Seminars and Colloquia at ESO Garching

For ESO and ESO-related Conferences and Workshops in Europe and Chile please check the main Conferences and Workshops page.

September 2014

09.09.14 (Tuesday)
10:00, ESO room "Fornax", Star and Planet Formation seminar
"Interstellar chemistry of nitrogen hydrides with Herschel"
Romane Le Gal (IPAG, Grenoble)
Abstract
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"Interstellar chemistry of nitrogen hydrides with Herschel"

Romane Le Gal (IPAG, Grenoble)

Abstract
Nitrogen is amongst the most abundant metals in the interstellar medium. Observations of several nitrogen-bearing species suggest abundances in sharp disagreement with current chemical models. Although some of these observations show that some gas-grain processes are at work, gas-phase chemistry needs first to be revisited. Strong constraints are provided by recent Herschel/HIFI observations of nitrogen hydrides fundamental rotational transitions in cold gas [1]. The aim of my PhD thesis work was to comprehensively analyse the interstellar chemistry of nitrogen, focussing on the gas-phase formation of the simplest polyatomic species, namely nitrogen hydrides. In cold and dense gas conditions, the chemistry of these latter is initiated by slow neutral-neutral reactions (the conversion from N to N2, in contrast to their carbonated and oxygenated analogues. We have investigated and revisited this specific part of the nitrogen chemistry. To this purpose, we present a new chemical network [2] in which the kinetic rates of critical reactions involved in nitrogen chemistry have been updated. Our new network is based on recent experimental and theoretical studies, including the calculation of nuclear spin branching ratios [3]. The different spin symmetries of the nitrogen hydrides are treated self-consistently, together with the ortho and para forms of molecular hydrogen. This new network is used to model the time evolution of the nitrogen species abundances in cold and dense gas conditions (n=10^4 cm^-3, T=10 K). The steady-state results are compared to observations of NH, NH2 and NH3 towards a sample of low-mass protostars, with a special emphasis on the influence of the overall amounts of gaseous carbon, oxygen, and sulphur. Our predicted ortho-to-para ratios for NH2 and NH3 [4] are also compared with the observational results of Persson et al. towards cold diffuse clouds [5].

References
[1] Hily-Blant, P., Maret, S., Bacmann, A., et al. 2010a, A&A, 521, L52
[2] Le Gal, R., Hily-Blant, P., Faure, A., Pineau des Forêts, G., Rist, C., & Maret, S., 2014, A&A, 562, A83
[3] Rist, C., Faure, A., Hily-Blant, P., & Le Gal, R., 2013, J. Phys. Chem. A, 117, 9800
[4] Faure, A., Hily-Blant, P., Le Gal, R., Rist, C., & Pineau des Forêts, G., 2013, ApJ, 770, L2
[5] Persson, C. M., De Luca, M., Mookerjea, B., et al. 2012, A&A, 543, A145
09.09.14 (Tuesday)
12:30, ESO room "Fornax", Lunch Talk
"Interstellar medium and initial stages of star formation: comparing simulations and observations"
Johanna Malinen (University of Helsinki)
Abstract
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"Interstellar medium and initial stages of star formation: comparing simulations and observations"

Johanna Malinen (University of Helsinki)

Abstract
Filamentary structures in interstellar molecular clouds have long been recognised as an important part of the star formation process. Recent studies have confirmed that dense cores in different stages of star formation are commonly located in the filaments. Therefore, it is important to study the structure and formation of the filaments and the cores, to understand the details of the early phases of star formation. The density structure of molecular clouds can be studied using many different methods and wavelengths. All techniques have their own drawbacks, and, therefore, it is crucial to compare the results obtained with different methods. Before making conclusions on observational data, the observational uncertainties and biases should be evaluated with simulations. In this presentation, I will give a short overview of star formation theory, observations, and simulations, and review the main results of my PhD thesis, concentrated on comparing simulations and observations of the early, prestellar phase of star formation.
15.09.14 (Monday)
12:30, ESO auditorium "Telescopium", Lunch Talk
"Oxygen in the Local Universe: Error and Uncertainty in Abundances"
Kevin Croxall (Ohio State University)
Abstract
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"Oxygen in the Local Universe: Error and Uncertainty in Abundances"

Kevin Croxall (Ohio State University)

Abstract
The metal content of a galaxy is one of the most important properties used to distinguish between viable evolutionary scenarios and strongly influences many of the physical processes in the ISM. An absolute and robust calibration of extragalactic metallicities is essential in constraining models of chemical enrichment, chemical evolution, and the cycle of baryons in the cosmos. Despite this strong dependence on abundance, the calibration of nebular abundances from nebular emission lines remains uncertain. Different calibrations of the abundance scale require different assumptions, which may or may not be valid, and measurements, not all of which are easily obtained. MODS on LBT and the late Herschel Space Observatory are allowing us to clarify this long standing calibration uncertainty. The sensitivity of MODS is enabling the detection of numerous temperature sensitive lines and features in nearby galaxies and Herschel observations of the [O III] 88 micron fine structure line in nearby galaxies are enabling the determination of nebular abundances that are nearly independent of temperature. I will discuss current efforts at constraining the abundance scale using these modern facilities.
16.09.14 (Tuesday)
12:30, ESO auditorium "Telescopium", Lunch Talk
"Astrochemistry, cosmic rays, and H3+"
Miwa Goto (USM)
Abstract
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"Astrochemistry, cosmic rays, and H3+"

Miwa Goto (USM)

Abstract
The talk starts with the introductory accounts of the astrochemistry, the cosmic rays and the hydrogen molecular ion H3+ to illustrate how the study of the one has immediate impacts on the other two. The Galactic Center is used as a laboratory to show that the three elements lively influence each other. The emphasis is put on how the spectroscopy of the H3+ has been used to develop our view of the interstellar medium in the Galactic Center in the past decade.
23.09.14 (Tuesday)
12:30, ESO room "Fornax", Lunch Talk
"AKARI FIR All-Sky Maps"
Yasuo Doi (University of Tokyo)
Abstract
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"AKARI FIR All-Sky Maps"

Yasuo Doi (University of Tokyo)

Abstract
We present the AKARI far-infred (FIR) all-sky maps and describe its characteristics, calibration accuracy and scientific capabilities. The AKARI FIR survey has covered 97% of the whole sky in four photometric bands, which cover continuously 50--180 micron with band central wavelengths of 65, 90, 140, and 160 microns. The spatial resolution of the maps is ~60--90 arcsecs and the detection limit is ~1--12 [MJy/sr] with an absolute accuracy of ~20%.

The data for the first time reveal the whole sky distribution of interstellar matter with arcminute-scale spatial resolutions at the peak of dust continuum emission, enabling us to investigate large-scale distribution of interstellar medium in great detail. The filamentary structure covering the whole sky is well traced by the all-sky maps.

The data are currently under assessment by the AKARI science team members and to be publicly released later this year. The release schedule is also described in this presentation.
30.09.14 (Tuesday)
12:30, ESO auditorium "Telescopium", Lunch Talk
"Modelling Galaxies within state-of-the-art Cosmological Simulations"
Violeta Gonzalez-Perez (University of Durham)
Abstract
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"Modelling Galaxies within state-of-the-art Cosmological Simulations"

Violeta Gonzalez-Perez (University of Durham)

Abstract
Galaxies are thought to form within haloes of dark matter, whose gravity allows the galaxies to exist. The formation and evolution of galaxies is affected by a multitude of other processes besides gravity and computational modelling is the only way we can attempt to understand all these processes. In this work we present a new development of the GALFORM semi-analytical model of galaxy formation and evolution, which exploits a Millennium Simulation-class N-body run performed with the Wilkinson Microwave Anisotropy Probe 7 cosmology. We use this new model to study the impact of the choice of stellar population synthesis (SPS) model on the predicted evolution of the galaxy luminosity function. Besides this model, we have generated a new GALFORM flavour constructed from merger trees derived from EAGLE, a hydrodynamical simulation. We compare results from both GALFORM and EAGLE.

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