Star Formation from Spitzer (Lyman) to Spitzer (Space Telescope) and Beyond

A summary of JENAM 2008 Symposium 9 "Star Formation from Spitzer (Lyman) to Spitzer (Space Telescope) and Beyond", held in Vienna, 10-12 September 2008.Comment: 6 page

Estimating Extinction using Unsupervised Machine Learning

Dust extinction is the most robust tracer of the gas distribution in the interstellar medium, but measuring extinction is limited by the systematic uncertainties involved in estimating the intrinsic colors to background stars. In this paper we present a new technique, PNICER, that estimates intrinsic colors and extinction for individual stars using unsupervised machine learning algorithms. This new method aims to be free from any priors with respect to the column density and intrinsic color distribution. It is applicable to any combination of parameters and works in arbitrary numbers of dimensions. Furthermore, it is not restricted to color space. Extinction towards single sources is determined by fitting Gaussian Mixture Models along the extinction vector to (extinction-free) control field observations. In this way it becomes possible to describe the extinction for observed sources with probability densities. PNICER effectively eliminates known biases found in similar methods and outperforms them in cases of deep observational data where the number of background galaxies is significant, or when a large number of parameters is used to break degeneracies in the intrinsic color distributions. This new method remains computationally competitive, making it possible to correctly de-redden millions of sources within a matter of seconds. With the ever-increasing number of large-scale high-sensitivity imaging surveys, PNICER offers a fast and reliable way to efficiently calculate extinction for arbitrary parameter combinations without prior information on source characteristics. PNICER also offers access to the well-established NICER technique in a simple unified interface and is capable of building extinction maps including the NICEST correction for cloud substructure. PNICER is offered to the community as an open-source software solution and is entirely written in Python.Comment: Accepted for publication in A&A, source code available at http://smeingast.github.io/PNICER

A new method to unveil embedded stellar clusters

In this paper we present a novel method to identify and characterize stellar clusters deeply embedded in a dark molecular cloud. The method is based on measuring stellar surface density in wide-field infrared images using star counting techniques. It takes advantage of the differing $H$-band luminosity functions (HLFs) of field stars and young stellar populations and is able to statistically associate each star in an image as a member of either the background stellar population or a young stellar population projected on or near the cloud. Moreover, the technique corrects for the effects of differential extinction toward each individual star. We have tested this method against simulations as well as observations. In particular, we have applied the method to 2MASS point sources observed in the Orion A and B complexes, and the results obtained compare very well with those obtained from deep Spitzer and Chandra observations where presence of infrared excess or X-ray emission directly determines membership status for every star. Additionally, our method also identifies unobscured clusters and a low resolution version of the Orion stellar surface density map shows clearly the relatively unobscured and diffuse OB 1a and 1b sub-groups and provides useful insights on their spatial distribution.Comment: A&A, in press; 13 pages, multi-layer figures can be displayed with Adobe Acrobat Reade

Symmetry Constrained Two Higgs Doublet Models

We study Two-Higgs-Doublet Models (2HDM) where Abelian symmetries have been introduced, leading to a drastic reduction in the number of free parameters in the 2HDM. Our analysis is inspired in BGL models, where, as the result of a symmetry of the Lagrangian, there are tree-level scalar mediated Flavour-Changing-Neutral-Currents, with the flavour structure depending only on the CKM matrix. A systematic analysis is done on the various possible schemes, which are classified in different classes, depending on the way the extra symmetries constrain the matrices of couplings defining the flavour structure of the scalar mediated neutral currents. All the resulting flavour textures of the Yukawa couplings are stable under renormalisation since they result from symmetries imposed at the Lagrangian level. We also present a brief phenomenological analysis of the most salient features of each class of symmetry constrained 2HDM.Comment: 30 pages, 5 Table

ECONOMIC TRADEOFF ANALYSIS OF A PRODUCT LINE ARCHITECTURE APPROACH THROUGH MODEL-BASED SYSTEMS ENGINEERING: A CASE STUDY OF FUTURE MINE COUNTERMEASURES UNMANNED UNDERWATER VEHICLES

The defense sector often develops systems to operate for at least 15 years, which can reach 40 or even 50 years. Those systems tend to be cheaper, more rapidly developed, and reliable when developed on product lines (PL). Product line architecture surges with potential to improve the acquisition process, resulting in a more rapid insertion of cost-effective warfighting capabilities. This thesis investigates the impact of the PL approach by analyzing the future generation of mine countermeasure (MCM) unmanned underwater vehicle (UUV) architecture alternatives, employing a detailed reuse model based on the COPLIMO framework. The research integrates parametric cost modeling with model-based systems engineering (MBSE), feeding the existing baseline knowledge regarding PL architecture. Furthermore, this can improve systems acquisition processes, deliver more agile capability, and reduce total life cycle costs (LCC). The integration of models highlights significant differences among the architectural variations considered early in the acquisition process before substantial financial commitments. Early decisions determine most of the total LCC and establish a baseline for long-term system performance. Hence, the choice of favorable design alternatives is crucial to program success. The results demonstrate that up-front investments in product lines generate a significant return on investment (ROI).Capitao-Tenente, Brazilian NavyApproved for public release. Distribution is unlimited

Mapping the interstellar dust with near-infrared observations: An optimized multi-band technique

We generalize the technique of Lada et al. (1994) to map dust column density through a molecular cloud (NICE) to an optimized multi-band technique (NICER) that can be applied to any multi-band survey of molecular clouds. We present a first application to a ~625 deg^2 subset of the Two Micron All Sky Survey (2MASS) data and show that when compared to NICE, the optimized NICER technique (i) achieves the same extinction peak values, (ii) improves the noise variance of the map by a factor of 2 and (iii) is able to reach 3 \sigma dust extinction measurements as low as A_V = 0.5 magnitudes, better than or equivalent to classical optical star count techniques and below the threshold column density for the formation of CO, the brightest H2 tracer in radio-spectroscopy techniques. The application of the NICER techniques to near-infrared data obtained with a 8 meter-class telescope with a state-of-the-art NIR camera, such as the VLT-ISAAC combination, will be able to achieve dynamic ranges from below 10^21 protons cm^-2 to over 10^23 protons cm^-2 (A_V in the range [0.3, 60]) and spatial resolutions < 10'', making use of a single and straightforward column density tracer, extinction by interstellar dust.Comment: 12 pages, 8 figures; A&A, in press. Full document with figures available at http://www.astro.uni-bonn.de/~lombardi/ms1526.pd

Schmidt's Conjecture and Star Formation in Molecular Clouds

We investigate Schmidt's conjecture (i.e., that the star formation rate scales in a power-law fashion with the gas density) for four well-studied local molecular clouds (GMCs). Using the Bayesian methodology we show that a local Schmidt scaling relation of the form Sigma*(A_K) = kappa x (A_K)^{beta} (protostars pc^{-2}) exists within (but not between) GMCs. Further we find that the Schmidt scaling law, by itself, does not provide an adequate description of star formation activity in GMCs. Because the total number of protostars produced by a cloud is given by the product of Sigma*(A_K) and S'(> A_K), the differential surface area distribution function, integrated over the entire cloud, the cloud's structure plays a fundamental role in setting the level of its star formation activity. For clouds with similar functional forms of Sigma*(A_K), observed differences in their total SFRs are primarily due to the differences in S'(> A_K) between the clouds. The coupling of Sigma*(A_K) with the measured S'(> A_K) in these clouds also produces a steep jump in the SFR and protostellar production above A_K ~ 0.8 magnitudes. Finally, we show that there is no global Schmidt law that relates the star formation rate and gas mass surface densities between GMCs. Consequently, the observed Kennicutt-Schmidt scaling relation for disk galaxies is likely an artifact of unresolved measurements of GMCs and not a result of any underlying physical law of star formation characterizing the molecular gas.Comment: 34 pages, 8 figures, and 2 tables; accepted for publication in ApJ on Sept 23, 201

Controlled Flavour Changing Neutral Couplings in Two Higgs Doublet Models

We propose a class of Two Higgs Doublet Models where there are Flavour Changing Neutral Currents (FCNC) at tree level, but under control due to the introduction of a discrete symmetry in the full Lagrangian. It is shown that in this class of models, one can have simultaneously FCNC in the up and down sectors, in contrast to the situation encountered in BGL models. The intensity of FCNC is analysed and it is shown that in this class of models one can respect all the strong constraints from experiment without unnatural fine-tuning. It is pointed out that the additional sources of flavour and CP violation are such that they can enhance significantly the generation of the Baryon Asymmetry of the Universe, with respect to the Standard Model.Comment: 29 pages, 3 figure

X Marks the Spot: Nexus of Filaments, Cores, and Outflows in a Young Star-Forming Region

We present a multiwavelength investigation of a region of a nearby giant molecular cloud that is distinguished by a minimal level of star formation activity. With our new 12CO(J=2-1) and 13CO(J=2-1) observations of a remote region within the middle of the California molecular cloud, we aim to investigate the relationship between filaments, cores, and a molecular outflow in a relatively pristine environment. An extinction map of the region from Herschel Space Observatory observations reveals the presence of two 2-pc-long filaments radiating from a high-extinction clump. Using the 13CO observations, we show that the filaments have coherent velocity gradients and that their mass-per-unit-lengths may exceed the critical value above which filaments are gravitationally unstable. The region exhibits structure with eight cores, at least one of which is a starless, prestellar core. We identify a low-velocity, low-mass molecular outflow that may be driven by a flat spectrum protostar. The outflow does not appear to be responsible for driving the turbulence in the core with which it is associated, nor does it provide significant support against gravitational collapse.Comment: Accepted for publication in the Astrophysical Journa