arXiv subjects

Alberto Rodríguez-Ardila

Publications and source records attributed to Alberto Rodríguez-Ardila.

At least 19 recordsLinked to original sources

arXiv2026

Simultaneous modeling of FeII emission in the optical and near-infrared in a prototypical Narrow-Line Seyfert 1 galaxy

This work investigates the FeII emission in active galactic nuclei (AGN), combining observational data from optical and near-infrared (NIR) spectra of the prototypical FeII emitter IZw1 with state-of-the-art photoionization modeling. Using updated FeII atomic datasets (Smyth et al. 2019; Tayal & Zatsarinny 2018; Bautista et al. 2015), we explore a wide parameter space to determine the physical conditions of FeII-emitting regions in the broad-line region (BLR). Our results show that optical ($R_{\rm 4570}$) and NIR ($R_{\rm 1μm}$) FeII emission can be simultaneously reproduced under consistent conditions, with the best agreement obtained using the Smyth et al. (2019) dataset, for hydrogen densities of $10^{11.0}$ to $10^{12.0}$ cm$^{-3}$ and near-solar metallicity. We quantify, for the first time, the impact of Lyman-$α$ fluorescence on the physical conditions of FeII emission in both regimes, revealing its dominant role in the NIR and, in contrast, highlighting the stronger influence of collisional processes in the optical. Additionally, for the first time, we compare optical and NIR FeII emission simultaneously with OI and the CaII triplet (CaT), reinforcing their connection to similar spatial regions and physical properties, as well as their usefulness as better proxies for optical FeII. Our findings support the idea of a vertical BLR structure, with NIR FeII and OI originating in less dense regions of the cloud than optical FeII and CaT.

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arXiv2024

Powerful outflows of compact radio galaxies

Gigahertz Peaked Spectrum (GPS) and Compact Steep Spectrum (CSS) sources are compact radio galaxies (RGs), with jets extending up to 20 kpc and ages <10^3 years. They are considered to evolve to Fanaroff-Riley RGs, but the real scenario to explain the compact sources remains unsolved. The young compact jets make GPS/CSS ideal for studying feedback in the nuclear region of AGNs because the jets are just starting to leave this region. Numerical simulations and jet power estimates suggest that compact sources can drive outflows on scales several times larger than the radio source itself, but the lack of suitable data limits comparisons between theory and observation. We carried out an optical spectroscopic study of 82 CSS/GPS with SDSS-DR12 data to investigate the influence of compact jets in the gas. We found outflowing gas components in the [OIII]\lambda5007 emission lines in half of our sample. The kinetic energy of the outflowing gas in compact sources is comparable to that observed in extended RGs, indicating that the compact jets can drive powerful outflows similar to those in FR RGs. The observed anti-correlation between the kinetic power of the outflow and the radio luminosity suggests an interaction between the young jet and the interstellar medium (ISM). This finding provides significant observational support for previous simulations of jet-ISM interactions and supports the evolutionary scenario for RGs. However, the lack of sources with high kinetic efficiency indicates that some compact galaxies may be frustrated sources.

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arXiv2024

Digging deeper into NGC 6868 II: ionized gas and excitation mechanism

We studied the ionized gas in the inner region ($\sim680\times470$ pc$^2$) of the galaxy NGC 6868 using Gemini/GMOS integral field unit observations. Channel maps reveal complex kinematics and morphology, indicating multiple processes at work in NGC 6868. Through emission-line fitting, we identified two ubiquitous components in our data: a narrow ($σ\sim110$ km s$^{-1}$) tracing an ionized gas disc and a broad component ($σ\sim300$ km s$^{-1}$) mainly associated with inflowing/outflowing gas. The derived V-band reddening shows a spatial distribution consistent with that obtained from stellar population synthesis, although with generally higher values. For the first time, we measured the electron temperature in NGC 6868, finding values ranging from $\sim 14000$ K in the central region to $\gtrsim20000$ K with an outward increasing temperature gradient. The electron density map exhibits an inverse relationship, with central values reaching $N_e\sim4000$ cm$^{-3}$ for the broad component decreasing to $N_e\sim100$ cm$^{-3}$ towards the edges of the field of view. Using BPT diagrams, we found that all spaxels are consistent with both AGN and shock ionization. However, when this information is combined with our kinematic and temperature findings, and further supported by the WHAN diagram, we argue that an AGN is the dominant ionisation mechanism in the central region of NGC 6868, while the extended outer component is ionized by a combination of hot low-mass evolved stars and shocks. According to our findings, shocks play a significant role in the ionization balance of this galaxy.

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arXiv2024

SMARTY: The mileS Moderate resolution neAr-infRared sTellar librarY

Most of the observed galaxies cannot be resolved into individual stars and are studied through their integrated spectrum using simple stellar populations (SSPs) models, with stellar libraries being a key ingredient in building them. Spectroscopic observations are increasingly being directed towards the near-infrared (NIR), where much is yet to be explored. SSPs in the NIR are still limited, and there are inconsistencies between different sets of models. One of the ways to minimize this problem is to have reliable NIR stellar libraries. The main goal of this work is to present SMARTY (mileS Moderate resolution neAr-infRared sTellar librarY) a ~0.9-2.4$μ$m stellar spectral library composed of 31 stars observed with the Gemini Near-IR Spectrograph (GNIRS) at the 8.1m Gemini North telescope and make it available to the community. The stars were chosen from the SMARTY library, for which the atmospheric parameters are reliable (and well tested), to populate different regions of the Hertzsprung-Russell (HR) diagram. Furthermore, five of these stars have NIR spectra available that we use to assess the quality of SMARTY. The remaining 26 stars are presented for the first time in the NIR. We compared the observed SMARTY spectra with synthetic and interpolated spectra, finding a mean difference of ~20% in the equivalent widths and ~1% in the overall continuum shape in both sets of comparisons. We computed the spectrophotometric broadband magnitudes and colours and compared them with the 2MASS ones, resulting in mean differences up to 0.07 and 0.10mag in magnitudes and colours, respectively. In general, a small difference was noted between the SMARTY spectra corrected using the continuum from the interpolated and the theoretical stars.

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arXiv2024

Joint analysis of the iron emission in the optical and near-infrared spectrum of I Zw 1

Constraining the physical conditions of the ionized media in the vicinity of an active supermassive black hole (SMBH) is crucial to understanding how these complex systems operate. Metal emission lines such as iron (Fe) are useful probes to trace the gaseous media's abundance, activity, and evolution in these accreting systems. Among these, the FeII emission has been the focus of many prior studies to investigate the energetics, kinematics, and composition of the broad-emission line region (BELR) from where these emission lines are produced. In this work, we present the first simultaneous FeII modeling in the optical and near-infrared (NIR) regions. We use CLOUDY photoionization code to simulate both spectral regions in the wavelength interval 4000-12000 Angstroms. We compare our model predictions with the observed line flux ratios for IZw1 - a prototypical strong FeII-emitting active galactic nuclei (AGN). This allows putting constraints on the BLR cloud density and metal content that is optimal for the production of the FeII emission, which can be extended to IZw1-like sources, by examining a broad parameter space. We demonstrate the salient and distinct features of the FeII pseudo-continuum in the optical and NIR, giving special attention to the effect of micro-turbulence on the intensity of the FeII emission.

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arXiv2023

UV Fe II emission model of HE 0413-4031 and its relation to broad-line time delays

Fe II emission is a well-known contributor to the UV spectra of active galactic nuclei and the modeling of this part may affect the results obtained for the MgII$\lambda2800$ emission, which is one of the lines used for black hole mass measurements and cosmological applications. We use the 11-year monitoring of the selected quasar HE 0413-4031 with the South African Large Telescope (SALT) and we supplement this monitoring with the near-IR spectrum taken with the SOAR telescope. A new redshift determination ($z=1.39117 \pm 0.00017$) using [OIII]$λλ4959,5007$ gave a very different value than the previous determination based only on the UV FeII pseudocontinuum ($z=1.3764$). It favors a different decomposition of the spectrum into Mg II and UV Fe II emissions. The line characteristics and the time delay of the Mg II emission ($224^{+21}_{-23}$ days) are not significantly affected. However, in comparison with the previous analysis, the rest-frame UV FeII time delay ($251^{+9}_{-7}$ days) is consistent with the inferred UV FeII line FWHM of $4200\,{\rm km/s}$ that is only slightly smaller than the MgII line FWHM. Hence the FeII-emitting material is more distant than the MgII-emitting gas in HE 0413-4031 by $\sim 0.023$ pc (4700 AU). The inferred velocity shift of both Mg II and UV Fe II lines with respect to the systemic redshift is now rather low, below 300 km s$^{-1}$. In addition, we construct an updated MgII radius-luminosity ($R-L$) relation from 194 sources, which is more than double the previous sample. The MgII $R-L$ relation is flatter than the UV FeII, optical FeII, and H$β$ $R-L$ relations. While the new decomposition of the spectrum is satisfactory, we see a need to create better Fe II templates using the newest version of the code CLOUDY.

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arXiv2023

First observation of double-peaked O I emission in the near-infrared spectrum of an active galaxy

Double-peaked profiles associated with the broad-line region (BLR) of active galactic nuclei (AGNs) are regarded as the clearest evidence of the presence of an accretion disk. They are most commonly detected by means of optical spectroscopy in the Balmer lines and in the Mg II $λ$2798 ultraviolet line. Here, we report the first unambiguous detection of a double-peak broad emission line associated with the O I $λ$11297 emission line in the near-infrared (NIR) in the local Seyfert 1 galaxy III Zw 002. Additionally, we detect simultaneously in the spectrum the double-peak emission in the Pa$α$ line and very likely in the He II $λ$10830. This is the first time that several broad double-peaked NIR emission lines have been detected simultaneously. The double-peaked profiles are fit using a disk-based model, with an additional Gaussian component attributed to nondisk clouds, which represents the classical BLR. Our results obtained from the fits reveal important parameters, such as disk inclination and geometry. From the double-peaked profile fits, we suggest that the BLR in III Zw 002 has a disk-like geometry, as it extends up to the outer edge of the BLR.

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arXiv2023

A Decade of Near-Infrared Variability in NGC4388: Insights into the AGN Structure

Variability studies have proven to be a powerful diagnostic tool for understanding the physics and properties of of Active Galactic Nuclei (AGNs). They provide insights into the spatial and temporal distribution of the emitting regions, the structure and dynamics of the accretion disk, and the properties of the central black hole. Here, we have analysed the K-band spectral variability of the Seyfert 1.9/2 galaxy NGC4388 spanning five epochs over a period of ten years. We have performed spectral synthesis of the nuclear region and found that the contribution of warm dust (T~800K) declined by 88% during these 10 years. In the same period, the [CaVIII] coronal line decreased 61%, whereas BrG emission declined 35%. For the HeI and H2, we did not detect any significant variation beyond their uncertainties. Based on the time span of these changes, we estimate that the region where the warm dust is produced is smaller than 0.6pc, which suggests that this spectral feature comes from the innermost part of the region sampled, directly from the AGN torus. On the other hand, the bulk of [CaVIII] is produced in the inner ~2pc and the nuclear BrG region is more extended, spanning a region larger than 3pc. Lastly, HeI and H2 are even more external, with most of the emission probably being produced in the host galaxy rather than in the AGN. This is the first spectroscopic variability study in the NIR for an AGN where the central source is not directly visible.

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arXiv2023

Digging deeper into NGC\,6868 I: stellar population

We use Gemini integral field unit observations to map the stellar population properties in the inner region ($\sim680\times470$ pc$^2$) of the galaxy NGC 6868. In order to understand the physical and chemical properties of the stellar content of this galaxy, we performed stellar population synthesis using the starlight code with the MILES simple stellar population models. We measured the absorption line indices Fe4383, Mg$_2$, Mg$_b$, Fe5270, Fe5335 for the whole FoV, and used them to derive Fe3 and [MgFe]'. These indices were used to derive [$α$/Fe]. This galaxy is dominated by old metal-rich populations (12.6 Gyr; 1.0 and 1.6 Z$_\odot$) with a negative metallicity gradient. We also found a recent ($\sim63$ Myr) metal-rich (1.6 Z$_{\odot}$) residual star formation in the centre of the galaxy. A dust lane with a peak extinction in the V band of 0.65 mag is seen. No signs of ordered stellar motion are found and the stellar kinematics is dispersion dominated. All indices show a spatial profile varying significantly along the FoV. Mg$_2$ shows a shallow gradient, compatible with the occurrence of mergers in the past. Mg$_b$ and Fe3 profiles suggest different enrichment processes for these elements. We observe three distinct regions: for $R<100$pc and $R>220$pc, Mg$_2$, Mg$_b$ anti correlate with respect to Fe3 and [MgFe]', and for $100 \text{pc}<R<220 \text{pc}$, they correlate, hinting at different enrichment histories. The [$α$/Fe] profile is really complex and has a central value of $\sim 0.2$ dex. We interpret this as the result of a past merger with another galaxy with a different [$α$/Fe] history, thus explaining the [$α$/Fe] maps.

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arXiv2021

A novel black-hole mass scaling relation based on coronal gas, and its dependence with the accretion disc

Using bona-fide black hole (BH) mass estimates from reverberation mapping and the line ratio [SiVI] 1.963$μ$m/Br$γ_{\rm broad}$ as tracer of the AGN ionising continuum, a novel BH-mass scaling relation of the form log($M_{\rm BH}) = (6.40\pm 0.17) - (1.99\pm 0.37) \times$ log ([SiVI]/Br$γ_{\rm broad})$, dispersion 0.47 dex, over the BH mass interval, $10^6 - 10^8$ M$_{\odot}$ is found. Following on the geometrically thin accretion disc approximation and after surveying a basic parameter space for coronal lines production, we believe one of main drivers of the relation is the effective temperature of the disc, which is effectively sampled by the [SiVI] 1.963$μ$m coronal line for the range of BH masses considered. By means of CLOUDY photoionisation models, the observed anti-correlation appears to be formally in line with the thin disc prediction T_disc $\propto {M_{\rm BH}}^{-1/4}$.

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arXiv2020

A novel black-hole mass scaling relation based on Coronal lines and supported by accretion predictions

Getting insights on the shape and nature of the ionizing continuum in astronomical objects is often done via indirect methods as high energy photons are absorbed by our Galaxy. This work explores the ionization continuum of active galactic nuclei (AGN) using the ubiquitous coronal lines. Using bona-fide BH mass estimates from reverberation mapping and the line ratio [Si VI] 1.963 micron/Br$γ_{\rm broad}$ as tracer of the AGN ionizing continuum, a novel BH-mass scaling relation of the form log($M_{\rm BH}) = (6.40\pm 0.17) - (1.99\pm 0.37) \times$ log ([Si VI]/Br$γ_{\rm broad})$, over the BH mass interval, $10^6 - 10^8$ M$_{\odot}$ with dispersion 0.47 dex is found. Following on the thin accretion disc approximation and after surveying a basic parameter space for coronal lines production, we believe that a key parameter driving this anti-correlation is the effective temperature of the accretion disc, this being effectively sampled by the coronal line gas. Accordingly, the observed anti-correlation becomes formally in line with the thin accretion disc prediction $T_{\rm{disc}} \propto {M_{\rm BH}}^{-1/4}$.

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arXiv2020

Spectroscopic study of the HII regions in the NGC 1232 galaxy

NGC 1232 is a face-on spiral galaxy that serves as an excellent laboratory for the study of star formation due to its proximity. Recent studies have revealed interesting features about this galaxy: X-ray observations suggest that it recently collided with a dwarf galaxy, however, no apparent remnant is observed. Here we search for evidence of this collision. We used long-slit optical spectra in two different positions obtained with the Goodman spectrograph at the SOAR telescope. We detected 18 HII regions in the north-south direction and 22 HII regions in the east-west direction and a background galaxy, NGC 1232B, for which we present the first redshift measurement and spectral analysis. We used the stellar population fitting technique to study the underlying stellar population and to subtract it from the spectra to measure the emission lines. The emission lines were used to determine the extinction, electron density, chemical abundance, and the star-formation rate gradient of NGC 1232. As is common in spiral galaxies, we found a stellar population gradient with older populations at the central regions and younger ones towards the outskirts, along with a negative oxygen abundance gradient of -0.16 dex/re. Due to the difficulty of measuring important emission lines, the number of objects for the abundance gradient is small, but there is a hint that this galaxy has a broken gradient profile, with a drop towards the center. If the collision caused any disturbance in the galaxy, we believe it would be small and hard to detect with a limited number of objects. From all the other measurements, we found no deviations from a typical spiral galaxy and no significant difference between different directions in the galaxy. The stellar population and emission line analysis of NGC 1232B suggest that it is a starburst galaxy.

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arXiv2020

Kiloparsec-scale jet-driven feedback in AGN probed by highly ionized gas: a MUSE/VLT perspective

We employ optical spectroscopy from the Multi Unit Spectroscopic Explorer (MUSE) combined with X-ray and radio data to study the highly-ionized gas (HIG) phase of the feedback in a sample of five local nearby Active Galactic Nuclei (AGN). Thanks to the superb field of view and sensitivity of MUSE, we found that the HIG, traced by the coronal line [FeVII] $λ$6089, extends to scales not seen before, from 700 pc in Circinus and up to ~2 kpc in NGC5728 and NGC3393. The gas morphology is complex, following closely the radio jet and the X-ray emission. Emission line ratios suggest gas excitation by shocks produced by the passage of the radio jet. This scenario is further supported by the physical conditions derived for the HIG, stressing the importance of the mechanical feedback in AGN with low-power radio jets.

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arXiv2020

Panchromatic Properties of the Extreme FeII Emitter PHL 1092

We present near-infrared spectroscopy of the NLS1 galaxy PHL1092 (z=0.394), the strongest FeII emitter ever reported, combined with optical and UV data. We modeled the continuum and the broad emission lines using a power-law plus a black body function and Lorentzian functions, respectively. The strength of the FeII emission was estimated using the latest FeII templates in the literature. We re-estimate the ratio between the FeII complex centered at 4570Ang and the broad component of H-Beta, R_FeII, obtaining a value of 2.58, nearly half of that previously reported (R_FeII=6.2), but still placing PHL1092 among extreme FeII emitters. The FWHM found for low ionization lines are very similar (FWHM~1200km/s), but significantly narrower than those of the Hydrogen lines (FWHM(H-Beta)~1900km/s). Our results suggest that the FeII emission in PHL1092 follows the same trend as in normal FeII emitters, with FeII being formed in the outer portion of the BLR and co-spatial with CaII, and OI, while H-Beta is formed closer to the central source. The flux ratio between the UV lines suggest high densities, log(n_H)~13.0 cm^{-3}, and a low ionization parameter, log(U)~-3.5. The flux excess found in the FeII bump at 9200Ang after the subtraction of the NIR FeII template and its comparison with optical FeII emission suggests that the above physical conditions optimize the efficiency of the ly-Alpha fluorescence process, which was found to be the main excitation mechanism in the FeII production. We discuss the role of PHL1092 in the Eigenvector 1 context.

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arXiv2019

Optical/NIR stellar absorption and emission-line indices from luminous infrared galaxies

We analyze a set of optical-to-near-infrared long-slit nuclear spectra of 16 infrared-luminous spiral galaxies. All of the studied sources present H$_2$ emission, which reflects the star-forming nature of our sample, and they clearly display H I emission lines in the optical. Their continua contain many strong stellar absorption lines, with the most common features due to Ca I, Ca II, Fe I, Na I, Mg I, in addition to prominent absorption bands of TiO, VO, ZrO, CN and CO. We report a homogeneous set of equivalent width (EW) measurements for 45 indices, from optical to NIR species for the 16 star-forming galaxies as well as for 19 early type galaxies where we collected the data from the literature. This selected set of emission and absorption-feature measurements can be used to test predictions of the forthcoming generations of stellar population models. We find correlations among the different absorption features and propose here correlations between optical and NIR indices, as well as among different NIR indices, and compare them with model predictions. While for the optical absorption features the models consistently agree with the observations,the NIR indices are much harder to interpret. For early-type spirals the measurements agree roughly with the models, while for star-forming objects they fail to predict the strengths of these indices.

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arXiv2018

Star Formation Rate Distribution in the Galaxy NGC 1232

NGC 1232 is a face-on spiral galaxy and a great laboratory for the study of star-formation due to its proximity. We obtained high spatial resolution Hα images of this galaxy, with adaptive optics, using the SAM instrument at the SOAR telescope, and used these images to study its H ii regions. These observations allowed us to produce the most complete H ii region catalog for it to date, with a total of 976 sources. This doubles the number of H ii regions previously found for this object. We used these data to construct the H ii luminosity function, and obtained a power-law index lower than the typical values found for Sc galaxies. This shallower slope is related to the presence of a significant number of high-luminosity H ii regions (logL>39 dex). We also constructed the size distribution function, verifying that, as for most galaxies, NGC 1232 follows an exponential law. We also used the Hα luminosity to calculate the star formation rate. An extremely interesting fact about this galaxy is that X-ray diffuse observations suggest that NGC 1232 recently suffered a collision with a dwarf galaxy. We found an absence of star formation around the region where the X-ray emission is more intense, which we interpret as a star formation quenching due to the collision. Along with that, we found an excess of star-forming regions in the northeast part of the galaxy, where the X-ray emission is less intense.

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arXiv2018

Probing Evolutionary Population Synthesis Models in the Near Infrared with Early Type Galaxies

We performed a near-infrared (NIR, $\sim$1.0$μ$m-2.4$μ$m) stellar population study in a sample of early type galaxies. The synthesis was performed using five different evolutionary population synthesis libraries of models. Our main results can be summarized as follows: low spectral resolution libraries are not able to produce reliable results when applied to the NIR alone, with each library finding a different dominant population. The two newest higher resolution models, on the other hand, perform considerably better, finding consistent results to each other and to literature values. We also found that optical results are consistent with each other even for lower resolution models. We also compared optical and NIR results, and found out that lower resolution models tend to disagree in the optical and in the NIR, with higher fraction of young populations in the NIR and dust extinction $\sim$1 magnitude higher than optical values. For higher resolution models, optical and NIR results tend do aggree much better, suggesting that a higher spectral resolution is fundamental to improve the quality of the results.

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arXiv2017

BAT AGN Spectroscopic Survey - IV: Near-Infrared Coronal Lines, Hidden Broad Lines, and Correlation with Hard X-ray Emission

We provide a comprehensive census of the near-Infrared (NIR, 0.8-2.4 $μ$m) spectroscopic properties of 102 nearby (z < 0.075) active galactic nuclei (AGN), selected in the hard X-ray band (14-195 keV) from the Swift-Burst Alert Telescope (BAT) survey. With the launch of the James Webb Space Telescope this regime is of increasing importance for dusty and obscured AGN surveys. We measure black hole masses in 68% (69/102) of the sample using broad emission lines (34/102) and/or the velocity dispersion of the Ca II triplet or the CO band-heads (46/102). We find that emission line diagnostics in the NIR are ineffective at identifying bright, nearby AGN galaxies because ([Fe II] 1.257$μ$m/Pa$β$ and H$_2$ 2.12$μ$m/Br$γ$) identify only 25% (25/102) as AGN with significant overlap with star forming galaxies and only 20% of Seyfert 2 have detected coronal lines (6/30). We measure the coronal line emission in Seyfert 2 to be weaker than in Seyfert 1 of the same bolometric luminosity suggesting obscuration by the nuclear torus. We find that the correlation between the hard X-ray and the [Si VI] coronal line luminosity is significantly better than with the [O III] luminosity. Finally, we find 3/29 galaxies (10%) that are optically classified as Seyfert 2 show broad emission lines in the NIR. These AGN have the lowest levels of obscuration among the Seyfert 2s in our sample ($\log N_{\rm H} < 22.43$ cm$^{-2}$), and all show signs of galaxy-scale interactions or mergers suggesting that the optical broad emission lines are obscured by host galaxy dust.

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