The Orion Nebula:

Registered participants

1. Abel, Nick: "Physical Conditions in Orion's Veil" Show abstract
   Orion's Veil is a foreground cloud of gas and dust, between us and the Trapezium cluster, which is the primary source of extinction towards the Nebula. Observations in the radio and optical regime have allowed us to create maps of the extinction and line-of-sight magnetic field across the Veil. These maps, combined with optical and UV absorption line studies towards the Trapezium stars, provide a wealth of observational data which makes the Veil an ideal laboratory with which to study the physical processes in the ISM. This talk will review the observations of the Veil, and how these unique set of observations combined with theoretical calculations have improved our understanding of the geometry, chemistry, and energetics of the environment. Specifically, this merger of observation and theory has allowed us to determine that the Veil's energetics is dominated by magnetic fields, have helped us to explain the lack of molecules in the region, and has allowed us to determine the thickness of the Veil and its distance away from the Trapezium.
2. Alves, Joao: "Orion Nebula Cluster Revisited: the foreground population" Show abstract
   The Orion Nebula Cluster (ONC) is the nearest massive star forming region hence a fiducial object for the understanding of the star formation process. Current massive star and cluster formation theories are based on observations of this well studied cluster. Nevertheless, the existence of an unknown population of foreground stellar interlopers could potentially affect the current massive star and cluster formation picture. We use the optical properties of the dust in the Orion A cloud to block optical background light, effectively isolating the stellar population between Earth and this cloud. We then use a multi-wavelength observational approach, from X-rays to mid-infrared, to characterize the cloud's foreground stellar population. In this talk we will present the first results from this work and discuss the degree of contamination of the ONC by the foreground population and its effect of the current observables for this benchmark region.
3. Arab, Heddy: "The Orion Bar seen by Herschel" Show abstract
   The Orion Bar, one of the brightest photodissociation regions (PDRs) in the far-Infrared (FIR) sky, has been observed with the Herschel Space Telescope. We present a complete and coherent analysis of the gas and dust component in the Orion Bar region. PACS and SPIRE photometric maps, combined to Spitzer/IRAC observations, are used to perform a spatially detailed analysis of the dust within the Bar.  We confront a dust model coupled with a radiative transfer code to recover the properties of dust in the PDR and probe their evolution. Spatially resolved spectroscopic observations from PACS are used to characterise the emission of the FIR cooling lines that trace the gas local conditions. Finally, the spatial correlations between molecular tracers (12CO, 13CO, C18O, CH+?) are studied from SPIRE Fourier Transform Spectrometer observations.
4. Ascasibar, Yago: "Hydrostatic models of the Orion Bar" Show abstract
   Due to its close distance to the Earth and its nearly edge-on geometry, the Orion Bar provides an excellent testbed for detailed photoionization models. We will show that, although the observed structure of the ionized HII region can be reproduced with remarkable accuracy, the agreement in the atomic layer is only qualitative, and the predicted abundances of several molecular species are off by several orders of magnitude. Consistent with previous work, our results hint that the density of cosmic rays is high (well above the Galactic background, though not as large as implied by equipartition arguments), but their role on the molecular chemistry is still unclear.
5. Esteban, Cesar: "The Orion nebula: a reference for ionized gas phase abundance determinations" Show abstract
   The chemical composition of the Orion nebula is traditionally considered the standard reference for the ionized gas phase in the solar neighborhood and for the determination of the abundance gradients in the Milky Way. Therefore, it is essential to obtain an accurate set of elemental abundances for this object. In this talk I will review the results of the different works devoted to the determination of the chemical composition of the nebula as well as the different techniques used for that. Particularly, I will focus on the discrepancy when comparing abundances derived from collisonally excited and recombination lines of the same ion. I will also review recent studies on particular objects inside the nebula as Herbig-Haro objects, protoplanetary discs and ionization fronts. These structures produce strong small spatial-scale variations on the physical conditions of the nebula that affect the determination of gaseous chemical abundances. Finally, I will discuss some aspects of the dust content and distribution across the Orion nebula and some evidences of localized destruction of dust particles.
6. Ferland, Gary: "Photoionization modelling of the Orion nebula" Show abstract
   TBD
7. Flores-Fajardo, Nahiely: "Ionization-hydrodynamic models of the Orion proplyds as a tool for gas-phase abundance determinations" - N. Flores-Fajardo and W. J. Henney Show abstract
   Proplyds are disks around young low-mass stars inside M42 photoevaporated by ultraviolet radiation from the massive Trapezium stars. Recent spectrophotometry gives tantalizing evidence of abundance differences between proplyds and the surrounding nebula, with important implications for the evolution of protoplanetary disks. However, proplyds are highly structured at very small scales, which must be taken into account in any abundance analysis. We present physical models of the proplyds that combine a simplified (but realistic) treatment of the acceleration of the flow through the ionization front with a detailed calculation of the radiative transfer, ionization, and thermal balance using the CLOUDY code. We predict the emissivity structure in multiple emission lines, together with the flux, morphology and kinematic profile of any given line. Comparison with high-resolution imaging, high-dispersion spectroscopy, and deep spectrophotometry tightly constrains the model parameters, giving abundances much more reliably than can be acheived by empirical methods.
8. Forbrich, Jan: "High-energy Emission from Young Stars in the Orion Nebula - the Radio and X-ray Views" Show abstract
   TBD
9. Garcia-Rojas, Jorge: "M43, the little sister of the Orion Nebula" Show abstract
   I will present the study of he Galactic HII region M43, a close-by apparently spherical nebula ionized by a single star. We perform a combined, comprehensive study of the nebula and its ionizing star by using as many observational constraints as possible from a set of high-quality observations. We develop a quantitative spectroscopic analysis of the ionizing star, and the empirical analysis of the nebular images and spectroscopy. All the information obtained has been used to construct a photoionization model (see Morisset et al. in this conference). We show the importance of an adequate correction of scattered light coming from the Huygens region of M42 to accurately derive the nebular properties of M43. We determine total abundances of O, N and S directly from observable ions (no ICFs needed). The comparison of these abundances with those derived in M42 indicates the importance of the atomic data and the considered ICFs.
10. Henney, William J.: "Dynamics of the Orion Nebula" Show abstract
    I review what we know about the dynamics of photoionized regions in general and the Orion Nebula in particular. I will cover the fundamental physical processes that are important in setting ionized gas in motion: thermal pressure gradients, stellar winds, jets and other outflows, radiation pressure, magnetic fields, instabilities, turbulence. I will also describe results from recent numerical simulations and observations of the kinematics of the ionized gas in Orion. Some questions that I will address are: Why does Orion not look like a Strömgren sphere? What is the cause of all of the structure that we see? Does the stellar wind have any effect on the dynamics of the nebula? When is it OK to just ignore the dynamics?
11. Korytko, Roman: "Determination of energy distribution in ionizing radiation spectrum of the Orion Nebula" Show abstract
    The electron densities n_e and temperatures T_e as well as ionic abundances were determined using nebular gas diagnostic method DIAGN on the base of the observed spectra (Baldwin J. et al. ApJ. 1991) from 21 different slit positions on Orion Nebula. For the each observed part of the Orion Nebula the energy distribution in the ionizing spectrum beyond λ ≤  912 Å (so called Lyc-spectrum) was determined using NLEHII method. The resulting Lyc-spectra with other data were used to calculation of the optimized photoionization models for the observed parts of the Orion Nebula. The dust abundance was also taken into account. As a result, the new Lyc-spectra were obtained, that will be used for the models grid calculation, and for correct derivation of the new expressions for ionization-correction factors in high-metalicity HII regions.
12. Luridiana, Valentina: "Fluorescence in Orion" Show abstract
    In nebular astrophysics, it is customary to correct an observed spectrum for extinction by comparing a hydrogen line ratio, such as Ha/Hb, to the theoretical ratio expected under case B conditions. In a number of cases, however, this procedure yields unconsistent results when it is simultaneously applied to several line ratios. The impossibility to fit all the line ratios with a unique extinction coefficient implies that an extra mechanism is at work, pushing the line ratios away from those predicted by simple recombination theory. In this work, we discuss recent observational data for the Orion region in which this signature is observed and present models in which the deviant line ratios are explained in terms of fluorescent excitation from the stellar continuum.
13. Menten, Karl: "Star Formation in the Orion Molecular Cloud System and the BN/KL Region" Show abstract
    TBD
14. Mesa-Delgado, Adal: "Effects of Herbig-Haro objects and bars on the oxygen abundance in the Orion Nebula" Show abstract
    Making use of the Potsdam Multi-Aperture Spectrograph in the optical range 3500-7200 A, we present results of how the presence of certain morphological structures affects to the elemental oxygen abundance of the Orion Nebula. In particular, we present the analysis of two Herbig-Haro objects and two well-stratified bars: HH202, HH204, the Bright Bar and the Orion-South Bar. The spatial distribution maps of the O/H ratio are far of being homogeneous showing a variation of about 0.2 dex around the average value typically found in the Orion Nebula (8.50 dex). We conclude that the observed behavior is a product of two effects affecting the O+ abundances: a) an overestimation of the collisional de-excitation effects on the [OII] lines due to the use of a wrong density; and, specifically for the Herbig-Haro objects, b) the use of a high temperature at the area of the leading working surface of the gas flows.
15. Mikołajewska, Joanna
16. Morisset, Christophe: "Fluorescence in Orion" - Ch. Morisset, M. Nunez, C. Esteban, A. Mesa-Delgado, V. Luridiana Show abstract
    Observations of the Orion Nebula performed using PPAK facilities allow us to analyze more than 10,000 fibers of 2.6arcsec size, each one giving a spectrum with 2.6 AA spectral resolution. We will present first results on density determination using OII recombination lines and [FeIII] forbidden lines. The analysis is done using PyNeb package.
17. Núnez-Díaz, Manuel: "A very deep spectrophotometric mosaic of the Orion Nebula" - M. Núnez-Díaz, C. Esteban, A. Mesa-Delgado, W. Henney Show abstract
    We present a deep spectrophotometric mosaic of the Orion Nebula obtained with the Potsdam Multi-Aperture Spectrophotometer (PMAS) at Calar Alto Observatory. The aim of the observations is to determine the spatial distribution of physical conditions and chemical abundances across the nebula with a resolution of about 3 arcsec. The 64 arcsec long hexagonal fiber bundle (PPAK) has been used to obtain a complete mosaic of the central 4 arcmin of the nebula in about 15 fields (around 5000 individual spectra). The spectra of the mosaic cover the entire visual wavelength range from 3700 to 6750 Angstrom and allow us to derive: a) different line intensity ratios covering all possible ionization states in the nebula; b) electron densities from several diagnostics based on [S II], [O II], [Cl  III], [Ar IV] and [Fe III] line ratios; c) dust extinction distribution, e) electron temperatures from [O III], [N II] and [SII] line ratios; f) the distribution of ionic and total abundances determined from collisionally excited lines; g) ionic abundances from C II and O II recombination lines and the abundance discrepancy factor. We will give an overview of the the current status, preliminary results and future goals of the project.
18. O'Dell, Robert: "The Large Scale Structure of the Orion Nebula." Show abstract
    The bright Huygens Region has slowly yielded knowledge about its 3-D structure over the last several decades, with the advent of the "Blister Model", the escarpment nature of the Bright Bar, the presence of a foreground Veil, and finally the basic shape of the primary emitting layer. More recently we have come to understand the special nature of the Orion-S feature that is an isolated neutral cloud within the ionized gas and the home of numerous new stars and outflows. The most recent developments are in understanding of the Extended Orion Nebula projecting to the south from the Huygens Region. The fact that much of its optical radiation is actually scattered light from the Huygens Region has rendered the derivation of a 3-D model for this large region more difficult, but we can be confident of the basic results.
19. Olczak, Christoph: "The diverse effects of stellar interactions in the ONC" Show abstract
    The ONC is one of numerous building blocks of a new generation of stars and planets in our Galaxy. However, it's high density and population of massive stars favour strong and frequent stellar interactions that affect the formation and evolution of it's stellar and substellar members. I will show the huge variety of effects stellar encounters potentially have: they can prevent or trigger planet formation, affect the stellar multiplicity, and leave characteristic signatures that can be traced observationally. Moreover, I will demonstrate that encounters induce very rapid mass segregation in an ONC-like star cluster. The signature of mass segregation shows a complex evolution over time.
20. Otulakowska-Hypka, Magdalena
21. Peimbert, Antonio: "The implication of the Orion nebula abundances for other galactic and extragalactic H II regions" Show abstract
    TBD
22. Peimbert, Manuel: "On the derived t² values for the Orion nebula" Show abstract
    TBD
23. Petr-Gotzens, Monika: "The ONC and its binaries: more details than ever" Show abstract
    To investigate the role of binarity in disk evolution, and hence planet formation, in a clustered high stellar density environment, we carried-out spatially resolved adaptive-optics-assisted observations of 28 binaries in the ONC. A number of stellar parameters such as effective temperatures, spectral types, luminosities, and masses, as well as accretion properties and near-infrared excesses for the individual binary components have been determined. We find that the fraction of accretion disks among the binary sources, as traced by their Brackett???gamma (2.16mic) emission, is 40(+/-10)%. This frequency, as well as the mass accretion rates for individual binary components, are comparable to those of Orion single stars and binaries in other star forming regions - despite the overall significant truncation of the outer circumstellar disks around stars in the central ONC through photoevaporation. Furthermore, we see evidence for a synchronized evolution of circumprimary and circumsecondary disks in close binaries with separations <200 AU.
24. Różyczka, Michał: "Star and planet formation in Orion" Show abstract
    TBD
25. Rubin, Robert: "Spatial Analysis of the PAH and ionic features southeast of the Orion Bar" Show abstract
    PAH and dust emission features as well as atomic ionic lines were observed between 10-37 microns with the Spitzer Space Telescope Infrared Spectrograph at 11 positions southeast of the Bright Bar (BB) in Orion. This is a further study after the earlier paper that focused on the ionized emission lines in the outer extended Orion Nebula (Rubin, Simpson, O'Dell, et al. 2011, MNRAS, 410, 1320). The major findings will be presented, including the conclusion that PAH erosion and destruction are important from the BB out to about 5 arcmin. These observations suggest three different regimes are sampled: (1) the H II region - PDR interface directly southeast of the BB, (2) shielded molecular cloud material further out, and (3) the H II region - PDR interface seen limb brightened at the outermost veil position approximately 12 arcmin from the exciting star theta1 Ori C.
26. Sarna, Marek
27. Simón-Díaz, Sergio: "Chemical composition of OB type stars in Orion" Show abstract
    I will present the main results of a recent reinvestigation of the chemical composition of B-type stars in the Orion OB1 association by means of state-of-the-art stellar atmosphere codes, atomic models and techniques. I will show that the inhomogeneity of abundances previously found in B-type stars in the Ori OB1 association is a consequence of intrinsic errors induced by the use of photometric indices to establish the stellar parameters prior to the abundance analysis, and will compare the derived abundances with (a) recent determinations of the Solar chemical composition, (b) abundances in other B-type stars in the Solar vicinity, and (c) the nebular abundances derived from the emission line spectrum of the Orion nebula.
28. Smak, Józef
29. Sobolev, Andrey: "Methanol Maser Associated With the Binary System Giving Birth to Strong Molecular Outflow Ori-S6" Show abstract
    MERLIN observations have shown that the class II methanol maser in Orion South region originates in molecular ring around young binary system consisting of 2 intermediate mass stars. This is the first evidence of association of class II methanol maser with YSO of intermediate mass. Presence of the maser puts strong constraints on the physical conditions and parameters of associated molecular material. The binary system with which the maser is associated deserves special attention because it gives birth to highly collimated, extended and rotating bipolar outflow Ori-S6 located in the Orion South region.
30. Stasińska, Grażyna: "The early stages of Orion studies" Show abstract
    Starting from the earliest investigations of the Orion nebula, I will show how our understanding of this object has gradually changed until the picture we have now. I will allso recall how the its study lead to the introduction of several fundamental concepts still in use in nebular astrophysics.
31. Szczerba, Ryszard
32. Takahashi, Satoko: "Filament fragmentation and youngest star formation within the Orion molecular cloud" Show abstract
    We present high angular resolution and wide-field interferometric observations of the Orion Molecular Cloud-2/3 utilizing with the Submilllimeter Array and Expanded Very Large Array. We detected thermal dust emission from circumstellar envelopes of more than 60 sources. The estimated mass ranges from 0.07 to 5.8 Mo, and the detected sources have a variety of structures and evolutionary stages (from prestellar to Class 0/I phases). Hierarchical structures with periodicity on different size-scales are suggested from 37 pc down to 0.05 pc. This suggests multi-size scale fragmentation processes within the Orion A molecular cloud. Fragmentation spacings are roughly consistent with the thermal fragmentation length in large-scale clumps (>0.3 pc), while fragmentation spacing smaller than thermal fragmentation length are suggested from the SMA data. These results suggest that the multi-scale turbulent dissipation processes and the magnetic field may play important role in the evolution within the filament.
33. Teixeira, Paula Stella: "What does the fragmentation scale of the OMC1 filament tell us?" Show abstract
    We explore the role of Jeans Fragmentation in the origin of the core mass function, by analyzing the Orion Molecular Cloud (OMC) 1 northern molecular filament. We report Submillimeter Array (SMA) 1.3mm observations of the filament, where we identify 16 compact sources. The sources range in mass from 0.8 to 2.8 MSun and 3 of them are driving highly collimated CO molecular outflows. The millimeter emission may be arising from the circumstellar disk and inner part of the envelope; these compact sources are therefore in the Class 0/I evolutionary phase. The spatial analysis of the protostars shows that these are separated by a quasi-equidistant length of 30' (0.06pc), consistent with the Jeans length (for a temperature of 17K and a mean density of 1.9x105cm-3), i.e., thermal fragmentation. We compare this result to that of other filamentary clouds, and discuss how a core mass function may be assembled in these regions.
34. Tsamis, Yiannis: "The oxygen abundance in protoplanetary disks embedded in HII regions" Show abstract
    I will present results from our ongoing study of protoplanetary disks in the Orion Nebula and other HII regions placing emphasis on their chemical composition, including heavy element content. Proplyds embedded in HII regions present a fertile ground for the study of circumstellar matter (perhaps metal-enriched?), which is implicated in the formation of planetary systems. Using first and second generation integral field spectrographs on large telescopes such as the VLT, we have taken spatially-resolved spectra of the photoevaporated wind and jets arising from these landmark sources. Incidentally, these studies have implications for the long-standing 'abundance anomaly' problem which challenges our understanding of HII region spectra.
35. Paul van der Werf: "Orion's veil" Show abstract
    TBD
36. Zapata, Luis: "The BN-KL Star Formation Region" Show abstract
    I will present a brief review of the massive star forming region BN/KL giving a special attention to recent results using radio interferometric observations which revealed an surprisely event occurred here some 500 years ago.