On the semi-dynamical reflection equation: solutions and structure matrices

Explicit solutions of the non-constant semi-dynamical reflection equation are constructed, together with suitable parametrizations of their structure matrices. Considering the semi-dynamical reflection equation with rational non-constant Arutyunov-Chekhov-Frolov structure matrices, and a specific meromorphic ansatz, it is found that only two sets of the previously found constant solutions are extendible to the non-constant case. In order to simplify future constructions of spin-chain Hamiltonians, a parametrization procedure is applied explicitly to all elements of the semi-dynamical reflection equation available. Interesting expressions for `twists' and R-matrices entering the parametrization procedure are found. In particular, some expressions for the R-matrices seem to appear here for the first time. In addition, a new set of consistent structure matrices for the semi-dynamical reflection equation is obtained.Comment: typos corrected and some comments adde

Clonal chromosomal mosaicism and loss of chromosome Y in elderly men increase vulnerability for SARS-CoV-2

The pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2, COVID-19) had an estimated overall case fatality ratio of 1.38% (pre-vaccination), being 53% higher in males and increasing exponentially with age. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, we found 133 cases (1.42%) with detectable clonal mosaicism for chromosome alterations (mCA) and 226 males (5.08%) with acquired loss of chromosome Y (LOY). Individuals with clonal mosaic events (mCA and/or LOY) showed a 54% increase in the risk of COVID-19 lethality. LOY is associated with transcriptomic biomarkers of immune dysfunction, pro-coagulation activity and cardiovascular risk. Interferon-induced genes involved in the initial immune response to SARS-CoV-2 are also down-regulated in LOY. Thus, mCA and LOY underlie at least part of the sex-biased severity and mortality of COVID-19 in aging patients. Given its potential therapeutic and prognostic relevance, evaluation of clonal mosaicism should be implemented as biomarker of COVID-19 severity in elderly people. Among 9578 individuals diagnosed with COVID-19 in the SCOURGE study, individuals with clonal mosaic events (clonal mosaicism for chromosome alterations and/or loss of chromosome Y) showed an increased risk of COVID-19 lethality

Spectral synthesis of the nuclear regions of Seyfert 2 and radio galaxies

We present the results of an optical spectral synthesis analysis for the nuclei of 20 Seyfert 2 and four radio galaxies, using a base of stellar population templates of different ages and metallicities and a power-law continuum. Compared with the stellar population of elliptical galaxies, we find that Seyfert 2s usually have a smaller contribution from old metal-rich stars (age 10 Gyr, Z ≥ Z̛), and a larger contribution from stars with ages of 100 Myr. We also find that the contributions from stars with ages ≤ 10 Myr and from a power-law continuum are small, rarely exceeding 5 per cent. These results show that the general assumption of elliptical galaxies as stellar population templates for these objects is incorrect, also implying that the excess blue continuum frequently found in their nuclear spectra is probably due to this template mismatch.We find a considerable contribution from 100-Myr-old stars (~~5 per cent), which can be interpreted from the point of view of models where the fuelling of the AGN is carried out by interactions/mergers

The nature of the optical light in Seyfert 2 galaxies with polarized continua

We investigate the nature of the optical continuum and stellar population in the central kiloparsec of the Seyfert 2 galaxies Mrk 348, Mrk 573, NGC 1358, and Mrk 1210 using high signal-to-noise−ratio, long-slit spectra obtained along the radio axis or along the extended high-excitation emission. These four galaxies are known to have polarized continua, including polarized broad lines in Mrk 348 and Mrk 1210, and previous studies indicate featureless continua contributions in the 20-50% range at λ ≈ 5500 Å . Nevertheless, our measurements of the equivalent widths of absorption lines and continuum ratios as a function of distance from the nuclei show no decrease of the equivalent widths (i.e., no dilution) nor blueing of the spectrum toward the nucleus, as expected if a blue, featureless continuum was present at the nucleus in the above proportions. We investigate one possibility to account for the lack of dilution : that the stellar population at the nucleus is the same as that from the surrounding bulge and dominates the nuclear light. By comparing the nuclear and the extranuclear spectra of each galaxy, we conclude that this hypothesis works for Mrk 348, NGC 1358, and Mrk 1210, for which we Ðnd stellar population contributions at the nucleus larger than 90% at all wavelengths. Our approach di†ers from that adopted in previous studies, where an elliptical galaxy template is used to represent the stellar population of the nucleus. Although the latter may be valid for some galaxies−as, for example, Mrk 573−in several cases the stellar population may be different from that of an elliptical galaxy. We find that a larger stellar population contribution to the nuclear spectra can play the role of the “second featureless continuum" source inferred from previous studies. In particular, stellar population synthesis shows that the nuclear regions of Mrk 348 and Mrk 1210 have important contributions of young to intermediate-age stars (0−10 8 yr) not present in templates of elliptical galaxies. In the case of Mrk 1210, this is further con- formed by the detection of a “Wolf-Rayet feature" in the nuclear emission-line spectrum

The stellar content of active galaxies

We present the results of a long-slit spectroscopic study of 38 active and four normal galaxies. Stellar absorption features, continuum colours and their radial variations are analysed in an effort to characterize the stellar population in these galaxies and detect the presence of a featureless continuum underlying the starlight spectral component. Spatial variations of the equivalent widths of conspicuous absorption lines and continuum colours are detected in most galaxies. Star-forming rings, in particular, leave clear fingerprints in the equivalent widths and colour profiles. We find that the stellar populations in the inner regions of active galaxies present a variety of characteristics, and cannot be represented by a single starlight template. Dilution of the stellar lines by an underlying featureless continuum is detected in most broadlined objects, but little or no dilution is found for most of the 20 type 2 Seyferts in the sample. Colour gradients are also ubiquitous. In particular, all but one of the observed Seyfert 2s are redder at the nucleus than in its immediate vicinity. Possible consequences of these findings are briefly outlined

Empirical diagnostics of the starburst-AGN connection

We examine a representative sample of 35 Seyfert 2 nuclei. Previous work has shown that nearly half (15) of these nuclei show the direct (but difficult to detect) spectroscopic signature at optical/near-UV wavelengths of the hot massive stars that power circumnuclear starbursts. In the present paper we examine a variety of more easily measured quantities for this sample, such as the equivalent widths of strong absorption features, continuum colors, emission line equivalent widths, emission line ratios and proÐles, far-IR luminosities, and near-UV surface brightness. We compare the composite starburst + Seyfert 2 nuclei to "pure" Seyfert 2 nuclei, Starburst galaxies, and normal galactic nuclei. Our goals are to verify whether the easily measured properties of the composite nuclei are consistent with the expected impact of a starburst and to investigate alternative less demanding methods to infer the presence of starbursts in Seyfert 2 nuclei, applicable to larger or more distant samples. We show that starbursts do indeed leave clear and easily quantiÐable imprints on the near-UV to optical continuum and emission line properties of Seyfert 2's. Composite starburst + Seyfert 2 systems can be recognized by: (1) a strong "featureless continuum" (FC), which dilutes the Ca II K line from old stars in the host's bulge to an equivalent width WK~10 10 Lʘ; (5) high near-UV surface brightness (~10 3 Lʘ pc-²). These characteristics are all consistent with the expected impact of circumnuclear starbursts on the observed properties of Seyfert 2's. Furthermore, they oer alternative empirical diagnostics of the presence of circumnuclear starbursts from a few easily measured quantities

The obscuring starburst of NGC 6221 and implications for the hard x-ray background

We present NGC 6221 as a case study of "X-ray-loud composite galaxies", which appear similar to starbursts at optical wavelengths and resemble traditional active galactic nuclei in X-rays. The net optical spectrum of NGC 6221 is properly characterized as a starburst galaxy, but in X-rays, NGC 6221 is similar to Seyfert 1 galaxies, exhibiting a power-law continuum spectrum, a broad Fe Kα line, and continuum variability on timescales of days and years. High-resolution images reveal that the detected active nucleus is relatively weak, not only at optical, but also at near-infrared wavelengths. An obscuring starburst, in which the interstellar gas and dust associated with the starburst conceal the active nucleus, accounts for these peculiar features. We demonstrate quantitatively that obscuration by column density NH=10 22 cm-² combined with relatively weak intrinsic nuclear activity can produce an optical spectrum that is characteristic of the surrounding starburst alone. While optical surveys would not identify the active nuclei that make these galaxies significant X-ray sources, such galaxies may, in fact, be important contributors to the X-ray background

Gemini/GMOS integral field unit stellar kinematics of the nuclear region of six nearby active galaxies

We present 2D mapping of the stellar velocity field within the inner 5 arcsec of six nearby active galaxies, using spectra obtained with the Integral Field Unit (IFU) of the Gemini Multi-Object Spectrograph instrument at the Gemini North telescope. The sampling of the observations is 0.2 arcsec, corresponding at the galaxies to spatial extents ranging from 10 to 30 pc. The spatial resolution range from 20 to about 180 pc, and the observed field of view covers a few hundred parsecs around the nuclei. The Ca II triplet absorption features at ≈ 8500Å were used to measure the stellar radial velocities and velocity dispersions. The radial velocity fields are dominated by rotation in all galaxies. A simple kinematical model assuming a purely rotating system with circular orbits in a plane was fitted to the radial velocity data. The turnover of the rotation curve is at only ≈ 50 pc for NGC4051 and between 200 and 700 pc for the other five galaxies. The velocity dispersion (σ) maps show the largest values (100 ≥ σ ≥ 150 km s-ˡ) at the centre. In the cases of NGC2273 and 3227, there is a decrease to σ ≈ 70–80 km s-ˡ at ≈ 200–300 pc from the nucleus, delineating partial rings of low-σ values. A similar broken ring seems to be present at ≈ 400 pc from the nucleus also in NGC4593. We interpret these low-σ rings as traces of recently formed stars that partially keep the cold kinematics of the original gas from which they have formed. In NGC3516 there is a decrease of σ outwards with the steepest gradient observed along the direction of the galaxy major axis, where σ reaches ≈ 80–90 km s-ˡ at ≈ 400 pc from the nucleus. The main novelty of the present work is the unprecedented spatial resolution reached by a 2D study of stellar kinematics of Seyfert galaxies using an IFU. The few similar IFU studies available in the literature for Seyfert galaxies have a much poorer spatial resolution and/or are restricted to the study of emission-line kinematics

Gemini/GMOS IFU gas velocity 'tomography' of the narrow line region of nearby active galaxies

We present two-dimensional (2D) mapping of the gas velocity field of the inner few hundred parsecs of six nearby active galaxies, using spectra obtained with the integral field unit of the Gemini Multi-Object Spectrograph instrument at the Gemini North telescope. In our previous paper, we reported the 2D mapping of the stellar kinematics extracted from the calcium triplet absorption lines. In this paper, we use the [S III] λ9069 emission line to obtain the flux distribution and kinematics of the gas in the narrow-line region (NLR). The gas emission is extended by a few hundred parsecs and its kinematics are dominated by rotation in the galaxy plane. Subtraction of the rotation component reveals outflows along the NLR which show spatial correlation with radio structures seen in Very Large Array radio 3.6 and 20 cm flux images, suggesting that the radio jet is pushing the circumnuclear interstellar medium. This interpretation is also supported by the observation of high-velocity dispersion (σ ≥ 500 km s-ˡ) structures in association with the outflowing gas. The gas outflows and radio jets are oriented at random angles relative to the galaxy major axis, indicating that they are not launched perpendicularly to the galaxy plane. Slicing the emission-line profiles into velocity channels, we create maps of the NLR gas distribution at different radial velocities. In at least half of our sample, the highest velocities are observed close to the nucleus suggesting that the emitting gas is decelerating outwards, from projected blueshifts exceeding 400 km s-ˡ to values of 100–200 km s-ˡ at 100–200 pc from the nucleus. We have estimated mass outflow rates in the NLR of ≈1 to 50 × 10-³Mʘ yr-ˡ, which are ≈10–20 times the accretion rate necessary to feed the active nucleus. The kinetic energy of the ouflow is estimated to be 4–5 orders of magnitude smaller than the bolometric luminosity. Assuming kinetic energy transfer between the radio jet and the NLR outflows, the mass ejection rate in the radio jet is 5–6 orders of magnitude smaller than the mass accretion rate necessary to feed the nuclear supermassive black hole