Young stars accrete mass from circumstellar disks and in many cases, the accretion coincides with a phase of massive outflows, which can be highly collimated. Those jets emit predominantly in the optical and IR wavelength range. However, in several cases X-ray and UV observations reveal a weak but highly energetic component in those jets. X-rays are observed both from stationary regions close to the star and from knots in the jet several hundred AU from the star. In this article we show semi-analytically that a fast stellar wind which is recollimated by the pressure from a slower, more massive disk wind can have the right properties to power stationary X-ray emission. The size of the shocked regions is compatible with observational constraints. Our calculations support a wind-wind interaction scenario for the high energy emission near the base of YSO jets. For the specific case of DG Tau, a stellar wind with a mass loss rate of 5 ⋅ 10−10 M⊙ yr−1 and a wind speed of 800 km s−1 reproduces the observed X-ray spectrum. We conclude that a stellar wind recollimation shock is a viable scenario to power stationary X-ray emission close to the jet launching point.

It has recently been proposed (Goodman et al. 2014) that long, skinny, infrared dark clouds may trace out the densest features of the Milky Way, which include spiral arms, and possible inter-arm tendrils. The features are so long and skinny that they are almost certainly caused and maintained by a global gravitational potential, so they are not likely to be self-gravitating molecular clouds. These “Bones of the Milky Way” could be used to help piece together the structure of the Galaxy, shedding light on age-old questions, such as the number of spiral arms in our Galaxy and their locations. We have searched for and identified a handful of candidate Bones: long, filamentary infrared-dark clouds found in position-velocity space where our current model of the Galaxy predicts spiral arms should lie. Utilizing archival data, we have confirmed the location of these Bone candidates in the Galactic mid-plane and within 5 km/s of a spiral arm. We propose to use the IRAM 30-m to create the first ever high-resolution CO map (1mm) of a candidate “Bone of the Milky Way,” simultaneously with a suite of dense gas tracers at 3mm with IRAM. Capitalizing on IRAM’s unique ability to map CO over large areas at high angular resolution while simultaneously obtaining kinematic information about the dense gas, we will provide the first measure of structure and kinematics toward these unique Galactic structures. Our total time request is XX hours to map XX sq. arcminutes at 1mm (¹³CO and C¹⁸O 2-1) and 3mm (HCO+, HCN 1-0, etc.) toward our most promising Northern-hemisphere candidate Bone, “BC1.”

LabCraft is a community-driven mod for the popular video game Minecraft (published by Mojang). LabCraft is meant to be used as a teaching tool and to expose children to various biology-related disciplines. Feel free to contact any listed author if you’re interested in helping develop or deploy LabCraft. GitHub Source

Recently, argued that a very long, very thin infrared dark cloud “Nessie” lies directly in the Galactic midplane and runs along the Scutum-Centaurus arm in position-position-velocity (p-p-v) space as traced by lower density CO and higher density NH₃ gas. Nessie was presented as the first “bone” of the Milky Way, an extraordinarily long, thin, high contrast filament that can be used to map our galaxy’s ”skeleton.“ We present the first evidence of additional bones in the Milky Way Galaxy, arguing that Nessie is not a curiosity but one of several filaments that could potentially trace Galactic structure. Our ten bone candidates are all long, filamentary, mid-infrared extinction features which lie parallel to, and no more than twenty parsecs from, the physical Galactic midplane. We use CO, N₂H+, HCO+ and NH₃ radial velocity data to establish the location of the candidates in p-p-v space. Of the ten filaments, six candidates also have a projected aspect ratio of ≥50: 1, run along, or extremely close to, the Scutum-Centaurus arm in p-p-v space, and exhibit no abrupt shifts in velocity. Evidence suggests that these candidates are Nessie-like filaments which mark the location of significant spiral features, with ”filament 5" replicating Nessie’s properties most strongly. As molecular spectral-line and extinction maps cover more of the sky at increasing resolution and sensitivity, we seek to find more bones in future studies, ultimately to create a global-fit to the Galaxy’s spiral arms by piecing together individual skeletal features.

Recently, argued that the very long, very thin infrared dark cloud “Nessie” lies directly in the Galactic midplane and runs along the Scutum-Centaurus arm in position-position-velocity (_p-p-v_) space as traced by lower density CO and higher density NH₃ gas. Nessie was presented as the first “bone” of the Milky Way, an extraordinarily long, thin, high-contrast filament that can be used to map our Galaxy’s ”skeleton.“ Here, we present evidence for additional bones in the Milky Way Galaxy, arguing that Nessie is not a curiosity but one of several filaments that could potentially trace Galactic structure. Our ten bone candidates are all long, filamentary, mid-infrared extinction features which lie parallel to, and no more than twenty parsecs from, the physical Galactic mid-plane. We use CO, N₂H+, HCO+ and NH₃ radial velocity data to establish the three-dimensional location of the candidates in _p-p-v_ space. Of the ten candidates, six also: have a projected aspect ratio of ≥50: 1; run along, or extremely close to, the Scutum-Centaurus arm in _p-p-v_ space; _and_ exhibit no abrupt shifts in velocity. Evidence suggests that these candidates are marking the locations of significant spiral features, with the bone called filament 5 (”BC_18.88-0.09") being a close analog to Nessie in the Northern Sky. As molecular spectral-line and extinction maps cover more of the sky at increasing resolution and sensitivity, we seek to find more bones in future studies, ultimately to create a global-fit to the Galaxy’s spiral arms by piecing together individual skeletal features.

INTRODUCTION Analyses of star forming regions have helped to shape the standard cartoon of star formation. In this toy model, young stellar objects (YSOs) are first surrounded by envelopes of dust and gas. Observationally, the envelopes of these deeply embedded early protostars reprocess stellar photons and emit the vast majority of their luminosity in the far infrared. Next, the envelope either dissipates or falls onto a circumstellar accretion disk, out of which planets may or may not form. Observationally, this stage, known as the Classical T-Tauri (CTT) phase, corresponds to a spectroscopically visible photosphere veiled UV and IR excess continuum emission due respectively to accretion from disk to star, and by thermal emission from the disk itself. In the final stage, the disk disappears, either through accretion, evaporation, planet formation, or some combination of the three. Observationally, the photometry of an object in this stage, known as the Weak-line T-Tauri (WTT) phase, differs very little from a main sequence object, although its spectrum may still show spectroscopic indicators of youth. However, a correlation between the derived age and the observed evolutionary phase has not yet been strategically tested. Stellar clusters are thought to provide natural laboratories for defining the timescales of the stellar evolutionary phases, as they host a population of similarly aged stars. The age of an object (or group of objects) is determined by comparing the position on the Hertzsprung-Russel (HR) in relation isochronal model tracks. The best current method to estimate the age of stellar clusters is through these comparisons of the observed cluster properties to the HR diagram model tracks. With derived ages of samples of stellar clusters, the evolution of the cluster properties, such as disk fraction, accretion rate, rotation rates, etc., can be mapped as a function of time, which can then be further extrapolated to estimate the age for the evolutionary phases of single stars. Yet, any systematic errors which affect the placement of YSOs on the HR diagrams will bias derived studies of the evolution of cluster and stellar properties. For example, studies of cluster disk fractions as a function of cluster age have been used to estimate the lifetime of circumstellar disks , and hence the time available for planet formation. Once a star’s disk has has been depleted through evaporation and accretion, no material remains for planet-building. shows an exponential decay of cluster disk fractions as a function of cluster age and derives a mean disk lifetime of 3 Myr. However, while the mean behavior of disks seems to be explained by an exponential decay, for an individual star and disk, the variables which predict whether or not the disk will dissipate quickly remain unknown. There is perhaps no better example of the state of our ignorance about the longevity of a disk , and thus the ages corresponding to evolutionary phases, than than the case of TW Hydra. The star TW Hydra (TW Hya henceforth), which is the namesake of the TW Hya association, is the closest (NUMBER???) known CTT and one of the closest YSOs in general . As such, many researchers have taken the opportunity to observe TW Hya with a variety of instruments. Numerous diagnostics (photometry, millimeter interferometery, spectroscopy) of TW Hya suggest that it is still accreting material from a thick circumstellar disk . Despite an abundance of observations, the estimated ages are past what would be expected for the star to have such a substantial disk. Studies of the TW Hya association members estimate ages between 5-20 million years old for the TW Hya association . When TW Hya itself is typed using optical diagnostics, a K7 dwarf most often is the best match . This spectral type, as well as its photometry and HR diagram isochrones, suggest an age of ∼10 Myr for the star – again, quite an old age in terms of understanding the survival of TW Hya’s accretion disk. However, one study of TW Hya in the infrared has suggested that these characteristics could be different. used moderate resolution near-IR spectra to determine a significantly later spectral type of M3. This revised spectral type suggests that TW Hya is younger (6 Myr ???). Adopting the spectral type of , and younger age, is rather appealing in terms of explaining the presence of the disk, yet at the same time requires a better understanding of spectral typing of YSOs. The mismatch between the optical and infrared spectral types is an especially pernicious problem for longitudinal studies of star formation. For field objects, which are typically no longer associated with star-forming material, the infrared spectral types correlate well with optically determined spectral types . For YSOs, the spectral type suggested by an optical spectrum (when available, as optical observations are often not feasible due to a combination of foreground extinction and accretion-shock veiling) does not always agree with the type suggested by the infrared spectrum . Possible reasons that may explain the observed discrepancies may result from a magnetic field, including Zeeman broadening and stellar activity, among other processes. An important piece of this puzzle is the strength of the stellar magnetic field. The magnitude of Zeeman broadening, an effect due to Zeeman line splitting in magnetic fields, increases with increasing wavelength as λ², meaning that optical spectra are less affected by strong magnetic fields than infrared spectra. Thus, any spectral typing using infrared data with spectral lines that are magnetically sensitive will produce a different result when a (strong) magnetic field is present. Strong magnetic fields are also associated with increased stellar activity and star spots. The temperature contrast between the stellar photosphere and the star spot are more severe in optical spectra. In the infrared, the contrast between the star and spot is less pronounced, thus resulting in the derivation of a different effective temperature (and spectral type) than that from optical data. Moreover, the competing effects of Zeeman broadening and stellar activity on the spectral types suggested by infrared spectra increases the uncertainty by which one can claim to know the spectral type (and hence age/mass derived from theoretical models) of these young stars. For TW Hya, suggest the reason for the discrepancy between the optical and infrared derived spectral types is likely due to star spots. Unfortunately this explanation is quite complicated, as the subject of star spots is related to a controversy regarding a possible planet, as well as magnetic field. Radial velocity monitoring of the star TW Hya, which is nearly pole-on , suggests that there may be a planetary companion. Subsequent analysis of the RV signal has been used to rebutte this claim and instead suggests that stellar spots are responsible for any observed RV modulations . — Regardless of the potential existence of a planetary companion, the strength of TW Hya’s magnetic field is not discussed in comparing the TW Hya spectral types, and as discussed above, will also have an impact. — to be written — In this paper, we aim to reveal the role of the magnetic field and reconcile the debated spectral type of TW Hya. We re-evaluate the stellar parameters of TW Hya using a powerful combination of newly obtained infrared spectra over the entire H and K-bands with high spectral resolution needed to observationally discern the magnetic effects and a spectral synthesis code that is capable of making the inclusion of magnetic fields widely possible. We use MoogStokes, a custom driver for the MOOG spectral synthesis code which computes the emergent spectrum of a magnetic star . MoogStokes calculates the Zeeman splitting of an absorption line by using the spectroscopic terms of the upper and lower state to determine the number, wavelength shift, and polarization of components into which it will split for a given magnetic field strength. MoogStokes then computes the polarized radiative transfer of all four Stokes components (I, Q, U, and V) from the bottom of the photosphere to the top. The emergent spectrum is a function of viewing angle as well as orientation of the magnetic field. In order to synthesize the composite spectrum of an unresolved magnetic star, MoogStokes computes emergent spectra at various locations across the stellar disk, applies the effects of rotational broadening and limb darkening, and combines the different emergent spectra to compute the composite spectrum. We present new high signal-to-noise spectra of TW Hya obtained with the Immersion GRating INfrared Spectrometer (IGRINS) instrument that boasts both high resolution ($R={\delta\lambda} = 45000$) and large spectral grasp . IGRINS provides comparable resolving power of CRIRES (a well known high resolution infrared spectrograph at Keck Observatory) at 30 times the wavelength range with no gaps in coverage , allowing the study of orders of magnitudes more spectral lines than was feasible with the previous generation of high resolution infrared spectrographs. Armed with both IGRINS and MoogStokes, we demonstrate that we can use a multitude of spectral lines from infrared spectra to determine the fundamental parameters of stars, which is a promising tactic to wield against clusters of stars in the future. By improving estimates of effective temperatures, surface gravities, rotational speeds, magnetic fields, and infrared continuum excess, this combination of tools promises to be a powerful way to investigate the evolution of these parameters, and the stars themselves, as a function of age.

LABELPLACEHOLDER1ID INTRODUCTION LABELPLACEHOLDER2ID EXPERIMENT Beam DAQ Polarized Target BETA BigCal Gas Lucite Tracker LABELPLACEHOLDER11ID DATA ANALYSIS Bigcal calibration Cerenkov Electron Identification Tracking Binning LABELPLACEHOLDER16ID EXTRACTION OF ASYMMETRY Charge Normalization Live time correction Beam Polarization Target Polarization Packing Fraction Target Dilution Factor Measured Asymmetries LABELPLACEHOLDER24ID RADIATIVE AND BACKGROUND CORRECTIONS Radiative Elastic tail subtraction Pair-symmetric background subtraction Pion asymmetry Inelastic radiative corrections LABELPLACEHOLDER30ID SPIN ASYMMETRIES Systematic errors LABELPLACEHOLDER32ID SPIN STRUCTURE FUNCTIONS LABELPLACEHOLDER33ID CONCLUSION

BASIC IDEAS 1. What are fields? (diff between theory of field and theory of particles) 2. Why quantum field theory? 1. Desire (photon and phonon) 2. Marriage of QM and R. (# of part. can change) 3. Fields maybe more fundemantal. 4. Connection between QFT and classical thermal field theory at T > 0. 3. How to quantize? discretize, solve N-body, take limit. 4. Xi(t)⇔ϕ(X, t)

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IntroductionRecently, Lynch and Houghton (2015) developed a method to predict in vivo response of auditory neurons using an estimated spectrotemporal receptive field (STRF) filter combined with an integrate-and-fire neuron model based on the Izhikevich neuron (Izhikevich, 2003). This model adds an additional adaptive parameter to the integrate-and-fire neuron for enhanced biophysical realism. Optimization is performed iteratively on the parameters of the filter and the parameters of the neuron model using a genetic algorithm in which fitness is evaluated by the van Rossum distance metric (van Rossum, 2001).Lynch and Houghton’s method fills a clear need in the neuroinformatics field and moves forward the possibilities for neuron modeling in in vivo electrophysiology research. There exist many avenues for further improvement, including models with more biologically interpretable parameters and improved optimization algorithms.In this paper, we propose a dynamical systems-based neuron model combined with an STRF filter that provides superior prediction accuracy with a computationally efficient optimization algorithm. This method is based on a Hindmarsh-Rose (HR) neuron model (Hindmarsh & Rose, 1984), which strikes a balance between the limited parameter sets of the integrate-and-fire models and the biological realism of the Hodgkin-Huxley ion current models (Hodgkin & Huxley, 1952). The feature space is explored by emcee (Foreman-Mackey et al., 2013), a Python implementation of a Markov chain Monte Carlo (MCMC), to find a local optima using the computationally efficient SPIKY  synchronization metric (Kreuz et al., 2015) as the fitness function. This combination of algorithms is first tested on simulated data with known parameters, and then validated on a real data set recorded in vivo from auditory neurons in the zebra finch (Taeniopygia guttata).