Formation of S0 galaxies through mergers. Evolution in the Tully-Fisher relation since z∼1z\sim1

(Abridged version) We explore whether a scenario that combines an origin by mergers at $z\sim$1.8-1.5 with a subsequent passive evolution of the resulting S0 remnants since $z \sim$0.8-1 is compatible with observational data of S0s in the Tully-Fisher relation (TFR). We studied a set of major and minor merger experiments from the GalMer database that generate massive S0 remnants. We analysed the location of these remnants in the photometric and stellar TFRs assuming that they correspond to $z\sim0.8$ galaxies. We then estimated their evolution in these planes over the last 7 Gyr. The results were compared with data of real S0s and spirals at different redshifts. We also tested how the use of Vcirc or Vrot,max affects the results. We found that just after $\sim$1-2 Gyr of coalescence, major mergers generate S0 remnants that are outliers of the local photometric and stellar TFRs at $z\sim0.8$. After $\sim$4-7 Gyr of passive evolution in isolation, the S0 remnants move towards the local TFR, although the initial scatter among them persists. This scatter is sensitive to the indicator used for the rotation velocity: Vcirc values yield a lower scatter than when Vrot,max values are considered instead. In the planes involving Vrot,max, a clear segregation of the S0 remnants in terms of the spin-orbit coupling of the model is observed, in which the remnants of retrograde encounters overlap with local S0s hosting counter-rotating discs. The location of the S0 remnants at $z\sim 0$ agrees well with the observed distribution of local S0 galaxies in the $\sigma_0$-$M_K$, Vcirc-$\sigma_0$ and Vrot,max-$\sigma_0$ planes. Thus, massive S0 galaxies may have been formed through major mergers that occurred at high redshift and have later evolved towards the local TFR through passive evolution in relative isolation, a mechanism that would also contribute to the scatter observed in this relation.Comment: 19 pages, 15 figures. Accepted for publication in A&

Formation of S0 galaxies through mergers. Bulge-disc structural coupling resulting from major mergers

Observations reveal a strong structural coupling between bulge and disc in S0 galaxies, which seems difficult to explain if they have formed from supposedly catastrophic events such as major mergers. We face this question by quantifying the bulge-disc coupling in dissipative simulations of major and minor mergers that result in realistic S0s. We have studied the dissipative N-body binary merger simulations from the GalMer database that give rise to realistic, relaxed E/S0 and S0 remnants (67 major and 29 minor mergers). We simulate surface brightness profiles of these S0-like remnants in the K-band, mimicking typical observational conditions, to perform bulge-disc decompositions analogous to those carried out in real S0s. The global bulge-disc structure of these remnants has been compared with real data, and they distribute in the B/T - r_e - h_d parameter space consistently with real bright S0s, where B/T is the bulge-to-total luminosity ratio, r_e is the bulge effective radius, and h_d is the disc scalelength. Major mergers can rebuild a bulge-disc coupling in the remnants after having destroyed the structures of the progenitors, whereas minor mergers directly preserve them. Remnants exhibit B/T and r_e/h_d spanning a wide range of values, and their distribution is consistent with observations. Many remnants have bulge Sersic indices ranging 1<n<2, flat appearance, and contain residual star formation in embedded discs, a result which agrees with the presence of pseudobulges in real S0s. Contrary to the popular view, mergers (and in particular, major events) can result in S0 remnants with realistically coupled bulge-disc structures in less than ~3 Gyr. In conclusion, the bulge-disc coupling and the presence of pseudobulges in real S0s cannot be used as an argument against the possible major-merger origin of these galaxies.Comment: 23 pages, accepted for publication in Astronomy and Astrophysics (version after minor language corrections

Excited-State Proton and Charge Transfer in Protonated Amino and Methylated Derivatives of 2-(2′-Hydroxyphenyl)benzimidazole

This is the peer-reviewed version of the following article: The Journal of Physical Chemistry B 2015, 119, 2475–2489, DOI: 10.1021/jp507917u, which has been published in final form at https://pubs.acs.org/doi/abs/10.1021/jp507917u. This article may be used for non-commercial purposes onlyWe studied the excited-state behavior of a family of mono- and diprotonated derivatives of 2-phenylbenzimidazole in different solvents, using steady-state and time-resolved fluorescence spectroscopy. The species investigated were 2-(4′-amino-2′-hydroxyphenyl)benzimidazole (1), the diethylamino analogue 2-(4′-N,N-diethylamino-2′-hydroxyphenyl)benzimidazole (2) and its N-methylated derivative 1-methyl-2-(4′-N,N-diethylamino-2′-hydroxyphenyl)benzimidazole (3). The O-methoxy derivatives of 2 and 3 (2-OMe and 3-OMe), and the simpler models 2-phenylbenzimidazole (4) and its 4′-amino (5) and 4′-dimethylamino (6) derivatives were also studied. We found that the dications of 1, 2, and 3 (protonated at the benzimidazole N3 and at the amino group) were strong photoacids, which were deprotonated at the hydroxyl group upon excitation in aqueous solution (totally for 2 and 3) to give a tautomer of the ground-state monocation. In contrast, no photodissociation was observed for the monocations of these species. Instead, some of the monocations studied behaved as molecular rotors, for which electronic excitation led to a twisted intramolecular charge transfer (TICT) state. The monocations of 2, 3, 2-OMe, 3-OMe, and 6, protonated at the benzimidazole N3, experienced a polarity- and viscosity-dependent radiationless deactivation associated with a large-amplitude rotational motion. We propose that this process is connected to an intramolecular charge transfer from the dimethylaminophenyl or diethylaminophenyl moiety (donor) to the protonated benzimidazole group (acceptor) of the excited monocation, which yields a twisted charge-transfer species. No fluorescence from this species was detected except for 3 and 3-OMe in low-viscosity solventsWe are indebted to the European Regional Development Fund, the Spanish Ministry of Economy and Competitiveness (Grant CTQ2010-17835), and the Xunta de Galicia (Grants GPC2013/052, CN2012/314, and EM2012/091) for financial support of our work. S.R. and J.L.P.L. are thankful for a MEC-FPU fellowship and a “Ramón y Cajal” contract, respectivelyS

Photoinduced Proton and Charge Transfer in 2‑(2′- Hydroxyphenyl)imidazo[4,5‑b]pyridine

This is the peer-reviewed version of the following article: The Journal of Physical Chemistry B 2013, 117, 884–896, DOI: 10.1021/jp311709c, which has been published in final form at https://pubs.acs.org/doi/abs/10.1021/jp311709c. This article may be used for non-commercial purposes onlyThis paper deals with the interplay between solvent properties and isomerism of 2-(2′-hydroxyphenyl)imidazo[4,5-b]pyridine (1), and the proton and charge-transfer processes that the different isomers undergo in the first-excited singlet state. We demonstrate the strong influence of these processes on the fluorescence properties of 1. We studied the behavior of 1 in several neutral and acidified solvents, by UV–vis absorption spectroscopy and by steady-state and time-resolved fluorescence spectroscopy. The fluorescence of 1 showed a strong sensitivity to the environment. This behavior is the result of conformational and isomeric equilibria and the completely different excited-state behavior of the isomers. For both neutral and cationic 1, isomers with intramolecular hydrogen bond between the hydroxyl group and the benzimidazole N undergo an ultrafast excited-state intramolecular proton transfer (ESIPT), yielding tautomeric species with very large Stokes shift. For both neutral and cationic 1, isomers with the OH group hydrogen-bonded to the solvent behave as strong photoacids, dissociating in the excited state in solvents with basic character. The pyridine nitrogen exhibits photobase character, protonating in the excited state even in some neutral solvents. An efficient radiationless deactivation channel of several species was detected, which we attributed to a twisted intramolecular charge-transfer (TICT) process, facilitated by deprotonation of the hydroxyl group and protonation of the pyridine nitrogenThis work has been supported by the Spanish Government and the European Regional Development Fund (Grant CTQ2010-17835) and the Xunta de Galicia (Grant CN 2012/314). A.B., M.V., and J.L.P.L. are thankful for a “Fundación Segundo Gil Dávila” fellowship, a MEC-FPU fellowship, and a “Ramon y Cajal” contract, respectivelyS

Moderately Strong Photoacid Dissociates in Alcohols with High Transient Concentration of the Proton-Transfer Contact Pair

This is the peer-reviewed version of the following article: The Journal of Physical Chemistry Letters 2014, 5, 989–994, DOI: 10.1021/jz5001648, which has been published in final form at https://pubs.acs.org/doi/abs/10.1021/jz5001648. This article may be used for non-commercial purposes onlyProton transfer from strong photoacids to hydroxylic solvents is much under debate. Experimentally, the main issue stems from relaxation and diffusion processes that are concomitant with ultrafast proton transfer and blur population dynamics. To overcome this, we propose a fast photodissociation reaction that, however, proceeds slower than solvent relaxation. Fluorescence spectroscopy of the cationic photoacid 2-(1′-hydroxy-2′-naphtyl)benzimidazolium reveals a two-stage mechanism: (a) reversible elementary proton transfer inside the solvent shell and (b) irreversible contact-pair splitting. The time evolution of the fluorescence signal is complex, yet this is explained quantitatively by simultaneous, spectrally overlapping emission of the acid, the conjugate base, and the contact proton-transfer pair. The latter attains high transient concentration in linear alcohols. Microscopic rate constants of dissociation are determinedWe thank the Spanish Government and the European Regional Development Fund (Grants CTQ2010-17835 and CTQ2010-17026) and the Xunta de Galicia (Grants CN 2012/314,EM2012/091, and GPC2013/052) for financial support of our work. J.L.P.L. thanks the Spanish Ministry of Economy and Competitiveness for funding through the Ramón y Cajal Programm 2009. M.V.G. and A.B. thank the Spanish Government and the “Segundo Gil-Dávila” Foundation, respectively, for financial supportS

Electro-optic system for online light transmission control of polymer-dispersed liquid crystal windows

Polymer-dispersed liquid crystals (PDLCs) are formed by micro droplets of liquid crystal embedded in a flexible matrix and sandwiched between transparent electrodes. Large area units (several square meters) can be easily prepared. Opaque, transparent, and intermediate light transmission states can be achieved by applying appropriate electric fields These features allow their use in active windows for illumination, greenhouse regulation, and privacy, both on buildings and vehicles. An electro-optic system based on a micro controlled driver was implemented for on-line control of PDLC windows. The system may self regulate daylight or may be used as remote control.Publicad

Evolution induced by dry minor mergers onto fast-rotator S0 galaxies

We analysed collisionless N-body simulations of intermediate and minor dry mergers onto S0s to test whether these mergers can generate S0 galaxies with kinematics intermediate between fast and slow rotators. We find that minor mergers induce a lower decrease of the global rotational support than encounters of lower mass ratios, which results in S0s with properties intermediate between fast and slow rotators. The resulting remnants are intrinsically more triaxial, less flattened, and span the whole range of apparent ellipticities up to $\epsilon_\mathrm{e} \sim 0.8$. They do not show lower apparent ellipticities in random projections than initially; on the contrary, the formation of oval distortions and the disc thickening increase the percentage of projections at $0.4 < \epsilon_\mathrm{e} < 0.7$. In the experiments with S0b progenitor galaxies, minor mergers tend to spin up the bulge and to decrease slightly its intrinsic ellipticity, whereas in the cases of primary S0c galaxies they keep the rotational support of the bulge nearly constant and decrease significantly its intrinsic ellipticity. The remnant bulges remain nearly spherical ($B/A \sim C/A > 0.9$), but exhibit a wide range of triaxialities ($0.20 < T < 1.00$). In the plane of global anisotropy of velocities ($\delta$) vs. intrinsic ellipticity ($\epsilon_\mathrm{e,intr}$), some of our models extend the linear trend found in previous major merger simulations towards higher $\epsilon_\mathrm{e,intr}$ values, while others depart from it. This is consistent with the wide dispersion exhibited by real S0s in this diagram compared with ellipticals, which follow the linear trend drawn by major merger simulations. The different trends exhibited by ellipticals and S0 galaxies in the $\delta$ - $\epsilon_\mathrm{e}$ diagram may be pointing to the different role played by major mergers in the build-up of each morphological type.Comment: Corrected typos. 20 pages, 14 figures. Accepted for publishing in A&

Analysis of extreme rainfall in the Ebre Observatory (Spain)

The relationship between maximum rainfall rates for time intervals between 5 min and 24 h has been studied from almost a century (1905-2003) of rainfall data registered in the Ebre Observatory (Tarragona, Spain). Intensity-duration-frequency (IDF) curves and their master equation for every return period in the location have been obtained, as well as the probable maximum precipitation (PMP) for all the considered durations. In particular, the value of the 1-day PMP has resulted to be 415 mm, very similar to previous estimations of this variable for the same location. Extreme rainfall events recorded in this period have been analyzed and classified according to their temporal scale. Besides the three main classes of cases corresponding to the main meteorological scales, local, mesoscale, and synoptic, a fourth group constituted by complex events with high-intensity rates for a large range of durations has been identified also, indicating the contribution of different scale meteorological processes acting together in the origin of the rainfall. A weighted intensity index taking into account the maximum rainfall rate in representative durations of every meteorological scale has been calculated for every extreme rainfall event in order to reflect their complexity

Analysis of synoptic patterns in relationship with severe rainfall events in the Ebre Observatory (Catalonia)

The study has obtained a classification of the synoptic patterns associated with a selection of extreme rain episodes registered in the Ebre Observatory between 1905 and 2003, showing a return period of not less than 10 years for any duration from 5 min to 24 h. These episodes had been previously classified in four rainfall intensity groups attending to their meteorological time scale. The synoptic patterns related to every group have been obtained applying a multivariable analysis to three atmospheric levels: sea-level pressure, temperature, and geopotential at 500 hPa. Usually, the synoptic patterns associated with intense rain in southern Catalonia are featured by low-pressure systems advecting warm and wet air from the Mediterranean Sea at the low levels of the troposphere. The configuration in the middle levels of the troposphere is dominated by negative anomalies of geopotential, indicating the presence of a low or a cold front, and temperature anomalies, promoting the destabilization of the atmosphere. These configurations promote the occurrence of severe convective events due to the difference of temperature between the low and medium levels of troposphere and the contribution of humidity in the lowest levels of the atmosphere.Peer ReviewedPostprint (author's final draft

Analysis of extreme rainfall in the Ebre Observatory (Spain)

The final publication is available at Springer via http://dx.doi.org/10.1007/s00704-015-1476-0Relationship between maximum rainfall rates for time intervals between 5 minutes and 24 hours has been studied from almost a century (1905-2003) of rainfall data registered in the Ebre Observatory (Tarragona, Spain). Intensity-duration-frequency (IDF) curves and its master equation for every return period in the location have been obtained, as well as the probable maximum precipitation (PMP) for all the considered durations. In particular, the value of the 1-day PMP has resulted 415 mm, very similar to previous estimations of this variable for the same location. Extreme rainfall events recorded in this period have been analyzed and classified according to their temporal scale. Besides the three main classes of cases corresponding to the main meteorological scales, local, mesoscale and synoptic, a fourth group constituted by complex events with high intense rates for a large range of durations has been identified also, indicating the contribution of different scale meteorological processes acting together in the origin of the rainfall. A weighted intensity index taking into account the maximum rainfall rate in representative durations of every meteorological scale has been calculated for every extreme rainfall event in order to reflect their complexity.Peer ReviewedPostprint (published version