arXiv subjects

Enrique Pérez-Montero

Publications and source records attributed to Enrique Pérez-Montero.

At least 19 recordsLinked to original sources

arXiv2026

Beyond the [OIII]$λ$4363 auroral line: [NeIII]$λ$3868 as a direct tracer of electron temperature

Auroral lines enable accurate measurements of chemical abundances in ionized gaseous nebulae thanks to their sensitivity to electron temperature. However, metal-enriched systems remain a challenge, as even deep observations cannot retrieve auroral lines due to their intrinsic faintness. To overcome this limitation, we present a novel approach to estimate electron temperatures in the conditions where the [OIII]$λ$4363 auroral line is barely detectable ($T_{e} < 11,000$ K). This approach relies on the detection of [NeIII]$λ$3868 and [OIII]$λ$4959,5007, which are among the brightest rest-frame optical emission lines. By means of detailed photoionization models, we derive a tight relation between the O3Ne3$\equiv$[OIII]$λ$4959,5007/[NeIII]$λ$3868 ratio and the electron temperature weighted in the O$^{++}$ dominated region. We test the validity of this relation in a large sample of galaxies that cover a wide range of redshifts z$\sim$0-9 and extragalactic HII regions. Our results show that the O3Ne3 ratio, in combination with the O3O2 ratio (tracer of ionization), yields electron temperature estimates consistent within the uncertainties with those based on [OIII]$λ$4363. The proposed relation can be used to estimate electron temperature in the cool (equivalently high-metal) regime [6,000, 13,500 K] where the emissivity of [OIII]$λ$4363 drops drastically.

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arXiv2025

Sulphur abundances in star-forming regions from optical emission lines: A new approach based on photoionization models consistent with the direct method

The derivation of sulphur chemical abundances in the gas-phase of star-forming galaxies is explored in this work, using the emission lines produced in these regions in the optical part of the spectrum and by means of photoionization models. We adapted the code HII-CHI-mistry to account for these abundances by implementing additional grids of models that assume a variable sulphur-to-oxygen abundance ratio, beyond the commonly assumed solar value. The addition of these models, and their use in a new iteration of the code allows us to use sulphur lines to precisely estimate the sulphur abundance, even in the absence of auroral lines. This approach aligns with the results from the direct method, and no additional assumptions about the ionization correction factor are needed, as the models directly predict the total sulphur abundance. We applied this new methodology to a large sample of star-forming regions from the MaNGA survey, and we explored the variation of the S/O ratio as a function of metallicity, making corrections for the significant contribution from diffuse ionized gas, which particularly affects the [SII] emission. Our results indicate no significant deviations from the solar S/O value in the range 8.0 < 12+log(O/H) < 8.7, where the bulk of the MaNGA sample stays, but also with possible enhancements of sulphur at the high metallicity regime. This may be linked to the depletion of oxygen in the gas-phase due to its incorporation onto dust grains, as it remains when other metallicity indicators independent of this depletion, as S/H itself, are used instead.

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arXiv2024

Chemical enrichment in LINERs from MaNGA. I. Tracing Oxygen and Nitrogen Nuclear Abundances in LINERs with Varied Ionizing Sources

The chemical enrichment in low-ionization nuclear emission-line regions (LINERs) is still an issue with spatial resolution spectroscopic data due to the lack of studies and the uncertainties in the nature of their ionizing source, despite being the most abundant type of active galaxies in the nearby Universe. Considering different scenarios for the ionizing source (hot old stellar populations, active galactic nuclei (AGN) or inefficient accretion disks), we analyze the implications of these assumptions to constrain the chemical content of the gas-phase interstellar medium (ISM). We used a sample of 105 galaxies from Mapping Nearby Galaxies at Apache Point Observatory (MaNGA) survey, whose nuclear central spaxels show LINER-like emission. For each scenario considered, we built a grid of photoionization models (4928 models for each considered ionizing source) which are later used in the open-source code HII-CHI-Mistry, allowing us to estimate chemical abundance ratios such as 12+log(O/H) or log(N/O) and constrain the ionization parameter that characterize the ionized ISM in those galaxies. We obtain that oxygen abundances in the nuclear region of LINER-like galaxies spread over a wide range 8.08 < 12+log(O/H) < 8.89, with a median solar value (in agreement with previous studies) if AGN models are considered. Nevertheless, the derived nitrogen-to-oxygen ratio is much less affected by the assumptions on the ionizing source, and point towards suprasolar values (log(N/O) = -0.69). By comparing the different analyzed scenarios, we show that if hot old stellar populations were responsible of the ionization of the ISM a complex picture (such as outflows and/or inflows scaling with galaxy chemical abundance) would be needed to explain the chemical enrichment history, whereas the assumption of AGN activity is compatible with the standard scenario found in most galaxies.

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arXiv2024

Astroaccesible: A multi-messenger outreach for a multi-messenger science

This contribution summarizes the main activities and objectives of the outreach project Astroaccesible, whose main aim is to carry the teaching and diffusion of astronomy among all kinds of collectives, focusing on blind and visually impaired (BVI) people. This project is led by a blind astronomer and aims to use a variety of resources based on different sensory channels, avoiding limiting the transmission of concepts to visual perception. This principle favors inclusion and benefits everyone, as the information is not presented using just one channel. This strategy is especially convenient for the nowadays typical data acquisition, where a variety of sources of information, not solely based on the collection of different spectral domains of electromagnetic radiation, is used. Moreover, the study of new multi-messenger astronomy could be much better understood using a multi-messenger teaching approach, favoring inclusion, motivation, and creativity.

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arXiv2024

Chemical abundances and deviations from the solar S/O ratio in the gas-phase ISM of galaxies based on infrared emission lines

The infrared (IR) range is extremely useful in the context of chemical abundance studies of the gas-phase interstellar medium (ISM) due to the large variety of ionic species traced in this regime, the negligible effects from dust attenuation or temperature stratification, and the amount of data that has been and will be released in the coming years. Taking advantage of available IR emission lines, we analysed the chemical content of the gas-phase ISM in a sample of 131 Star-Forming Galaxies (SFGs) and 73 Active Galactic Nuclei (AGNs). Particularly, we derived the chemical content via their total oxygen abundance in combination with nitrogen and sulfur abundances, and with the ionisation parameter. We used a new version of the code HII-CHI-Mistry-IR v3.1 which allows us to estimate log(N/O), 12+log(O/H), log(U), and, for the first time, 12+log(S/H) from IR emission lines, which can be applied to both SFGs and AGNs. We tested that the estimations from this new version, that only considers sulfur lines for the derivation of sulfur abundances, are compatible with previous studies. While most of the SFGs and AGNs show solar log(N/O) abundances, we found a large spread in the log(S/O) relative abundances. Specifically, we found extremely low log(S/O) values (1/10th solar) in some SFGs and AGNs with solar-like oxygen abundances. This result warns against the use of optical and IR sulfur emission lines to estimate oxygen abundances when no prior estimation of log(S/O) is provided.

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arXiv2024

Multiwavelength exploration of Extreme Emission Line Galaxies detected in miniJPAS survey

Extreme Emission Line Galaxies (EELGs) stand as remarkable objects due to their extremely metal poor environment and intense star formation. Considered as local analogues of high-redshift galaxies in the peak of their star-forming activity, they offer insights into conditions prevalent during the early Universe. Assessment of their stellar and gas properties is, therefore, of critical importance, which requires the assembly of a considerable sample, comprehending a broad redshift range. The Javalambre-Physics of the Accelerating Universe Astrophysical Survey (JPAS) plays a significant role in assembling such a sample, encompassing approximately 8000 deg2 and employing 54 narrow-band optical filters. The present work describes the development and subsequent application of the tools that will be employed in the forthcoming JPAS spectrophotometric data, allowing for the massive and automated characterization of EELGs that are expected to be identified. This fully automated pipeline (requiring only the object coordinates from users) constructs Spectral Energy Distributions (SEDs) by retrieving virtually all the available multi-wavelength photometric data archives, employs SED fitting tools and identifies optical emission lines. It was applied to the sample of extreme line emitters identified in the miniJPAS Survey, and its derived physical properties such as stellar mass and age, coupled with fundamental relations, mirror results obtained through spectral modeling of SDSS spectra. Thorough testing using galaxies with documented photometric measurements across different wavelengths confirmed the pipeline's accuracy, demonstrating its capability for automated analysis of sources with varying characteristics, spanning brightness, morphology, and redshifts. The modular nature of this pipeline facilitates any addition from the user.

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arXiv2024

Exploring the hardness of the ionising radiation with the infrared softness diagram. I. Similar effective temperature scales for starbursts and (ultra)luminous infrared galaxies

{We explored the {softness parameter} in the infrared, whose main purpose is the characterisation of the hardness of the incident ionising radiation in emission-line nebulae. This parameter is obtained from the combination of mid-infrared wavelength range transitions corresponding to consecutive ionisation stages in star-forming regions. We compiled observational data from a sample of star-forming galaxies (SFGs), including luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs), to study the softness parameter and its equivalent expression in two dimensions, the softness diagram. We compared them with predictions from photoionisation models to determine the shape of the ionising continuum energy distribution in each case. We also used the measured emission-line ratios as input for HCmistry-Teff-IR, a code that performs a Bayesian-like comparison with photoionisation model predictions in order to quantify the equivalent effective temperature (T*) and the ionisation parameter. We found similar average values within the errors of the softness parameter in (U)LIRGs (-0.57) in the rest of the SFGs (-0.51), which could be interpreted as indicative of a similar incident radiation field. This result is confirmed from the analysis using HCm-Teff-IR, which simultaneously points to a slightly lower, although similar within the errors, T* scale for (U)LIRGs, even when a higher dust-to-gas mass ratio is considered in the models for these objects. These derived T* values are compatible with the ionisation from massive stars, without any need of harder ionising sources, both for (U)LIRGs and the rest of the SFGs. However, the derived T* in (U)LIRGs do not show any correlation with metallicity. This could be interpreted as a sign that their similar average T* values are due to the attenuation of the energetic incident flux from massive stars by the heated dust mixed with the gas.

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arXiv2023

Merger-driven infall of metal-poor gas in luminous infrared galaxies: a deep dive beneath the mass-metallicity relation

The build up of heavy elements and the stellar mass assembly are fundamental processes in the formation and evolution of galaxies. Although they have been extensively studied through observations and simulations, the key elements that govern these processes, such as gas accretion and outflows, are not fully understood. This is especially true for luminous and massive galaxies, which usually suffer strong feedback in the form of massive outflows, and large-scale gas accretion triggered by galaxy interactions. For a sample of 77 luminous infrared (IR) galaxies, we derive chemical abundances using new diagnostics based on nebular IR lines, which peer through the dusty medium of these objects and allow us to include the obscured metals in our abundance determinations. In contrast to optical-based studies, our analysis reveals that most luminous IR galaxies remain close to the mass-metallicity relation. Nevertheless, four galaxies with extreme star-formation rates ($> 60$M$_{\odot }$yr$^{-1}$) in their late merger stages show heavily depressed metallicities of 12+log(O/H) $\sim 7.7$--$8.1$ along with solar-like N/O ratios, indicative of gas mixing processes affecting their chemical composition. This evidence suggests the action of a massive infall of metal-poor gas in a short phase during the late merger stages, eventually followed by a rapid enrichment. These results challenge the classical gas equilibrium scenario usually applied to main-sequence galaxies, suggesting that the chemical enrichment and stellar-mass growth in luminous IR galaxies are regulated by different processes.

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arXiv2023

Assessing model-based carbon and oxygen abundance derivation from ultraviolet emission lines in AGNs

We present an adapted version of the code HII-CHI-Mistry-UV (Pérez-Montero & Amorín 2017) to derive chemical abundances from emission lines in the ultraviolet, for use in narrow line regions (NLR) of Active Galactic Nuclei (AGN). We evaluate different ultraviolet emission line ratios and how different assumptions about the models, including the presence of dust grains, the shape of the incident spectral energy distribution, or the thickness of the gas envelope around the central source, may affect the final estimates as a function of the set of emission lines used. We compare our results with other published recipes for deriving abundances using the same emission lines and show that deriving the carbon-to-oxygen abundance ratio using CIII] $λ$ 1909 Å and OIII] $λ$ 1665 Å emission lines is a robust indicator of the metal content in AGN that is nearly independent of the model assumptions, similar to the case of star-forming regions. Moreover, we show that a prior determination of C/O allows for a much more precise determination of the total oxygen abundance using carbon UV lines, as opposed to assuming an arbitrary relationship between O/H and C/O, which can lead to non-negligible discrepancies.

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arXiv2022

The softness diagram for MaNGA star-forming regions: diffuse ionized gas contamination or local HOLMES predominance?

We explore the so-called softness diagram -- whose main function is to provide the hardness of the ionizing radiation in star-forming regions -- in order to check whether hot and old low-mass evolved stars (HOLMES) are significant contributors to the ionization within star-forming regions, as suggested by previous MaNGA data analyses. We used the code HCm-Teff to derive both the ionization parameter and the equivalent effective temperature (T*), adopting models of massive stars and planetary nebulae (PNe), and exploring different sets of emission lines in the softness diagram to figure out the main causes of the observed differences in the softness parameter in the MaNGA and CHAOS star-forming region samples. We find that the fraction of regions with a resulting T* > 60 kK, which are supposedly ionised by sources harder than massive stars, is considerably larger in the MaNGA (66%) than in the CHAOS (20%) sample when the [SII] $λλ$ 6716,6731 emission lines are used in the softness diagram. However, the respective fractions of regions in this regime for both samples are considerably reduced (20% in MaNGA and 10% in CHAOS) when the [NII] emission line at $λ$ 6584 is used instead. This may indicate that diffuse ionised gas (DIG) contamination in the lower resolution MaNGA data is responsible for artificially increasing the measured T* as opposed to there being a predominant role of HOLMES in the HII regions.

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arXiv2022

The universe in words: Astronomy for all through audio description within the outreach project Astroaccesible

Astroaccesible is an outreach project hosted by the Instituto de AstrofÍ sica de AndalucÍ a - CSIC and leaded by a blind astronomer aimed at the teaching and popularisation of astronomy and astrophysics among all kind of disabled and non-disabled people. Among the different strategies followed to transmit information to blind and partially sighted people, audio description is one of the most accesible and popular in the case of films and museums, but it has not been yet widely incorporated for the description of astronomical images. In this contribution we introduce {"The Universe in words", which are a series of videos describing images of some of the most popular objects in the Messier catalogue. These audio descriptions do not only have a clear inclusive aspect, but also imply a better and deeper understanding of the represented images for everybody. This is one of the most important aspects of using inclusive resources, as they also clearly improve the efficiency of the transmission process for all kind of public. These videos can also be used as supplementary material in of in-person activities and as a complement to other kind of materials, such as sonifications or models of the same or similar type of astronomical objects.

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arXiv2022

Measuring chemical abundances in AGN from infrared nebular lines: HII-CHI-Mistry-IR for AGN

Future and on-going infrared and radio observatories such as JWST, METIS or ALMA will increase the amount of rest-frame IR spectroscopic data for galaxies by several orders of magnitude. While studies of the chemical composition of the ISM based on optical observations have been widely spread over decades for SFG and, more recently, for AGN, similar studies need to be performed using IR data. This regime can be especially useful in the case of AGN given that it is less affected by temperature and dust extinction, traces higher ionic species and can also provide robust estimations of the chemical abundance ratio N/O. We present a new tool based on a bayesian-like methodology to estimate chemical abundances from IR emission lines in AGN. We use a sample of 58 AGN with IR spectroscopic data retrieved from the literature to probe the validity of our method. The estimations of the chemical abundances based on IR lines in our sample are later compared with the corresponding abundances derived from the optical emission lines in the same objects. HII-CHI-Mistry-IR takes advantage of photoionization models, characterized by the chemical abundance ratios O/H and N/O and the ionization parameter $U$, to compare their predicted emission-line fluxes with a set of observed values. Instead of matching single emission lines, the code uses some specific emission-line ratios sensitive to the above free parameters. We report mainly solar and also subsolar abundances for O/H in the nuclear region for our sample of AGN, whereas N/O clusters around solar values. We find a discrepancy between the chemical abundances derived from IR and optical emission lines, being the latter higher than the former. This discrepancy, also reported by previous studies of the composition of the ISM in AGN from IR observations, is independent from the gas density or the incident radiation field to the gas.

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arXiv2022

Painting graphs with sounds: CosMonic sonification project

CosMOnic (COSmos harMONIC) is a sonification project with a triple purpose: analysis (by means of sounds) of any type of data, source of inspiration for artistic creations, and pedagogical and dissemination purposes. In this contribution we present the work recently produced by CosMonic in the latter field, creating specific cases for the inclusive astronomy dissemination project AstroAccesible for blind and partially sighted people, but also aimed at a general public that wants to understand astrophysics in an alternative format. For this project, CosMonic seeks to create simple astronomical cases in their acoustic dimension in order to be easily understood. CosMonic's philosophy for these sonifications can be summarized in a simple metaphor: painting graphs with sounds. Sonification is a powerful tool that helps to enhance visual information. Therefore, CosMonic accompanies its audios with animations, using complementary methods to reach a general public. In addition to provide some cases created by CosMonic for inclusive astronomy, we also share our experience with different audiences, as well as suggest some ideas for a better use of sonification in (global) inclusive outreach.

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arXiv2022

Characterisation of the stellar content of SDSS EELGs through self-consistent spectral modelling

Extreme emission line galaxies (EELGs) are a notable galaxy genus, ultimately being regarded as local prototypes of early galaxies at the cosmic noon. Robust characterisation of their stellar content, however, is hindered by the exceptionally high nebular emission present in their optical spectroscopic data. This study is dedicated into recovering the stellar properties of a sample of 414 EELGs as observed by the SDSS Survey. Such is achieved by means of the spectral synthesis code FADO, which self-consistently considers the stellar and nebular emission in an optical spectrum. Additionally, a comparative analysis was carried on, by further processing the EELGs sample with the purely stellar spectral synthesis code Starlight, and by extending the analysis to a sample of 697 normal star-forming galaxies, expected to be less affected by nebular contribution. We find that, for both galaxy samples, stellar mass and mean age estimates by Starlight are systematically biased towards higher values, and that an adequate determination of the physical and evolutionary properties of EELGs via spectral synthesis is only possible when nebular continuum emission is taken into account. Moreover, the differences between the two population synthesis codes can be ascribed to the degree of star-formation activity through the specific star-formation rate and the sum of the flux of the most prominent emission lines. As expected, on the basis of the theoretical framework, our results emphasise the importance of considering the nebular emission while performing spectral synthesis, even for galaxies hosting typical levels of star-formation activity.

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arXiv2022

New calibrations for estimating the N/O ratio in HII regions

We use a sample of 536 \hii\ regions located in nearby spirals, with an homogeneous determination of their $T_e$-based abundances, to obtain new empirical calibrations of the N2O2, N2S2, O3N2, and N2 strong-line indices to estimate the nitrogen-to-oxygen abundance ratio when auroral lines are not detected. All indices are strongly correlated with the $T_e$-based $\log$(N/O) for our \hii\ region sample, even more strongly than with $12+\log$(O/H). N2O2 is the most strongly correlated index, and the best fit to the $\log$(N/O)-N2O2 relation is obtained with a second-order polynomial. The derived relation has a low dispersion ({\em rms}$<$0.09~dex), being valid in the range $-1.74 < $ N2O2 $< 0.62$ (or $-1.81 < $ $\log$(N/O) $< -0.13$). We have compared our calibration with previous ones and have discussed the differences between them in terms of the nature of the objects used as calibrators.

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arXiv2021

Chemical abundances in the nuclear region of nearby galaxies from the Palomar Survey

We estimate chemical abundances and ionization parameters in the nuclear region of a sample of 143 galaxies from the Palomar Spectroscopic Survey, composed by Star-Forming Galaxies (87), Seyferts 2 (16) and LINERs (40) using the \textsc{Hii-Chi-mistry} code. We also study for each spectral type the correlation of the derived quantities with other different properties of the host galaxies, such as morphology, stellar mass, luminosity and mass of their Supermassive Black Holes. The results obtained for Star-Forming Galaxies are used to check the soundness of our methodology. Then, we replicate a similar study for our sample of AGN, distinguishing between Seyferts 2 and LINERs. We report a saturation of Oxygen abundances for the nuclear regions of SFG. The correlations between chemical abundances and their host galaxy properties for SFG are in good agreement with previous studies. We find that Seyferts 2 present slightly higher chemical abundances but this result must be reexamined in larger samples of Seyfert galaxies. In contrast, we obtain lower chemical abundances for LINERs than for SFG. We confirm these relatively lower abundances for another sample of infrared luminous LINERs in the same stellar mass range. Our analysis of AGNs (both LINERs and Seyferts) shows that their host galaxy properties are not correlated with our estimated chemical abundances.

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arXiv2020

Ionized gaseous nebulae chemical abundance determination using the direct method

In this tutorial it is explained the procedure to analyze an optical emission-line spectrum produced by a nebula ionized by massive star formation. Particularly, it is described the methodology used to derive physical properties, such as electron density and temperature, and the ionic abundances of the most representative elements whose emission lines are present in the optical spectrum. The tutorial is focused on the direct method,based on the measurement of the electron temperature to derive the abundances, given that the ionization and thermal equilibrium of the ionized gas is dominated by the metallicity. The ionization correction factors used to obtain total abundances from the abundances of some of their ions are also given. Finally, some strong-line methods to derive abundances are described. These are used when no estimation of the temperature can be derived, but that can be consistent with the direct method if they are calibrated.

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arXiv2018

O/H-N/O: the curious case of NGC 4670

We use integral field spectroscopic (IFS) observations from Gemini North Multi-Object Spectrograph (GMOS-N) of a group of four H II regions and the surrounding gas in the central region of the blue compact dwarf (BCD) galaxy NGC 4670. At spatial scales of $\sim$ 9 pc, we map the spatial distribution of a variety of physical properties of the ionised gas: internal dust attenuation, kinematics, stellar age, star-formation rate, emission line ratios and chemical abundances. The region of study is found to be photoionised. Using the robust direct T$_e$-method, we estimate metallicity, nitrogen-to-oxygen ratio and helium abundance of the four H II regions. The same parameters are also mapped for the entire region using the HII-CHI-mistry code. We find that log(N/O) is increased in the region where the Wolf-Rayet bump is detected.The region coincides with the continuum region, around which we detect a slight increase in He abundance. We estimate the number of WC4, WN2-4 and WN7-9 stars from the integrated spectrum of WR bump region. We study the relation between log(N/O) and 12 + log(O/H) using the spatially-resolved data of the FOV as well as the integrated data of the H II regions from ten BCDs. We find an unexpected negative trend between N/O and metallicity. Several scenarios are explored to explain this trend, including nitrogen enrichment, and variations in star formation efficiency via chemical evolution models.

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