arXiv subjects

Marco Berton

Publications and source records attributed to Marco Berton.

At least 19 recordsLinked to original sources

arXiv2026

Super-Eddington Accretion and Early-Stage Feedback in Ton S180

Narrow-line Seyfert 1 (NLSy1) galaxies are key laboratories for studying rapid supermassive black hole (SMBH) growth and active galactic nucleus (AGN) feedback at high accretion rates. We investigate the nearby NLSy1 Ton S180 with VLT-MUSE optical integral field spectroscopy to connect its nuclear accretion properties with the spatially resolved ionized gas and host-galaxy kinematics. We modeled the unresolved nuclear spectrum and applied a custom point spread function subtraction to recover the host-galaxy emission on kiloparsec scales. The nuclear spectrum requires a complex permitted-line decomposition and a blueshifted [O III] outflow component. Single-epoch estimators and the stellar velocity dispersion imply black hole masses in the range $\log(M_{\rm BH}/M_\odot) = 6.5 - 7.7$. Combined with the observed luminosity, this implies a dimensionless mass accretion rate of $\dot{M} / \dot{M}_{\rm Edd} = 4.1 - 980$, confirming the extreme accretion regime. The host galaxy shows a circumnuclear ring, an inner elongated structure consistent with a bar, and rotation-dominated gas and stellar kinematics. Simple inflow models do not significantly better reproduce the observed velocity field. We detect a resolved ionized outflow extending about 2 kpc west of the nucleus, with mildly blueshifted velocities (with a maximum of $v_{\rm max} \sim 340$ km s$^{-1}$). Its mass outflow rate is only $\sim 4.2 \times 10^{-4}\,M_\odot\,\mathrm{yr}^{-1}$, whereas the unresolved nuclear outflow reaches $v_{\rm max} \sim 1140$ km s$^{-1}$ and $\dot{M}_{\rm out} > 1.5\,M_\odot\,\mathrm{yr}^{-1}$. This contrast may reflect either weak ionized coupling from nuclear to galactic scales or different episodes of AGN activity over time. These results show that Ton S180 is undergoing rapid SMBH growth, while the observed ionized outflow remains confined to the inner few kiloparsecs and is weak on host-galaxy scales.

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arXiv2026

Optical observations of candidate host galaxies of eight fast X-ray transients

Fast X-ray transients (FXTs) are extragalactic flashes of X-rays with a typical duration of minutes to hours for which a variety of origins has been proposed and observed. To decipher the origin of FXTs, particularly those lacking multi-wavelength counterparts, we aim to understand their energetics and environments. We present deep optical ground-based observations of the positions of eight FXTs in order to try and identify and characterize candidate host galaxies. We use their properties to discriminate between possible progenitor scenarios. We identify candidate host galaxies for Swift~J050400.2+673405, XRT140507, XRT040610, XRT151121, XRT191127 and EP240708a. For each candidate, we infer the spectroscopic or photometric redshift, stellar mass, star formation rate, metallicity and stellar population age by fitting our data with the spectral energy distribution fitting code BAGPIPES. We re-identify XRT191223 as a Galactic stellar flare. For several FXTs, there are multiple candidate host galaxies, which complicates deriving constraints on the origin of the FXT. Assuming association with (one of) those candidates, all are consistent with a (non-)relativistic white dwarf - intermediate mass black hole tidal disruption event (WD-IMBH TDE) and a binary neutron star (BNS) merger. Two are consistent with a supernova shock breakout and only EP240708a with cocoon emission from a long gamma-ray burst. We also discuss the possibility that the host galaxies remain undetected in our observations. We conclude that FXTs detected by Chandra and XMM-Newton are likely to arise from a variety of origins, and we discuss that part of this population differs from FXTs detected by Einstein Probe many of which appear consistent with a collapsar scenario.

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arXiv2026

NOCTURNE. III. Unidentified variable emission in the nuclear regions of PKS 2153-69

Historically, the study of the central regions of Type 1 AGN has been limited by the combination of the host galaxy spectrum with strong emission from the accretion disk and NLR/BLR, which prevented us from accurately probing the galactic and AGN properties in the central regions. Integral field spectroscopy allows us to correct for this effect and study both the unobscured cores of AGN host galaxies as well as the uncontaminated spectra of their central engines with unprecedented precision. Using MUSE WFM observations, in this work, we present a combined method for modelling and subtracting QSO light in type-1 AGN alongside results for one such source, PKS 2153-68 (z=0.028), both jetted and gamma-ray emitting. After separating the host galaxy and AGN spectra, we discuss the discovery of an unresolved and yet-to-be-identified high-velocity ($\sim$25000 km/s) short timescale ($\leq$1 yr) variable emission, unlike anything observed in other variable AGN.

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arXiv2026

Investigating the origin of radio emission in candidate super-Eddington accreting black holes

Recent works show that the radio power of quasars accreting at very high rates can reach surprisingly high values. These studies suggest that this radio emission might originate from star formation, but lack of data leaves open the possibility that they could also contain a jetted active galactic nucleus (AGN). We investigate the origin of the radio emission of a sample of 18 super-Eddington candidates, over a wide range of redshifts. These sources are expected to have extreme radiative output per unit black hole mass, show high-velocity outflows and are therefore thought to be a prime mover of galactic evolution via radiative and mechanical feedback. We present new Karl G. Jansky Very Large Array (VLA) observations at L, C and X-band of these sources, which we combine with observations from the LOw-Frequency ARray (LOFAR) Two-metre Sky Survey (LoTSS) and the Very Large Array Sky Survey (VLASS). We also use optical and IR data to derive estimates of accretion and wind parameters, as well as star formation rates to compare with the ones derived from the radio emission. Based on the radio variability, luminosity, morphology, radio spectral properties, radio vs IR estimates of star formation rate and radio-to-mid IR flux ratio, we find that 7 of our 18 targets are likely to have their radio emission predominantly coming from SF, and 6 from a combination of SF and AGN-related mechanisms, while only three sources indicate a core or jetted AGN only origin for the detected radio emission. This is consistent with previous studies, and supports the prevalence of lower power radio structures associated with star-forming activity rather than relativistic jets in the high Eddington ratio regime. In the same sample, however, we find three sources for which the data suggest a concomitant presence of super-Eddington accretion and relativistic ejections.

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arXiv2025

How similar are narrow-line Seyfert 1 galaxies and high-z type 1 AGN?

The recent observations of highly accreting supermassive black holes (SMBH) at very high redshift ($z>$4) with the James Webb Space Telescope (\textit{JWST}) allowed us to shed light for the very first time on the early evolutionary phases of active galactic nuclei (AGN). Perhaps unsurprisingly, several of the physical properties observed in these new objects, including those known as little red dots (LRDs), are closely reminiscent of the low-mass and high-Eddington AGN in the local Universe, and in particular of the class of narrow-line Seyfert 1 (NLS1) galaxies. However, some differences also emerged, likely due to the radically different evolutionary path and the environment where LRDs and NLS1s live. In this work, we review the multiwavelength properties of local NLS1s and briefly compare them with type 1 AGN found at high-$z$, showing that despite some differences, the study of NLS1s can be extremely useful to better understand the extreme accretion physics of high-$z$ quasars and the early stages of AGN evolution. The goal of this review is to provide the high-z community a handbook to compare their new sources with those already known in the local Universe, and to give the low-z community a starting point to venture in the early phases of AGN evolution.

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arXiv2025

An optical perspective on early-stage AGN with extreme radio flares

In the last decade of Active Galactic Nuclei (AGN) monitoring programs, the Mets\"ahovi Radio Observatory detected multiple times seven powerful flaring narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz. Several hypotheses have been proposed, but the understanding of this unique phenomenon is still far. To look at the case from a different point of view, we performed an emission line analysis of the optical spectra, with the aim of identifying similarities among the sources, that can be in turn possibly tied with the radio behavior. Our data were obtained with the Gran Telescopio Canarias. The results we obtained show that six out of seven sources have typical properties for the NLS1 class, and one of them is an intermediate Seyfert galaxy. We found on average black hole masses above the median value for the class (> 10$^7$ M$_\odot$), and a strong Fe II emission, which could be a proxy for an intense ongoing accretion activity. Although interesting, the characteristics we found are not unusual for these kind of AGN: the optical spectra of our sources do not related with their unique radio properties. Therefore, further multi-wavelength studies will be necessary to narrow the field of hypotheses for this peculiar phenomenon.

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arXiv2024

X-ray properties of two complementary samples of intermediate Seyfert galaxies

We present the X-ray spectral analysis of two complementary sets of intermediate Seyfert galaxies (ISs). Analyzing X-ray data, we estimate the hydrogen abundance $N_H$ and test its connection with the [O III] luminosity acquired from optical observations. The results confirm the conclusions drawn in a previous study concerning the lack of a direct correlation between the obscuration measure ($N_H$) and the intrinsic characteristics of the active nuclei ([O III] luminosity). Instead, we validate the existence of a correlation between the Seyfert type and the $N_H$ parameter, employing a separation threshold of approximately 10$^{22}$ atoms cm$^{-2}$. Simultaneously, our findings align with prior research, corroborating the relationship between X-ray luminosity and the [O III] luminosity.

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arXiv2023

A large jet narrow-line Seyfert 1 galaxy: observations from pc to 100 kpc scales

We present new 1.5-8.5 GHz Very Long Baseline Array (VLBA) observations and 0.32-1.26 GHz Giant Meterwave Radio Telescope (GMRT) observations of J0354-1340, which is the only known radio-quiet (RQ) or radio-intermediate (RI) narrow-line Seyfert 1 galaxy with a 100-kpc two-sided radio jet. A pc-scale one-sided jet in the southeast direction from the core emission is found in the VLBA observations, while the kpc-scale jet observed with Karl G. Jansky Very Large Array (VLA) and GMRT is in the south-north direction. The core spectra on pc and kpc scales are presented in combination with the archival VLASS observations at 3.0 GHz and the VLA C configuration observations at 5.5 GHz. The pc-scale emission dominates the kpc-scale emission above ~ 5 GHz, and the spectrum is inverted due to synchrotron self-absorption. This indicates a compact synchrotron source with a size of ~ 0.04 pc, which is associated with either the jet base or the corona. A sub-kpc scale jet, which is unresolved on scales of ~ 3 arcsec, probably dominates the emission below ~ 5 GHz. Future radio observations can explore the jet structure between the pc and 100 kpc scales, the origin of their direction mismatch, and the pc-scale jet proper motion. It remains to be explored how common such large-scale jets are in RQ or RI AGN.

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arXiv2023

Optical properties of two complementary samples of intermediate Seyfert galaxies

We present preliminary results of the analysis of optical spectra of two complementary samples of Seyfert galaxies. The first sample was extracted from a selection of the 4th Fermi Gamma-ray Large Area Telescope (4FGL) catalog, and consists of 9 $γ$-ray emitting jetted Seyfert galaxies. The second one was extracted from the Swift-BAT AGN Spectroscopic Survey (BASS), and is composed of 38 hard-X ray selected Active Galactic Nuclei (AGN). These two samples are complementary, with the former expected to have smaller viewing angles, while the latter may include objects with larger viewing angles. We measured emission line ratios to investigate whether the behavior of these Seyferts can be explained in terms of obscuration, as suggested by the well-known Unified Model (UM) of AGN, or if there are intrinsic differences due to the presence of jets, outflows, or the evolution. We found no indications of intrinsic differences. The UM remains the most plausible interpretation for these classes of objects even if some results can be challenging for this model.

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arXiv2022

A New Sample of Gamma-Ray Emitting Jetted Active Galactic Nuclei

We considered the fourth catalog of gamma-ray point sources produced by the Fermi Large Area Telescope (LAT) and selected only jetted active galactic nuclei (AGN) or sources with no specific classification, but with a low-frequency counterpart. Our final list is composed of 2980 gamma-ray point sources. We then searched for optical spectra in all the available literature and publicly available databases, to measure redshifts and to confirm or change the original LAT classification. Our final list of gamma-ray emitting jetted AGN is composed of BL Lac Objects (40%), flat-spectrum radio quasars (23%), misaligned AGN (2.8%), narrow-line Seyfert 1, Seyfert, and low-ionization nuclear emission-line region galaxies (1.9%). We also found a significant number of objects changing from one type to another, and vice versa (changing-look AGN, 1.1%). About 30% of gamma-ray sources still have an ambiguous classification or lack one altogether.

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arXiv2022

Jetted narrow-line Seyfert 1 galaxies breaking the jet paradigm -- a comprehensive study of host galaxy morphologies

Narrow-line Seyfert 1 (NLS1) galaxies are unevolved active galactic nuclei (AGN) that exist predominantly in spiral galaxies. However, mostly due to the small number of sources studied, it has been under debate whether also the hosts of jetted NLS1 galaxies, a particular subclass of these sources hosting a relativistic jet, are disk-like, or elliptical, as the hosts of more powerful jetted AGN. We studied the host morphologies of 14 NLS1 galaxies, 11 of which have been detected at 37 GHz indicating that these sources harbour relativistic jets. The J- and Ks-band data used in this study were obtained with the Nordic Optical Telescope (NOT). We performed the photometric decomposition of the host galaxy using the band that gave a better fit, and additionally, created colour maps of all sources that had both a J- and a Ks-band observation. We were able to successfully model 12 sources, nine of which most likely have disk-like morphology. Of the remaining sources, one source could possibly be hosted either in a disk-like or a dwarf galaxy, and in two cases the results are inconclusive. Only one of our sources shows clear signs of interaction, but the colour maps of most of our sources hint at ample dust in the nuclei, possibly indicating earlier minor mergers, that can go unnoticed due to the limited resolution of these observations. Our results further support disk-like galaxies as the predominant host type of jetted NLS1 galaxies. Most importantly, with the number of modelled hosts of jetted NLS1s now exceeding 50, with only a few elliptical hosts, it seems to be safe to conclude that also disk-like galaxies are able to launch and maintain relativistic jets, and that the traditional jet paradigm stating that only massive elliptical galaxies are capable of hosting relativistic jets is severely outdated.

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arXiv2022

Radio spectra of narrow-line Seyfert 1 galaxies observed with ATCA and VLASS

We present radio spectral analyses for a sample of 29 radio-quiet (RQ) and three radio-loud (RL) narrow-line Seyfert 1 galaxies (NLS1s) detected with the Australia Telescope Compact Array at both 5.5 GHz and 9.0 GHz. The sample is characterized by L_bol/L_Edd > 0.15. The radio slopes in 25 of the 29 RQ NLS1s are steep (alpha_5.5-9.0 < -0.5), as found in earlier studies of RQ high L_bol/L_Edd AGN. This steep radio emission may be related to AGN-driven outflows, which are likely more prevalent in high L_bol/L_Edd AGN. In two of the three RL NLS1s, the radio slopes are flat or inverted (alpha_5.5-9.0 > -0.5), indicating a compact optically-thick source, likely a relativistic jet. Archival data at 3.0 GHz, 1.4 GHz, and 0.843 GHz are also compiled, yielding a sample of 17 NLS1s detected in three bands or more. In nine objects, the radio spectra flatten at lower frequencies, with median slopes of alpha_5.5-9.0 = -1.21 +/- 0.17, flattening to alpha_3.0-5.5 = -0.97 +/- 0.27, and to alpha_1.4-3.0 = -0.63 +/- 0.16. A parabolic fit suggests a median spectral turnover of ~ 1 GHz, which implies synchrotron self-absorption in a source with a size of only a fraction of 1 pc, possibly a compact wind or a weak jet. Two objects show significant spectral steepening to alpha < -2 above 3 GHz or 5 GHz, which may suggest relic emission from past ejection of radio emitting plasma, of the order of a few years to a few decades ago. Finally, two objects present a single spectral slope consistent with star-forming activity.

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arXiv2021

Optical singly-ionized iron emission in radio-quiet and relativistically jetted active galactic nuclei

The issue of the difference between optical and UV properties of radio-quiet and radio-loud (relativistically "jetted") active galactic nuclei (AGN) is a long standing one, related to the fundamental question of why a minority of powerful AGN possess strong radio emission due to relativistic ejections. This paper examines a particular aspect: the singly-ionized iron emission in the spectral range 4400 -- 5600 A, where the prominent HI H$β$ and [OIII] 4959, 5007 lines are also observed. We present a detailed comparison of the relative intensity of Fe II multiplets in the spectral types of the quasar main sequence where most jetted sources are found, and afterwards discuss radio-loud narrow-line Seyfert 1 (NLSy1) nuclei with $γ$-ray detection and with prominent Fe II emission. An Fe II template based on I Zw 1 provides an accurate representation of the optical Fe II emission for RQ and, with some caveats, also for RL sources. CLOUDY photoionization simulations indicate that the observed spectral energy distribution can account for the modest Fe II emission observed in composite radio-loud spectra. However, spectral energy differences alone cannot account for the stronger Fe II emission observed in radio-quiet sources, for similar physical parameters. As for RL NLSy1s, they do not seem to behave like other RL sources, likely because of their different physical properties that could be ultimately associated with a higher Eddington ratio.

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arXiv2021

Peaked sources and narrow-line Seyfert 1s: a love story

The first similarities between peaked sources (PS) and narrow-line Seyfert 1 (NLS1) galaxies were noticed already twenty years ago. Nowadays, it is known that several sources can share both classifications, and that part of the parent population of $γ$-ray emitting NLS1s could be hiding among PS. In this brief review, we describe how and why this orientation-based unification was developed. We also show how the recent discovery of absorbed radio jets in NLS1s, basically invisible at frequencies below 10 GHz, could impact our knowledge of PS and, in particular, render the widely used radio-loudness parameter obsolete.

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arXiv2021

Unravelling the origin of extended radio emission in narrow-line Seyfert 1 galaxies with the JVLA

Narrow-line Seyfert 1 (NLS1) galaxies are believed to be active galactic nuclei (AGN) in the early stages of their evolution. Some dozens of them have been found to host relativistic jets, whilst the majority has not even been detected in radio, emphasising the heterogeneity of the class in this band. In this paper, our aim is to determine the predominant source of radio emission in a sample of 44 NLS1s, selected based on their extended kpc-scale radio morphologies at 5.2 GHz. We accomplish this by analysing their spatially resolved radio spectral index maps, centred at 5.2 GHz. In addition, we utilise several diagnostics based on mid-infrared emission to estimate the star formation activity of their host galaxies. These data are complemented by archival data to draw a more complete picture of each source. We find an extraordinary diversity among our sample. Approximately equal fractions of our sources can be identified as AGN-dominated, composite, and host-dominated. Among the AGN-dominated sources are a few NLS1s with very extended jets, reaching distances of tens of kpc from the nucleus. One of these, J0814+5609, hosts the most extended jets found in an NLS1 so far. We also identify five NLS1s that could be classified as compact steep-spectrum sources. We further conclude that due to the variety seen in NLS1s simple proxies, such as the star formation diagnostics also employed in this paper, and the radio loudness parameter, are not ideal tools for characterising NLS1s. We emphasise the necessity of examining NLS1s as individuals, instead of making assumptions based on their classification. When these issues are properly taken into account, NLS1s offer an exceptional environment to study the interplay of the host galaxy and several AGN-related phenomena, such as jets and outflows. [Abstract abridged.]

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arXiv2021

Narrow-line Seyfert 1 galaxies with absorbed jets -- insights from radio spectral index maps

Narrow-line Seyfert 1 (NLS1) galaxies are active galactic nuclei (AGN) believed to be in the early stages of their evolution. A fraction of them have been found to host relativistic jets. Due to the lack of large-scale diffuse radio emission they are believed to be experiencing one of their first activity cycles, and can offer us an opportunity to study the early evolution of more powerful AGN, such as radio galaxies and flat-spectrum radio quasars. Recently, a group of intriguing jetted NLS1s was discovered: based on high radio frequency data they host relativistic jets, but in the JVLA observations they all showed steep radio spectra at least up to 9.0~GHz, indicating very strong absorption at these frequencies. In this paper we study a subset of these sources in detail by employing spatially resolved radio spectral index maps at central frequencies of 1.6, 5.2, and 9.0~GHz. With spectral index maps we can disentangle the different radio emission components over the radio-emitting region, and get insights into the production mechanisms of radio emission. In addition, we study their host galaxies in relation to the radio emission to investigate if the host can provide us additional information regarding the origin of the radio emission, or the launching mechanism of the jets. It is fascinating how different the sources studied are, and certainly more, especially wide frequency-range, and high-resolution observations will be needed to understand their history and current properties, such as the reason behind the extraordinary radio spectra.

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arXiv2021

Jet-induced feedback in the [O III] lines of early evolution stage active galactic nuclei

It is well known that active galactic nuclei (AGN) show various forms of interaction with their host galaxy, in a number of phenomena generally called AGN feedback. In particular, the relativistic plasma jets launched by a fraction of AGN can strongly affect their environment. We present here a study of the [O III] $λλ$4959,5007 lines in a diverse sample of early evolution stage AGN -- specifically narrow-line Seyfert 1 galaxies. Radio imaging observations of all of the sources enable a division to jetted and non-jetted sources, and exploiting this we show that the ionized gas properties are significantly influenced by the presence of the jets, as we often find the [O III] lines (blue-)shifted with respect to their restframe wavelength. We also show how the radio morphology and the radio spectral index do not seem to play a role in the origin of the [O III] shifts, thus suggesting that the source inclination is not relevant to the lines displacement. We do not find a strong relation between the [O III] line properties and the bolometric luminosity, suggesting that within our sample radiatively driven outflows do not seem to have a significant contribution to the [O III] line kinematics. We finally suggest that [O~ III] shifts may be a good proxy to identify the presence of relativistic jets. Additional studies, especially with integral-field spectroscopy, will provide a deeper insight into the relation between jets and their environment in early evolution stage AGN.

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arXiv2020

SN 2017gci: a nearby Type I Superluminous Supernova with a bumpy tail

We present and discuss the optical spectro-photometric observations of the nearby (z=0.087) Type I superluminous supernova (SLSN I) SN 2017gci, whose peak K-corrected absolute magnitude reaches Mg=-21.5 mag. Its photometric and spectroscopic evolution includes features of both slow and of fast evolving SLSN I, thus favoring a continuum distribution between the two SLSN-I subclasses. In particular, similarly to other SLSNe I, the multi-band light curves of SN 2017gci show two rebrightenings at about 103 and 142 days after the maximum light. Interestingly, this broadly agrees with a broad emission feature emerging around 6520 A after 51 days from the maximum light, which is followed by a sharp knee in the light curve. If we interpret this feature as Halpha, this could support the fact that the bumps are the signature of late interactions of the ejecta with a (hydrogen rich) circumstellar material. Then we fitted magnetar and CSM-interaction powered synthetic light curves onto the bolometric one of SN 2017gci. In the magnetar case, the fit suggests a polar magnetic field Bp = 6 x 1e14 G, an initial period of the magnetar Pinitial=2.8 ms, an ejecta mass Mejecta=9 Msun and an ejecta opacity k = 0.08 cm g^{-1} . A CSM interaction scenario would imply a CSM mass of 5 Msun and an ejecta mass of 12 Msun. Finally, the nebular spectrum of phase 187 days was modeled, deriving a mass of 10 Msun for the ejecta. Our models suggest that either a magnetar or CSM interaction might be the power sources for SN 2017gci and that its progenitor was a massive (40 Msun) star.

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