The Orion Fingers: Near-IR Adaptive Optics Imaging of an Explosive Protostellar Outflow

Aims. Adaptive optics images are used to test the hypothesis that the explosive BN/KL outflow from the Orion OMC1 cloud core was powered by the dynamical decay of a non-hierarchical system of massive stars. Methods. Narrow-band H2, [Fe II], and broad-band Ks obtained with the Gemini South multi-conjugate adaptive optics (AO) system GeMS and near-infrared imager GSAOI are presented. The images reach resolutions of 0.08 to 0.10", close to the 0.07" diffraction limit of the 8-meter telescope at 2.12 microns. Comparison with previous AO-assisted observations of sub-fields and other ground-based observations enable measurements of proper motions and the investigation of morphological changes in H2 and [Fe II] features with unprecedented precision. The images are compared with numerical simulations of compact, high-density clumps moving ~1000 times their own diameter through a lower density medium at Mach 1000. Results. Several sub-arcsecond H2 features and many [Fe II] 'fingertips' on the projected outskirts of the flow show proper motions of ~300 km/s. High-velocity, sub-arcsecond H2 knots ('bullets') are seen as far as 140" from their suspected ejection site. If these knots propagated through the dense Orion A cloud, their survival sets a lower bound on their densities of order 10^7 cm^-3, consistent with an origin within a few au of a massive star and accelerated by a final multi-body dynamic encounter that ejected the BN object and radio source I from OMC1 about 500 years ago. Conclusions. Over 120 high-velocity bow-shocks propagating in nearly all directions from the OMC1 cloud core provide evidence for an explosive origin for the BN/KL outflow triggered by the dynamic decay of a non-hierarchical system of massive stars. Such events may be linked to the origin of runaway, massive stars.Comment: Accepted to A&A. 25 pages, 18 figures. Figure 1 (http://goo.gl/whAz3m) is particularly colorful. The FITS images will be made available from CDS. Resubmission fixed broken bibliograph

Disentangling Stellar and Airglow Emission Lines from HST-COS Spectra

H I Ly$\alpha$ (1215.67 \r{A}) and the O I triplet (1302.17, 1304.86, and 1306.03 \r{A}) are bright far-ultraviolet (FUV) emission lines that trace the stellar chromosphere. Observations of stellar Ly$\alpha$ and O I using the Hubble Space Telescope's (HST) most sensitive FUV spectrograph, the Cosmic Origins Spectrograph (COS), are contaminated with geocoronal emission, or airglow. This study demonstrates that airglow emission profiles as observed by COS are sufficiently stable to create airglow templates which can be reliably subtracted from the data, recovering the underlying stellar flux. We developed a graphical user interface to implement the airglow subtraction on a sample of 171 main sequence F, G, K, and M-type dwarfs from the COS data archive. Correlations between recovered stellar emission and measures of stellar activity were investigated. Several power law relationships are presented for predicting the stellar Ly$\alpha$ and O I emission. The apparent brightness of the stellar emission relative to the airglow is a critical factor in the success or failure of an airglow subtraction. We developed a predictor for the success of an airglow subtraction using the signal-to-noise ratio (SNR) of the nearby chromospheric emission line Si III (1206.51 \r{A}). The minimum attenuated Ly$\alpha$ flux which was successfully recovered is 1.39$\times$10$^{-14}$ erg cm$^{-2}$ s$^{-1}$, and we recommend this as a minimum flux for COS Ly$\alpha$ recoveries.Comment: 38 pages, 27 figures, to be published in Ap

Stellar Characterization Necessary to Define Holistic Planetary Habitability

It is a truism within the exoplanet field that to know the planet, you must know the star. This pertains to the physical properties of the star (i.e. mass, radius, luminosity, age, multiplicity), the activity and magnetic fields, as well as the stellar elemental abundances which can be used as a proxy for planetary composition. In this white paper, we discuss important stellar characteristics that require attention in upcoming ground- and space-based missions, such that their processes can be understood and either detangled from that of the planet, correlated with the presence of a planet, or utilized in lieu of direct planetary observations

The Orion Fingers: H_2 Temperatures and Excitation in an Explosive Outflow

We measure H_2 temperatures and column densities across the Orion Becklin-Neugebauer/Kleinmann-Low (BN/KL) explosive outflow from a set of 13 near-infrared (IR) H_2 rovibrational emission lines observed with the TripleSpec spectrograph on Apache Point Observatory's 3.5 m telescope. We find that most of the region is well characterized by a single temperature (~2000–2500 K), which may be influenced by the limited range of upper-energy levels (6000–20,000 K) probed by our data set. The H_2 column density maps indicate that warm H2 comprises 10^(-5)–10^(−3) of the total H_2 column density near the center of the outflow. Combining column density measurements for co-spatial H_2 and CO at T = 2500 K, we measure a CO/H2 fractional abundance of 2 × 10^(−3) and discuss possible reasons why this value is in excess of the canonical 10^(−4) value, including dust attenuation, incorrect assumptions on co-spatiality of the H_2 and CO emission, and chemical processing in an extreme environment. We model the radiative transfer of H_2 in this region with ultraviolet (UV) pumping models to look for signatures of H_2 fluorescence from H i Lyα pumping. Dissociative (J-type) shocks and nebular emission from the foreground Orion H ii region are considered as possible Lyα sources. From our radiative transfer models, we predict that signatures of Lyα pumping should be detectable in near-IR line ratios given a sufficiently strong source, but such a source is not present in the BN/KL outflow. The data are consistent with shocks as the H_2 heating source

CHESS: An innovative concept for high-resolution, far-UV spectroscopy

The space ultraviolet (UV) is a critical astronomical observing window, where a multitude of atomic, ionic, and molecular signatures provide crucial insight into planetary, interstellar, stellar, intergalactic, and extragalactic objects. The next generation of large space telescopes require highly sensitive, moderate-to-high resolution UV spectrograph. However, sensitive observations in the UV are difficult, as UV optical performance and imaging efficiencies have lagged behind counterparts in the visible and infrared regimes. This has historically resulted in simple, low-bounce instruments to increase sensitivity. In this study, we present the design, fabrication, and calibration of a simple, high resolution, high throughput FUV spectrograph - the Colorado High-resolution Echelle Stellar Spectrograph (CHESS). CHESS is a sounding rocket payload to demonstrate the instrument design for the next-generation UV space telescopes. We present tests and results on the performance of several state-of-the-art diffraction grating and detector technologies for FUV astronomical applications that were flown aboard the first two iterations of CHESS. The CHESS spectrograph was used to study the atomic-to-molecular transitions within translucent cloud regions in the interstellar medium (ISM) through absorption spectroscopy. The first two flights looked at the sightlines towards α Virgo an