Panoràmica

• Guerra i escriptura. Ressenya del llibre de Paul Preston "Idealistas bajo las balas: corresponsales extranjeros en la Guerra de España", a càrrec de David Caminada • Del disseny gràfic a la direcció d’art. Una visita guiada. Ressenya del llibre de Josep Rom "Sobre la direcció d’art", a càrrec de David Tetilla • Mirades crítiques de la realitat. Ressenya del llibre de Josetxo Cerdán i Casimiro Torreiro "Al otro lado de la ficción: trece documentalistas españoles contemporáneos", a càrrec de Magdalena Sellés • Propostes per a un retorn de la primavera política. Ressenya del llibre coordinat per Michel Wieviorka "La primavera de la política". Idees per acabar amb el declivi de la democràcia tradicional, a càrrec de Joaquim Colominas • An Impressive Body of Work. Ressenya del llibre d’Israel Paredes "Imágenes del cuerpo", a càrrec de Catherine Otey • Els cafès, una institució europea. Ressenya del llibre d’Antonio Martí Monterde "Poética del café", a càrrec de Jordi Berrio • L’economia a la televisió-espectacle. Ressenya del llibre de Lourdes Ballarín "La informació econòmica a la televisió, un espectacle que costa de veure", a càrrec de Iolanda Tortajada • En Met i el Comissariat de Propaganda. Ressenya del llibre d’Enric Pujol "Jaume Miravitlles i el Comissariat de Propaganda de la Generalitat de Catalunya (1936-1939)", a càrrec de Queralt Solé • Las palabras como símbolos de experiencias emocionales. Ressenya del llibre de Joan Sabaté i Ester Franquesa "Màrqueting lingüístic i consum", a càrrec de Josep M. de Ricarte • La deconstrucció d’un mite. Ressenya del llibre d’Enric Vila "Lluís Companys. La veritat no necessita màrtirs", a càrrec de Laura Ruano • El model educatiu de la ciutat de Vic. Ressenya dels llibres de Jordi Busquet i Alfons Medina "Societat i ensenyament a Vic. Els reptes educatius. Estudi sociològic sobre la percepció de l’educació a la ciutat de Vic", a càrrec de Sonia Ballan

Obscuration beyond the nucleus: infrared quasars can be buried in extreme compact starbursts

In the standard quasar model, the accretion disc obscuration is due to the canonical dusty torus. Here, we argue that a substantial part of the quasar obscuration can come from the interstellar medium (ISM) when the quasars are embedded in compact starbursts. We use an obscuration-unbiased sample of 578 infrared (IR) quasars at z ≈ 1–3 and archival Atacama Large Millimetre/submillimetre Array submillimetre host galaxy sizes to investigate the ISM contribution to the quasar obscuration. We calculate star formation rates (SFR) and ISM column densities for the IR quasars and a control sample of submillimetre galaxies (SMGs) not hosting quasar activity and show that: (1) the quasar obscured fraction is constant up to SFR ≈ 300 M ☉ yr −1, and then increases towards higher SFR, suggesting that the ISM obscuration plays a significant role in starburst host galaxies, and (2) at SFR ≳ 300 M ☉ yr −1, the SMGs and IR quasars have similarly compact submillimetre sizes (R e ≈ 0.5–3 kpc) and consequently, the ISM can heavily obscure the quasar, even reaching Compton-thick (N H &gt; 10 24 cm −2) levels in extreme cases. Based on our results, we infer that ≈10–30 per cent of the IR quasars with SFR ≳ 300 M ☉ yr −1 are obscured solely by the ISM.</p

Obscuration beyond the nucleus: infrared quasars can be buried in extreme compact starbursts

In the standard quasar model, the accretion disk obscuration is due to the canonical dusty torus. Here, we argue that a substantial part of the quasar obscuration can come from the interstellar medium (ISM) when the quasars are embedded in compact starbursts. We use an obscuration-unbiased sample of 578 infrared (IR) quasars at $z\approx 1-3$ and archival ALMA submillimeter host galaxy sizes to investigate the ISM contribution to the quasar obscuration. We calculate SFR and ISM column densities for the IR quasars and a control sample of submillimeter galaxies (SMGs) not hosting quasar activity and show that: (1) the quasar obscured fraction is constant up to $\rm SFR\approx 300 \: M_{\odot} \: yr^{-1}$, and then increases towards higher SFR, suggesting that the ISM obscuration plays a significant role in starburst host galaxies, and (2) at $\rm SFR\gtrsim 300 \: M_{\odot} \: yr^{-1}$, the SMGs and IR quasars have similarly compact submillimeter sizes ($R_{\rm e}\approx 0.5-3\rm \: kpc$) and, consequently, the ISM can heavily obscure the quasar, even reaching Compton-thick ($N_{\rm H}>10^{24} \rm \: cm^{-2}$) levels in extreme cases. Based on our results, we infer that $\approx 10-30\%$ of the IR quasars with $\rm SFR\gtrsim 300 \: M_{\odot} \: yr^{-1}$ are obscured solely by the ISM.Comment: Accepted for publication in MNRAS Letter

Probing the roles of orientation and multi-scale gas distributions in shaping the obscuration of Active Galactic Nuclei through cosmic time

The origin of obscuration in Active Galactic Nuclei (AGN) is still an open debate. In particular, it is unclear what drives the relative contributions to the line-of-sight column densities from galaxy-scale and torus-linked obscuration. The latter source is expected to play a significant role in Unification Models, while the former is thought to be relevant in both Unification and Evolutionary Models. In this work, we make use of a combination of cosmological semi-analytic models and semi-empirical prescriptions for the properties of galaxies and AGN, to study AGN obscuration. We consider a detailed object-by-object modelling of AGN evolution, including different AGN light curves (LCs), gas density profiles, and also AGN feedback-induced gas cavities. Irrespective of our assumptions on specific AGN LC or galaxy gas fractions, we find that, on the strict assumption of an exponential profile for the gas component, galaxy-scale obscuration alone can hardly reproduce the fraction of $\log (N_{\rm H}/$cm$^{-2}) \geq 24$ sources at least at $z\lesssim3$. This requires an additional torus component with a thickness that decreases with luminosity to match the data. The torus should be present in all evolutionary stages of a visible AGN to be effective, although galaxy-scale gas obscuration may be sufficient to reproduce the obscured fraction with $22<\log (N_{\rm H}/$cm$^{-2})<24$ (Compton-thin, CTN) if we assume extremely compact gas disc components. The claimed drop of CTN fractions with increasing luminosity does not appear to be a consequence of AGN feedback, but rather of gas reservoirs becoming more compact with decreasing stellar mass.Comment: MNRAS, accepted, 19 pages, 15 figures, 3 appendice

UV-visible and 1H−15N^1H-^{15}N NMR spectroscopic studies of colorimetric thiosemicarbazide anion sensors

Four model thiosemicarbazide anion chemosensors containing three N – H bonds, substituted with phenyl and/or 4-nitrophenyl units, were synthesised and studied for their anion binding abilities with hydroxide, fl uoride, acetate, dihydrogen phosphate and chloride. The anion binding properties were studied in DMSO and 9 : 1 DMSO – H 2 O by UV-visible absorption and 1 H/ 13 C/ 15 N NMR spectroscopic techniques and corroborated with DFT studies. Signi fi cant changes were observed in the UV-visible absorption spectra with all anions, except for chloride, accompanied by dramatic colour changes visible to the naked eye. These changes were determined to be due to the deprotonation of the central N – H proton and not due to hydrogen bonding based on 1 H/ 15 N NMR titration studies with acetate in DMSO- d 6 – 0.5% water. Direct evidence for deprotonation was con fi rmed by the disappearance of the central thiourea proton and the formation of acetic acid. DFT and charge distribution calculations suggest that for all four compounds the central N – H proton is the most acidic. Hence, the anion chemosensors operate by a deprotonation mechanism of the central N – H proton rather than by hydrogen bonding as is often reported

Probing the roles of orientation and multi-scale gas distributions in shaping the obscuration of Active Galactic Nuclei through cosmic time

The origin of obscuration in Active Galactic Nuclei (AGN) is still an open debate. In particular, it is unclear what drives the relative contributions to the line-of-sight column densities from galaxy-scale and torus-linked obscuration. The latter source is expected to play a significant role in Unification Models, while the former is thought to be relevant in both Unification and Evolutionary Models. In this work, we make use of a combination of cosmological semi-analytic models and semi-empirical prescriptions for the properties of galaxies and AGN, to study AGN obscuration. We consider a detailed object-by-object modelling of AGN evolution, including different AGN light curves (LCs), gas density profiles, and also AGN feedback-induced gas cavities. Irrespective of our assumptions on specific AGN LC or galaxy gas fractions, we find that, on the strict assumption of an exponential profile for the gas component, galaxy-scale obscuration alone can hardly reproduce the fraction of log (NH/cm−2) ≥ 24 sources at least at z ≲ 3. This requires an additional torus component with a thickness that decreases with luminosity to match the data. The torus should be present in all evolutionary stages of a visible AGN to be effective, although galaxy-scale gas obscuration may be sufficient to reproduce the obscured fraction with 22 &lt; log (NH/cm−2) &lt; 24 (Compton-thin, CTN) if we assume extremely compact gas disc components. The claimed drop of CTN fractions with increasing luminosity does not appear to be a consequence of AGN feedback, but rather of gas reservoirs becoming more compact with decreasing stellar mass