arXiv subjects

T. V. Ricci

Publications and source records attributed to T. V. Ricci.

At least 19 recordsLinked to original sources

arXiv2026

Small and Complex II: Characterizing the Disk and Stellar Envelope of Edge-on $z \sim 0$ Massive Compact Galaxies

We present multi-component photometric decompositions of $r$-band Hyper Suprime-Cam images for a sample of 75 edge-on massive compact galaxies (MCGs) at $z < 0.1$, selected as $+2σ$ outliers in the stellar mass-velocity dispersion relation and $-2σ$ outliers in the velocity dispersion-size relation. MCGs are composed of compact bulges and disks embedded within stellar envelopes of unclear physical nature. Comparing MCGs to a mass- and redshift-matched control sample of non-compact edge-on S0 galaxies with a similar three-component structure, we find that the smaller sizes of MCGs are not driven by a single component. MCGs host more compact bulges and envelopes ($R_\mathrm{e,bulge} \sim 0.3$ versus $0.5$kpc; $R_\mathrm{e,env} \sim 4.4$ versus $5.7$kpc), as well as shorter and thicker disks ($h_R \sim 1.1$ versus $1.7$kpc; $h_R/z_0 \sim 3.9$ versus $5.3$). The sizes of the structural components are coupled, suggesting their formation processes are linked. Median bulge- and disk-to-total flux fractions are similar in both samples, with $B/T \sim 0.3$ and $D/T \sim 0.4$. Envelope ellipticities span $ε_\mathrm{env} \sim 0$-$0.7$, with MCGs exhibiting rounder envelopes. Low- and high-ellipticity envelopes are broadly consistent with stellar halos and thick disks, respectively. However, the nature of intermediate ellipticity envelopes remains ambiguous from photometry alone. The coupling between component sizes, together with the survival of a substantial disk component, argues against dry minor mergers as the dominant envelope-building mechanism. A comparison with 8 relic galaxies reveals that MCGs and relics share similar bulge-disk-envelope structures and follow the same component size-mass relations, consistent with belonging to a common structural family.

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arXiv2026

Small and Complex I: The Three Component Structure of $z \sim 0$ Massive Compact Quiescent Galaxies

We investigate the morphology and structural properties of 246 massive compact quiescent galaxies (MCGs; $\log M_{\star} \sim 10$-$11$, $σ_{\mathrm{e}} \sim 150$-$350\,$km\,s$^{-1}$, $R_{\mathrm{e}} \sim 0.7$-$2.5\,$kpc) at $z \sim 0$, selected as outliers in the stellar mass-velocity dispersion and velocity dispersion-size relations, using $g$-, $r$-, and $i$-band Hyper Suprime-Cam images. We compare them to a control sample of average-sized quiescent galaxies (CSGs) matched in stellar mass, star formation rate, redshift, and $g-i$ color. Both samples are dominated by S0 galaxies, comprising $93\%$ of MCGs and $71\%$ of CSGs, while ellipticals account for $4\%$ and $11\%$, respectively. The fraction of interacting or morphologically disturbed systems is low in both samples ($13\%$ for MCGs and $16\%$ for CSGs). Multi-component decompositions of the $g$- and $r$-band images show that $75\%$ of MCGs require a three-component model (bulge, disk, and envelope), while $21\%$ are best fit by two components and $4\%$ by a single Sérsic profile. Two-component MCGs are preferentially low-inclination systems, suggesting that the three-component fraction represents a lower limit. In contrast, only $7\%$ of CSGs exhibit a comparable three-component structure. Bars are present in $29\%$ of CSGs but are absent in MCGs. For three-component systems, MCGs and CSGs have similar bulge ($R_\mathrm{e}=0.39$ vs.\ $0.45$\,kpc) and envelope ($R_\mathrm{e}=6.4$ vs.\ $5.8$\,kpc) sizes, while MCG disks are significantly more compact ($R_\mathrm{e}=1.9$ vs.\ $3.3$\,kpc). The envelope component shows a broad ellipticity distribution ($ε_\mathrm{Envelope} \sim 0.0$-$0.6$), which we interpret as corresponding to either a stellar halo or a thick disk.

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arXiv2026

Evaluating the efficacy of a data cube treatment procedure for kinematic analyses: application to NGC 3115 and NGC 4699

Data cubes have been increasingly used in astronomy. These data sets, however, are usually affected by instrumental effects and high-frequency noise. In this work, we evaluate the efficacy of a data cube treatment methodology, previously proposed by our research group, for analyses focused on the stellar and gas kinematics. To do that, we used data cubes of the central regions of the galaxies NGC 3115 and NGC 4699, obtained with the Integral Field Unit of the Gemini Multi-Object Spectrograph. For each galaxy, we analysed three data cubes: non-treated, filtered (with the Butterworth spatial filtering) and filtered and deconvolved (with the Richardson-Lucy deconvolution). For each data cube, we performed a dynamical modelling, using Jeans Anisotropic Models, to obtain, among other parameters, the masses of the central supermassive black holes. Both for NGC 3115 and NGC 4699, the values of the parameters provided by the dynamical modelling from the non-treated, filtered and filtered and deconvolved data cubes were compatible, at the 1-$σ$ level. However, the use of the Butterworth spatial filtering decreased the uncertainty of the parameters. The additional use of the Richardson-Lucy deconvolution decreased even more the uncertainty of the parameters. The complete data treatment procedure resulted in decreases of 41% and 45% in the uncertainties of the supermassive black hole masses in NGC 3115 and NGC 4699, respectively. These results indicate that our treatment procedure not only does not compromise analyses of data cubes focused on the stellar or gas kinematics, but actually improves the quality of the results.

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arXiv2025

Scaling relations at the central regions of nearby galaxies

Scaling relations between galactic parameters represent key pieces of evidence for investigating the processes of galaxy formation and evolution. In most studies, these relations have been obtained for large portions of the galaxies (i.e., on kpc scales), but it is also important to evaluate these relations in smaller scales. In this work, we used optical data cubes of a subsample of nearby galaxies of the DIVING 3D survey. These allowed us to analyze the scaling relations involving stellar velocity dispersion, stellar population age, and stellar population metallicity at the nuclear and circumnuclear regions of galaxies. We detected correlations between the stellar velocity dispersion and the age, metallicity, and total stellar mass. These correlations are independent of galaxy inclinations, considering all morphological types, nuclear activity, and the presence or absence of galactic bars. We detected, for the first time, a correlation between the stellar velocity dispersion and stellar metallicity in the nuclear regions of galaxies. It is found to be qualitatively consistent with the well-known stellar mass-metallicity relation. We also noted that barred galaxies tend to show younger and less metal-rich stellar populations than unbarred galaxies in the central regions, which may be a consequence of the bar triggering star formation in the nuclear regions of these objects. Some active galactic nuclei (AGNs) in our sample are positioned above the observed correlation between stellar velocity dispersion and stellar population age, suggesting that their nuclear stellar populations are younger than expected. This may be a consequence of positive AGN feedback, triggering star formation. Conversely, starburst galaxies do not show nuclear stellar populations at ages over one billion years.

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arXiv2024

Massive Compact Quiescent Galaxies in the $M_\star$ vs. $σ_\mathrm{e}$ Plane: Insights from stellar Population Properties

We investigated the stellar population properties of a sample of 1858 massive compact galaxies (MCGs) extracted from the SDSS survey. Motivated by previous results showing that older compact galaxies tend to have larger velocity dispersion at fixed stellar mass, we used the distance to the $σ_\mathrm{e}$ vs. $R_\mathrm{e}$ and $M_\star$ vs. $σ_\mathrm{e}$ relations as selection criteria. We found that MCGs are old ($\gtrsim 10$ Gyr), $α$-enhanced ([$α/\mathrm{Fe}] \sim 0.2$) and have solar to super-solar stellar metallicities. Metallicity increases with $σ_\mathrm{e}$, while age and [$α$/Fe] do not vary significantly. Moreover, at fixed $σ_\mathrm{e}$, metallicity and stellar mass are correlated. Compared to a control sample of typical quiescent galaxies, MCGs have, on average, lower metallicities than control sample galaxies (CSGs) of similar $σ_\mathrm{e}$. For $σ_\mathrm{e} \lesssim 225$ km/s, MCGs are older and more $α$-enhanced than CSGs, while for higher $σ_\mathrm{e}$ ages and $α$-enhancement are similar. The differences in age and $α$-enhancement can be explained by lower-$σ_\mathrm{e}$ CSGs being an amalgam of quiescent galaxies with a variety of ages. The origin of the differences in metallicity, however, is not clear. Lastly, we compared the stellar mass within the region probed by the SDSS fiber finding that, at fixed fiber velocity dispersion, MCGs have lower stellar masses on average. Since the velocity dispersion is a tracer of the dynamical mass, this raises the possibility that MCGs have, on average, a bottom heavier initial mass function or a larger dark matter fraction within the inner $\sim 1-2$ kpc.

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arXiv2023

The Origin of Massive Compact Galaxies: Lessons from IllustrisTNG

We investigate the formation and evolution of z=0 massive compact galaxies (MCGs) in the IllustrisTNG cosmological simulation. We found that, as in observations, MCGs are mainly old (median age $\sim 10.8$ Gyr), have super-solar metallicities (median $\log Z/Z_{\odot}\sim0.35$) and are $α$-enhanced (median $[α/Fe]\sim0.25$). The age distribution extends to younger ages, however, and a few MCGs are as young as $\sim7$ Gyr. In general, MCGs assemble their mass early and accrete low angular momentum gas, significantly increasing their mass while growing their size much slower. A small fraction of MCGs follow another evolutionary path, going through a compaction event, with their sizes shrinking by 40% or more. The accretion of low angular momentum gas leads to enhanced SMBH growth, and MCGs reach the threshold SMBH mass of $\log M_\mathrm{BH}\sim10^{8.5} M_\odot$ - when kinetic AGN feedback kicks in and quenches the galaxy - earlier than non-compact galaxies. Comparing MCGs to a sample of median-sized quiescent galaxies matched in effective velocity dispersion, we find that their accretion histories are very different. 71% of MCGs do not merge after quenching compared to 37% of median-sized quiescent galaxies. Moreover, tracing these populations back in time, we find that at least a third of median-sized quiescent galaxies do not have a compact progenitor, underscoring that both dry mergers and progenitor bias effects are responsible for the differences in the kinematics and stellar population properties of MCGs and median-sized quiescent galaxies.

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arXiv2023

The DIVING$^\mathrm{3D}$ Survey - Deep IFS View of Nuclei of Galaxies - III. Analysis of the nuclear region of the early-type galaxies of the sample

We analysed the nuclear region of all 56 early-type galaxies from the DIVING$^\mathrm{3D}$ Project, which is a statistically complete sample of objects that contains all 170 galaxies of the Southern Hemisphere with B < 12.0 mag and galactic latitude |b| < 15$^{\circ}$. Observations were performed with the Integral Field Unit of the Gemini Multi-Object Spectrograph. Emission lines were detected in the nucleus of 86$\pm$5% of the objects. Diagnostic diagrams were used to classify 52$\pm$7% of the objects as LINERs or Seyferts, while the other 34$\pm$6% galaxies without H$β$ or [O III] lines in their spectra were classified as weak emission line objects. Transition Objects are not seen in the sample, possibly because the seeing-limited data cubes of the objects allow one to isolate the nuclei of the galaxies from their circumnuclear regions, avoiding contamination from H II regions. A broad line region is seen in 29$\pm$6% of the galaxies. Of the 48 galaxies with emission-line nuclei, 41 have signs of AGNs. Some objects have also indications of shocks in their nuclei. Lenticular galaxies are more likely to have emission lines than ellipticals. Also, more luminous objects have higher [N II]/H$α$ ratios, which may be associated with the mass-metalicity relation of galaxies. A direct comparison of our results with the Palomar Survey indicates that the detection rates of emission lines and also of type 1 AGNs are higher in the DIVING$^\mathrm{3D}$ objects. This is a consequence of using a more modern instrument with a better spatial resolution than the Palomar Survey observations.

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arXiv2022

Active Galactic Nuclei signatures in Red Geyser galaxies from Gemini GMOS-IFU observations

Red Geysers are quiescent galaxies with galactic scale ionised outflows, likely due to low-luminosity Active Galactic Nuclei (AGN). We used Gemini GMOS-IFU observations of the inner $\sim 1.0-3.0$ kpc of nine Red Geysers selected from the MaNGA survey to study the gas ionisation and kinematics. The emission-line ratios suggest the presence of Seyfert/LINER (Low Ionisation Nuclear Emission Region) nuclei in all sources. Two galaxies show H$α$ equivalent width (H$α$ EW) larger than 3 Å(indicative of AGN ionisation) within an aperture 2.5 arcsec of diameter ($1.3-3.7$ kpc at the distance of galaxies) for MaNGA data, while with the higher resolution GMOS data, four galaxies present H$α$ EW$>3$ Åwithin an aperture equal to the angular resolution ($0.3-0.9$ kpc). For two objects with GMOS-IFU data, the H$α$ EW is lower than 3 Åbut larger than 1.5 Å, most probably due to a faint AGN. The spatially resolved electron density maps show values between $100-3000$ cm$^{-3}$ and are consistent with those determined in other studies. The large (MaNGA) and the nuclear scale (GMOS-IFU) gas velocity fields are misaligned, with a kinematic position angle difference between 12$^{\circ}$ and 60$^{\circ}$. The [NII]$λ$6583 emission-line profiles are asymmetrical, with blue wings on the redshifted side of the velocity field and red wings on the blueshifted side. Our results support previous indications that the gas in Red Geysers is ionised by an AGN, at least in their central region, with the presence of outflows, likely originating in a precessing accretion disc.

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arXiv2022

The DIVING$^\mathrm{3D}$ Survey -- Deep IFS View of Nuclei of Galaxies -- II. First results: nuclear emission-line properties of the mini-DIVING$^\mathrm{3D}$ sample

This work presents the first results of the Deep IFS View of Nuclei of Galaxies (DIVING$^\mathrm{3D}$) survey. We analysed the nuclear emission-line spectra of a sub-sample we call mini-DIVING$^\mathrm{3D}$, which includes all Southern galaxies with B < 11.2 and |b| > 15 degrees. We verified that $23\% \pm 4\%$ of the galaxies show nuclear emission-line properties characteristic of Low Ionization Nuclear Emission-Line Regions (LINERs). Diagnostic diagram analysis reveals an apparent dichotomy, not detected in previous studies, between objects classified as H II regions and as LINERs or Seyferts, with very few galaxies classified as transition objects. A possible explanation for this result is that at least part of the transition objects are composite systems, with a central LINER contaminated by the emission from circumnuclear H II regions. The higher spatial resolution of the DIVING$^\mathrm{3D}$ survey, in comparison with previous studies, allowed us to isolate the nuclear emission from circumnuclear contaminations, reducing the number of transition objects. We also propose an alternative scenario, in which the emission-line spectra of some transition objects are the result of shock heating by central outflows, together with photoionization by young stars. Clear evidence of active galactic nuclei (AGNs), in the optical and X-ray spectral bands, were detected in 69$\%$ of the LINERs in the mini-DIVING$^\mathrm{3D}$ sample. Considering the entire mini-DIVING$^\mathrm{3D}$ sample, evidence of AGNs were detected in 65$\%$ of the objects.

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arXiv2022

The DIVING$^{3D}$ Survey -- Deep IFS View of Nuclei of Galaxies -- I. Definition and Sample Presentation

We present the Deep Integral Field Spectrograph View of Nuclei of Galaxies (DIVING$^{3D}$) survey, a seeing-limited optical 3D spectroscopy study of the central regions of all 170 galaxies in the Southern hemisphere with B < 12.0 and |b| > 15 degrees. Most of the observations were taken with the Integral Field Unit of the Gemini Multi-Object Spectrograph, at the Gemini South telescope, but some are also being taken with the Southern Astrophysical Research Telescope (SOAR) Integral Field Spectrograph. The DIVING$^{3D}$ survey was designed for the study of nuclear emission-line properties, circumnuclear (within scales of hundreds of pc) emission-line properties, stellar and gas kinematics and stellar archaeology. The data have a combination of high spatial and spectral resolution not matched by previous surveys and will result in significant contributions for studies related to, for example, the statistics of low-luminosity active galactic nuclei, the ionization mechanisms in Low-Ionization Nuclear Emission-Line Regions, the nature of transition objects, among other topics.

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arXiv2021

A Gemini-NIFS view of the merger remnant NGC 34

The merger remnant NGC 34 is a local luminous infrared galaxy (LIRG) hosting a nuclear starburst and a hard X-ray source associated with a putative, obscured Seyfert~2 nucleus. In this work, we use adaptive optics assisted near infrared (NIR) integral field unit observations of this galaxy to map the distribution and kinematics of the ionized and molecular gas in its inner $\mathrm{1.2\,kpc \times 1.2\,kpc}$, with a spatial resolution of 70~pc. The molecular and ionized gas kinematics is consistent with a disc with projected major axis along a mean PA~=~$\mathrm{-9^{\circ}.2 \pm 0^{\circ}.9}$. Our main findings are that NGC~34 hosts an AGN and that the nuclear starburst is distributed in a circumnuclear star-formation ring with inner and outer radii of $\approx$~60 and 180~pc, respectively, as revealed by maps of the $\mathrm{[Fe II] / Paβ}$ and $\mathrm{H_{2} / Brγ}$ emission-line ratios, and corroborated by PCA Tomography analysis. The spatially resolved NIR diagnostic diagram of NGC~34 also identifies a circumnuclear structure dominated by processes related to the stellar radiation field and a nuclear region where $[Fe II]$ and H$_2$ emissions are enhanced relative to the hydrogen recombination lines. We estimate that the nuclear X-ray source can account for the central H$_2$ enhancement and conclude that $[Fe II]$ and H$_2$ emissions are due to a combination of photo-ionization by young stars, excitation by X-rays produced by the AGN and shocks. These emission lines show nuclear, broad, blue-shifted components that can be interpreted as nuclear outflows driven by the AGN.

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arXiv2021

The Puzzling Origin of Massive Compact Galaxies in MaNGA

We characterized the kinematics, morphology, and stellar population (SP) properties of a sample of massive compact quiescent galaxies (MCGs, $10 \lesssim \log M_\star$/$M_\odot \lesssim 11$ and $r_{\rm e} \sim 1-3 $kpc) in the MaNGA Survey, with the goal of constraining their formation, assembly history and assessing their relation with non-compact quiescent galaxies. We compared their properties with those of a control sample of median-sized quiescent galaxies ($r_{\rm e} \sim 4-8 $kpc) with similar effective velocity dispersions. MCGs have elevated rotational support, as evidenced by a strong anti-correlation between the Gauss-Hermite moment $h_3$ and $V/σ$. In contrast, 30$\%$ of control sample galaxies (CSGs) are slow rotators, and fast-rotating CSGs generally show a weak $h_3-V/σ$ anti-correlation. MCGs and CSGs have similar ages, but MCGs are more metal-rich and $α$-enhanced. Both MCGs and CSGs have shallow negative metallicity gradients and flat [$α$/Fe] gradients. On average, MCGs and CSGs have flat age gradients, but CSGs have a significantly larger dispersion of gradient values. The kinematics and SP properties of MCGs suggest that they experienced highly-dissipative gas-rich events, such as mergers, followed by an intense, short, and centrally concentrated burst of star formation, between 4 to 10 Gyr ago ($z\sim0.4-2$), and had a quiet accretion history since then. This sequence of events might be analogous to, although less extreme than, the compaction events which formed compact quiescent galaxies at $z \sim 2$. The small sizes of MCGs, and the high efficiency and short duration of their last star formation episode suggest that they are descendants of compact post-starburst galaxies.

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arXiv2020

Digging process in NGC 6951: the molecular disc bumped by the jet

We present a study of the central 200 pc of the galaxy NGC 6951, SAB(rs)bc, an active twin of the Milky Way, at a distance of 24 Mpc. Its nucleus has been observed in the optical with the GMOS-IFU, showing an outflow, and with the HST/ACS, revealing two extended structures with similar orientation, suggesting the presence of a collimating and/or obscuring structure. In order to ascertain this hypothesis, adaptive optics assisted NIR integral field spectroscopic observations were obtained with the NIFS spectrograph in the Gemini North telescope. We detected a compact structure of H$_2$ molecular gas, interpreted as a nearly edge-on disc with diameter of $\sim$47 pc, PA=124$°$ and velocity range from -40 to +40 km s$^{-1}$. This disc is misaligned by 32$°$ with respect to the radio jet and the ionization cones seen in the optical. There are two regions of turbulent gas, with position angles similar to the jet/cones, seen both in molecular and ionized phases; these regions are connected to the edges of the molecular disc and coincide with a high ratio of [N II]/H$α$=5, suggesting that these regions are shock excited, partially ionized or both. We explain these structures as a consequence of a "digging process" that the jet inflicts on the disc, ejecting the molecular gas towards the ionization cones. The dynamical mass within 17 pc is estimated as $6.3\times10^{6}$$M_{\odot}$. This is an interesting case of an object presenting evidence of a connected feeding-feedback structure.

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arXiv2020

Measuring the mass of the supermassive black hole of the lenticular galaxy NGC 4546

Most galaxies with a well-structured bulge host a supermassive black hole (SMBH) in their centre. Stellar kinematics models applied to adaptive optics (AO) assisted integral field unit observations are well-suited to measure the SMBH mass ($M_{BH}$) and also the total mass-to-light ratio [$(M/L)_{TOT}$] and possible anisotropies in the stellar velocity distribution in the central region of galaxies. In this work, we used new AO assisted Near-Infrared Integral Field Spectrometer (NIFS) observations and also photometric data from the Hubble Space Telescope Legacy Archive of the galaxy NGC 4546 in order to determine its SMBH mass. To do this, we applied the Jeans Anisotropic Modelling (JAM) method to fit the average second velocity moment in the line of sight $(\overline{v^2_{los}})$ of the stellar structure. In addition, we also obtained $(M/L)_{TOT}$ and the classical anisotropy parameter $β_z$=1--($σ_z$/$σ_R$)$^2$ for this object within a field of view of 200$\times$200 pc$^2$. Maps of the stellar radial velocity and of the velocity dispersion were built for this galaxy using the penalized pixel fitting ({\sc ppxf}) technique. We applied the Multi Gaussian Expansion procedure to fit the stellar brightness distribution. Using JAM, the best-fitting model for $\overline{v^2_{los}}$ of the stellar structure was obtained with $(M/L)_{TOT}$ = 4.34$\pm$0.07 (Johnson's R band), $M_{BH}$ = (2.56$\pm$0.16)$\times$10$^8$ M$_\odot$ and $β_z$ = --0.015$\pm$0.03 (3$σ$ confidence level). With these results, we found that NGC 4546 follows the $M_{BH}$ $\times$ $σ$ relation. We also measured the central velocity dispersion within a radius of 1 arcsec of this object as $σ_c$ = 241$\pm$2 km s$^{-1}$.

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arXiv2019

Detection of a double-peaked H$α$ component from the accretion disc of NGC 4958

Active Galactic Nuclei are objects associated with the presence of an accretion disc around supermassive black holes found in the very central region of galaxies with a well-defined bulge. In the optical range of the spectrum, a possible signature of the accretion disc is the presence of a broad double-peaked component that is mostly seen in H$α$. In this paper, we report the detection of a double-peaked feature in the H$α$ line in the nucleus of the galaxy NGC 4958. The narrow line region of this object has an emission that is typical of a LINER galaxy, which is the usual classification for double-peaked emitters. A central broad component, related to the broad line region (BLR) of this object, is seen in H$α$ and also in H$β$. We concluded that the double-peaked emission is emitted by a circular relativistic Keplerian disc with an inner radius $ξ_{\rm i}$ = 570$\pm$ 83, an outer radius $ξ_{\rm o}$ = 860$\pm$170 (both in units of $GM_{\rm SMBH}/c^2$), an inclination to the line of sight $i$ = 27.2$^o \pm$0.7$^o$ and a local broadening parameter $σ$ = 1310$\pm$70 km s$^{-1}$.

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arXiv2019

A treatment procedure for GMOS/IFU data cubes: application to NGC 2835

We present a set of treatment techniques for GMOS/IFU data cubes, including: correction of the differential atmospheric refraction; Butterworth spatial filtering, to remove high spatial-frequency noise; instrumental fingerprint removal; Richardson-Lucy deconvolution, to improve the spatial resolution of the observations. A comparison with HST images shows that the treatment techniques preserve the morphology of the spatial structures in the data cubes, without introducing distortions or ghost features. The treatment procedure applied to the data cube of the central region of the late-type galaxy NGC 2835 allowed the detection of a nuclear emitting region with emission-line ratios indicating a probable LINER, although the classifications of Transition Object or Seyfert galaxy cannot be discarded. Such a detection was not possible without the data treatment. This shows that the benefits provided by this treatment procedure are not merely cosmetic, but actually affect the quality of different types of analyses, like the determination of the fraction of galaxies, of different morphological types, with a central Seyfert/LINER/Transition object emission.

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arXiv2017

Optical and near-infrared IFU spectroscopy of the nuclear region of the AGN-starburst galaxy NGC 7582

NGC 7582 is an SB(s)ab galaxy which displays evidences of simultaneous nuclear activity and star formation in its centre. Previous optical observations revealed, besides the H II regions, an ionization cone and a gas disc in its central part. Hubble Space Telescope (HST) images in both optical and infrared bands show the active galactic nuclei (AGNs) and a few compact structures that are possibly associated with young stellar clusters. In order to study in detail both the AGN and evidence for star formation, we analyse optical (Gemini Multi-Object Spectrograph) and near-infrared (Spectrograph for Integral Field Observations in the Near Infrared) archival data cubes. We detected five nebulae with strong He II$λ$4686 emission in the same region where an outflow is detected in the [O III]$λ$5007 kinematic map. We interpreted this result as clouds that are exposed to high-energy photons emerging from the AGN throughout the ionization cone. We also detected Wolf$-$Rayet features which are related to emission of one of the compact clusters seen in the \textit{HST} image. Broad H$α$ and Br$γ$ components are detected at the position of the nucleus. [Fe II]$λ$1.644 $μ$m, H$_2λ$2.122 $μ$m and Br$γ$ flux maps show two blobs, one north and the other south from the nucleus, that seem to be associated with five previously detected mid-infrared sources. Two of the five He II nebulae are partially ionized by photons from starbursts. However, we conclude that the main source of excitation of these blobs is the AGN jet/disc. The jet orientation indicates that the accretion disc is nearly orthogonal to the dusty torus.

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arXiv2016

IFU spectroscopy of 10 early-type galactic nuclei - IV. Properties of the circumnuclear stellar kinematics

The study of stellar kinematic properties may provide hints on the formation and evolution of elliptical and lenticular galaxies. Although most previous studies have focused on the large scale of these galaxies, their central regions (scales of $\sim$ 100 pc) may contain important clues about their structure, such as kinematically decoupled cores. This is the fourth paper on a sample of 10 massive ($σ$ $>$ 200 km s$^{-1}$) and nearby ($d$ $<$ 31 Mpc) early-type galaxies, observed with the integral field unit of the Gemini South Multi Object Spectrograph. Here, we analyse the properties of the stellar kinematics in the circumnuclear region. We fitted the line-of-sight velocity distribution with a Gauss-Hermite function. In seven galaxies of the sample, we detected a rotation pattern in their radial velocity maps that are anti-correlated with $h_3$. We interpret this as stellar structures in rotation embedded in the bulges of the objects. Comparing the stellar kinematic results with the PCA Tomography results and also with the gas kinematic results of IC 5181, it seems that this object may have a non-axisymmetric potential at its centre. The velocity dispersion maps of four objects have a nuclear peak, which must correspond, in part, to unresolved stellar rotation. In NGC 1404, we detected a kinematic decoupled core with an extension of $\sim$ 200 pc. This galaxy also has a $σ$-drop in the centre, which may be related to both stellar components in counterrotation or with a kinematically cold star-forming region.

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