arXiv subjects

L. Sánchez-Menguiano

Publications and source records attributed to L. Sánchez-Menguiano.

At least 19 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/.

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arXiv2026

ALMA CO-CAVITY II. Resolved Scaling Relations in Void Galaxies

Scaling relations involving star formation rates (SFRs), molecular gas mass, and stellar mass are key to understand galaxy evolution, and have previously been explored at resolved scales. However, they have not been examined with particular emphasis on the large-scale environments (LSEs). In this work, we study the resolved Schmidt-Kennicutt relation (rSK), molecular gas main sequence (rMGMS) and star-forming main sequence (rSFMS) from a sample of 41 void galaxies (VGs) residing in the least dense regions of the Universe. Using high-resolution interferometric CO(1-0) data and optical IFU data from the ALMA CO-CAVITY and CAVITY surveys at scales of 2.5" (0.8-2.1 kpc), we study these relations for the full sample as well as for individual galaxies in voids. We fit the relations, finding a similar parametrisation as that used for galaxies from all LSEs. However, the rMGMS is the tightest of the three relations ($σ_{rMGMS}=0.16$ dex, $σ_{rSK}=0.21$ dex, and $σ_{rSFMS}=0.24$ dex), unlike in other samples. We find that a large source of deviations in the relations comes from galaxy-to-galaxy variations. However, the rMGMS is less affected by these variations. It has been suggested that the rMGMS arises from the concentration of molecular gas within the gravitational potential set by the stellar content and dark matter. We hypothesise that deviations from the rMGMS trace changes in the gravitational potential occurring on longer time-scales, whereas deviations in the rSK and the rSFMS are driven by more rapid variations in the SFR. This distinction is particularly relevant for our sample of VGs because the 41 ALMA CO-CAVITY VGs are more isolated than galaxies in other LSEs, and therefore are less affected by events that can significantly alter the gas distribution or trigger SF on short time-scales. In this sense, the rMGMS is likely the most stable of these relations over time.

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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.

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arXiv2026

ALMA CO-CAVITY I. Resolved Molecular Gas in Void Galaxies

The environment plays a key role in galaxy evolution, yet it remains unclear how detailed molecular gas properties and their connection to star formation and stellar content are influenced by both large-scale and local environments. Here we introduce the ALMA CO-CAVITY project, the first interferometric CO(1-0) survey of a large sample of 41 void galaxies (VGs) to characterise in detail their molecular gas properties. It is built over the CAVITY project, offering optical integral field unit (IFU) data, enabling a direct, pixel-to-pixel comparison between molecular gas (from ALMA), star formation, and stellar properties, as well as the derivation of their scaling relations. In this work we present ALMA data products for our sample, containing data cubes, moment maps and position-velocity diagrams at angular resolutions of 1 arcsec. We also present molecular gas, stellar mass, and star formation rate surface density maps at a common resolution of 2.5 arcsec. We contextualise our sample against representative unresolved and resolved surveys. While our sample provides a good representation of the VG population and follows the distribution of key properties seen in star-forming galaxy samples, galaxies included in resolved studies from the literature tend to be more massive, less isolated, and located in denser large-scale environments. We present global scaling relations for the ALMA CO-CAVITY sample and find that the molecular gas main sequence exhibits the smallest scatter (0.21 dex), followed by the Schmidt-Kennicutt relation and the star-forming main sequence. From integrated properties alone, we find that these scaling relations for VGs are compatible with those for denser environments. This paper lays the foundation for forthcoming studies exploiting this unique dataset.

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arXiv2024

Analysis of the Internal Radial Gradient of Chemical Abundances in Spiral Galaxies from CALIFA

The study of chemical evolution is of paramount importance for understanding the galaxies evolution. Models and observations propose an inside-out mechanism in the formation of spiral galaxy disks implying a negative radial gradient of elemental abundances when represented in logarithmic scale. However, observed chemical abundance gradients, in some instances, deviate from a single linear negative straight line, revealing inner drops or outer flattenings, particularly in more massive galaxies. This study analyzes oxygen abundance gradients in spiral galaxies based on observations from the Calar Alto Legacy Integral Field Area (CALIFA) survey. Our focus is specifically on examining oxygen abundance gradient profiles, as obtained with data from HII regions, with a special emphasis on the inner radial gradient. We employ an automated fitting procedure to establish correlations between the physical properties of galaxies and bulges and the presence of these inner drops, seeking for potential explanations for these gradient variations. We find that the different criteria used in the literature to distinguish HII regions from other ionization sources in the galaxy, such as Active Galactic Nuclei, significantly impact the results, potentially altering abundance gradient profiles and uncovering galaxies with distinct inner drops. Additionally, we analyze the abundance radial gradients to investigate the impact of diffuse ionized gas (DIG) decontamination on oxygen abundances over the featuring inner drops. We observe that DIG, concentrated mainly in the central regions of galaxies, can modify oxygen abundance gradient profiles if left unaddressed.

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arXiv2024

Morphologies of galaxies within voids

In this work we investigate the effects of the environment on the evolution of void galaxies. In particular, we study their morphology and explore its dependence with their location within the void where the galaxies reside, as well as with properties of the void, such as void size or galaxy number-density. The sample of void galaxies that we use in this study is based on the catalogue of cosmic voids and void galaxies in the SDSS-DR7. Since we are interested into study the morphology of void galaxies, we select galaxies in the redshift range 0.005$\leq$z$\leq$0.080, and use the public galaxy morphologies for SDSS with Deep Learning algorithms to divide the sample between early- and late-type void galaxies. We analyse the fraction of galaxies of each morphology type as a function of the void-centric distance, the size of the voids, and the density of galaxies in each void. There is a higher abundance of late-type galaxies with respect to early-type galaxies within voids, which remains nearly constant from the inner to the outer part of the voids. We do not find any dependence of the fraction of early- and late-type galaxies with respect to the size of the voids or the number-density of galaxies in the voids. Galaxies in voids follow the morphology-density relation, in the sense that the majority of the galaxies in voids (the most under-dense large-scale environments) are late-type galaxies. However, we find no difference between voids with lower or higher volume number-density of galaxies: the fraction of early- and late-type galaxies do not depend on the density of the voids. The physical processes responsible for the evolution from late towards earlier types (such as external environmental quenching) are not sufficiently effective in voids or so slow (internal secular quenching) that their contributions do not appear in the morphology-density relation.

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arXiv2024

CO-CAVITY project: Molecular gas and star formation in void galaxies

Cosmic voids, distinguished by their low-density environment, provide a unique opportunity to explore the interplay between the cosmic environment and the processes of galaxy formation and evolution. Data on the molecular gas has been scarce so far. In this paper, we continue previous research done in the CO-CAVITY pilot project to study the molecular gas content and properties in void galaxies to search for possible differences compared to galaxies that inhabit denser structures. We observed at the IRAM 30 m telescope the CO(1-0) and CO(2-1) emission of 106 void galaxies selected from the CAVITY survey. Together with data from the literature, we obtained a sample of 200 void galaxies with CO data. We conducted a comprehensive comparison of the specific star formation rate (sSFR = SFR/M$_*$), the molecular gas fraction (MH$_2$/M$_*$), and the star formation efficiency (SFE = SFR/MH$_2$) between the void galaxies and a comparison sample of galaxies in filaments and walls, selected from the xCOLD GASS survey. We found no statistically significant difference between void galaxies and the comparison sample in the molecular gas fraction as a function of stellar mass for galaxies on the star-forming main sequence (SFMS). However, for void galaxies, the SFE was found to be constant across all stellar mass bins, while there is a decreasing trend with M$_*$ for the comparison sample. Finally, we found some indications for a smaller dynamical range in the molecular gas fraction as a function of distance to the SFMS in void galaxies. Overall, our analysis finds that the molecular gas properties of void galaxies are not very different from denser environments. The physical origin of the most significant difference that we found - a constant SFE as a function of stellar mass in void galaxies - is unclear and requires further investigation and higher-resolution data.

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arXiv2024

The effect of local and large scale environment on the star formation histories of galaxies

We aim to investigate how the local environment influences the star formation history (SFH) of galaxies residing in various large-scale environments. We categorise a sample of 9384 galaxies into the three primary large scale structures (voids, walls \& filaments, and clusters) and further classify them based on their local environment (as either "singlets" or group members), through a search of companion galaxies within sky-projected distances $Δr_p < 0.45$ Mpc and velocity differences $Δv < 160$ $\text{km s}^{-1}$. Subsequently, we explore these subsamples through SFH data from previous works. Throughout the study, galaxies are divided into long-timescale SFH galaxies (LT-SFH), which assemble their mass steadily along cosmic time, and short-timescale SFH galaxies (ST-SFH), which form their stars early. We then compare characteristic mass assembly look-back times. The distributions of mass assembly look-back times in ST-SFH galaxies are statistically different for singlets and groups. These differences are only found in LT-SFH galaxies when studying these distributions in stellar mass bins. Our results indicate that the large-scale environment is related to a delay in mass assembly of up to $\sim$2 Gyr, while this delay is $<$1 Gyr in the case of local environment. The effect of both kinds of environment is more significant in less massive galaxies, and in LT-SFHs. Our results are consistent with galaxies in groups assembling their stellar mass earlier than singlets, especially in voids and lower mass galaxies. Local environment plays a relevant role in stellar mass assembly times, although we find that large-scale structures also cause a delay in mass assembly, more so in the case of cluster galaxies.

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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.

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arXiv2023

Galaxies in voids assemble their stars slowly

Galaxies in the Universe are distributed in a web-like structure characterised by different large-scale environments: dense clusters, elongated filaments, sheetlike walls, and under-dense regions, called voids. The low density in voids is expected to affect the properties of their galaxies. Indeed, previous studies have shown that galaxies in voids are on average bluer and less massive, and have later morphologies and higher current star formation rates than galaxies in denser large-scale environments. However, it has never been observationally proved that the star formation histories (SFHs) in void galaxies are substantially different from those in filaments, walls, and clusters. Here we show that void galaxies have had, on average, slower SFHs than galaxies in denser large-scale environments. We also find two main SFH types present in all the environments: 'short-timescale' galaxies are not affected by their large-scale environment at early times but only later in their lives; 'long-timescale' galaxies have been continuously affected by their environment and stellar mass. Both types have evolved slower in voids than in filaments, walls, and clusters.

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arXiv2022

pyHIIextractor: A tool to detect and extract physical properties of HII regions from Integral Field Spectroscopic data

We present a new code named pyHIIextractor, which detects and extracts the main features (positions and radii) of clumpy ionized regions, i.e. candidate HII regions, using Hα emission line images. Our code is optimized to be used on the dataproducts provided by the Pipe3D pipeline (or dataproducts with such a format), applied to high spatial resolution Integral Field Spectroscopy data (like that provided by the AMUSING++ compilation, using MUSE). The code provides the properties of both the underlying stellar population and the emission lines for each detected H ii candidate. Furthermore, the code delivers a novel estimation of the diffuse ionized gas (DIG) component, independent of its physical properties, which enables a decontamination of the properties of the HII regions from the DIG. Using simulated data, mimicking the expected observations of spiral galaxies, we characterise pyHIIextractor and its ability to extract the main properties of the H ii regions (and the DIG), including the line fluxes, ratios and equivalent widths. Finally, we compare our code with other such tools adopted in the literature, which have been developed or used for similar purposes: pyhIIexplorer, SourceExtractor, HIIphot, and astrodendro. We conclude that pyHIIextractor exceeds the performance of previous tools in aspects such as the number of recovered regions and the distribution of sizes and fluxes (an improvement that is especially noticeable for the faintest and smallest regions). pyHIIextractor is therefore an optimals tool to detect candidate HII regions, offering an accurate estimation of their properties and a good decontamination of the DIG component.

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arXiv2019

SIGNALS: I. Survey Description

SIGNALS, the Star formation, Ionized Gas, and Nebular Abundances Legacy Survey, is a large observing program designed to investigate massive star formation and HII regions in a sample of local extended galaxies. The program will use the imaging Fourier transform spectrograph SITELLE at the Canada-France-Hawaii Telescope. Over 355 hours (54.7 nights) have been allocated beginning in fall 2018 for eight consecutive semesters. Once completed, SIGNALS will provide a statistically reliable laboratory to investigate massive star formation, including over 50 000 resolved HII regions : the largest, most complete, and homogeneous database of spectroscopically and spatially resolved extragalactic HII regions ever assembled. For each field observed, three datacubes covering the spectral bands of the filters SN1 (363 -386 nm), SN2 (482 - 513 nm), and SN3 (647 - 685 nm) are gathered. The spectral resolution selected for each spectral band is 1000, 1000, and 5000, respectively. As defined, the project sample will facilitate the study of small-scale nebular physics and many other phenomena linked to star formation at a mean spatial resolution of 20 pc. This survey also has considerable legacy value for additional topics including planetary nebulae, diffuse ionized gas, andsupernova remnants. The purpose of this paper is to present a general outlook of the survey, notably the observing strategy, galaxy sample, and science requirements.

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arXiv2018

The shape of oxygen abundance profiles explored with MUSE: evidence for widespread deviations from single gradients

We characterise the oxygen abundance radial distribution of a sample of 102 spiral galaxies observed with VLT/MUSE using the O3N2 calibrator. The high spatial resolution of the data allows us to detect 14345 HII regions with the same image quality as with photometric data, avoiding any dilution effect. We develop a new methodology to automatically fit the abundance radial profiles, finding that 55 galaxies of the sample exhibit a single negative gradient. The remaining 47 galaxies also display, as well as this negative trend, either an inner drop in the abundances (21), an outer flattening (10) or both (16), which suggests that these features are a common property of disc galaxies. The presence and depth of the inner drop depends on the stellar mass of the galaxies with the most massive systems presenting the deepest abundance drops, while there is no such dependence for the outer flattening. We find that the inner drop appears always around $\rm 0.5\,r_e$, while the position of the outer flattening varies over a wide range of galactocentric distances. Regarding the main negative gradient, we find a characteristic slope of $α_{O/H} = -\,0.10\pm0.03\,\rm{dex}/r_e$. This slope is independent of the presence of bars and the density of the environment. However, when inner drops or outer flattenings are detected, slightly steeper gradients are observed. This suggests that radial motions might play an important role in shaping the abundance profiles. We define a new normalisation scale ($r_{O/H}$) for the radial profiles based on the characteristic abundance gradient, with which all the galaxies show a similar position for the inner drop ($\sim0.5\,r_{O/H}$) and the outer flattening ($\sim1.5\,r_{O/H}$).Finally, we find no significant dependence of the dispersion around the negative gradient with any galaxy property, with values compatible with the uncertainties of the derived abundances.

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arXiv2017

Star formation in the local Universe from the CALIFA sample. II. Activation and quenching mechanisms in bulges, bars, and disks

We estimate the current extinction-corrected H$α$ star formation rate (SFR) of the different morphological components that shape galaxies (bulges, bars, and disks). We use a multi-component photometric decomposition based on SDSS imaging to CALIFA Integral Field Spectroscopy datacubes for a sample of 219 galaxies. This analysis reveals an enhancement of the central SFR and specific SFR (sSFR $=$ SFR/$M_{\star}$) in barred galaxies. Along the Main Sequence, we find more massive galaxies in total have undergone efficient suppression (quenching) of their star formation, in agreement with many studies. We discover that more massive disks have had their star formation quenched as well. We evaluate which mechanisms might be responsible for this quenching process. The presence of type-2 AGNs plays a role at damping the sSFR in bulges and less efficiently in disks. Also, the decrease in the sSFR of the disk component becomes more noticeable for stellar masses around 10$^{10.5}$ M$_{\odot}$; for bulges, it is already present at $\sim$10$^{9.5}$ M$_{\odot}$. The analysis of the line-of-sight stellar velocity dispersions ($σ$) for the bulge component and of the corresponding Faber-Jackson relation shows that AGNs tend to have slightly higher $σ$ values than star-forming galaxies for the same mass. Finally, the impact of environment is evaluated by means of the projected galaxy density, $Σ$$_{5}$. We find that the SFR of both bulges and disks decreases in intermediate-to-high density environments. This work reflects the potential of combining IFS data with 2D multi-component decompositions to shed light on the processes that regulate the SFR.

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arXiv2017

Arm and interarm abundance gradients in CALIFA spiral galaxies

Spiral arms are the most singular features in disc galaxies. These structures can exhibit different patterns, namely grand design and flocculent arms, with easily distinguishable characteristics. However, their origin and the mechanisms shaping them are unclear. The overall role of spirals in the chemical evolution of disc galaxies is another unsolved question. In particular, it has not been fully explored if the \hii\,regions of spiral arms present different properties from those located in the interarm regions. Here we analyse the radial oxygen abundance gradient of the arm and interarm star forming regions of 63 face-on spiral galaxies using CALIFA Integral Field Spectroscopy data. We focus the analysis on three characteristic parameters of the profile: slope, zero-point, and scatter. The sample is morphologically separated into flocculent versus grand design spirals and barred versus unbarred galaxies. We find subtle but statistically significant differences between the arm and interarm distributions for flocculent galaxies, suggesting that the mechanisms generating the spiral structure in these galaxies may be different to those producing grand design systems, for which no significant differences are found. We also find small differences in barred galaxies, not observed in unbarred systems, hinting that bars may affect the chemical distribution of these galaxies but not strongly enough as to be reflected in the overall abundance distribution. In light of these results, we propose bars and flocculent structure as two distinct mechanisms inducing differences in the abundance distribution between arm and interarm star forming regions.

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arXiv2017

Observational hints for radial migration in disc galaxies from CALIFA

Context: According to numerical simulations, stars are not always kept at their birth galactocentric distances but migrate. The importance of this radial migration in shaping galactic light distributions is still unclear. However, if it is indeed important, galaxies with different surface brightness (SB) profiles must display differences in their stellar population properties. Aims: We investigate the role of radial migration on the light distribution and the radial stellar content by comparing the inner colour, age and metallicity gradients for galaxies with different SB profiles. We define these inner parts avoiding the bulge and bar regions and up to around three disc scale-lengths (type I, pure exponential) or the break radius (type II, downbending; type III, upbending). Methods: We analyse 214 spiral galaxies from the CALIFA survey covering different SB profiles. We make use of GASP2D and SDSS data to characterise their light distribution and obtain colour profiles. The stellar age and metallicity profiles are computed using a methodology based on full-spectrum fitting techniques (pPXF, GANDALF, and STECKMAP) to the IFS CALIFA data. Results: The distributions of the colour, stellar age and stellar metallicity gradients in the inner parts for galaxies displaying different SB profiles are unalike as suggested by Kolmogorov-Smirnov and Anderson-Darling tests. We find a trend in which type II galaxies show the steepest profiles of all and type III the shallowest, with type I galaxies displaying an intermediate behaviour. Conclusions: These results are consistent with a scenario in which radial migration is more efficient for type III galaxies than for type I systems with type II galaxies presenting the lowest radial migration efficiency. In such scenario, radial migration mixes the stellar content flattening the radial stellar properties and... [abriged]

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arXiv2017

The Mass-Metallicity Relation revisited with CALIFA

We present an updated version of the mass--metallicity relation (MZR) using integral field spectroscopy data obtained from 734 galaxies observed by the CALIFA survey. These unparalleled spatially resolved spectroscopic data allow us to determine the metallicity at the same physical scale ($\mathrm{R_{e}}$) for different calibrators. We obtain MZ relations with similar shapes for all calibrators, once the scale factors among them are taken into account. We do not find any significant secondary relation of the MZR with either the star formation rate (SFR) or the specific SFR for any of the calibrators used in this study, based on the analysis of the residuals of the best fitted relation. However we do see a hint for a (s)SFR-dependent deviation of the MZ-relation at low masses (M$<$10$^{9.5}$M$_\odot$), where our sample is not complete. We are thus unable to confirm the results by Mannucci et al. (2010), although we cannot exclude that this result is due to the differences in the analysed datasets. In contrast, our results are inconsistent with the results by Lara-Lopez et al. (2010), and we can exclude the presence of a SFR-Mass-Oxygen abundance Fundamental Plane. These results agree with previous findings suggesting that either (1) the secondary relation with the SFR could be induced by an aperture effect in single fiber/aperture spectroscopic surveys, (2) it could be related to a local effect confined to the central regions of galaxies, or (3) it is just restricted to the low-mass regime, or a combination of the three effects.

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arXiv2016

Evidence of ongoing radial migration in NGC 6754: Azimuthal variations of the gas properties

Understanding the nature of spiral structure in disk galaxies is one of the main, and still unsolved questions in galactic astronomy. However, theoretical works are proposing new testable predictions whose detection is becoming feasible with recent development in instrumentation. In particular, streaming motions along spiral arms are expected to induce azimuthal variations in the chemical composition of a galaxy at a given galactic radius. In this letter we analyse the gas content in NGC 6754 with VLT/MUSE data to characterise its 2D chemical composition and H$α$ line-of-sight velocity distribution. We find that the trailing (leading) edge of the NGC 6754 spiral arms show signatures of tangentially-slower, radially-outward (tangentially-faster, radially-inward) streaming motions of metal-rich (poor) gas over a large range of radii. These results show direct evidence of gas radial migration for the first time. We compare our results with the gas behaviour in a $N$-body disk simulation showing spiral morphological features rotating with a similar speed as the gas at every radius, in good agreement with the observed trend. This indicates that the spiral arm features in NGC 6754 may be transient and rotate similarly as the gas does at a large range of radii.

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