arXiv subjects

Javier Alvarez-Marquez

Publications and source records attributed to Javier Alvarez-Marquez.

6 recordsLinked to original sources

arXiv2026

Stratification of the AGN-Driven multi-phase outflows in the dwarf Seyfert galaxy NGC 4395

We present a multi-wavelength study of nuclear outflows in the nearby dwarf Seyfert galaxy NGC~4395, which hosts an intermediate-mass black hole. Using \textit{JWST}/NIRSpec and MIRI IFU spectroscopy (1.66--28.6~$μ$m), together with ALMA and Gemini/GMOS data, we probe the ionised and molecular gas on parsec scales. The JWST nuclear spectra reveal 134 emission lines, including H\,\textsc{i}, He, numerous fine-structure lines, H$_2$ rotational/ro-vibrational transitions, and several PAH bands. Modelling of the H$_2$ rotational lines reveals three warm/hot molecular components ($T\!\approx\!580$, 1480, and 2900~K), along with a cold ($<50$~K) phase traced by ALMA CO(2--1). Outflow signatures are detected in cold and warm/hot molecular gas, in H\,\textsc{i}, and in 36 fine-structure lines spanning ionisation potentials of 7.6--300~eV. Ionised outflow velocities range from 127 to 716~km\,s$^{-1}$, with blueshifted and redshifted components consistent with a stratified biconical geometry. The cold molecular gas shows a mass outflow rate nearly 1--2 orders of magnitude larger than that of the warm/hot molecular and ionised phases. The kinetic coupling efficiency is 0.003--0.12\% for the coronal-line gas and 0.4--1.4\% for the H\,\textsc{i} outflow, indicating that only the low-ionisation gas significantly impacts the surrounding ISM. Outflow velocity and the fraction of flux in the outflowing component increase with ionisation potential, implying that the most highly ionised gas originates closest to the AGN and is most efficiently accelerated.

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arXiv2026

A UV-Luminous Galaxy at z=11 with Surprisingly Weak Star Formation Activity

One of the major discoveries by the James Webb Space Telescope (JWST) is the identification of a large population of luminous galaxies at $z>10$, challenging theoretical models for early galaxy formation. The unexpectedly high number density of these systems has triggered intense debate about potential differences in the physical properties of galaxies at such extreme redshifts and those at lower redshift. However, progress has been limited by the lack of rest-frame optical diagnostics, which are critical for constraining the key properties. Here we present deep JWST/MIRI observations of a UV-luminous galaxy at $z=11.04$, CEERS2-588, only 400 Myr after the Big Bang. CEERS2-588 is detected in the MIRI F560W and F770W bands, while deep MIRI/MRS spectroscopy yields no detection of H$α$ or [OIII]$\lambda5007$ line, revealing a prominent Balmer break detected for the first time at $z>10$. Spectral energy distribution (SED) fitting indicates an extended star formation history possibly reaching $z>15$, followed by rapid quenching within the recent $\sim10$ Myr, in stark contrast to other $z>10$ galaxies. The MIRI detections also significantly improve our stellar mass estimate to $\mathrm{log}(M_*/M_\odot)=9.1^{+0.1}_{-0.1}$, making CEERS2-588 the most massive galaxy securely confirmed at $z>10$. Remarkably, the inferred gas-phase metallicity is near solar, exceeding predictions from current theoretical models. These results suggest that efficient starbursts play a key role in producing the abundant luminous galaxy population in the early universe.

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arXiv2025

ELPIS: Accelerated metal and dust enrichment in a proto-cluster core at $z\approx8$

We present a study of the metal, dust, and molecular gas content in galaxies within the A2744-z7p9OD proto-cluster at z ~ 7.88. We focus on two galaxy groups, the Quintet and the Chain, which are covered by the ELPIS survey (The Emission-Line Protocluster Imaging Survey of the furthest overdensity beyond Pandora's Cluster Abell 2744). [C II] 158 um emission is detected in five galaxies, revealing molecular gas reservoirs with log(M_gas/Msun) ~ 9.0-9.6, while dust continuum at the observed frame of 1.26 mm is detected in three galaxies, yielding dust masses of log(M_dust/Msun) ~ 6.0-6.4, assuming a dust temperature of T_dust = 45 (+15, -15) K. The derived properties, including stellar-to-dust mass ratios of log(M_dust/M_star) ~ -3 to -2 at log(M_star/Msun) ~ 9, and dust-to-gas mass ratios of log(M_dust/M_gas) ~ -4 to -3 at 12+log(O/H) ~ 8, place these galaxies in an intermediate regime: higher than the very low ratios expected from supernova-driven dust production, but still below the levels attained once efficient grain growth dominates. These values indicate a transition phase of dust mass assembly, likely reflecting the onset of grain growth via metal accretion under accelerated evolution in the proto-cluster core.

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arXiv2024

MIRI Deep Imaging Survey (MIDIS) of the Hubble Ultra Deep Field

The recently launched James Webb Space Telescope (JWST) is opening new observing windows on the distant universe. Among JWST's instruments, the Mid Infrared Instrument (MIRI) offers the unique capability of imaging observations at wavelengths $λ> 5μ$m. This enables unique access to the rest frame near infra-red (NIR, $λ\ge 1$\mum) emission from galaxies at redshifts $z>4$ and the visual ($λ\gtrsim 5000$Å) rest frame for $z>9$. We here report on the guaranteed time observations (GTO) from the MIRI European Consortium, of the Hubble Ultra Deep Field (HUDF), forming the MIRI Deep Imaging Survey (MIDIS), consisting of an on source integration time of $\sim41$ hours in the MIRI/F560W (5.6 $μ$m) filter. To our knowledge, this constitutes the longest single filter exposure obtained with JWST of an extragalactic field as yet.

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arXiv2023

JWST MIRI flight performance: Detector Effects and Data Reduction Algorithms

The detectors in the Mid-Infrared Instrument (MIRI) of the James Webb Space Telescope (JWST) are arsenic-21 doped silicon impurity band conduction (Si:As IBC) devices and are direct descendants of the Spitzer IRAC22 long wavelength arrays (channels 3 and 4). With appropriate data processing, they can provide excellent per-23 formance. In this paper we discuss the various non-ideal behaviors of these detectors that need to be addressed24 to realize their potential. We have developed a set of algorithms toward this goal, building on experience with25 previous similar detector arrays. The MIRI-specific stage 1 pipeline algorithms, of a three stage JWST cali-26 bration pipeline, were developed using pre-flight tests on the flight detectors and flight spares and have been27 refined using flight data. This paper describes these algorithms, which are included in the first stage of the28 JWST Calibration Pipeline for the MIRI instrument.

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arXiv2021

The UV-brightest Lyman continuum emitting star-forming galaxy

We report the discovery of J0121+0025, an extremely luminous and young star-forming galaxy (M_UV = -24.11, log[L_Lya / erg s^-1] = 43.8) at z = 3.244 showing copious Lyman continuum (LyC) leakage (f_esc,abs ~ 40%). High signal-to-noise ratio rest-frame UV spectroscopy with the Gran Telescopio Canarias reveals a high significance (7.9 sigma) emission below the Lyman limit (< 912A), with a flux density level f_900A = 0.78 +/- 0.10 uJy, and strong P-Cygni in wind lines of OVI 1033A, NV 1240A and CIV 1550A that are indicative of a young age of the starburst (<10 Myr). The spectrum is rich in stellar photospheric features, for which a significant contribution of an AGN at these wavelengths is ruled out. Low-ionization ISM absorption lines are also detected, but are weak (EW0 ~ 1A) and show large residual intensities, suggesting a clumpy geometry of the gas with a non-unity covering fraction or a highly ionized ISM. The contribution of a foreground and AGN contamination to the LyC signal is unlikely. Deep optical to Spitzer/IRAC 4.5um imaging show that the spectral energy distribution of J0121+0025 is dominated by the emission of the young starburst, with log(M*/Msun) = 9.9 +/- 0.1 and SFR = 981 +/- 232 Msun yr^-1. J0121+0025 is the most powerful LyC emitter known among the star-forming galaxy population. The discovery of such luminous and young starburst leaking LyC radiation suggests that a significant fraction of LyC photons can escape in sources with a wide range of UV luminosities and are not restricted to the faintest ones as previously thought. These findings might shed further light on the role of luminous starbursts to the cosmic reionization.

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