich forest of water lines, provides key insights into the composition of forming planets. One of the strongest trends seen with data from Spitzer and now JWST is a correlation between the increase in water line flux and accretion luminosity of a system. We set out to reproduce and understand this trend by adding an accretion module to the thermo-chemical code DALI, and explore how viscous accretion heating and the addition of accretion luminosity impacts the 2D temperature structure and the observable water reservoir. We reproduce the trend that the observed water mass increases with accretion rate, with hot, warm, and cool water being more to less strongly correlated, respectively. Our model suggests that these trends are due to an increased emitting area with accretion rate, with some of the cool and warm population becoming hidden underneath an optically thick dust surface and being constrained to a smaller disk volume. This trend is driven by the accretion-related increase in central luminosity, while viscous heating centralized to the midplane has no impact on observed water mass.

astro-ph.EP↗

arXiv2026

JWST/MIRI Hydrocarbon and Water Absorption in the Wind of a Young Disk: Signatures of Pebble Drift and Carbon Grain Sublimation

We present JWST/MIRI-MRS observations of ISO-Oph 37, a highly inclined flat-spectrum ($\lesssim$1 Myr old) source, to investigate the chemical composition and dynamical origin of its inner-disk gas. The spectrum reveals a rich combination of molecular emission and absorption: H$_2$O, CO, and OH are detected in emission, while strong absorption is observed from CO, H$_2$O, CO$_2$, HCN, C$_2$H$_2$, and CH$_4$, with no detectable ice absorption features. LTE slab modeling of the absorption yields excitation temperatures of $T_{\rm ex}\sim400-600$ K and column densities of $\log N/{\rm cm}^{2}\sim16-19$, characteristic of warm gas located within the inner few au. The absorption lines are significantly blueshifted relative to the systemic velocity, with mid-IR lines exhibiting larger shifts than near-IR CO absorption. This velocity structure points to a velocity- and temperature-stratified molecular disk wind. In this framework, the absorption directly samples disk material lifted from the inner disk surface, preserving the chemical imprint of the wind-launching region. Along the line of sight, ISO-Oph 37 is unusually hydrocarbon-rich compared to other known absorption systems (GV Tau N and IRS 46), exhibiting high (C$_2$H$_2$+CH$_4$)/HCN, (C$_2$H$_2$+CH$_4$)/CO and H$_2$O/CO column density ratios, while the CO and HCN columns remain broadly typical. We find that these molecular ratios are best explained by enhancement of both hydrocarbons and water, driven by inward drift and sublimation of icy pebbles and by thermal processing of carbonaceous grains at the soot line. ISO-Oph 37 thus demonstrates that carbon-rich inner-disk chemistry can be established early in disk evolution and that it can be directly probed through molecular absorption in disk winds.

astro-ph.EP↗

arXiv2026

Understanding Balmer Decrements in T Tauri stars in terms of Multiflow Magnetospheric Accretion

Magnetospheric accretion is the paradigm for accretion in Classical T-Tauri Stars (CTTS). However, the standard, one-flow magnetospheric accretion model fails to replicate important characteristics such as the observed Balmer decrements. We address this limitation by adopting a model with two axisymmetric magnetospheric accretion flows of different accretion rates and geometries. We calculate the fluxes of the hydrogen $H_α$, $H_β$, and $H_γ$ lines of each flow with the magnetospheric accretion model and use Bayesian statistics to fit the Balmer line fluxes of 139 CTTS in the Orion OB1b subassociation, and in the Upper Scorpius, Lupus and Chamaeleon I star-forming regions. We find that the Balmer decrements and line fluxes can be fitted by two distinct but coexisting flows: a compact, high accretion rate flow, close to the star and narrow (mean inner radius $R_i \sim 2.9 R_*$ and mean width $ΔR \sim 0.7 R_*$), covering a few percent of the emitting area, and a more spread out flow, thicker ($ΔR \sim 1.2 R_*$), and larger ($R_i \sim 3.7 R_*$), with lower accretion rate, encompassing the rest of the emitting area. The two-flow model can also reproduce the empirical correlation between the luminosity in $H_α$ and the accretion luminosity. Overall, our findings suggest that a multicolumn approach provides a more accurate representation of the observed Balmer line emission, in agreement with results of numerical simulations.

astro-ph.SR↗

arXiv2026

Fading into darkness: A weak mass ejection and low-efficiency fallback accompanying black hole formation in M31-2014-DS1

Stellar-mass black holes (BHs) can form from the near-complete collapse of massive stars, causing them to abruptly disappear. The star M31-2014-DS1 in the Andromeda galaxy was reported to exhibit such a disappearance between 2014 and 2022, with properties consistent with the failed explosion of a $\approx 12 - 13$ M$_\odot$ yellow supergiant leading to the formation of a $\approx 5$ M$_\odot$ BH. We present mid-infrared (MIR) observations of the remnant obtained with the James Webb Space Telescope (JWST) and X-ray observations from the Chandra X-ray Observatory in 2024. The JWST MIRI/NIRSpec data reveal an extremely red source, showing strong blueshifted absorption from molecular gas (CO, CO$_2$, H$_2$O, SO$_2$) and deep silicate dust features. Modeling the dust continuum confirms continued bolometric fading of the central source to $\log(L/L_\odot)\approx3.88$ ($\approx7-8$% of the progenitor luminosity), surrounded by a dust shell spanning $\approx40-200$ au. Modeling of the molecular gas indicates $\sim 0.1$ M$_\odot$ of gas expanding at $\approx 100$ km s$^{-1}$ near the inner edge of the dust shell. No X-ray source is detected down to a luminosity limit of $L_X\lesssim1.5\times10^{35}$ erg s$^{-1}$. We show that the panchromatic observations are explained by (i) a low-energy ($\approx10^{46}$ erg) ejection of the outer H-rich progenitor envelope and (ii) a fading central BH powered by inefficient ($\sim0.1$% in mass) accretion of loosely bound fallback material. The analysis robustly establishes the bolometric fading of M31-2014-DS1 and provides the first cohesive insights into BH formation via low-energy explosions and long-term fallback.

astro-ph.SR↗

arXiv2025

Cosmic cascades: How disk substructure regulates the flow of water to inner planetary systems

The influx of icy pebbles to the inner regions of protoplanetary disks constitutes a fundamental ingredient in most planet formation theories. The observational determination of the magnitude of this pebble flux and its dependence on disk substructure (disk gaps as pebble traps) would be a significant step forward. In this work we analyze a sample of 21 T Tauri disks (with ages $\approx 0.5{-}2\mathrm{~Myr}$) using JWST/MIRI spectra homogeneously reduced with the JDISCS pipeline and high-angular-resolution ALMA continuum data. We find that the 1500/6000 K water line flux ratio measured with JWST - a tracer of cold water vapor and pebble drift near the snowline - correlates with the radial location of the innermost dust gap in ALMA continuum observations (ranging from 8.7 to 69 au), confirming predictions from recent models that study connections between the inner and outer disk reservoirs. We develop a population synthesis exploration of pebble drift in gapped disks and find a good match to the observed trend for early and relatively effective gaps, while scenarios where pebble drift happens quickly, gaps are very leaky, or where gaps form late are disfavored on a population level. Inferred snowline pebble mass fluxes (ranging between $10^{-6}$ and $10^{-3}~M_\oplus/\mathrm{yr}$ depending on gap position) are comparable to fluxes used in pebble accretion studies and those proposed for the inner Solar System, while system-to-system variations suggest differences in the emerging planetary system architectures and water budgets.

astro-ph.EP↗

arXiv2025

The JDISC Survey: Linking the Physics and Chemistry of Inner and Outer Protoplanetary Disk Zones

Mid-infrared spectroscopy of protoplanetary disks provides a chemical inventory of gas within a few au, where planets are readily detected around older stars. With the JWST Disk Infrared Spectral Chemistry Survey (JDISCS), we explore demographic trends among 31 disks observed with MIRI (MRS) and with previous ALMA millimeter continuum imaging at high angular resolution (5-10 au). With these S/N $\sim$200-450 spectra, we report emission from H$_2$O, OH, CO, C$_2$H$_2$, HCN, CO$_2$, [Ne II], [Ne III], and [Ar II]. Emission from H$_2$O, OH and CO is nearly ubiquitous for low-mass stars, and detection rates of all molecules are higher than for similar disks observed with Spitzer-IRS. Slab model fits to the molecular emission lines demonstrate that emission from C$_2$H$_2$, HCN, and possibly CO$_2$ is optically thin; thus since column densities and emitting radii are degenerate, observations are actually sensitive to the total molecular mass. C$_2$H$_2$ and HCN emission also typically originate in a hotter region ($920^{+70}_{-130}$, $820^{+70}_{-130}$ K, respectively) than CO$_2$ ($600^{+200}_{-160}$ K). The HCN to cold H$_2$O luminosity ratios are generally smaller in smooth disks, consistent with more efficient water delivery via icy pebbles in the absence of large dust substructures. The molecular emission line luminosities are also correlated with mass accretion rates and infrared spectral indices, similar to trends reported from Spitzer-IRS surveys. This work demonstrates the power of combining multi-wavelength observations to explore inner disk chemistry as a function of outer disk and stellar properties, which will continue to grow as the sample of observed Class II systems expands in the coming JWST observation cycles.

astro-ph.SR↗

arXiv2024

The First JWST View of a 30-Myr-old Protoplanetary Disk Reveals a Late-stage Carbon-rich Phase

We present a JWST MIRI/MRS spectrum of the inner disk of WISE J044634.16$-$262756.1B (hereafter J0446B), an old ($\sim$34 Myr) M4.5 star but with hints of ongoing accretion. The spectrum is molecule-rich and dominated by hydrocarbons. We detect 14 molecular species (H$_2$, CH$_3$, CH$_4$, C$_2$H$_2$, $^{13}$CCH$_2$, C$_2$H$_4$, C$_2$H$_6$, C$_3$H$_4$, C$_4$H$_2$, C$_6$H$_6$, HCN, HC$_3$N, CO$_2$ and $^{13}$CO$_2$) and 2 atomic lines ([Ne II] and [Ar II]), all observed for the first time in a disk at this age. The detection of spatially unresolved H$_2$ and Ne gas strongly supports that J0446B hosts a long-lived primordial disk, rather than a debris disk. The marginal H$_2$O detection and the high C$_2$H$_2$/CO$_2$ column density ratio indicate that the inner disk of J0446B has a very carbon-rich chemistry, with a gas-phase C/O ratio $\gtrsim$2, consistent with what have been found in most primordial disks around similarly low-mass stars. In the absence of significant outer disk dust substructures, inner disks are expected to first become water-rich due to the rapid inward drift of icy pebbles, and evolve into carbon-rich as outer disk gas flows inward on longer timescales. The faint millimeter emission in such low-mass star disks implies that they may have depleted their outer icy pebble reservoir early and already passed the water-rich phase. Models with pebble drift and volatile transport suggest that maintaining a carbon-rich chemistry for tens of Myr likely requires a slowly evolving disk with $α-$viscosity $\lesssim10^{-4}$. This study represents the first detailed characterization of disk gas at $\sim$30 Myr, strongly motivating further studies into the final stages of disk evolution.

astro-ph.EP↗

arXiv2023

The Ca II lines as tracers of disk structure in T Tauri Stars: The Chamaeleon I region

We present a study of the Ca II K and IR-triplet lines in a sample of Classical T Tauri stars in the Chamaeleon I star-forming region. We study X-shooter spectra of the stars in the sample and find that in some of these stars the Ca II lines are much weaker than expected from their H line fluxes and mass accretion rate. Since the Ca II K lines have characteristic magnetospheric accretion line profiles and the magnetospheric flows feed directly from the inner disk, we interpret the Ca deficit in terms of depletion due to processes happening in the disk. To test this hypothesis, we define a coarse depletion indicator using the flux of the Ca II K line and show that it correlates with disk properties. In particular, using indicators extracted from Spitzer/IRS spectra, we obtain that all the transitional and pre-transitional disks of the sample show depletion, consistent with trapping of refractories in pressure bumps created by planets and/or in the planets themselves. We find full disks with Ca depletion in the sample that also show indications of advanced dust evolution. We apply magnetospheric accretion models to fit the Balmer and Ca II line fluxes of a star showing clear Ca depletion and derive a Ca abundance in its inner disk of about 17% solar.

astro-ph.SR↗