AGN feedback in action in the molecular gas ring of the Seyfert galaxy NGC7172

We present new ALMA observations of the CO(3-2) transition and 854micron continuum at 0.06-0.3" resolution, together with new VLT/SINFONI observations of NGC7172. This is a luminous (bolometric luminosity of ~10^44 erg/s) Seyfert galaxy that belongs to the Galaxy Activity, Torus, and Outflow Survey (GATOS). The CO(3-2) observations reveal the presence of a highly inclined cold molecular gas ring with an approximate radius of 3-4"~540-720 pc, which is likely associated with an inner Lindblad resonance of a putative stellar bar. There are noncircular motions in the VLT/SINFONI [SiVI]1.96micron and H2 at 2.12micron, and ALMA CO(3-2) velocity fields. After subtracting the stellar velocity field, we detected [SiVI] blueshifted velocities of a few hundred km/s to the south of the AGN. They trace outflowing ionized gas outside the plane of the galaxy and out to projected distances of ~200 pc. The CO(3-2) position-velocity diagram along the kinematic minor axis displays noncircular motions with observed velocities of up to ~150 km/s. Assuming that these are taking place in the disk of the galaxy, the observed velocity signs imply that the molecular gas ring is not only rotating but also outflowing. We derived an integrated cold molecular gas mass outflow rate of ~40 Msun/yr for the ring. Using the 854micron map, we resolved a 32 pc radius torus with a gas mass of 8x10^5 Msun. These torus properties are similar to other Seyfert galaxies in the GATOS sample. We measured a decreased cold molecular gas concentration in the nuclear-torus region relative to the circumnuclear region when compared to other less luminous Seyfert galaxies. We conclude that the effects of AGN feedback in NGC7172, which are likely caused by the AGN wind and/or the moderate luminosity radio jet, are seen as a large-scale outflowing molecular gas ring and accompanying redistribution of molecular gas in the nuclear regions.Comment: Accepted for publication to A&

The far-infrared spectroscopic surveyor (FIRSS)

We are standing at the crossroads of powerful new facilities emerging in the next decade on the ground and in space like ELT, SKA, JWST, and Athena. Turning the narrative of the star formation potential of galaxies into a quantitative theory will provide answers to many outstanding questions in astrophysics, from the formation of planets to the evolution of galaxies and the origin of heavy elements. To achieve this goal, there is an urgent need for a dedicated space-borne, far-infrared spectroscopic facility capable of delivering, for the first time, large scale, high spectral resolution (velocity resolved) multiwavelength studies of the chemistry and dynamics of the ISM of our own Milky Way and nearby galaxies. The Far Infrared Spectroscopic Surveyor (FIRSS) fulfills these requirements and by exploiting the legacy of recent photometric surveys it seizes the opportunity to shed light on the fundamental building processes of our Universe

Observations of the Crab Nebula and Pulsar with the Large-Sized Telescope Prototype of the Cherenkov Telescope Array

CTA (Cherenkov Telescope Array) is the next generation ground-based observatory for gamma-ray astronomy at very-high energies. The Large-Sized Telescope prototype (\LST{}) is located at the Northern site of CTA, on the Canary Island of La Palma. LSTs are designed to provide optimal performance in the lowest part of the energy range covered by CTA, down to $\simeq 20$ GeV. \LST{} started performing astronomical observations in November 2019, during its commissioning phase, and it has been taking data since then. We present the first \LST{} observations of the Crab Nebula, the standard candle of very-high energy gamma-ray astronomy, and use them, together with simulations, to assess the basic performance parameters of the telescope. The data sample consists of around 36 hours of observations at low zenith angles collected between November 2020 and March 2022. \LST{} has reached the expected performance during its commissioning period - only a minor adjustment of the preexisting simulations was needed to match the telescope behavior. The energy threshold at trigger level is estimated to be around 20 GeV, rising to $\simeq 30$ GeV after data analysis. Performance parameters depend strongly on energy, and on the strength of the gamma-ray selection cuts in the analysis: angular resolution ranges from 0.12 to 0.40 degrees, and energy resolution from 15 to 50\%. Flux sensitivity is around 1.1\% of the Crab Nebula flux above 250 GeV for a 50-h observation (12\% for 30 minutes). The spectral energy distribution (in the 0.03 - 30 TeV range) and the light curve obtained for the Crab Nebula agree with previous measurements, considering statistical and systematic uncertainties. A clear periodic signal is also detected from the pulsar at the center of the Nebula.Comment: Submitted to Ap

Multiwavelength study of the galactic PeVatron candidate LHAASO J2108+5157

Context. Several new ultrahigh-energy (UHE) γ-ray sources have recently been discovered by the Large High Altitude Air Shower Observatory (LHAASO) collaboration. These represent a step forward in the search for the so-called Galactic PeVatrons, the enigmatic sources of the Galactic cosmic rays up to PeV energies. However, it has been shown that multi-TeV γ-ray emission does not necessarily prove the existence of a hadronic accelerator in the source; indeed this emission could also be explained as inverse Compton scattering from electrons in a radiation-dominated environment. A clear distinction between the two major emission mechanisms would only be made possible by taking into account multi-wavelength data and detailed morphology of the source. Aims. We aim to understand the nature of the unidentified source LHAASO J2108+5157, which is one of the few known UHE sources with no very high-energy (VHE) counterpart. Methods. We observed LHAASO J2108+5157 in the X-ray band with XMM-Newton in 2021 for a total of 3.8 hours and at TeV energies with the Large-Sized Telescope prototype (LST-1), yielding 49 hours of good-quality data. In addition, we analyzed 12 years of Fermi-LAT data, to better constrain emission of its high-energy (HE) counterpart 4FGL J2108.0+5155. We used naima and jetset software packages to examine the leptonic and hadronic scenario of the multi-wavelength emission of the source. Results. We found an excess (3.7σ) in the LST-1 data at energies E > 3 TeV. Further analysis of the whole LST-1 energy range, assuming a point-like source, resulted in a hint (2.2σ) of hard emission, which can be described with a single power law with a photon index of Σ = 1.6 ± 0.2 the range of 0.3 - 100 TeV. We did not find any significant extended emission that could be related to a supernova remnant (SNR) or pulsar wind nebula (PWN) in the XMM-Newton data, which puts strong constraints on possible synchrotron emission of relativistic electrons. We revealed a new potential hard source in Fermi-LAT data with a significance of 4σ and a photon index of Σ = 1.9 ± 0.2, which is not spatially correlated with LHAASO J2108+5157, but including it in the source model we were able to improve spectral representation of the HE counterpart 4FGL J2108.0+5155. Conclusions. The LST-1 and LHAASO observations can be explained as inverse Compton-dominated leptonic emission of relativistic electrons with a cutoff energy of 100-30+70 TeV. The low magnetic field in the source imposed by the X-ray upper limits on synchrotron emission is compatible with a hypothesis of a PWN or a TeV halo. Furthermore, the spectral properties of the HE counterpart are consistent with a Geminga-like pulsar, which would be able to power the VHE-UHE emission. Nevertheless, the lack of a pulsar in the neighborhood of the UHE source is a challenge to the PWN/TeV-halo scenario. The UHE γ rays can also be explained as π0 decay-dominated hadronic emission due to interaction of relativistic protons with one of the two known molecular clouds in the direction of the source. Indeed, the hard spectrum in the LST-1 band is compatible with protons escaping a shock around a middle-aged SNR because of their high low-energy cut-off, but the origin of the HE γ-ray emission remains an open question

Probing computational methodologies in predicting mid-infrared spectra for large polycyclic aromatic hydrocarbons

We extend the prediction of vibrational spectra to large sized polycyclic aromatic hydrocarbon (PAH) molecules comprising up to ∼1500 carbon atoms by evaluating the efficiency of several computational chemistry methodologies. We employ classical mechanics methods (Amber and Gaff) with improved atomic point charges, semi-empirical (PM3, and density functional tight binding), and density functional theory (B3LYP) and conduct global optimizations and frequency calculations in order to investigate the impact of PAH size on the vibrational band positions. We primarily focus on the following mid-infrared emission bands 3.3, 6.2, 7.7, 8.6, 11.3, 12.7, and 17.0 μm. We developed a general Frequency Scaling Function (⁠FSF⁠) to shift the bands and to provide a systematic comparison versus the three methods for each PAH. We first validate this procedure on IR scaled spectra from the NASA Ames PAH Database, and extend it to new large PAHs. We show that when the FSF is applied to the Amber and Gaff IR spectra, an agreement between the normal mode peak positions with those inferred from the B3LYP/4-31G model chemistry is achieved. As calculations become time intensive for large sized molecules Nc > 450, this proposed methodology has advantages. The FSF has enabled extending the investigations to large PAHs where we clearly see the emergence of the 17.0 μm feature, and the weakening of the 3.3 μm one. We finally investigate the trends in the 3.3 μm/17.0 μm PAH band ratio as a function of PAH size and its response following the exposure to fields of varying radiation intensities

The nuclear and extended mir-infrared emission of Seyfert galaxies

We present subarcsecond resolution mid-infrared (MIR) images obtained with 8-10 m-class ground-based telescopes of a complete volume-limited (DL<40 pc) sample of 24 Seyfert galaxies selected from the Swift/BAT nine month Catalog. We use those MIR images to study the nuclear and circumnuclear emission of the galaxies. Using different methods to classify the MIR morphologies on scales of ~200 pc, we found that the majority of the galaxies (75-79%) are extended or possibly extended and 21-25 % are point-like. In general, we find that galaxies with larger inclinations show more extended morphologies than face-on galaxies, and we do not find significant differences between the morphologies of Sy1 and Sy2. This extended emission is weak and compact and it represents ~30% of the total MIR emission of the galaxies in the sample. We obtain nuclear and circumnuclear MIR fluxes to investigate their correlation with different AGN and star formation indicators. We find that the nuclear MIR emission (inner ~70 pc) is strongly correlated with the X-ray emission (the harder the X-rays the better the correlation) and with the [O IV]λ25.89 micron emission line. We find the same results, although with more scatter, for the circumnuclear MIR emission. This indicates that AGN photoionization is the dominant source of excitation of the nuclear and circumnuclear MIR emission

The properties of polycyclic aromatic hydrocarbons in galaxies: constraints on PAH sizes, charge and radiation fields

Based on theoretical spectra computed using Density Functional Theory we study the properties of polycyclic aromatic hydrocarbons (PAH). In particular using bin-average spectra of PAH molecules with varying number of carbons we investigate how the intensity of the mid-infrared emission bands, 3.3, 6.2, 7.7, and 11.3 $\mu$m, respond to changes in the number of carbons, charge of the molecule, and the hardness of the radiation field that impinges the molecule. We confirm that the 6.2/7.7 band ratio is a good predictor for the size of the PAH molecule (based on the number of carbons present). We also investigate the efficacy of the 11.3/3.3 ratio to trace the size of PAH molecules and note the dependence of this ratio on the hardness of the radiation field. While the ratio can potentially also be used to trace PAH molecular size, a better understanding of the impact of the underlying radiation field on the 3.3 $\mu$m feature and the effect of the extinction on the ratio should be evaluated. The newly developed diagnostics are compared to band ratios measured in a variety of galaxies observed with the Infrared Spectrograph on board the Spitzer Space Telescope. We demonstrate that the band ratios can be used to probe the conditions of the interstellar medium in galaxies and differentiate between environments encountered in normal star forming galaxies and active galactic nuclei. Our work highlights the immense potential that PAH observations with the James Webb Space Telescope will have on our understanding of the PAH emission itself and of the physical conditions in galaxies near and far

AGN feedback in the Local Universe: Multiphase outflow of the Seyfert galaxy NGC 5506

\ua9 2024 EDP Sciences. All rights reserved.We present new optical GTC/MEGARA seeing-limited (0.9″) integral-field observations of NGC 5506, together with ALMA observations of the CO(3 - 2) transition at a 0.2″ ( ~25 pc) resolution. NGC 5506 is a luminous (bolometric luminosity of ~1044 erg s-1) nearby (26 Mpc) Seyfert galaxy, part of the Galaxy Activity, Torus, and Outflow Survey (GATOS). We modelled the CO(3 - 2) kinematics with 3DBAROLO, revealing a rotating and outflowing cold gas ring within the central 1.2 kpc. We derived an integrated cold molecular gas mass outflow rate for the ring of ~8 M⊙ yr-1. We fitted the optical emission lines with a maximum of two Gaussian components to separate rotation from non-circular motions. We detected high [OIII]λ5007 projected velocities (up to ~1000 km s-1) at the active galactic nucleus (AGN) position, decreasing with radius to an average ~330 km s-1 around ~350 pc. We also modelled the [OIII] gas kinematics with a non-parametric method, estimating the ionisation parameter and electron density in every spaxel, from which we derived an ionised mass outflow rate of 0.076 M⊙ yr-1 within the central 1.2 kpc. Regions of high CO(3 - 2) velocity dispersion, extending to projected distances of ~350 pc from the AGN, appear to be the result from the interaction of the AGN wind with molecular gas in the galaxy\u27s disc. Additionally, we find the ionised outflow to spatially correlate with radio and soft X-ray emission in the central kiloparsec. We conclude that the effects of AGN feedback in NGC 5506 manifest as a large-scale ionised wind interacting with the molecular disc, resulting in outflows extending to radial distances of 610 pc