arXiv subjects

M. Hernández-Sánchez

Publications and source records attributed to M. Hernández-Sánchez.

5 recordsLinked to original sources

arXiv2026

CAVITY: Calar Alto Void Integral-field Treasury surveY: II. Second public data release

Studying galaxy evolution under the unique environmental conditions of cosmic voids provides an opportunity to disentangle the role of the large-scale environment in shaping mass assembly (both baryonic and dark matter), regulating galaxy physical properties, and driving the transformation from star-forming to quiescent systems. We present the second public data release (DR2) of the Calar Alto Void Integral-field Treasury Survey (CAVITY), an ongoing legacy programme designed to study void galaxies (VGs) across a range of nearby ($0.005 \leq z \leq 0.050$) voids with different sizes and dynamical stages, providing 200 science-grade optical integral-field spectroscopy (IFS) data cubes. By doubling the number of galaxies relative to DR1 while maintaining the same selection criteria, DR2 significantly increases the dataset's statistical power, enabling more robust characterization of galaxy properties and their correlations with environment. The observations were obtained with the PMAS/PPAK spectrograph on the 3.5-m Calar Alto telescope using the V500 configuration, covering the optical spectral range of 3745-7500 A at a resolution of 6 A (FWHM). The DR2 VG sample spans a broad range of stellar masses, morphologies, colours, and gas ionisation properties. We describe the sample selection, observing strategy, data reduction pipeline, quality-control procedures, and the public access to the CAVITY datasets and associated ancillary data on the survey's database. In addition, we present a characterisation of the large- and local-scale environments of CAVITY galaxies, showing that the 15 surveyed voids encompass a wide variety of sizes, galaxy richness, galaxy populations, and local structures, including galaxy groups. This release comprises 200 IFS data cubes, publicly available together with the master catalogues at the survey's dedicated webpage: https://cavity.caha.es/data/dr2/.

astro-ph.GA↗

arXiv2026

Galaxy groups within voids

In this work, we aim to identify and characterise a sample of galaxy groups within voids in the local Universe (z\,<\,0.08), taking into account the peculiarities of these vast and empty structures. The void galaxies used in this study are selected from a well-defined void galaxy sample, from which the parent sample of the Calar Alto Void Integral-field Treasury surveY (CAVITY) legacy project was drawn. To identify galaxy groups, we applied a fiends-of-friends (FoF) like group finder algorithm to the selected sample, ensuring a certain degree of gravitational binding among group members. The same algorithm has been applied to identify a control sample of groups not in clusters nor voids, referred as NCNV groups. The catalogue of groups consists on 1367 physically bound groups, with a total of 3040 galaxies, plus 14672 galaxy singlets. Most of the galaxies in voids are singlets (59\%), in contrast, most of the NCNV galaxies in the control sample are in groups (60\%). To consider the dynamical stage of the groups we used the parameters harmonic radius ($\rm R_H$), radial velocity dispersion ($\rm σ_{v_r}^2$), dimensionless crossing time ($\rm H_0 t_c$), and group virial mass ($\rm M_{vir}$). We also used the total optical ($r$-band) luminosity, L$_r$, to estimate the mass-to-light ratio ($\rm M/L$) of the groups. We studied the relations of void properties and these parameters with the group richness. Galaxy groups can be found in any void in the local Universe, with no dependency of group richness on the density of voids. The densest groups in the studied sample of voids are composed of six galaxies, therefore, voids generally contain small groups, in comparison to denser structures such as filaments, walls, and galaxy clusters. Galaxy groups within voids are typically loose groups, in an early stage of their evolution.

astro-ph.GA↗

arXiv2024

Multilayer directed random networks: Scaling of spectral properties

Motivated by the wide presence of multilayer networks in both natural and human-made systems, within a random matrix theory (RMT) approach, in this study we compute eigenfunction and spectral properties of multilayer directed random networks (MDRNs) in two setups composed by $M$ layers of size $N$: A line and a complete graph (node-aligned multiplex network). First, we numerically demonstrate that the normalized localization length $β$ of the eigenfunctions of MDRNs follows a simple scaling law given by $β=x^*/(1+x^*)$, with $x^*\propto (b_{\rm eff}^2/L)^δ$, $δ\sim 1$ and $b_{\rm eff}$ being the effective bandwidth of the adjacency matrix of the network of size $L=M\times N$. Here, $b_{\rm eff}$ incorporates both intra- and inter-layer edges. Then, we show that other eigenfunction and spectral RMT measures (the inverse participation ratio of eigenfunctions, the ratio between nearest- and next-to-nearest-neighbor eigenvalue distances, and the ratio between consecutive singular-value spacings) of MDRNs also scale with $x^*$.

cond-mat.dis-nn↗

arXiv2024

CAVITY, Calar Alto Void Integral-field Treasury surveY and project extension

We have learnt in the last decades that the majority of galaxies belong to high density regions interconnected in a sponge-like fashion. This large-scale structure is characterised by clusters, filaments, walls, where most galaxies concentrate, but also under-dense regions, called voids. The void regions and the galaxies within represent an ideal place for the study of galaxy formation and evolution as they are largely unaffected by the complex physical processes that transform galaxies in high-density environments. These void galaxies can hold the key as well to answer current challenges to the $Λ$CDM paradigm. The Calar Alto Void Integral-field Treasury surveY (CAVITY) is a Legacy project approved by the Calar Alto Observatory to obtain spatially resolved spectroscopic information of $\sim300$ void galaxies in the Local Universe (0.005 < z < 0.050) covering from -17.0 to -21.5 in $\rm r$ band absolute magnitude. It officially started in January 2021 and has been awarded 110 useful dark observing nights at the 3.5 m telescope using the PMAS spectrograph. Complementary follow-up projects including deep optical imaging, integrated, as well as resolved CO data, and integrated HI spectra, have joint the PMAS observations and naturally complete the scientific aim of characterising galaxies in cosmic voids. The extension data has been denominated CAVITY+. The data will be available to the whole community in different data releases, the first of which is planned for July 2024, and it will provide the community with PMAS data cubes for around 100 void galaxies through a user friendly, and well documented, database platform. We present here the survey, sample selection, data reduction, quality control schemes, science goals, and some examples of the scientific power of the CAVITY and CAVITY+ data.

astro-ph.GA↗

arXiv2024

Non-Hermitian diluted banded random matrices: Scaling of eigenfunction and spectral properties

Here we introduce the non-Hermitian diluted banded random matrix (nHdBRM) ensemble as the set of $N\times N$ real non-symmetric matrices whose entries are independent Gaussian random variables with zero mean and variance one if $|i-j|<b$ and zero otherwise, moreover off-diagonal matrix elements within the bandwidth $b$ are randomly set to zero such that the sparsity $α$ is defined as the fraction of the $N(b-1)/2$ independent non-vanishing off-diagonal matrix elements. By means of a detailed numerical study we demonstrate that the eigenfunction and spectral properties of the nHdBRM ensemble scale with the parameter $x=γ[(bα)^2/N]^δ$, where $γ,δ\sim 1$. Moreover, the normalized localization length $β$ of the eigenfunctions follows a simple scaling law: $β= x/(1 + x)$. For comparison purposes, we also report eigenfunction and spectral properties of the Hermitian diluted banded random matrix ensemble.

cond-mat.dis-nn↗