arXiv subjects

Angeles I. Díaz

Publications and source records attributed to Angeles I. Díaz.

8 recordsLinked to original sources

arXiv2026

Physical properties of circumnuclear ionising clusters. IV. NGC 1097

The circumnuclear star-forming ring of the barred spiral galaxy NGC 1097 provides a unique laboratory to study star formation under extreme conditions. This work aims to derive the physical properties of the circumnuclear star-forming regions (CNSFRs) using MUSE integral field spectroscopy observations. A total of 24 individual ionised HII are identified and analysed within its ring, which spans from $\sim$385 pc to $\sim$1.3 kpc. Despite the complex nuclear activity, all HII regions are found to be purely photoionised. Directly derived abundances reveal supersolar metallicities, with the highest one exceeding five times the solar value (12+log(S/H) = 7.875 $\pm$ 0.353, T$_e$([SIII]) = 3912 $\pm$ 567 K), and representing the highest abundance reported to date. In this high-metallicity regime, we find a break in the ionisation parameter-[SII]/[SIII] relation, which can be explained by changes in the ionisation structure and line emissivities, as confirmed by photoionisation models that successfully reproduce the observed emission-line ratios. Our results also indicate that the local gas supply regulates the star formation activity within the ring, with the young stars ionising 8 % of the total gas in the ring. Furthermore, our findings support a propagating starburst scenario, originating in the galaxy nucleus and extending towards the ends of the bar and into the circumnuclear ring through bar-driven shocks, this being consistent with the results of previous multi-wavelength studies. Finally, we likely detect optical signatures associated with one of the two known jets in this galaxy. This finding, together with the radio core emission previously found at sub-parsec scales, reflects the presence of feedback processes operating even on small galactic disc scales.

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arXiv2020

The delay time distribution of supernovae from integral-field spectroscopy of nearby galaxies

Constraining the delay-time distribution (DTD) of different supernova (SN) types can shed light on the timescales of galaxy chemical enrichment and feedback processes affecting galaxy dynamics, and SN progenitor properties. Here, we present an approach to recover SN DTDs based on integral field spectroscopy (IFS) of their host galaxies. Using a statistical analysis of a sample of 116 supernovae in 102 galaxies, we evaluate different DTD models for SN types Ia (73), II (28) and Ib/c (15). We find the best SN Ia DTD fit to be a power law with an exponent $α= -1.1\pm 0.3$ (50\% confidence interval), and a time delay (between star formation and the first SNe) $Δ= 50^{+100}_{-35}~Myr$ (50\% C.I.). For core collapse (CC) SNe, both of the Zapartas et al. (2017) DTD models for single and binary stellar evolution are consistent with our results. For SNe II and Ib/c, we find a correlation with a Gaussian DTD model with $σ= 82^{+129}_{-23}~Myr$ and $σ= 56^{+141}_{-9}~Myr$ (50\% C.I.) respectively. This analysis demonstrates that integral field spectroscopy opens a new way of studying SN DTD models in the local universe.

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arXiv2019

A Bayesian direct method implementation to fit emission line spectra: Application to the primordial He abundance determination

This work presents a Bayesian algorithm to fit the recombination and collisionally excited line spectra of gas photoionized by clusters of young stars. The current model consists in fourteen dimensions: two electron temperatures, one electron density, the extinction coefficient, the optical depth on the $HeI$ recombination lines and nine ionic species. The results are in very good agreement with those previously published using the traditional methodology. The probabilistic programming library PyMC3 was chosen to explore the parameter space via a NUTs sampler. These machine learning tools provided excellent convergence quality and speed. The primordial helium abundance measured from a multivariable regression using oxygen, nitrogen and sulfur was $Y_{P,\,O-N-S}=0.243\pm0.005$ in agreement with a standard Big Bang scenario.

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arXiv2018

Primordial helium abundance determination using sulphur as metallicity tracer

The primordial helium abundance $Y_P$ is calculated using sulphur as metallicity tracer in the classical methodology (with $Y_P$ as an extrapolation of $Y$ to zero metals). The calculated value, $Y_{P,\,S}=0.244\pm0.006$, is in good agreement with the estimate from the Planck experiment, as well as, determinations in the literature using oxygen as the metallicity tracer. The chemical analysis includes the sustraction of the nebular continuum and of the stellar continuum computed from simple stellar population synthesis grids. The $S^{+2}$ content is measured from the near infrared $\left[SIII\right]λ\lambda9069Å,9532Å$ lines, while an $ICF\left(S^{3+}\right)$ is proposed based on the $Ar^{3+}/Ar^{2+}$ fraction. Finally, we apply a multivariable linear regression using simultaneously oxygen, nitrogen and sulphur abundances for the same sample to determine the primordial helium abundance resulting in $Y_{P-O,\,N,\,S}=0.245\pm0.007$

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arXiv2017

Optical/Near-IR spatially resolved study of the H II galaxy Tol 02

The main goal of this study is to characterise the stellar populations in very low metallicity galaxies. We have obtained broad U, B, R, I, J, H, K, intermediate Strömgren y and narrow Hα and [OIII] deep images of the Wolf-Rayet, Blue Compact Dwarf, H II galaxy Tol 02. We have analysed the low surface brightness component, the stellar cluster complexes and the H II regions. The stellar populations in the galaxy have been characterised by comparing the observed broad band colours with those of single stellar population models. The main results are consistent with Tol 02 being formed by a 1.5 Gyr old disk component at the centre of which a group of 8 massive $>10^4 \, M_{\odot}$ stellar cluster clumps is located. Six of these clumps are 10 Myr old and their near infrared colours suggest that their light is dominated by Red Supergiant stars, the other two are young Wolf-Rayet cluster candidates of ages 3 and 5 Myr respectively. 12 H II regions in the star-forming region of the galaxy are also identified. These are immersed in a diffuse Hα and [OIII] emission that spreads towards the North and South covering the old stellar disk. Our spatial-temporal analysis shows that star formation is more likely stochastic and simultaneous within short time scales. The mismatch between observations and models cannot be attributed alone to a mistreat of the RSG phase and still needs to be further investigated.

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arXiv2016

Properties of the outer regions of spiral disks: abundances, colors and ages

We summarize the results obtained from our suite of chemical evolution models for spiral disks, computed for different total masses and star formation efficiencies. Once the gas, stars and star formation radial distributions are reproduced, we analyze the Oxygen abundances radial profiles for gas and stars, in addition to stellar averaged ages and global metallicity. We examine scenarios for the potential origin of the apparent flattening of abundance gradients in the outskirts of disk galaxies, in particular the role of molecular gas formation prescriptions.

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arXiv2015

A photometric comprehensive study of circumnuclear star forming rings: the sample

We present photometry in U, B, V, R and I continuum bands and in H$α$ and H$β$ emission lines for a sample of 336 circumnuclear star forming regions (CNSFR) located in early type spiral galaxies with different levels of activity in their nuclei. They are nearby galaxies, with distances less than 100 Mpc, 60\% of which are considered as interacting objects. This survey of 20 nuclear rings aims to provide insight into their star formation properties as age, stellar population and star formation rate. Extinction corrected H$α$ luminosities range from $1.3\times 10^{38}$ to $4\times 10^{41} erg s^{-1}$, with most of the regions showing values between 39.5 $\leq log L(Hα) \leq$ 40, which implies masses for the ionizing clusters higher than $2\times 10^{5} M_\odot $. H$α$ and H$β$ images have allowed us to obtain an accurate measure of extinction. We have found an average value of A$_V$ = 1.85 magnitudes. (U-B) colour follows a two maximum distribution around (U-B)$ \simeq$ -0.7, and -0.3; (R-I) also presents a bimodal behaviour, with maximum values of 0.6 and 0.9. Reddest (U-B) and (R-I) regions appear in non-interacting galaxies. Reddest (R-I) regions lie in strongly barred galaxies. For a significant number of HII regions the observed colours and equivalent widths are not well reproduced by single burst evolutionary theoretical models.

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arXiv2007

The N/O evolution on galaxies:the role played by the star formation history

We study the evolution of nitrogen resulting from a set of spiral and irregular galaxy models computed for a large number of input mass radial distributions and with various star formation efficiencies. We show that our models produce a nitrogen abundance evolution in good agreement with the observational data. In particular, low N/O values for high-redshift objects, such as those obtained for Damped Lyman Alpha galaxies can be obtained with our models simultaneously to higher and constant values of N/O as those observed for irregular and dwarf galaxies, at the same low oxygen abundances $\rm 12+log(O/H) \sim 7$ dex. The differences in the star formation histories of the regions and galaxies modeled are essential to reproduce the observational data in the N/O-O/H plane.

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