The properties of the stellar populations in ULIRGs I: sample, data and spectral synthesis modelling

We present deep long-slit optical spectra for a sample of 36 Ultraluminous Infrared Galaxies (ULIRGs), taken with the William Herschel Telescope (WHT) on La Palma with the aim of investigating the star formation histories and testing evolutionary scenarios for such objects. Here we present the sample, the analysis techniques and a general overview of the properties of the stellar populations. Spectral synthesis modelling has been used in order to estimate the ages of the stellar populations found in the diffuse light sampled by the spectra in both the nuclear and extended regions of the target galaxies. We find that adequate fits can be obtained using combinations of young stellar populations (YSPs,t_YSP<=2 Gyr), with ages divided into two groups: very young stellar populations (VYSPs, t_VYSP <=100 Myr) and intermediate-young stellar populations (IYSPs, 0.1 < t_IYSP <= 2 Gyr). Our results show that YSPs are present at all locations of the galaxies covered by our slit positions, with the exception of the northern nuclear region of the ULIRG IRAS 23327+2913. Furthermore, VYSPs are presents in at least 85% of the 133 extraction apertures used for this study. Old stellar populations (OSPs, t_{OSP} > 2 Gyr) do not make a major contribution to the optical light in the majority of the apertures extracted. In fact they are essential for fitting the spectra in only 5% (7) of the extracted apertures. The estimated total masses for the YSPs (VYSPs+IYSPs) are in the range 0.18 x 10^{10} <= M_YSP <= 50 x 10^{10} Msun. We have also estimated the bolometric luminosities associated with the stellar populations detected at optical wavelengths, finding that they fall in the range 0.07 x 10^{12} < L_bol < 2.2 x 10^{12} Lsun. In addition, we find that reddening is significant at all locations in the galaxies.Comment: accepted for publication in MNRA

Optimal Control Realizations of Lagrangian Systems with Symmetry

A new relation among a class of optimal control systems and Lagrangian systems with symmetry is discussed. It will be shown that a family of solutions of optimal control systems whose control equation are obtained by means of a group action are in correspondence with the solutions of a mechanical Lagrangian system with symmetry. This result also explains the equivalence of the class of Lagrangian systems with symmetry and optimal control problems discussed in \cite{Bl98}, \cite{Bl00}. The explicit realization of this correspondence is obtained by a judicious use of Clebsch variables and Lin constraints, a technique originally developed to provide simple realizations of Lagrangian systems with symmetry. It is noteworthy to point out that this correspondence exchanges the role of state and control variables for control systems with the configuration and Clebsch variables for the corresponding Lagrangian system. These results are illustrated with various simple applications

Universality Classes of Diagonal Quantum Spin Ladders

We find the classification of diagonal spin ladders depending on a characteristic integer $N_p$ in terms of ferrimagnetic, gapped and critical phases. We use the finite algorithm DMRG, non-linear sigma model and bosonization techniques to prove our results. We find stoichiometric contents in cuprate $CuO_2$ planes that allow for the existence of weakly interacting diagonal ladders.Comment: REVTEX4 file, 3 color figures, 1 tabl

Molar Entropy and Enthalpy of CO Adsorbed in Zeolites as Derived from VTIR Data: Role of Intermolecular Modes

Detailed analysis of recently reported variable-temperature IR (VTIR) spectra of carbon monoxide adsorbed in alkaline zeolites shows how, not only the corresponding values of standard adsorption enthalpy ((Formula presented.)) and entropy ((Formula presented.)) can be obtained, but also the thermodynamic values of molar entropy and enthalpy which characterize the adsorbed gas phase. In addition, it is shown that the so obtained molar entropy data can lead to new insights into soft molecular modes, which would be hardly accessible by conventional IR spectroscopic techniques

Starburst radio galaxies: general properties, evolutionary histories and triggering

In this paper we discuss the results of a programme of spectral synthesis modelling of a sample of starburst radio galaxies in the context of scenarios for the triggering of the activity and the evolution of the host galaxies. The starburst radio galaxies -- comprising ~15 - 25% of all powerful extragalactic radio sources -- frequently show disturbed morphologies at optical wavelengths, and unusual radio structures, although their stellar masses are typical of radio galaxies as a class. In terms of the characteristic ages of their young stellar populations (YSP), the objects can be divided into two groups: those with YSP ages t_ysp < 0.1 Gyr, in which the radio source has been triggered quasi-simultaneously with the main starburst episode, and those with older YSP in which the radio source has been triggered or re-triggered a significant period after the starburst episode. Combining the information on the YSP with that on the optical morphologies of the host galaxies, we deduce that the majority of the starburst radio galaxies have been triggered in galaxy mergers in which at least one of the galaxies is gas rich. However, the triggering (or re-triggering) of the radio jets can occur immediately before, around, or a significant period after the final coalescence of the merging nuclei, reflecting the complex gas infall histories of the merger events. Overall, our results provide further evidence that powerful radio jet activity can be triggered via a variety of mechanisms, including different evolutionary stages of major galaxy mergers; clearly radio-loud AGN activity is not solely associated with a particular stage of a unique type of gas accretion event.Comment: 16 pages, 3 Figures, accepted for publication in MNRA

Localized Fibrous Tumors of the Pleura: Experience With 7 Recent Cases

OBJECTIVE: Localized fibrous tumors of the pleura are rare. We report 7 cases and review the literature in order to define the range of clinical characteristics of these tumors, treatment options, and prognosis. METHODS: A retrospective review of 7 cases treated between 1997 and 2003, focusing on clinical presentation, diagnostic tests, and treatment. The tumor was removed surgically in all cases, by thoracotomy in 6 cases and by video-assisted thoracoscopic surgery in 1 patient. RESULTS: All patients recovered fully after surgery, with no postoperative complications. One patient experienced recurrence twice, 33 and 67 months after the initial resection. All are alive at the time of writing, after a mean follow up period of 19 months (range 1 month to 5 years and 10 months). CONCLUSIONS: The treatment of choice for a fibrous tumor of the pleura is full resection and follow up to detect possible late recurrence