Scientific Program

Abstract: Star-forming galaxies at high-z show more extreme stellar and nebular properties than their lower-z counterparts. Among them, CIII]1908 emitters studied through deep optical spectra are proved to show properties approaching those which appear common in reionization galaxies, namely hard radiation fields, strong ionization and low metallicities. Thus, these emitters at z~3 can be used as testbeds to better understand connections between these properties and the physical mechanisms facilitating the escape of ionizing photons. In this talk, we present new results based on the VANDELS survey. We explore physical properties, including stellar metallicity and C/O abundance, for a large sample of CIII] emitters at z~3. We will show they follow trends consistent with Galactic thick disc stars and local HII galaxies. A qualitative agreement with chemical evolution models suggests they are experiencing an active phase of chemical enrichment.

Authors & Abstract: José Miguel Rodriguez Espinosa, J. Miguel Mas-Hesse, Eduard Salvador Solé,  & Alberto Manrique

I will explain a new method to measure the sizes of smoothly evolving ionised bubbles at the epoch of reionisation, using the ionising continuum photons (assuming they are emitted by galaxies) and the mean cosmic density, which is a function of the redshift.

I will show the advantages of our method. Indeed, our method can be used for individual sources and for proto-cúmulos. I will compare our method with other methods often used in the literature. Specially the method used by Yajima (2018) that it is commonly used. I will also explain why this later method gives very close results. Finally I will compare our method with other methods that have recently appeared in the literature. In particular, I will show that the method derived by Endsley and Stark (2022) gives very different results than other methods. In particular, this method has several parameters that are left to the user, thus not constrained by usual parameters.

Authors & Abstract: Borja Pérez-Díaz, Enrique Pérez-Montero, Juan Antonio Fernández-Ontíveros, Jose Manuel Vílchez

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 (HII-CHI-Mistry-IR) 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, composed by 43 Seyferts, 8 ULIRGs, 4 LIRGs and 3 LINERs, 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. There is a discrepancy between the chemical abundances derived from IR and optical emission lines, being the latter higher than the former. This result, consistent with previous studies of the composition of the ISM from IR observations, is independent from the gas density or the incident radiation field to the ISM.

Abstract: We use multi-object near-IR spectroscopy with VLT/KMOS to investigate the role of the environment in the evolution of the gas properties of galaxies in the Spiderweb protocluster at z=2.16. Based on rest-frame optical emission lines, [NII]λ6584 and Hα, we measure star formation rates (SFR) and gas-phase oxygen abundances of 39 protocluster members as a function of local density and global environment properties. Our results show that galaxies embedded in this structure display SFRs compatible with those of the Main Sequence of galaxies, and enhanced metallicity values (~0.1 dex) compared to their coeval field counterparts. Furthermore, we explore the gas fraction-gas metallicity diagram for a few galaxies with molecular gas masses measured by VLA/ATCA using CO(1-0). In the context of the gas-regulator model, our objects are consistent with relatively low mass loading factors, suggesting lower outflow activity than field samples at similar redshift and thus, hinting at the onset of environmental effects in this massive protocluster. We discuss the implications of these results on different scenarios of environmentally driven galaxy evolution during the early stages of massive cluster assembly.

Abstract: I will present new results of a representative sample of 24 local luminous infrared galaxies (LIRGs) at z<0.02 using high spatial resolution (<100 pc) data from ALMA. Our LIRGs lie above the Main-Sequence (MS), with typical stellar masses in the range 10^10-10^11 M⊙ and SFR∼30 M⊙ yr−1. I study the CO(2-1) and 1.3 mm continuum emissions to derive their effective radii using the curve-of-growth method. Up to date the molecular size of local LIRGs is poorly constrained. In this talk I want to shed more light on this topic using high resolution (sub-kpc scales) ALMA data comparing our results with those previously derived in the stellar and ionized phase in the same LIRG sample and also comparing the sizes of the different LIRG phases with those derived in local and high-z systems. I found that LIRGs are characterized by an extremely compact molecular gas distribution (<R_CO >∼ 0.7 kpc), factor X2 smaller than the ionized gas (<R_Hα >∼ 1.4 kpc), and X4 smaller than the stellar host (<R_star >∼ 2.2 kpc). Therefore, LIRGs deviate from local Spirals for which the molecular and stellar distributions have similar sizes (R_CO ∼R_star ∼ 3.9 kpc). In particular, the molecular size of LIRGs is similar to that of early-type galaxies (ETGs; R_CO ∼ 1 kpc), but about a factor of 6 more compact than Spirals of similar stellar mass. The presence of an active galactic nucleus (AGN) does not seem to strongly affect the (mean) molecular size in local LIRGs, although larger median radii by a factor of 2 are derived when considering galaxies with an AGN, as a result of the different range of R_CO characterizing the two subsamples. According to the results obtained for high-z (2<z<6) MS SFGs and (above the MS) SMGs using different tracers, high-z systems are characterized by more extended stellar, molecular and ionized gas emissions than local LIRGs (by a factor of ∼5). Their derived stellar size and stellar mass values support the idea that high-z SMGs might be the ’scaled-up’ version (both in size and stellar mass) of local LIRGs.

Abstract: Aiming at the detection of cosmological gas being accreted onto galaxies of the local Universe, we examined the Ha emission in the halo of 164 galaxies in the MUSE-Wide survey with observable Ha (redshift < 0.42). An exhaustive screening of the corresponding Ha images led us to select 166 reliable Ha emitting gas clouds. They are not created by instrumental artifacts, telluric line residuals, or high redshift interlopers. In addition to the mere existence of Ha emission, our main result is that Ha often shows double peak emission, with the drop in intensity at the rest-frame of the central galaxy. The presentation will describe how we have reached these results.

Abstract: I will analyze possible physical origins for the double-peak Ha emission we have detected in the halo of low redshift galaxies. Among others, we have examined cosmological gas accretion, galaxy outflows, accretion disks around compact objects, expanding bubbles driven by SNe, planetary nebulae, shocks, and tidal disruption events. Only one of these possibilities seem to be able to satisfy all observational constraints. I will reveal which one during the presentation.

Abstract: Extreme emission line galaxies (EELGs) are a notable galaxy genus, ultimately being regarded as local prototypes of early galaxies at the cosmic noon. Robust characterization 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 formerly acknowledged correlations, such as the positive trend between mean stellar age and stellar surface density, can only be retrieved when considering the nebular contribution. 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 emphasize the importance of considering the nebular emission while performing spectral synthesis, even for galaxies hosting typical levels of star-formation activity.

Authors & Abstract: Vilchez, J.M., Zinchenko, I., Pérez-Montero; E., Duarte-Puertas, S., Sukhorukov, A. V.; Sobolenko, M

The oxygen abundance (O/H) and the nitrogen-to-oxygen (N/O) abundance ratio, and their corresponding radial gradients, have been derived for a sample of 1431 galaxies from the MaNGA DR15 survey.
We found a correlation between the slope of the O/H gradient of the galaxy stellar mass, which is strongly non-linear, revealing that the steepest average O/H abundance gradients are measured in intermediate mass galaxies, whereas the flatter abundance gradients are shown by high- and low-mass galaxies.
The slope of N/O gradients versus galaxy stellar mass also shows a non-linear relation, with the steepest gradients derived for galaxies in the intermediate galaxy mass range [log(M/Msun) ~ 10], flatter gradients for high-mass galaxies, whereas the flattest gradients are found in low-mass galaxies. Overall, a general trend of steepening N/O gradients towards higher galaxy mass is confirmed. In this work we have unveiled the dependence between O/H and N/O gradients and the galaxy mean stellar age, as traced by the D(4000) index.

Authors & Abstract: Marisa García-Vargas, Mercedes Mollá, Esperanza Carrasco & Armando Gil de Paz

MEGARA LCB mode is a powerful Integral Field Unit (IFU) on GTC with a unique combination of spaxel size, 0.62”, spatial coverage (12.5“ x 11.3“), and high spectral resolution (R ~ 6000, 12000, 18000) in the visible range. This opens a new window of opportunity to boost the discoveries in eXtremely Metal Poor, XMPs, allowing the study of the spatial distribution of diffuse gas in the galaxy, spatially resolved kinematical studies of gas and stars, and a precise metallicity determination by clearly resolving spectral lines blended in lower resolution spectra. We are carrying out a project (11 galaxies in this moment) with Guaranteed Time and Open Time data with MEGARA at the GTC showing, for the first time, a complete and detailed 2D view of these galaxies. The stellar population is analyzed with the use of PopStar and pyPopStar models, and the consequent gas emission line spectra, from the ionizing young clusters, is interpreted with the combination of PopStar + CLOUDY photoionization code, allowing us to build evolutionary models to support the interpretation of the data. Finally, our deep observations will allow us to carry out this analysis all the way out to the limits of these galaxies.

Abstract: Theoretical predictions have suggested metallicity of the progenitor system producing a type Ia supernova (SN Ia) could play a role in determining its maximum luminosity. In this talk I will summarize our efforts within Estallidos to observationally investigate if such a relationship exists. We split our study in three redshift (z) ranges: (i) for low-z, we used the 4.2 m William Herschel Telescope (WHT) to obtain spectroscopy of a sample of 28 SN Ia host galaxies for which distances have been derived using methods independent from SNe Ia. We found a trend between SN Ia absolute magnitudes and the oxygen abundances of the host galaxies, in the sense that luminosities tend to be higher for galaxies with lower metallicities, in agreement with theoretical predictions; (ii) for intermediate-z (z<0.45), we estimated oxygen abundances of galaxies hosting SNe Ia from the Sloan Digital Sky Survey-II/Supernova (SDSS-II/SN) survey. We find a trend of decreasing oxygen abundance with increasing redshift for the most massive galaxies. Moreover, Hubble residuals versus oxygen abundance show a decreasing slope of -0.186 ± 0.123 mag dex-1 (1.52σ) in good agreement with theoretical expectations; (iii) we are currently studying if this trend holds at higher-z (0.4<z<1.0) studying SuperNova Legacy Survey (SNLS) host galaxies (See Iker Millán talk).

Abstract:The "HI KOALA IFS Dwarf galaxy Survey" (Hi-KIDS) uses KOALA+AAOmega at the Anglo-Australian Telescope (AAT) to get good-quality IFS data of a sample of nearby dwarf and irregular galaxies for which we already have 21cm HI interferometric data, exploring a parameter space which is not studied by current IFS galaxy surveys. Hi-KIDS studies the global and local properties of the ionized gas (metallicity, SFR, kinematics) and the stellar component (star-formation history, kinematics) of these dwarf galaxies. It also compares the combined IFS+radio data with theoretical predictions of chemical evolution models to investigate the efficiency of the conversion of gas into stars. Hi-KIDS will provide a comprehensive picture of the physical processes ruling dwarf galaxies, the data will be released publicly in AAO's Data Central as legacy.
In this talk I will provide an update of the survey, including discussing the effort made in the developing of the PyKOALA code to process the KOALA data. I will also emphasise how Hi-KIDS is an excellent example of a science case for exploring the resolved properties of nearby galaxies using BlueMUSE at the VLT in the near future.

Abstract: In this talk I will present the BEARD (Bulge Evolution And the Rise of Discs) survey, an International Time Program awarded with 78 telescope nights at the Roque de los Muchachos observatory for observing a volume-limited sample of 66 MW-like galaxies, i.e., massive spirals with small bulges. BEARD provides a multi nature dataset --very deep imaging (WFC@INT), long-slit spectroscopy (DOLORES@TNG), integral-field spectroscopy (MEGARA@GTC), narrow-band imaging (IO:O@LT), with the main scientific goal to understand how merging- and internal- (bar driven) processes influence the evolution of MW-like galaxies. In a Universe dominated by Cold Dark Matter (CDM), the growth of galaxies is expected to happen hierarchically: mergers of small systems eventually create a giant galaxy. This theory has been very successful at describing the evolution of ¡ Mpc-size structures (such as filaments and galaxy clusters) and it seems to work well for massive ellipticals. However, the stellar discs of massive spirals, such as our own Milky Way (MW), are fragile systems that may not survive a violent merger. Therefore, the question arises: how are discy giants built? I will present the status of the project and some preliminary analysis of the dataset.

Authors & Note: Arrabla Haro, P., Sobral, D., Rodríguez Espinosa J.M., Muñoz-Tuñón, C., Garcia-Dias, R. and Santos, S.

This talk was not presented in the workshop due to scheduling problems. However, Pablo had send us this video with his talk some days before the workshop.

Abstract: We present, herein, an unsupervised Machine Learning clustering focused on the search for differences in the shape of normalised rest-frame low-z Spectral Energy Distributions (SEDs). We will be looking for possible differences associated with the Stellar Populations (SPs) of the galaxies. To perform this study we used data from the narrow-band photometric survey 'Physics of the Accelerating Universe' (PAU) in the COSMOS field. We fit the SEDs of the selected sample using the CIGALE code and we have demonstrated that the joint of low-resolution (R ~ 50) photometric spectra and unsupervised classification of a large amount of ~ 6000 SEDs represents an excellent opportunity to analyse and detect hidden patterns between different physical parameters of the galaxies.